Farm animal diarrhoea Flashcards
3 factors that combine to cause calf diarrhoea
pathogens, environment and management, calf factors (immune status, stress)
Pathogens causing calf diarrhoea - 7
- E.coli
- Rotavirus
- Coronavirus
- Cryptosporidium
- Salmonella
- Mixed infections
- Coccidiosis
Significance of E.coli grown from faecal culture
Insignificant - all faecal cultures grow this. It is important to determine whether it is an enterotoxigenic type or not.- requires 2 factors
2 factors for ETEC
Adhesive fimbriae and enterotoxin (carried on plasmids)
3 types of E.coli infection
- Extraintestinal (colisepticaemia)
- Enteric (special strains, ETEC)
- Public health (rare, special strains, STEC)
Signs of ETEC - calves/piglets/lambs
Neonatal enteritis (1-3 weeks old) - seen when <5days
More common in young animals with poor colostrum intake
Diarrhoea (stunting of villi)
Often in conjunction with rotavirus
What are K88 and K99?
Types of fimbriae (cattle and pig respectively) that are enterotoxigenic. Also known as colonisation factors. Now called F4 and F5.
Structure of labile toxin (LT)
5 B subunits, 1 A subunit (A1 or A2)
Similar to cholera toxin
Attaches to brush border of SI cells.
LT causes a Gs subunit to malfunction causing increases in cAMP level, activation of Cl- channel, Na+ and H2O loss from tissue into lumen –>secretory diarrhoea. Metabolic acidosis, dehydration and electrolyte loss are sometimes fatal.
Effect of ST
Mechanism less well understood - types types STa and STb. STa raises intracellular GC (short-lived toxin, not immunogenic). STb - unknown action, non-immunogenic, difference aa sequence, porcine ETEC only.
How do you diagnose ETEC?
Show both toxin (or gene) and fimbriae (or gene)
Define STEC
Shiga-like toxin producing E.coli. Toxins are ST-1 and ST-2. Some diarrhoea and haemorrhagic colitis in calves. Previously called EHEC (enterohaemorrhagic)
Public health significance of STEC
Carriage by calves - beef animals
Contamination of beef - cooked foods
Very low does (10CFU) infects humans (heamorrhagic colitis and haemolytic uraemic syndrome causes renal failure)
How does STEC cause human disease?
Attaching and effacing lesion in gut (by the adhesion factor intimin), Shiga-like toxin is absorbed (causes vascular damage, oedema, thrombi). Causes thrombocytic thrombocytopaenic purpurea.
Diagnosis of STEC? 2
Culture and latex agglutination tests. n.b. cooking destroys the pathogen.
Clinical signs -rotavirus -5
- Calves aged 1-3 weeks
- high morbidity low mortality
- duodenum and jejunum affected - Causes malabsorption
- shed by cows and older calves - persists
- Often coupled with coronavirus infection
Clinical signs - coronavirus -5
- Slightly older calves (7-22, up to 28d)
- slightly higher mortality
- ileum, caecum and colon affected
- shed by cows and older cow
- persists in environment
Significance of the culture of salmonella = ?
Always significant. Reportable to the AHVLA because it is zoonotic. AB always indicated
Which animals are affected by salmonella? How?
Any age of animal
Systemic illness and pyrexia
What age do you see clinical signs in calves infected with cryptosporidium? What must you bear in mind?
5-14 days (n.b. PPP=2-7 days)
Signs - cryptosporidium
Lower SI/colon –> villous atrophy –> malabsorption
Often concurrent disease
Resistance develops
Signs - coccidiosis
Slightly older weaned calves (>3 weeks)
May –> blood stained faeces, tenesmus
May –> subclinical (poor growth rate and secondary infections as immunocompromised)
How do you diagnose infection?
Faecal sample NOT swab from healthy AND affected animals. Send to competent lab. Bacteriology, virus isolation AND typing are all needed. Don’t just look at faecal appearance!
List the ages of calves that are used as a guide to diagnose infection. 6
E,coli 3 weeks
List calf factors - 4
- Colostrum accesibility
- Dystocia
- Competition
- Dam - cow factors, uality of colostrum, down? allowed to suck?
