By Trudi Baird
13 October 2001 — Leptospirosis is a serious disease and a real threat to both animals and humans. But, due to heightened media attention, farmers could be forgiven for thinking it is only a matter of time before their farm becomes infected with the disease.
In reality, the disease is associated more with the North Island and in particular with cattle. Although other regions of New Zealand do have confirmed cases of Leptospirosis, Southland and Otago are probably the least likely to be effected. This might come as a surprise to many farmers given the high profile case of the Southland sheep shearer who recently contracted the disease and came close to death.
Janet Tyson, speaking on behalf of OSH, said from information gathered it suggests that the lower South Island isn’t considered a “problem area” for the disease – be it in cattle, deer or sheep. But she warned that although there may be a low level of infection in sheep, if one animal within a flock becomes infected then a farmer can expect the whole flock to become infected. This is due to the highly infectious nature of Leptospirosis.
There are various types of Leptospirosis but the two common types are hardjo and pomona. The disease tends to be linked with pigs, cattle and, in more recent times, deer.
John Smart, of Clutha Vets, said if Leptospirosis does show up in the south it tends to be the hardjo bacteria rather than pomona. But he said he believes the disease is more of a problem in the North Island than here and that sheep are not considered active carriers.
Dr Smart confirmed he has never had to deal with a confirmed case of the disease in sheep.
Similarly, Andrew Roe of Central Southland Vets, said although it is widely vaccinated against in dairy cattle, he has not encountered any confirmed cases in sheep.
The Leptospirosis bacteria attack the kidney and liver of animals and is spread through contaminated urine. For this reason it is deemed a winter-time disease as surface water on paddocks assists in the spreading of bacteria. It can also survive in waterways which are another risk area due to stock drinking the water down-stream from a farm carrying infected stock Dr Roe said one of the difficulties with Leptospirosis is the lack of clinical signs in an infected animal.
While some will become weak or anaemic, other animals just carry the disease and shed the infectious bacteria without showing symptoms. Often it will be the younger animals who get sick but testing for the disease can be difficult, he said.
Blood testing of cattle can be done but the test cannot distinguish between vaccination antibodies and the bacteria itself, so if animals have been vaccinated at any time, a reliable test result is difficult. Vaccination does not offer guaranteed protection either.
Another method of testing is to culture the bacteria from urine but Dr Roe said this is not fool proof as an animal can excrete the bacteria intermittently.
Testing of sheep can also be carried out but it is not common. Dr Roe said he wouldn’t recommend testing unless an animal is showing symptoms during the winter or spring time. Symptoms are not definite but can include anaemia (caused by blood loses through kidney damage) or lambs becoming weak, lethargic or starting to die. The time to watch for the disease in lambs is from weaning onwards when the bacteria is more likely to be picked up through grazing or drinking water.
Paul Langford, of Northern Southland Vets, said he has not encountered the disease down here in cattle, deer or sheep and believes it would be hard to find in Southland, even in dairy herds. He puts this down, in part, to the annual vaccination programme of most dairy farmers.
He is aware of a few sheep flocks in the King Country which were diagnosed with the disease and he has spoken to North Island deer vets who have encountered it in their areas.
Clinical signs of the disease in deer can be similar to those shown in cattle and include abortion or red water in fawns – which is not to be associated with the grazing of second growth swedes.
Category: Animal Health