Equine infectious GI diseases

Question 1

When referring to an isolation facility a veterinarian must have established 2 of which 3 clinical signs?

Answer 1

• Acute diarrhoea
• Fever: above 38.5 degrees
• Low white blood cell count

Question 2

Describe some features of salmonella bacteria

Answer 2

Gram negative
Motile
Bacillus 
Modified flagella and pili
Facultative anaerobe 
Facultative intracellular

Question 3

What do Salmonella Virulence Plasmids allow for?

Answer 3

Intracellular growth
Serum resistance
Cellular invasion

Question 4

Which 3 Exotoxins that all result in diarrhoea when infected with Salmonella?

Answer 4

• cAMP
• Cytotoxin
• Phospholipase A

Question 5

What are some host risk factors associated with Salmonella?

Answer 5

Antibiotic treatment
General anaesthesia 
Transport
Hospitalisation
Surgery
Feed withdrawal/change
Stress

Question 6

Describe the hosts response to a salmonella infection

Answer 6

• 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

Question 7

What is the main cause of variable mortality in a salmonella infection?

Answer 7

• 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

Question 8

What causes endotoxemia?

Answer 8

Endotoxins are released when bacteria die, and then dissociated endotoxins are able to cross the gastro-intestinal barrier to end up in the bloodstream

Question 9

How can salmonella be spread?

Answer 9

• survives in damp soil for up to 9 months
• spread by direct contact
• water and feed contaminated with faecal material
• host stress increases susceptibility

Question 10

What are some stable (isolation) control methods for the prevention of Salmonella?

Answer 10

• 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

Question 11

Once a horse has been placed into isolation for Salmonella, protocol must remain in place until when?

Answer 11

Until 5 faecal cultures for salmonella are reported back as negative

Question 12

Describe some features of Clostridium bacteria

Answer 12

Saprophytic 
Part of normal intestinal flora
Gram positive
Endospore forming 
Bacilli
Obligate anaerobes
Only some strains are motile

Question 13

Which strain of Clostridium is most common in horses?

Answer 13

C.perfringens type A

Question 14

If Clostridium is a part of the hosts normal flora how does it become infective?

Answer 14

Requires host ‘stress’ or intestinal flora change

Question 15

What are some stress factors that could cause a Clostridium infection?

Answer 15

• Intercurrent infections
• Extreme temperatures
• Dehydration
• Transportation
• Sudden diet change
• Antibiotic therapy
• General anesthesia

Question 16

Does clostridium have high or low mortality rates?

Answer 16

High

Question 17

How is clostridium bacteria adapted to surviving in an environment?

Answer 17

• Spore forming
• Resistant to heat and cold
• Resistant to many disinfectants

Question 18

How can clostridium be prevented and managed?

Answer 18

• Avoid crowding and stress
• Avoid rapid changes in diet
• Quarantine affected animals
• Regular hand washing/good hygiene

Question 19

On a rotavirus what is the target antigen of a neutralising antibody response?

Answer 19

VP4 protein

Question 20

How is rotavirus infected and where in the body does it target?

Answer 20

• Ingested

- Infects the absorptive epithelium of the small intestine

Question 21

What are the consequences of damage to the small intestine due to rotavirus?

Answer 21

Damage and loss of cells in villi leads to villus atrophy, resulting in poor nutrient absorption and osmotic diarrhoea

Question 22

Which host response neutralizes Rotavirus?

Answer 22

Humoural response

Question 23

What factors make a host more susceptible to Rotavirus?

Answer 23

Age less than 2 months (ie naïve immune status)
Intercurrent infections
Extreme temperature
Poor food and water sanitation
Overcrowding
Transportation

Question 24

How does Rotavirus interact with the environment?

Answer 24

• Spread by direct contact
• Water and feed contamination
• Survives for up to 9 months in the environment
• Resistant to disinfectant

Question 25

How can rotavirus be controlled and prevented?

Answer 25

• 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