A serological survey of the prevalence of antibodies against enteroviruses in brushtail possums (Trichosurus vulpecula) in New Zealand: Enteroviruses have a limited distribution in brushtail possums

Abstract

AIM: To establish an immunoassay to detect antibodies against enteroviruses in brushtail possums (Trichosurus vulpecula), and to determine the prevalence of seropositive samples of antibodies to enteroviruses in wild possums in New Zealand.

METHODS: A sandwich ELISA was established to detect antibodies to enteroviruses in possums. The IgG fraction of guineapig polyclonal antibodies to enteroviruses of possums was used as the capture antibody to bind the enteroviral antigens prior to incubating with test sera from possums. The bound antibodies from the test sera were detected using a conjugate specific to possum immunoglobulins. An archival serum bank was surveyed for the prevalence of seropositive samples, from possums, to the virus. The sera were collected from possums from areas of Northland, Wanganui, Castlepoint, Paraparaumu, Shannon, Orongorongo, Nelson, Hokitika, Banks Peninsula, Riverton, Kawau Island, Chatham Island and Stewart Island, between 1993 and 1996. Possums were captured from farmland, forest margin, scrub, beech, exotic forest or native forest.

REULTS: Antibodies to the enteroviruses were detected in possums from Shannon (56/270; 21%), Wanganui (4/46; 9%), Kawau Island (3/44; 7%), and Orongorongo (1/43; 2%). The proportion of seropositive possums per area was similar for those found on the forest margin or pasture grazed by sheep and cattle compared with those in the forest. Seropositive possums were significantly older than those that were seronegative (p<0.01).

CONCLUSIONS: The distribution of enteroviruses in possums was clustered in the Manawatu-Wanganui regions, where the viruses were originally isolated. The limited distribution was likely due to the lack of contact between possum populations due to natural barriers. If a recombinant enterovirus carrying a biocontrol agent against possums was released it would encounter little interference from field strains in the majority of the country, due to the limited distribution of these viruses in the field.

KEY WORDS:

• Possum
• enterovirus
• ELISA
• serology
• survey

Acknowledgements

We thank H Chiang for his excellent technical assistance, L Morrison for statistical analysis, and Drs DD Health and PE Cowan (Landcare Research) for provision of the bank of sera from possums. This project was contracted by the Animal Health Board and the Foundation for Research, Science and Technology, New Zealand.