Farm animal diarrhoea Flashcards Preview

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Flashcards in Farm animal diarrhoea Deck (34):

3 factors that combine to cause calf diarrhoea

pathogens, environment and management, calf factors (immune status, stress)


Pathogens causing calf diarrhoea - 7

-Mixed infections


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
-Dam - cow factors, uality of colostrum, down? allowed to suck?


List environmental features that need consideration

Water/feed bucket location - inside/outside pens
Contact with other calves
Deep litter
Calf Milk Replacer (CMR) vs solid feed vs. water


How much Calf Milk Replacer (CMR) should you feed?

15-20% body weight per day in volume but follow packet instructions and check fat and protein levels.


3 classes of causes of growing animal/adolescent cattle diarrhoea, give examples

ENDOPARASITES - ostertagia (1/2), coccidia, fluke
NUTRITIONAL - rumen acidosis, copper deficiency
INFECTIOUS - salmonella, mucosal disease (BVD PI)


3 classes of causes of adult cattle diarrhoea, give examples

INFECTIOUS - MAP, salmonella, coronavirus (winter dystentery)
PARASITIC - fluke, ostertagia


What must be a routine part of dairy herd management?

Walk around farm and observe faecal consistency of different groups of cattle.


Clinical signs - MAP. Treatment? Zoonotic?

Clinical cases - severe diarrhoea and weight loss in adult cows. Infectious faeces.
No treatment or cure.
Potentially zoonotic - MAP may be involved in Crohn's disease in humans


How is MAP/Johne's contracted?

Usually acquired by youngstock (F/O route)
Takes at least 2 years to become clinical.
Subclinical disease hard to detect or identify with lab tests


3 main ways of preventing young animal infection. 3 other ways?

Preventing access to faeces of older animals/adults, infected colostrum (avoid pooled colostrum) or in utero.
-Test before buying in.
-Don't spread slurry
-Cull out or breed to beef


Diagnosis of MAP - how? Sensitivity vs specificty?

Blood test - ELISA
Low sensitivity but high specificity (positive is always a positive, negative is not always a negative). Many infected cows are not detected this way. A milk test is also available.
OTHER METHODS = ZN smear, PCR faecal, faecal culture, necropsy


How does MAP diagnosis differ between when you are screening for infected cows versus testing clinically infected cows?

Diagnosis is difficult when screening for infected cows. In clinically infected cows, tests have a much higher sensitivity.