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(218) Leptospira are long slender spiral-shaped bacteria, found in most mammalian host species. Over 160 serotypes are known, generally called serovars, with cross infections occurring between some species. Each serotype has one or more (usually only two or three) reservoir hosts which multiply up the type and maintain it. A serotype can remain as a life-long infection in its reservoir host.

The pig is a reservoir host for Leptospira pomona, L. tarassovi, L. bratislava and L. muenchen, the last two being very closely related. It is not a reservoir host for L. icterohaemorrhagiae but it can be infected from rats urine and become ill. It can also become infected by other serotypes from other animals urine, for example L. canicola from dogs and L. hardjo from cattle but the infections are subclinical and do not result in disease. The pig is then an incidental host i.e. does not perpetuate the infection and is only responsible for minimal spread.

L. pomona causes important reproductive problems in female breeding pigs spreading slowly through the herd. It remains in the herd permanently unless steps are taken to eradicate it. It is not in the UK or Ireland and seems to have disappeared from Western Europe but is widespread throughout the rest of the pig rearing world. In America the skunk is an alternative reservoir host.

L. tarassovi causes a similar syndrome (i.e. a collection of signs and lesions) to L. pomona but tends to be milder and to spread more slowly. It is found in Eastern Europe and the Antipodes. It is thought that some wild animals are also reservoir hosts.

The pig is also a reservoir host for certain subtypes of L. bratislava and L. muenchen which are widespread throughout the pigs of the world. They causes a different syndrome to L. pomona and L. tarassovi and affect mainly pregnant gilts and second litter females because they will not previously have encountered it.

Once these organisms are introduced into a herd the pigs become permanent carriers with infection of the kidneys and intermittent excretion of the organism into the urine. L. bratislava/muenchen also permanently inhabit the fallopian tube of sows and the reproductive organs of boars and are spread in semen.

Infection can enter the herd in one of three ways:

  1. Introduction of infected gilts and boars.
  2. Infection brought into the herd by other animals.
  3. Exposure of the herd to indirect sources of contamination, e.g.: contaminated water.
A herd can also be contaminated by L. bratislava/muenchen by AI if no antibiotics are used in the semen. Unless very stringent precautions are taken most herds become exposed at some stage to L. bratislava/muenchen. L. pomona and L. tarassovi are more easily kept out.

Leptospirosis can be a very difficult disease to diagnose because pigs are often infected but there are no clinical signs to be seen. Thus if you carry out a serological test in your herd and the result is positive, for example to L. bratislava, this does not necessarily mean you have disease - only that the animal has been infected and responded by producing antibodies. If you carry out a serological test with positive results for L. pomona, this may be a cross reaction to other non pig serotypes in the same group.

Conversely, if you have an infertility problem that clinically suggests leptospira as the cause, then such test results would support a diagnosis of disease if there were rising titres in the serum of the affected sows. However this may not be the case because pregnant females seroconvert early in the infection and by the time they abort or show symptoms the serum levels may be falling.

Methods of spread within the herd are as follows:

  • Infection is by mouth, through the mucous membranes.
  • Most leptospira are inhabitants of the kidney and found in urine.
  • Introduction and spread within the herd can occur by various forms of wildlife.
  • Introduction and spread within a herd can occur through the introduction of carrier boars and gilts.
  • Pig to pig transmission via urine is common.
  • Venereal infection is commonplace particularly with L. bratislava/muenchen.
  • Contaminated water, floor surfaces , pools and streams.
  • Wallows used in outdoor production if there are pools of fresh water.
The most common type outside the UK, Ireland and Western Europe is L. pomona. The most widespread in pigs world-wide is L. bratislava/muenchen. All leptospira require moisture, not only for indirect transmission, but also to survive. Desiccation kills them in 48 hours. When they invade the pig for the first time, there is rapid multiplication, and antibodies become evident 5-10 days later in the blood. Titres may rise as high as 1:1000, but they gradually decline to a low point or even become negative although the animal may still carry the bacteria and excrete them.

Leptospira may become localised in the uterus during pregnancy, causing either abortions or increases in stillborn piglets. L. bratislava may persist in the oviduct and uterus of non pregnant sows, and in the genital tracts of boars. This may be an important medium for the maintenance of infection in the herd and be responsible for sows failing to conceive.

Clinical signs
In acute outbreaks inappetence and depression may be observed but chronic low grade disease is more common with abortions, stillbirths and an increase in poor, non-viable pigs. If abortions in a herd are more than 1% then investigations for leptospirosis should be considered. A reduction in farrowing rates and numbers of live pigs born per sow is also an associated factor particularly with L. bratislava infection.

It is important to appreciate that many infections are subclinical but the organisms may persist in the kidneys and reproduction tracts to cause problems later.

Signs associated with acute L. bratislava disease:

  • Repeat breeders are common particularly in first and to some extent second pregnancy gilts.
  • This often follows embryo loss and there may be copious vaginal discharges.
  • Late term abortions.
  • An increase in premature piglets.
  • An increase in stillbirths.
  • Mixed litters of live poor pigs and dead piglets at birth.
  • An increase in mummified pigs.
  • An increase in repeat breeding animals.
  • Often there is a two year cycle of disease.
  • Reproductive failure occurs in second litter females, rather than gilts following their introduction to older carrier boars.
  • Disease is less common in older animals.
  • In long standing carrier herds disease can be difficult to recognise.
This is carried out by assessing the antibody levels in a cross section of breeding females and the isolation of the organism from diseased tissues. The micro-agglutination test is carried out on serum, and recently affected animals will show titres of up to 1:1000 or more. At the onset of clinical signs a blood sample should be taken and a further one, two weeks later. If the second sample shows a rise in antibody levels at least two fold, this would be indicative of leptospira involvement. Leptospira are difficult organisms to grow, and take a long period of time. L. bratislava/muenchen are even more difficult to grow and very few laboratories can culture them. There is however, a method of detecting leptospira under the microscope using the fluorescent antibody test (FAT). Because of the difficulty of distinguishing between sub-clinical infection and infection with disease, an appraisal of the following will help:
  1. Records. Study the levels of abortions, repeats, stillbirths, week piglets and the age of occurrence in sows and gilts.
  2. Study the clinical picture.
  3. Eliminate other diseases.
  4. Eliminate non infectious causes of infertility.
  5. Blood sample suspicious animals and repeat 2-3 weeks later. Look for rising antibody titres e.g. 1st sample result 1:100, 2nd result 1:800. This would confirm active infection and indicate probable involvement.
  6. Blood sample ten females that have a history of infertility.
  7. In chronic disease however, the significance of titre levels are very difficult to assess.
  8. Test the aborted foetuses, urine or kidneys and fallopian tubes of slaughtered gilts by the FAT.
  9. Test thoracic fluid from stillborn pigs for the presence of antibody.
Similar diseases
The symptoms of leptospirosis can be mistaken for other causes of infertility including:
  • Chronic PRRS.
  • Endometritis.
  • Non infectious causes.
  • Summer infertility.
  • Management failures
A study of Fig.6-1 and chapter 5 will help in differentiating.


  • Medicate the feed with tetracycline's, either oxytetracycline or chlortetracycline at levels of 800g/tonne. Feed for a period of three weeks followed by a further course six weeks later, and repeat this for four treatment periods.
  • An initial three week course of 800g of tetracycline followed by a further eight week course at 400g.
  • Strategic medication. Where there is a history of periodic infertility, in-feed medication can be targeted just prior to the expected time of disease.
  • Inject sows at weaning time with streptomycin if available at 25mg/kg. Boars should be treated with this drug once every six weeks. Alternatively semi-synthetic penicillins could be used.
  • Introduce antibiotic into the anterior vagina post-service. This is the same procedure to that described under vaginal discharges, and involves the use of an AI catheter and the deposition of antibiotic into the anterior vagina 6-18 hours after the last mating. Ampicillin, amoxycillin, or penicillin/dihydrostreptomycin could be used. (See chapter 15). Discuss with your veterinarian.
Management control and prevention
  • Control by vaccination is reasonably effective and in many countries vaccines are available that contain five or six different types of leptospira. Alternatively, where vaccines are not available, it is necessary to use antibiotic therapy.
  • Whilst it can be difficult to prevent L. bratislava/muenchen from infecting the herd, nevertheless the more serious types such as L. pomona and L. tarassovi can be kept out of the herd by careful isolation of incoming stock, serological testing, veterinary liaison and a knowledge of the source herd.
  • Once leptospira are active and present in the herd, hygiene, the constant removal of urine and good management become important methods of control. In outdoor herds, wallows could become sources of contamination especially if there are pools of fresh urine. The most effective method of control is to provide two wallows per paddock and use an electric fence which by movement will allow each to dry out and rest alternately.
  • In indoor housing, poor concrete surfaces that allow the collection of urine and water are ideal sources for maintaining high levels of infection.
  • If the sow is only exposed to low numbers of organisms, infection probably takes place with little disease.
  • Make sure your diagnosis of disease is a correct one.
  • Check the serology of your herd. Do not buy in what you don't have.
  • Check your sources of boars and gilts.
  • Keep rodents under control.
  • Provide well drained concrete surfaces particularly in defecating areas and boar pens.
  • Remove slurry regularly.
  • Identify problem parities and strategically medicate.
  • Vaccinate if a vaccine is available.

  • This can be done but it is unreliable and is probably contraindicated for L. bratislava.

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