Displaying publications 1 - 20 of 253 in total

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  1. Dealing with malaria in the last 60 years. A personal experience
    de Zulueta J
    Parassitologia, 2000 Jun;42(1-2):87-90.
    PMID: 11234335
    Dealing with malaria in the last 60 years is seen by the author in the perspective of his own experience. His malaria work, which began in 1941, covered the study of the habits of the mosquitoes dwelling in the savanna country of Eastern Colombia and the effect on malaria transmission of the newly introduced DDT residual spraying. The success of the campaign he later directed in Sarawak and Brunei contributed to the launching by WHO of its global malaria eradication campaign. Further successful work in Uganda showed the possibility of effective control and even eradication in highland country but left unsolved the problem of how to interrupt transmission of holoendemic malaria in Africa. The author's work with WHO in the Middle East showed to what extent social and economic conditions could influence the course of a malaria campaign. This was also the experience in America, both in Colombia in the author's early work and later in Mexico during an evaluation of the national malaria programme. Development of insecticide resistance was also encountered in his career and the refractoriness of the European vectors was also observed in his work as a malariologist.
    Matched MeSH terms: Mosquito Control/history
  2. Mosquito Control Workers in Malaysia: Is Lifetime Occupational Pesticide Exposure Associated With Poorer Neurobehavioral Performance?
    Yusof MZ, Cherrie JW, Samsuddin N, Semple S
    Ann Work Expo Health, 2022 10 11;66(8):1044-1055.
    PMID: 35661855 DOI: 10.1093/annweh/wxac038
    BACKGROUND: Use of pesticides has been linked to neurobehavioral deficits among exposed workers. In Malaysia, organophosphate and pyrethroid pesticides are commonly used to control mosquito-borne diseases.

    OBJECTIVES: This study aims to assess workers' lifetime occupational pesticide exposure and examine the relationship with neurobehavioral health.

    METHODS: A cross-sectional study was conducted on 158 pesticide-exposed and 176 non-exposed workers. To collect historical exposure and job tasks, a questionnaire and an occupational history interview were used. Pesticide exposure was measured in a subgroup of workers via inhalation and skin contact. The total pesticide intake of each worker was assessed using inhalation and dermal exposure models. CANTAB® computerised neurobehavioral performance assessments were used.

    RESULTS: The participants' mean age was 31 (8) years. Pirimiphos-methyl (median = 0.569 mg/m3, Interquartile range [IQR] = 0.151, 0.574) and permethrin (median = 0.136 mg/m3, IQR = 0.116, 0.157) had the highest measured personal inhalation concentrations during thermal spraying. The estimated total lifetime pesticide intake for exposed workers ranged from 0.006 g to 12800 g (median = 379 g and IQR = 131, 794 g). Dermal exposure was the predominant route of pesticide intake for all workers. Compared to controls, workers with high lifetime pesticide intake had lower Match to Sample Visual (adjusted B = -1.4, 95% Confidence Interval (CI) = -2.6, 0.1), Spatial Recognition Memory (adjusted B = -3.3, 95% CI = -5.8, 0.8), Spatial Span (SSP) (adjusted B = -0.6, 95% CI = -0.9, 0.3) scores. Workers with low pesticide intake performed worse than controls (adjusted B = -0.5, 95% CI = -0.8, -0.2) in the SSP test, but scored higher in the Motor Screening test (adjusted B = 0.9, 95% CI = 0.1, 1.6). Higher Paired Associates Learning test scores were observed among higher (adjusted B = 7.4, 95% CI = 2.3, 12.4) and lower (adjusted B = 8.1, 95% CI = 3, 13.2) pesticide intake groups. There was no significant difference between the Reaction Time and Pattern Recognition Memory tests with lifetime pesticide intake after adjusting for confounders.

    CONCLUSION: Pesticide exposure has been linked to poorer neurobehavioral performance. As dermal exposure accounts for a major fraction of total intake, pesticide prevention should focus on limiting dermal exposure.

    Matched MeSH terms: Mosquito Control
  3. Dengue vector control: present status and future prospects
    Yap HH, Chong NL, Foo AE, Lee CY
    Gaoxiong Yi Xue Ke Xue Za Zhi, 1994 Dec;10 Suppl:S102-8.
    PMID: 7844836
    Dengue Fever (DF) and Dengue Haemorrhagic Fever (DHF) have been the most common urban diseases in Southeast Asia since the 1950s. More recently, the diseases have spread to Central and South America and are now considered as worldwide diseases. Both Aedes aegypti and Aedes albopictus are involved in the transmission of DF/DHF in Southeast Asian region. The paper discusses the present status and future prospects of Aedes control with reference to the Malaysian experience. Vector control approaches which include source reduction and environmental management, larviciding with the use of chemicals (synthetic insecticides and insect growth regulators and microbial insecticide), and adulticiding which include personal protection measures (household insecticide products and repellents) for long-term control and space spray (both thermal fogging and ultra low volume sprays) as short-term epidemic measures are discussed. The potential incorporation of IGRs and Bacillus thuringiensis-14 (Bti) as larvicides in addition to insecticides (temephos) is discussed. The advantages of using water-based spray over the oil-based (diesel) spray and the use of spray formulation which provide both larvicidal and adulticidal effects that would consequently have greater impact on the overall vector and disease control in DF/DHF are highlighted.
    Matched MeSH terms: Mosquito Control/trends*
  4. Fulltext Field-simulated residual efficacy of betacyfluthrin against Anopheles sinensis Wiedemann
    Yap HH, Chong NL, Lee CY, Koay CA
    Southeast Asian J. Trop. Med. Public Health, 1997 Mar;28(1):233-4.
    PMID: 9322312
    The residual efficacy of a relatively new pyrethroid, betacyfluthrin was compared with DDT against Anopheles sinensis Wiedemann in some village houses in Penang, Malaysia, for a period of 30 weeks. Efficacy was determined by exposing laboratory-cultured An. sinensis mosquitos to treated wall surfaces with either betacyfluthrin at 15 and 25 mg/m2 or DDT at 2,000 mg/m2 for one hour. Betacyfluthrin provided a longer residual effect (up to 210 days with > 70% mortality) compared with DDT. The potential of betacyfluthrin as a candidate for residual spraying for malaria control is discussed.
    Matched MeSH terms: Mosquito Control*
  5. Field efficacy of mosquito coil formulations containing d-allethrin and d-transallethrin against indoor mosquitos especially Culex quinquefasciatus Say
    Yap HH, Tan HT, Yahaya AM, Baba R, Loh PY, Chong NL
    Southeast Asian J. Trop. Med. Public Health, 1990 Dec;21(4):558-63.
    PMID: 2098916
    Comparative field efficacy studies of four mosquito coil formulations containing active ingredient of d-allethrin (0.19 or 0.28 w/w) and d-transallethrin (0.12 or 0.16% w/w) and blank coils without active ingredient were carried out in living rooms (mean size 54.1 m3) of residential houses in a squatter area in Butterworth, Malaysia. The major indoor biting mosquitos collected in the test site were that of Culex quinquefasciatus Say (84.7%). Mean percentage reduction of blank coils, coils with 0.19 and 0.28% d-allethrin and coils with 0.12 and 0.16% d-transallethrin were 29.0, 71.7, 70.9, 75.0 and 72.6%, respectively. The use of coils as a mean of personal protection against mosquitos is discussed.
    Matched MeSH terms: Mosquito Control/methods*; Mosquito Control/standards
  6. Performance of ULV formulations (Pesguard 102/Vectobac 12AS) against three mosquito species
    Yap HH, Chong AS, Adanan CR, Chong NL, Rohaizat B, Malik YA, et al.
    J Am Mosq Control Assoc, 1997 Dec;13(4):384-8.
    PMID: 9474567
    Adulticidal and larvicidal performances of a water-based pyrethroid microemulsion Pesguard PS 102 (AI d-allethrin and d-phenothrin, both at 5.0% w/w) and Vectobac 12AS, an aqua-suspension Bacillus thuringiensis israelensis (B.t.i.) formulation (AI 1,200 ITU/mg) were assessed against mosquitoes Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus using a Leco ULV Fog Generator Model 1600 and a Scorpion 20 ULV AirBlast Sprayer. Laboratory-cultured mosquito adults and larvae were used for efficacy assessment. For trials using Leco, both pyrethroid and bacterial formulations were dispersed both singly and in combination with Pesguard PS 102 at a dosage of 0.2 liters/ha and B.t.i. at a dosage of 1.0 liter/ha. Similar trials with the Scorpion were also conducted with Pesguard PS 102 at a dosage of 0.2 liters/ha and a higher dosage of B.t.i. (1.5 liters/ha). Experiments were conducted in a football field (200 x 100 m) where five check points at 10, 25, 50, 75, and 100 m downwind from the spray nozzle were chosen for efficacy assessments. Knockdown and mortality were scored at 1 and 24 h postspraying. Results from both trials showed that mortality values varied with distance from spray nozzle. For trials with Leco, fogging with the combination of Pesguard PS 102 and B.t.i. provided larvicidal mortality of > 80% for both Aedes species and of > 60% for Cx. quinquefasciatus larvae at several check points, depending on wind conditions. Complete mortality of adult Aedes mosquitoes at 24 h posttreatment was also achieved, while mortality values for Culex adults reached > 90% under strong wind conditions. As for trials with the Scorpion 20, high adult and larval mortalities were also achieved, with > 90% mortality at some check points. The above study demonstrated the possibility of achieving both larvicidal and adulticidal effects when using a combination of B.t.i. and Pesguard PS 102 in ULV space spray.
    Matched MeSH terms: Mosquito Control/methods*
  7. Indoor thermal fogging application of pesguard FG 161, a mixture of d-tetramethrin and cyphenothrin, using portable sprayer against vector mosquitoes in the tropical environment
    Yap HH, Lee YW, Zairi J, Jahangir K, Adanan CR
    J Am Mosq Control Assoc, 2001 Mar;17(1):28-32.
    PMID: 11345415
    Indoor bioefficacy of the thermal fogging application of Pesguard FG 161, a formulation containing both knockdown and killing agents (active ingredient [AI]: d-tetramethrin 4% [w/w] and cyphenothrin 12% [w/w]) was compared with Resigen5 (AI: s-bioallethrin 0.8% [w/w], permethrin 125/75] 18.7% [w/w], and piperonyl butoxide 16.8% [w/w]), another pyrethroid formulation, as larvicides and adulticides against Aedes aegypti, Aedes albopictus, Anopheles sinensis, and Culex quinquefasciatus using a portable Agrofog AF35 sprayer indoors in houses on Penang Island, Malaysia. Pesguard FG 161 at the concentrations tested was effective against all 4 mosquito species tested. The water-based Pesguard FG 161 performed far better as a larvicide than the diesel-based formulation. Resigen was also effective as a larvicide and adulticide against all 4 mosquito species tested. Larvae of Ae. aegypti were most susceptible to water-based Pesguard FG 161, followed by Cx. quinquefasciatus, An. sinensis, and Ae. albopictus. Even at the lowest concentrations tested, Pesguard FG 161 showed adequate adulticidal properties. At higher dosages, water-based Pesguard FG 161 proved effective as a larvicide against all 4 mosquito species.
    Matched MeSH terms: Mosquito Control/methods*
  8. Evaluation of DursbanR and Dowco 214 as mosquito larvicides in rice-fields
    Yap HH, Ho SC
    Southeast Asian J. Trop. Med. Public Health, 1977 Mar;8(1):63-70.
    PMID: 70078
    Emulsifiable concentrates of DursbanR (chlorpyrifos) and Dowco 214 (chlorpyrifos-methyl) were tested as mosquito larvicides using Hudson knapsack sprayers on small plots of rice-fields on Penang Island. The mosquitoes found in these rice-fields are predominantly Anopheles campestris and Culex tritaeniorhynchus. At dosages of 14, 28 and 56 gm hectare-1, Dursban is effective in maintaining the rice-fields free of Anopheles larvae for at least 2, 3 and 7 days respectively. Dowco 214 at 56 gm hectare-1 is able to keep the fields free of all mosquito larvae for at least 2 days.
    Matched MeSH terms: Mosquito Control*
  9. Differences in Perceived Severity of Zika Virus Infection and Dengue Fever and its Influence on Mosquito Control Practices in Malaysia
    Wong LP, Alias H, Aghamohammadi N, Sam IC, AbuBakar S
    J Community Health, 2017 Oct;42(5):854-864.
    PMID: 28238029 DOI: 10.1007/s10900-017-0326-7
    The aims of this study were to explore the differences in (1) the perception of severity towards ZIKV infection and dengue fever, and (2) mosquito control practices before and after the ZIKV outbreak were declared a Public Health Emergency of International Concern (PHEIC). Data were collected between Feb to May 2016 using a computer-assisted telephone interviewing system. The median scale score for perceived severity of ZIKV was 3 (interquartile range [IQR] 1-5) versus 4 (IQR 3-5) for dengue (P mosquito control practices before and after ZIKV was declared a PHEIC were similar, at 4 (IQR 3-5). Multivariate analysis revealed that participants with a higher score for perception of severity of ZIKV were more likely to report greater mosquito control practices after the declaration of the PHEIC (OR 1.822 [95% CI 1.107-2.998]). The emerging ZIKV pandemic requires concerted efforts to enhance mosquito control practices among the Malaysian public. Efforts to improve public mosquito control practices should focus on enhancing the perception of the severity of ZIKV.
    Matched MeSH terms: Mosquito Control/statistics & numerical data*
  10. Fulltext Dispersal of Engineered Male Aedes aegypti Mosquitoes
    Winskill P, Carvalho DO, Capurro ML, Alphey L, Donnelly CA, McKemey AR
    PLoS Negl Trop Dis, 2015 Nov;9(11):e0004156.
    PMID: 26554922 DOI: 10.1371/journal.pntd.0004156
    BACKGROUND: Aedes aegypti, the principal vector of dengue fever, have been genetically engineered for use in a sterile insect control programme. To improve our understanding of the dispersal ecology of mosquitoes and to inform appropriate release strategies of 'genetically sterile' male Aedes aegypti detailed knowledge of the dispersal ability of the released insects is needed.

    METHODOLOGY/PRINCIPAL FINDINGS: The dispersal ability of released 'genetically sterile' male Aedes aegypti at a field site in Brazil has been estimated. Dispersal kernels embedded within a generalized linear model framework were used to analyse data collected from three large scale mark release recapture studies. The methodology has been applied to previously published dispersal data to compare the dispersal ability of 'genetically sterile' male Aedes aegypti in contrasting environments. We parameterised dispersal kernels and estimated the mean distance travelled for insects in Brazil: 52.8 m (95% CI: 49.9 m, 56.8 m) and Malaysia: 58.0 m (95% CI: 51.1 m, 71.0 m).

    CONCLUSIONS/SIGNIFICANCE: Our results provide specific, detailed estimates of the dispersal characteristics of released 'genetically sterile' male Aedes aegypti in the field. The comparative analysis indicates that despite differing environments and recapture rates, key features of the insects' dispersal kernels are conserved across the two studies. The results can be used to inform both risk assessments and release programmes using 'genetically sterile' male Aedes aegypti.

    Matched MeSH terms: Mosquito Control/methods
  11. Anti-larval sluicing
    Williamson KB, Scharff JW
    Malayan Medical Journal, 1936;11:124-50.
    Matched MeSH terms: Mosquito Control
  12. The nitrogenous and total organic content of the soil in relation to malaria
    Williamson KB
    Malayan Medical Journal, 1928;3:148-64.
    Matched MeSH terms: Mosquito Control
  13. Malaria and population explosion
    Williams CD
    Lancet, 1968 Oct 19;2(7573):868-9.
    PMID: 4175755
    Matched MeSH terms: Mosquito Control
  14. Recent developments in insecticides of medical importance
    Wharton RH
    Med J Malaya, 1950;5.
    The prospects in Malaya in the immediate future may be briefly summarized as follows : For residual sprays, DDT and gamma BHC, unless some outstanding new compound appears, will continue to be the most widely used. Both kill the principal malaria carrier. Anopheles maculatus and gamma BHC for a short period after application also kills the common nuisance mosquito, Culex fatigans. Though DDT does not kill C fatigans it prevents them from resting in rooms and reduces the number of biting. Both insecticides should eliminate bed bugs Cimex hemipterus during the course of spraying and reduce cockroach infestation. For the elimination of cockroaches and ants from houses gamma BHC is superior to DDT but the effect is short lived. The other residual insecticides, Chlordane, Toxaphene, Methoxychlor and the newer products Aldrin and Dieldrin are not likely to be used extensively in Malaya. They cannot yet be purchased locally and on present indications have no outstanding advantages to recommend them instead of DDT or BHC. Personal protection against scrub typhus infection is now satisfactory. Either DBP or benzyl benzoate rubbed into clothing should prevent the attachment of mites for several days, and DMP is also effective if applied daily to the skin or clothing. The mite population in an infective area can probably be reduced effectively by spraying BHC on the vegetation, but this method of control is not likely to be attempted in many areas. DMP is a good mosquito repellent and forms the main ingredient of several commercial preparations; it is not as effective when incorpora ted in a cream as it is when pure. Of the several simple, efficient remedies now available for head louse and scabies control, gamma BHC in coconut oil is probably the most useful because of its cheapness, ease of application, and effect on both parasites.
    Matched MeSH terms: Mosquito Control
  15. The ways and means adopted by government for the control of malaria in the Federated Malay States
    Wellington AR
    Malayan Medical Journal, 1926;1:16-20.
    Matched MeSH terms: Mosquito Control
  16. Gunong Pulai. Anti-malarial measures
    Watson M
    Malayan Medical Journal, 1926;1:38-42.
    Matched MeSH terms: Mosquito Control
  17. The effect of drainage and other measures on the malaria of Klang, Federated Malay States
    Watson M
    J Trop Med, 1903;6:349-53, 368-71.
    Matched MeSH terms: Mosquito Control
  18. Twenty-five years of malaria control
    Watson M
    Malayan Medical Journal, 1928;3:7-10.
    Matched MeSH terms: Mosquito Control
  19. Fulltext Surveillance of Aedes mosquitoes in a university campus in Kuala Lumpur, Malaysia
    Wan Norafikah O, Chen CD, Soh HN, Lee HL, Nazni WA, Sofian-Azirun M
    Trop Biomed, 2009 Aug;26(2):206-15.
    PMID: 19901907 MyJurnal
    Ovitrap surveillance was initiated for eight continuous weeks to determine the distribution and abundance of Aedes sp. mosquitoes in the University of Malaya campus, Kuala Lumpur, and the impact of meteorological conditions on the Aedes populations. Two study areas within the campus were selected: Varsity Lake and Seventh Residential College. The abundance of Aedes populations in Varsity Lake was indicated by ovitrap index (OI) which ranged from 60.00%-90.00%. The mean number of larvae per ovitrap of Aedes albopictus in Varsity Lake ranged from 11.23+/-2.42-43.80+/-6.22. On the other hand, the outdoor OI for Seventh Residential College ranged from 73.33%-93.33%, respectively, while the mean number larvae per ovitrap for this area ranged from 19.33+/-4.55-35.27+/-5.46, respectively. In addition, the indoor OI of Seventh Residential College ranged from 0.00%-30.00%, while the mean number of larvae per ovitrap for Ae. albopictus ranged from 0-5.90+/-3.55. There was no significant difference (p>0.05) of Ae. albopictus population between Varsity Lake and Seventh Residential College. The studies showed a correlation between OI and mean number of larvae per ovitrap for outdoor Ae. albopictus populations in Varsity Lake and Seventh Residential College (r=0.794). There was also a correlation between the mean larvae number per ovitrap of Ae. albopictus obtained from eight weeks indoor ovitrap surveillance in Seventh Residential College with rainfall (r=0.584). However, there was no correlation between the mean larvae number per ovitrap of Ae. albopictus in both study areas with temperature and relative humidity. Aedes aegypti mosquitoes were found neither indoor nor outdoor in both study areas. This study indicated that the principal dengue vector in the university campus was most likely Ae. albopictus.
    Matched MeSH terms: Mosquito Control
  20. Cessation of oiling in a malarious area during a certain season of the year [duplicate1]
    Wallace RB
    Malayan Medical Journal, 1930;5:117-25.
    Matched MeSH terms: Mosquito Control
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