Tissue and Organ Injury Response

• This lecture outlines the response to injury at the tissue and organ level (selected organs)
• Requires defining tissue and organs

Tissue

• A group of cells in an organism with similar structure and function
• Four types of tissue are connective, epithelial, muscle, and nervous

Organs

• Combination of tissues working together to perform a specific function in the body
• Examples are the heart, lungs, liver, and kidneys

Injury at the Tissue Level

• Tissue may be injured by heat, cold, chemicals, toxins, or trauma
• Injured animal tissue reacts by the process of inflammation
• Inflammation increases capillary permeability and blood flow to the affected tissue

Inflammation

• Inflammation increases the number of white blood cells and antibodies to fight infection

Signs of Inflammation

• Heat
• Redness
• Swelling
• Pain
• Loss of function

Description of Inflammation

• The suffix "-itis" describes an inflammatory process
• Mastitis is inflammation of the udder/mammary glands
• Gastritis is inflammation of the stomach
• Hepatitis is inflammation of the liver
• Nephritis is inflammation of the kidney
• Arthritis is inflammation of the joint(s)
• Metritis is inflammation of the uterus
• Bronchitis is inflammation of the bronchus (lungs)

Example of Inflammation

• Mastitis has the symptoms of heat, redness, swelling, pain, and loss of function

Abcess Formation

• The body detects and responds to a foreign body by activating specific cells
• Different cells work together to fight the foreign body
• Pus, or purulent materials, results from dead neutrophils

Injury at the Organ Level

• Responses are dependent on the particular organ involved

Digestive Tract Injury

• The basic response is increased secretion rate and motility
• Vomiting results from injury in the upper tract
• Diarrhea results from injury to the lower tract

Respiratory Tract Injury

• The response is similar: increased secretion and motility
• Sneezing results from injury above the pharynx
• Coughing results from injury below the pharynx

Urinary Tract Injury

• Increased motility is seen as "straining" and is often confused with constipation and parturition

Kidney

• Kidneys filter waste products from the blood circulation and eliminate them in urine
• Acute kidney injury can result from the presence of kidney stones (uroliths)
• Stephanurus dentatus, the kidney worm of pigs, and Dioctophyma renale, the giant kidney worm of dogs, may also cause injury
• Microbial infections can cause kidney injury, e.g. leptospirosis
• Toxins like nephortoxins can cause kidney injury
• Kidneys might be injured by lack of blood flow, blockage in urine flow that causes infections
• Direct kidney damage by infections, medications, or toxins can also injure the kidneys
• Autoimmune conditions can also injure kidneys
• Serious complications of acute kidney injury (AKI) include high potassium levels
• High potassium can lead to muscle weakness, paralysis, and heart rhythm problems
• Too much fluid in the body can cause edema in the extremities or pulmonary edema
• AKI denotes a sudden and often reversible reduction in kidney function
• Acute renal damage or injury can lead to renal failure and death if no intervention is done

Liver

• Liver damage is common in farm animals
• Plant toxins like Brachiaria decumbens can damage the liver
• Migrating parasites like Ascaris suum, (roundworm that affects pigs) can damage the liver
• Microbial infections like leptospirosis and metabolic disturbances like ketosis can cause liver damage

Mild Liver Damage

• Results in fat infiltrating the liver cells leads to fatty degeneration
• Reversible if the problems are removed quickly and the damage is not severe

Severe Liver Damage

• Leads to death of liver cells
• Liver cells do not regenerate well and are replaced by fibrous or scar tissue
• Scar tissue causes damage to the surrounding tissue which may die
• The larger area of dead tissue is replaced by more scar tissue

Liver Cirrhosis

• This process leads to a progressive damage to the liver
• Complete repair is unusual and there is often progressive damage that may lead to total liver failure months or years after damage

The Skin

• Injury or insult to the skin also results in increased secretion
• Damaged or dead cells are quickly replaced and the area is healed by first or second intention healing
• The skin is the largest organ

Dermatitis and Folliculitis

• Skin conditions

Gangrene

• Gangrene occurs when a large amount of tissue dies (e.g. burns on skin or acute staphylococcal mastitis) and saprophytic bacteria colonize the dead area
• Gangrene is usually blue or black, cold, and painless
• If cut/incised, it does not bleed
• Very often the affected tissue sloughs i.e. falls off
• The gangrene bacteria often cause toxic substances to enter the general circulation, the animal becomes inappetent, and there is an onset of fever

Abcesses

• An abscess may develop with a deep-seated infection, especially if drainage is impeded e.g. puncture wounds
• Inflammation is the body's normal response to injury
• If the inflammatory process does not eliminate the infection immediately, the body builds a fibrous wall around the seat of infection to contain it
• This is a young or immature abscess
• At this stage there is hot, red, painful and swollen area
• The infection is contained in this wall until the body defense system effectively neutralizes it
• The wall progressively softens until it bursts at the weakest point
• At this stage the area is cold, not painful and very soft
• This is a mature or ripe abscess

Best management of Abcesses

• Abscesses are best managed by allowing them to ripen and then they are lanced at a point to facilitate good drainage just before it ruptures naturally
• Drainage is short and healing is quick
• Drainage is short and healing is quick, and lancing before maturity may result in the opposite
• Antibiotics are not useful in an ordinary abscess
• Antibiotics do not penetrate the fibrous tissue well and antibiotics tend to delay the onset of maturity

Cellulitis

• Sometimes the deep layers of the body are infected and the inflammatory process fails to wall off the infection effectively
• Or the walling off process starts but is weak and ruptures prematurely
• The infection then spread rapidly over large areas of the body causing a rather severe condition called cellulitis
• The tissue is hot, very swollen and painful and the animal is ill and in danger of dying
• Dog bite in goats is a good example
• Treatment is by large dose antibiotics very early
• Do not attempt to lance

Outline

• Evaluate basic health status of a ruminant based on clinical signs
• Evaluate basic health status of a ruminant based on medical history and physical examination
• Describe the biological, physical environment and management practices required for the health and welfare of farm animals
• Recognize that veterinary conditions are often caused by non-infectious causes

Health Defined

• Is a state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity by the World Health Organization (WHO)
• The Office of International Epizootics (OIE) is the World Organisation for Animal Health
• The OIE collects and analyses information on diseases originating in animals

Animal Health

• Animal health is essential for animal welfare and is a growing consumer concern
• Since 2000, the OIE develops international standards
• These include conditions for transport, slaughter and production
• 60% of human pathogens are of animal origin
• 75% of emerging animal diseases can be transmitted to humans
• Five emerging diseases appear each year

Animal Welfare

• Means how an animal is coping with the conditions in which it lives
• An animal is in a good state of welfare if indicated by scientific evidence
• An animal is healthy, comfortable, safe, well-nourished, able to express innate (natural) behaviour, and not suffering unpleasant states that cause pain, fear, and distress

Animal Welfare Components

• Good animal welfare requires disease prevention and veterinary treatment
• Appropriate shelter, management, nutrition, humane handling, and humane slaughter are also needed
• Animal welfare refers to the state of the animal
• Treatment is covered by other terms such as animal care, animal husbandry, and humane treatment
• Protecting an animal's welfare means providing for its physical and mental needs

Five Freedoms of Animal Welfare

• From hunger and thirst (provide ready access to fresh water and maintain a healthy diet)
• From discomfort (provide an appropriate environment with shelter and a comfortable resting area)
• From pain, injury, or disease (prevention and rapid diagnosis and treatment)
• To express normal behavior (provide sufficient space, proper facilities and company of the animal's own kind)
• From fear and distress (ensure conditions that avoid mental suffering)

Characteristics of a Healthy Animal

• Physical appearance: bright/dull skin and coat, parasites, hair loss (alopecia)
• Gait: normal, abnormal (lame, limping)
• Posture: weight bearing, non-weight bearing
• Behavior: bright, alert, responsive, depress, signs of discomfort (bellowing, bleating)
• Activity level: normal, abnormal, reluctant to move, laying down
• Discharge from orifices: nasal, ocular, vaginal, oral, anal (eyes, ears, mouth, nose, vagina, anus)
• Body Conformation: Determined by muscle and fat coverage over the transverse and spinous processes of the vertebral column in the loin area determined by the Body Condition Score (1-5) where 1 is emaciated and 5 is obese
• TPR (Temperature, Pulse/Heart rate, Respiratory rate
  • Sheep Temperature 38.3- 39.9 degrees Celcius, HR 70-80, RR 16-34
  • Goat Temperature 38.5 - 39.7 degrees Celcius, HR 70-80, RR 10-20
  • Cattle Temperature 38 - 39.3 degrees Celcius, HR 40-80, RR 10-30
• Rumen function- The rumen is located on the left side of the animal in the left paralumbar fossa
  • The para-lumbar fossa is the triangular shape depression that is below the vertebral column
  • Should feel the rumen contract and push back against your fist
  • 2 strong contractions should be felt in 3 minutes or 1 contraction in 2 minutes

Rumen fill

• Is the result of dry matter intake, ration composition, digestion and the rate of passage of ingested feed
• Rumen fill scoring is useful for identifying possible feeding and feed intake problems
• Rumen fill score 1-5

FAMACHA Scoring system

• Designed to identify animals that are anemic due to parasite burden so deworming only occurs on these animals
• Deworming in this manner saves the farmer the cost of deworming the entire herd.
• Deworming in this manner saves the farmer the cost of deworming the entire herd
• Red is Optimal, then there is Red-pink, Pink, Pink-white and last is White which means Fatal leading to required drug dose

Productive Parameters

• Feed Conversion Ratio (FCR) is the amount of feed the animal eats to gain a live weight of 1 kg
• Average Daily Gain is the rate of weight gain per day over a specified period of time
• Fertility is successful establishment of pregnancy
• Fertility rate is generally very good once animals are fed properly
• Average daily weight gain (ADG) = (FinalWeight - Initial Weight) / Days

Requirements for Maintenance of Good Health and Welfare

• Feed quantity and quality to promote development and immunity
• Shelter and ventilation to promote comfort and help good health
• Freedom from infectious diseases via vaccinations and treatments
• Appropriate biological and physical environment through socialization and comfortable environment
• Most problems farm animals experience is caused by management and poor animal husbandry