Mosquito-borne infections in Fiji: II. Arthropod-borne virus infections

Abstract

SUMMARYSurveys of arbovirus activity in Fiji were conducted over a 10-year period from December 1959 to December 1969. No arboviruses were isolated from over 200,000 mosquitoes, 9000 ticks, or 575 serum samples. Eight thousand human and 1117 bird, bat and animal sera were tested for haemagglutination-inhibiting arbovirus antibody using a variety of group A, group B and Bunyamwera group antigens. Only a small number of low-titre reactions were found among the non-human sera, but 14 % of all human sera were found to contain Group B antibody. The antibody prevalence increased with increasing age, from less than 1 % for persons born since 1950, to 70 % for persons born before 1900. The age differences in prevalence could be used to estimate the time and size of previous epidemics. Differences were found in antibody prevalence between the sexes, between ethnic groups and between persons from different regions. These differences could be explained in terms of climate, location and custom.Historical and serological evidence both suggest that all the antibody detected was due to past exposure to dengue virus. The very high proportion of the population with no dengue antibody makes Fiji a high-risk area for a further dengue epidemic. Dengue virus is known to be active in the Pacific and South-East Asia.

Mosquito-borne infections in Fiji: I. Filariasis in northern Fiji: epidemiological evidence regarding factors influencing the prevalence of microfilaraemia of Wuchereria bancrofti infections

“…In our survey the prevalence of microfilaraemia was always higher among Fijians than among Indians living in similar geographical and climatic situations: even when the prevalences in the two ethnic groups living in settlements were compared, that among Fijian males was found to be slightly higher than among Indian males. Nevertheless, the fact that the maximum prevalence among Indian males was reached at a young age, the observation that elephantiasis among Indians was more prevalent than among Fijians ) and the report by Maguire et al (1971) that the prevalence of dengue antibodies among Indian males was no less than among Fijian males under comparable circumstances suggest that the lower prevalence in Indians could be due to a higher recovery rate, a situation perhaps similar to that producing the differences between the two sexes in Fijians (see below).…”

“…The women are extensively covered by their clothes and they do not work appreciably in the plantations or farms. Their lower exposure to mosquito-borne disease is also demonstrated by the prevalence of dengue antibodies among them; it being 4 % compared with 10 % in males (Maguire et al 1971).…”

“…Women have acquired dengue antibodies at least as frequently as their men folk and presumably from the same species of mosquitoes as those transmitting filariae (Maguire et al 1971). Rates of recovery from filarial infection which were higher in women than in men could result in the observed differences in prevalence of microfilaraemia.…”

“…Only New Caledonia has similar climatic variations, but New Caledonia differs from the others in that the main insect vector is Aedes (Ochlerotatus) (Symes, 1960;Burnett, 1960a). These two Aedes mosquitoes were probably also the main vectors of dengue virus which ravaged the area during epidemics in 1930 and 1943 (Maguire et al 1971). …”

“…but control of the parasite by diethylcarbamazine administered to the human population has offered hope in Fiji (Burnett & Mataika, 1964) as it has elsewhere in the Pacific region (Laigret, Kessel, Bambridge & Adams, 1966;Ciferri, Siliga, Long & Kessel, 1969 (Maguire et al 1971) but reference will be made to the results where they facilitate the understanding of the epidemiology of filariasis. In Fiji the two diseases are comparable in that (1) man is the sole vertebrate host, (2) the same species of mosquito transmit both diseases (Rosen, Rosebook, Sweet & Sabin, 1954) Second survey.…”