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2 November 2001
A goat farm and a cattle farm, both in the Waikato area, have been hit by a disease outbreak caused by a bacterium thought to be new to New Zealand.
The bacterium - Mycoplasma mycoides subspecies mycoides (large colony) (MmmLC) - causes polyarthritis in goats, which is characterised by painful swelling of several joints.
So far, 34 cases in kids and 39 cases in calves have occurred. Six kids and 10 calves have died or been put down.
Ministry of Agriculture and Forestry exotic disease response programme co-ordinator Matthew Stone said MmmLC had not previously been reported in New Zealand or other countries as a disease of cattle, but can cause disease in sheep. No sheep are currently known to be involved in the outbreak here.
He said treatment with antibiotics can assist in the resolution of clinical signs of disease, but was not effective in eliminating infection and recovered animals typically become long-term carriers.
Dr Stone said that, unusually, tests expected to detect antibodies to the bacterium did not indicate infection in either the goats or the calves. The unexpected negative test is being investigated by sending serum samples overseas to the laboratory in the United Kingdom where typing of the organism occurred.
MAF began investigating the outbreak in August this year, after the dairy goat farm began experiencing illness in kids. Evidence that it had spread to a calf-rearing farm became apparent in late August when calves presented with a similar syndrome characterised by polyarthritis and pneumonia.
Investigations revealed that unpasteurised milk had been purchased from a dairy factory for feeding to the calves. Some of this unpasteurised milk originated from the infected goat farm.
This link was confirmed when evidence of Mycoplasma was found in tissue taken from calves and in milk samples retained by the dairy factory.
Dr Stone said that, as a containment measure, movement of animals has been restricted on the two infected properties and several others where kids and calves have been moved since the outbreak began.
A Technical Advisory Group (TAG) made up of representatives from MAF, industry stakeholders, and including veterinary and industry experts, is currently being set up to consider response options. The final response decision will be made by the Director of Animal Biosecurity following the report from the TAG.
MmmLC is an organism subject to market access requirements in export certificates for sheep and goats (live animals, semen and embryos) to certain countries. Some export certificates have been withdrawn and will require re-negotiation. MAF is liaising directly with exporters who may be affected.
Mycoplasmas are killed by pasteurisation. MmmLC does not infect humans.
MmmLC is found in Europe, Africa, North America and Australia, where it causes sporadic outbreaks of pneumonia, arthritis, conjunctivitis, and mastitis in goats, and in some countries, sheep.
It is reported to have occurred here once before, in a single goat in New Zealand in the 1970s. Surveillance had not found further evidence of the organism till now, and New Zealand was considered free.
Dr Stone said mycoplasma were a complex group of micro-organisms.
"Some species and types are important pathogens of livestock, with significant production and international trade implications. One of the most important of these is Mycoplasma mycoides subspecies mycoides (small colony- SC), the cause of contagious bovine pleuro-pneumonia, and quite distinct from MmmLC.
"Other livestock Mycoplasma occur almost worldwide, with limited impact. Accurate definition of the organism type involved in the New Zealand outbreak was therefore essential before initiating any response.
"Accurate reporting of the organism type is likewise considered essential by MAF to avoid confusion."
Matthew Stone, Programme Coordinator Exotic Disease Response MAF Biosecurity