Capillaria hepatica infection in wild rodents collected from the States of Kelantan, Selangor and Johore in Peninsular Malaysia since 1973 is reported. A total of 1,258 rodents consisting of 20 species of house, field and forest rats, and 7 species of squirrels were examined for the parasite and 17 species consisting of 111 murids and 1 flying squirrel were found infected. The house rat, Rattus norvegicus had the highest prevalence rate, followed by 3 species of field rats, R. tiomanicus, R. argentiventer and Bandicota indica. The prevalence of infection was low among forest rats with the exception of Lenothrix canus. Only 1 flying squirrel, Hylopetes spadiceus was found with the parasite. The prevalence of infection in relation to the host behaviour and habitats was discussed. C. hepatica appears to be widespread throughout Malaysia with a wide range of hosts among rodent species. Some new host records are presented herein.
An enzyme-linked immunosorbent assay using excretory-secretory antigens of the second stage larvae maintained in vitro was used to determine the seroprevalence of Toxocara antibodies in Orang Asli (aborigines) of Peninsular Malaysia. The mean + 3 SD optical density of 30 healthy subjects was used as the cut-off point. Overall prevalence was found to be 31.9%. No significant relationship was found between positive rates with sex and age groups, though children between 0 to 9 years recorded the highest positive rates. Eosinophil counts were found to be closely related to the proportion of positivity to toxocaral infection and mean optical densities. There was some degree of cross-reaction with Trichuris trichuria positive sera.
The distribution of anti-toxoplasma antibodies among the aborigines in Malaysia and its association with other soil transmitted infections and eosinophilia were studied. A total of 415 serum samples were collected and tested by IFA test. Overall prevalence was 10.6%, lower than previously reported. The antibody titers showed a unimodal distribution peaking at 1:8 dilution. There was a higher proportion of high antibody titer (> 1:128) in the adult compared to the children with no significant difference in prevalence rate by sex. The pattern of infection does not differ from other soil transmitted infections and there was no association between raised Toxoplasma antibodies with eosinophilia.
In Peninsular Malaysia, only Wuchereria bancrofti and Brugia malayi are reported to cause human filariasis. Brugia pahangi infects many of the same animal hosts as the zoonotically transmitted subperiodic B. malayi. There is a well-recognized need for improved diagnostic techniques for lymphatic filariasis. Parasite antigen detection is a promising new approach, and it will probably prove to be more sensitive and specific than clinical, microscopic and antibody-based serological methods. We recently generated monoclonal antibodies (MAb XC3) from in vitro culture products of adult B. pahangi (B.p. IVP). Filarial antigenemia was quantitated in various hosts including the sera from 6 Malaysian Aborigines with acute lymphatic filariasis. In hosts infected with brugian filariasis and dirofilariasis, antigenemia was scored ranging from 90 ng/ml to 960 ng/ml. None of the control animal and human sera had antigenemia above 90 ng/ml. In addition, MAb XC3 and B.p. IVP were applied in several seroepidemiological surveys among household cats in Kuala Selangor in order to correlate information gathered for future studies of possible cases of human infection. Out of the 81 cats surveyed, 10 (12.35%) and 5 (6.17%) were parasitologically positive for B. pahangi and B. malayi, respectively. However, 21 (25.92%) were antigenemia positive when serologically investigated with MAb XC3. Antifilarial antibodies to B.p. IVP by direct ELISA showed very high cross-reactivity with non-filarial gut worm infections. 16 (19.75%) cats had reciprocal titers ranging from 320 to 2,560. Only 1 (1.23%) cat from this group was antigenemic.
A study of health status of Orang Asli population (based on physical examination findings) was conducted in 4 villages in Pos Piah, Sungai Siput Perak, Malaysia. In all 356 individuals between 4 months-72 years old (178 males and 178 females) participated in this study. Poor general health status, physical and mental handicaps were seen in 7.8%, 0.3% and 0.3% of the population, respectively. About one-fifth of the population had dental caries. Splenomegaly, hepatomegaly and hepatosplenomegaly were among the commonest abnormalities with the occurrence rates of 19.8%, 13.7% and 6.7%, respectively, being detected in the population. About one-fifth of the population showed signs suggestive of protein-energy deficiency; whilst less than 5% showed signs indicative of riboflavin, iodine and iron deficiencies. Vitamin A deficiency was the commonest nutritional deficiency identified in this community with almost 38.4% of them showing signs of the deficiency. The commonest skin infection was scabies.
A rapid diagnostic system for scrub typhus using nested polymerase chain reaction (PCR) was applied to clinical samples from Malaysian Aborigines. Whole blood from twenty-four patients suspected of scrub typhus infection were tested using nested polymerase chain reaction and sera were evaluated by the indirect immunoperoxidase test. Antibody responses towards Rickettsia tsutsugamushi were observed in seventeen patients with the majority having high titers of IgG antibodies. Seven patients were seronegative. The nested PCR amplified R. tsutsugamushi DNA from six patients, of which two were negative serologically and four had high titers of IgG antibodies. Second samples collected seven days after treatment were negative by PCR testing. Nested PCR is highly sensitive and specific and may be used to provide rapid confirmation of scrub typhus cases in endemic region.
Three MAbs 1C4.2D8, 1C4.2C4 and 1C4.1F5 were produced using sonicated adult worm antigens of Angiostrongylus malaysiensis and they were found to be secreters of IgG1. The MAbs 1C4.2C4 and 1C4.2D8 were found to react with antigens of A. malaysiensis and cross-react with the closely related A. cantonensis but not with other helminths. A total of 108 human sera collected from Orang Asli (aborigenes) from Grik, in the State of Perak were tested for A. malaysiensis infection using the MAb-ELISA. MAb 1C4.1F5 and 25 (23%) were positive. Twenty of these positive samples were tested with the MAb 1C4.2D8 and none was found to be positive.
A community study on the age and sex related prevalence, intensity infection and frequency distribution of Ascaris, Trichuris and hookworm was carried out in 205 Orang Asli (Aborigines) children (95 boys, 110 girls) aged 1-13 years. The overall prevalence of Ascaris, Trichuris and hookworm was 62.9%, 91.7% and 28.8%, respectively. Almost two-thirds of the children were infected with moderate and severe intensity infection of Trichuris, 46.3% had moderate to severe intensity infection of Ascaris. However only 1.5% had moderate intensity of hookworm infection. The prevalence and mean intensity infection (measured by eggs per g) of Ascaris was age-dependent; lower in age group 1-4 years reached peak and stable at age group 5 years and above. The prevalence of Trichuris was high in all age groups and it fluctuated with age; the mean intensity of infection of Trichuris (measured by eggs per g) was age-dependent. Hookworm infection also rose with age and reached peak at 5-6 years, following that the prevalence declined. The frequency distributions of Ascaris, and hookworm were overdispersed. A strong positive correlation (p < 0.001) were observed between Ascaris and Trichuris and between hookworm and Trichuris. A positive correlation (p < 0.01) were also observed between Ascaris and hookworm.
The effect of permethrin impregnated bednets on Anopheles maculatus Theobald was studied in four villages in Pos Betau, Pahang, Malaysia from August 1990 to July 1992. Collections of mosquitos were carried out indoors and outdoors from 1900 to 0700 hours. All mosquitos were dissected for sporozoites and parity. In May 1991 two villages received bednets impregnated with permethrin at 0.5 g/m2 and two villages received placebo bednets. There was a significant difference in the sporozoite and parous rates between the treated and control villages after the distribution of bednets (p < 0.05). There was no significant difference in the bites/man/night of An. maculatus between the pre and post treatment periods in the control villages. However there was a significant difference in bites/man/night between pre and post treatment in the treated villages (p < 0.001).
The Aborigines or Orang Asli in Peninsular Malaysia who are still seminomadic are known to have a close association with dogs. In this study, enzyme-linked immunosorbent assay (ELISA) was used to detect anti-Sarcoptes scabiei var canis antibodies in this community as a measure of exposure to the mite. Out of 312 Orang Asli tested, 24.7% were positive for polyvalent anti-Sarcoptes antibodies. No significant difference was found between the positive rates in males (26.1%) and females (23.6%). Only 1.9% were positive for IgA and none was positive for IgE anti-Sarcoptes antibodies. Since there were very few patients with clinical manifestation of scabies, there is a possibility that continuous exposure to the dogs mite confers cross-protective immunity in the community against human scabies.