Leptospirosis - Cattle and Sheep

Description

Leptospirosis is an economically significant zoonotic disease caused by the bacteria leptospira interrogans. Disease in cattle is usually due to L.pomona or L.hardjo;L. interrogans serovar hardjo is host-adapted to cattle, whereas L.pomona is non-host specific. Clinical disease is rarely seen in sheep, they are less susceptible to the bacterium but may act as non-symptomatic carriers.

In cattle leptospirosis is seen in 3 forms, acute, subacute and chronic. The acute disease is seen most frequently in calves, causing pyrexia, haemoglobinurea, jaundice, anorexia, uraemia due to renal damage and death. Acute disease in susceptible heifers, is seen as fever, lethargy, agalactia of all quarters; abortion and stillbirth may also occur. The subacute form results in clinical signs similar to those of the acute form, in a less severe form. The main signs of the chronic or enzootic form are infertility, especially in the heifers, and abortions.

In the rare cases affecting sheep, infection results in an acute syndrome in lambs, or abortion and agalactia in ewes.

Signalment

Risk factors include access to rivers and watercourses, rodent infestation, buying in stock and using a bull instead of AI. Cograzing sheep with cattle can result in disease in cattle as sheep can act as non-symptomatic carriers.

Diagnosis

Clinical Signs

Acute syndrome:

• Pyrexia
• Anorexia
• Dyspnoea
• Hymolytic anaemia
• Icterus
• Haemoglobinuria

Enzootic/chronic form:

• Abortion
• Infertility
• Milk drop

Laboratory Tests

Diagnosed by rising antibody titre in paired serum samples

Treatment

Urinary excretion can be reduced by administering dihydrostreptomycin or amoxycillin

Incactivated vaccines are of questionable efficacy

References

• Divers, T.J. and Peek, S.F. (2008) Rebhun's diseases of dairy cattle Elsevier Health Scieneces
• Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition) Merial
• Radostits, O.M, Arundel, J.H, and Gay, C.C. (2000) Veterinary Medicine: a textbook of the diseases of cattle, sheep, pigs, goats and horses Elsevier Health Sciences