The susceptibility of two species of wallaby to infection with Trypanosomaevansi

Objective To determine the susceptibility of the agile wallaby (Macropus ag ilis) and the dusky pademelon (Thylogale brunii) to infection with Trypanos oma evansi. Method Two agile wallabies and three dusky pademelons were experimentally i nfected with between 5x10(4) and 10x10(4) T evansi from a cryopreserved sta bilate isolated from an Indonesian buffalo. Animals were observed twice dai ly for clinical signs and blood was collected every 3 days to determine par asitaemia. Necropsy was conducted on animals that died or were euthanased w hen in extremis and representative tissue sections examined. Results All wallabies developed a high parasitaemia by 6 days after infecti on, which persisted until death or euthanasia in extremis, between days 8 a nd 61. Clinical signs included anorexia, weakness and ataxia. Anaemia occur red in one wallaby that survived for 61 days. Gross pathological changes va ried between animals. They included pericarditis, serous atrophy of fat, sp lenomegaly, ulcerative gastritis and enteritis. Histological changes were c haracterised by a mononuclear cell infiltration of the connective tissue of most organs with little cellular destruction. Striking lesions were seen i n the choroid, heart, stomach and small intestine. Conclusion Agile wallabies and pademelons are highly susceptible to infecti on with Tevansi. Wallabies, therefore, have the potential to spread Tevansi within New Guinea and Australia if infection is introduced. Mortality is l ikely to be high thereby acting as an indicator of recent introduction. His tological changes seen in wallabies infected with Tevansi are diagnostic fo r infections occurring in Australia and Papua New Guinea.