A behaviour study on the potential for direct transmission of tuberculosisfrom possums (Trichosura vulpecula) to alpacas (Lama pacos), and the converse from alpacas to possums

Aims. To evaluate the potential for the direct transmission of tuberculosis from possums to alpacas, and vice versa. Methods. A field study was conducted on an alpaca farm in Northland, New Ze aland on 7 January 1999. Observations were recorded on the interaction of o ne group of male alpacas with a simulated dead possum, one male and one fem ale alpaca group with a simulated terminally tuberculous possum, and one gr oup of male alpacas with a normal possum in an enclosure from which the ani mals could not escape. The possum was sedated with ketamine as hydrochlorid e to simulate death (inactive; no movement), and terminal illness (active, inco-ordinated movement around the paddock). The observations were based on the focal animal sampling technique, they were un-replicated, and recorded visually and manually with intermittent still photography Results. Both male and female alpacas showed strongly inquisitive interacti on with the possum. They clustered around the possum (focal animal) very so on after it was observed by the first member of the group. The interest of the majority of both sex groups remained high for the observation periods o f approximately 30 minutes, and most individuals remained within 5 metres o f the possum for that time. Approximately 50% of the alpacas were within po ssible aerosol transmission distance of 2 metres from the sedated, erratica lly mobile possum with their heads towards it for approximately 50% of the two observation periods. Aggressive behaviour was recorded for a young male with stamping on the moving possum. Similar, but more vigorous and prolong ed stamping behaviour was recorded for a female with a young (<1 week) offs pring (cria). The stamping behaviour was accompanied by very close nose to nose contact of the alpaca and possum. At one point the female threw the po ssum approximately 1.5 metres in the air with her teeth. The group of male alpacas placed in an enclosure with an unsedated normal possum generally mo ved away from the possum during its rapid active attempts to escape. When i t became inactive their approaches were cautious and only once elicited a d efence reaction from the possum, from which they recoiled. One male made on e attempt to stamp on the active possum. Soon after the possum became inact ive in a small loose hay pile, the alpacas lost interest in it. Conclusions. The alpaca / possum behavioural interactions show there is pot ential for direct aerosol transmission of tuberculosis from possums to alpa cas, but probably not from alpacas to possums.