ID - Equine Infectious Gastrointestinal Diseases Flashcards
Name 5 major causes of infectious equine gastrointestinal disease
Salmonella - acute fibrinonecrotic colitis
Clostridium perfringens & clostridium difficile
Acute necrotic colitis & dysentery (Colitis X)
Rotavirus - acute enterocolitis in foals
Ehrlichia risticii - Potomac Horse Fever (acute colitis)
What is the policy for a horse with suspected infectious colitis?
Policy is not to admit any horse with a high suspicion of having infectious colitis in a hospital without an appropriate isolation facility
What 3 clinical signs is a referring veterinarian looking for when deciding if a case needs full isolation (it needs 2 out of 3 symptoms for iso)?
Acute diarrhoea
Fever (temperature over 38.5 degrees C)
Low white blood cell count (less than 4.0 x10^9 cells/L)
How varied is the salmonella enterica species?
6 subspecies esp salmonella enterica subsp enterica
Over 2000 serovars esp. typhimurium
Others include Newport, Anatum, and Agona
What is the significant difference between host specific and non-host specific salmonella enterica?
Host specific causes more systemic disease
What disease could be described by the following?
- gram -ve motile bacillus
- modified flagellae & pilli used for plasmid exchange
- facultative anaerobe
- facultative intracellular - the most pathogenic strains are best at this
- wide range of antibiotic resistance
Salmonella enterocolitis
Name 4 different ways in which Salmonella interacts with the hosts
Adhesion molecules - 3 different types (species selectivity).
Invasion genes - encode proteins that cause ruffles in enterocyte membrane and Salmonellae become interiorised.
Salmonella Virulence Plasmids - allow for intracellular growth, serum resistance, and cellular invasion.
3 exotoxins that all result in diarrhoea - cAMP, Cytotoxin, Phospholipase A activity
Describe the host response to Salmonella
Without invasion there is no response (opportunistic)
Lipopolysaccharide (endotoxin) triggers massive neutrophil dominated inflammatory cascade
LPS > macrophage > IL-1 & TNF > Neutrophil activation
Persistance of facultative intracellular pathogen in macrophages maintains inflammatory response
Inflammation and tissue necrosis lead to leakage of protein and fluid > diarrhoea
What disease does the following symptoms describe?
Angry purple looking mucous membrane, saliva tacky due to dehydration, purple rings visible?
Salmonella
How can salmonella lead to severe disease or even death?
Diarrhoea dilutes salmonella and toxins and removes them from the body. Diarrhoea and endotoxaemia leads to severe shock and cardio-circulatory collapse. Variable mortality (related to virulence) - if hydration can be maintained diarrhoea and inflammatory response eliminates infection and mucosa heals - otherwise...
How long can salmonella survive in damp soil?
9 months
How is salmonella transmitted?
- Contagious spread by direct contact & fomites
- Water & feed contaminated with faecal material
- Recovered animals may shed for weeks or months
- Host stress increases susceptibility and lowers required spore dose
- most frequently reported outbreaks are amongst hospitalised patients
How can you personally help prevent and control the spread of salmonella?
- Washing hands after working with horse and before eating/drinking (pay particular attention to under the nails and use antibacterial soap)
- Gloves, shoe covers and outer protective clothing (disposable overalls) must be put on before entering the stable and removed upon leaving it. Boots must also be dipped before leaving the isolation area
- Hands should be washed immediately after leaving the stable with antibacterial soap
How can you prevent and control the spread of salmonella at the stable?
- Muck out horses in isolation last
- Bag and dispose of soiled bedding in feed as clinical waste. Don’t compost
- After the horse has been discharged empty stable and dispose of all bedding, waste feed and PPE as clinical waste
- Rinse equipment to remove visible contamination, then clean with bleach (hypochlorite) or Virkon and then dried completely
- Rinse stable with detergent to remove visible contamination, then clean with bleach (0.5%) and leave for 10, then rinse and clean with Virkon S (1%) and leave for 10 then rinse
- stable should be swabbed for bacterial culture then left to dry (if culture negative stable can be used again, if positive clean again)
How long does a horse with salmonella need to stay in isolation?
Once isolation protocol is in place it must remian until either all 5 faecal cultures for salmonella (q12 - 24 hours) are reported back as negative, or the horse goes home (culture not PCR as PCR often too sensitive - would isolate more cases than necessary)
