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30 May 1997
The parasite Trichinella spiralis has been found in a ‘home-killed' pig bought from a back-yard herd in Mamaku, near Rotorua. The incidence of T. spiralis is very low in New Zealand. The last recorded case of the disease in domestic pigs in this country was in 1974.
Samples taken from the pig were tested initially by the Meat Industry Research Institute in Hamilton and later confirmed by a MAF Quality Management expert
parasitologist, after the person who bought the pig submitted samples for testing.
Available evidence suggests that a reservoir of T. spiralis infestation exists in New Zealand wildlife such as rats and wild cats, and that on rare occasions this spills over into domestic pigs. Modern pig farming practices significantly reduces the probability of domestic pigs becoming infected.
Since 1974, pigs slaughtered at abattoirs have been routinely monitored for the presence of T. spiralis. All samples tested so far have been negative for the presence of the parasite. Since 1990 all exported feral pigs processed through game packing houses have also tested negative.
The farm from which the infected pig was bought was immediately served with a restricted premises notice by the Ministry of Agriculture, which means nothing can move on or off the farm. Checks are being made by MAF into the number of pigs on the farm, their ages and their contact with wildlife such as rats. The whereabouts of other pigs sold from the farm will also be traced, and any meat or meat products on the farm will be sealed and samples taken for laboratory testing.
The parasite can affect a number of warm-blooded mammals, including humans, who can pick it up from eating certain types of raw or under-cooked meat carrying the infective parasite larvae.
Correctly cooked meat poses no risk, as the larvae are killed by proper cooking. Deep freezing for extended periods also significantly reduces the chance of infection.
The parasite, primarily found in pork, wild game and bear meat, can be transferred to humans by eating raw or under-cooked meat from an infected meat-eating animal. The infectious parasite larvae are digested with the meat, and the larvae invade the small intestine. The hatched larvae are carried by the blood and lymph to the muscles. Overseas, incidents in humans have been traced to uncooked meats and smallgoods which are often supplied directly from small farms, not via large regulated abbatoirs. The other source has been contaminated meat from wild game killed and eaten by hunters.
MAF advises the public that meat of any type should be bought only from reputable commercial operators, who will be selling inspected product.
Symptoms of trichinosis in humans include fever, muscular pain, swelling of eyelids or face, headaches and diarrhoea. If left untreated it can be fatal. There have been three recorded human cases in New Zealand, the last recorded in 1965. The control measures relating to trichinosis which have been in place for many years have resulted in no cases being seen in New Zealand for more than 30 years.
Media inquiries to:
Dr David Bayvel, Acting Chief Veterinary Officer (025) 470 582 / (04) 476 3009-hm
Debbie Gee, Manager, Corporate Communications (025) 465 870