Turnout is not far away, and now is the time to be considering what vaccinations should be carried out to protect livestock from disease as they go out to grass.
Bovine Leptospirosis can be a major problem at turnout because of urine contaminating the lush pasture we hope to see in the spring. One study carried out in 2003 demonstrated infection levels in British herds of greater than 70%, leading to major economic loss.
The disease is spread mainly from urine droplets entering the body via the eyes, nose, mouth, and broken skin. Four main syndromes are seen:
Abortion storms: Normally occuring 4-12 weeks after infection, usually in the latter part of pregnancy.
Milk drop: This has been described as ‘flabby bag syndrome’. All four quarters are affected, giving a dramatic decrease in milk yield, showing colostrum-like milk and a high cell count.
Infertility: A high incidence of silent heats and return to oestrus is noted, leading to a high cull rate and extended calving interval.
Weak calves: Infection during pregnancy, if it does not lead to abortion, is evident in calves with lighter birth weight and greater susceptibility to disease
These signs of disease and known risk factors, such as keeping an open herd, using a bull, co-grazing sheep and access to water courses, should lead to suspicion of disease.
Studies have been carried out on herds infected with Leptospirosis where they underwent trials to assess the effects of vaccination. Half of the animals in the trial were vaccinated, the rest being left unvaccinated.
Overall conception rates (OCR) between the two groups were measured and the vaccinated cattle showed a significantly higher OCR (49%) compared with those left unvaccinated (29%).
This could lead to substantial savings if infected herds were vaccinated.
A screening programme for the control of this disease in dairy herds is easily started using bulk milk samples to measure the level of immunity and so get an indication of the level of exposure.
In suckler herds blood samples are taken from a representative number of animals, the results giving an indication of the level of exposure within the herd.
Vaccination can be used to control the disease in herds already exposed and to prevent disease in those that are not.
If you suspect a problem, you should consult your veterinary surgeon.
Another aspect to this disease is that it can be transmitted to humans, and so has implications in relation to control of substances hazardous to health legislation.
The most likely people to be at risk of infection are farmers/herdsmen, vets and AI technicians.
Symptoms are of a prolonged flu-like illness with severe headaches, which can become meningitis if left untreated.
Early diagnosis and treatment will shorten the course of the disease but it can still be several months to recovery.
It should also be noted that signs may be seen in humans before any are seen in the herd, so any lingering flu-like conditions should be investigated by your doctor. It is also worth noting that pasteurisation destroys the infection in milk.