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Fulltext Studies on the effect of lambdacyhalothrin on Anopheles maculatus Theobald and its response to residual spraying at Jeram Kedah, Negeri Sembilan, Malaysia

Vythilingam I, Chiang GL, Mahadevan S, Eng KL, Chan ST, Singh KI

Southeast Asian J. Trop. Med. Public Health, 1993 Mar;24(1):138-42.
PMID: 8362288

A field trial was carried out to study the effect of lambdacyhalothrin on Anopheles maculatus in trap huts in Jeram Kedah, Negeri Sembilan, Malaysia. Two trap huts were built, of which one was sprayed with lambdacyhalothrin at a dosage of 25 mg ai/m2 and the other served as control. Eight collectors commenced collecting mosquitos from 1900 to 2400 hours, two each indoors and outdoors. Bioassay was also carried out in the treated and control huts to determine susceptibility of adult mosquitos to lambdacyhalothrin. In the treated hut more mosquitos were present during the pre- spraying period. Lambdacyhalothrin gave a mortality of 100% against An. maculatus for 8 months.
Fulltext Capture-recapture studies with Anopheles maculatus Theobald (Diptera: Culicidae) the vector of malaria in peninsular Malaysia

Chiang GL, Loong KP, Chan ST, Eng KL, Yap HH

Southeast Asian J. Trop. Med. Public Health, 1991 Dec;22(4):643-7.
PMID: 1687932

Mark-release-recapture experiments were undertaken in January 1989, in Pos Betau, Pahang, Malaysia, with the malaria vector Anopheles maculatus. On two consecutive nights, 121 and 175 blood-fed mosquitos were released. A mean recapture rate of 11.5% and survival rates of 0.699-0.705 with an estimated oviposition cycle period of 2.35 days were obtained from the releases. About 68% of all recaptures were taken within a distance of 0.5 km from their release points and the longest detected flight was 1.6 km. No heterogeneity was found between indoor and outdoor biters of An. maculatus.
Biochemical genetic relationship in three taxa of the malaria mosquito Anopheles balabacensis complex

Yong HS, Cheong WH, Chiang GL, Dhaliwal SS, Loong KP, Sarjan R

Comp. Biochem. Physiol., B, 1983;76(3):611-3.
PMID: 6641178

Three taxa of the malaria mosquito Anopheles balabacensis complex representing three geographical regions (Thailand, Peninsular Malaysia and Sabah) in Southeast Asia, were analysed for genetic variation at 15 gene-enzyme systems. The Sabah taxon was monomorphic for all the 15 gene-enzyme systems. Only two gene-enzyme systems (esterase and glucose phosphate isomerase) were variable in the Thailand and Peninsular Malaysia taxa. The average heterozygosity or gene diversity was 0.007 for the Thailand taxon and 0.028 for the Peninsular Malaysia (Perlis) taxon. There were no unique gene-enzyme markers in the three taxa studied. The average values of genetic identities (0.933-0.997) and genetic distances (0.003-0.069) indicate that these three taxa are of subspecific status.
Field studies on the surveillance of Coquillettidia crassipes (Van der Wulp) and the isolation of a strain of Cardiofilaria in peninsular Malaysia

Chiang GL, Samarawickrema WA, Eng KL, Cheong WH, Sulaiman I, Yap HH

Ann Trop Med Parasitol, 1986 Apr;80(2):235-44.
PMID: 2875691

Surveillance methods for Coquillettidia crassipes were studied in an open housing estate near Kuala Lumpur using three types of traps Trinidad 10 trap, modified Lard can trap and IMR trap, each baited with chicken or pigeon. All traps attracted Cq. crassipes. There was no significant difference in the catches in the three traps. There was also no significant difference between chicken and pigeon as bait. Catches at heights of 1.5, 3, 4.5 and 6 m did not show any significant difference in density. Cq. crassipes was active at night with an early peak during the first hour of the night and a minor peak between 0100 and 0200 hours. The activity of the parous and nulliparous sections of the population was similar, except that a higher proportion of the parous females was active during the second peak compared with the nulliparous females. The parous rate was 22.3%, and the probability of survival through one day for two gonotrophic cycles was 0.711 and 0.650. The infection rate for Cardiofilaria was 29 out of 1052 (2.76%) and the infective rate (L3 larvae) was 13 out of 1052 (1.24%). 48.3% of the infected Cq. crassipes had a worm burden of more than ten larvae. One of the chickens in the traps was positive for microfilariae of Cardiofilaria four weeks after exposure as bait. Laboratory bred Cq. crassipes fed on this chicken produced infective larvae in ten days, and these were inoculated into clean chickens and pigeons. Microfilariae appeared in the chickens but not in pigeons. The adult worms recovered await identification.
Filariasis in Bengkoka Peninsula, Sabah, Malaysia: vector studies in relation to the transmission of filariasis

Chiang GL, Cheong WH, Samarawickrema WA, Mak JW, Kan SK

Southeast Asian J. Trop. Med. Public Health, 1984 Jun;15(2):179-89.
PMID: 6150551

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.
Phosphoglucomutase polymorphism in two species of Armigeres mosquitoes

Yong HS, Chan KL, Dhaliwal SS, Cheong WH, Mak JW, Chiang GL

Southeast Asian J. Trop. Med. Public Health, 1980 Sep;11(3):424-5.
PMID: 6108615
Field and laboratory observations on Coquillettidia crassipes in relation to transmission of Brugia malayi in Peninsular Malaysia

Chiang GL, Samarawickrema WA, Mak JW, Cheong WH, Sulaiman I, Yap HH

Ann Trop Med Parasitol, 1986 Feb;80(1):117-21.
PMID: 2873797

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.
Laboratory colonization of Mansonia uniformis, Ma. indiana and Ma. bonneae in Malaysia

Chiang GL, Cheong WH, Loong KP, Eng KL, Samarawickrema WA

J Am Mosq Control Assoc, 1985 Jun;1(2):186-90.
PMID: 2906664

Methods are described for the laboratory colonization of Mansonia uniformis, Ma. indiana and Ma. bonneae in Malaysia. Gravid females oviposited in 500 ml beakers with a layer of water covered with small leaves of Salvinia. Newly hatched larvae were set up in a basal medium of guinea pig dung and water or liver powder, yeast powder and water. Larvae attached to aquatic plants or 'Keaykolour' ruffia snow white paper. The cultures with paper gave better yields than those with plants. Production of Ma. uniformis was higher than the other two species. Twelve generations of Ma. uniformis and 11 generations of Ma. indiana and Ma. bonneae were monitored in the laboratory.
Genetics of glucose phosphate isomerase and phosphoglucomutase in Aedes albopictus (diptera: culicidae)

Yong HS, Chan KL, Dhaliwal SS, Cheong WH, Chiang GL, Mak JW

Theor Appl Genet, 1981 Nov;59(6):345-8.
PMID: 24276567 DOI: 10.1007/BF00276447

Glucose phosphate isomerase (E.C. 5.3.1.9) and phosphoglucomutase (E.C. 2.7.5.1) were found to be polymorphic in a laboratory colony of Aedes albopictus. The glucose phosphate isomerase locus is represented by two alleles resulting in three genotypes, while the phosphoglucomutase locus is represented by at least five alleles giving rise to a total of 15 genotypes. The inheritance of these two enzymes is of the Mendelian type with codominant alleles. Present data indicate that these genes are not linked.Of 105 mosquitoes analysed for these two gene-enzyme systems, the frequencies for glucose phosphate isomerase alleles are Gpi (S)=0.68 and Gpi (F)=0.32, while the frequencies for phosphoglucomutase alleles are Pgm (A)=0.16, Pgm (B)=0.11, Pgm (C)=0.19, Pgm (D)=0.30 and Pgm (F)= 0.24. The frequencies of the three glucose phosphate isomerase genotypes are in accord with Hardy-Weinberg expectations (X 1 (2) =2.74). Similarly, the frequencies of the 15 phosphoglucomutase genotypes probably do not differ significantly from Hardy-Weinberg expectations (X 10 (2) = 18.45).
Genetics of glucosephosphate isomerase in Aedes togoi (Diptera: Culicidae)

Yong HS, Cheong WH, Mak JW, Chiang GL, Chan KL, Dhaliwal SS

Biochem Genet, 1980 Oct;18(9-10):939-45.
PMID: 7225086

The genetics of glucosephosphate isomerase (E.C. 5.3.1.9) in two strains (Malaysian and Taiwan) of Aedes togoi is reported. Three electrophoretic phenotypes were presented in both sexes. The zymogram patterns were identical in both strains of A. togoi. The phenotypes were governed by a pair of codominant alleles. The allele frequency of the slow-moving band was 0.63 in the Malaysian strain adn was 0,86 and 0.82 in F161 and F169 generations, respectively, of the Taiwan strain. The sample studied was in good accord with Hardy-Weinberg expectation.
Fulltext Safety of outpatient commencement of sotalol

Kamsani SH, Middeldorp ME, Chiang G, Stefil M, Evans S, Nguyen MT, et al.

Heart Rhythm O2, 2024 Jun;5(6):341-350.
PMID: 38984365 DOI: 10.1016/j.hroo.2024.05.003

BACKGROUND: Inpatient monitoring is recommended for sotalol initiation.
OBJECTIVE: The purpose of this study was to assess the safety of outpatient sotalol commencement.
METHODS: This is a multicenter, retrospective, observational study of patients initiated on sotalol in an outpatient setting. Serial electrocardiogram monitoring at day 3, day 7, 1 month, and subsequently as clinically indicated was performed. Corrected QT (QTc) interval and clinical events were evaluated.
RESULTS: Between 2008 and 2023, 880 consecutive patients who were commenced on sotalol were evaluated. Indications were atrial fibrillation/flutter in 87.3% (n = 768), ventricular arrhythmias in 9.9% (n = 87), and other arrhythmias in 2.8% (n = 25). The daily dosage at initiation was 131.0 ± 53.2 mg/d. The QTc interval increased from baseline (431 ± 32 ms) to 444 ± 37 ms (day 3) and 440 ± 33 ms (day 7) after sotalol initiation (P < .001). Within the first week, QTc prolongation led to the discontinuation of sotalol in 4 and dose reduction in 1. No ventricular arrhythmia, syncope, or death was observed during the first week. Dose reduction due to asymptomatic bradycardia occurred in 3 and discontinuation due to dyspnea in 3 within the first week. Overall, 1.1% developed QTc prolongation (>500 ms/>25% from baseline); 4 within 3 days, 1 within 1 week, 4 within 60 days, and 1 after >3 years. Discontinuation of sotalol due to other adverse effects occurred in 41 patients within the first month of therapy.
CONCLUSION: Sotalol initiation in an outpatient setting with protocolized follow-up is safe, with no recorded sotalol-related mortality, ventricular arrhythmias, or syncope. There was a low incidence of significant QTc prolongation necessitating discontinuation within the first month of treatment. Importantly, we observed a small incidence of late QT prolongation, highlighting the need for vigilant outpatient surveillance of individuals on sotalol.
The changing pattern of primary glomerulonephritis in Singapore and other countries over the past 3 decades

Woo KT, Chan CM, Mooi CY, -L-Choong H, Tan HK, Foo M, et al.

Clin. Nephrol., 2010 Nov;74(5):372-83.
PMID: 20979946

This review of 2,586 renal biopsies over the past 3 decades in Singapore documents the changing pattern of glomerulonephritis (GN) from that of a third world country to that of a developed nation. In the 1st decade, mesangial proliferative glomerulonephritis was the most common form of primary GN, just as it was in the surrounding Asian countries. In the 2nd decade, the prevalence of mesangial proliferative GN decreased with a rise in membranous, GN which is also seen in China and Thailand. In the 3rd decade, there was a dramatic increase in focal sclerosing glomerulosclerosis. This increase reflects aging and obesity in keeping with more developed countries like Australia, India, Thailand and the United States of America. IgA nephritis remains the most common GN. Apart from the geographical influence, other socioeconomic factors play a significant role in the evolution of the renal biopsy pattern. Mesangial proliferative GN remains prevalent in many Asian countries, but in Singapore the prevalence is decreasing just as it is in Japan, Korea and Malaysia. Worldwide, the prevalence of focal sclerosing glomerulosclerosis continues to increase in many countries.