Search

The positive rate of dogs with Dirofilaria immitis microfilariae among house dogs was examined for 27 years from 1968 to 1994 in the southern and northern parts of Nagasaki City. Roles of the number of the main vector, Culex plpiens pallens and of RPSS (rate of population utilizing a sewage system) were analyzed statistically in relation to the annual changes in microfilarial prevalence. In the southern and northern parts, there was a clear correlation among three parameters of the positive rate in the dogs, the number of Cx. p. pallens and RPSS. The present study proved that the decrease in the positive rate of dogs in both the southern and northern parts is mainly attributable to a decrease in the number of Cx. p. pallens. which resulted from the decrease of the breeding places of this mosquito following the spread of the public sewage system and the improvements in the use of roads and open roadside ditches., 日本熱帯医学会雑誌, vol.23(2), pp.133-137; 1995

Female mosquitoes including Culex pipiens pallens, the main vector of Dirofilaria immitis, and some secondary vectors, were collected at 4 to 10 sites in Nagasaki City from 1983 to 1989 using light traps, and the number of the mosquitoes and the natural infection rate with D.immitis were compared between the southern and the northern parts of the city. In 1983, Cx. p.pallens was extremely prevalent in the southern part but not in the northern part. After 1986, the prevalence of Cx. p.pallens became very low in both the parts. The rapid decrease of prevalence of this species may be attributable to the decrease in breeding sites by improvement of roads and open roadside ditches in parallel with spread of sewage systems. On the basis of the number of infected mosquitoes in Nagasaki City, it was suggested that, Cx. tritaeniorhynchus and Ae. albopictus are important vectors in addition to Cx.p.pallens, but Ae. togoi does not play a significant role in the transmission of D.immitis., 日本熱帯医学会雑誌, vol.22(4), pp.199-206; 1994