Microorganisms & Infection Diseases PDF

## Micro-organisms ### Infection Colonization of an individual host by a foreign micro-organism. ### Pathogen Infectious agent that causes harm. ### Disease Occurs when normal bodily functions are sufficiently impaired to reduce performance, leading to clinical signs. ### Contagion Disease sprea...

## Micro-organisms ### Infection Colonization of an individual host by a foreign micro-organism. ### Pathogen Infectious agent that causes harm. ### Disease Occurs when normal bodily functions are sufficiently impaired to reduce performance, leading to clinical signs. ### Contagion Disease spread directly/indirectly from one to another. ### Types of Microorganisms * Bacteria - Strep/Staph * Virus - Covid, Parvo, FeLV * Fungus - Dermatophytes * Yeast - Malassezia * Protozoa - E. cuniculli * Parasite - Endo/Ecto * Prions ### Bacteria * Size: 0.5-5 micrometres * Unicellular * Cell wall mainly peptidoglycan * 3 Basic shapes * Bacilli: eg. Salmonella * Spirals: eg. Helicobacter * Cocci: eg. Strep/Staphylococcus * Gram Staining Used * Gram Positive = Purple * Gram Negative = Pink ### Bacteria Cont. #### Structure * Cell membrane - within cell wall. Selectively permeable. * Cytoplasm - Contains dissolved nutrients, waste + enzymes. * Nuceloid - Bacterial chromosome suspended within cytoplasm * Ribosomes - Contain RNA for protein synthesis. * Plasmid - Small piece of DNA which can replicate independently of the chromosome. * Flagellum - Form of movement ### Endospores (spores) * Produced by some species of Bacteria. * Dormant. Formed when a growing cell is deprived. * Hard to get rid of. * Common techniques * Autoclaving (moist heat $121^\circ C$ under pressure 6.9 kPa for 15 mins +) * Repeated steaming * Dry Heat ($160^\circ C$ for at least 2 hrs) ### Reproduction * Requirements * Supply of suitable nutrients * Correct temperature (body temp) * PH (7-7.4) * Water * Correct gaseous environment * Obligate Aerobes - need oxygen * Obligate Anaerobes - don't need oxygen * Reproduce asexually 1. Cell replicates its DNA 2. Cytoplasmic membrane elongates + seperates DNA 3. Cross wall forms 4. Cross wall forms completely - Septum 5. Daughter cells are formed ### Conjugation - (plasmid) Passage of DNA from donor bacterial cell to another (recipient) 1. Donor + recipient cells pulled together by sex pilus, formed by donor cell. 2. Pilus retracts, bringing cells together. Cell membranes fuse to cause a channel. 3. Plasmid replicates and goes to recipient. Cells seperate - recipient becomes donor as now has plasmid. * Rare in gram-positive bacteria. * Causes antibiotic resistance. ### Bacterial shapes and arrangement #### Arrangements of Cocci * Coccus * Diplococci * Tetrad * Sarcina * Staphylococci * Streptococci #### Arrangements of Bacilli * Bacillus * Diplobacilli * Streptobacilli * Pallisades * Coccobacilli #### Arrangements of Spiral * Spirilla (Helical-shaped\Corkscrew form) * Spirochetes * Vibrio ## Types of Viruses * Helical Virus: * Like the Tobacco Mosaic Virus which infects a number of different types of plants, have a slinky-shaped capsid that twists around and encloses it's genetic material. * Polyhedral Viruses: * Like adenoviruses, which are known to cause a range of illnesses from Pink eye to pneumonia, are composed of genetic material surrounded by a many-sided capsid, usually with 20 triangular faces. * Spherical Viruses: * Like the infamous Coronavirus, are essentially helical viruses enclosed in a membrane known as an envelope, which is spiked with sugary proteins that assist in sticking to and entering host cells. * Complex Viruses: * Like bacteriophages, which infect and kill bacteria, resemble a lunar lander, and are composed of a polyhedral "head" and a helical body (or "tail sheath"), and legs (or "tail fibers") that attach to a cell membrane so that it can transfer it's genetic material. ## Viruses (virion) * Size - 20-300 nanometres * Non-cellular, no cell wall + no nucleus. * Incapable of reproduction without host * Each particle is made up of: * Nucleic Acid (DNA/RNA) forming central core * Protein coat - capsid * Varies shapes: * Helical (Can be enveloped/non-enveloped - giving 4 basic shapes) * Icosahedral * Complex (poxvirus) * Composite (bacteriophages) ### Replication * Only able to attach to cells with complementary compatable receptor. * Eg. Influenza attaches to ciliated epithelium of resp tract. * Specificity is known as tissue tropism. * Normally only infect one or two hosts. ## Transmission * Host to host either directly/non-directly. * Example: * Direct - Cat licking feline calicivines of another cat. * Indirect - Dog licking floor where parvo has been. * Different viruses have adapted ways of transmission. * Example: * Resp tract virus transmitted via particles being sneezed out and breathed in by others. ## Incubation Time between first infection and clinical signs can still spread during this time. ### Examples: * Feline Panleucopenia - 2-10 days * Feline Leukemia - Months - Years * Feline Calicivines - 1-7 days * Rabies - +/- 2 months (3-8 weeks) * Canine Distemper - 7-21 days * Canine Parvo - 3-5 days * Canine Hepatitis - 5-10 days. * Canine Parainfluenza - 3-10 days ## Diagnosing viral infections * Clinical signs + patient history. * Use of electron microscope. * Polymerase Chain Reaction (PCR) - amplify + detect nucleic acid of virus. ## Treatment * Fluids (IV+Oral) * Tempting foods * Antibacterials to limit secondary bacterial infections * Vaccination - preventative - immune response * Antiviral treatments ## Prevention * Border policy (vaccination policies) * Accommodation design * Suitable disinfectants + contact times * Vaccinations ## Prions * Proteinaceous particles * Infects central nervous system eventually leading to death. * Incubation period - 2 to 20 years! ### Diagnoses * Post mortem examination * Lymph node samples from live animals now possible ### Fungi - * Grows aerobically (using oxygen) * Gains energy from substances in which they grow. * Moulds - Multicellular * Dermatophytes * Yeasts - Unicellular * Malassezia * Candida albicans ## Incubation Periods - Viruses * Feline Panleucopenia - 2-10 days - Icosahedral * Feline Leukemia - Months - Years - Icosahedral * Feline Calicivines - 1-7 days - Icosahedral * Rabies - 3-8 weeks - Helical * Canine Distemper - 7-21 days - Helical * Canine Parvovirus - 3-5 days - Icosahedral * Canine Hepatitis - 5-10 days * Canine Parainfluenza - 3-10 days - Helical ## Bacterial Diseases **Disease** | **Shape**| **Gram Staining** | **Species** ------- | -------- | -------- | -------- Salmonellosis | Rods | Negative | Dog Campylobacteriosis | Curved rods | Negative | Dog Kennel Cough | Short rods | Negative | Dog Leptospirosis | Spirochaete | Negative | Dog Lyme Disease | Spirochaete | Negative | Dog Streptococcal infection | Cocci | Positive | Dog Staphylococcal infection | Cocci | Positive | Dog Tetanus | Long rod | Positive | Dog Mycoplasmal conjunctivitis | Pleomorphic - no wall | Negative | Cat Cat bite abscess | Rods/Coccobacilli | Negative | Cat ## Immunity * Body protects against diseases * Detecting + resisting microbial/parasitic invasion * Three basic levels * Physical barriers * Innate immunity * Acquired immunity ### Physical barriers * Skin - Surface of GI, resp + urogenital tracts. * Movement of mucous secretions aid in cleaning pathogens. ### Innate immunity * Next layer of defence * Pre-existing - saliva containing enzymes * Rapidly activated - inflammation + phagocytosis ### Acquired immunity - (Humoral/Cellular) * Recognises and respond to foreign pathogens. * Produces specific cells and antibodies directed against the pathogen involved. * Takes several days to act against pathogen. * Memory cells are formed following exposure. #### Humoral - B lymphocytes * B lymphocytes develop into plasma, form antibodies. * Can be acquired by passive transfer of antibodies (maternally derived antibodies - MDA) across placenta and in colostrum. * Efficiency declines within hours of birth - delays to colostral intake = Poor passive immunity = increased risk of infection. ### Humoral cont. * Active immunity invokes immunological memory * Quickly + Specifically recognise antigen that body has seen before * Passive immunity is temporary protection, MDA declines to non-protective level within few weeks. ### Cellular immunity * Doesn't involve antibodies * T-lymphocytes make chemical messengers (cytokins) help direct immune cell functions + responses #### Types of T cells * Helper T cells * Cytotoxic T cells * Supressor T cells * Natural active immunity - antibodies produced by lymphocytes in response to disease * Natural active immunity - more relevant to viral diseases rather than bacterial diseases. * Artificial active immunity - vaccines * Natural passive immunity - maternally derived antibodies supplied to neonate in colostrum first milk. Provides protection for first 8-12 weeks * Artificial passive immunity - administration of antiserum containing antibodies produced by donor. Only lasts few days as foreign. ## Physical Barriers * Skin * Sebaceous glands - Produces sebum. Acidic pH environment prevents replication. * Sweat glands - Sweat - Lysozymes, antibacterial properties. * Mucous membranes * Conjunctiva - Produces Tears. * Respiratory tract - Mucus + Saliva, contains lysozymes. * Hairs - Cilia - Mucous-producing glands, traps bacterial/foreign material within mucus + hairs "sweep" away * Secretions * Semen - Antibacterial properties * Vagina - + Zinc - Acidic environment inhibits bacterial growth * Stomach acid - Inhospitable environment for any swallowed pathogen. ## Immunity *Non-specific/innate* | *Specific/adaptive/acquired* ------- | -------- *Present at birth* | *Cell mediated - T lymphocytes* * Same response for any pathogen* | *Helper* * Inflammatory response: WBC - Phagocytosis - Bleeding (flushes)* | *Cytotoxic/Killer* || *Suppressor* || *Humoral - B lymphocytes * | *Active* || *Natural* || *Artificial* #### Active * Memory cells - produced after exposure #### Passive * Materenally derived antibodies (colostrum) * Antiserum (passive) ## Biosecurity Prevention of disease causing agents entering or leaving place where they pose a risk. ## Barrier Nursing Physical barrier between infectious patient + Staff (PPE, seperate equipment) ## Reverse barrier nursing Isolation of susceptible aninmals (young/old/immune-suppressed) to protect them from sources of infection *Protective isolation/reverse isolation* ### Equipment * PPE * Coveralls * Aprons * Shoe covers * Hats * Face masks * Gloves * Food/water bowls * Utility trays * Cleaning Equipment * Disposable bedding * Clinical equiment * Needles * Syringes * Thermometer * Drip pump ### Isolation protocol * Barrier nursing * Footbaths at entrance * Shoes to be dipped on entrance/exit. * PPE put on + discarded. * WHO Handwash on entrance/exit. ## Canine Infectious Diseases **Disease/Infection** | **Agent** | ** Incubation Period** | **Affected Organs** | **Transmission** | **Zoonotic?** | **Vaccs** ------- | -------- | -------- | -------- | -------- | -------- | -------- Distemper | Virus | 7-21 days | Resp + GI | Inhalation | No | Yes Hepatitis | Virus | 5-10 days | Liver | Inhalation/Ingestion | No | Yes Parvo | Virus | 3-5 days | GI, Bone marrow | Ingestion of f+ | No | Yes Lepto | Bacteria | 5-7 days | Kidneys + Liver | Mm and skin abrasions | Yes | Yes Kennel cough | Bacterial | 5-7 days | Resp | Inhalation | No | Yes Rabies | Virus | 1 week to 6 months (3-8 weeks) | CNS | Saliva - skin wound | Yes - Fatal | Yes Salmonella | Bacteria | 2-3 days following stressful experience | GI | Ingestion of f+ | Yes | No ## Feline Infectious Diseases **Disease/Infection** | **Agent** | **Incubation Period** | **Affected Organs** | **Transmission** | **Zoonotic?** | **Vaccs?** ------- | -------- | -------- | -------- | -------- | -------- | -------- Panleucopenia | Virus | 2- 10 days | GI, Bone marrow | Body excretions | No | Yes Upper Resp. Disease | Virus/Bacteria | 1-10 days | Upper resp tract | Saliva/Discharge | No | Yes Leukemia | Virus | Months - Years | Immune system/neoplasia | Saliva | No | Yes Immunodeficiency | Virus | Variable | Immune system | Cat bites - Saliva | No | No Infectious Peritonitis | Virus | Variable | Severe inflammation of body tissues | Ingestion | No | No Infectious Anemia | Bacteria | N/A | RBC | Unknown | No | No Toxoplasmosis | Cocci | 3-10 days | Intestinal tract | Ingestion of T1 - Meat | Yes | No ## Canine Distemper (CDV) * Dogs + Ferrets are susceptible * Persists in environment 1-2 days. * Commonly seen in unvacc puppies 3-6 months * Shed from * Respiratory exudate * Urine * Faeces * Saliva * Vomit * Occular discharge. ### Clinical Signs * Depression * Pyrexia * Anorexia * Conjunctivitis * Rhinitis * Cough * Exudative pneumonia * VID * Neurological. ### Treatment * Isolation + Barrier nursing * IVFT * Broad spectrum antibiotics * Antiemetics * Anticonvulsants ### Diagnostics * Haematology + biochemistry * Thorax x-rays * CSF * Post mortem ## Hepatitis * Shed from all bodily secretions. * 10 days post infection, virus is spread in urine for at least 6 months. * Tonsils + lymph nodes -> liver ### Clinical Signs * Pyrexia * Depression * Anorexia * Vid * Shock * Hepatomegaly * Abdo pain * Patechial haemorrhages * Jaundice * Corneal oedeme * Neuro * Death ### Diagnostics * History * Bloods - Haem - Biochem - Clotting * Serological tests * Post mortem ### Treatment * IVFT * Analgesics * Occular topical steroid * Antimicrobials ## Panleucopenia * Feline parvo * Domestic + wild cats. ### Clinical Signs * Pyrexia * Depression * Vomiting * Anorexia * Diarrhea * Dehydration * Hypothermia * Ataxia * CNS tremors * Cerebellar hypoplasia * Retinal lesions * Abortion/Infertility ### Diagnostics * Bloods - Haem - Biochem * ELISA ### Treatment * IVFT * Antib's * Antiemectics ## Upper Respiratory ### Viral * Feline Herpesvirus Type I (FHV-1) * Feline Calicivines (FCV) ### Bacterial * Mycoplasma felis * Bordetella bronchiseptica * Chlamydia felis ### Signs: * Depression * Inappetance * Pyrexia * Conjunctivitis * Dyspnoea * Discharge * Sneezing * Coughing ## Parvo (CPV) * Survives in environment months - years * Incubation period of 7-14 days has been reported (is 3-5 days) ### Clinical Signs * Anorexia * Depression * Lethargy * V+ * HGE * Pyrexia * Shock * Dehydration * Hypothermia * Death ### Diagnostics * Bloods - Haem - Biochem * Faecal sample - CPV antigen - ELISA * Post mortem. ### Treatment * Isolation + barrier nursing * IVFT * Antiemetic * Nutrition * Antib's. ## Leukemia - *FeLV* ### Neoplastic FeLV ### Clinical Signs * Tachypnoea * Dyspnoea * Regurgitation * Horner's syndrome * Lethargy * Bleeding * Sepsis * Splenomegaly ### Diagnostics * Bloods - Haem - ELISA * Bone marrow cytology * FNA * X-rays/Scans ### Non-neoplastic * Anaemia * Platelet abnormalities * Leucocyte abnormalities * Immunosuppression * Infertility/abortions