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Biomedical subjects

Y H Bang

Publications and source records attributed to Y H Bang.

33 records · Page 2Linked to original sources
PubMed1981

Progress in malaria vector control.

Malaria control, except in tropical Africa, will probably continue to be based to a large extent on the use of insecticides for many years. However, the development of resistance to insecticides in the vectors has caused serious difficulties and it is necessary to change the strategy of insecticide use to maximize their efficacy. A thorough knowledge of the ecology and behaviour of each vector species is required before the control strategy can be adapted to different epidemiological situations. The behavioural differences between sibling species have been recognized for several years, but study of this problem has recently been simplified by improved means of identification that involve chromosomal banding patterns and electrophoretic analysis. Behavioural differences have also been associated with certain chromosomal rearrangements.New records of insecticide resistance among anophelines continue to appear and the impact of this on antimalaria operations has been seriously felt in Central America (multi-resistance in Anopheles albimanus), Turkey (A. sacharovi), India and several Asian countries (A. culicifacies and A. stephensi), and some other countries. Work continues on the screening and testing of newer insecticides that can be used as alternatives, but DDT, malathion, temephos, fenitrothion, and propoxur continue to be used as the main insecticides in many malaria control projects. The search for simpler and innovative approaches to insecticide application also continues.Biological control of vectors is receiving increased attention, as it could become an important component of integrated vector control strategies, and most progress has been made with the spore-forming bacterium, serotype H-14 of Bacillus thuringiensis. Larvivorous fish such as Gambusia spp. and Poecilia spp. continue to be used in some programmes.Application of environmental management measures, such as source reduction, source elimination, flushing of drainage and irrigation channels, and intermittent irrigation have been re-examined and currently a great deal of interest is being shown in these approaches.There has been limited interest in the genetic control of mosquitos and the phenomenon of refractoriness in some strains of the disease vectors, with the idea of replacing the vector species with the refractory strain. More research is needed before this approach can become a practical tool.It is apparent that in future a more integrated approach will have to be used for vector control within the context of antimalaria programmes. Training of staff, research, and cooperation at all levels will be an essential requirement for this approach.

Animals↗
PubMed1980

A study of small mammals in the Ciloto field station area, West Java, Indonesia, with special reference to vectors of plague and scrub typhus.

From June 1977 to June 1978 a study of smal mammals was carried out in the Ciloto field station area, West Java, Indonesia by the WHO Vector Biology and Control Research Unit-II. The objectives of the investigations were to determine the diversity and density of rodent species, to find potential plague and scrub typhus vectors and to study their host-parasite relationships. In the 13 month period a total of 6 species of murids were identified; two species of campestral rats (R. tiomanicus and R. argentiventer), one species of peri-domestic (R. exulans), one species of domestic (R.r. diardii), and two species of forest rats (R. bartelsii and R. bukit). In addition, three species of insectivores (Suncus murinus, Hylomys suillus and Crocidura monticola), and one species of carnivore were found. Of the three habitats studies (mixed, ricefield and lalang), 10 species of small mammals were found in the mixed while four species of commensal murids were found in both the ricefield and the lalang. Of the four commensal murid species R. exulans had the highest density. R. tiomanicus was common but not abundant, and least common was R. argentiventer. R.r. diardii was occasionally found in the field. The mean litter size of gravid R. tiomanicus was 7.1, R. exulans 4.3, R. argentiventer 7.5 and R.r. diardii 9. Male R. tiomanicus, R. argentiventer and R.r. diardii with spermatozoa present in animals over 55 gm. Animals of less than 50 gm had no sperm. In R. exulans spermatozoa were present in specimens weighing 24-66 gm. No sperm were detected in those below 20 gm. The flea index of Xenopsylla cheopis and Stivalius cognatus as determined for R. tiomanicus was 0.3 and 2.3;l for R.r. diardii 2.2 and 1.7; for R. exulans 0.3 and 0.5; and for R. argentiventer 0.4 and 1.7 respectively. S. cognatus had a significantly higher density than X. cheopis among the campestral and peridomestic rats, but the density of X. cheopis was significantly in the domestic rat. Overall infestation rates were equally high in both mixed and lalang habitats, but low in the ricefield. Flea indices were highest in the mixed habitat, lower in lalang, and lowest in ricefield. The putative vector of scrub typhus (Leptotrombidium (L.) deliense) was quite prevalent on campestral rats, less so on domestic ones and least on peridomestic. Overall infestation rates were equally high in both mixed and lalang habitats and low in the ricefield. Chiggers load per animal was significantly higher in the mixed habitat, lower in lalang and lowest in the ricefield.

Animals↗
PubMed1970

The effectiveness of ultra-low-volume applications of malathion at a rate of 3 US fluid ounces per acre in controlling Aedes aegypti in Thailand.

Ultra-low-volume (ULV) aerial applications of malathion at a rate of 3 US fl oz per acre (219 ml/ha) for the control of Aedes aegypti and Culex pipiens fatigans were evaluated in 2 areas near Bangkok, Thailand. A housing project of the Royal Thai Air Force received 2 applications a week apart while the village of Bang Khen received 1 application. Bioassays, oil-sensitive red dye cards, landing-rate counts, ovitraps, and light-traps were used to evaluate the effects of the treatment. A comparison of pre- and post-treatment indices indicated good control of A. aegypti following all treatments. The results of these tests when compared with those of an earlier study using 6 US fl oz/acre (438 ml/ha) showed that the higher rate of application rate was more effective. Only fair control of C. p. fatigans was obtained. A comparison of light-trap collections before and after treatment demonstrated fairly good over-all control of other species of mosquitos for 3-4 days following each of the 2 treatments on the Air Force housing area.

Aedes↗
PubMed1969

Replicate surveys of larval habitats of Aedes aegypti in relation to Dengue haemorrhagic fever in Bangkok, Thailand.

Dengue haemorrhagic fever in Bangkok and Thonburi occurs principally during the wet season. The mosquito vector is Aedes aegypti. A study was made of the larval habitats of A. aegypti in 14 localities, at three different times of the year, to determine whether there were fluctuations in the A. aegypti population, as measured by the number of occupied habitats, which could be correlated with the incidence of the infection.The habitats were classified into 6 categories and a single larva was collected for identification from each one that was occupied. The number and percentage of occupied habitats of each category per 100 houses were analysed to determine whether there were differences between localities and between times of the year. Almost all the comparisons between localities were highly significant. There was evidence of slight changes in the number of occupied habitats from time to time, the chief increase being between the cool and the warm seasons and the chief decrease from the wet to the cool season, but it seems unlikely that outbreaks of dengue haemorrhagic fever can be explained by increases in A. aegypti densities during the wet season.

Aedes↗