Bacteria present for over a decade

20 December 2001

MAF's investigation into a bacterial disease outbreak in goats and some calves fed unpasteurised goats milk in the Waikato suggests it may have been present in goats in New Zealand for over a decade.

Derek Belton, Director Animal Biosecurity for the Ministry of Agriculture and Forestry (MAF) said the information was crucial in deciding how to manage Mycoplasma mycoides subspecies mycoides (large colony) (MmmLC) in goats.

"Clearly if the bacteria has been in the country for a number of years, we need to consider how widely it has spread." He emphasised the bacteria does not pose a human health risk.

"Developing the necessary diagnostic tests will assist our surveillance, though our investigations suggest plenty of opportunity for spread in goats during this time." he said.

Mr Belton stressed that MmmLC is distinct from the more serious Mycoplasma mycoides subspecies mycoides small colony (MmmSC) which has not occurred in New Zealand. MmmLC is endemic in almost all countries and does not therefore post a risk to New Zealand's meat exports.

This week's meeting of the Technical Advisory Group (TAG) has formulated recommendations on how to manage the outbreak of MmmLC. The TAG is made up of MAF officials and industry experts.

The key recommendation was that as MmmLC is probably already established in New Zealand goatherds, eradication in goats is not technically, physically or economically feasible.

As a result, the Restricted Places status imposed on the four goat farms in the Waikato will be removed. Information on managing the infection on suspect farms, and on prevention of infection on non-infected farms, will be provided generally to goat farmers and veterinarians.

Development of reliable tests to accurately detect infection with the bacterium in goats should be continued with a view to providing a testing service to the goat industry on a voluntary and cost-recovery basis. This will allow goat farmers to determine whether infection with MmmLC is present in their herds, or in herds they wish to purchase goats from.

MAF's New Zealand Animal Health Reference Laboratory has, in the course of two months, developed and applied a battery of antibody and DNA based tests, as well as culture techniques. Over 3,800 tests have been programmed or completed and once validated the most accurate and efficient tests would become available to animal health laboratories to offer in their range of testing services, said Mr Belton.

Current tests can identify infected herds, but are not sensitive and specific enough to accurately detect infected and non-infected individuals within a herd.

The TAG also considered and made recommendations on the management of the isolated disease outbreak in cattle to prevent it's spread. There was also discussion on the practice of feeding unpasteurised milk to cattle. No calves affected by MmmLC will enter the breeding herd.

Evidence of previous rare isolations of MmmLC in cattle reported in the international literature, and the views of an international expert on the lack of a significant threat to cattle posed by MmmLC, indicate that the bacterium is very unlikely to be a significant disease of cattle.

Findings indicate that the disease outbreak occurred as a result of high dose and high-risk exposure of a large number of very young calves, something that hadn't been reported previously.

The TAG acknowledged the uncertainties about the behaviour of MmmLC in cattle, and recommended a cautious approach be continued by slaughtering all exposed calves. While, MmmLC is not a danger to human health, none of the slaughtered cattle will enter the food chain.

The Restricted Places status on the nine cattle farms will be removed once the exposed cattle have been slaughtered.

The AgResearch containment facility at Flock House will remain under restricted movements as studies continue on the calves held there. Studies have been initiated to investigate the prevalence, persistence and spread of the infection in calves. Results are expected later next year.

Mr Belton praised the willingness of the goat and dairy industry to work with MAF in finding solutions to the outbreak of MmmLC. He also paid tribute to the farmers who have worked with MAF during the investigation.

"A disease outbreak creates a difficult situation - for the people directly affected, for the industries that are at risk, and for the response teams that are called into action. The groups have worked very effectively together," he said.

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