Leptospirosis

 

Other names

In man infection with L. icterohaemorrhagica is called Weil's Disease

Causal agent

A very large family of bacteria present in all parts of the world. They belong to the spirochaete type of bacteria

There are five serovars and groups which are important to the pig: pomona, australis (bratislava) and tarassovi together with canicola, icterohaemorrhagicae and grippotyphosa

L. pomona

The most clinically important Leptosposis is L. pomona. However, L. pomona is not present in all countries.

Age group

Mainly the adults are affected with clinical signs. Note that non pig specific leptospira can infect any age group. For example jaundice due to L. icterohaemorrhagica can affect weaners as well as adults

Clinical signs

Acute

Anorexia, pyrexia and listlessness. Therefore very non-specific and tends to only affect individuals, on majority of farms these signs are missed.

With L. icterohaemorrhagica the animals can be very ill and jaundiced

Chronic

Abortions, stillbirths an the birth of weak pigs and other vague reproductive problems

 

Aborted piglets but note there are many causes of abortion in the pig Interstitial nephritis commonly associated the L. pomona Normal and jaundiced pig yellow.

Infectivity

 

The organism cannot withstand drying, but will live for a long time in wet conditions. Rodents can carry many leptospiral diseases

Post-mortem Lesions

Acute cases

The pathological findings can be very limited

Chronic

Mainly confined to the kidneys and consist of scattered small grey foci of a focal interstitial nephritis. Note many other diseases can cause identical findings and leptospira can be isolated from kidneys with no pathological damage

Diagnosis

 

Can be difficult

Serology

Antibody positive titres can be very transient, lasting less than a month. Many serological tests are inconclusive at 1/100

Demonstration

The demonstration of Leptospiras in tissues can be achieved but is not easy

Culture

Difficult and time consuming. Leptospira are also normal in healthy animals

Treatment

Individuals

Streptomycin at 25mg/kg is effective

Group

In-feed medication with 800g of chlortetracycline per tonne of feed for 6 weeks.

Vaccines

Vaccine only protective for 3 months. Vaccines are not available in all coutries.

Control

Rodent control and biosecurity

Manage wallows to allow the wallow to dry out during the summer.

Disinfect water supplies

Routine treatment of boars especially at AI studs

Common differentials

 

Other reproductive problems. Poor stockmanship and breeding routines

Zoonotic

Various leptospiral species cause problems in humans. Some are potentially fatal.