Leptospirosis

General

Leptospirosis is a bacterial infection that can affect reproductive performance of sows and is also a threat to people or other pigs when leptospires are shed in the urine and from the reproductive tract into the surrounding environment.

The disease is caused by the bacteria species known as Leptospira. Four serovars are currently known to cause leptospirosis in Australian pigs. These belong to three of nine pathogenic species of Leptospira: L. interrogans serovars pomona and bratislava, L. fainei serovar hurstbridge and L. borgpetersenii serovar tarassovi.

Infection occurs in non-immune pigs when the bacteria enter the body via the nose, mouth, and eyes or breaks in skin. The bacteria multiply in the kidney and then are shed in the urine. Peak infection occurs in pigs 12-16 weeks old.

The disease is introduced into previously non-infected piggeries through urine of carrier pigs or occasionally rodents. Outbreaks are more serious in wet conditions eg. open drains or in outdoor herd situations, wet or poorly drained paddocks.

Clinical Signs

It can be difficult to visibly notice an infected pig in the growing herd. The only signs may be listlessness, inappetence and a mild scour that may last a couple of days. The most significant problem apart from the risks associated with human health is that to infected pregnant sows.

If pregnant sows become infected, they can abort or produce stillborn or weak piglets that often die soon after birth. Abortions generally occur in the last three weeks of pregnancy, but can be as early as the sixtieth day of pregnancy if susceptible pigs have received a high enough dose of the bacteria.

Diagnosis

Leptospirosis can be diagnosed by isolating leptospires from stillborn piglets or aborted foetuses. Chronic leptospirosis is a major cause of kidney inflammation leading to pale lesions on the kidneys. These can be observed at slaughter.

Treatment

 In feed medication with tetracyclines at 800 gm/tonne for 10-14 days is the main available option. Seek veterinary advice before implementing any program.

Control

Vaccinate selected gilts twice yearly 4-6 weeks apart then every six months. Vaccinating the breeding herd twice a year gives good protection however sometimes weaners need to be vaccinated. If leptospirosis is wide spread in the growing herd, give two vaccinations between 8-12 weeks followed by in-feed tetracyclines upon veterinary advice.

Other control measures include; controlling rats and mice to help prevent spread of the disease, reducing access to urine and wearing gloves when handling foetuses and membranes of aborting sows.