Studies have been made of the bionomics and ecology of Aëdes aegypti (L.) entirely under natural conditions and in its natural habitats on the Kenya coast.Development from egg to adult under conditions approximating as nearly as possible to those in nature took a minimum of eight days and a maximum of twenty-five.Males were in excess of females, in the proportion seventeen to ten, from eggs hatched in natural breeding places.Although the mosquito may be able to propagate in houses, adults from outside habitually enter premises. If this entry is for egg-laying, then eradication by domestic larval control alone, although reputedly achieved elsewhere, is not possible under conditions obtaining in the coastal belt of Kenya. Windowtrap captures, however, indicate that the entry may not be for the purpose of egg-laying.The seasonal reduction of both larvae and adults in houses during the hot, dry months of February and March is attributed to a combination of the absence of breeding places outside and the shorter life span of the mosquito at this time.It is shown that both sexes enter and leave native huts throughout the 24-hour period, but the movement is confined almost wholly to the hours of daylight. The flight from houses is much reduced in the cool months (July and August). This corresponds with the season when most enter.

No abstract

Variation in daily egg counts, and in counts for samples of the same stool, was investigated in children with Schistosoma mansoni and Ascaris lumbricoides infections, using a thin smear technique. The results indicated that counts vary according to the stool consistency; drier stools from the same person producing up to seven times greater counts than wet ones. The sensitivity of the technique was tested in schoolchildren living in an endemic S. mansoni area, and found to detect all infections with intensities of greater than 50 eggs per gram of stool, after examination of only one slide containing 40mg stool. The sensitivity varied with the intensity of infection. The relevance of these findings to diagnosis in field situations is discussed.

In this paper a list, with brief notes on prevalence, behaviour and habitat is given of 121 species, sub-species and varieties of mosquitos taken in the last 12 years during field work on the Kenya coast. Two species and one sub-species of the mosquitos found are not yet described. Notes on variation have been included for species that show interesting features in this respect and the distribution of the species in East Africa is also included where it is of interest.

A two-year follow-up was conducted in children who had been the subjects of a six-month double-blind trial in the single-dose treatment of Schistosoma haematobium infection. The trial had assessed therapeutic efficacy of three oral preparations-praziquantel 40 mg/kg, metrifonate 10 mg/kg, and the 'combination' (concurrent niridazole 25 mg/kg and metrifonate 10 mg/kg administration). Reduction in urinary egg excretion remained high up to follow-up at two years, based on a comparison of pre- and post-treatment geometric mean counts-praziquantel 96.9% (n = 96 at six months, 51 at two years); the 'combination' 93.9% (n = 97 at six months, 48 at two years); and metrifonate 90.3% (n = 92 at six months, 49 at two years). The differences in percentage reduction were not significant (p greater than 0.1). However, a significantly greater reduction in egg output was produced by praziquantel (81.7%) and the 'combination' (82.5%) than by metrifonate (54.2%), on comparing pre- and post-treatment arithmetic mean counts (p less than 0.01). A significantly smaller percentage of subjects were excreting greater than or equal to 125 ova/10 ml urine two years after treatment with praziquantel (10.3%), compared to treatment with the 'combination' (25.7%) and metrifonate (35.8%) (p less than 0.01). The cure rate was significantly higher in the praziquantel group (47.4%) compared to the 'combination' (24.7%) and metrifonate (17.4%) groups, for the six to 24-month follow-up period (p less than 0.001). The pattern and level of transmission had contributed to the long-term efficacy recorded in this study.