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28 January 1999
Another chapter of New Zealand history is about to close with the Ministryof Agriculture and Forestry hoping to declare the country provisionally free from truehydatids later in the year.
Hydatids has featured in New Zealand for as long as the sheep industryitself. An 1887 medical practitioners' circular showed extensive experience of thedisease.
This once deadly, now largely forgotten disease, was responsible for thedeaths of 142 people between 1946 and 1956. Many more people underwent repeated surgicaloperations to remove hydatids cysts from internal organs.
MAF has been responsible for hydatids control since 1991, and no new humancases have been reported in recent years. A single confirmed case in 1998 involved aninactive cyst in a cattle beast. True hydatids, which is caused by the tapeworm parasite Echinococcusgranulosus, is now so rare in livestock that these days even finding a single cystsuch as this in an animal at slaughter is a major event.
Even more promising is that such incidents have been confined to a singleisolated area during the past five years.
This is a far cry from the situation at the beginning of the NationalHydatids Council's eradication programme in 1959, when up to 80% of sheep from certainparts of New Zealand were found to have hydatid cysts at slaughter.
Both townies and farmers will recall visiting the local hydatidsdog-dosing strip which was part of the eradication programme, along with dog control,regulations on home killing, and a ban on feeding uncooked offal to dogs. With most of NewZealand clear of the disease, the days of six-weekly dosing of dogs ended in 1996, but dogowners still have an obligation to ensure that offal is thoroughly cooked before feedingto dogs.
The strict inspection of livestock passing through slaughterhouses was avital part of the eradication programme, and post-mortem inspection of livestock atslaughterhouses remains a cornerstone of the current control programme.
The current programme is based on the principle that people must beresponsible for animals they own or are in charge of. This places obligations on allowners of dogs and/or livestock.
Some people still confuse sheep measles and true hydatids. Sheep measles,which is common in New Zealand, is not a human health risk, but rather a product qualityissue.
True hydatids, on the other hand, is much more serious. The parasite canonly mature in dogs, but to complete its life cycle it also needs an intermediate host. InNew Zealand, the main intermediate host is sheep. Dogs become infected by eating fertilehydatid cysts in raw sheep offal (liver or lungs). Sheep become infected by grazing onpasture contaminated with tapeworm eggs passed in dog faeces.
Hydatids disease in man usually follows close contact with infected dogs.Such dogs are most likely to infect their owner or owner's children. The effect on thehealth of people can vary from no symptoms to severe illness and death, depending on thenumber of cysts, their site and size.
Every year there are around 30 million sheep and lambs and three to fourmillion cattle, calves and deer slaughtered and inspected in New Zealand. The absence ofcysts provides strong assurance that the parasite is almost beaten.
However, inactive cysts may continue to be found occasionally - but withdecreasing regularity - for some time years yet. Whenever they are found, they arefollowed up with a detailed investigation of the property to make sure no hidden pocketsof the disease remain.
MAF will ensure appropriate inspection and control efforts continue untilcomplete eradication of true hydatids from New Zealand is achieved.
If all goes according to plan, MAF hopes to be able to give theprovisional all clear this year, meaning New Zealand will enter the new millenniumhydatids-free.
Media inquiries to:
Howard Pharo, National Advisor, Agriculture Security, MAF Regulatory Authority: 04-474 4100
Debbie Gee, Director, Corporate Communications, MAF: 04-474 4258