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Fulltext Studies on adult mosquito vectors of Japanese encephalitis in a pig farm in Selangor, Malaysia

Vythilingam I, Mahadevan S, Zaridah MZ, Ong KK, Abdullah G, Ong YF

Southeast Asian J. Trop. Med. Public Health, 1994 Jun;25(2):383-6.
PMID: 7855662

Mosquito collections were carried out for a period of one year from January to December 1992 in a pig farm in Sungai Pelek, Selangor, Malaysia. A total of 41,022 mosquitos belonging to 52 species and 20 genera were collected. Culex tritaeniorhynchus and Cx. gelidus, the important vectors, comprised 63% of all mosquitos collected. Both these species were collected in large numbers during the wet months of May and December. The other predominant species in that area were Cx. fuscocephala, Cx. quinquefasciatus, Cx. sitiens, Aedes butleri, and Armigeres subalbatus.

Matched MeSH terms: Population Density
Fulltext Anopheline mosquitos of northwest coastal Malaysia

Jaal Z, MacDonald WW

Southeast Asian J. Trop. Med. Public Health, 1992 Sep;23(3):479-85.
PMID: 1488703

Collections of adult anopheline mosquitos were made from a cow-baited trap in nine coastal villages located along nearly 160km of northwest peninsular Malaysia. Two collections, separated by 1.5 to 6 months, were made at each site. Nearly 6,000 anophelines of 19 species were collected. The dominant species were Anopheles peditaeniatus. An. sinensis, An. subpictus and An. lesteri paraliae. Small numbers of the malaria vectors An. maculatus (at one site) and An. campestris (at four sites) were collected, but no An. sundaicus were recorded.

Matched MeSH terms: Population Density
Chigger (Acarina:Trombiculidae) surveys of the west coast beaches of Sabah and Sarawak

Dohany AL, Phang OW, Rapmund G

Southeast Asian J. Trop. Med. Public Health, 1977 Jun;8(2):200-6.
PMID: 411176

Leptotrombidium (Leptotrombidium) arenicola Traub, a vector of scrub typhus, had previously been found to occur in the coastal vegetation behind the edge of open sand along the beaches of Peninsular Malaysia. Surveys of the west coast beaches of Sabah and Sarawak were conducted to determine if this species occurs in similar habitat in East Malaysia on the island of Borneo. Leptotrombidium (L.) arenicola was not collected from the eighteen sites studied. Of the 11,982 mite larvae collected, 55 per cent were L.(L.) deliense (Walch), a well-known, widespread vector of scrub typhus.

Matched MeSH terms: Population Density
Numbers of Leptotrombidium (Leptotrombidium) deliense (Acarina: trombiculidae) and prevalence of Rickettsia tsutsugamushi in adjacent habitats of peninsular Malaysia

Roberts LW, Muul I, Robinson DM

Southeast Asian J. Trop. Med. Public Health, 1977 Jun;8(2):207-13.
PMID: 411177

Numbers of L. (L.) deliense larvae were determined in adjacent habitats over a 16 month period. Both R. argentiventer and R. tiomanicus were highly efficient hosts for L. (L.) deliense. R. argentiventer was host to significantly greater numbers of chiggers per rat than was R. tiomanicus. The 2 habitats were similar in numbers of chiggers collected. No consistent correlation was apparent between numbers of chiggers and any single weather factor, but the chigger population seemed to be adversely affected by a 2 month period during which total evaporation greatly exceeded total rainfall. Direct fluorescent antibody examination of tissues from unfed L. (L.) deliense showed that 2 of 420 larvae (0.5%) contained organisms morphologically resembling R. tsutsugamushi. Considering the vector load and numbers of chiggers being returned to the ground by a given host, a rate of 0.5% appeared adequate to account for the prevalence rate of R. tsutsugamushi observed in the 2 host species.

Matched MeSH terms: Population Density
The inheritance of autogeny in Aedes (Finlaya) togoi (Theobald) from Malaysia and some aspects of its biology

Thomas V, Leng YP

Southeast Asian J. Trop. Med. Public Health, 1972 Jun;3(2):163-74.
PMID: 5082846
Matched MeSH terms: Population Density
The effects of rainfall on trombiculid (Acarina:trombiculidae) larval populations in peninsular Malaysia

Gentry JW, Phang OW, Manikumaran C

Southeast Asian J. Trop. Med. Public Health, 1977 Jun;8(2):217-20.
PMID: 918713

Studies of larval mite populations along transects, as measured with black plates, were conducted in forest and grassland habitats for a period of 67 weeks. Larvae of both Leptotrombidium (Leptotrombidium) deliense and L. (L.) fletcheri were influenced greatly by rainfall, with the larvae being abundant and easily collected during periods of heavy rainfall and difficult or impossible to collect during dry periods. Simulated rainfall maintained larval populations for longer periods during dry weather.

Matched MeSH terms: Population Density
The persistence of naturally formed mit (Acarina: trombiculidae) foci in Malaysia

Gentry JW, Phang OW, Manikumaran C

Southeast Asian J. Trop. Med. Public Health, 1977 Jun;8(2):214-6.
PMID: 918712

Mite foci were fenced above and below ground to prevent the entry of host animals and to prevent the migration of mites within the soil. Weekly counts were made over a period of thirty weeks with larvae being collected at the beginning and end of the study, but not during the intervening period of hot, dry weather. Post-larval forms can survive for long periods and mite foci can remain productive without being visited by the host animals. Mite foci may be missed by normal survey methods during hot, dry weather.

Matched MeSH terms: Population Density
Seasonal and long term variations of surface ozone concentrations in Malaysian Borneo

Latif MT, Dominick D, Ahamad F, Ahamad NS, Khan MF, Juneng L, et al.

Sci Total Environ, 2016 Dec 15;573:494-504.
PMID: 27572541 DOI: 10.1016/j.scitotenv.2016.08.121

Malaysian Borneo has a lower population density and is an area known for its lush rainforests. However, changes in pollutant profiles are expected due to increasing urbanisation and commercial-industrial activities. This study aims to determine the variation of surface O3concentration recorded at seven selected stations in Malaysian Borneo. Hourly surface O3data covering the period 2002 to 2013, obtained from the Malaysian Department of Environment (DOE), were analysed using statistical methods. The results show that the concentrations of O3recorded in Malaysian Borneo during the study period were below the maximum Malaysian Air Quality Standard of 100ppbv. The hourly average and maximum O3concentrations of 31 and 92ppbv reported at Bintulu (S3) respectively were the highest among the O3concentrations recorded at the sampling stations. Further investigation on O3precursors show that sampling sites located near to local petrochemical industrial activities, such as Bintulu (S3) and Miri (S4), have higher NO2/NO ratios (between 3.21 and 5.67) compared to other stations. The normalised O3values recorded at all stations were higher during the weekend compared to weekdays (unlike its precursors) which suggests the influence of O3titration by NO during weekdays. The results also show that there are distinct seasonal variations in O3across Borneo. High surface O3concentrations were usually observed between August and September at all stations with the exception of station S7 on the east coast. Majority of the stations (except S1 and S6) have recorded increasing averaged maximum concentrations of surface O3over the analysed years. Increasing trends of NO2and decreasing trends of NO influence the yearly averaged maximum of O3especially at S3. This study also shows that variations of meteorological factors such as wind speed and direction, humidity and temperature influence the concentration of surface O3.

Matched MeSH terms: Population Density
Microplastics in the freshwater and terrestrial environments: Prevalence, fates, impacts and sustainable solutions

Wong JKH, Lee KK, Tang KHD, Yap PS

Sci Total Environ, 2020 Jun 01;719:137512.
PMID: 32229011 DOI: 10.1016/j.scitotenv.2020.137512

The ubiquitous occurrences of microplastics in the environment have raised much concern and resulted in voluminous studies related to microplastics. Studies on microplastics pollution of the marine environment have received significantly higher attention compared to those of the freshwater and terrestrial environments. With the impetus to better understand microplastics in the freshwater and terrestrial environments, this review elucidates the findings of >100 articles related to the prevalence, fates and impacts of microplastics therein and the sustainable solutions, mostly in the past 10 years. This review shows the interconnection between terrestrial and freshwater microplastics with wastewater and sewage treatment plants as the most significant contributors of environmental microplastics via sludge and effluent discharges. Microplastics in both ecosystems comprise the primary and secondary forms with the latter resulted from weathering of the former. Besides retaining in soil and infiltrating with rainwater underground, terrestrial microplastics also enter the freshwater environment. The environmental microplastics interact with the biotic and abiotic components resulting in entrainment, settlement, biofouling, degradation, fragmentation and entry into the food chain, with subsequent transfer across the food chain. The abundance of environmental microplastics is attributed to population density and urbanization though tidal cycle, storms, floods and human activities can affect their distribution. The leaching of additives from microplastics poses major health concern and sustainable solutions target at reduction of plastics use and disposal, substitution with bioplastics and wastewater treatment innovations. Further studies on classification, detection, characterization and toxicity of microplastics are necessary to permit more effective formulation of solutions.

Matched MeSH terms: Population Density
Fulltext Population 70 million: a consideration of health aspects

Zulkifli SN, Yusof K

Med J Malaysia, 1985 Jun;40(2):62-79.
PMID: 3834289

A 70 million population for Malaysia by the year 2010 has been officially targetted for in the Mid-Term Review of the Fourth Malaysia Plan, 1981-1985. In response to this, a preliminary investigation was undertaken into the health aspects of population growth. For this exercise, infant mortality rate was used as the health indicator. From trends seen vis-a-vis population growth, it appears that thus far, population growth has not been associated negatively with health (as measured by IMR). In recognition of the relevance of the medical, economic and education factors to health, trends in Malaysia's population ratio, per capita GNP and rates of school enrolment were also drawn; the selection of these as proxies being based on completeness of time-serial records. Although statistical regressions established the high correlation between medical doctors.population ratio and school enrolment rate with IMR, the limitations in this analysis did not permit any reliable inferences. In view of the difficulties in projections of trends, a comparison of health and related variables was carried out for several countries with high populations as near to 70 million as were available. The characteristics associated with low mortality and high life expectancy (health indices) were identified as low population growth, high literacy and high per capita GNP; this being stated with explicit qualifications. Other determinants of health were also discussed in brief, and the need for careful planning in the distribution of human and material resources was noted.

Matched MeSH terms: Population Density*
Fulltext Distribution and density of Aedes aegypti (L) and Aedes albopictus (Skuse) in Sarawak

Chang MS, Jute N

Med J Malaysia, 1982 Sep;37(3):205-10.
PMID: 7176997

A total of 73 localities covering 4,894 premises and 26, 712 breeding habitats were surveyed in 1980 to determine and establish the density and distribution pattern of Aedes aegypti and Aedes albopictus in Sarawak. A similar pattern has been observed in the density of the Aedes aegypti and Aedes albopictus. The number of houses positive with Aedes larvae were found to be highest in the coastal areas followed by the inland rural areas. The Aedes aegypti Breteau Index (B.I.) of 0-525 in the coastal areas is the highest followed by 0-207.5 in the inland rural areas. The study undertaken has now revealed that both the Aedes aegypti and Aedes albopictus are widespread in the State.

Matched MeSH terms: Population Density
Fragmented population structure of plasmodium falciparum in a region of declining endemicity

Anthony TG, Conway DJ, Cox-Singh J, Matusop A, Ratnam S, Shamsul S, et al.

J Infect Dis, 2005 May 1;191(9):1558-64.
PMID: 15809916

The population genetic structure of Plasmodium falciparum differs between endemic regions, but the characteristics of a population recently fragmented by effective malaria control have been unknown.

Matched MeSH terms: Population Density
Genetic Structure and Diversity Among Historic and Modern Populations of the Sumatran Rhinoceros (Dicerorhinus sumatrensis)

Brandt JR, van Coeverden de Groot PJ, Witt KE, Engelbrektsson PK, Helgen KM, Malhi RS, et al.

J Hered, 2018 06 27;109(5):553-565.
PMID: 29684146 DOI: 10.1093/jhered/esy019

The Sumatran rhinoceros (Dicerorhinus sumatrensis), once widespread across Southeast Asia, now consists of as few as 30 individuals within Sumatra and Borneo. To aid in conservation planning, we sequenced 218 bp of control region mitochondrial (mt) DNA, identifying 17 distinct mitochondrial haplotypes across modern (N = 13) and museum (N = 26) samples. Museum specimens from Laos and Myanmar had divergent mtDNA, consistent with the placement of western mainland rhinos into the distinct subspecies D. s. lasiotis (presumed extinct). Haplotypes from Bornean rhinos were highly diverse, but dissimilar from those of other regions, supporting the distinctiveness of the subspecies D. s. harrissoni. Rhinos from Sumatra and Peninsular Malaysia shared mtDNA haplotypes, consistent with their traditional placement into a single subspecies D. s sumatrensis. Modern samples of D. s. sumatrensis were genotyped at 18 microsatellite loci. Rhinos within Sumatra formed 2 sub-populations, likely separated by the Barisan Mountains, though with only modest genetic differentiation between them. There are so few remaining Sumatran rhinoceros that separate management strategies for subspecies or subpopulations may not be viable, while each surviving rhino pedigree is likely to retain alleles found in no other individuals. Given the low population size and low reproductive potential of Sumatran rhinos, rapid genetic erosion is inevitable, though an under-appreciated concern is the potential for fixation of harmful genetic variants. Both concerns underscore 2 overriding priorities for the species: 1) translocation of wild rhinos to ex situ facilities, and 2) collection and storage of gametes and cell lines from every surviving captive and wild individual.

Matched MeSH terms: Population Density
The future of protected areas in a crowded world

Harmon D, Brechin SR

George Wright Forum, 1994;11(3):97-116.
PMID: 12290870
Matched MeSH terms: Population Density*
Population Density and Risk of Inflammatory Bowel Disease: A Prospective Population-Based Study in 13 Countries or Regions in Asia-Pacific

Ng SC, Kaplan GG, Tang W, Banerjee R, Adigopula B, Underwood FE, et al.

Am J Gastroenterol, 2019 01;114(1):107-115.
PMID: 30177785 DOI: 10.1038/s41395-018-0233-2

INTRODUCTION: Living in an urban environment may increase the risk of developing inflammatory bowel disease (IBD). It is unclear if this observation is seen globally. We conducted a population-based study to assess the relationship between urbanization and incidence of IBD in the Asia-Pacific region.
METHODS: Newly diagnosed IBD cases between 2011 and 2013 from 13 countries or regions in Asia-Pacific were included. Incidence was calculated with 95% confidence interval (CI) and pooled using random-effects model. Meta-regression analysis was used to assess incidence rates and their association with population density, latitude, and longitude.
RESULTS: We identified 1175 ulcerative colitis (UC), 656 Crohn's disease (CD), and 37 IBD undetermined (IBD-U). Mean annual IBD incidence per 100 000 was 1.50 (95% CI: 1.43-1.57). India (9.31; 95% CI: 8.38-10.31) and China (3.64; 95% CI, 2.97-4.42) had the highest IBD incidence in Asia. Incidence of overall IBD (incidence rate ratio [IRR]: 2.19; 95% CI: 1.01-4.76]) and CD (IRR: 3.28; 95% CI: 1.83-9.12) was higher across 19 areas of Asia with a higher population density. In China, incidence of IBD (IRR: 2.37; 95% CI: 1.10-5.16) and UC (IRR: 2.63; 95% CI: 1.2-5.8) was positively associated with gross domestic product. A south-to-north disease gradient (IRR: 0.94; 95% CI: 0.91-0.98) was observed for IBD incidence and a west-to-east gradient (IRR: 1.14; 95% CI: 1.05-1.24) was observed for CD incidence in China. This study received IRB approval.
CONCLUSIONS: Regions in Asia with a high population density had a higher CD and UC incidence. Coastal areas within China had higher IBD incidence. With increasing urbanization and a shift from rural areas to cities, disease incidence may continue to climb in Asia.

Matched MeSH terms: Population Density
Estimating the Population Size of People Who Inject Drugs in Malaysia for 2014 and 2017 Using the Benchmark-Multiplier Method

Hiebert L, Azzeri A, Dahlui M, Hecht R, Mohamed R, Hana Shabaruddin F, et al.

Subst Use Misuse, 2020;55(6):871-877.
PMID: 31933411 DOI: 10.1080/10826084.2019.1708943

Background: As hepatitis C elimination efforts are launched, national strategies for screening and treatment scale-up in countries, such as Malaysia, must be designed and implemented. Strategic information, including estimates of the total number of patients chronically-infected with hepatitis C virus (HCV) and the size of key populations, such as people who inject drugs (PWID), is critical to informing these efforts. For Malaysia, the estimate of the PWID population size most frequently reported in global systematic reviews is for the year 2009. Objectives: To support ongoing national HCV planning efforts, we aimed to estimate the national population size of active PWID in Malaysia, for the years 2014 and 2017. Methods: To estimate the PWID population size, we applied standard benchmark-multiplier methodology, frequently used for PWID population size estimation, and extended it by adjusting for cessation of injecting drug use within the benchmark and calculating statistical uncertainty intervals. Results: The estimated active PWID population size was 153,000 (95% uncertainty interval (UI): 136,000-172,000) for 2014 and 156,000 (95% UI: 137,000-188,000) for 2017. Conclusions/importance: This updated estimate of the active PWID population size in Malaysia will help inform effective planning for the scale-up of HCV screening and treatment services. The proposed methodology is applicable to other countries that maintain national HIV registries and have conducted Integrated Biological and Behavioral Surveys among active PWID.

Matched MeSH terms: Population Density
Fulltext Assessment of land use factors associated with dengue cases in Malaysia using Boosted Regression Trees

Cheong YL, Leitão PJ, Lakes T

Spat Spatiotemporal Epidemiol, 2014 Jul;10:75-84.
PMID: 25113593 DOI: 10.1016/j.sste.2014.05.002

The transmission of dengue disease is influenced by complex interactions among vector, host and virus. Land use such as water bodies or certain agricultural practices have been identified as likely risk factors for dengue because of the provision of suitable habitats for the vector. Many studies have focused on the land use factors of dengue vector abundance in small areas but have not yet studied the relationship between land use factors and dengue cases for large regions. This study aims to clarify if land use factors other than human settlements, e.g. different types of agricultural land use, water bodies and forest are associated with reported dengue cases from 2008 to 2010 in the state of Selangor, Malaysia. From the correlative relationship, we aim to generate a prediction risk map. We used Boosted Regression Trees (BRT) to account for nonlinearities and interactions between the factors with high predictive accuracies. Our model with a cross-validated performance score (Area Under the Receiver Operator Characteristic Curve, ROC AUC) of 0.81 showed that the most important land use factors are human settlements (model importance of 39.2%), followed by water bodies (16.1%), mixed horticulture (8.7%), open land (7.5%) and neglected grassland (6.7%). A risk map after 100 model runs with a cross-validated ROC AUC mean of 0.81 (±0.001 s.d.) is presented. Our findings may be an important asset for improving surveillance and control interventions for dengue.

Matched MeSH terms: Population Density
Fulltext Counting in the dark: non-intrusive laser scanning for population counting and identifying roosting bats

Azmy SN, Sah SA, Shafie NJ, Ariffin A, Majid Z, Ismail MN, et al.

Sci Rep, 2012;2:524.
PMID: 22826802 DOI: 10.1038/srep00524

Population surveys and species recognition for roosting bats are either based on capture, sight or optical-mechanical count methods. However, these methods are intrusive, are tedious and, at best, provide only statistical estimations. Here, we demonstrated the successful use of a terrestrial Light Detection and Ranging (LIDAR) laser scanner for remotely identifying and determining the exact population of roosting bats in caves. LIDAR accurately captured the 3D features of the roosting bats and their spatial distribution patterns in minimal light. The high-resolution model of the cave enabled an exact count of the visibly differentiated Hipposideros larvatus and their roosting pattern within the 3D topology of the cave. We anticipate that the development of LIDAR will open up new research possibilities by allowing researchers to study roosting behaviour within the topographical context of a cave's internal surface, thus facilitating rigorous quantitative characterisations of cave roosting behaviour.

Matched MeSH terms: Population Density
Fulltext Genetic diversity of Nile tilapia (Oreochromis niloticus) throughout West Africa

Lind CE, Agyakwah SK, Attipoe FY, Nugent C, Crooijmans RPMA, Toguyeni A

Sci Rep, 2019 11 14;9(1):16767.
PMID: 31727970 DOI: 10.1038/s41598-019-53295-y

Nile tilapia (Oreochromis niloticus) is a globally significant aquaculture species rapidly gaining status as a farmed commodity. In West Africa, wild Nile tilapia genetic resources are abundant yet knowledge of fine-scale population structure and patterns of natural genetic variation are limited. Coinciding with this is a burgeoning growth in tilapia aquaculture in Ghana and other countries within the region underpinned by locally available genetic resources. Using 192 single nucleotide polymorphism (SNP) markers this study conducted a genetic survey of Nile tilapia throughout West Africa, sampling 23 wild populations across eight countries (Benin, Burkina Faso, Côte d'Ivoire, Ghana, Togo, Mali, Gambia and Senegal), representing the major catchments of the Volta, Niger, Senegal and Gambia River basins. A pattern of isolation-by-distance and significant spatial genetic structure was identified throughout West Africa (Global FST = 0.144), which largely corresponds to major river basins and, to a lesser extent, sub-basins. Two populations from the Gambia River (Kudang and Walekounda), one from the western Niger River (Lake Sélingué) and one from the upper Red Volta River (Kongoussi) showed markedly lower levels of diversity and high genetic differentiation compared to all other populations, suggesting genetically isolated populations occurring across the region. Genetic structure within the Volta Basin did not always follow the pattern expected for sub-river basins. This study identifies clear genetic structuring and differentiation amongst West African Nile tilapia populations, which concur with broad patterns found in previous studies. In addition, we provide new evidence for fine-scale genetic structuring within the Volta Basin and previously unidentified genetic differences of populations in Gambia. The 192 SNP marker suite used in this study is a useful tool for differentiating tilapia populations and we recommend incorporating this marker suite into future population screening of O. niloticus. Our results form the basis of a solid platform for future research on wild tilapia genetic resources in West Africa, and the identification of potentially valuable germplasm for use in ongoing breeding programs for aquaculture.

Matched MeSH terms: Population Density
Fulltext Population estimates of Bornean orang-utans using Bayesian analysis at the greater Batang Ai-Lanjak-Entimau landscape in Sarawak, Malaysia

Pandong J, Gumal M, Alen L, Sidu A, Ng S, Koh LP

Sci Rep, 2018 10 23;8(1):15672.
PMID: 30353034 DOI: 10.1038/s41598-018-33872-3

The integration of Bayesian analysis into existing great ape survey methods could be used to generate precise and reliable population estimates of Bornean orang-utans. We used the Marked Nest Count (MNC) method to count new orang-utan nests at seven previously undocumented study sites in Sarawak, Malaysia. Our survey teams marked new nests on the first survey and revisited the plots on two more occasions; after about 21 and 42 days respectively. We used the N-mixture models to integrate suitability, abundance and detection models which account for zero inflation and imperfect detection for the analysis. The result was a combined estimate of 355 orang-utans with the 95% highest density interval (HDI) of 135 to 602 individuals. We visually inspected the posterior distributions of our parameters and compared precisions between study sites. We subsequently assess the strength or reliability of the generated estimates using identifiability tests. Only three out of the seven estimates had <35% overlap to indicate strong reliability. We discussed the limitations and advantages of our study design, and made recommendations to improve the sampling scheme. Over the course of this research, two of the study sites were gazetted as extensions to the Lanjak-Entimau Wildlife Sanctuary for orang-utan conservation.

Matched MeSH terms: Population Density

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