All exotic sheep to remain in quarantine five years

Press, 23 November 1976, Page 23

All exotic sheep to remain in quarantine five years

AH 700 East Friesian sheep and their crossbred progeny in the Ministry of Agriculture and Fisheries’ experimental exotic flock have been destroyed. This follows the recommendations of a special technical committee, after the death in the Mana Island quarantine farm of an East Friesian ewe from scrapie.

The committee comprised Dr G. H. Adlam, the director of the Ministry’s Animal Health Division; Mr R. M. Salisbury, the division's assistant director; Dr W. Te Punga, director of the Wallaceville Animal Research Centre,; Professor N. Bruere, of the Veterinary Clinical Sciences Department, Massey University; and Dr P. G. O’Hara, the superintendent of the Animal Health Reference Laboratory, Wallaceville. The committee also recommended that all the sheep in the programme should be quarantined for a further five years from now. which is two years longer than planned.

This means that none of the remaining breeds (Oxford Down. German Whiteheaded Mutton and Finnish Landrace) can leave quarantine until at least late 1981. Furthermore, the committee advises, if another case of scrapie is detected tn the quarantined animals during this period, all sheep which have been in direct or indirect contact with the infected animal should be destroyed.

According to Dr Adlam, there is no possibility that the disease has affected the national flock. He emphasised it was a quarantine station incident. The four breeds were introduced to the Somes Island maximum security quarantine station in late 1972 and later transferred to Mana Island. Their crossbred progeny were

moved to a speciallyprepared Government’ owned quarantine farm in June this year. "The whole quarantine programme has been designed around the possibility that a sheep infected with the disease might be imported, in spite of detailed pre-selection investigations and severe importation requirements."

In designing the quarantine and disease control procedures, New Zealand began with the protocols used by other countries in importing sheep from the United Kingdom and, from there, elaborated a much more stringent policy, he said.

“Whereas many countries’ quarantine restrictions end after three years and a half confinement on a sheep farm, our conditions require all purebred exotic sheep born here to remain on off-shore Mana Island beyond that period for another two years and a half. The originally imported sheep will never leave the island. “Even the crossbred progeny from exotic rams, out of Romney ewes, are being maintained on the specially approved Ministry-operated quarantine farm under Ihe same conditions and for the same period.” He said each sheep was tattooed on the flank and ear, double ear-lagged and marked with a distinctive MAF sign for positive identification, and all data was computerised. Thus, traceback procedures would ensure that every animal with East Friesian breeding was slaughtered. “Scrapie is an infectious chronic neurosis of adult sheep characterised in most cases by intense itching. inco-ordination and death usually two to six months after clinical symptoms appear. Diagnosis is confirmed by microscopic examination of brain tissue.”

It was not a highly contagious disease, but its long and variable incubation period meant imported animals and their progeny had to be segregated from New Zealand breeding flocks for several years to allow time for any symptoms to develop, said Dr Adlam

“Although scrapie has occurred in the United Kingdom for at least 200 years, the economic loss from it in commercial sheep flocks is small.

“It is an insidious condition. and in many pedigree flocks a few animals may die each year from the disease. The cause of these losses may be unknown to the owners.” Dr Adlam said that as it was not a notifiable disease in the United Kingdom, no regulatory measures were taken to control it there. The lack of any test to detect pre-clinical cases further complicated the problem of selecting sheep from scrapie-free flocks in Britain.

"The diagnosis of the disease in a sheep almost four years after the importation of the animals underlines the need for the six-year-long quarantine period insisted on here.

“As all the quarantined sheep are under official Ministry control and totally segregated from all other animals, the confirmation of scrapie has no effect on the health status of New Zealand flocks.” Dr Adlam said that maternal transmission played the dominant role in scrapie’s spread. The disease was usually transmitted vertically from one ewe generation to the next.

“The role of rams in the spread of the disease is not yet fully understood, but appears to be of a minor nature. Certainly there is no evidence to

date that semen is implicated,”

It seemed lateral spread — spread to unrelated sheep by direct close contact — could occur at lambing time through contact with afterbirth from infected animals, he said. “However, as the crossbred sheep left Mana in June of this year, they were not in contact with the affected animal during the lambing period when lateral spread would have been most likely.” He said that many precautions had been taken on the specially-selected Government-owned farm in the central North Island: “These include double boundary fencing, regular Ministry veterinary inspection and supervision, cheek mustering and the thorough investigation into all deaths. “Only one group of nonexperimental pasture control sheep, after careful ear-tagging. have been licensed off for MAFsupervised slaughter.”

Dr Adlam said that for more than 100 years, until 1952, thousands of sheep were brought to New Zealand from the United Kingdom without any precautions against the introduction of scrapie. “The recognition of the disease during 1952 in Mid-Canterbury in imported Suffolk sheep led to the present, ban on routine importations, and the slaughter of the infected flock.

, “Apart from one other outbreak in 1954, which was traced directly to the 1952 one, no further cases occurred, in spite of the fact that contact, animals had gone to 191 properties.”