Around 70% of unvaccinated UK herds continue to show evidence of leptospirosis infection, according to 2006 test results released by the Bovine Leptospirosis Information & Screening Service (BLiSS).

Since the launch of the BLiSS initiative in 1999, Schering-Plough Animal Health has monitored the levels of leptospirosis infection in the national dairy and beef herd based on laboratory analysis of milk and blood samples. In 2006 69% of bulk milk samples tested positive for antibodies to the disease. In addition, 77% of BLiSS blood samples submitted last year indicated exposure to leptospirosis infection.

But whilst laboratory analysis of milk and blood samples is undoubtedly a practical and cost-effective diagnostic tool for assessing the overall extent of leptospirosis infection, vets warn that the current technique will not pinpoint the particular strain of the disease threatening an individual herd.

“Unfortunately, routine testing of bulk milk and herd blood samples does not distinguish between the two L.hardjo strains – hardjo-bovis and hardjo-prajitno – that are known to affect cattle in the UK,” cautions Schering-Plough Animal Health livestock veterinary adviser Andrew Montgomery MRCVS.

“We know from research that two strains infect cattle in the UK – with prajitno being more commonly isolated from animals showing severe clinical signs of leptospirosis: for example, those with severe milk drop or aborting. However, routine testing cannot identify the actual strains on an individual farm. Consequently, when it comes to implementing an effective vaccination programme it's important to use Leptavoid-H, which is the only vaccine that provides protection against both strains of the disease,” he stresses.

Andrew Montgomery says leptospirosis is one of those insidious, costly livestock diseases that commonly results in a grumbling fertility problem in unvaccinated herds. “A series of independent studies has clearly proved the link between the disease and depressed conception rates and this is a significant drain on profits. For example, for every day leptospirosis potentially causes calving index to slip over 365 it's been estimated that it costs you at least £2.50 per day. So when you consider you only need to stop as little as a two day slippage to make a return on vaccination, it's an investment well worth making,” he says.

He points out that herds most at risk from leptospirosis are those that buy stock in; those that use a bull and not AI; those where cattle co-graze with sheep; and those that graze near watercourses. “So unless you operate a truly closed herd, it is important to talk to your vet about testing for leptospirosis and vaccination,” he advises.

Spring turnout is the key risk period for leptospirosis transmission. At grass, uninfected cattle are suddenly exposed to the urine of any infected animals that may be shedding leptospires. Moist spring grass is also a relatively favourable environment for leptospires, allowing them to survive for longer outside the host.

Cattle producers can easily screen their herd for infection, Schering-Plough says. Milk and blood sample diagnostic support is available from participating vet practices. In addition, if milk producers are sending milk samples to NMR for fat, protein and cell count analysis, they can easily ask their laboratory to screen for leptospirosis as well using the NMR Healthcheck service, the company points out.

RABDF/Defra Farm Health Planning Award launched
Cattle Industry urged to be vigilant in keeping Bluetongue out
Semex's Solution to Finding the Perfect Mate