Distribution of vectors, transmission indices and microfilaria rates of subperiodic Wuchereria bancrofti in relation to village ecotypes in Samoa

Abstract

Aedes polynesiensis and Ae. samoanus biting densities and Wuchereria bancrofti infection and infective rates were studied in 47 villages throughout the islands of Samoa Upolu, Manono and Savaii during 1978-79, and microfilaria (mf) rates were surveyed in 28 of the villages. The mf rate was correlated with both infection and infective rates of Ae. polynesiensis in Upolu, but not of Ae. samoanus. In Upolu, Ae. polynesiensis was apparently the major vector. It was relatively more abundant in more cultivated and populated areas, along the northern coast of Upolu, except Apia town area. In Savaii, Ae. samoanus predominated over Ae. polynesiensis except in "plantation" villages. Relatively high biting densities and rates of infection and infectivity indicated that Ae. samoanus was not less important than Ae. polynesiensis as a vector in Savaii. Ae. samoanus preferred natural vegetation, in contrast to Ae. polynesiensis which was found near human habitations in cultivated land. There was no difference between the biting densities of Ae. polynesiensis in "coastal" and "inland" villages, indicating that crab holes (numerous only in some coastal villages) may not influence the density of Ae. polynesiensis. Higher mf rates were associated with villages where Ae. polynesiensis, rather than Ae. samoanus, was dominant, indicating that Ae. polynesiensis was generally a more efficient vector. In the former villages, the difference in mf rates between males and females was smaller than in the latter, probably reflecting a difference in biting habits of the vectors. Ae. polynesiensis infections were recorded in plantations over 2 km from any village, suggesting that both habitats were foci of transmission.

Dry Season Production of Filariasis and Dengue Vectors in American Samoa and Comparison with Wet Season Production

“…polynesiensis occurred during periods of high rainfall with higher biting rates after these periods. 25,31 Such direct effects of rainfall on natality and mortality could explain the reduced productivity measured in our rainy season samples, but further research is needed to determine if these effects occur with Aedes spp. in American Samoa.…”

Effect of Water Resource Development and Management on Lymphatic Filariasis, and Estimates of Populations at Risk

“…23,26,27 As will be shown in our review and has been noted before, LF transmission is spurred by rapid urbanization in the absence of accompanying waste management and sanitation facility programs. [28][29][30][31][32] Second, a large-scale campaign built around chemotherapy and improved sanitation proved successful to control LF in the Shandong province, People's Republic of China. 33 Third, Durrheim and colleagues recently suggested that chronic parasitic diseases, including LF, could be used as viable health indicators for monitoring poverty alleviation, as the root ecological causes of these health conditions depend on poor sanitation, inadequate water supply and lack of vector control measures.…”

“…polynesiensis was small. 30 High numbers of Culex vectors were found in urban areas dominated by wastewater mismanagement and domestic water storage. 29,31,32 Transmission parameters.…”

“…Table 5 summarizes the five studies that assessed the impact of water resource development and management on transmission parameters. Three studies were carried out in irrigation schemes, 36,38,40 one study evaluated the impact of water mismanagement in the face of urbanization, 30 and one study was undertaken after a water management control program had been launched. 29 Overall, it was found that irrigation, waste-water mismanagement, water storage, or waste accumulation generally lead to increased biting rates, higher transmission potentials, and a higher proportion of vectors infective or infected with microfilaria.…”

Distribution of breeding and control of the filariasis vector Aedes samoanus in leaf axils of Pandanus in Samoa

“…In order to assess the significance of Ae.samoanus breeding in Pandanus axils in Samoa, the results of our larval survey may be correlated with the adult densities of Ae.samoanirs. In a study reported elsewhere (Samarawickrema et al, 1987), the average density per manhour of Ae.samounus was 33.1 in Upolu and 67.1 in Savai'i. Both in Upolu and in Savai'i, greater abundance of Ae.sanzoarzus was recorded in villages with natural vegetation, inland villages and shaded villages, as opposed to plantation villages, coastal villages and open villages.…”