Additions to the Mosquito Fauna of Union Island,Saint Vincent and the GrenadinesAccessibility Summary:In accordance with Title II regulations this content meets all points of exemption as Archived web content and/or Preexisting conventional electronic documents.

The mosquito Haemagogus equinus is a known vector of yellow fever (YF) in central America. Seasonal abundance, daily biting activity and the age composition of adult Hg.equinus female populations were monitored weekly during 1981-82 by human collectors on the ground at Point Gourde Forest, Chaguaramas, 16 km west of Port of Spain, Trinidad. 2. Landing collections of Hg.equinus showed diurnal activity from 06.00 to 20.00 hours (suntime), with a single peak between 08.00 and 14.00 hours. 3. Overall, 5.6% of Hg.equinus were collected during the dry season (December-April) and 94.4% during the wet season (May-November). 4. Mean density of Hg.equinus in relation to man ranged from 0.35/man-day in February to 133/man-day in July, with averages of 2.8 in the wet season, 36.9 in the dry season and 22/man-day for the whole year. 5. Monthly parous rates averaged 62.1% (range 0-88%); 2.8% of females were 2-pars, another 2.8% were 3-pars, but no older females of Hg.equinus were found (sample size 467). 6. These age-grading data indicate that Hg.equinus females have relatively short life expectancy and hence low vector potential, which may help to explain why YF virus has seldom been isolated from this vector species.

1. Age composition, seasonal abundance and diel patterns of landing activity of the sylvan vector of yellow fever Haemagogus janthinomys Dyar were monitored weekly during 1981-82 by human collectors on the ground at Point Gourde in Chaguaramas Forest, 16 km west of Port of Spain, Trinidad.2. Landing collections of Hg.janthinomys showed only diurnal activity, from 06.00 to 18.00 (sunrise to sunset, universal time), with a single peak of activity between 10.00 and 16.00 hours.3. Densities of Hg.janthinomys were about 6 times greater during the wet season (May-November) than during the dry season (December-April); the annual Williams' mean landing rate on two collectors was 9.3 per day.4. Monthly parous rates averaged 59% (range 0-86%) and some females were up to seven-pars. Retained eggs (range 1-21, mean 7.7/female) were found in the ovaries of 1.3% of landing females, all of which had stage I ovarian follicles for the next gonotrophic cycle. Hence blood-feeding is not inhibited by egg retention, which might promote transovarial transmission of virus. Implications of these findings are discussed in relation to yellow fever epidemiology.

Seasonal and spatial distributions of the arbovirus vector mosquito Culex (Melanoconion) caudelli Dyar and Knab (Diptera: Culicidae) in the Aripo-Wallerfield forest, Trinidad, were studied by collecting mosquitoes attracted to mouse-baited traps in forest, ecotone and savannah, one day per week throughout the year, 98% of the Cx caudelli mosquitoes were collected during the wet season, with a significant positive correlation between rainfall and mosquito catch. The reverse occurred during the dry season. Cx caudelli displayed a preference for the ecotone where 67% were collected, while 32% and 1% were collected in the forest and savannah respectively.

The occurrence of the first seven cases of visceral larva migrans in Trinidad and Tobago is described. All cases occurred in children of the same family. The ELISA test was used to confirm the clinical diagnosis.

A colony of Toxorhynchites moctezuma was established at the Caribbean Epidemiology Centre in Trinidad in 1984. Toxorhynchites moctezuma was maintained in cages with high humidities. Eggs were deposited most frequently in a cut bicycle tire containing water. A minimum of 42 h was required for hatching, but 94% hatched between 43 and 51 h. Aedes aegypti larvae were supplied as prey. Larval development times varied with the quantity of prey offered, but when fed ad lib, peak developmental time was 18 days. Mean pupal developmental time was 5.5 days. Although only 12% of larvae survived to pupation in 3 years of production, our experience indicates this species would be a likely candidate for mass production and release.

The seasonal incidence and diel oviposition patterns of sylvan Haemagogus celeste and Hg. leucocelaenus in the Pt. Gourde Forest, Trinidad, were monitored weekly for 53 consecutive weeks using conventional ovitraps. During the dry season peak oviposition by Hg. celeste occurred between 10.00 and 12.00 hours, and that by Hg. leucocelaenus between 12.00 and 14.00 hours; during the wet season peak oviposition by both species occurred between 12.00 and 14.00 hours. Diurnal patterns of oviposition were observed for both species during the wet and dry seasons. The numbers of ovipositions and of eggs laid during the wet season were, for both species, significantly higher (P greater than 0.001) than those observed during the dry season.

Diel patterns of oviposition of sylvan Haemagogus equinus in the field in Trinidad, West Indies, were monitored weekly for 53 consecutive weeks using standard ovitraps. During the wet season (September to November 1981 and May to September 1982) a large well-defined unimodalpeak (comprising 97% of all eggs laid and 89% of occurrences) occurred at 12.00–14.00 hours, four to six hours before sunset. During the dry season (December 1981 to May 1982), two small less-well-defined peaks occurred at 10.00–12.00 and 14.00–16.00 hours (comprising 4·9% of eggs laid and 14% of occurrences). A diurnal oviposition pattern was observed when the wet and dry season data were combined. The number of eggs and occurrences found during the wet season was significantly higher (P > 0·001) than that observed during the dry season.

The diel biting periodicity of the arbovirus vector Culex (Melanoconion) caudelli Dyar and Knab (Diptera; Culicidae) in the Aripo-Wallerfield forest, Trinidad, was studied by collecting mosquitoes attracted to mouse-baited traps at 2-hourly intervals during eight 24 h periods. Biting females of Cx caudelli were collected during all night-time hours, 18.00-06.00 hours, with an overall unimodal pattern, i.e. one well-defined peak between 22.00 and 04.00 hours. This contrasts with previous reports that Cx caudelli is diurnally active. During the four moon phases, the period of peak biting activity varied from 22.00 to 24.00 hours at fullmoon, from 22.00 to 04.00 hours at first quarter, and from 24.00 to 02.00 hours at new moon and last quarter phases. The number of mosquitoes collected varied significantly with moon phases, the highest (152/24 h) being collected in the first lunar quarter and the lowest (71/24 h) in the last lunar quarter. Cloud cover and rainfall had no significant effect on the diel biting periodicity of Cx caudelli.

The diel oviposition periodicity of sylvan Haemagogus janthinomys Dyar in the Pt. Gourde Forest, Trinidad, West Indies was monitored weekly for 53 weeks using conventional ovitraps. During the wet season (September to November 1981 and May to September 1982) a large well-defined unimodal peak occurred six to eight hours after sunrise (comprising 94% of eggs laid and 91% occurrences). During the dry season (December 1981 to May 1982), a small less-well-defined peak occurred two to four hours before sunset (comprising 6% of eggs laid). The combined data showed a diurnal oviposition pattern with eggs laid from noon to sunset. The numbers of eggs and of used ovitraps found during the wet season were significantly (P less than 0.001) higher than those found during the dry season.

the canopy of the forest. Similarly, the bamboo pots were'placed on the opposite side of the -ovitraps starting at ground level and at approximately every 60 cm thereafter' reaching toa height of 720 cm. Bamboo pots varied in lengths from 15 to 30 cm. Likewise, their diameters varied between 5 and 8 cm. At Cachipe, 24 ovitraps were attached to the trunk of a crappo tree, but the canopy here was open due to greater logging operations in this area' During the dry season, both the ovitraps and bamboo pots were half-filled with water, but early in the rainy season (June), both types of containers became easily filled and overflowed with water during heavy rains so that the amount of water added during the rest of the rainy season was reduced to about one-third of the container. Ovitraps and bamboo pots were serviced weekly when each oftheir contents were emptied into a basin, ' and all larvae collected were placed in vials with labels giving pot number, date and height. Collections at Saunders Road started January 25 and ended September 9, 1979' At Cachipe colIections started January t7, t979 and ended January 9, 1980. The results are presented on Fig. 1. At Saunders Road 49 pots (25 ovitraps and24 bamboo pots) were found positive for Tx. moctezurna larvae. Larvae were collected from ovipots at ground level and throughout the verticarange of this tree station up to a height of 870 cm. However, 17 of the 49 positive results $4.7%\ were obtained with pots placed within 120 cm of ground level. At Cachipe, where collections were made over a period of one year, 25 ovitraps were positive and these were also found throughout the vertical range up to height of 720 cm. However, tB (53%) were found within 120 cm of ground level. Comparison between collections in ovitraps and those ofbamboo pots were not possible as the latter were larger anct held more water with a consequence that overflow in ovitraps was more frequent resulting in the greater loss of Tx. moctezumo eggs. The failure to collect Tx. rnoctezurno larvae in ovitraps from the last week of May through June might possibly be due to the heavy rainfall at this time resulting in the overflowing of containers. The ability of Tx. moctezuma tn locat'e artificial containers near the ground suggest it might be a good biocontrol agent for Aedes o'egypti. k should be noted however, that Focks et 319

The effects of a mass chemotherapy programme using spaced doses of diethylcarbamazine citrate on Wuchereria bancrofti microfilaraemias and vector infection rates were studied in an isolated rural community of 650 people in north Trinidad where a microfilaria rate of 15% had previously been recorded. A single oral dose of 6mg/kg body weight was given at monthly intervals for one year. After 6 months, 79% (52/66) of persons previously microfilaraemic had become negative. After 12 months the negative proportion had increased to 90% (63/70). The geometric mean microfilaria density of those still microfilaraemic was reduced from 19.7 to 4.6 per 100mm3 of blood. Of 147 initially negative persons, none had become positive following treatment. Filarial infection rates in Culex quinquefasciatus from randomly sampled houses fell from 6.4% to zero; in houses where occupants with microfilaraemia had been identified before treatment, the rate was reduced from 15.8% to zero. In a supplementary study, however, weekly collections from one initially positive house showed a rapid decline in the vector infection rate from 43% to 2% after three months but an additional 3 months elapsed before the index reached zero. There was negligible microfilarial uptake by the vectors from residual low-density microfilaraemias (<10 microfilariae per 100mm3 of blood) after chemotherapy.

Following the discovery in two villages in Montserrat of five individuals who were passing Schistosoma mansoni ova in their stools, a house to house survey was undertaken in November 1978 to determine the prevalence of the infection. From 158 persons residing in the two villages 137 faecal samples were received. Of these 14% were positive for S. mansoni ova. The enzyme linked immunosorbent assay (ELISA) was performed on finger-prick blood samples collected on chromatography paper. In the ELISA 16% of the 132 persons tested were positive. In comparison with the stool examination, the ELISA showed a 53% sensitivity and a 92% specificity. It was recommended that the individuals passing schistosome eggs should be treated.