Studies on the vectors of leishmaniasis in Kenya: phlebotomine sandflies of Sandai location, Baringo district.

Adults of phlebotomine sandflies were collected from natural and man-made habitats in Sandai area of Baringo district using sticky and CDC light traps. Three sandfly species belongings to the Phlebotomus genus and eight species belonging to the Sergentomyia genus were recorded in the area. These flies fall into "perennial" group as they appeared to breed throughout the year. During the dry season there was an increase of sandfly densities in animal burrows and termite mounds, the main sandfly breeding places. Tree holes and human habitations constituted the major sandfly resting places during the wet season. Sandflies of the Phlebotomus genus were more collected in termite mounds and inside houses using CDC light traps, whereas in animal burrows they were more collected by sticky traps than by CDC traps. Sandflies of the Sergentomyia genus were equally collected by sticky traps and CDC light traps. However, in animal burrows and in human habitations, sandflies were more collected by CDC light traps than by sticky traps. On statistical analysis, CDC light traps seemed to be effective inside houses and in animal burrows. In termite mounds both traps yielded uniform results.

Effects of permethrin-treated screens on phlebotomine sand flies, with reference to Phlebotomus martini (Diptera: Psychodidae).

Effects of permethrin-treated screens on the sand fly, Phlebotomus martini Parrot, a vector of visceral leishmaniasis in Kenya, were evaluated after the eighth treatment. Screens treated with 0.50 g/m2 of permethrin 20% emulsifiable concentrate were fitted inside houses and re-treated every 6 mo from August 1989 to December 1993. Before application of the treated screens, a geometric mean of 0.83 P. martini were collected per trap night inside houses, whereas after the eighth treatment only 0.05 sand flies were caught. P. martini abundance was reduced by 88.8%. Analysis of the effects of treated screens on the total sand fly population (all species) indicated that 1.79 sand flies were collected per night per house before deployment of treated screens, whereas 0.16 flies were caught after the eighth treatment. The percentage of sand fly reduction inside treated houses increased with successive treatment of the screens, and a reduction of 81.4% was observed after the eighth treatment. Permethrin-treated screens did not reduce the sand fly engorgement rate inside houses.

Cutaneous leishmaniasis in Kenya: Sergentomyia garnhami (Diptera Psychodidae), a possible vector of Leishmania major in Kitui District: a new focus of the disease.

Investigations on phlebotomine sandflies in Tseikuru, Kitui District, Kenya were carried out to determine the vectors of Leishmania major. Sandflies were trapped from animal burrows over a period of one year using castor oil-smeared sticky traps. Nineteen phlebotomine sandfly species were identified and their prevalence in this habitat determined. Dissections on the parous sandflies resulted in the isolation of Leishmania parasites from Phlebotomus martini and Sergentomyia garnhami. The isolated parasites were cultured in NNN medium and were consequently mass cultured in RPMI medium for biochemical characterisation. The parasites from S. garnhami were typed as Leishmania major.

A bioassay to evaluate the efficacy of permethrin-impregnated screens used against phlebotomine sandflies (Diptera: Psychodidae) in Baringo District of Kenya.

Control of phlebotomine sandflies remains a difficult problem throughout the world because of the insects' very highly specialized breeding sites. Use of insecticides remains one effective methods for managing sandflies. The present studies were conducted to establish how long permethrin impregnated wall cloth remains effective against sandflies. Cotton cloth, impregnated with permethrin (0.5g/m2) were hung inside experimental houses in Baringo District, Kenya, for the control of sandflies. Small pieces of cloth were cut off from the screen every month for 12 months, and bioassayed against sandflies. The cloth was found to remain effective against sandflies for 6 months.

Evaluation of the residual efficacy of permethrin-impregnated screens used against mosquitoes in Marigat, Baringo district, Kenya.

Insecticide-impregnated screens and bednets are gradually finding wider use in malaria control programmes. The efficacy of these devices is dependent on the method of application, the acceptability by the people and effectiveness of the insecticide used. The present studies were carried out to determine the duration of the effectiveness of a permethrin-impregnated wall cloth (Mbu cloth) used in the Marigat area of Baringo District, Kenya in order to ensure its effective use. Cotton cloth impregnated with permethrin was hung inside an experimental house in Marigat and small pieces cut off each month for bioassay against mosquitoes over a twelve month period. The wall cloth remained effective for 6, 4 and 10 months against Anopheles gambiae s.l. the known vector of malaria, Culex quinque-fasciatus and Aedes aegypti, respectively.

Studies on the epidemiology of leishmaniasis in Kenya: flight range of phlebotomine sandflies in Marigat, Baringo District.

A study on the flight range of phlebotomine sandflies using the mark-release-recapture technique was undertaken in Marigat, Baringo District, Kenya, to determine the distance sandflies are able to travel and assess their importance in disease transmission. Over a period of 17 months, a total of 108,429 sandflies collected from their natural habitats were marked and released from a central point in a valley. Of these, 842 (0.8%) sandflies comprising 11 species were recaptured. Ninety-five percent of the recaptured sandflies were recovered within a radius of 50 m from the release point and 54% within a radius of 10 m. Two Sergentomyia ingrami females were recaptured at a distance of 1000 m from the release point.

Distribution of sandflies (Diptera: Psychodidae) in three vegetation habitats in the Marigat area, Baringo District, Kenya.

A total of 4,467 phlebotomine sandflies representing nine species and two genera were collected using polythene material coated with castor oil in three vegetation types in Marigat area from February to May 1986. Sandfly relative abundance was greatest in the closed-canopy forest (61% of total catch), followed by the open-canopy woodland (38%) and the thicket (1%). Nine species of sandflies were collected in both the closed-canopy forest and the open-canopy woodland. The thicket yielded only four species. The sandfly population in the vegetation was composed of Sergentomyia bedfordi (61%), S. antennatus (31%), S. ingrami (3%), S. schwetzi (2%), and S. africanus (1%). Plebotomus species rarely occurred in the study area. In the closed-canopy forest and the open-canopy woodland, female S. bedfordi were most abundant during the dry season, while males predominated during the wet period. Inversely, more male S. antennatus were collected during the dry season, while females predominated in the open-canopy woodland during the wet season. In the closed-canopy forest, male S. antennatus outnumbered the females during both dry and wet seasons. Both S. antennatus and S. bedfordi increased in abundance during the dry season.

Epidemiology of leishmaniases in Kenya. Natural host preference of wild caught phlebotomine sandflies in Baringo District, Kenya.

Host preference of wild caught phlebotomine sandflies was studied in Marigat, Baringo District, Kenya, an endemic focus for both Leishmania donovani Laveran & Mensel and L. major Yakimov & Schokhov using precipitin test of blood meals. Sandflies of the Phlebotomus Rondani & Berte and Sergentomyia Franc & Parrot genera were encountered blood fed and resting in nine different habitats which were investigated. Analysis of their blood meals revealed a distinct host preference between the Phlebotomus and Sergentomyia genera. A distinction of host preference within species of each of the two genera was also observed. Furthermore, certain resting habitats from which the bloodfed sandflies were collected appeared to be favoured by specific sandfly species. It was observed that most of the wild hosts such as lizards and rodents except the hippopotamus, shared the same resting habitats with the sandflies. It was also observed that the man-biting sandflies preferred to rest outdoors after feeding. Domestic animals and man were the favoured hosts of vectors of both visceral and cutaneous leishmaniases, thus introducing an element of zooprophylaxis.