Starch-gel electrophoretic studies on nine gene-enzyme systems comprising 14 loci revealed a fair level of genetic variation in two population samples of Anopheles maculatus from Peninsular Malaysia. The proportion of polymorphic loci was 0.36 for the Fort Bertau sample and 0.29 for the Gua Musang sample, while the mean heterozygosity value was 0.09 for Fort Bertau and 0.07 for Gua Musang. The values of genetic similarity (I = 0.98) and genetic distance (D = 0.02) were of the rank of geographical populations.
Until recently, very little was known of Anopheles species complexes and their relationships to epidemiology and malaria transmission in Southeast Asia. During the past eight years, extensive studies on the genetics of natural populations of anopheline mosquitoes in this region, involving the interdisciplinary efforts of taxonomists, operational entomologists and biologists, have revealed groups of cryptic species of Anopheles vectors, particularly the An. leucos phyrus group. This species group comprise seventeen species and two subspecies widely distributed in the forested areas of Southeast Asia. Among these species. An. dirus Peyton and Harrison, has been shown by cytogenetic and morphological studies to be a complex of at least seven isomorphic species, provisionally designated species A, B, C, D, E, F and takasagoensis, on the Southeast Asian mainland. Cytological identification of these species is based on distinct banding patterns of salivary gland polytene chromosomes as well as heterochromatin differences in mitotic karyotypes. The five species found in Thailand (A-D, F) exhibit distinct geographic distributions. Species A is widespread throughout Thailand except in the south. Species B had been found in sympatry with species C in southern Thailand and both seem to show north-south clinal geographic variation. Species D is common on the west side of southern Thailand and along the Thai-Burmese border in sympatry with species A. Species F, An. nemophilous Peyton and Ramalingam, has been found in a population at the Thai-Malaysian border in this study although it was known to be common in southern and western Thailand and Peninsular Malaysia. Species E is known only from western India. The five species found in Thailand also exhibit seasonal variation in relative abundance and different nocturnal biting cycles. Chromosomal polymorphisms have been observed in mitotic and polytene chromosomes of An. dirus A and D. Species B and C also show heterochromatin variation in the sex chromosomes, but are monomorphic for the standard sequence in polytene chromosomes. These biological characteristics of the An. dirus complex may have implications for understanding the epidemiology of malaria in Southeast Asia. Recent cytogenetic studies of wild-caught samples of An. leucosphyrus from Sumatra, Kalimantan and southern Thailand have revealed the presence of two distinct species within this taxon. Species A is widely distributed in southern Thailand, East Malaysia and Kalimantan, while species B is confined to Sumatra. The two isomorphic species are vectors of human malaria within their range of distribution.(ABSTRACT TRUNCATED AT 400 WORDS)
A dot enzyme immunoassay (DEIA) was used to determine the levels of antibody to dengue 3 virus in the acute and convalescent sera of febrile patients with a clinical diagnosis of dengue fever or dengue haemorrhagic fever. The antibody titres were compared with titres determined by the haemagglutination inhibition (HI) test. The results of the study showed that, besides being more simple to perform, the DEIA is in order of magnitude more sensitive than the HI test. Furthermore, the data suggest that it is possible to use a single dilution as a cutoff point to predict with reasonable accuracy, if a patient has had a recent dengue infection. The DEIA test for antibodies to dengue virus is an appropriate technology highly suitable for rapid diagnosis and surveillance in developing countries.
Four recent cases of dengue fever with severe, unusual clinical manifestations are described. Two of these cases had features of fulminant hepatitis and encephalopathy; one of these cases was fatal. The two remaining cases showed hepatitis with renal impairment. The significance and importance of these unusual manifestations of dengue disease are discussed.
Analysis of diarrhoeal disease patterns in Malaysia from 1981-1986 suggested that infectious hepatitis ranked as the most predominant diarrhoeal disease followed by typhoid, food poisoning, dysentery and cholera. Although these five major food and water-borne diseases are still endemic in this country, diarrhoeal diseases per se no longer become an important public health problem in Malaysia. Enforcement of the cholera control program brought the incidence of the disease to a minimal. Unfortunately, this fatal form of diarrhoeal disease caused the greatest mortality compared to the others. Seasonal influence also played a part in controlling the occurrence of the disease. There was a preponderance of diarrhoeal diseases during the rainy season implicating contaminated water as a source of transmission. Although greater than half of the population has been supplied with piped water and sanitary latrines, a lot more has to be done before diarrhoeal diseases could be eliminated from this country.
In 1982, Malaysia experienced the worst dengue/dengue haemorrhagic fever outbreak in its history. All states in Peninsular and East Malaysia were similarly affected. There was a total of 3,005 cases with 35 deaths, with the majority of cases occurring between the months of July to October. There was a total of 1,001 laboratory confirmed cases. Most of the cases were in patients over the age of 15 years. The Chinese population was mainly affected, although a much higher proportion of Malays was noted in comparison to previous years. The main serotypes involved were dengue-1 and dengue-3. No dengue-4 serotype were isolated.
Susceptibilities of two colonies of the taxon An. dirus (one from Perlis and from Thailand) and one colony of An. balabacensis from Sabah to DDT, dieldrin, malathion, fenitrothion and propoxur were determined. DDT and fenitrothion tolerance was found in An. dirus species B and An. balabacensis. No resistant strain was isolated as the two colonies were not either homozygous or nearly so for resistance. Field testing of the susceptibility of the adults of An. balabacensis to DDT was carried out between 1957 to 1976. The results indicated a progressive rise in the LC50 levels greater than 1% in almost all instance. The variation in the number of sprays applied in some districts have resulted in varying sensitivities. Association between the changes in levels of DDT susceptibility and exophilic habit of An. balabacensis has been observed but needs further confirmation. The significance of these findings and the difficulties in distinguishing tolerant from truly resistant individuals are discussed in relation to accurate species identification.
Fifteen independent E. coli strains of avian, bovine and porcine origin in Peninsular Malaysia were tested for antibiotic resistance and conjugative R plasmids. Eight (53%) isolates were found to be antibiotic resistant. Among them, 37.5% were mono-resistant and 62.5% were resistant to three or more antibiotics, i.e., multi-resistant. All of them were resistant to Tc and sensitive to Gm and Nx. Three of the eight antibiotic resistant strains were able to transfer all or part of their resistance to an E. coli K12 recipient by conjugation. The transfer frequencies of Km, Sm and Tc resistance of the three donors varied between 4.5 X 10(-8) to 6.8 X 10(-7). Analysis of the plasmid profiles of all the three donors and their respective transconjugants after agarose gel electrophoresis provided conclusive evidence that the transferable resistance traits were plasmid-mediated.
A total of 37 species of mosquitoes from seven genera were collected in six villages in the Bengkoka Peninsula, Sabah State, during two visits in 1981 in connection with studies on malaria and filariasis. Fifty-five per cent of the total mosquitoes collected were Mansonia. An. collessi constituted a new record of the species from Sabah. An. balabacensis was found to be naturally infected with sporozoites. Ma. bonneae was found to be naturally infected with Brugia, probably B. malayi. Parous rates of An. balabacensis and Ma. bonneae were very high with consequent high probability of survival ideally suiting transmission of malaria and filariasis.
The prevalence of human rotavirus enteritis in children admitted to the gastroenteritis ward of the Kuala Lumpur General Hospital was studied in 1982. Human rotavirus in the stool of the patients was detected by enzyme-linked immunosorbent assay. The survey showed that rotavirus enteritis in children were observed throughout the year, with two broad peaks of rotavirus infection occurring around March and September. The lowest incidence was recorded in July, however, no prolonged period of low prevalence of rotavirus enteritis was observed. The average prevalence for the whole of 1982 was 40% of the total diarrhoeal cases. No significant relationship was noted between the prevalence of the disease and rainfall.
To determine if the unusually high incidence of salmonellosis reported on Guam for several years might be the result of more frequent bacteriologic examination of gastroenteritis/diarrhoea patient stool specimens, a survey of medical clinic and laboratory activities was undertaken among countries in the Pacific Basin Area. Survey results suggest that while Guam laboratories may be particularly proficient in isolating Salmonella organisms, the quantity of stool specimens examined could not account for the higher incidence of salmonellosis observed on the island.
Six independent isolates of Klebsiella from hospital environmental sources in Malaysia were found to be resistant to at least ampicillin, carbenicillin, cefoperazone, chloramphenicol, gentamicin and tetracycline. On the basis of their antibiograms, they were divided into four antibiogroups. They transferred all or part of their multiple antibiotic resistance traits to E. coli by conjugation. The results suggest that these Klebsiella strains harbour self-transmissible R plasmids. The significance of these findings are discussed.
The incidence of HBsAg in random blood donors was found to be twice that of the prisoner population. The anti-HBe however, was about twice that in the prisoners when compared with the random blood donors. Both the random blood donors and the prisoners had similar incidence of HBeAg. The percentage frequency of HBsAg positivity with anti-HBe positivity was also similar in both groups. The 18 normal non-blood donors did not have HBsAg, HBeAg or anti-HBe.
This report highlights some of the educational aspects on nutrition and tropical diseases. Health conditions in most of the countries in this region has improved but not at the same pace as the progress in medical sciences. The slow progress in tackling this problem has been partly due to the failure of understanding psycho-social, cultural and economic patterns. Many of the health workers and educators who are involved in the control of tropical diseases emphasize on practice rather than research. Due emphasis should be given to training and research in health education involving not only the professionals and auxiliary staff but also political leaders, policy makers and community leaders at grassroot level.
A study was carried out to identify some of the cultural factors in the epidemiology of filariasis in an endemic community in Malaysia. The viewpoint of the community, data an responses on knowledge of illness and filariasis, host related factors, health examination, vector study were analysed and discussed. The observations noted on cultural factors were: Occupational pattern: Different agricultural occupations seemed to related to transmission in terms of body exposure. Activities not related to production of crops: Play groups in late afternoon, bathing of household members near and after sunset, congregations at prayer houses very much exposed the population to mosquito bites in different degree in terms of length of time spent outside the house. Knowledge of filariasis: Filariasis was understood in terms of elephantiasis, the chronic stage of the disease. Other signs of disease-adenolymphangitis, red lines running down one or both legs and abscess were generally recognized but not often annonated with specific disease. Attitude toward disease: Filariasis was not seen as a health problem and the idea of filarial worms was still hard to believe. Knowledge on disease causation: Biological causes were generally recognized, though the idea of bacteria was not widespread.