A one year study was conducted to evaluate the impact of spray application of Bacillus thuringiensis israelensis (Bti), strain AM65-52 on vector populations and dengue transmission in a dengue endemic state in Malaysia. Residential sites with similar populations of Aedes aegypti (L.) and Aedes albopictus Skuse were studied. One site was treated with spray application of Bti into all outdoor target vector habitats, which consisted of natural and artificial containers. The other site was not treated. The impact of spray application was measured with an indoor and outdoor ovitrap index (OI) and epidemiologic data. Significant reductions in both Ae. aegypti and Ae. albopictus, OI were observed both indoors and outdoors, in treated sites compared to untreated sites (p < 0.05). OI reduction was achieved over time in the treated area. The OI was suppressed to below 10%. This was maintained for 4 weeks into the post-treatment phase. The outdoor OI at the untreated site remained at more than 40% for 38 weeks during the evaluation period. One dengue case occurred at the Bti treatment site at the beginning of the treatment phase, but no further cases were detected during the remainder of the treatment phase. However, there was an ongoing dengue outbreak in the untreated area with 15 serologically confirmed cases during weeks 37-54. Intensive fogging operations with pyrethroids at the untreated (Bti) site had a positive impact on Ae. albopictus, but not on Ae. aegypti.
The human immunodeficiency virus (HIV) epidemic has had a profound influence on the epidemiology of tuberculosis (TB). The potential for HIV-associated TB cases to transmit M. tuberculosis and to produce a secondary increase in TB morbidity is unknown. A cross-sectional study was carried out to compare the prevalence of M. tuberculosis infection among the household contacts of HIV-positive and HIV-negative pulmonary tuberculosis (PTB) patients. Records of tuberculin (Mantoux) tests administered during routine contact investigations at the Chest Clinic, Hospital Kota Bharu, from 1999 to 2000 were reviewed. The HIV status of the patients was based on the results of ELISA tests while information on household contacts was gathered during visits to their houses. Ninety-four contacts of 39 HIV-negative patients and 44 contacts of 17 cases of HIV-positive patients were included in this preliminary study. 30% (12/40) of the contacts of HIV-positive PTB had a positive tuberculin compared with 52.8% (47/ 94) of the contacts of HIV-negative patients [OR = 0.41, 95% Confidence interval (CI) 0.17 - 0.97; p = 0.016]. The difference was still significant after performing multivariate logistic regression analysis to adjust for variables associated with infectiousness of TB (adjusted OR = 0.24, 95% CI 0.07 - 0.87; p = 0.03). This study has shown that HIV-infected PTB patients are less infectious to their contacts than HIV-negative patients. The presence of MV in the community may not necessitate a change of the current policy of the management of contacts.
Study site: Chest Clinic, Hospital Kota Bharu, Kelantan, Malaysia
Soil-transmitted helminthiasis is a common problem in communities with poor socio-environmental conditions. This study was undertaken to identify important socio-environmental predictors of soil-transmitted helminthiasis in Bachok, a rural community in Kelantan for the development and implementation of an effective prevention and control program. Of 363 children randomly sampled, 38.8% were infected with soil-transmitted helminthiasis. Risk predictors of soil-transmitted helminthiasis found to be significant after adjustment included poor household hygiene score and large household size. The probability of being infected was 0.58 amongst children with both of these risk factors.
Surveillance studies on cercarial dermatitis were carried out in paddy growing areas in Peninsular Malaysia. It was observed that dermatitis in paddy planters occurred in paddy fields which were cultivated using animals such as bafflos or fields where domestic animals were allowed to graze during the off planting season as these animals harbored the parasite. The causative agent of cercarial dermatitis was Schistosoma spindale. A total of 215 small mammals trapped from Alor Setar and 126 trapped from Labu were examined for the schistosome. In Alor Setar Bandicota indica, Rattus argentiventer and Rattus rattus diardii were the only wild mammals found to be infected with the parasite, while in the Labu areas only Rattus tiomanicus jalorensis was positive for the schistosome. The occurrence of S. spindale in R. argentiventer and R.r. diardii in Alor Setar and in R.t. jalorensis in Labu constitute new host and geographic distribution records of the schistosome.
A study was carried out to determine the distribution of cockroaches in two different housing areas with central sewerage or individual septic tanks in an urban area in Kuala Lumpur, Malaysia. Six species of cockroaches were present and of these Periplaneta americana and Periplaneta brunnea were found in greater abundance. Seventeen species of bacteria were isolated and of these Escherichia coli and Klebsiella p. pneumoniae were isolated in greatest numbers. Control measures carried out using lambda cyhalothrin showed that there was no significant difference between treated and control sites.
Frogs caught from two States (Selangor and Langkawi) in Malaysia were examined for spargana of Spirometra sp. Infected frogs usually show no marks of infection but some had swelling and bleeding at the infection site. The size and weight of the infected frogs did not correlate with the infection status. The infection status in relation to human health is discussed.
Mosquito adults and larvae were collected from dengue high risk areas and transported to the laboratory for identification. Identified mosquitos were pooled according to the species, date and locality and stored at -70 degrees C. A total of 1,385 pools of Aedes albopictus and 267 pools of Ae. Aegypti were collected from major towns in 12 states in Peninsular Malaysia. Virus isolation was carried out using cell culture (C6/36 clone) of Ae. albopictus and detection of dengue virus by the peroxidase anti-peroxidase staining. All positive isolations were further re-confirmed by the reverse transcriptase-polymerase chain reaction (RT-PCR). Most of the pools were negative with PAP staining and RT-PCR. However, 11 mosquito pools were positive with PAP staining. On the other hand, samples from Terengganu, Pulau Pinang and Johor were positive using both methods.
Serum specimens were collected from 6 species of animals living in 9 states of Malaysia including Sabah, North Borneo in 1993. Antibodies against Japanese encephalitis (JE) virus in these sera were detected by means of hemagglutination-inhibition (HI) and neutralization (NT) tests. By HI test, 702 of 2,152 (32.6%) sera showed positive results. Higher positive rates were obtained by the NT test, in which 1,787 of 1,927 (92.7%) sera had antibodies against JE virus. All serum specimens with positive HI were confirmed as positive by the NT. Swine sera showed especially higher rates of antibody positive and higher antibody titers compared with other animals. These results suggest that JE infections are widely distributed among many animals of Malaysia, and pig is the most susceptible amplifier host for JE virus.
Studies on age groups within activity cycles, age composition and survivorship in natural populations of Mansonia in Kampung Pantai, Bengkoka Peninsula of Sabah state have been described. Early activity of 3-5 parous Ma. bonneae during the first hour after sunset was noted. Age composition of Ma. bonneae at forest shade, indoor and outdoor of house, comparative buffalo vs human bait outdoor in Kampung Pantai showed all round high parous rates ranging from 66.7 to 75.4%. Population 3-parous and older ranged from 18.8 to 26.7%. Nine of the 14 infective Ma. bonneae were 3-parous and this segment of the population was engaged in active transmission. High parous rates were observed in Ma. dives and Ma. uniformis taken in small numbers. Parous rates of Ma. bonneae taken in Kampung Delima and Kampung Taradas were also high. Estimates of daily survivorship of Ma. bonneae and Ma. dives determined by two methods were very high.
Two separate observations from recent electrophoretic studies of the systematics and population genetics of laboratory-reared populations which had a long history of colonization in various laboratories, were found to be inconsistent with the present study which used wild-caught populations from East Malaysia. Reanalysis of the two data sets generally indicated a low amount of genetic variation in laboratory colonies. The latter is characterized by higher frequency of monomorphic loci, low average heterozygosity values and, in one extreme case, no variability at two loci. However, natural populations of An. balabacensis and An. leucosphyrus showed more protein variability by the use of polyacrylamide gel electrophoresis. Since laboratory-maintained mosquitoes are genetically and phenotypically different from those in the field, results of laboratory studies on the systematics and population genetics of Anopheles species complexes may be biased.
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 study to identify the knowledge of infected and uninfected respondents on filariasis and epidemiologic factors in one endemic community in Malaysia to determine their role in the transmission and control of filariasis was carried out. The data were collected by non-participant observations and interviews using semi-structured schedules. The majority of respondents in both groups had knowledge of filariasis. There was no marked difference between male and female respondents, and similarly, there was fair distributions of knowledgeable respondents with and without some years of schooling. On filarial transmission, 9.2% of the infected said that filariasis was contacted through mosquito bites, while among the uninfected it was 7.4%. Within the infected, 14.8% thought that filarial worms entered the human body through the consumption of unhygenically prepared foods and drinks while, among the uninfected it was 20.4%. Both groups were aware of the presence of mosquitoes in their village. However, the majority did not associate this factor with host's susceptibility to filarial infections. Rather, they were of the opinion that personal hygiene and proper meals had something to do with filariasis. The findings showed there was general awareness of filariasis in the community which might indicate that the health campaigns had reached various levels of the population. Yet, they still lacked knowledge on disease transmission. Also, they did not make direct association between environment and exposure to mosquitoes bites though they were aware of their presence but which they regarded as not directly harmful to their health.
Despite great development in socioeconomic status throughout 50 years of independence, Malaysia is still plagued with soil-transmitted helminthiases (STH). STH continue to have a significant impact on public health particularly in rural communities. In order to determine the prevalence of STH among rural Orang Asli children and to investigate the possible risk factors affecting the pattern of this prevalence, fecal samples were collected from 292 Orang Asli primary schoolchildren (145 males and 147 females) age 7-12 years, from Pos Betau, Kuala Lipis, Pahang. The samples were examined by Kato-Katz and Harada Mori techniques. Socioeconomic data were collected using pre-tested questionnaires. The overall prevalence of ascariasis, trichuriasis, and hookworm infections were 67.8, 95.5 and 13.4%, respectively. Twenty-nine point eight percent of the children had heavy trichuriasis, while 22.3% had heavy ascariasis. Sixty-seven point seven percent of the children had mixed infections. Age > 10 years (p = 0.016), no toilet in the house (p = 0.012), working mother (p = 0.040), low household income (p = 0.033), and large family size (p = 0.028) were identified as risk factors for ascariasis. Logistic regression confirmed low income, no toilet in the house and working mother as significant risk factors for ascariasis. The prevalence of STH is still very high in rural Malaysian communities. STH may also contribute to other health problems such as micronutrient deficiencies, protein-energy malnutrition and poor educational achievement. Public health personnel need to reassess current control measures and identify innovative and integrated ways in order to reduce STH significantly in rural communities.
Poliovirus kept on the cut surfaces of fully ripe papaya cubes placed in an ice box showed a sharp and significant reduction in the recovery of infectious virus about 15 minutes after exposure. Thereafter, a very gradual decrease ensued and infectious residual virus was detected up to the end of the 6-hour exposure period. Papaya cubes washed or kept overnight before virus inoculation, and from less ripe fruits produced a similar survival pattern. A very small proportion of the inoculum was recovered from the mashed content of the inoculated papaya cubes thus suggesting that most of the non-recovered virus particles were inactivated. The results suggest that the importance of poliovirus-contaminated cut papayas as a transmission vehicle for the virus is greatly reduced by the rapid decline in the infectivity of a large proportion of the virus soon after contamination. Nevertheless, the potential to transmit remains as a small residual pool of infectious poliovirus is able to survive for a relatively long period.