Mosquito biting activity on humans & detection of Plasmodium falciparum infection in Anopheles stephensi in Goa, India.

Background & objectives: Knowledge of the bionomics of mosquitoes, especially of disease vectors, is essential to plan appropriate vector avoidance and control strategies. Information on biting activity of vectors during the night hours in different seasons is important for choosing personal protection measures. This study was carried out to find out the composition of mosquito fauna biting on humans and seasonal biting trends in Goa, India. Methods: Biting activities of all mosquitoes including vectors were studied from 1800 to 0600 h during 85 nights using human volunteers in 14 different localities of three distinct ecotypes in Goa. Seasonal biting trends of vector species were analysed and compared. Seasonal biting periodicity during different phases of night was also studied using William’s mean. Results: A total of 4,191 mosquitoes of five genera and 23 species were collected. Ten species belonged to Anopheles, eight to Culex, three to Aedes and one each to Mansonia and Armigeres. Eleven vector species had human hosts, including malaria vectors Anopheles stephensi (1.3%), An. fluviatilis (1.8%), and An. culicifacies (0.76%); filariasis vectors Culex quinquefasciatus (40.8%) and Mansonia uniformis (1.8%); Japanese encephalitis vectors Cx. tritaeniorhynchus (17.4%), Cx. vishnui (7.7%), Cx. pseudovishnui (0.1%), and Cx. gelidus (2.4%); and dengue and chikungunya vectors Aedes albopictus (0.9%) and Ae. aegypti (0.6%). Two An. stephensi of the total 831 female anophelines, were found positive for P. falciparum sporozoites. The entomological inoculation rate (EIR) of P. falciparum was 18.1 and 2.35 for Panaji city and Goa, respectively. Interpretation & conclusions: Most of the mosquito vector species were collected in all seasons and throughout the scotophase. Biting rates of different vector species differed during different phases of night and seasons. Personal protection methods could be used to stop vector-host contact.

Geographical distribution and evaluation of mosquito larvivorous potential of Aphanius dispar (Rüppell), a native fish of Gujarat, India.

Background & objectives: Certain indigenous fish can play potential role in vector control. The study recorded distribution of Aphanius dispar (Rüppell) in its native habitats in Gujarat, India and evaluated its larval propensity for Indian mosquito vectors. Methods: Fishes were surveyed in various districts of Gujarat and samples were collected from coastal habitats and were identified to species. Physicochemical properties of water samples were analysed in the laboratory. Five laboratory acclimatized adult fish (2.2–3 cm) released in chlorine-free water in glass jars were provided with 500 larvae daily. Five replicates were run. Daily consumption of I to IV instars of Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus was recorded separately for three days. Anopheles stephensi larval control using the fish in industrial tanks (9–180 m2) was evaluated. Results & conclusion: The fish was found in large numbers in estuarine waters, rivulets, backwaters and small dams in the districts of Kutch, Jamnagar, Patan and Anand in Gujarat. Mean daily consumption of larvae in laboratory was as follows: An. stephensi 128 ± 0.2 to 204 ± 6; Cx. quinquefasciatus 24 ± 4 to 58 ± 10; Ae. aegypti 43 ± 5 to 68 ± 2. In water tanks, A. dispar reduced 93% larval counts by Day 7 and 98% by Day 21 (p <0.01), showing high larval propensity. A consolidated information on bionomics, tolerance and physicochemical properties of water taken from natural habitats of A. dispar indicate its high larvivorous potential. Large-scale evaluation is warranted to evaluate its potential in vector-borne disease control.