Also known as lepto, leptospirosis is a very contagious disease. All cows can be infected by the bacteria which cause lepto. Animals, other than cows, can also have the disease including dogs, pigs, deer, rodents, sheep, and goats. Cattle generally tend to experience milder signs and symptoms than these other animals. Calves can die as a result of catching leptospirosis although it is not very common for the disease leading to death in older cows.
Bovine leptospirosis is caused by two types (serovars) of bacteria from a group known as Leptospira hardjo. The bacteria can be found in the kidneys, uterus, and sex glands of cows. They gain access to these organs through wounds, the eye, or the mouth and replicate in the liver. The bloodstream then carries them to particular areas of the body.
Young calves will not have fully developed their immune systems and so are more at risk. In addition, if a calf does become infected it will usually show more severe signs and symptoms than an older cow. Other cattle more susceptible to bovine leptospirosis are those situated near water or sheep. Leptospirosis is usually transmitted via contaminated drinking water, infected urine, feed, and pastures. The infection may enter through the eye, broken skin or via the mouth. Other animals infected by the disease are also able to act as sources of infection.
Signs and symptoms include a decrease in milk production, abortions, and a lower fertility level. Bovine leptospirosis is a zoonotic disease which means it can be transferred to humans and human signs and symptoms are similar to those of the flu. Vaccinations are available to protect against infection, thus reducing the spread of the disease.
Transmission of leptospirosis
Transmission of lepto is usually a result of sharing pastures and drinking water, especially if it is stagnant. The season most associated with contraction for the disease is summer as cattle are more likely to be kept outside. Aborted material and urine that is infected with the disease can also be sources of infection. Sheep act as carriers of the disease and so cattle that drink from the same water sources as infected sheep are able to contract bovine leptospirosis. If there is mixed grazing between cattle and sheep then there may also be a transmission of the bacteria. Bulls used for breeding may transmit the disease and care must be taken when importing a bull from another farm. Artificial insemination semen is considered to be a safer method for breeding.
Cattle are able to host the bacteria, even after recovery, for many months and shed the virus via urination. Thus, this contributes to the spread of bovine leptospirosis. Outside of the host, the bacteria can survive for a few months in conditions with the correct temperature and moisture levels. This includes certain stagnant watercourses. It is important to note that humans are also at risk of contracting the disease. If infected aborted material is handled or there has been contact with contaminated water and urine, then the bacteria can be transferred to humans.
Signs and symptoms of lepto
Signs and symptoms include abortions, a decrease in milk yield but also a decrease in fertility has been suggested. Additionally, a high temperature can be observed as well as lethargy, a loss of appetite, and a reluctance to move. Not all the signs will be presented or, in some cases, noticed. Cattle which are vaccinated or that have developed effective immune systems experience milder, if any, symptoms following infection.
In terms of the decrease in milk yield, in most cases the reduction is extremely rapid leading to the emptied udder being known as a “flabby bag”. The udder will not be hard to the touch. Any milk that can be extracted may contain small amounts of blood or have a similar texture and appearance to colostrum.
Lepto causes approximately every three in ten cows to abort in the last third of pregnancy. The more times a herd is infected by the virus, the less likely abortions will occur. Abortion is also less likely if the pregnant cow has become infected at the beginning of her pregnancy. Naive herds are more susceptible to abortions as well as beef cattle since less effort is made to ensure up to date vaccinations are administered. Calves are more severely affected by the disease. They may present bloody urine and high temperatures. It is fairly common for calves to die following acute infection.
Treatment of leptospirosis
Administration of antibiotics decided by a veterinarian is the main method of treatment. Alongside this, a course of vaccinations may be given if many cows in the herd are infected. The antibiotics used are usually either streptomycin or tetracycline. Without antibiotic treatment, as well as not curing the cow, the bacteria will have more time to spread. It also increases the risk for humans.
Prevention of leptospirosis
Preventative methods of medicine such as vaccination are recommended to reduce transmission. Calves at the age of four months old are able to be administered the vaccine although, if the mother was vaccinated during pregnancy or thirty days before, then maternal immunity will pass on to the calf for approximately six months. The initial dose is given four to six weeks before the second and this is followed by annual boosters. The boosters provide the cattle with long term immunity. If cattle are continually being imported and exported to and from the farm then the boosters are advised to be given twice yearly.
As well as vaccination, there are other methods to reduce the chances of infection. Breeding methods such as artificial insemination are thought to be safer than sharing bulls and the herd can be tested periodically to check for signs of infection from different strains of lepto. New cows should be fully vaccinated before entering the farm and cattle should not share pastures or water courses with sheep. Urine should be prevented from entering any drinking water and good ventilation and hygiene is vital.
Diagnosis of leptospirosis
Bovine leptospirosis is initially diagnosed by observing the signs and symptoms presented and gaining knowledge of any possible history of the disease within the herd or on the farm. Following this, the disease is confirmed via laboratory diagnoses. Blood and milk samples may be taken and the pathogen identified by searching for and finding the relevant antibodies. Dark-field microscopy is sometimes used to detect the presence of infection by taking samples of urine. ELISA tests are used to check up on the herd by testing the milk in bulk. Aborted faces can be tested using immuno-florescent staining methods.
Prognosis of leptospirosis
The prognosis for most animals if treated in time is generally good. It is even better if the cow has previously been vaccinated. Despite this, lepto can be fatal for young calves infected by the bacteria.