ABSTRACT
Background & objectives: Phlebotomine sandflies are vectors of leishmaniases and other diseases. Long-lasting insecticidal nets (LLINs) as possible tools for control have not been widely tested against them. The objective of this study was to determine the efficacy of Olyset® Net and PermaNet® LLINs alongside a local brand, K-O Tab® treated net (Supanet) against Phlebotomus duboscqi female sandflies. Methods: Four replicates of unwashed and 20x washed Olyset Nets and PermaNets, K-O Tabtreated and untreated Supanet and ‘no net’ treatments were evaluated against sandflies within the laboratory by tunnel tests and in semi-field conditions in the greenhouse model for their efficacy. Results: All bednets allowed entry of P. duboscqi sandflies and subsequent blood-feeding. Olyset net’s blood feeding inhibition was significantly higher than that of Supanet in the laboratory but not in semi-field condition. Of the LLINs, only Olyset net had sandflies that could not feed significantly more than those of Supanet. Additionally, no significant efficacy difference was observed between LLINs washed 20x and unwashed ones. The only significant difference noted in number of sandflies that were found dead or paralyzed within bednets in the semi-field condition was between Olyset and K-O Tab treated Supanet. In the laboratory, unwashed Olyset had a significantly higher number of sandflies killed than all other bednet treatments. Conclusion: Olyset net use in areas where sandflies are nuisance biters and/or disease vectors could be more beneficial in preventing sandfly bites than other tested bednets. It is recommended that mesh sizes of LLINs should be smaller for control of sandflies than those used for control of mosquitoes.
ABSTRACT
Background & objectives: In order to understand sandfly bionomics, vector species identification, and to develop methods for sandfly control, there is a need to sample sandflies in any particular habitat. This survey was aimed at determining the best method of sampling Phlebotomus (Phlebotomus) duboscqi (Diptera: Psychodidae) in the field. Methods: Different animal baits and CO2-baited CDC light traps were used to attract sandflies released in an insect-proof screen-house located in the sandfly’s natural habitat in Marigat, Baringo district of Kenya. Results: Attraction of hungry P. duboscqi female sandflies by the goat (Capra hircis) was significantly higher than that of hamster (Mesocricetus auretus), Nile grass rat (Arvicanthis niloticus), gerbil (Tatera robusta) and chicken (Gallus domestica). However, two rodent species, A. niloticus and T. robusta did not differ significantly. A linear regression analysis of weights of animal baits and number of sandflies attracted revealed an insignificant result. The fluorescent dyes used to distinguish sandflies of different day experiments seemed not to influence the sandfly numbers in relation to the studied sandfly behaviour. Interpretation & conclusion: The similar attraction pattern of P. duboscqi in semi-field environment by CO2-baited CDC light trap and the goat provides hope for solution to the problem of fast dissipating dry ice (CO2 source) in the field. Goats can, therefore, also be utilized as deflectors of vectors of cutaneous leishmaniasis from humans in zooprophylaxis in Leishmania major endemic areas where the sandfly is found.
ABSTRACT
Background & objectives: Zooprophylaxis is a strategy that can control malaria by attracting mosquitoes to domestic animals that act as dead-end hosts. The objective of this study was to establish the effects of zooprophylaxis and long-lasting insecticidal nets (LLINs) on malaria transmission in an agro-based ecosystem with seasonal transmission. Methods: The mosquito samples were collected indoors using the space spray catch method before and after intervention between October 2005 and March 2006 to determine the mosquito densities and the feeding patterns of Anopheles spp in Mwea, Kenya. Results: A total of 4148 mosquito samples were collected, out of which 11 (0.2%) were tested positive for sporozoites. Ten were Anopheles gambiae species and one was An. funestus species. Results on blood meal ELISA showed that in the household categories that used bednets and kept one cow there was a decrease in relative change ratio (post-/pre-intervention) of 87.5 and 19.6% (p <0.05) in human and cattle blood intake respectively. For households that kept 2–4 cattle and used bednets, there was a decrease in cattle blood index (CBI) by 61.9% and an increase in human blood index (HBI) by 2%, which was not significant (p >0.05). In households with >4 cattle and bednet, there was significant reduction (p <0.05) in CBI of 37.5% as compared to the reduction of 10.3% in HBI. The ratios of man biting rates (MBR) decreased significantly, as you move up from households with one cattle with or without LLINs to households with more than four cattle with or without LLINs with a regression coefficient of –0.96; SE = 0.834; p = 0.017. Similarly, the HBI decreased significantly with the regression coefficient of 0.239; SE = 0.039; p = 0.015 (p <0.05) especially in households with >4 cattle. Interpretation & conclusion: This study demonstrated that there were additive effects of zooprophylaxis and LLINs in the control of mosquito density and reduction of human risk to the mosquito bites. However, in Integrated Vector Management (IVM), the number of animals per household should not be more than four.
ABSTRACT
BACKGROUND AND OBJECTIVES: An entomological survey was conducted to determine the relationship between malaria and lymphatic filariasis transmission by Anopheles gambiae s.l. and An. funestus in two inland villages along the Kenyan coast. METHODS: Mosquitoes were sampled inside houses by pyrethrum spray sheet collection (PSC). In the laboratory, the mosquitoes were sorted to species, dissected for examination of filarial infection and the anophelines later tested for Plasmodium falciparum circumsporozoite proteins by an enzyme-linked immunosorbent assay (ELISA). RESULTS: From a total of 2,032 female mosquitoes collected indoors, An. gambiae s.l constituted 94.4% while the remaining 5.6% comprised of An. funestus and Culex quinquefasciatus. None of the Cx. quinquefasciatus was positive for filarial worms. P. falciparum sporozoite rate for An. gambiae s.l. from both villages was significantly higher than Wuchereria bancrofti infectivity rate. Similarly, the entomological inoculation rate for An. gambiae s.l. was significantly higher than the corresponding W. bancrofti infective biting rate and transmission potential for both the villages. Mass treatment of people with filaricidal drugs in Shakahola in the ongoing global elimination of lymphatic filariasis campaign seemed to have reduced the indices of filariasis transmission but had no effect on malaria transmission. INTERPRETATION AND CONCLUSION: These results indicate the intensity of malaria transmission by anophelines to be much higher than that of lymphatic filariasis in areas where both diseases co-exist and re-emphasise the need to integrate the control of the two diseases in such areas.