Copyright 2000 by The American Society of Tropical Medicine and Hygiene MOSQUITO ISOLATES OF ROSS RIVER VIRUS FROM

Abstract. During 1996–1998 60,619 mosquitoes were collected around Cairns, Australia and processed for Al-phavirus isolation. Thirty-three isolates of Ross River (RR) virus were made from 9 species, Aedes imprimens, Aedes kochi, Aedes notoscriptus, Aedes vigilax, Culex annulirostris, Culex gelidus, Mansonia septempunctata, Verrallina (formerly Aedes) carmenti, and Verrallina lineatus. Attempts to isolate RR virus from 121 Aedes aegypti were unsuccessful. Twenty-six (79%) of the isolates came from within 1 km of a colony of spectacled flying-foxes, Pteropus conspicillatus. The minimum infection rate for these mosquitoes was 1.0 compared with 0.2 per 1,000 for mosquitoes trapped at all other sites. Ross River virus has not previously been isolated from Ae. imprimens, Cx. gelidus, Ma. septempunctata, Ve. carmenti, or Ve. lineatus. This is also the first isolation of an arbovirus from Cx. gelidus in Australia. In conclusion, the vector status of Ve. carmenti, Ae. aegypti and Ma. septempunctata warrants further study. This study also provides evidence that P. conspicillatus may be a reservoir host. Ross River (RR) virus is a mosquito-borne Alphavirus that occurs in Australia, Papua New Guinea, and the Solomon Islands.1–3 Human infection may cause arthralgia and arthri-tis, possibly persisting for long periods.4,5 The average num-ber of notified cases in Australia during 1991–1996 wa