Leptospirosis - Pigs

Description

Leptospirosis is an infective disease caused by the bacteria Leptospira. There are a number of serovars of the bacteria which vary in their pathogenesis and host specificity. L.bratislava and L.pomona are both host adapted to swine and are the most common cause of clinical leptospirosis in pigs. Other serovars which are host adapted to other species can also cause disease in pigs: L.icterohaemorrhagiae transmitted by rats, L.canicola by dogs, L.grippotyphosa by wildlife and rarely L.hardjo by cattle. Transmission is via urine of infected animals, persistence in the environment relies on soil moisture and water ways. Venereal transmission from carrier boars and sows is also responsible for infection and maintenance of the disease

Signalment

Leptospirosis has a worldwide distribution; it is more prevalent in warm wet climates. The incidence of disease depends on the serovar involved.

Diagnosis

Clinical Signs

The most common clinical presentation is the chronic form which results in abortion 2-4 weeks before term, still births and weak piglets which die shortly after birth are also seen.

• Late term abortion
• Still birth
• Infertility

An acute syndrome has been described in piglets but is very rare, clinical signs are outlined below:

• Pyrexia
• Dyspnoea
• Haemoglobinuria
• Anorexia
• Icterus
• Anaemia

Some serovars can become endemic in a herd causing minimal disease but presenting a major zoonotic concern.

Diagnosis is made on a combination of clinical signs and identification of the orgainism by laboratory testing.

Laboratory Tests

Paired serum samples showing a positive rise in antibody titre can be used in some cases for confirmation of infection. The organism can be isolated by culture in a special medium, of it can be viewed under dark field microscopy.

Treatment

Treatment with antibiotics such as oxytetracycline, enrofloxacin and ampicillin are effective for chronic cases. Early treatment for acute cases with antibiotics may be successful; a blood transfusion may also be needed if anaemia is severe. In an outbreak the whole herd should be treated with appropriate antibiotics to reduce shedding of the organism in the urine. Depopulation and disinfection of the premises may ne necessary in some cases.
A vaccine exists in the USA but is not available in the UK; the protection provided is short lived, it minimises but does not eliminate clinical disease in all cases.

References

• Cowart, R.P. and Casteel, S.W. (2001) An Outline of Swine diseases: a handbook Wiley-Blackwell
• Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition) Merial
• Straw, B.E. and Taylor, D.J. (2006) Disease of Swine Wiley-Blackwell