Leptospirosis, commonly referred to as “Lepto", is caused by the spiral-shaped bacteria
Leptospira. It is one of the commonest causes of reduced fertilty and pregnancy loss in cattle. It also causes milk drop and increased cell counts. Wildlife such as rats can carry the disease and spread infection. Humans can also be infected by the bacteria causing a range of 'flu' like symptoms.
Lepto is excreted in urine and milk. Contaminated urine droplets (on the ground or in the air) can enter the cow's body via the eyes, mouth, nose or broken skin. The bacteria then enter the
blood stream and head for their target organs - ovaries (infertility), uterus (abortion/infertility), udder (milk drop/cell count) and kidneys where the animal 'carries' the disease and can then reinfect other cows by shedding the disease in its urine. Leptospira organisms can survive in the environment for weeks to months depending on environmental conditions, and some organisms have been shown to survive in stagnant, standing water or in wet soil for longer than six months if the temperature is favourable.
Risk factors for contracting Leptospirosis:
- Open herd
- Using bulls rather than AI, especially if shared
- co-grazing sheep with cattle
- having water courses used by a mixture of animals
A bulk milk sample is a good place to start to give some indication of the level of infection on the farm. On beef and dairy farms blood samples can be taken which will tell us if they infection is circulating and to find out whether the animal has been previously exposed. Abortion enquiries can sometimes give false negatives due to the interval between infection and abortion.
Acute infection in a naive herd can lead to dramatic losses caused by abortion storms or severe milk drop. It may be necessary in some circumstances to treat all cows with antibiotics to kill the bacteria. This would then be followed up with vaccination. Where the infection is endemic (i.e. causing a lower level of continuous loss in the form of abortion and infertility) we advise vaccination
Good management is vital in the control of leptospirosis and includes:
1. Eliminating access of cattle to surface water or streams used by other livestock.
2. Removing rubbish that harbours wildlife and rats.
3. Limiting access of rodents and wildlife to livestock feed.
4. Eliminating urine drainage into water sources.
5. Reducing contacts between cattle, other livestock, rodents, and wildlife as much as
6. Cleaning, disinfecting, and drying barns, pens, and other confinement areas after use by infected cattle.
7. Draining or fencing swampy areas likely to harbor the leptospires.
8. Vaccinating susceptible animals for relevant serotypes.
9. Keep your herd closed if possible.
10. Use AI rather than a bull.
Vaccination ususally consists of a primary course of two injections at least 4 wks apart. Ideally the course should be completed in the spring before the main transmission season at turnout. Re-vaccination with a single booster should be given annually to maintain protection and progressively reduce exposure in the herd. If the primary course is given later than spring it should be given in the following spring and annually thereafter.
You would need to vaccinate all breeding animals above 6 months of age. For this reason we advise vaccinating from 6 months to ensure the herd becomes free from disease over a period of a few years. To short cut this you can inject the herd with antibiotics first to clear out carriers. Don't forget that bulls can carry and spread lepto so they need to be included in your control programme.