Behavioural studies on the potential for direct transmission of tuberculosis from feral ferrets (Mustela furo) and possums (Trichosurus vulpecula) to farmed livestock

Abstract

Studies were conducted to evaluate the response of cattle and deer to ferrets which were sedated so they behaved like terminally tuberculous animals, and to compare this with the response of cattle, deer and sheep to sedated possums. Six groups of deer and two groups of cattle were exposed to a sedated ferret and to a sedated possum. Both livestock species showed interest in the possum by sniffing and licking it, but they only briefly touched the ferret and no licking or extended investigation was observed. The proportion of available time spent in physical contact with the possum by cattle was 7.7 times as high as for the ferret, and for the deer was 5.7 times as high. The behavioural response of three groups of sheep to a sedated possum was investigated, and sheep showed limited interest beyond viewing the possum from a distance. The amount of time spent by sheep investigating the possum was very low and the intensity of exploration was also low. For possums, at least one deer was within 1.5 m (an estimate of the distance that tuberculosis can be transmitted by aerosol) for 50.9% of observation time, and in physical contact with the possum for 9.5% of time. The figures for cattle were 69.3% and 17.3%, while those for sheep were 6.9% and 0.3%. In interactions with ferrets, the equivalent figures were 29.8% within 1.5 m and 2.2% in physical contact for cattle, and 20.8% and 1.1% for deer. Tuberculous possums commonly and tuberculous ferrets less commonly have lung lesions and/or discharging sinuses, and may excrete Mycobacterium bovis intermittently or continuously in aerosols or discharges. The exploratory behaviour of deer and cattle in this study would provide opportunities for them to become infected with M. bovis if they had contact with infectious possums, and less probably with ferrets. The response of sheep to possums suggests that they would be much less likely to contract the disease.

Bovine Tuberculosis in Free-Ranging Carnivores From Michigan

“…While most mammalian species are susceptible to bovine tuberculosis (Francis 1958), only a few non-ruminant species are thought to be reservoirs of M. bovis. Brushtail possums (Trichosurus vulpecula) and ferrets (Mustela furo) in New Zealand (Patterson et al, 1995;Sauter and Morris, 1995) and European badgers (Meles meles) in England and Ireland (Nolan and Wilesmith, 1994;O'Reilly and Daborn, 1995) are believed to be reservoir hosts for bovine tuberculosis. These species develop extensive lesions containing tremendous numbers of bacilli.…”

Effects of sustained control of brushtail possums on levels ofMycobacteriumbovis infection in cattle and brushtail possum populations from Hohotaka, New Zealand

“…Davidson, 1976), and DNA fingerprinting studies show that often the same strain of M. bovis is infecting both species (Collins et aZ., 1988). Additionally, biologically plausible mechanisms have been described for transmission of M. bovis from tuberculous possums to livestock (paterson and Sauter and Morris, 1995) and large-scale possum control operations are usually followed by a significant reduction in the incidence of Tb in cattle (Tweddle and Livingstone, 1994;Ministry of Agriculture and Fisheries, 1986). Control of possum populations is now routinely undertaken in areas where possums are, or are considered likely to be infected with M.…”

Advances in New Zealand mammalogy 1990–2000: Deer

“…In the wild, however, deer-to-deer transmission of Tb appears to be rare (Nugent & Lugton 1995;Lugton et al 1998), and prevalence in deer declines when infected sympatric possum populations are reduced to low densities . Wild red deer are primarily "spillover" hosts that appear to become infected mainly by, for example, investigating terminally ill possums (Sauter & Morris 1995). Most infected deer appear able survive for at least several years (GN unpubl.…”