Kunjin Research Articles

Studies of the epidemiology of arthropod-borne virus infections at Mitchell River Mission, Cape York Peninsula, North Queensland: I. Mosquito collections, 1963–1966

40,508 female mosquitoes of 40 species were collected in light- or chicken-baited traps or biting man, on 8 occasions in the period March 1963 to November 1966, at Mitchell River Mission, Cape York Peninsula, North Queensland. Catches were highest for most species in the wet season, but Ficalbia and Aedeomyia were more abundant in the dry season and Mansonia and Coquillettidia equally common in both seasons. Variations in population between seasons and between successive years could be correlated with rainfall and with known breeding sites. A comparison of collections on chickens and on man suggested that Anopheles species fed on mammals, Culex pullus and Culex squamosus on birds, and other Culex species, Mansonia, Coquillettidia and Aedes on both; Uranotaenia, Ficalbia and Aedeomyia were not taken on either host. Culex annulirostris, the most frequent source of arboviruses in the area, was also the commonest mosquito taken; it showed seasonal variation in host preference, with a higher proportion taken on man in the dry season; it is suggested that its association with man-made breeding sites may be of value in control. Host preferences described for Anopheles spp. and Culex squamosus suggest that mammals may act as vertebrate hosts for Mapputta, Kowanyama and MRM3630 viruses, and birds as hosts for Kunjin virus. The seasonal variation in population of Anophelines known as potential vectors of malaria is discussed with reference to the past history of malaria in the area.

Studies of the epidemiology of arthropod-borne virus infections at Mitchell River Mission, Cape York Peninsula, North Queensland: III. Virus studies of wild birds, 1964–1967

8 strains of 4 arboviruses were isolated from blood and organs from 775 birds captured at Mitchell River Mission in 6 collections from October 1964 to March 1967. 3 strains of Ross River virus (from Grallina cyanoleuca, Microeca fascinans and Poephila personata) and 1 strain of Corriparta virus (from Charadrius melanops were isolated in March-April 1965; 3 strains of a Group B virus (from Centropus phasianinus) and 1 strain of Kunjin virus (from Oriolus flavocinctus) were isolated in March-April 1966. The Group B virus was found antigenically distinct from those previously isolated in Australia, and has tentatively been named Alfuy virus. No viruses were isolated from birds collected during the dry seasons. Serological tests on bird serum or blood gave additional evidence of infection with Group B arboviruses, Sindbis, Corriparta and Koongolg Group viruses. The isolation of Ross River virus from birds was at some variance with the results of previous serological surveys and is discussed.

The neutralization of arboviruses: II. Neutralization in heterologous virus-serum mixtures with four group B arboviruses

Neutralization by rabbit antisera to Murray Valley encephalitis, West Nile, Kunjin, and Edge Hill viruses was studied by plaque assay of surviving virus. The neutralization slope of the regression lines in dose-response experiments for each hyperimmune serum was significantly greater in homologous reactions than in cross reactions. The regression line equations were transformed to an “area function” which represented a summation of the neutralizing activity over the whole range of antiserum dilutions, providing a useful basis for comparing the potency of antisera. Normalizing these area functions permitted evaluation of antigenic relationships. The inclusion of fresh serum in the tests increased neutralization in most cases, but specificity was not improved. In contrast to the results of neutralization tests determined by intraperitoneal inoculation in mice, hyperimmune sera exhibited greater specificity than immune sera in the plaque assay, and in the plaque inhibition test. Kunjin antisera displayed similar neutralizing activity against both Kunjin and West Nile viruses in all three assay systems. Values for the neutralization slopes were considered in relation to an affinity term for interaction between small molecules and protein. Variations in slope with the same serum assayed in different hosts or against different viruses were interpreted as being due to recognition by the specific host cell of different dispositions of antigen-antibody complexes comprising a critical area on each neutralized virus particle.