Leptospirosis is the general term applied to diseases of animals and humans caused by varieties of certain spiral-shaped bacteria known as Leptospira. Many such varieties are harboured by a wide range of animals, and all of them are capable of causing illness in humans.
Leptospira pomona and Leptospira hardio are particularly important in livestock, with Leptospira tarassovi of lesser importance. Leptospira copenhagenican severely affect animals, particularly dogs, and humans.
Symptoms and recognition of leptospirosis
Redwater in cattle, and particularly in calves, strongly suggests infection with Leptospira pomona. Calves as young as two or three weeks of age can become affected.
Symptoms develop suddenly and include deep red urine, decreased activity, rapid breathing, anaemia and pale, slightly yellow membranes lining the mouth and vagina. Young calves still on the bucket may be off-colour at one feeding and dead before the next. Not all severely affected animals die, however, and the symptoms of redwater may pass after a few days.
Leptospirosis with redwater can occur in adult cattle, but these cases are less common and symptoms are usually milder and deaths are rare. Similar symptoms can arise from quite different causes such as overgrazing on rape, turnips and choumollier, or accidental access to onions and onion crops.
A peculiar type of mastitis is another distinctive form of leptospirosis. There is a sudden onset of slackness of the whole udder and abnormal milk in all four quarters. It may affect many cows in a herd at one time. Leptospira hardjois a frequent cause, with the milk being yellowish, and sometimes of uneven consistency. Leptospira pomona may also produce a similar condition but the milk may be brownish, or contain a little blood.
With L. pomona infection redwater occasionally accompanies this unusual mastitis condition, and may produce severe sickness. Otherwise there is little general sickness. Milk returns to its normal appearance after a few days, but sometimes the cow fails to reach her expected level of production for that season.
Cows may abort in late pregnancy due to either Leptospira pomona or Leptospira hardio. Abortion may occur without, or some weeks after, other symptoms of leptospirosis.
Leptospirosis may also add indirectly to other problems in cattle, such as decreased milk production, increased susceptibility to the usual forms of mastitis, and poorer fertility. It can also be responsible for losses of condition as a result of persistent kidney damage.
Leptospirosis in pigs is sometimes important as a cause of abortions, still-births and poor survival of newborn piglets. There may be some cases of animals failing to thrive because of persistent kidney damage.
Leptospira pomona is most important; Leptospira tarassovi may also cause similar symptoms.
In sheep, leptospirosis is rare, but redwater resulting from infection with Leptospira pomona can occur.
Horses may be infected with Leptospira pomona, leading to severe sickness, redwater in foals, and abortion. There may also be a connection between Leptospira pomona infection and a persistent eye condition called periodic ophthalmia.
Nature and transmission of leptospirosis
Exposure of livestock to leptospira organisms is much wider than the occurrence of the disease would suggest. Livestock pick up infection by contact with pasture or water contaminated by the urine of infected livestock or wild animals.
In warm, moist conditions the organisms may survive and cause infection for several weeks, so that under suitable conditions, many livestock are almost continually exposed for long periods.
The organism enters the body through intact membranes such as those of the eyes or inside the nose and through the skin if it happens to be broken. Swallowing is not a recognised means of infection.
Many animals suffer only mild or unapparent signs on their first infection. Recovered animals become resistant to further infection by similar leptospiral organism but for periods of up to several months, they may pass leptospiral organisms in their urine, adding to the reservoir of environmental infection.
Many factors affect the complex pattern of exposure and resistance, producing widely varying levels of infection and symptoms.
The unusual mastitis – discussed earlier is still not well understood. Udder reaction and damage associated with it, however, produce positive reactions on the rapid mastitis test.
It is suspected that leptospiral mastitis paves the way for more familiar mastitis infections. However, milk is unfavourable for survival of leptospiral organisms, so milk, unlike urine, is not important in contaminating the environment.
Abortion during later stages of pregnancy is caused by leptospiral organisms multiplying after first entering the body. When they reach the placenta and the unborn calf they multiply further in that site, to cause sufficient damage for abortion to follow.
Thus, one may see the unusual mastitis or redwater some weeks before the cow aborts. On the other hand, the initial infection may produce such mild results that nothing unusual is seen before the abortion.
Diagnosis of leptospirosis
The sudden appearance of acute sickness associated with redwater in calves, and perhaps older cattle, is sufficient to provide a strong suspicion of Leptospira pomona infection, although other causes of redwater, such as overgrazing on fodder crops, must be taken into account.
The sudden appearance of a slack udder with abnormal milk in all four quarters points directly towards Leptospira hardjo infection.
Laboratory examination of urine and other specimens may be made to confirm the infection. Infected animals produce antibodies to the leptospira organisms and these antibodies can be detected by testing blood samples.
Sometimes, positive results on the first test can only be interpreted as evidence that cattle were exposed to infection sometime in the past. However, if rising antibody levels are found on further tests, they indicate recent infection.
When the first suggestion of leptospirosis in cattle or pigs turns out to be abortion late in pregnancy, then without laboratory assistance there is no way of confirming infection.
In cattle, abortions come under scrutiny on account of the national brucellosis eradication campaign. An interesting point here is that as leptospiral abortion usually occurs quite some weeks after infection, antibody levels could be falling rather than rising at that time.
Similar considerations apply to the testing of sows following loss of their piglets from abortion, stillbirth or lack of vitality after birth.
Treatment and control of leptospirosis
Treatment of cattle severely affected with leptospirosis, in- particular calves with redwater, requires veterinary consultation.
Leptospiral organisms are susceptible to antibiotics, especially streptomycin. It is claimed that streptomycin is capable of eliminating the carrier state of leptospirosis in cattle and pigs.
Following initial evidence of leptospiral attack, incontact cows heavy in calf (or sows in pig) could be protected against the risk of abortion by streptomycin treatment. Expense becomes a factor here and veterinary consultation is essential in these cases.
Prevention of leptospirosis through management alone is not reliable. However, avoiding paddocks receiving drainage directly from the milking yards, or poorly drained areas for young calves, should reduce the risk of severe Leptospira pomona infection associated with redwater and heavy mortality.
Another step to reducing Leptospira pomona infection in cattle is to keep them away from pigs, and drainage flowing out of piggeries.
Immunisation is by far the most practical method of controlling leptospirosis. Veterinary consultation is desirable at the start of a vaccination program.
When first starting a vaccination program, 2 shots must be given, 4-6 weeks apart. Immunity to infection will be present approximately 2 weeks after the second injection. This immunity will need to be annually, usually 6-8 weeks prior to calving so the new born calf is protected until it is old enough to be vaccinated and actively develop its own immunity.
Calves are vaccinated when 6-8 weeks old, and again about six weeks later. Heifer replacements should be boostered prior to joining and then prior to calving (in line with the rest of the herd).
A vaccine is now available which combines 5 in 1 leptospirosis vaccines for use in cattle. Vaccination of purchased cattle must not be overlooked.
Control of Leptospira pornona infection in pigs also requires a vaccination program, the details of which are supplied by vaccine manufacturers. Vaccines are also available to counter Leptospira tarassovi.
Vaccines for control of leptospirosis are non-living products, incapable of introducing infection into unexposed or non-infected animals. Leptospirosis vaccination does not interfere with blood testing undertaken for additional investigations of the disease.
Leptospirosis in humans is an occupational hazard of farmers and others in close contact with animals. People can become infected through bare feet, by handling aborted calves or piglets without gloves, by droplets sprayed from urinating animals which reach the eye or nasal passages, or through poor attention to personal hygiene, including washing the hands, especially after handling known-infected animals.
Disinfection is especially important when handling possible cases of infection.
Human leptospirosis resulting from contact with livestock can cause severe illness. Influenza-like symptoms of fever for some 7-10 days, muscular pain, headache, intolerance of light, vomiting, and abdominal pain can occur. Leptospira hardiois is the organism particularly important in this regard.
When any connection between human illness and leptospirosis is suspected, your doctor should be given any information available on the leptospirosis situation on the farm concerned.
The advice provided in this publication is intended as a source of information only. Always read the label before using any of the products mentioned.
Article courtesy of Department of Natural Resources and Environment, Victoria, Australia.