Studies were commenced to collect and identify the phlebotomine sandflies found in Nairobi. These studies were also aimed at determining their numbers as well as assessing the effects of seasonal changes on the sandfly population. Four trapping methods, namely, light traps, sticky traps, aspiration and human bait were employed. Eight species and one undescribed species were recorded over a period of 6 months. The identified species included Phlebotomus guggisbergi (Kirk and Lewis), P. rodhaini (Parrot), Sergentomyia adleri (Theodor), S. harveyi (Heisch, Guggisberg and Teesdale) and S. bedfordi (Newstead) and an undescribed species. Most of the sandfly species trapped showed seasonal prevalence. The seasonal variation was closely related to the weather conditions. Sandflies were found in termite mounds, animal burrows, caves and dugouts some of which were near human habitations. Termite mounds and animal burrows were the most preferred habitats.

A number of natural and man-made habitats in Marigat area of Kenya were surveyed for sandflies in 1985/86. Of the 98,573 adult sandflies collected, 2.7 % belonged to the genus Phlebotomus and 97.3% to Sergentomyia. Relative abundance of sandflies of the genus Phlebotomus was four times higher in burrows than in termite hills, while sandflies of the genus Sergentomyia collected from termite hills were twice as numerous as those from burrows. Termite hills had the highest sandfly population compared to other sites, followed by tree holes and animal burrows. Fifteen species were identified, of which five belonged to Phlebotomus and 10 to Sergentomyia. The most abundant and widespread species were Sergentomyia antennatus, S. bedfordi, S. ingrami, Phlebotomus martini, S. schwetzi, S. africanus and P. duboscqi. Sandflies of both genera were present for the greater part of the year. Most species of sandflies decreased in numbers during the dry season. High population densities of sandflies were recorded during the wet period. Correlations between relative abundance of sandfly vectors of leishmaniases and rainfall were positive. However, none of the correlation coefficients was statistically significant.

Field investigations were carried out in northern Nigeria to determine the prominent natural habitats of phlebotomine sandflies. Two biotopes, termite hills and rock crevices, were identified as the major habitats with the termite hills being the most significant. All the 12 species (Phlebotomus duboscqi, P. rodhaini, Sergentomyia antennula, S. bedfordi, S. africana, S. schwetzi, S. ingrami, S. adleri, S. clydei, S. buxtoni, S. affinis and S. christophersi) identified in this study came from this source. Only a small number of samples representing a few species were collected from the three other habitats (tree holes, animal burrows and a cave) investigated. The distribution of the sandflies was found to be influenced by the availability of suitable biotopes and physico-chemical composition of the soil.

Investigations of the phlebotomine sandflies fauna in a visceral leishmaniasis focus of Aba Roba in Ethiopia were carried out. This resulted in finding Phlebotomus celiae for the first time in the country. Previously, this species was incriminated as a vector of visceral leishmaniasis in Kitui, Kenya where the disease is endemic. It is possible that P. celiae has a wide distribution covering areas of similar ecological niches as those of its first description.

Adults of various phlebotomine sandfly species were obtained from leishmaniases endemic foci in Kenya using several trapping methods. Ten species were successfully reared from egg to adult in the laboratory; and large colonies of Sergentomyia schwetzi, S. bedfordi, S. ingrami, S. antennatus, S. adleri, S. garnhami, Phlebotomus duboscqi and P. martini established. Generally, the development of Phlebotomus spp. from egg to adult took longer (54.7–57.2 days) than Sergentomyia spp. whose developmental time with the exception of S. garnhami, varied between 36.5–42.3 days.

Studies on breeding sites of Phlebotomus duboscqi, a vector of Leishmania major, were intensified in Marigat, Baringo District, Kenya using the soil incubation technique, following the previously successful attempt to look for sandfly breeding sites. Soil samples obtained from nest areas of the animal burrows yielded Phlebotomus duboscqi and Sergentomyia ingrami. These two species had been shown to harbour L. major parasites inside animal burrows. Other phlebotomine sandflies recovered from these same breeding sites included P. martini, P. rhodhaini, S. bedfordi, S. africanus, S. antennatus and S. graingeri

Five (Sergentomyia antennatus, S. garnhami, S. schwetzi, S. ingrami and S. adleri) of the six species of sandflies fed on mammalian blood containing cultured Leishmania donovani promastigotes on day 0, were able to feed through cockerel skin membranes at 5.5, 10, 34.3, 45.7 and 95% feeding rates, respectively. Sergentomyia bedfordi was able to feed on mammalian blood only through a lizard skin membrane at 100% feeding rate. Promastigotes were found in 9.3, 25 and 37.5% of S. schwetzi, S. adleri and S. ingrami respectively, dissected on days 3–9.

The results open way for artificial feeding of Kenyan sandflies on mammalian blood through membranes, and indicate that it is necessary to select the type of membrane depending on sandfly species. The ability of L. donovani to develop in Kenyan sandflies is being investigated to experimentally establish and confirm the importance of various genera and species in the epidemiology of leishmaniasis.

The vectors of Leishmania major were investigated in Marigat, Baringo District, Kenya, a focus of both visceral and dermal leishmaniases. These studies resulted in the discovery of the resting sites of Phlebotomus duboscqi, a known vector of L. major, and of alternate principal resting sites of Phlebotomus martini, a known vector of visceral leishmaniasis. Furthermore, Sergentomyia ingrami was incriminated as a possible vector of L. major among susceptible rodents inside burrows. Trapping methods which have resulted in the discovery of the resting sites of these phlebotomine sandflies are presented in this paper.

The paper reviews advances in our understanding of the vectorial capacity and vector–parasite relationship in Kenyan sandflies since the early 1900s (when sandflies were first reported in Kenya). Of the 38 species of sandflies known to occur in Kenya to date, three (Phlebotomus pedifer, P. martini and P. duboscqi) can naturally carry biochemically and serologically confirmed Leishmania (aethiopica, donovani and major, respectively) and 12 (Phlebotomus rhodhaini, Sergentomyia garnhami, S. squamipleuris, S. africanus, S. kirki, S. ingrami, S. antennatus, S. bedfordi, S. schwetzi, S. affinis, S. graingeri and S. clydei) carry various flagellates of biochemically or serologically unknown character.

Current research on naturally infected wild-caught sandflies indicates that L. aethiopica promastigotes have close association with structures resembling a peritrophic membrane and invade P. pedifer gut cells. Promastigotes invade the malpighian tubules of S. garnhami and S. antennatus.

Studies on laboratory-reared sandflies show that P. martini is susceptible to L. donovani amastigotes and that cultured promastigotes of L. donovani can survive in the guts of S. schwetzi, S. ingrami and S. adleri.

Experimental infection of sandflies with Leishmania is discussed and priorities for laboratory work set.

Investigations on sandfly breeding sites in Marigat, Baringo District, in Kenya were carried out using a soil incubation technique. Soil samples from natural resting sites were collected, incubated and observed daily for emerging adult phlebotomine sandflies. This technique proved to be the best in the recovery of phlebotomine sandflies from known resting sites. Ten sandfly species were recovered from soil collected from animal burrows and termite hills.

Studies of the epidemiology of visceral leishmaniasis in the West Pokot focus have revealed that Sergentomyia bedfordi, S. antennatus and S. schwetzi are the most abundant sandfly species. The latter have been shown to feed mainly on lizards. Phlebotomus martini was encountered in termite hills in the ventilation shafts, and showed an even distribution among the termite hills throughout the district where kala-azar cases were detected. Investigations into the relationship between termite hills and the presence of kala-azar cases in various homes were carried out. All homes afflicted with kala-azar had a termite hill or hills within a 10-m radius. The period of time spent in own homestead by each kala-azar case was to establish if each kala-azar patient contracted the disease in the focus of investigation.

Sandflies caught from termitaria at Tseikuru (Kitui District) and Masinga (Machakos District) were dissected and examined for the presence of Leishmania. Leishmanial parasites were found in the guts of 12 out of 112 Sergentomyia garnhami from Tseikuru and in 2 out of 48 S. antennatus from Masinga. Five of the 12 S. garnhami and 1 of the 2 S. antennatus had leishmanial parasites in the malpighian tubules. Electron microscopic investigations revealed that in the malpighian tubules of S. garnhami the parasites were either free in the lumen or in close contact with the basement membrane.

Wild-caught phlebotomine sandflies were captured from rock crevices and termite hills and released into feeding cages containing various species of laboratory animals, to find suitable hosts for feeding flies for experimental or breeding purposes. Flies captured from rock crevices did not feed as well as those human-baited at termite hills. The ubiquitous species from the termite hills was Phlebotomus martini, the major vector of kala-azar in the study area (Machakos District of Kenya). This anthropophilic species feeds readily on the mammalian laboratory animals. Cooling flies before feeding stimulated them to feed.