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Biomedical subjects

M W Service

Publications and source records attributed to M W Service.

At least 37 records · Page 2Linked to original sources
PubMed1993

The ecology and behaviour of the forest form of Anopheles gambiae s.s.

Studies on the ecology of Anopheles gambiae s.s. and the transmission of malaria were undertaken in a high rainfall forested area in southern Sierra Leone. Anopheles gambiae s.s., identified by chromosomal techniques as the Forest form, was the only malaria vector in the study village. Surprisingly, rice fields or swamps were not favoured breeding places for this species; breeding mainly occurred in temporary pools. The mean annual sporozoite rate of An. gambiae s.s. determined by ELISA was 3.9%. Pyrethrum spray, human bait, and exit trap collections, as well as identification of mosquito blood-meals using the ELISA method, showed that the forest chromosomal form of An. gambiae s.s. was highly anthropophagic and exophilic.

Animals↗
PubMed1992

Importance of ecology in Aedes aegypti control.

Aedes aegypti is one of the world's most widely distributed mosquitos and is of considerable medical importance as a vector of dengue and yellow fever. Not surprisingly therefore there has been more written on its biology than any other mosquito. The present paper summarizes ecological studies undertaken on this vector, including those on pre-adult mortalities, life-tables, adult dispersal and survival rates. In discussing surveillance techniques it is pointed out there are still no reliable methods for monitoring adult populations. The importance of the resting habits of adults and house construction in insecticidal control of Ae. aegypti is discussed. The question is, have ecological studies and population modeling resulted in any more understanding of the epidemiology of dengue, or helped formulate better control strategies? The answer seems to be not usually, possible because there have actually been relatively few good ecological studies on Ae. aegypti. Although mathematical modeling indicates that better control might be achieved if it were directed at the larvae, not adults, this has not usually been taken into consideration by those engaged in control. There is clearly need for greater collaboration between those practicing control, and ecologists and modelers.

Aedes↗
PubMed1991

Agricultural development and arthropod-borne diseases: a review.

A review is presented of the interrelationships between arthropod vectors, the diseases they transmit and agricultural development. Particular attention is given to the effects of deforestation, livestock development and irrigation on the abundance of vectors and changing patterns of diseases such as malaria, trypanosomiasis, leishmaniasis, Chagas' and some arboviral infections. The question as whether keeping livestock diverts biting away from people and reduces diseases such as malaria--that is zooprophylaxis, or whether the presence of cattle actually increases biting populations is discussed.

Agriculture↗
PubMed1984

The effect of domestic detergents on the population dynamics of the immature stages of two competitor mosquitoes, Culex cinereus Theobald and Culex quinquefasciatus Say (Diptera, Culicidae) in Kenya.

In some rural areas of Kenya pit latrines are the most important breeding places of Culex quinquefasciatus, but this vector is often rapidly displaced by a competitor, Culex cinereus, which then breeds prolifically in the latrines. In urban settlements, however, cesspools are the main breeding sites of C. quinquefasciatus and no such species replacement occurs. These latter habitats contain water contaminated with domestic detergents. When detergents were introduced into a pit latrine colonized only by C. cinereus this mosquito was eliminated after about 3 weeks. When both species were reared in water containing detergents C. cinereus had lower pupal yields than C. quinquefasciatus. In two pit latrines where C. cinereus normally displaced C. quinquefasciatus, the addition of detergent prevented this, and after their coexistence for a few weeks, C. cinereus eventually disappeared. These observations suggest that during the last few decades domestic detergents, together with other pollutants such as insecticides, may have contributed to the elimination of competitors, such as C. cinereus, from C. quinquefasciatus breeding sites.

Animals↗
PubMed1983

Value of cuticular and internal hydrocarbons for the identification of larvae of Anopheles gambiae Giles, Anopheles arabiensis Patton and Anopheles melas Theobald.

Gas chromatographic profiles of the cuticular and internal lipids extracted from 4th-instar larvae of the Anopheles gambiae complex have shown quantitative differences in their chain length distributions. For example, hydrocarbons extracted with 95% ethanol showed relative differences in peak heights eluting at Kovat indices (KI's) 2840 (An. gambiae 1.21, An. arabiensis 1.39 and An. melas 1.14) and 3150 (An. gambiae 6.73, An. arabiensis 13.40 and An. melas 13.50). However, while using the non-hydrocarbon fractions, differences were obtained at a KI of 2160 (An. gambiae 0.45, An. arabiensis 0.45 and An. melas 1.16) and at a KI of 2430 (An. gambiae 2.90, An. arabiensis 1.81 and An. melas 3.50). Utilizing the total ethanol extract and omitting the TLC (thin layer chromatography) step, thus saving four hours of analysis time, good separation was achieved at a KI of 2060 (An. gambiae 0.60, An. arabiensis and An. melas 0.0) and at a KI of 2430 (An. gambiae 1.13, An. arabiensis 0.69 and An. melas 1.59). Other differences were also noted in the profiles which could identify one or more of the three species. Good separation could be made on single larvae as well as on small batches of specimens. It was concluded that analysis of cuticular and internal lipids provides a useful biochemical method of distinguishing larvae of these species, but further studies are needed on these and other species of the An. gambiae complex collected from many localities in Africa.

Animals↗
PubMed1980

Identification of mosquitoes of Anopheles gambiae species complex A and B by analysis of cuticular components.

Two important vectors of malaria in Africa, Anopheles gambiae and Anopheles arabiensis (Diptera: Culicidae), often occur sympatrically and cannot be distinguished morphologically. A chemical method was developed to identify individual laboratory-reared adult males or females of either species by extraction and analysis of cuticular components with gas chromatography. Statistically significant differences were seen between species when selected pairs of peaks were compared.

Animals↗
PubMed1979

Light trap collections of ovipositing Simulium squamosum in Ghana.

At a site near Boti waterfalls in southern Ghana a total of 14 644 female and two male Simulium squamosum were caught in four nights in Monks Wood light traps. The highest catch, of 6520 females, was obtained in a single night with an ultraviolet light tube that had a one-second flash rate. About 12% of the females caught were gravid and dissections of non-gravids showed that they had oviposited very recently. The traps were clearly catching females before or soon after oviposition. The same traps caught none or very few blackflies when placed in two other localities near Akosombo. Trap location appeared very important in sampling ovipositing females of S. squamosum.

Animals↗
PubMed1979

Differentiation between species of the Anopheles gambiae Giles complex (Diptera: Culicidae) by analysis of cuticular hydrocarbons.

Lipids were extracted from 500 female Anopheles gambiae and An. arabiensis in n-hexane and the extracts examined by gas chromatographic analysis using a glass column packed with 3% OV-1 on a 100-200 mesh Gas Chrom Q which was maintained at 225 degrees C. Cuticular hydrocarbons consisted mostly of unbranched paraffins. There were differences between the distribution of compounds with 25-29 carbons. After adjusting the C27 peak to 100%, hydrocarbons C26 and C29 represent heights of 80 and 69% in An. gambiae compared with values of 49 and 95 % in An. arabiensis. Other small but consistent differences were also found. Investigations are being performed on extracts from smaller samples and on other species within the An. gambiae complex.

Animals↗
PubMed1978

A survey of Anopheles gambiae (species A) and An. arabiensis (species B) of the An. gambiae Giles complex in the Kisumu area of Kenya following insecticidal spraying with OMS-43 (Fenitrothion).

After village huts in the Kisumu area of Kenya had been sprayed with a nominal 2 g/m2 of OMS-43 (fenitrothion) as part of an insecticidal evaluation programme 964 adults of the Anopheles gambiae complex collected from huts were identified cytogenetically as either An. gambiae (species A) or An. arabiensis (species B). Similarly, cytogenetic methods were used to identify 349 adults collected from granaries and artificial pit-shelters. In addition, 2203 larvae of the gambiae complex collected from different types of habitats were specifically identified cytogenetically. As in a previous survey made prior to insecticidal spraying, adults of An. arabiensis predominated in outdoor collections while An. gambiae was highly endophilic. However, it appeared that spraying with fenitrothion had resulted in an increase in both the degree of exophily in An. arabiensis and also its relative numbers in respect to An. gambiae, although the overall pooulation of both species was greatly reduced by spraying. Insecticidal spraying may have diverted both species from feeding on man to cattle. Except for one village, where larvae of An. arabiensis were commoner than expected in cattle hoof-prints, there was little difference between the selection of different types of larval habitats by the two sibling species. Chromosomal inversions were more common in adults of An. arabiensis than in An. gambiae.

Animals↗
PubMed1975

A survey of species A and B of the Anopheles gambiae Giles complex in the Kisumu area of Kenya prior to insecticidal spraying with OMS-43 (fenitrothion).

Throughout 1972 surveys were made in Kenya on the Anopheles gambiae Giles complex in an area near Kisumu, part of which was to have all houses sprayed with OMS-43 (fenitrothion) the following year. Pre-spray data was collected on monthly hut densities, man-biting rates, parity and the human blood indices and sporozoite rates of A. gambiae caught in both an area designated for spraying (evaluation zone) and a comparison zone which was to remain unsprayed. The sporozoite rates, host preferences, and population size of the A. gambiae comples in relation to the human population were similar in the two zones. Few adults were collected from artificial pit-shelters in either zone. Cytotaxonomic identifications showed that although species A of the A. gambiae comples predominated throughout the year, the population of species B decreased relatively less in the drier months than that of species A. No marked differences were found between the host preferences or sporozoite rates of the two species.

Animals↗
PubMed1975

Detection of the predators of Simulium damnosum by the precipitin test.

Saline cell free extracts of larvae of the Simulium damnosum complex were used to immunize rabbits for the production of damnosum-antisera. Injections into the lymph nodes produced a more specific antiserum than was obtained by intramuscular injection followed by absorption. This antiserum was used to identify by the precipitin test natural predators of S. damnosum collected from the bandama River in the Ivory Coast. Various trichopteran larvae and odonatan nymphs and adults were found to be the most important predators.

Animals↗