Abundance of Culex Tritaeniorhynchus Giles and Culex Gelidus Theobald in Kathmandu Valley, Nepal

Abstract

The present study carried out during April, 2009 to September, 2009 in Tokha and Gothatar of Kathmandu district, Hattiban of Lalitpur district and Balkot of Bhaktapur district has reported the vector abundance, indoor and outdoor densities, resting preferences and age grading of both Culex tritaeniorhynchus and Culex gelidus and hypothesis testing results on significance of monthly variation and areawise variation of both species. During the study period, a total of 30,602 Culex mosquitoes were collected. Among them 404 were Cx tritaeniorhynchus and 55 were Cx gelidus. The study recorded maximum man hour density (9.5) for Cx tritaeniorhynchus from Tokha area in August, 2009 in indoor collection. Similarly, the maximum man hour density was 22.0 in September, 2009 in the same site in outdoor collection. The maximum man hour density for Cx gelidus in indoor was 0.75 recorded from Gothatar and Tokhaareas in August, 2009. The maximum man hour density (4.0) was recorded in outdoor in August, 2009 from Tokha area for Cx gelidus. The highest vector abundance recorded in September, 2009 for Cx tritaeniorhynchus was 1.3 and 0.15 for Cx gelidus in August, 2009 from Tokha area of Kathmandu district. In case of resting preference, a total of 175 Cx tritaeniorhynchus were recorded from indoor and 162 were recorded from outdoor. Altogether 15 Cx gelidus were recorded from indoor and 33 were recorded from outdoor in total collected samples. Out of all collected samples, the gravid females of both species were most commonly found while unfed, fullfed and half gravid abdominal conditions were also observed. The highest density of Japanese Encephalitis vectors were recorded from Tokha and Gothatar area of Kathmandu district, although the hypothesis testing results showed no significance difference between all four sites. The resting habit of vectors was higher at indoor habitats in all prevalent months. The abundance of vectors was higher in August and September as revealed by the results of hypothesis testing. The abundance of Cx tritaeniorhynchus was higher than that of Cx gelidus. This observation of fluctuation in densities, resting preferences and age grading of Cx tritaeniorhynchus and Cx gelidus would be useful for possible inclusion of the Kathmandu valley in the National Japanese Encephalitis Prevention and Control Programme.