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Will you be vaccinating your cattle against Leptospirosis?
Carolyn Hogan BVetMed MRCVS 

The sun is shining, the daffodils are out, and so soon will be the cows, so comes the question, will you be vaccinating your cattle against leptospirosis this year?

It’s easy to forget the potential losses from disease when disease control programmes are working. And that’s when it can be tempting to look at reducing costs by removing the cost of vaccines for diseases you’re no longer seeing. Probably because the vaccines are working! So when you’re deciding whether or not to take that gamble you need to look again at what that gamble is.

What are the clinical signs of Leptospirosis?
Leptospira Hardjo infection in cattle causes effects on reproduction (infertility, abortion and weak calf syndrome), and milk drop.

  • Flabby Bag’ is the colloquial name given to the effects on milk production. The udder becomes soft and flabby, and milk production drops off dramatically for 5-6 days. If milk drop occurs before peak lactation then the peak will never be achieved.
  • Abortion can occur 3-12 weeks after infection, with most abortions happening in the last 3 months of pregnancy. There is a marked seasonal incidence in late summer. Infection can also produce premature or weakly calves.
  • Infertility or subfertility results from leptospires localising in the uterus, causing inflammation, which leads to early death of the embryo1. The cow is seen returning to service at regular or irregular intervals. One study showed a conception to first service in clean cows of 46%, compared to just 30% in infected cows2. This would have a significant impact on any herd, and particularly in beef suckler herds aiming to calve 65% of their cows in the first 3 weeks of the calving period.

Spread of Leptospira Hardjo is mainly via Contaminated Urine
Because Leptospira Hardjo localises in the kidneys, the greatest route of infection is via contaminated urine, and the main period of transmission is during grazing, peaking from June to October. Excretion reduces when cattle are housed and fed silage possibly due to increased urine acidity. This is why vaccination against leptospirosis is usually done pre-turnout.

Leptospira Hardjo is also a zoonotic disease, which means humans can be infected. Dairy farmers handling and milking cows are particularly at risk of coming into contact with infected urine in the parlour.

Risk Factors for Leptospirosis
Herds where cattle are bought in, cattle co-graze with sheep, bulls rather than AI is used, or cattle have access to shared watercourses, are all at increased risk of Leptospira hardjo infection.  In 2014 SAC Consulting Services diagnosed leptospirosis in a 160 cow dairy herd where twelve cows experienced a sudden onset drop in milk production, with no other clinical signs. The affected animals had access to a stream shortly before the first case was observed and this was considered to be the source of infection.

Persistence and Prevention of Infection
Leptospires can stay in the kidneys of infected cattle for a long period of time and these cattle will shed leptospires either intermittently or continuously for days or even years. These cattle provide an important reservoir of infection within the herd.

Biosecurity measures can help reduce the risk of exposure to infection; however it would be very difficult to completely eradicate bovine leptospirosis in the UK because of the high percentage of infected herds. In practical terms, vaccination provides the most reliable way of protecting a herd4.

Should you vaccinate?
So, we are back to the question about whether or not to vaccinate against leptospirosis this spring. In August 2016 SAC Dumfries reported 2 confirmed cases of leptospirosis in dairy herds5.  In one of the herds vaccination had lapsed as a cost saving measure. Stopping vaccination is certainly a very quick way of reducing farm expenditure, but are you prepared and can you afford to take the risk from a potential disease recurrence?

Disease prevention plans should always be based on a comprehensive risk management approach for your herd, and discussed thoroughly with your vet.

 

Source: livestockfarming.co.uk


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