Influence of stress of capture on haematological values and cellular immune responses in the Australian brushtail possum (Trichosurus vulpecula).

Possums (Trichosurus vulpecula) captured for the first time (single-capture) had significantly lower blood lymphocyte and eosinophil counts, but higher neutrophil counts than possums which had been captured frequently. Single-capture possums also had depressed lymphocyte responses to concanavalin A (males and females) and pokeweed mitogen (males only). The haematological changes and the depressed lymphocyte reactivity to the T-cell mitogens were consistent with the animals being in a stressed state following capture for the first time. The haematological profile of single-capture possums changed to a profile similar to that of the frequently captured possums following housing in cages for 1 week, and high lymphocyte responses to T-cell mitogens were recorded following housing for 3-5 weeks. This information, together with body weight data, indicates that a minimum of 4 weeks adaptation to housing in cages should be allowed before possums are used in experimental studies.