Leptispirosis

This is one of the commonest causes of reduced fertility and pregnancy loss in cattle. It also causes milk drop and increased cell counts. Even humans are not safe as the leptospires can infect us to cause a range of symptoms from 'flu' and headaches through to full-blown meningitis and death.

What happens when a bovine becomes infected with lepto?

Lepto is excreted in urine and milk, but it is the urine that really helps to spread the disease. Contaminated urine droplets, either on the ground or in the air, can enter the cow's body via eyes, mouth, nose or broken skin (if you can smell urine that's droplets in your nose!). The leptos then enter the blood stream and head for their target tissues - ovaries (infertility), uterus (abortion/infertility), udder (milk drop/cell count) and kidney (carrier state - reinfects other cows).

What are the major risk factors for Leptospirosis?

The 4 main factors that increase your chances of getting lepto are as follows: -

1. Open vs. closed herd
2. Bull vs. AI
3. Co-grazing sheep with cattle
4. Water courses

How do I find out if I've got lepto?

Diagnosis of lepto 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 a profile of the herd's lepto situation needs to be done to assess the level of infection. This can be done in two stages. A bulk milk sample will give you some indication of the level of infection on the farm. This can be followed up with blood tests to get a more detailed idea of what is going on. Just at the moment we are able to offer the laboratory fees free of charge for these diagnostics. When you are having acute milk drop caused by lepto the diagnosis is normally easier as the symptoms occur at the time of infection. This means we can look for a change in the level of immunity in the cows' blood, which demonstrates recent infection.

What do I do if I have lepto?

Depending on the severity of the disease you will need to consider two options. Where lepto has started to cause substantial loss to the farm (abortion storms or severe milk drop), as it does when it finds a non-immune herd of cows, then you will need to inject all cows with antibiotic to kill off the leptospires. This is then followed with vaccination. We have done this on a number of farms with very pleasing results. Where lepto is endemic rather than epidemic (i.e. it is causing a lower level of continuous loss in the form of pregnancy loss and infertility) we tend to advise vaccination only. The vet will help you to decide which is the best plan of action for your farm.

When is the best time to vaccinate?

The peak time for excretion of lepto by carrier cows is following turnout. This is because of the change in urine pH. For this reason we advise vaccination in March/April so that you have maximum immunity over the peak risk period. We often find farmers are vaccinating at the wrong time because the abortions from lepto are commonly diagnosed in summer or early autumn (because of the lag phase mentioned earlier). If this happens to you we advise vaccinating at this time but bringing your first booster forward to March of the next year.

Which animals would I need to vaccinate?

You would need to vaccinate all breeding animals above 6 months of age. If you allow an animal to become a carrier then vaccination will not cure it and it may continue to have problems, as well as keep a level of challenge going on the farm. For this reason we advise vaccinating from 6 months to make the herd become totally free over a period of a few years. To short cut this you can inject the herd with antibiotics first to clear out carriers. To save money we would not vaccinate animals you are likely to be culling in that year. Don't forget that bulls can carry and spread lepto so they need to be included in your control programme.