Equine infectious GI diseases Flashcards
When referring to an isolation facility a veterinarian must have established 2 of which 3 clinical signs?
- Acute diarrhoea
- Fever: above 38.5 degrees
- Low white blood cell count
Describe some features of salmonella bacteria
Gram negative Motile Bacillus Modified flagella and pili Facultative anaerobe Facultative intracellular
What do Salmonella Virulence Plasmids allow for?
Intracellular growth
Serum resistance
Cellular invasion
Which 3 Exotoxins that all result in diarrhoea when infected with Salmonella?
- cAMP
- Cytotoxin
- Phospholipase A
What are some host risk factors associated with Salmonella?
Antibiotic treatment General anaesthesia Transport Hospitalisation Surgery Feed withdrawal/change Stress
Describe the hosts response to a salmonella infection
- Bacteria are opportunistic so need to invade cells for a response
- Lipopolysaccharide endotoxin triggers neutrophil inflammatory cascade
- Persistence of facultative intracellular pathogen in macrophages maintains inflammatory reaction
- Inflammation and tissue necrosis lead to leakage of protein and fluid = diarrhoea
- Diarrhoea dilutes Salmonella and toxins and removes them from body
What is the main cause of variable mortality in a salmonella infection?
- Diarrhoea and endotoxaemia leads to severe shock and cardio-circulatory collapse
- If hydration can be maintained diarrhoea and inflammatory response eliminates infection and the mucosa heals
What causes endotoxemia?
Endotoxins are released when bacteria die, and then dissociated endotoxins are able to cross the gastro-intestinal barrier to end up in the bloodstream
How can salmonella be spread?
- survives in damp soil for up to 9 months
- spread by direct contact
- water and feed contaminated with faecal material
- host stress increases susceptibility
What are some stable (isolation) control methods for the prevention of Salmonella?
- Horses in isolation mucked out last to avoid faecal contamination
- Soiled bedding and feed from isolated cases should be bagged and disposed of as clinical waste
- Stable should be completely disinfected when a patient is discharged
- The stable should then be swabbed for bacterial culture and then left empty to dry completely
Once a horse has been placed into isolation for Salmonella, protocol must remain in place until when?
Until 5 faecal cultures for salmonella are reported back as negative
Describe some features of Clostridium bacteria
Saprophytic Part of normal intestinal flora Gram positive Endospore forming Bacilli Obligate anaerobes Only some strains are motile
Which strain of Clostridium is most common in horses?
C.perfringens type A
If Clostridium is a part of the hosts normal flora how does it become infective?
Requires host ‘stress’ or intestinal flora change
What are some stress factors that could cause a Clostridium infection?
- Intercurrent infections
- Extreme temperatures
- Dehydration
- Transportation
- Sudden diet change
- Antibiotic therapy
- General anesthesia
Does clostridium have high or low mortality rates?
High
How is clostridium bacteria adapted to surviving in an environment?
- Spore forming
- Resistant to heat and cold
- Resistant to many disinfectants
How can clostridium be prevented and managed?
- Avoid crowding and stress
- Avoid rapid changes in diet
- Quarantine affected animals
- Regular hand washing/good hygiene
On a rotavirus what is the target antigen of a neutralising antibody response?
VP4 protein
How is rotavirus infected and where in the body does it target?
- Ingested
- Infects the absorptive epithelium of the small intestine
What are the consequences of damage to the small intestine due to rotavirus?
Damage and loss of cells in villi leads to villus atrophy, resulting in poor nutrient absorption and osmotic diarrhoea
Which host response neutralizes Rotavirus?
Humoural response
What factors make a host more susceptible to Rotavirus?
Age less than 2 months (ie naïve immune status) Intercurrent infections Extreme temperature Poor food and water sanitation Overcrowding Transportation
How does Rotavirus interact with the environment?
- Spread by direct contact
- Water and feed contamination
- Survives for up to 9 months in the environment
- Resistant to disinfectant
How can rotavirus be controlled and prevented?
- Ensure clean food and water sources
- Avoid crowing foals together
- Clean foal bedding frequently
- Isolate infected
- Vaccinate for Equine Rotavirus: Mare in 8th, 9th& 10th months of EACH pregnancy
