Elisha S Tikasingh

Ecology of the rodents, Proechimys guyannensis trinitatis and Oryzomys capito velutinus, on Trinidad

This study deals with ecology of two rodents, Proechimys guyannensis trinitatis and Oryzomys capito velutinus , representing nearly 70 per cent of the mammals captured in Turure Forest, Trinidad. Maximum population densities of each species were 5.5 and 9.2 animals per acre, respectively; mean values computed for each home range were 0.425 and 1.012 acres, respectively. Marked individuals of Proechimys have been retrapped for 20 months and others were kept in the laboratory for 3.5 years. O. c. velutinus may live up to 28 months in captivity but individuals caught in the wild have not been retrapped for longer than 12 months. Sex ratios, laboratory breeding, mortality due to laboratory processing and transportation, cutaneous parasites, and the haemoparasites of these two small mammals are discussed.

Suppression of Aedes aegypti by predatory Toxorhynchites moctezuma in an island habitat

Abstract. Larval populations of the mosquito Aedes aegypti were suppressed by predatory Toxorhynchites moctezuma mosquito larvae released systematically in a village on Union Island (Saint Vincent and the Grenadines) during March‐December 1988.

A laboratory investigation of mosquito larval predation by Toxorhynchites moctezuma on Aedes aegypti

ABSTRACT. 1. Functional responses of predatory Toxorhynchites moctezuma (Dyar & Knab) larvae feeding on Aedes aegypti (L.) larvae (Diptera: Culicidae) were found to be type II of Holling (1959) and Rogers (1972).

Observations on the seasonal incidence and diel oviposition periodicity of Haemagogus mosquitoes (Diptera: Culicidae) in Trinidad, W.I.: Part I. Haemagogus janthinomys Dyar

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 prevalence and distribution of Mansonella ozzardi in coastal north Trinidad, W.I.

A day blood smear survey for Mansonella ozzardi in the north coast communities of Trinidad recorded a prevalence of 4.8% in 4,488 persons examined. Prevalence rates were highest in the four western-most communities, where the vector, Culicoides phlebotomus, is a severe nuisance problem. Prevalence rates increased with age and were higher in males than in females. Mean microfilaria densities were low in both sexes up to 50 years of age but in older males the density increased with age. Wuchereria bancrofti infections were detected in five of the ten communities surveyed.

Bancroftian filariasis in coastal north Trinidad: the effects of mass chemotherapy using spaced doses of diethylcarbamazine citrate on human microfilaraemias and vector infection rates.

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 6 mg/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 100 mm3 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 (less than 10 microfilariae per 100 mm3 of blood) after chemotherapy.

The control of hookworm disease in Commonwealth Caribbean countries

Like other countries around the globe where conditions existed for the parasites causing hookworm disease to thrive, this disease was a serious problem to settlers in countries of the Commonwealth Caribbean, i.e. those countries that were formerly part of the British Empire. Early in the 20th century, the Rockefeller Foundation (RF) assisted the southern United States in controlling this disease. Soon other countries requested assistance and the Rockefeller Foundation responded by creating their International Health Commission to target the problem. Guyana (then British Guiana) was the first country where work was started. Through a system of chemotherapy, sanitation with the provision of latrines and health education the RF assisted the Commonwealth Caribbean countries during the period 1914-1925 in controlling the disease. Most countries continued the programmes started by the Rockefeller Foundation and this paper provides evidence through a series of surveys to show that hookworm disease is no longer a public health problem.

Effects of Toxorhynchites moctezuma larval predation on Aedes aegypti populations: experimental evaluation

Abstract. Predatory larvae of the mosquito Toxorhynchites moctezuma were used experimentally to control a standing crop of larvae of the dengue vector mosquito Ae.aegypti. Each week, fifty Ae.aegypti first instar larvae were introduced to each of five water‐filled drums (220 litres) of the type commonly used for domestic water storage in Caribbean dwellings. At the beginning of the fourth week, a certain number (0, 1, 2, 5 or 10) of first instar Tx.moctezuma larvae were introduced to each drum and the daily yield of Ae.aegypti adults from each drum was monitored thereafter. The experiment was repeated three times. With only one or two Tx.moctezuma larvae, predation on Ae.aegypti larvae stopped the output of Ae.aegypti adults for 1 week. Five or ten Tx. moctezuma prevented any Ae.aegypti emergence for up to 16 weeks. Cannibalism among Tx. moctezuma larvae was seldom observed and appeared not to be a hindrance in using this species against Ae.aegypti. Thus Tx.moctezuma is regarded as a good candidate for the biological control of Ae.aegypti by augmentative releases.

Seasonal abundance, biting cycle and parity of the mosquito Haemagogus leucocelaenus in Trinidad, West Indies

Adult female populations of Haemagogus leucocelaenus (Dyar and Shannon), the sylvan vector of yellow fever, 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.

Diel biting activity of Culex (Melanoconion) caudelli in Trinidad, West Indies

ABSTRACT. 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.