Objectives To determine the distribution of virus infection during an outbreak of Japanese encephalitis (JE) in the Torres Strait, and to describe the environmental factors facilitating the outbreak. Design Human and porcine serological surveys for JE virus activity throughout the Torres Strait, and mosquito and household surveys on the island of Badu. Setting The island of Badu (where the clinical cases occurred) and the other islands of the Torres Strait, Australia, during April‐May 1995. Results The serological surveys identified recent JE virus infection among residents or domestic pigs on at least nine outer Torres Strait islands. A JE virus, confirmed by nucleotide sequencing, was isolated from two asymptomatic Badu residents. Virus isolations and mosquito surveys implicated Culex annulirostris as the major vector involved in the outbreak. There was prolific Cx. annulirostris breeding in a variety of water bodies close to and within the Badu community. Over half (53%) of the households kept pigs in pens, and many (63%) of the pigpens were situated near standing water; in 56% of these “wet” pigpens Cx. annulirostris was breeding. Conclusions There was evidence of widespread JE virus activity throughout the outer islands of the Torres Strait. We suggest that migratory birds and/or wind‐blown mosquitoes could have imported the virus into the Torres Strait from a focus of viral activity, possibly in Papua New Guinea, thereby initiating the outbreak. A combination of environmental factors, with large numbers of domestic pigs in close proximity to human dwellings and mosquito breeding sites, undoubtedly facilitated the outbreak on Badu.

Objective To describe the circumstances of two cases of Japanese encephalitis (JE) in north Queensland in 1998, including one acquired on the Australian mainland. Design Serological surveillance of sentinel pigs for JE virus activity; serological surveys of humans and pigs and viral cultures of mosquito collections. Setting Islands in the Torres Strait and communities in the Northern Peninsula Area (NPA) and near the mouth of the Mitchell River in Cape York, Queensland, In the 1998 wet season (December 1997‐May 1998). Results Sentinel pigs in the Torres Strait began to seroconvert to JE virus in February 1998, just before onset of JE in an unvaccinated 12‐year‐old boy on Badu island. By mid‐April, most sentinel pigs had seroconverted. Numerous JE viruses were isolated from Culex annulirostris mosquitoes collected on Badu. In early March, a person working at the mouth of the Mitchell River developed JE. Serological surveys showed recent JE virus infection in 13 young pigs on a nearby farm, but not in 488 nearby residents. In NPA communities, sentinel pigs seroconverted slowly and JE viruses were isolated from three, but none of 604 residents showed evidence of recent infection. Nucleotide sequencing showed that 1998 JE virus isolates from the Torres Strait were virtually identical not only to the 1998 isolate from an NPA pig, but also to previous (1995) Badu isolates. Conclusions JE virus activity was more widespread in north Queensland in the 1998 wet season than in the three previous wet seasons, but ecological circumstances (eg, less intensive pig husbandry, fewer mosquitoes) appear to have limited transmission on the mainland. Nucleotide sequencing indicated a common source for the 1995 and 1998 JE viruses. Circumstantial evidence suggests that cyclonic winds carried infected mosquitoes from Papua New Guinea.

Stem canker of oilseed rape (canola, Brassica napus) is associated with a species complex of two closely related fungal species, Leptosphaeria maculans and L. biglobosa. Of these, L. maculans is the most damaging and develops gene-for-gene relationships with the host. Here, a wide scale analysis of the L. maculans -L. biglobosa species complex was performed throughout the American continent (23 locations from Chile to Canada) plus several locations in Western Australia for comparison purposes, based on a collection of 1132 isolates from infected tissues of a susceptible cultivar. Fungal species were discriminated on the basis of morphological, phytopathological and molecular criteria and showed that L. biglobosa was closely associated with L. maculans in most of the locations. Multiple gene phylogeny using sequences of ITS, actin and b-tubulin confirmed the prevalence of the L. biglobosa 'canadensis' sub-clade in Canada, whereas up to three different sub-clades of L. biglobosa were found in Georgia (USA). Race structure of L. maculans was investigated using a combination of pathogenicity tests and PCR amplification of avirulence alleles AvrLm1, AvrLm4 and AvrLm6. Three contrasting situations were observed: (i) race structure in Ontario, Chile and Georgia was related to that of European and Western Australian populations, with a low race diversity; (ii) only one race was found in Mexico, and not found outside of this country; (iii) a large diversity of races was observed in central Canada (Manitoba, Alberta and Saskatchewan) with very specific features including maintenance of avirulence alleles absent from Europe, absence of the AvrLm7 allele common in Europe (or eastern Canada) and wide location-to-location variability.

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During the summer 1994 outbreak of epidemic polyarthritis in suburban Brisbane, 29,931 adult female mosquitoes were collected by octenol-CO2 light traps and tested for virus by species in pools of approximately 20 using an in situ enzyme-linked immunoassay. Overall, 63 isolations of Ross River (RR) virus were made from 7 different mosquito species, including 23 from freshwater-breeding Culex annulirostris Skuse, 13 from peridomestic Aedes notoscriptus (Skuse), 4 from Aedes procax (Skuse), 12 from the brackish water-breeding Aedes funereus (Theobald), 9 from saltmarsh Aedes vigilax (Skuse), and 1 each from Culex sitiens Wiedemann and Aedes alternans (Westwood). The RR virus minimum infection rate in mosquitoes ranged from 1.6 to 2.5/1,000 from March to June 1994. This study implicates freshwater and brackish water mosquitoes as important suburban vectors of RR virus and indicates the need for refocusing mosquito control priorities.

Objectives: To investigate two outbreaks of dengue type 2 in north Queensland, one in the Torres Strait beginning in late 1996, the other in a Cairns suburb in early 1997. Design: Epidemiological investigation of all laboratory‐confirmed cases of dengue, entomological investigation of the local environment, and laboratory analysis of the isolated dengue viruses. Main outcome measures: Numbers of confirmed and of locally acquired cases; virus serotype; comparison of nucleotide sequences between viruses isolated from the two outbreaks; and Breteau Index (Bl = number of containers with larvae of the mosquito vector Aedes aegypti found per 100 houses investigated) on the affected islands and in the Cairns suburb. Results: There were 201 confirmed cases of dengue in the Torres Strait outbreak, which lasted nearly seven months, and seven confirmed cases in the Cairns outbreak, which lasted about nearly 11 weeks. Most (190) were confirmed as dengue type 2. Nucleotide sequencing of viruses isolated from the two outbreaks showed they were identical. Ae. aegypti breeding sites were very common on the five Torres Strait islands surveyed (Bis, 73‐219 ‐ high risk), but less so in the Cairns suburb (Bl, 23). The most common breeding sites were water storage reservoirs, particularly rainwater tanks, on the outer Torres Strait islands, discarded containers (such as plastic containers, buckets and tyres) on Thursday Island, and garden items (such as flowerpot bases and jars) in Cairns. Conclusions: The virus responsible for the Cairns outbreak was most probably introduced from the Torres Strait, whereas the virus responsible for the Torres Strait outbreak was imported from Papua New Guinea. Preventive strategies tailored to specific locations are needed to reduce breeding of Ae. aegypti in north Queensland, and the consequent risk of future outbreaks of dengue.

Japanese encephalitis (JE) virus first appeared in Australia in 1995, when three clinical cases (two fatal) were diagnosed in residents on Badu Island in the Torres Strait, northern Queensland. More recently, two confirmed human JE cases were reported in the Torres Strait Islands and Cape York Peninsula, in northern Queensland in 1998. Shortly after JE virus activity was detected in humans and sentinel pigs on Badu Island in 1998, adult mosquitoes were collected using CO2 and octenol-baited CDC light traps; 43 isolates of JE virus were recovered. Although Culex sitiens group mosquitoes yielded the majority of JE isolates (42), one isolate was also obtained from Ochlerotatus vigilax (Skuse). Four isolates of Ross River virus and nine isolates of Sindbis (SIN) virus were also recovered from members of the Culex sitiens group collected on Badu Island in 1998. In addition, 3,240 mosquitoes were speciated and pooled after being anesthetized with triethylamine (TEA). There was no significant difference in the minimum infection rate of mosquitoes anesthetized with TEA compared with those sorted on refrigerated tables (2.8 and 1.6 per 1,000 mosquitoes, respectively). Nucleotide analysis of the premembrane region and an overlapping region of the fifth nonstructural protein and 3' untranslated regions of representative 1998 Badu Island isolates of JE virus reveled they were identical to each other. Between 99.1% and 100% identity was observed between 1995 and 1998 isolates of JE from Badu Island, as well as isolates of JE from mosquitoes collected in Papua New Guinea (PNG) in 1997 and 1998. This suggests that the New Guinea mainland is the likely source of incursions of JE virus in Australia.

Abstract. During 1996-1998 60,619 mosquitoes were collected around Cairns, Australia and processed for Alphavirus 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.