In an effort to develop a more effective technique in dispersing a microbial control agent, Bacillus thuringiensis (Bt), a truck-mounted ultra low volume (ULV) generator (Scorpion) was used to disperse B. thuringiensis israelensis (Bti) and Bti with malathion. Complete larval and adult mortalities for all tested mosquito species within the first 70-80 feet from the ULV generator were achieved. Beyond that distance less than 50% mortality was achieved as insufficient sprayed particles reached the area. A minimum of 10(3) Bti colony forming units per ml is required to cause 100% larval mortality. The sprayed Bti larvicidal toxins were persistent in the test water 7 days post ULV. The effectiveness of B. thuringiensis jegathesan (Btj), a new mosquitocidal Bt serotype was also evaluated. Similar mortality results as Bti were achieved except that the Btj toxins underwent degradation in the test water, since less than 50% less in larval mortality was observed in 7 days post ULV samples. This ULV method has the potential to disperse Bt and malathion effectively for a simultaneous control of mosquito adults and larvae.
The effect of testosteron on Ascaris suum worm load and larval growth were studied. The results revealed that the effect of testosterone on A. suum infection was dose dependent. Administration of 0.5 mg testosterone propionate (TP) for 18 days significantly increased the mice susceptibility to A. suum infection (66.2 ± 11.15 larvae) (mean ± S.E.) when compared to the control. Higher dosage of testosterone (1.0, 2.5 or 5.0 mg TP) did not show any significant effect. The present experiment also showed that administration of testosterone (0.5 mg TP) for 7 days increased the host susceptibility (86.1 ± 5.86 larvae) to A. suum infection compared to the control (14.6 ± 1.71 larvae) (P < 0.001). Similar results were found when the hormone was administered for 14 and 28 days. On the contrary, when gonadectomised mice were given 0.5 mg TP, the level of susceptibility increased (P < 0.001). It is believed that testosterone indirectly influence the parasitic infection through its effect on the lymphoid organs.
Kesan testosteron terhadap bebanan dan pertumbuhan larva Ascaris suum telah dikaji. Hasil kajian menunjukkan bahawa pengaruh testosteron terhadap infeksi A. suum adalah bergantung kepada takaran hormon yang diberikan. Didapati hanya takaran 0.5 mg testosteron propionat (TP) yang diberikan selama 18 hari meninggikan kerentanan mencit (66.2 ± 11.15 larva) (min ± S.E.) terhadap infeksi parasit jika dibandingkan dengan kawalan (38.0 ± 7.13 larva) (P>0.05). Takaran testosteron yang lebih tinggi (1.0, 2.5 atau 5.0 mg TP) tidak menunjukkan kesan yang jelas. Hasil percubaan juga menunjukkan bahawa pemberian hormon (0.5 mg TP) selama 7 hari boleh meningkatkan kerentanan perumah (86.1 ± 5.86 larva) terhadap infeksi A. Summ. Perbandingan dengan kawalan (14.6 ± 1.71 larva) dan menunjukkan perbezaan yang nyata pada P < 0.001. Begitujuga dengan pemberian hormon selama 14 dan 28 hari. Sebaliknya gonadektomi telah mengurangkan kerentanan mencit terhadap infeksi A. suum. Walau bagaimanapun, kesan sebaliknya didapati apabila mencit yang gonadektomi itu diberi suntikan 0.5 mg TP (P < 0.001). Hormon testosteron dipercayai mempengaruhi corak infeksi parasit secara tidak langsung dengan mempengaruhi perkembangan organ-organ limfoid.
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 malaria survey was conducted to examine the presence of common clinical features of malaria in individuals living in an endemic area of malaria. The overall infection rate was 11.0% with 7.5% and 3.5% infected with Plasmodium vivax and Plasmodium falciparum respectively. The mean parasitaemia level of both species was 2905.9 parasites/microliter blood, with the mean parasitaemia level of P. vivax and P. falciparum at 682.7 parasites/microliter blood and 6981.7 parasites/microliter blood respectively. The infection rates were higher in the younger age group. Hepatomegaly, hepatosplenomegaly and clinical anaemia were significantly associated with malaria. None of the patients were febrile. In conclusion, in low endemic areas, the presence of clinical anaemia, hepatomegaly and hepatosplenomegaly in afebrile individuals could be considered as useful criteria for the presence of asymptomatic parasitaemia. It is important to carry out laboratory diagnostic investigations, to ensure all the asymptomatic parasitaemia which act as reservoirs are detected and treated.
Four hundred and thirty five (435) cases 0f sexually transmitted infections (STIs) were notified from 20 (twenty) primary care clinics throughout Malaysia from June 1999 till September 2000 using the syndromic approach of STI management, adapted by the Ministry of Health based upon the criteria set by the World Health Organisation (WHO). Gonorrhoea was the most prevalent STI reported (30.34 %), followed by candidiasis (28.05%), syphilis (15.17%) and non-specific urethritis (NSU) — 14.02%) . As seen in most other parts of the world, the younger age groups (those between twenty and thirty nine years old) were found to be more commonly infected with STIs. Initial analysis shows that systematic data collection based on the syndromes and clear—case definitions (algorithms for the syndromic approach} need to be developed and added further to the current manual that is being developed for the health and medical staff at the operational it level. Exploration and expansion of behavioural surveillance research, management information systems of the syndromic approach, and development of new or additional strategies in the manual for the staff too, also need improvement. The Ministry of Health is also concerned about the quantity and quality of the available data based upon syndromic management of STI as compared to laboratory based criteria. Since this programme is very much client centered, the adoption of this approach generally might offer substantial improvements in the quality and effectiveness of STI care, either within the public or the private health care settings in Malaysia.
This study determined the prevalence of ocular manifestation of vitamin A deficiency in Orang Asli (Aborigine) children. Night blindness was found in 16.0% of the children, conjunctiva xerosis in 57.3%, Bitot's spot in 2.8%, corneal xerosis in 0.5% and corneal scars in 5.6%. These findings show that history of night blindness had sensitivity, specificity and predictive value (positive) of 47.2, 98.1 and 96.2%, respectively, compared with the standard diagnosis procedure using luxometer readings.
The rapid detection of dengue infection in mosquito vectors is important for early warning to forestall an outbreak. Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) provides a rapid method for dengue detection in man and mosquitoes. An RT-PCR kit developed by the Medical Entomology Unit, Institute for Medical Research to detect dengue infection in mosquitoes, was tested for its shelf life at 3 storage temperatures: room temperature, refrigerator and freezer. Test kits were tested once every 3 days for kits stored at room temperature, and once every week for those stored at refrigerator and freezer temperatures. The results showed that the test kit could only be stored above its recommended storage temperature of -20 degrees C for not more than 3 days. DNA 100 bp markers in the kits appeared to be stable at the tested temperatures and were usable up to the 20th day when stored at 2 degrees C and below.
Artificial feeding of mosquitoes with blood meal is an important technique in the studies of mosquito feeding. Owing to the difficulty in obtaining suitable artificial membranes for mosquito feeding from other sources, several easily obtainable membranes in Malaysia were tested for their suitability as a replacement. Skin of chicken, fish, and salted sausage were obtained and tested against cattle skin membrane as a control. The results showed that cattle skin is still the most favorable membrane to be used, with full engorgement rate of around 57% using fresh human blood. However, processed chicken skin was shown having potential for further testing since with feeding using human blood kept overnight at 4 degrees C, an engorgement rate of 50% was obtained.
Giardia duodenalis is an intestinal parasite that causes diarrhoea and malabsorption in children. The parasite also infects AIDS patients with a weak immune system. A study was carried out on six local isolates of Giardia duodenalis (110, 7304, 6304, M007, 2002 and 6307) from faeces of Orang Asli patients admitted to the Gombak Hospital. WB, a reference pathogenic strain from human and G. muris from a wild mouse, were commercially obtained from the American Type Culture Collection (ATCC). All the isolates were cultured axenically in TYI-S-33 medium. Two sets of primers were used for the techniques: primers LP1 and RP1 and primers LP2 and RP2. The sets of primers amplified giardine gene of 171 bp and 218 bp in sizes respectively. The study showed that the two sets of primers could detect G. duodenalis to the genus and species level specifically.
A study of chikungunya virus was carried out to establish Reverse Transcriptase- Polymerase Chain Reaction (RT-PCR) as a rapid detection technique of the virus. The susceptibility of lab-colonized Aedes aegypti to chikungunya virus was also determined. Artificial membrane feeding technique was used to orally feed the mosquitoes with a human isolate of chikungunya virus. A total of 100 fully engorged female Ae. aegypti were obtained and maintained for 7 days. Seventy of them survived and then pooled at 10 individuals per pool. Total RNA was extracted from the samples and RT-PCR amplifications were carried out. Five out of 7 pools showed positive PCR band at 350-bp, indicating Ae. aegypti is a potential vector of chikungunya virus. The minimum infection rate (MIR) was 71% within these laboratory colonies. RT-PCR is a sensitive technique that is useful in detecting infected mosquitoes in epidemic areas. This technique can de used as a rapid detection method and provide an early virologic surveillance systems of chikungunya virus infected mosquitoes.
The bioefficacy of indoor residual-sprayed deltamethrin wettable granule (WG) formulation at 25 mg a.i./m2 and 20 mg a.i./m2 for the control of malaria was compared with the current dose of 20 mg/m2 deltamethrin wettable powder (WP) in aboriginal settlements in Kuala Lipis, Pahang, Malaysia. The malaria vector has been previously identified as Anopheles maculatus. The assessment period for the 20 mg/m2 dosage was six months, but for the 25 mg/m2 dosage, the period was 9 months. Collections of mosquitoes using the bare-leg techniques were carried out indoors and outdoors from 7:00 PM to 7:00 AM. All mosquitoes were dissected for sporozoites and parity. Larval collections were carried out at various locations to assess the extent and distribution of breeding of vectors. A high incidence of human feeds was detected during May 2005 and a low incidence during January 2005 for all the study areas. Our study showed that deltamethrin WG at 25 mg/m2 suppressed An. maculatus biting activity. More An. maculatus were caught in outdoor landing catches than indoor landing catches for all the study areas. The results indicate that 25 mg/m2 WG is good for controlling malaria for up to 9 months. Where residual spraying is envisaged, the usual two spraying cycles per year with 20 mg/m2 deltamethrin may be replaced with 25 mg/m2 deltamethrin WG every 9 months.
A study was carried out to investigate correlation between presence of specific microalgal species and Leptoconops biting midge larvae in its breeding habitats. Sand samples containing microalgae were collected from the beach where the midges were most commonly biting and from sand beaches which are potential as breeding habitats of Leptoconops. The survey covered sand beaches from 12 seperate islands. At all sites, the Bacillariophyta constituted the largest representatives of the microalgae community with the majority from the Naviculaceae family. A total of 24 microalgal species were identified from the sand samples collected from the study sites. Sand samples from Kentot Kecil Island had the highest number of algal species (11.0) and the highest algae species diversity ( Shanon-Weiner Diversity Index, H' = 0.884). Besar Island (Johor) had the lowest number of algal species (2.0) whereas Tengol A Island had the lowest algae species diversity (H'=0.234). Highest similarity index was recorded between sand samples collected from Tengol A Island and Tengol B Island (75.0%) followed by Besar Island (Melaka) and Tengol B Island (62.0 %). The variation between other islands were relatively high. Virtually many kinds of algae were found where Leptoconops were breeding but Fragilaria intermedia, Mastigloia minuta and Navicula advena were particularly common.
This study was designed to compare the sensitivity and specificity of detecting sensorineural hearing loss (SNHL) using the transient-evoked otoacoustic emissions (OAE) machine (the Madsen TE Echoscreen) and automated auditory brainstem response (AABR) machine (the Sabre Compac portable AABR) in term neonates exposed to severe hyperbilirubinaemia.
A study was conducted to examine the persistency of transovarial dengue virus type 2 (DEN-2) in a Selangor strain of Aedes aegypti mosquitoes. Two hundred 4-5 day old female mosquitoes were fed with blood containing dengue virus. The infected mosquitoes were reared to the 7th generation; each generation was screened for the virus using immunological staining methods. The virus was detectable until the 5th generation but absent in the 6th and the 7th generations. Therefore, dengue virus type 2 can be transmitted transovarially in Aedes aegypti mosquitoes until the fifth generation under laboratory conditions.
The adult population and species composition of mosquitoes collected in Ranau, Sabah are described. A total of 5956 mosquitoes representing 8 genera and 41 species were collected using human landing catch, indoor and outdoor. Anopheles maculatus was the most common species (15.6%) followed by Culex quinquefasciatus (12.8%), Culex pseudovishnui (12.1%), Anopheles balabacensis (11.1%), Culex vishnui (9.7%), Aedes vexans (9.6%), Culex tritaeniorhyncus (6.6%), Anopheles donaldi (5.6%) and others in very small percentage.
In this study, artificial membrane feeding technique was used to orally feed Aedes aegypti with dengue and chikungunya viruses. Virus detection was carried out by reverse transcriptase polymerase chain reaction. The study did not detect dual infection of Ae. aegypti with dengue and chikungunya virus from the same pool or from individual mosquitoes. Oral receptivity of Ae. aegypti to chikungunya virus was higher than that of dengue virus.
Dengue 2 and 4 viruses obtained from dengue-infected patients were maintained in a C6/36 Aedes albopictus Skuse cell line and used to infect adult female Aedes aegypti mosquitoes. Each serotype was mixed separately with fresh human erythrocytes and fed to adult female mosquitoes using an artificial membrane feeding technique. Fully engorged mosquitoes were selected and retained at 26 degrees C, 28 degrees C and 30 degrees C to observe dengue virus development in Aedes vectors. Virus detection was carried out by reverse-transcriptase polymerase chain reaction (RT-PCR). The virus was first detected on Day 9 at 26 degrees C and 28 degrees C and on Day 5 at 30 degrees C for both dengue 2 and 4. The study shows the incubation period of the viruses decreased when the extrinsic incubation temperature increases.
In Peninsular Malaysia, a large proportion of malaria cases occur in the central mountainous and forested parts of the country. As part of a study to assess remote sensing data as a tool for vector mapping, we conducted entomological surveys to determine the type of mosquitoes, their characteristics and the abundance of habitats of the vector Anopheles maculatus in malaria endemic areas in Pos Senderot. An. maculatus mosquitoes were collected from 49 breeding sites in Pos Senderot. An. maculatus preferred to breed in water pockets formed on the bank of rivers and waterfalls. The most common larval habitats were shallow pools 5.0-15.0 cm deep with clear water, mud substrate and plants or floatage. The mosquito also preferred open or partially shaded habitats. Breeding habitats were generally located at 100-400 m from the nearest human settlement. Changes in breeding characteristics were also observed. Instead of breeding in slow flowing streams, most larvae bred in small water pockets along the river margin.
Iron deficiency and anaemia affect millions of children worldwide. This study aimed to investigate the effect of iron deficiency with or without anaemia on cognitive functions, specifically with short-term memory, attention and visual motor coordination in children. A total of 173 primary school children was enrolled. Cognitive functions were assessed using the Wechsler Intelligence Scale for Children. Three sub-tests were selected to assess processing speed (coding test), immediate auditory memory (digit span test) and visual processing and problem solving ability (maze test). The results showed significant correlation between age and coding test (r =0.38, p< 0.001), digit span test (r =0.16, p = 0.028), and maze test scores (r =0.28, p< 0.001), and the total sub-test scores (r=0.43, p < .001). After age adjustment of the cognitive function tests, iron deficient children without anaemia scored significantly lower than the healthy children (p< 0.001) on coding test, while iron deficient children with anaemia and iron deficient children without anaemia scored significantly lower (p< 0.001) than the healthy counterparts on maze test. No significant differences were observed on digit-span score among the groups. This study confirms the negative effect of both iron deficiency and iron deficiency anaemia on processing speed and visual motor coordination in children.