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Biomedical subjects

W W Macdonald

Publications and source records attributed to W W Macdonald.

At least 19 recordsLinked to original sources
PubMed1993

The ecology of anopheline mosquitos in northwest coastal Malaysia: larval habitats and adult seasonal abundance.

Collections of anopheline mosquitos were made twice monthly for 13 months from a cow-baited trap in two villages, Kampung Permatang Rawa and Sungai Udang Kecil, on mainland coastal Penang, Malaysia. Each collection period was six hours from sunset. Unquantified larval collections were made regularly in each area. Although the villages were only about 50km apart, and each had extensive, irrigated rice-fields in its vicinity, the species abundance and the seasonal fluctuations differed significantly. In Kampung Permatang Rawa Anopheles sinensis and An. peditaeniatus were dominant in prevalence, whereas in Sungai Udang Kecil An. indefinitus and An. lesteri paraliae were most common and An. peditaeniatus was relatively rare. The rice growing schedules in the two areas differed, but there was a moderate correlation between the abundance of several species and the rice-growing pattern. There was no correlation at either site with rainfall.

Agriculture↗
PubMed1993

The ecology of anopheline mosquitos in northwest coastal Malaysia: host preferences and biting-cycles.

The host preferences of eight species of anophelines were studied in two coastal Malaysian villages, Kampung Permatang Rawa and Sungai Udang Kecil, by seven 12-hour catches in each village. Collections were made concurrently from a human-baited net trap, a cow-baited net trap and by human-bait landing catches. Anopheles campestris was attracted almost equally to man and cow, but An. lesteri paraliae, An. nigerrimus, An. peditaeniatus, An. sinensis, An. indefinitus, An. subpictus and An. vagus showed a strong preference for the cow bait. The human-bait landing catches were more productive than the human-baited net trap, which attracted very few mosquitos. Seven more all-night catches were made at each village employing only the cow-baited trap, and the combined data were used to plot the biting-cycles of each species at each site. Although the biting-cycles at the two localities were in general agreement, there were notable differences. At Sungai Udang Kecil, where the collection site was relatively sheltered, several species showed a steady decline in numbers from sunset to sunrise. At Kampung Permatang Rawa, on the other hand, where the site was more exposed and close to the sea, the same species showed a bimodal pattern of activity with an early evening peak followed by a decline then a period of increased activity before sunrise rising to a second, lesser peak at 0500-0600 hours.

Animals↗
PubMed1991

Control of Culex quinquefasciatus in Myanmar (Burma) and India: 1960-1990.

During the past 30 years three major programmes of research have been carried out in Myanmar (Burma) and India on the ecology and control of Culex quinquefasciatus. To differing degrees the programmes have employed environmental, chemical, biological and genetic control strategies, but none has been an unqualified success. Results have been good when well-trained staff with substantial resources were employed, but much poorer when less-well-equipped general health workers took over the programmes. Overall, it would seem most cost-effective for health workers to concentrate their efforts on the elimination of the limited number of larval habitat categories which commonly contribute a large fraction of the adult population. Insecticides and biological control agents should serve as supplements, not as alternatives, to environmental management. Genetic control strategies have currently no place in C. quinquefasciatus programmes.

Animals↗
PubMed1990

A mark-release-recapture experiment with Mansonia mosquitos in Malaysia.

An experiment was carried out with Mansonia mosquitos in an area endemic for subperiodic Brugia malayi to assess the applicability of the mark-release-recapture method to these mosquitos. An estimated 17,880 individuals of six species of Mansonia were marked with fluorescent dust and released: 453 Ma. annulata, 305 Ma. annulifera, 6,200 Ma. bonneae, 516 Ma. dives, 3,998 Ma. indiana and 6,408 Ma. uniformis. Twenty-three marked individuals were recaptured. Most recaptures were made one or two nights after their release, but one Ma. annulifera was recaptured five nights later and one Ma. bonneae had been marked and released 6-11 nights previously. The recaptured mosquitos were collected between 0.5 and 2.4 km from their release points.

Animals↗
PubMed1978

A light and electron microscope study of rickettsia-like organisms in the ovaries of mosquitoes of the Aedes scutellaris group.

The ovaries from some members of the Aedes scutellaris group were examined by light and electron microscopy to locate rickettsia-like organisms, and Culex pipiens fatigans was used as a control. It was found that light microscopy was unsatisfactory for this purpose since none of the available staining techniques demonstrates the organisms clearly and diagnostically. With the electron microscope it was shown that the organisms were by no means as common in the mosquitoes of the A. scutellaris group as in C.p. fatigans; they were quite frequently seen in A. polynesiensis, of sporadic occurrence in A. malayensis, rare in A. tabu and have not yet been identified with certainty in A. cooki.

Aedes↗
PubMed1972

A survey of the distribution and relative prevalence of Aedes aegypti in Sabah, Brunei, and Sarawak.

Although dengue haemorrhagic fever is widely established in South-East Asia, no cases have been reported from Borneo. In order to help to assess whether the infection could become established in Borneo, a survey was made, using the single-larva collection method, of the distribution and prevalence of the principal vector, Aedes aegypti, in Sabah and in a few towns and villages of Brunei and Sarawak. In addition, the prevalence of Ae. aegypti was compared with that of certain other species of Aedes.Ae. aegypti was found to be well established in the north, east, and south-west of Sabah but to be absent from almost all of the west coast. It was either uncommon in, or absent from, several small coastal villages; in others, very high Breteau indices were recorded. No reasonable explanation for this discontinuous distribution can be suggested. Large numbers of potential larval habitats were found, giving reason to believe that Ae. aegypti will spread further within these territories.

Aedes↗
PubMed1970

The magnitude of seasonal changes in larval populations of Aedes aegypti in Bangkok, Thailand.

Weekly surveys of Aedes aegypti larvae were made during 1966-67 in three localities in Bangkok in order to detect and measure any changes in the population which might be correlated with the seasons. The larval habitats were divided into water-jars and miscellaneous containers. Only the data from alternate weekly surveys were analysed. Analysis of variance showed that the changes in the numbers of habitats occupied varied greatly both by month and by locality. It is concluded that there was some reduction in the larval population during the cool and hot seasons and that the magnitude and timing of the fall varied from place to place. The reduction was of the order of 11%-26%. Local environmental changes, as well as climatic changes, greatly influenced the Ae. aegypti population.

Aedes↗