VETS20019 Study.pdf

VETS20019 Frontiers in Veterinary Science Definitions and concepts Environmental factors 1 Thermoregulation Thermoregulation refers to the physiological and behavioural processes by which an animal attempts to maintain a stable internal body temperature by regulating heat gain and heat loss Poikil...

VETS20019 Frontiers in Veterinary Science Definitions and concepts Environmental factors 1 Thermoregulation Thermoregulation refers to the physiological and behavioural processes by which an animal attempts to maintain a stable internal body temperature by regulating heat gain and heat loss Poikilotherms are organisms whose core temperature varies considerably with the environmental temperature, meaning temperature regulation is primarily through behavioural means (low energy requirement so better survival in food scarcity). Homeotherms are animals able to maintain a relatively stable internal core temperature range by internal means within a wide range of environmental/ambient temperatures (high metabolic rate = high energy intake). Internal means include: 1. Shivering: Rapid rhythmic skeletal muscle contractions that liberate energy to be converted into heat. Increases metabolic heat production 2. Non-shivering thermogenesis: Hormones regulate heat production by the stimulation of fat metabolism. Brown fat is capable of converting energy into heat (abundant in small animals and very young animals to compensate for greater heat loss caused by greater surface area to volume ratio) 3. Piloerection: Fur stands up and traps heat close to the skin 4. Skin vasoconstriction: Autonomic response in which skin blood vessels reduce blood flow through the skin. This decreases heat loss by keeping blood in the central core where it is insulated from the external temperature. Skin temperature is reduced. The reverse is true for skin vasodilation Elevated body temperature Hyperthermia Pyrexia - Elevated temperature with normal - Increased thermoregulatory ‘set point’ thermoregulatory ‘set point’ - Often associated with infectious disease - Response to hyperthermia is decrease heat - Adaptive response production and increase heat loss Reduced body temperature  Hypothermia Physiological (uncommon) - Low temperature with normal - Decreased thermoregulatory ‘set point’ thermoregulatory ‘set point’ - Occurs prior to giving birth in some species - Response is to increase heat production - Occurs during hibernation in some species and decrease heat loss The thermoneutral zone is the range of ambient temperatures at which temperature regulation is achieved without regulatory changes in heat production or evaporative cooling, i.e. the conditions under which an animal does not need to make any significant physiological or behavioural adjustments to try and lose or conserve heat. Active compensatory mechanisms are employed above the upper critical temperature and below the lower critical temperature, however death will not necessarily occur outside the thermoneutral zone without extreme temperatures or prolonged time in these critical conditions without compensation. Body size and shape are important. Smaller, thinner animals have an increased surface area to volume ratio and lose heat more readily, and larger, fatter animals have a decreased surface area to volume and gain heat more rapidly. Heat stress clinical signs include increased water intake, decreased appetite, decreased fertility, decreased weight gain, decreased milk production, reduced exercise performance, illness (heat stroke) and death. Cold stress clinical signs include increased metabolic weight (=weight loss), increased feed intake, decreased FCE, altered body composition, reduced neonatal survival, and death from hypothermia. 2 Air, soil and water quality The quality of air can have significant effects on an animal’s respiration and health in general: 1. Bioaerosols: Airborne particles that contain living organisms, fragments, toxins, and waste products. Possible health effects include exposure to infectious diseases, allergic reactions, respiratory symptoms and lung function impairment 2. Noxious gases: Includes ammonia (toxic), hydrogen sulfide (toxic), carbon dioxide and methane - Ammonia (from urine and faeces): Occurs when anhydrous ammonia (liquid or gas) reacts with tissue water to form a strongly alkaline solution (NH4OH). Results in the destruction of cilia and the mucosal barrier to infection (more susceptible to respiratory disease). Damaged cells and inflammatory exudate as well as reactive smooth muscle contraction cause airway obstruction - Hydrogen sulfide (from faeces): Highly toxic (affects CNS). At high concentrations, hydrogen sulfide has a direct paralysing effect on the respiratory centre in the brain, causing respiratory paralysis after a couple of breaths followed by convulsions and death. It becomes dangerous at 100 ppm and above as it causes loss of smell and is undetectable to the senses 3. Particular matter: Potential for particles to cause health effects is related to their size, with fine particles with a diameter beef cattle, horses and pigs > dairy cows and poultry. Drinking water of excess salinity causes reluctance to drink, diarrhoea, loss of production and decline in health 2. Presence of infectious organisms 3. Toxins 4. Mineral deficiencies/excesses 5. Dissolved oxygen concentration 6. Organic matter build-up 7. Ammonia concentrations 8. Water temperature 9. pH Stocking density affects many of these factors. Environmental effects and degradation include: 1. Climate change: Suitable habitats for both domestic and wild animals may become unsuitable or shift geographically. Effects can be mitigated in domestic but not wild animals. Effects may be direct on animals themselves or via changing local plant species affecting the food chain, ex. Ocean pH change and shell integrity, temperature effects on sex determination/ratio 2. Deforestation and loss of habitat 3. Pollution/rubbish 4. Human interaction - dependency (inappropriate diets), conflicts (predators, grazing wildlife, motor vehicle trauma and death), disease exchange (new zoonoses). Once a disease becomes established in humans following a spillover event, it generally means human to human spread is possible Welfare The increase in societal concern for animal welfare over history is interlinked with the circle of influence/concern. Animal welfare is a more mainstream concept as more societies developed food and economic security and their capacity to expand their circle of concern and advocate for animal health grew exponentially. Timeline: 500 BCE: Ancient philosophers advocated not eating animals 400 BCE: Religious edicts forbidding the consumption or mistreatment of certain animals Early 20th century: Prevention of Cruelty legislation Late 20th century: Concept of ‘duty of care,’ a need to provide animals with the necessities of life, nourishment, basic health care and treatment if they fall ill. Not just the prevention of cruelty but the active care of animals Now: Change driven by public behaviour rather than legislation and more animals considered worthy of protection Animal welfare: The concern for an animal’s wellbeing, associated with the concept that animals should be humanely treated and not unnecessarily suffer. Accepting of some animal utilisation by humans but positions on the details vary significantly Animal rights: A philosophical position that animals have inherent moral rights. Animal utilisation by humans contravenes animal rights as animals should have a right to consent. 3 Welfare of farmed animals Development of more intensive farming methods (mechanisation, increased efficiency, genetic selection, targeted nutrition) led Carson to write Animal Machines in which she exposed new developments in agriculture to the public with reasonable concern for animal welfare. The government responded with the original five freedoms: animals should have the space to turn around, groom themselves, get up, lie down, and stretch their limbs. This was developed into the modern five freedoms: 1. Freedom from hunger or thirst 2. Freedom from discomfort 3. Freedom from pain, injury or disease 4. Freedom to express most normal behaviour 5. Freedom from fear and distress However absolute freedom in this sense is oftentimes not viable, so the more continuous five domains of animal welfare were developed: Each domain can be positive or negative, and the mental state mainly has to do with negative and positive experiences as a result of the other four domains. Welfare is captured throughout time - as long as there are more positive experiences than negative (sleep is unconscious = neutral), the animal has reasonably good welfare. Welfare issues that have an impact on farming animals include: 1. Confinement of animals: May be real and/or exist in the public perception. Majorly concerns freedom of movement and access to sufficient resources to meet their behavioural and social needs 2. Surgical husbandry practices that cause pain: Mulesing, castration, dehorning, tail docking, beak trimming  3. Long distance transport of animals for economic reasons: Road/rail/sea/air. Higher price obtained by transporting animals long distance (live export rather than transporting meat) 4. Problems and diseases induced by the population environment: Ex. Mastitis in dairy cows from bacterial contamination due to poor housing hygiene 5. Poor handling during transport or slaughter: Not a byproduct of the system, but rather an active act of malpractice Continuous improvement involves regulation and product assurance methods to incentivise adhering to standards for animal welfare. Farmers will generally earn greater profit for their products for following animal welfare regulations. New technologies to improve welfare include immunocastration and ‘in ovo’ sex identification in layer poultry 4 Welfare of sport and entertainment animals Includes animals exhibited at fauna parks, aquariums and agricultural shows, those performing in circuses, taking part in sporting events such as racing and rodeos, or in the film and television industry. Horse racing is a 5 billion dollar industry, but has various welfare concerns including: 1. Treatment of lower-value breeding mares 2. ‘Wastage’ of young stock before ever racing: 82% of horses entered training, and 34% of those that were not trained died from fractures, wounds/trauma, digestive disorders and tendon/ligament injuries (most were euthanized) 3. 2-year-old racing (damage/developmental issues) 4. Quality of life for racehorses outside of training and racing 5. Catastrophic injury and death: Occur at a rate of 0.4 in 1000 starts, but may also occur during training, risking catastrophic fractures of the limb bones and supporting structures requiring euthanasia. Many such injuries are caused by a leg bone fracturing while at gallop. These are thought to occur through weakening of the bone due to microfractures - minute cracks that develop with repeated loading and are invisible unless the bone is examined with a microscope/high quality bone scan 6. Treatment and fate of horses once they leave the industry: Most horses retire by 5 years old. Many females will become ‘brood mares’ and remain in the industry. However, because most male racehorses are castrated, they have no role in the breeding industry. A video leaked in 2019 showing the abuse and mistreatment of ex-racehorses prior to slaughter at a pet food abattoir. The NSW racing industry claimed it does not send any of its horses to pet food abattoirs, but if there is no outlet for these horse in the pet food industry, there needs to be another way of humanely managing these horses in retirement (risk of neglect without systematic protocol) Greyhound racing is a smaller industry (4 billion) with its own suite of welfare concerns:  1. Illegal training of greyhounds to chase by using live prey (misconception that it will make them perform better with little basis) 2. Fate of animals that do not go through greyhound adoption programs 3. 16000-25000 greyhounds unaccounted for (wastage) Greyhound Risk Victoria Animal Welfare Program (combat risk of the industry being completely banned): - Rehoming: Greyhound Adoption Program and working with other rehoming organisations - Education, training and advice for industry participants - ‘Whole of Life’ welfare strategy - Greyhound Microchip Registry - Research: Data analysis on injury rates and other aspects - Veterinary support on and off the track 5 Welfare of animal companions Attitudes towards animals are shaped by community standards and expectations, personal experience, attitudes of those around us and professional opinions shared with us. Values (guiding life principles) inform beliefs (values + information) inform attitudes (positive or negative response to focus) inform intentions inform behaviours (influenced by social norms and perceived behavioural control). Regulation happens at many levels: personal choices, local council rules, state legislation, National/Federal Acts, etc. Attitudes towards animals and their welfare are modified by two key motivational considerations: Affect (emotional response) and Utility (perceived instrumental value) Animal sentience refers to the ability of animals to experience pleasurable states such as joy and aversive states such as pain or fear. For companion animals, many of the decisions that determine their daily environment, activities, health and interactions are determined by people. Animal welfare refers to an animal’s ability to cope with its environment, the behaviours and feelings expressed by animals (difficult to measure), and whether the various needs and wants of the animals are being fulfilled. One Health recognises that the physical health of humans, animals, plants and the environment is interconnected. One Welfare extends this to include physical and mental wellbeing, in that animal welfare depends on and influences human welfare and environmental sustainability Measuring animal welfare: Behaviour 1. Ethograms: Simply mapping and defining behaviour without motivations/emotional valence 2. Activity budgets: Fractions of activity and rest in a period of time 3. Social interactions: Human-animal, and animal-animal 4. Environment interactions: Use of space 5. Behavioural diversity: Range of behaviours exhibited by an animal. Restrictive environments usually restrict the behavioural repertoire 6. Choice paradigms: Animal preference (ex. Y-maze) 7. Motivation tests: Amount of work animal is willing to put in to access a resource, interaction or activity 8. Cognitive bias assessment: Prediction of new experiences is dependent on past experience - Optimistic or pessimistic towards outcome Measuring animal welfare: Physiology 1. Weight 2. Thermal 3. Physiology (stress hormones, immune function) 4. Neural activity in response to different stimuli 5. Heart/respiratory rate (stress response) 6. Equipment we use to interact with animals 7. Environmental conditions Includes gross measurements, rates, hormones, biochemistry and physiology Dunning-Kruger effect = Pet owners believe they are better at things when they don’t have a lot of knowledge about it and are thus non-receptive to animal welfare efforts as they already consider themselves responsible and ‘better than average’ Cognitive dissonance refers to the state of having inconsistent thoughts, beliefs or attitudes, especially relating to behavioural decisions or attitude change. People who have already engaged in a behaviour that does not accord with their believe, even in light of new information, are less likely to be willing to change the behaviour, and more likely to find reasons to justify why the behaviour is necessary (usually stems from guilt over past actions) 6 Exploring welfare issues in companion animals Issue Effects Duration Intensity Domains Nutrition - 50% overweight, Long-term Medium, can Obese 10-40% obese. be worsened pets Reduces life by secondary expectancy, is health issues linked to secondary health issues and impacts quality of life Enviro - Leads to Short-term Low Dogs problematic but regular home behaviours and alone stress due to separation anxiety (especially post pandemic) Flat faced Crowded dentition, Lifetime High pets excessive skin (Brachyce folds, prominent phaly) eyes and closed  airways = major skin and eye issues, air hunger, breathlessness, sleep problems. High risk of heat exhaustion/stroke due to decreased respiration Dominant Leads to stress, Long-term Medium or aversive suppression of or lifetime style behaviour, training secondary health methods issues and anxious and unhappy animals. Primal dog dynamics are more family-based Stereotypi Repetitive Short-term Low but may cal behaviours may but be indicative behaviour possibly be useful repetitive of bigger coping (lifetime) welfare mechanisms in concern stressful or deprived environments Animal factors 7/8 Nutrition Macronutrients include carbohydrates, proteins, fat and fibre. As fed minus water equals dry matter (DM). Minerals and vitamins are also really important and are generally only consumed in very small amounts. Digestibility refers to the ability of a particular animal to internalise the components of food (metabolise and utilise nutrients). Different animals and different foodstuffs have different digestion efficiencies, and these are usually laboratory values not field values (environmental factors may come into play). Without adequate energy, all other nutrients are wasted. Without lysine, the animal cannot utilise other amino acids/nutrients. Energy is the baseline feed requirement in animal nutrition Animals can liberate energy from a lot of foodstuffs. In animal nutrition, we mainly focus on fats and proteins as a source of energy Proteins are required for growth and are composed of amino acids Essential amino acids: 10 essential AA in dogs and 11 in cats (+taurine, cats will not survive on dog food unless supplemented) Limiting amino acids: Main limiting acid is lysine, then threonine. Growing animals need an even greater percentage of these amino acids per kg of body weight Lipids can either be fats (animal based) or oils (plant based) and function as an energy storage mechanism. Essential fatty acids cannot be synthesised by the animal, such as arachidonic acid in cats (lacks enzyme to convert linoleic acid to arachidonic acid) Fibre is oftentimes used as dietary filler. Weight controls diets (animals feel satiated without increased intake of other macronutrients) Water sol aren’t stored Measuring feed components In vivo - Expensive but specific Within the animals - Growth trials, indicator trials In vitro - Cheaper, not species specific Laboratory tests - Chemistry, fermenters In sacco - Ruminant studies ‘In bag’ - Relies on ability to go into different parts of the animal and see what is happening (cannula) - Quite invasive (surgery) Dietary factors include feed processing, taste, forage consumption, anti-nutritional factors, energy density and water level People tend to begin demanding the same things in animal food that we see in human food, so we see the same trends but with a time lag as these become more established. Diets in companion animals include organic/natural, BARF (bones and raw food), grain free, kibble and raw. There are always disadvantages to putting animals on new diets as it is really difficult to meet all the criteria without missing some points. 9 Phenotypic selection Animal genetics is important because animals provide people with a variety of products, services and companionship in a range of environments, with genetic variation in livestock populations providing the opportunity to make genetic improvements to promote sound animal health and increase production. Good genetics is not an excuse for poor management and nutrition - animal health is multifactorial. Significant genetic variation exists in terms of disease susceptibility and resistance. Improvement in animal health through genetic selection is advantageous as genetic gain is cumulative and permanent and can persist in future progenies. Understanding of genetic principles and animal breeding technologies is crucial for improving animal health, production and wellbeing. Phenotypes (observable physical traits or characteristics) are a result of genetics and the environment. The Law of Segregation: Two alleles for each trait segregate in gamete formation and offspring inherit one genetic allele from each parent The Law of Dominance: An organism with alternate forms of a gene will express the form that is dominant The Law of Independent Assortment: Excluding linked genes, genes for different traits are sorted separately Almost every trait shows genetic variation Genetics terminology Term Definition Gene Shortest nucleotide sequence that codes for a specific function or trait. Genes come in pairs, because chromosomes are found in pairs in all cells except the gametes Chromosome One of a number of long strands of DNA and associated proteins present in the nucleus of every cell Locus/loci The specific location of a gene on a chromosome. If we cannot specifically identify the location of a gene, we locate a marker close to the gene Alleles An alternate form of a gene Dominant An allele that covers up the effect of the other allele Recessive The allele whose effect is covered up Trait Any observable or measurable characteristic of an individual Phenotype The measurement of a trait Simply inherited A trait only affected by a few genes, ex. Horned vs polled trait Polygenic trait A trait affected by many genes with no single gene having an overriding influence - not very easy to control for Qualitative traits Traits in which phenotypes are expressed in categories. Are affected by one or very few genes Quantitative traits Traits in which phenotypes show continuous (numerical) expression Polygenic control - many genes, each having a relatively small contribution to the genetic merit of the animal. Exception - a major  gene Major genes Genes that have a major influence on a quantitative trait, Ex. double muscling gene Breeding objective A clear goal of selection - focused, quantifiable and with a timeline Breeding value The value of an animal as a genetic parent EBV = herd average + heritability(average - individual phenotype) Heritability A measure of the strength of the relationship between breeding values (genotype) and phenotypic values for a trait in a population. Heritability is the fraction of total phenotypic variance that is due to hereditary or genetic effects. If there is a strong relationship between the phenotype and genotype, our progeny predictions will be more accurate Low heritability (50%) = carcass traits Dam A female parent Sire A male parent Two main concepts of animal breeding: 1. Selection - The process of choosing the parents of the next generation - Select more desirable animals and let them produce offspring, cull the animals with poor performance. Goal is to increase the frequency of desirable genes in the population - Natural selection: Selection that occurs in nature without human help - the stronger more vigorous animals are more likely to reach breeding age and produce offspring - Artificial selection: Selection under human control. Includes replacement selection (selecting new animals to become parents first or using artificial insemination) or culling (process that determines which parents will no longer remain parents) - Index selection: Involves calculating a total score for each animal based on the merit in each trait (weighting factor * phenotype for each trait added together). Selection indices are expressed as net profit per cow mated. Progeny value = ½ * bull value 2. Mating systems - The goal is to improve the efficiency of production and product quality - Random mating: A system in which mates are chosen at random - any male has an equal opportunity to mate with any female in the population (does not imply absence of selection) - Assortative mating: Mating individuals according to their phenotypes Positive assortative mating = Similar phenotypes (best to best and worst to worst) Negative assortative mating = Unlike phenotypes (best to worst). Involves corrective or compensatory mating to produce a progeny with medium performance - Inbreeding: A system of mating in which the mates are more closely related than the average of the population (can be mild or intense). Inbreeding uncovered genes that cause defects that have been hidden in the heterozygotes (usually recessive), resulting in an increased incidence of genetic defects. Inbreeding depression refers to the reduction in the population mean that occurs with increased inbreeding - more common for low heritability traits and reproductive traits - Outbreeding: The mating of individuals that have unlike pedigrees (less closely related than the average of the population. Reduces homozygosity and increases heterozygosity, increases the mean of the population, and less incidence of genetic defects - Outcrossing: The mating of individuals within a breed. Used to minimise inbreeding. Considered to be outcross if the mates have no common ancestors in the last 4-6 generations of their pedigrees. Maintains high levels of performance and low levels of genetic defects - Crossbreeding: The mating of animals from different breeds. Combines the good traits from different breeds when we crossbreed (typically dominant traits) - Breed complementarity: An improvement in the overall improvement of a crossbred offspring resulting from crossing breeds of different but complementary biological types. Usually involves crossing maternal breeds with paternal breeds - Heterosis/Hybrid Vigor: An increase in the performance of hybrids over that of purebreds, most noticeably in traits like fertility and survivability 10 Genomic selection Genetics may look at a single gene, but genomics look at all genes and how they interact to influence growth and development of an organism. Genomic testing can help predict future profitability potential by allowing producers to make more accurate animal selection and strategic breeding decisions. The goal of genomic selection is to rank animals based on their genetic merit as accurately as as early in the animal’s life as possible. Single nucleotide polymorphisms (SNPs) are a variation in a single nucleotide that occurs at a specific position in the genome, where each variation is present to some appreciable degree within a population. It is more cost effective to look at these genetic markers with known effects rather than sequence the entire genome of every animal in the population. Genomic selection is a two-step process: 1. The effects of the markers (>50000 SNPs) must be estimated in a reference/training population for which phenotypes and genotypes are available on the animals (essentially generate a model which is updated regularly to ensure accuracy) 2. This information is then used to predict the breeding values or EPDs of candidates for selection in a test (evaluation) population Example: Dairy cattle 1. Genotype a large number of bull calves from the population 2. Calculate the estimated breeding values or EPDs for these calves (accuracy = 0.80) 3. Select a team of bull calves based on these EPDs and sell semen from them as soon as they can produce it 4. This breeding design will reduce the generation interval from ~4 years to ~2 years and the rate of genetic gain will be doubled Reproductive strategies to speed up rate of genetic gain:  1. Artificial insemination 2. MOET (surrogates carry offspring of genetically desirable breeding pair) 3. JIVET 4. Sexing semen 5. Cloning For DNA collection, hairs are collected with the follicle intact (high amount of DNA). This is provided alongside the animal’s ID (tag), sterile equipment and dry hairs (wash hands and ensure sample is not contaminated with faeces), and that multiple hairs are taken (the more DNA the better) Genetic defects are diseases or disorders that are inherited genetically. A lethal gene is one that causes death of the individual prior to being born or within its lifetime (usually shortly after birth). A detrimental gene is one that is deleterious to the organism and decreases vigour and vitality but does not cause death. To eliminate genetic defects, we must cull the offspring with the defect, cull sires of the offspring with the defect, and replace those with sires that have a clean pedigree (i.e. sires that are not carriers of the defect, otherwise ¼ of their offspring will have the defect if mated with a female carrier) Environmentally caused Genetic defect - Defect occurred when the diet of the dam - Defect only occurs in certain breeding was deficient or when she was under other groups stress (ex. disease) - Defect occurs in herds where inbreeding is - Defect did not occur again after diets or practised environments improved - Defect occurs in more than one season - Defective offspring clustered in same year when diets and environments are different or season - Defect occurs at a low frequency (normally - Defective offspring occur frequently recessive) - Defect occurs more frequently in one breed DNA tests for genetic defects - When the exact location of the gene of interest is known, these DNA tests can detect carriers with 100% certainty. If the exact location of the gene is not know, but the location of a closely linked gene is known, the other gene can be used as a marker - Genotyping is DNA testing - uses a blood/tissue test - Genetic engineering can mean removing or replacing an existing gene, switching a gene on or off, or inserting a new gene altogether. This procedure relies on the production and repair of intentional targeted breaks in chromosomal DNA - CRISPR/Cas9: CRISPR comprises a single molecule of RNA that performs two jobs: one end binds to the target gene and the other delivers a DNA-cutting enzyme (Cas9) to the site. This allows for the replacement of faulty genes with healthy ones Agent factors 11/12 Toxins Term Definition  Toxin Any material which causes adverse health effects when it contacts or enters the body Toxic Used to describe the effects of a poison on biological systems Toxicosis Used to describe the syndrome of adverse health effects that result from exposure to a toxin Toxicity A measure of the capacity of a chemical agent to produce injury to living systems The dose makes the poison. Therefore a dose-response relationship must exist Mechanisms of toxicity include receptor-mediated, enzyme related, direct physical damage (free radicals), immune system related, DNA-related, and reproduction/development related Pesticides rely on selective toxicity, in which the agent is significantly more toxic to the target species than to non target species. This may be achieved through differences in toxic effect, differences in toxicokinetics, and selective exposure Toxicology Includes identification and classification of the poison, physical and chemical properties of the poison, biological effects and fate of the poison in the body. We look at effect at a population level Bioaccumulation The gradual accumulation of a toxin over time within an animal (ex. OPs are readily taken up into fat tissue which may be mobilised all at the same time) Biomagnification Process by which a toxin increases its concentration in tissues of animals as it travels up the food chain (apex predator = most at risk) Primary Animals directly exposed to the toxin. Prevented through reducing poisoning palatability and access to non target species Secondary Toxicity that occurs through contacting or ingesting another organism poisoning that has been directly exposed to the toxin. Prevented through using agents that biodegrade rapidly, or agents that require multiple doses to have a toxic effect Sources of toxins include metals, bacterial and fungal toxins, pharmaceutical drugs and household pesticides, and poisonous plants and animals. Effects of drugs are often dose dependent and continuous, whereas toxic effects a not continuous but are instead quantal - i.e. animal is dead/not dead, experiencing symptoms/not experiencing symptoms Margin of safety: Calculated as the dose that is lethal in 1% of animals divided by the dose that is effective in 99% of animals (LD1/ED99). The dose is generally expressed as the weight of drug or toxin per kg/g of animal weight Toxicokinetics: Describes the movement and fate of toxins once they contact or enter the body and describes four primary processes: 1. Absorption a. By ingestion (oral route) - One of the most important sites of absorptions, particularly in animals - Occurs along the entire tract, from mouth to rectum - Factors such as pH, GI motility, GI surface area and lipid solubility affect the rate of absorption, with lipid soluble substances generally absorbed more readily than water soluble substances - Barriers include digestive enzymes (saliva, stomach, intestines), alteration in pH (ex. Stomach acidity), motility of the GI tract and interactions with food and other drugs in the GI lumen b. Through the skin (percutaneous route) - The skin is relatively impermeable so the toxin must penetrate several cell layers before entering the small blood capillaries in the dermis - Outermost layer is the stratum corneum; this is the rate limiting step - Toxins pass through the skin via passive diffusion and enter the systemic circulation through venous and lymphatic capillaries in the dermis c. Through the airways (inhalation) - Generally gases, vapours, aerosols or volatile liquids with absorption occurring via the lungs  - Epithelial cells lining the alveoli are thin so the distance for chemical diffusion is very short. They are also in close contact with the capillaries, so chemicals and readily and rapidly absorbed into the blood 2. Distribution The rate of distribution depends primarily by blood flow and the rate of diffusion out of the capillary bed and into the tissues. Toxins will be internally distributed into different body fluid compartments (plasma water/bloodstream, interstitial water, intracellular water, fat). Eventual distribution is determined largely by tissue affinity, with some toxins accumulating in specific organs. Any toxin stored in the tissues will be in equilibrium with the free portion of toxin in the plasma, so it will be continually released into the circulation to be metabolised. 3. Metabolism Involves altering the physical properties of the toxin from those favouring absorption (lipophilic) to those favouring excretion in the urine and faeces (hydrophilic). Most often occurs in the liver. In most cases, metabolism terminates the effects of the toxin, however, in some cases the transformation initiatives the effects of the toxin Phase 1 reactions Phase 2 reactions - Catabolic - Anabolic - Usually form more chemically reactive - Usually lead to inactive products products - Mostly occurs in the liver but also kidney - Often involve cytochrome P450 enzymes in and lung the liver Reactions typically occur sequentially (1 → 2). Both phases decrease lipid solubility and increase water solubility, facilitating elimination in the urine Hepatic ‘first pass’ effect Important because differences in toxin effect may be dependent on the route of exposure and liver enzyme activity can be highly variable. The presence of liver disease may alter the toxicokinetics of toxins absorbed from the GI tract (more likely to suffer toxic effects as the toxin will not be effectively metabolised) 4. Excretion Hepatobiliary excretion: Elimination in faeces by liver Urinary excretion: Elimination in urine by kidneys All body secretions have the ability to excrete toxins, including saliva, tears, milk and exhaled air Variability in toxic effect depends on 1. Exposure time (acute vs chronic) 2. Dose (palatability, alternatives available, pasture management/seasonality, behaviour of animals, individual preferences) 3. Species differences (physiology and metabolism) 4. Toxicokinetic differences (adme) If given a case study ask: what is the toxic agent? What factors contribute to the signs of toxicity (toxin, species, individual, behaviour, toxicokinetics) Sources of poisoning in domestic animals; - Environmental - Industrial pollutants (metals, gases) - Naturally occurring toxins - Pesticides - Food source and household products - Toxic plants  - Feed and water contaminants - Secondary poisoning - Household drugs How do we investigate a potential poisoning: 1. Describe the condition 2. Identify a source of the toxic agent 3. Establish evidence of exposure to the toxic agent 4. Estimate the dose 13 Microbial pathogens Eukaryotes and prokaryotes differ in their size, metabolism, cell organisation, replication, maintenance of shape, nucleic acid handling, ribosomal structure and genome. Bacteria can catabolise all naturally occurring organic compounds, photoautotrophs use light, chemoautotrophs use chemical structures, chemoheterotrophs encompass all the pathogenic bacteria. Viruses and bacteria differ in their structural unit, genome, replication, generation of energy and size. Obligate parasites are not able to survive independently whereas saprophytes can live freely and do not need a host to survive. Not all infectious agents cause disease. For example, normal flora are always present, vary between species, have a role in health (vitamins, nutrient breakdown), have a protective role, are a source of opportunists and have significance in diagnosis (ex. Competition with pathogens). Specific sites include the mouth, stomach, intestines, lungs, vulva/vagina, skin and mammary gland (generally all mucosal surfaces). However an overgrowth of the normal microbiome can cause disease. Making a microbial diagnosis: (1) If an organism is detected, is it from the animal? Is it causing the disease? Is it the only one causing disease? (2) If an organism isn’t detected, is it because there wasn’t one there? Did it not survive the trop? Did I look for the right one? To ensure we make the correct diagnosis, we need to collect the sample from the right animal and the right place, treat the sample carefully and examine it as quickly as possible, and examine the results in light of the situation presented (the most common solution is usually the correct one) 14 Parasites Classification Biology Pathogenesis Lifecycles Groups Examples Protozoa - Free Intraintestinal Direct or Apicomplexa, Giardia, Unicellular living or or indirect. amoebae, Cryptospora, organisms parasitic extraintestinal Asexual or flagellates, Toxoplasma sexual ciliates  Trematodes - Parasitic Acute/chronic Indirect life cycles. Usually Fasciola Flukes disease hermaphrodites. hepatica Cestodes - Parasitic Usually chronic Indirect life cycles. Adult Echinococcu Tapeworms worm in intestine, larva in s, Taenia tissues (damage) Nematodes - Parasitic Acute or Direct or indirect. Exist as Ascaris roundworms chronic two sexes (dioecious) suum, dirofilaria immitis Disease dynamics and zoonoses 15/16 Epidemiological triad Classifying disease by: 1. Clinical sign (ex. Acute diarrhoea) 2. Syndrome (ex. Sudden death in cattle) 3. Anatomical abnormality 4. By cause (necessary cause, not sufficient cause) Sources of disease: 1. Environment (soil saprophyte, fungi and bacteria, opportunistic pathogens) 2. Other species (reservoir species, host range) 3. Own species (clinically affected animals, subclinical infections, latent infections, normal flora/microbiota - opportunistic) Cause - condition that contributes to a disease Necessary cause - condition that MUST be present for disease to occur Sufficient causes - set of MINIMAL conditions to produce disease (different combinations) Iatrogenic transmission - Horizontal transmission involving treatment/medical equipment Zooanthroponosis - Reverse zoonosis Examples of spillover: Rabies (canids), Ebola virus (primates), Nipah virus (bats), bovine TB, West Nile fever (birds) Livestock intensification - Increasing demand for animal products in developing countries. Leads to greater spread of infectious diseases and waste management problems Livestock extensification - Animals being kept more extensively and often producing less In-feed antibiotics - Emergence and spread of antibiotic resistance via the food chain and/or a contaminated environment, resistance genes can spread to other bacteria Disease control involves 1. Biosecurity: Limit vehicle entry, limit people entry, prevent contact with wildlife  2. Vaccination 3. Antibiotics? Sometimes… but not often! 17/18 Evaluating and classifying information Inductive reasoning - Looking at a situation then deducing what may come next (reasonably logical). Exceptions can still fall into inductive reasoning, but sometimes we may need to adapt our system if these exceptions are more common under certain circumstances Descriptive studies - Case reports, case series, survey (prevalence without a control) Analytical epidemiological studies - Cohort, case-control, cross-sectional Experimental studies - Lab experiments, clinical trials (disease cause, treatment effect) Null hypothesis: No difference exists between groups. The aim of the study is to reject the null hypothesis and illustrate a correlation between the two groups. We can reject the null hypothesis when results seen are statistically/biologically significant and are real effects rather than random error (chance) or systematic error (bias) Bias - Systematic error in design, conduct or analysis. Three types: (1) Selection in which study groups are not representative of the target population, (2) Information, (3) Confounding. Bias can be ruled out by examining the materials and methods to make sure the comparison was fair. It is easier to control bias in an experimental study than analytical study P-values - Is the observed difference between two groups likely to have occurred by chance? Small p values reject chance as a likely explanation for an observed difference. Precise studies are relatively free from random error and will favour rejection of the null hypothesis. The smaller the 95% confidence interval, the more precise the estimate (looking for low variation). Interpreting a study involves considering the point estimate (is this statistically and biologically significant), looking at the confidence interval, and looking at the p-value. Power of a study is the probability the null hypothesis will be rejected when there is a real difference of a given magnitude between treatments (decide what magnitude is important before the study begins) 19/20 Zoonoses and One Health 60% of all human infections are suspected of having human origins 75% of new and emerging human infectious diseases have animal origins Major anthropogenic drivers of zoonotic disease emergence: 1. Increasing demand for animal protein 2. Unsustainable agricultural intensification 3. Increased use and exploitation of wildlife 4. Unsustainable utilisation of natural resources  5. Travel and transportation 6. Changes in food supply chains 7. Climate change Destruction of habitats leads to migration, increasing the human wildlife interface. With global warming, vectors are also present in more regions around the world Cost effectiveness involves efficiency by volume (i.e. bulk production) and efficiency by variety (sharing of resources between stakeholders with different interests) 21 Zoonoses Recap Zoonosis: Diseases of humans in which the infectious agent is acquired from animals and for which animals are the reservoir of infection One Health: Concept incorporating interdisciplinary collaborations and communications in all integrated aspects of healthcare for humans, animals and the environment 22 One Health and control Transboundary animal disease: Diseases may spread beyond the individual property or state or country so control cannot be achieved at the local level (Ex. Bluetongue farm virus). Control of TADs involves: 1. Harmonising disease definitions 2. Harmonising diagnostic, treatment and vaccination methods 3. Promoting transparent exchange of disease intelligence 4. Promoting collaboration in agreed eradication campaigns 5. Facilitating trade Assist countries to achieve high national standards in animal health via: 1. Veterinary education 2. Regulation of drugs 3. Surveillance for disease incidence 4. Food security and supply (reduce pressure on animal populations) 5. Diagnostic services 6. Preparedness and response planning (use of models) State and Federal veterinary services National: Responsible for international trade, compliance with international standards, border controls, national disease surveillance and reporting State and territory: Responsible for disease control within their borders International organisations OIE - Aims include transparency, scientific information, international solidarity, promotion of veterinary services, food safety and animal welfare FAO - Working to build a world without hunger WHO - Leadership in global human health including setting norms and standards, developing evidence-based policy options, providing technical support and monitoring and assessing health trends. Key partnering role in control of zoonoses Biosecurity: All the measures taken to minimise the risk of pests and infectious diseases entering, emerging, establishing or spreading. Key components are quarantine (protects population of susceptible animals from diseased animals by imposing a barrier between the groups) and surveillance (track movement of disease via regularly tested sentinels) 23/24 The big picture and future directions Demand for animal health is being driven by three fundamental trends: 1. Population growth - Means increased demand for protein. The role of veterinarians will be critical in helping farmers increase productivity to meet that demand in a sustainable way 2. More people with disposable income - Means high protein diet and animal companionship. People are increasingly willing to spend income on the health of their animals 3. Urbanisation - Changing the way animal proteins are produced, what people eat in their diets and how well people understand food production today At the same time, being closer to animals increases the risks of the emergence and spread of zoonotic diseases Feeding the world while addressing climate change is one of the biggest challenges of the 21st century. Agricultural production will need to increase by roughly 70% to accommodate the growing population. It encompasses: 1. The logistics of producing more protein in the face of constrained natural resources such as limited arable land and fresh water 2. Challenges from diseases that threaten the health of farm animals and the safety of the food supply 3. Increasing consumer influence - transparency across the food chain and pet owners wanting to know more about pets’ health and wellbeing Technology for animal health monitoring: smart collars (positional and activity) available for both companion animals and production animals (smart sensing, health monitoring, dashboard and alerts). Livestock versions are focussed on water consumption, space use, subclinical plant poisoning, behavioural differences, and animal theft (solar-powered collars). Another new tech is virtual fencing that lightly shocks animals to keep them restricted to certain areas, and the MooMonitor for detecting fertility and cow health. Instant diagnostics = PCR, dipstick tests Weekly case studies W2 Live export Live export refers to the transport of animals to other countries for a variety of purposes, including slaughter and breeding, with Australia having one of the biggest live export industries in the world. Generally, animals reared in the south of Australia are exported to the Middle East and animals reared in the north of Australia are exported to South-East Asia (ex. Singapore). Heat stress of animals during the journey and after arrival in the destination countries is one of the main welfare concerns for exported animals, with mortality rates peaking around July to August. To combat this, the Australian government banned the live shipment of sheep to, or through, the Middle East between 1 June to 14 September every year. However, animal welfare advocacy groups are critical of the use of mortality rates as the sole indicator of voyage welfare, as it is not representative of the ways in which animals are being affected outside of mortalities in terms of the five domains of animal welfare (nutrition, environment, health, behaviour and mental state). Two of these concerns are stocking density (should be reduced by up to 60% some months in fairly ventilated environments to minimise the risk of heat stress) and animal handling at/after export (combatted through the Exporter Supply Chain Assurance System for transparency and targeting welfare problems throughout the supply chain). Suppliers export live animals rather than frozen meat for various reasons: (1) The existence of wet markets for fresh meat in importing countries, (2) Economics (cheaper to slaughter in other countries), (3) Cultural reasons (ex. Religious festivals). Australia is attempting to phase out live sheep export despite this opposition from suppliers. W3 When Peppa bit Rudy - Managing companion animals by managing humans There is a need to remove breed-related stigma and focus on owner problems, ‘any dog can bite’ campaign. Understanding dog personalities and behavioural signs can prevent attacks. W4 Nutrition calculations (1 kcal = 4.184 kJ) ‘As fed’ refers to the form in which the food is presented to the animal (includes a moisture/water component) whereas ‘dry matter’ refers to the food composition if we take out all the water (100 - moisture %). Foods vary greatly in their water content, and so expressing everything on a dry matter basis allows us to compare the nutrient compositions of different foods and apply these to the animal’s nutritional requirements. W5 Breeding heat tolerant cows and eliminating genetic defects Heat stress causes reduced feed intake, inflammation, panting and respiratory alkalosis, and gut damage and affects lipid/carbohydrate metabolism, immunity, apoptosis and oxidative stress. Preventing heat stress involves three basic approaches: (1) Adjusting the environment (shade, baths, misting/sprinklers), (2) Nutritional supplements, and (3) Genetic manipulation. Crossbreeding is used to combine desirable traits from different breeds (breed complementation), however this cannot be applied to dairy cows as there is a negative association between thermotolerance and milk production. One gene at the SLICK locus coding for a short and slick hair coat (thermoregulatory phenotype) has been successfully introduced from Senepol cattle into lactating Holstein cows. In terms of developing heat tolerance GEBV, the following steps are applied: 1. Defining heat tolerance (set goals) 2. Understanding how heat tolerance has developed and the existing scope of variability in dairy herds 3. Make a genomic prediction 4. Take a herd with equal numbers of heat tolerant and heat susceptible individuals and test the genomic prediction Eliminating genetic defects involves culling the offspring with the defect, culling the sire of the offspring with the defect, and replacing the sire with an unrelated sire. Dams may also be culled depending on the position in the industry (i.e. breeders). It is also important to avoid purchasing a carrier sire as if there are any carrier dams in the herd, ¼ of their offspring will have the defect. Genotyping can be used to identify and possibly even eliminate genetic defects in a herd or candidate sires and dams (use SNPs instead of whole genome sequencing to save costs). W6 Sammy’s acting really weird - Investigating a poisoning and the mechanism of antidotes Evidence required to determine whether clinical signs may be related to a poisoning include: (1) Development of signs in a previously well animal, (2) Evidence of exposure to toxic agent, (3) Signs consistent with known toxic effects, (4) Presence of toxic agent in the stomach or other tissues. Methiocarb metabolites are still quite toxic so the first pass effect doesn’t really apply despite ingestion. To limit absorption: 1. Gastric lavage (stomach) 2. Enema (large bowel) 3. Activated charcoal (binds toxin in small intestine) The mechanism of action of methiocarb is irreversible binding to the AChE enzyme responsible for the termination of ACh activity at nerve terminals. Muscarinic signs include bronchial secretions, salivation and uncontrolled excretion, nicotinic signs include muscle twitching, tremors and seizures and CNS signs include restlessness and seizures. Atropine is a muscarinic antagonist (reversibly blocks ACh receptor) so it controls the muscarinic signs only. Phalaris contains an unidentified toxin that inhibits nitrogen metabolism, resulting in elevated ammonia levels in the blood and brain damage. 1 Describe the condition, 2 Identify source, 3 Establish evidence of exposure, 4 Estimate the dose W7 Calf diarrhoea The primary viral causes of calf diarrhoea are rotaviruses, coronaviruses, astroviruses and bredaviruses. The primary bacterial causes are ETEC and Salmonella. Protozoan causes include Cryptosporidium (acid fast stain due to small size), Eimeria and Giardia. The primary parasites at risk of spreading to humans are Giardia and Cryptosporidium, particularly in children and the elderly. W8 Cysticercosis A definitive host is a host whereby the the parasite reaches sexual maturity and begins shedding eggs, whereas an intermediate host is one in which the larval stages of the parasite live (often as cyst structures in tapeworms) following the ingestion of eggs shed in the faeces of the definitive host. For Taenia solium, the definitive host is humans and the two intermediate hosts are humans and pigs. The main reason is that humans are not eaten by humans and so cysts are not ingested in the tissues of other people (dead-end hosts). Another reason is that human cysts generally become non-viable due to the immune response but can still cause pathology such as epilepsy. The primary features propagating Taenia solium transmission in disadvantaged communities are: (1) A lack of comprehensive toilet or waste management facilities, (2) Pigs roaming free to access human faeces), (3) Home slaughter of pigs (inadequate meat inspection), (4) Not cooking meat sufficiently to kill cysts, (5) Human faeces in water supplies, (6) Lack of facilities for hygiene, (7) No regular worming treatment of people. A vaccination for pigs rather than humans was decided on for a few reasons: (1) Greater spread and cost-effectiveness for approval and registration (2) Equally effective as the tapeworm life cycle requires pigs (3) Avoids vaccine hesitancy An antiparasitic drug was used in combination as it renders existing cysts in the pigs non-viable, while the vaccine presents new cysts from forming W9 Human mistakes - Rabbit haemorrhagic disease and bovine spongiform encephalopathy RHDV infects only rabbits and has been used in some countries to control rabbit populations as it is highly infectious and often fatal. Field studies investigating natural transmission were undertaken on Wardang island, with strict PC4 biosecurity protocols implemented (control mosquitoes and flies, rabbit-free zone around quarantine areas, surveillance of other animals, electrified fence, etc.). The location was chosen as it is (1) An island which prevents the movement of rabbits onto the mainland, (2) Is uninhabited so there will be no human traffic to and from the island, and (3) Is a suitable habitat for rabbits that mimics their natural habitat. However, the island is very close to the mainland which is quite concerning. The virus was detected in two sentinel sites outside the quarantine area months after initial testing had commenced. The CSIRO attempted to frame this breach in a positive light suggesting it illustrates the potential of RHDV as a biocontrol agent against rabbits. Eventually, a dead rabbit was detected on the mainland due to mechanical transmission from bush flies feeding on the blood of dead rabbits. There were many things that should have been done differently throughout the quarantine and breach process. (1) There should have been a greater effort to reduce insect-borne transmission, (2) If this was not possible, testing should have been carried out on an isolated island further from the mainland, and (3) The media release should have been less misleading. vCJD is a variant of CJD (human spongiform encephalopathy) that is non-sporadic and appears to follow a very consistent pattern of damage that mimics BSE. There should have been a greater investigation into the transmission of BSE and a cease on consumption of beef until transmission was fully understood. Furthermore, people with authority should not have been making claims that eating beef was safe, as this was actually the root cause of the disease and propagated transmission in an attempt to silence fear mongering. W10 Zoonoses and One Health Investigating a novel disease. The first step is to identify the origin of the disease: (1) The type of pathogen is determined, (2) Use genomic sequencing to figure out whether the disease in animals is the same as in humans, (3) Test if the pathogen isolated from an animal will cause disease in the animal. The next step is to investigate sources of disease: (1) Antibody test the animal, (2) Antibody test humans, (3) Antibody test local wildlife, (4) Sample the environment. If there are antibodies, it indicates the animal/person has had the disease in the past, if there are active pathogens in the tissues, it indicates the animal/person is an asymptomatic carrier of the disease (reservoir host). Bats are such good reservoirs and transmitters of viral zoonoses as their ability to fly causes damage at the cellular level (inflammatory response). Bats have dampened down their inflammatory response as an adaptation of this requirement to fly, and so the body is naturally well-protected against viruses. Other viruses implicating bats as a reservoir host include MERS, SARS and Ebola. W11 Rabies and Australian bat lyssavirus Rabies is caused by an RNA virus called Rabies lyssavirus (Rhabdoviridae), with several genotypes that may be host or geographically associated but all behave in the same way in terms of pathogenesis. Rabies affects all warm-blooded animals but primarily mammals; birds are not typically considered as natural infection is extremely rare with no clinical signs. The virus concentrates in animal saliva and is transmitted when it comes into contact with fresh wounds or unprotected mucous membranes of non-vaccinated animals/people. Signs of illness may appear within 10 days and several months, and death typically occurs within 10 days after clinical signs are present. The course of infection follows behavioural change, progressive paralysis, coma and then death. Behavioural changes in dogs and cats are either a depressed form (only bites when provoked) or a restless form (snapping, restlessness, eating strange objects). Cattle become depressed, stop producing milk, salivate, bellow, and may attack other animals. Control options: Humans - Pre-exposure vaccination or post-exposure vaccination and immunoglobulin administration Domestic animals - Vaccination and desexing Wildlife - Oral bait vaccines (sylvatic cycle) The SARAH program in Sikkim has been successful in reducing rabies as it has developed a stable pool of vaccinated desexed dogs to prevent incursion by external unvaccinated dogs. Alternatively, culling programs simply open up new resources for new dogs and offspring to fill. Australian bat lyssavirus works very similarly to rabies in terms of its clinical signs and its 100% mortality rate after the presentation of these clinical signs. It is generally seen as an emerging disease, not necessarily because it is a novel disease in bats, but because human encroachment into bat environments with urbanisation has increased the human-bat interface and increased the opportunity for infection. However, there is no continuous cycle of transmission, with only 3 humans and 2 horses infected. W12 Antimicrobial stewardship - Dairy farm and prawn farm Antibiotics are used to treat or prevent the onset of bacterial infections in humans and animals, but bacteria and other microorganisms naturally develop resistance to antibiotics over time through genetic changes. These resistance genes can also be passed between different bacterial strains/species and are accelerated by inappropriate antibiotic use, including taking antibiotics for viral infections, prescribing antibiotics when they are not genuinely required, overuse in animals and animal production, and not following professional prescribing advice (ex. Underdosing or not completing the whole course). Indiscriminate antimicrobial use contributes to the rise in antimicrobial resistance by increasing the overall selection pressure for the development of the resistance. Even if these genes are developed in non-pathogenic or non-target bacteria, they can be transferred to pathogenic bacteria (ex. Through bacteriophages). Underdosing contributes to the rise in antimicrobial resistance as it simply removes the most susceptible population, leaving the less susceptible to reproduce (selection pressure). In terms of sample collection, for any organism that can be cultured, antimicrobial susceptibility testing is vital - should pick a chemical that kills the target organism but avoid reaching for top-shelf antimicrobials (especially in animal medicine as these are primarily reserved for majorly untreatable human cases). A majority of animal cases do not actually require antibiotics, especially not immediately, and so animal owners should strive for proactive prevention rather than reactive treatment. Client education is particularly important in this sector, especially for companion animals and in industries where animals are the sole source of income. This involves informing owners why their animal did/did not receive antibiotics (only used when absolutely necessary and where the condition would not improve or worsen without them). It also involves owner actions, such as following prescribing information as closely as possible, educating owners on antimicrobial resistance, and monitoring the animal for signs of improvement or non-improvement to determine the efficacy of continuing to use the antimicrobial. A majority of shrimp production occurs in low- and middle-income countries where antimicrobial use is largely unregulated. Additionally, untreated human waste is regularly deposited in water stores. Through antibiotic pollution in the environment, there has been a surge in the levels of antimicrobial-resistant bacteria surrounding these shrimp farms, as well as the number of bacteria with resistance genes even after antimicrobial use has ceased. To prevent this, water should be thoroughly cleaned and preferably sterilised or filtered to remove contaminants. Then, clients should be educated on appropriate antimicrobial use and waste management, and potentially join a certification program to ensure any production losses from following these practices are adequately compensated. Specific case studies and examples