Rob Hall continues his look into infectious diseases with Leptospirosis up this month…
Lepto is one of the most common causes of reduced fertility and pregnancy loss in cattle. It can also cause milk drop and increased cell counts.
The disease is spread mainly through urine of infected animals but also through uterine discharge, aborted material and semen from infected bulls. The infectious organism is then absorbed from these fluids via the mucus membranes, for example the eyes, mouth, nose or reproductive tract. Once the leptospirosis organism is in the cow’s system it travels via the blood to the target tissue – ovaries (causing infertility), uterus (abortion/infertility), udder (milk drop/ high cell count) and kidneys (spreading to other animals via urine).
There are four major risk factors that increase the likelihood of a farm getting leptospirosis:
1. Open herd (vs. closed herd)<br/ > 2. Using a bull (vs. AI)
3. Co-grazing sheep alongside the cattle
4. Open water courses (urine from wildlife is consumed by cattle)
There are two main forms of the disease which affect cattle:
- Udder form – seen mostly after calving. There is a sudden drop in milk yield affecting all quarters and the udder appears flaccid. The udder secretion becomes thickened and clotted; occasionally it is bloody or yellow in colour. This is often accompanied by fever, reddening of the membranes around the eyes and reduced feed intake.
- Abortion – seen on its own or after milk drop syndrome. This usually occurs 3-12 weeks after the cow is infected. Most abortions occur in the second half of gestation. Some reduced fertility may also be seen in the herd due to early embryonic loss.
Diagnosis of leptospirosis can be quite difficult. With abortion and pregnancy loss there is normally an interval between infection and loss of the foetus. This means if you test the cow at the time of abortion you have normally missed the boat.
Instead we choose to assess the level of leptospirosis in the herd. The easiest way of doing this is through bulk milk testing. Through our Infectious Disease Check scheme we are offering this to our farmers on a quarterly basis thanks to financial support from a number of sponsors. Where necessary, we can follow this up with individual animal blood testing.
Diagnosis following an acute milk drop is normally easier as this occurs closer to the time of infection. By testing for antibody increase in two samples taken two weeks apart we can detect immune response from infection.
In the case where acute Leptospirosis infection is diagnosed by your vet, treatment with antibiotics may be appropriate before vaccination. Similarly, in herds where ongoing exposure of the herd to Leptospirosis is diagnosed vaccination will most likely be the best course of action.
A robust vaccination programme will be drawn up by your vet, which will include annual vaccination of all breeding animals over six months of age, including bulls. Vaccination is best carried out around turnout, as chronically infected carrier cows shed the lepto organism in higher numbers at this point in the year. It also ensures that cows have maximum immunity over the peak risk period. For seasonal grazing herds, vaccination should be time to ensure maximal protection during the breeding period.
Lepto is a zoonotic disease, so good hygiene precautions should be practised at all times, especially with aborting cattle. Infection of humans may cause flu like symptoms and the disease can result in severe damage to the liver or kidneys. Pregnant women can miscarry. If there is any suspicion of the disease in your cattle, please contact us as soon as possible.