Using seven methods of surveillance, 58 species of mosquitoes from nine genera were in Pantai and the two neighbouring villages during two visits in 1982. Ma. bonneae was the most prevalent species attracted to man. In the forest shade Ma. bonneae and Ma. dives showed activity throughout the 24 hours with peak biting during 1900-2100 hours. An. balabacensis exhibited peak activity shortly after midnight. Inside and outside house, Ma. bonneae showed similar activity except that it ceased during the day. Mansonia was only mildly zoophilic. CDC light traps gave poor yields of mosquitoes. Pyrethrum spray catch inside houses early morning did not include any Mansonia. Outdoor day resting catch included Ma. bonneae fed on man. Transmission of Brugia, probably human filariasis, by Ma. bonneae occurred in Pantai and in the two neighbouring villages. One infection in Ma. dives was found in Pantai. The monthly infective biting rate and monthly transmission potential for Ma. bonneae were estimated at the forest shade and outside the house in Pantai.
An epidemio-meteorotropic analytical study of Selangor, in the Southwest coast of Peninsular Malaysia, examines the monthly incidence of dengue for the period 1973-1982 to assess possible quantitative association with the monthly rainfall. The relationships between rainfall, abundance of A. aegypti and dengue infection during 1982 in Jinjang, a dengue-prone area in Selangor, were also examined. A quantitative association between rainfall and the number of dengue cases was found during the first wet period. The lag time between the onset of heavy rain and dengue outbreak was about two to three months. A 120% increase in the number of dengue cases was observed when the monthly rainfall was 300 mm or more. Positive associations were seen between the incidence of dengue and the Aedes house index and the Breteau index in Jinjang. The relationships between these three variables and rainfall suggest that the latter might have exerted its effect on dengue infection partly through the creation of more breeding sites for A. aegypti. Assessment of the importance of A. aegypti in the transmission of dengue in this locality was not possible because of the lack of adjustment for A. albopictus, the other known vector of dengue in the state, and for social and other environmental factors influencing infection rates. In spite of this and the interpretational problems common in aggregate studies, the present analyses have provided relatively strong statistical evidence of an association between rainfall and dengue outbreaks in Selangor, thereby indicating that it is a factor worthy of careful surveillance and monitoring.
Field observations were made on Coquillettidia crassipes during a study of Mansonia in a swamp forest ecotype in Tanjong Karang. There was an increase in abundance in July consistent with the increase in abundance of Mansonia and an increase in rainfall. The biting cycle showed a dramatic early peak during the period 1900-2000 hours. The probability of daily survival through one day for the first three gonotrophic cycles was 0.770, 0.722 and 0.759. Two of the 54 Cq. crassipes dissected were infective, with two and 25 L3 larvae of Brugia. Both subperiodic B. malayi and B. pahangi developed into L3 larvae in laboratory bred Cq. crassipes. The index of experimental infection was higher for B. pahangi. Mansonia bonneae and Ma. uniformis showed higher indices of experimental infection than Cq. crassipes for subperiodic B. malayi. It is concluded that in an endemic area with a high density of Cq. crassipes it could act as a secondary vector of Brugian filariasis.
An investigation into the seasonal changes in the population structure of Haemonchus and Trichostrongylus in tracer goats was conducted over 12 months at Serdang, an area in southern West Malaysia with year-round tropical rainfall. Successive groups of parasite-free tracer goats were grazed for a month alongside naturally infected adult goats and necropsied for worm counts 14 days after their removal from pasture. No hypobiotic larvae of Trichostrongylus were recovered. Hypobiotic larvae of Haemonchus were evident during each month of the year but accounted for only a very small proportion of the total Haemonchus burden. Very low levels were encountered from December through to June. Comparatively higher levels of hypobiosis were observed thereafter with a peak of 7.4% in September. The factors responsible for hypobiosis were not clearly defined but the phenomenon was associated with increasing levels of soil moisture storage. Host resistance, adult worm population of tracers and population of ingested L3 were ruled out as possible inducing factors.
A retrospective study of 224 cases of snake bites in Bukit Mertajam Hospital over a two year period is reported. Snake bites formed 0.5% of the total and 1.7% of the Medical and Paediatric admissions and accounted for 0.3% of the total hospital deaths. The commonest snake species involved was the Malayan pit viper. 89% of the patients escaped with negligible poisoning and went home in less than seven days. Most of the bites were inflicted in the lower limbs and occurred in the dark. Only 5% of the patients were given anti-venom, of whom one-third had adverse reaction.
A marked seasonality of births for the two main ethnic groups of peninsular Malaysia, far exceeding the cyclic fluctuations in births in the United States and Canada, was reported for the 1960s. A 36% excess of births over the average monthly number was observed among Malays each January. Among the ethnic Chinese in Malaysia a regular periodicity in the numbers of births was also found, but it was far less marked and the peak occurred in October or November. The peaks in both groups were due in large measure to conceptions that correlate with religious observances or holidays. Here I report on cyclic birth patterns in peninsular Malaysia for the period 1970-1985. Rapid economic development has occurred during this time and has brought with it demographic changes, such as a massive rise in contraceptive use and a decline in birth rates. These demographic changes have been accompanied by the loss of the pronounced seasonal pattern of births among the Malays. The seasonality of Malay births is now of roughly the same magnitude as the seasonality in the United States and Canada, whereas seasonality of births among the Chinese in Malaysia remains essentially unchanged.
The levels of nematode egg production in goats and the availability of infective larvae (L3) on pasture were investigated on a dairy unit in New South Wales, Australia. The output of eggs by adult goats was always above 300 epg. The profile of the graph of larval availability in herbage paralleled those for temperature and rainfall, suggesting that larval peaks occurred when the temperature and availability of moisture were optimal. The dominant genus was Trichostrongylus, followed by Haemonchus, then Ostertagia. A larger proportion of Haemonchus larvae in the cultures of faeces were collected during the summer months.
Between January 1987 and February 1990 Babesia infections were detected in 320 dogs in Germany by means of microscopical and/or serological methods. It was found, that 316 dogs were infected with Babesia canis and 4 animals with Babesia gibsoni. Of the Babesia-canis-positive dogs 184 were abroad up to 4 months before diagnosis, mainly in France, Spain and Italy, but also in Hungary, Greece, Jugoslavia, Portugal, Morocco, Togo, Pakistan, Sri Lanka, Malaysia, Turkey, Romania, Austria and the Netherlands. For further 36 dogs the possible place of infection for Babesia canis could not be clarified geographically. 5 dogs each were simultaneously infested with Rhipicephalus sanguineus and Dermacentor reticulatus, respectively. The four dogs infected with Babesia gibsoni were previously in Sri Lanka (2), Brazil (1) or Algeria/Kenya (1). In 88 dogs from the Offenburg/Lahr/Freiburg area, which were not abroad, infections with Babesia canis were diagnosed from January to June as well as from September to December, however, most cases occurring in April and May. Of these dogs approximately 20% were found to be infested with Dermacentor reticulatus. These ticks were also collected on the vegetation in the Offenburg area. Therefore, an endemic focus of Babesia canis can be deduced in the area of Offenburg/Lahr/Freiburg and Dermacentor reticulatus as vector also in Germany.
This study describes the status of viral encephalitis in Perak, Malaysia during the year 1990. In addition, 14 cases selected from Penang and Perak during the years 1989 and 1990 are presented, with data showing titers of neutralizing antibodies against Japanese encephalitis virus (JEV) and dengue 2 virus, titers of antibodies against JEV and dengue virus antigens as determined by DEIA, and a comparison of these with the presence of IgM to JEV and dengue virus. These data show that there probably is far more viral encephalitis due to JEV in Malaysia than the national figures reflect.
Marine biofouling causes problems to marine structure and obstructs condenser tubes in cooling systems which use sea water as the coolant. The main purpose of this study is to investigate the seasonal ecology of biofouling organisms such as the green mussel, Perna viridis, the dominant fouling species in the Eastern Johore Straits at the Senoko Power Station. The spawning time and its relationship with environmental conditions were studied. The physical, chemical and biological conditions of the sea at Senoko were monitored for a year. Settling slides were used to study the fouling succession in different monsoon seasons. The study showed that there were two main spawning peaks for the green mussel and that these peaks occurred during the intermonsoon months of November and April. These peaks were also correlated with the bimodal patterns for salinity, dissolved oxyen, bivalve veliger larval density and total plankton biomass of the Eastern Johore Strait water. Succession patterns were similar during the two monsoon seasons, however, the rate of fouling was probably greater during the southwest monsoon months. It is therefore advisable that the control or reduction of biofouling in Eastern Johore Strait should take into account the seasonal fluctuations and spawning of the fouling organisms.
A study on population patterns of the parasitoid Spalangia endius Walker at a dumping ground near Kuala Lumpur city showed that the percentage of S. endius adult emergence varied seasonally. During the relatively heavy rainfall months of August and November 1988, and January, March, and April 1989, the population of S. endius adult emergence were low (0-14.2%) compared to the less rainy months of July, September, and December 1988, and May 1989 (29.3-39.6%). This information could be useful in formulating strategies to reduce house fly population at the refuse dumping ground through integrated pest management programs.
The superovulatory response to gonadotrophin treatment during different months of the year was investigated in Kambing kacang goats, a tropical breed, in Malaysia. Sixty-three cycling does, fitted with progesterone impregnated intravaginal sponges for 17 days, received two days before sponge withdrawal, an intramuscular injection of either 10, 15 or 20 mg of follicle stimulating hormone (FSH) or 500, 1000 or 1500 iu of equine chorionic gonadotrophin (eCG). The dose of FSH was divided into four decreasing daily doses and each daily dose was subdivided into two and administered at 07.00 and 19.00. Fifty-four does detected in oestrus were mated with fertile bucks. The ovarian response was determined by laparoscopy and eggs were recovered surgically five or six days after oestrus. The ovulatory response (mean +/- standard deviation) based on corpora lutea was higher in the FSH (13.4 +/- 8.4 corpora lutea per doe, n = 20) than the eCG-treated groups (6.4 +/- 5.1 corpora lutea per doe, n = 25) but the difference was not significant (P greater than 0.05). Does responded to gonadotrophins throughout the year with more than 50 per cent of does responding during the rainy months compared with less than 35 per cent responding during the dry months. This difference was statistically significant (P less than 0.05). Egg recovery was better in the FSH (6.8 +/- 5.3 per doe, n = 20) than the eCG groups (3.0 +/- 3.8 per doe, n = 21) but the difference was not significant (P greater than 0.05).
Faecal worm egg counts of goats from two farms in Penang Island, West Malaysia, were monitored over a period of 14 months. The faecal egg count pattern followed that of total rainfall. The humid tropical environment was favourable for the development of various species of trichostrongylid nematodes, namely Haemonchus contortus, Trichostrongylus spp., Oesophagostomum spp. and Cooperia spp. Generally, H. contortus was observed to be the predominant species, more so in the monsoon months of the year.
The relationship among body size (as indicated by wing length), age (as indicated by parity dissections), and malaria infection were observed in host-seeking Anopheles maculatus Theobald females collected in aboriginal villages of peninsular Malaysia. Both ELISA and salivary gland dissections were used to determine malaria infection. The wings of parous females were significantly longer than those of nulliparous females, suggesting that larger females live longer than smaller ones, and thus have a higher vectorial capacity. Body size differences were not detected between infected parous and uninfected parous females. Females infected with only oocysts were significantly larger than females infected with sporozoites. No correlation was found between the number of oocysts or sporozoites and body size in this small sample.
Dengue fever (DF) has been endemic in Malaysia since 1902 and reached epidemic proportions in 1973. The incidence rate of the disease in 1973 was 5.4 cases per 100,000 and reached 10.4 cases per 100,000 in 1987. The Chinese are the main ethnic community affected showing an overall morbidity rate of 9.0 cases per 100,000 followed by Malays 2.9 cases per 100,000 and Indians 2.4 cases per 100,000. The ethnic race ratio between Chinese, Malays and Indians which was 3.7:1:1.3 in 1975 reached 3.7:1:0.9 in 1987. The attack rates were observed to be higher in the males. The mean male:female ratio among Chinese was 1.1:1, while for Malays and Indians it was 1.5:1. The age-specific morbidity rate was highest in the 10- to 19-year age group followed by the 20- to 29-year age group. Epidemics of dengue fever were found to occur seasonally with the appearance of two peaks, viz. one in June and the other in August. Dengue fever, a rural disease before, has established itself as an urban disease.
Publication year=1992-1993
Eggs of temperate Aedes albopictus populations are cold hardy and can diapause, but tropical populations are not cold hardy and cannot diapause. Heterozygotes possess intermediate diapause and cold hardiness. Males of a tropical strain from Malaysia with a distinctive genetic marker were released into an existing temperate population in East St. Louis, Illinois. Subsequent egg samples from the release site had genetic marker frequency of up to 24%. Reduced cold hardiness and decreased diapause incidence were also observed in the release site population. No such changes occurred at a nearby control site. The rank order of overwintering survival of eggs at the release site was: Aedes triseriatus > temperate Ae. albopictus > hybrid temperate/tropical Ae. albopictus > tropical Ae. albopictus. Eggs collected from the release population the next summer showed total absence of the genetic marker; presumably carriers were removed by the winter.
Collections of anopheline mosquitos were made twice monthly for 13 months from a cow-baited trap in two villages, Kampung Permatang Rawa and Sungai Udang Kecil, on mainland coastal Penang, Malaysia. Each collection period was six hours from sunset. Unquantified larval collections were made regularly in each area. Although the villages were only about 50km apart, and each had extensive, irrigated rice-fields in its vicinity, the species abundance and the seasonal fluctuations differed significantly. In Kampung Permatang Rawa Anopheles sinensis and An. peditaeniatus were dominant in prevalence, whereas in Sungai Udang Kecil An. indefinitus and An. lesteri paraliae were most common and An. peditaeniatus was relatively rare. The rice growing schedules in the two areas differed, but there was a moderate correlation between the abundance of several species and the rice-growing pattern. There was no correlation at either site with rainfall.