The amoeboid form of Blastocystis hominis has been reported infrequently, and its morphological descriptions have yielded conflicting and confusing reports. In the present study, we used the amoeboid forms seen predominantly in symptomatic patients infected with Blastocystis to provide detailed descriptions on the fine surface structure and intracellular morphology. Scanning electron microscopy revealed the irregular shape of the amoeboid form, with an intercalated fibrillar structure and a highly convoluted surface with deep indentations and projected pseudopodia. Transmission electron microscopy showed the existence of two types of amoeboid forms of B. hominis in in vitro culture, one with a large central vacuole containing tiny electron-dense particles while the other contains multiple small vacuoles in the cytoplasm. A surface coat with varying thickness surrounded the amoeboid form, which also showed prominent, extended pseudopodia of varying shape. Irregularly shaped mitochondrion-like organelles with prominent cristae, lipid inclusions, and multiple vacuoles were frequently seen in close proximity with the pseudopodia. The characteristic nucleus with a crescentic band of electron-dense chromatin material was also seen.
Species of Apelaunothrips are fungus-feeders on dead leaves, particularly in leaf-litter, and they are recorded across the Old World tropics from Africa to northern Australia and southern Japan. All species in this genus have the maxillary stylets 4-6 microns in diameter, considerably broader than the 2-3 micron diameter that is typical among Phlaeothripinae. The species are largely uniform in structure, but in four species the larger males have fore femora enlarged with a conspicuous tubercle on the inner margin at the base. In one of these species, the males are dimorphic, with no intermediates between large and small individuals, in contrast to the continuous variation in structure found in many polymorphic Phlaeothripidae. A key is provided to the 37 recognised species of Apelaunothrips, including the following: A. desleyae sp.n. from northern Australia; A. bogor sp.n. from Java; A. gombak sp.n. from Peninsular Malaysia.
Four new species of Calydiscoides Young, 1969 are described from three species of nemipterids caught off Kemaman, Terengganu, on the eastern coast of Peninsular Malaysia: C. monogrammae n. sp. from Scolopsis monogramma; C. conus n. sp. from S. magaritifer; C. scolopsidis n. sp. from S. margaritifer and S. monogramma; and C. kemamanensis n. sp. from Pentapodus setosus. The present investigation reveals that the squamodiscs (lamellodiscs) are composed of 10-12 short, complete, interlocking and concentric tubular lamellae. The innermost lamella is attached to a pair of adductor muscles.
A new nematode, Elaeolenchus parthenonema n. g., n. sp., is described from the palm-pollinating weevil Elaeidobius kamerunicus Faust. The new genus is placed in the Anandranematidae n. fam., which, together with the genus Anandranema Poinar et al., 1993, is characterised by nematodes having only a single autotokous generation in the insect host. This is the first report of a member of this superfamily reproducing only parthenogenetically. The development of E. parthenonema and its effect on the weevil host is discussed, along with a phylogenetic synopsis of the families of the Sphaerularioidea Lubbock 1861. The Beddingiidae n. fam. is proposed for Beddingia Blinova & Korenchenko, 1986, comprising the original Deladenus parasites of Hymenoptera that possess both free-living and parasitic amphimictic generations in their life-cycles. This family is considered to have the most primitive type of development in the superfamily.
A study of the prevalence and intensity of soil-transmitted helminthiasis among pre-school children aged 0 to 7 years from an Orang Asli village resettlement scheme in Gua Musang, Kelantan was undertaken. The overall prevalence of soil transmitted helminthic (STH) infections was 56.0%. The predominant helminth found was Ascaris lumbricoides while the commonest type of infection was a mixed infection with Ascaris lumbricoides and Trichuris trichiura. The prevalence rates of Ascaris, Trichuris and hookworm infections were 47.5%, 33.9% and 6.2% respectively. The intensity of Ascaris infections were 64.5% light, 27.3% moderate and 8.3% heavy whilst the intensity of Trichuris infections were 80.5% light, 18.3% moderate and 1.2% heavy. However, the intensity of hookworm infections were 86.7% light, 13.3% moderate and no heavy infection. The prevalence of helminthiasis (STH) shows an-age dependent relationship, with the lowest prevalence in 0-< 1 year age group and highest in the 6-< 7 year age group.
Established criteria for morphological typing of sarcocysts was applied to a large series of cases of human skeletal muscle sarcocystosis in Malaysia to determine the type of sarcocyst present. We also wanted to test the general usefulness of this classification and to determine if there are any new cyst types. Three-dimensional (3-D) reconstruction was done to see if the sarcocyst has a distinct 3-D morphology. A total of 66 sarcocysts from 21 cases of human muscle sarcocystosis obtained from a previous prevalence study were examined. Tissue sections (5 microns thick) were stained with haematoxylin and eosin and studied under the light microscope. For 3-D reconstruction, an image analyser was used to align and reconstruct the sarcocyst after microscopic images had been captured with a charge-coupled device (CCD) camera. All the cysts best fit into the type 4 category. This classification is generally useful, although cyst wall characteristics and zoite size appear to be the most reliable criteria for classification. The cyst width averaged 77 microns (range, 30-137.5 microns). Cyst walls were smooth, had no cytophaneres and were less than 1 micron thick. No secondary cyst wall or surrounding inflammation was evident. Numerous cyst merozoites with diameters averaging 1 micron filled the cyst lumen. Although septa were not apparent, in many cysts, zoites were arranged in a unique, curvilinear fashion that suggested their presence. 3-D reconstruction showed the sarcocyst to be a long, tortuous "cylinder" with no branching or other distinguishing feature.
Factors affecting the mechanical transmission of rotavirus by the legs and wings of the housefly, Musca domestica L., were examined in a laboratory study. Rotavirus was picked up when houseflies walked on thin smears of clarified rotavirus suspensions. The addition of glycerol, which increased viscosity of the virus suspension, and particulate human feces slightly increased the proportion of flies contaminated with virus. However, the addition of glycerol greatly reduced the average number of virus particles picked up per fly, whereas feces greatly increased the number of particles. The proportion of flies with virus-contaminated legs, which transferred virus to > 1 contact surface, was increased by longer contact time with the surface and when the contact surface was agar instead of glass. Most virus particles were deposited on 1st contact with the surface. Most flies dislodged virus particles inoculated on the underside of their wings soon after the start of simulated flight. Our data indicated that the nature of the virus-suspending medium has a greater effect on the level of virus contamination than on the ability to become contaminated. The importance of walking as a mode of virus transport depends on the nature of the contact surface, the risk of the contaminated fly settling first on a surface likely to come into contact with humans, and fly numbers.
A total of 1131 Police Field Force personnel were screened serologically for schistosomiasis in Malaysia. A total of 150 (13.3%) were tested positive or borderline. Stool samples from 75 of these cases were however all negative for schistosome eggs. This survey suggests that Police Field Force personnel may be agents for propagating the schistosome life cycle in Malaysia.
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.
A new sanguinicolid blood fluke, Parasanguinicola vastispina, is described from sea bass Lates calcarifer cultured in Malaysia. It is distinguished by its massive armature and widely spaced genital pores, the female pore being pre-ovarian. P. vastispina inhabits the branchial arteries, dorsal aorta, mesenteric venules and renal artery of its host. No pathological effect was observed in infected fish.
Insecticide-impregnated bednets appear to be a potentially cost-effective intervention against endemic malaria in the tropics, but this has yet to be confirmed by field trials. There are two aspects to consider in assessing such trials: (1) the extent to which subjects use nets regularly and properly, and (2) the effectiveness of nets which are truly used regularly and properly in reducing malaria transmission. The second aspect is currently of primary concern, to determine if human-vector relationships for a particular at-risk population are such that bednets can be effective. But to give bednets a "fair" test in this regard requires regular and proper use in the first place. The study described here suggests they did not get a "fair" test in one field trial in Sabah, East Malaysia. The study also strongly suggests that direct observations, rather than post hoc questioning of subjects, may be essential to accurately gauge bednet usage rates. Accurate usage rates are required to determine what proportion of a population needs to use nets to reduce malaria transmission, and to evaluate the effectiveness of promotional programs over time. Direct observations can also yield valuable data on night-time activities that increase malaria risk, such as television viewing that keeps people awake and out of bednets.
Comparative studies of vector efficiency were done with the Liverpool and Malaysian strains of Aedes (Finlaya) togoi for subperiodic Brugia malayi and Brugia pahangi. The Malaysian strain of A. togoi was found to take in fewer microfilariae under the same experimental conditions than the Liverpool strain. Also, for various microfilarial densities in the host's peripheral blood, the Malaysian strain had less mean infective larvae per fed mosquito than the Liverpool strain. The microfilarial intake of A. togoi was not affected by the site of feeding on the host affected by the site of feeding on the host. Most of the mosquitoes took in fewer microfilariae than expected. It is concluded from these studies that the Malaysian strain of A. togoi is a susceptible and reasonably good vector for subperiodic B. malayi and B. pahangi. Further field studies should be carried out to determine its importance as a natural vector of Brugian filariasis.
Twenty-three species of intestinal flukes reported in man in Southeast Asia are assigned to seven families: Echinostomatidae, Fasciolidae, Heterophyidae, Lecithodriidae, Microphallidae, Paramphistomatidae and Plagiorchiidae. The majority of species belongs to the Heterophyidae and Echinostomatidae families. Common species are Fasciolopsis buski, Echinostoma ilocanum, E. malayanum, E. revolutum and Haplorchis yokogawai. The countries where large number of species were reported are Thailand (14 species), Philippines (12 species), Indonesia (8 species) and Malaysia (4 species). Only one species was recognized in Laos, and Vietnam. Several species reported in man in the other regions, were reported in animals in Southeast Asia. It is possible that these are present in humans but have not yet been reported.
Field surveillance of Cq. crassipes was conducted in an open housing estate near Kuala Lumpur using IMR traps baited with chicken and gerbils. Chicken bait attracted more Cq. crassipes. There was significant difference between chicken and gerbil as bait. The mosquitoes preferred to feed at canopy level. The parous rate was 20.41% and the infection rate for Cardiofilaria nilesi was 2.04%. None of the 120 chicken and 5 ducks, in a village close to the open housing estate, examined for microfilariae were positive. Ar. durhami and Ar. subalbatus did not support development of C. nilesi. However, Cq. crassipes is an extremely efficient vector of C. nilesi.
A survey of a total of 1,157 Indian primary school children from eight schools from urban and rural areas in and around Kuala Lumpur showed an overall
prevalence of infection with soil-transmitted helminthiasis of 89.02%. The prevalence and intensity of infection were consistently high among both school boys and girls throughout the six years of primary school. The predominant helminth was Trichuris trichiura - both as single and mixed infections. The commonest type of helminthic infection among urban primary school children was mixed infections with Trichuris trichiura and Ascaris lumbricoides. Hookworm infections, both as single or mixed infections, were more common among school children from rubber and oil palm estates in the rural areas.
Edesonfilaria cynocephali n. sp., a parasite of Cynocephalus variegatus taylori (Thomas) in Malaysia, is described. Makifilaria Krishnasamy et coll., 1981 is placed in synonymy with Edesonfilaria and the new combination E. inderi (Krishnasamy et coll., 1981) n. comb. is proposed. Edesonfilaria and the closely related genus Macacanema constitute a small evolutionary line of Filariae with a hyperspecialized oesophagus (the glandular portion lacks lumen); the line is restricted to the Indo-Malaysian region and occurs in arboreal Dermopterans, Chiropterans and Primates.
Once-yearly, mass deworming with broad spectrum anthelmintics over a period of five years among four types of communities in Malaysia resulted in an overall education in the prevalence of soil-transmitted helminthiases by one-third to two-thirds. The reduction in prevalence of infection was highest among inhabitants in semi-urban settlements (65.5%), followed by those in the rural estates (53.0%) and high-rise flats (43.9%). Soil-transmitted helminthiases were only reduced by 35.5% in the urban slums. Reduction in infection with Trichuris trichiura was better than that with Ascaris lumbricoides whereas hook-infection was completely eliminated in some of the communities surveyed. The reduction in prevalence ofsoil-transmitted helminthiases by long-term, once-yearly deworming alone, without other supplementary interventions, reinforces the potential and feasibility of regular mass-deworming as an immediate and effective measure for the control ofsoil-transmitted helminthiases. This is of great public health significance especially in highly endemic communities where some form of intervention is urgently needed and facilities for other control measures such as the improvement of environmental sanitation and nutritional status and health education are neither feasible nor possible nor immediately available.
A survey of 308,101 primary school children in Peninsular Malaysia conducted in 1979 by the School Health Services, Ministry of Health, Malaysia, revealed that 10.7% of children were infested with Pediculus humanus capitis. The prevalence rate was higher in the economically less advanced states of Terenganu (34%), Kelantan (23%), and Perlis (21%) than in the other states (4-13%). Of 14,233 school children examined in the State of Melaka, 26% of Indians, 18.7% of Malays, 6.1% of Europeans, and 0.7% of Chinese had pediculosis. The prevalence rate, which has remained unchanged over the past 5 years, does not appear to vary with age but is higher in children with long hair and those from the lower socioeconomic groups. Boys have a lower infestation rate than do girls. The higher incidence in Indians and Malays correlates well with their lower socioeconomic status in the community, and their cultural habit of maintaining longer hair than do the Chinese. The difference become less apparent in the higher socioeconomic groups.