Calf Scour

Question 1

Name the infectious agents which cause scour in calves

Answer 1

Salmonella (dublin & typhimurium), E. coli (ETEC), Cryptosporidium, Coccidiosis, Rotavirus, Coronavirus

Question 2

Describe the pathogenesis of ETEC

Answer 2

Calves - age

Question 3

Why is E. coli scour not seen in calves >5d old?

Answer 3

Abomasum becomes sufficently acidic to kill E. coli before they reach the SI and cause disease

Question 4

What are the clinical signs of ETEC scour?

Answer 4

Profuse, foul smelling d+
Yellow
\+/- blood in scour
\+/- pyrexia
Wet mouth
Distended, watery abdomen

Question 5

Describe the pathogenesis of Salmonella

Answer 5

Age

Question 6

What are the clinical signs of Salmonella scour?

Answer 6

\+/- blood in scour
Pyrexia
Septicaemia
Vascular necrosis
Herd level - adult scour, abortion

Question 7

Describe the pathogenesis of rotavirus/coronavirus

Answer 7

Age 5-21d - peaks at 10d then immune after 21d

1. Invades enterocytes
2. Replicates within then ruptures cells causing release of enterotoxin
3. Villi shrink = decreased absorptive SA
4. Hyperplasia of crypts in response to loss of villi
5. Excess nutrients in lumen = osmotic d+

Question 8

What are the clinical signs of rotavirus/coronavirus scour?

Answer 8

Profuse d+
White scour
Quickly become dehydrated
*can be confused with nutiritonal scour
Coronavirus - winter dysentery and respiratory disease in adults

Question 9

Describe the pathogenesis of Crypto

Answer 9

Calves - age 1-3 wks, lambs - age 2-20d

Causes villous atrophy and crypt hyperplasia

Question 10

What are the clinical signs of crypto?

Answer 10

Profuse watery d+
Quickly become dehydrated
Less severe systemic signs

Question 11

Describe the pathogenesis of cocci

Answer 11

Age 3 wks - 3 months
Causes rupture of enterocytes
Malabsorption and osmotic d+

Question 12

What are the clinical signs of cocci scour?

Answer 12

Black/bloody scour
Abdominal pain
Tenesmus
Walk with tail up

Question 13

How is the cause of scour diagnosed?

Answer 13

CS
Calf-side ELISA - viruses, E. coli, crypto
PM

Question 14

How is scour treated?

Answer 14

Ab - systemically unwell or mucous/blood in d+
NSAID - for analgesia and to reduce inflammation
Halocur (Halofuginone) - reduce shedding of crypto
Cocci tx - Decoquinate (coccidiostat), Diclazuril (tx and px in lambs, control in calves), Toltrazunil (px CS and reduces shedding)

Question 15

Describe the lifecycle of crypto/cocci

Answer 15

1. Host ingests oocyst
2. Sporozoites hatch in SI and burrow into mucosa
3. Form a trophozoite in extracytoplasmic vacuole
4. Reproduce asexually to form 8 merozoites
5. Merozoites hatch, enter other cells and reproduce asexually to form gametes
6. Gametes fuse and lay down a cyst wall to become an oocyst
7. Thin walled oocysts lyse and cause autoimmunity
8. Thick walled oocysts excreted in faeces and are infective

Question 16

What are the consequences of scour?

Answer 16

Decreased organ perfusion and azotaemia
Electrolyte loss
Metabolic acidosis

Question 17

How does scour cause a metabolic acidosis?

Answer 17

Bicarb lost in lumen means acid in bood can’t be neutralised and lactic acid increases due to shock
CHO can’t be digested so D-lactate increases which casues CS
To counteract this, the body exchanges H+ for luminal K+ which causes hyperkalaemia, cardiac arrhythmia and death

Question 18

Describe the fluid therapy regimen for animals with metabolic acidosis

Answer 18

9% dehydrated + mod/severe acidosis - IVT + bicarb

Mild acidosis = lactated/acetate fluid
Moderate = lactated/acetate + 15g bicarb
Severe = lactated/acetate + 35g bicarb

Spike with glucose for E
if unsure whether acidotic DO NOT give bicarb