Ecology of Aedes Mosquitoes, the Major Vectors of Arboviruses in Human Population

Aedes aegypti (Stegomyia) has been human vectors for many human diseases globally. In recent years, dengue virus has been diagnosed in different regions such as Asia and Latin America vectored by Aedes spp. mosquitoes. Dengue cases have been reported again in the several parts of African and other continental hospital. The different types of breeding sites have been found to be abundant in both urban and rural areas. The abundance of adult Ae. aegypti and habitat productivity in different settings escalates the risk of dengue transmission if viruses are found in asymptomatic population. The insecticide resistance has been found to occur in the wild population of Aedes aegypti to insecticides commonly used for indoor residual spray and long-lasting insecticidal net treatments. The control of human vector population is still a challenge as the vector has a diurnal feeding and outdoor resting behavior. Environmental management is still the best practice to be adopted in many countries for Aedes aegypti control. The currently discovered dengue vaccine might be an immediate arsenal for the community immunization

Efficacy of PermaNet\uae 3.0 and PermaNet\uae 2.0 nets against laboratory-reared and wild Anopheles gambiae sensu lato populations in northern Tanzania

Abstract Background Mosquitoes have developed resistance against pyrethroids, the only class of insecticides approved for use on long-lasting insecticidal nets (LLINs). The present study sought to evaluate the efficacy of the pyrethroid synergist PermaNet\uae 3.0 LLIN versus the pyrethroid-only PermaNet\uae 2.0 LLIN, in an East African hut design in Lower Moshi, northern Tanzania. In this setting, resistance to pyrethroid insecticides has been identified in Anopheles gambiae mosquitoes. Methods Standard World Health Organization bioefficacy evaluations were conducted in both laboratory and experimental huts. Experimental hut evaluations were conducted in an area where there was presence of a population of highly pyrethroid-resistant An. arabiensis mosquitoes. All nets used were subjected to cone bioassays and then to experimental hut trials. Mosquito mortality, blood-feeding inhibition and personal protection rate were compared between untreated nets, unwashed LLINs and LLINs that were washed 20 times. Results Both washed and unwashed PermaNet\uae 2.0 and PermaNet\uae 3.0 LLINs had knockdown and mortality rates of 100% against a susceptible strain of An. gambiae sensu stricto . The adjusted mortality rate of the wild mosquito population after use of the unwashed PermaNet\uae 3.0 and PermaNet\uae 2.0 nets was found to be higher than after use of the washed PermaNet\uae 2.0 and PermaNet\uae 3.0 nets. Conclusions Given the increasing incidence of pyrethroid resistance in An. gambiae mosquitoes in Tanzania, we recommend that consideration is given to its distribution in areas with pyrethroid-resistant malaria vectors within the framework of a national insecticide-resistance management plan

Bio-efficacy of DuraNet® long-lasting insecticidal nets against wild populations of Anopheles arabiensis in experimental huts

Abstract Background Mosquitoes have developed resistance to multiple classes of insecticides for malaria vector control. A new generation of long-lasting insecticidal bed nets (LLINs) has been developed with increased efficacy against these resistant mosquitoes. The present study therefore evaluated the efficacy of the pyrethroid-based LLINs, DuraNet versus PermaNet 3.0, in an Eastern Africa hut design in Magugu in northern Tanzania where mosquitoes’ population higher proportion (69.3%) has been identified as Anopheles gambiae s.l. Methods Standard World Health Organization bioefficacy evaluations were conducted in both laboratory and experimental huts. Experimental hut evaluations were conducted in an area with high populations of Anopheles arabiensis. All nets used were subjected to laboratory cone bioassays and then to experimental hut trials. Mosquito mortality, blood-feeding inhibition, and personal protection rate were compared between untreated nets, unwashed LN, and LN that were washed 20 times. Results Standard WHO laboratory bioefficacy evaluations of DuraNet and PermaNet® 3.0 which were untreated, washed, or 20 times washed showed optimal knockdown and mortality for both net types against a susceptible strain of An. arabiensis. In standard experimental hut evaluations, the blood feeding inhibition for PermaNet® 3.0 unwashed and washed was 82.4% (76.3–88.6%) to 91.5% (84.1–98.8%) while for DuraNet was 98.3% (97.0–99.5%) to 96.0% (94.1–88.2%) respectively. The DuraNet LLINs showed a significantly higher killing effect than the other treatment of 90.0% (86.1–94.2%) and 94.0% (90.2–97.9%) for unwashed and washed nets respectively. No significant difference in deterrence or induced exophily was detected between the treatment arms. There were no adverse effects reported among sleepers in the experimental huts. Conclusion The findings of this study indicate that the pyrethroid-based net DuraNet LLINs attained required efficacy when evaluated against wild population of An. arabiensis from Northern Tanzania. This adds value to the existing vector control tool box which gives community wider choice for vector control

Effect of Different Hosts on Feeding Patterns and Mortality of Mosquitoes (Diptera: Culicidae) and their Implications on Parasite Transmission

Aim: The host-response to hematophagus insects is still an important parameter in understanding disease transmission patterns. We investigated the feeding and mortality rates of three mosquito species, namely Culex quinquefasciatus, Aedes aegypti and Anopheles arabiensis against three different hosts. Materials and Methods: Unfed three to five-day-old female mosquitoes were released in a tunnel box that had a rabbit or guinea pig or mice as a host. The feeding succession patterns of mosquitoes in different hosts were An. arabiensis, Cx. quinquefasciatus and A. aegypti. Results: Mosquito mortality rate was 54.9% for mosquitoes introduced in mice as a host, 34.3% in the Guinea pig and 10.8% for those that introduced in the rabbit. Conclusion: The presence of defensive and tolerable hosts in environment emphasizes the relevance of studying epidemiological impact of these behaviors in relation to diseases transmission