Anopheline mosquitoes and malaria parasites in Taiwan

Extensive taxonomic studies of the genus Anopheles were carried out in Taiwan during the first half of the 20th century. As a result, 17 species of Anopheles were identified and reported as occurring in Taiwan. However, the occurrence of two species, An. kochi and An. fluviatilis, in Taiwan is doubtful. Vector competence of the anophelines of Taiwan was also studied both in the laboratory and in the field during the same period of time, and experimental infections of 8 species of Anopheles were carried out by Anazawa in the 1920s. The results showed that all species tested were susceptible to three human plasmodia except for An. sinensis which was refractory to Plasmodium falciparum. The results of dissection of nearly 10,000 anopheline mosquitoes collected from the field by various workers suggested that An. minimus is the chief vector in Taiwan. Crithidial flagellates resembling malaria sporozoites were found in the salivary glands of 4 common species of Anopheles collected from cow-stables. These flagellates may have been misidentified as malaria sporozoites in the earlier investigations. During the first part of the operations for malaria control and eradication, anopheline mosquitoes were collected by day from 1,118 houses scattered over the island. Of the 25,656 specimens of Anopheles collected, nearly 80% were An. minimus, mostly from bedrooms. Since the highly anthropophilic and endophilic An. minimus was determined to be the chief vector of malaria in Taiwan, DDT was applied to the wall surfaces in houses for malaria control and eradication. Before spraying DDT, the rate of P. malariae infections was very high in areas where malaria is endemic. However, these infections were more quickly suppressed by DDT spraying than two other parasite species. Other details of studies on the ecology and behavior of anophelines are also presented.