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: Malaria in urban and highland areas is emerging as a significant public health threat in Kenya which has seen a dramatic increase in malaria transmission in low risk highland areas. The objectives of the study were to find and incriminate potential vectors of malaria in Kibera, Nairobi. Methods: One hundred and twenty houses within Lindi area of the southern central section of Kibera slum in Nairobi were chosen randomly and global positioning system (GPS) mapped. Day resting indoor mosquitoes were collected from January 2001 to December 2003. Larvae were collected between 2002 and 2004 and reared in the insectary to adults. Results: A total of 176,993 mosquitoes were collected. Out of this, 176,910 were Culex fatigans and 83 were Anopheles gambiae s.l. Mosquito population peaked during the long rains in April to May and the short rains in November and December. Blood meal analysis of An. gambiae s.l. female mosquitoes revealed 0.97 human blood index. No mosquito was found positive for Plasmodium falciparum sporozoites. Anopheles gambiae s.l. mosquitoes were found breeding in polluted water and 95% of the larvae were identified as An. arabiensis. Interpretation & conclusion: Anopheles gambiae s.l., malaria vector is present in Nairobi and it breeds in polluted water. Anopheles arabiensis is predominantly preferring humans as blood meal source, thus, showing ecological flexibility within the species.
ABSTRACT
Background & objectives: Bancroftian filariasis in Kenya is endemic in coastal districts with an estimated number of 2.5 million people at risk of infection. The main mosquito genera involved in transmission of Wuchereria bancrofti in these areas are Anopheles, Culex and Mansonia. The study was envisaged to compare the infectivity rates of Bancroftian filariasis vectors between the high transmission (wet) and the low transmission (dry) seasons. Methods: Mosquitoes were sampled from houses and compounds from two study sites, Gazi and Madunguni, on the Kenyan coast. Day resting indoor collection (DRI), pyrethrum spray catch (PSC) and CDC light traps were used to collect mosquitoes. After identification, female mosquitoes were dissected to search for W. bancrofti III stage larvae. Results: A total of 1832 female mosquitoes were dissected. Infectivity rates of vectors in Madunguni were 1.49 and 0.21% in wet and dry seasons respectively, whereas in Gazi, these were 1.69 and 0%, respectively. There was a significant difference in the infectivity rates between the two seasons in both Madunguni and Gazi villages (p <0.05). Anopheles gambiae s.l. was the main vector in both study sites followed by Culex quinquefasciatus and An. funestus. Conclusion: There was a difference in infectivity rates of Bancroftian filariasis vectors between the wet and dry seasons. The abundance of An. gambiae s.s. during the transmission season could be responsible for the increased infectivity rates of vectors in this season.
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.