Developing time-based model for the prediction of breeding activities of dengue vectors using early life cycle variables and epidemiological information in Northern Malaysia.

Autoregressive integrated moving average (ARIMA) was applied to make realtime predictions on the Aedes egg populations in three selected dengue hotspots of Penang, Malaysia. The weekly ovitrap collection was carried out to determine the abundance of Aedes eggs in field population in some selected areas. The ARIMA models were able to estimate actual egg abundance using two criteria. The first criteria is determine the reliability of statistics and the second is to measure the accuracy of forecasting ability of the model equation. The parsimonious model with a lowest order of AR or MA and RMSE value of the forecast for each data set was considered the best. ARIMA (1,0,0), ARIMA (2,0,0) and ARIMA (0,1,1) models were judged to be the best fit for the suburban, urban squatter and urban area data sets respectively. The models were able to forecast the number of eggs within a range of one to eleven weeks. The developed models were able to estimate the egg abundance adequately to permit their use in Aedes control programme in Penang Island. Thus, it can be a useful tool for health officials to improve the management of mosquito control and alert the public to reduce the possibility of dengue outbreaks.

Developing time-based model for the prediction of breeding activities of dengue vectors using early life cycle variables and epidemiological information in Northern Malaysia

Autoregressive integrated moving average (ARIMA) was applied to make realtime predictions on the Aedes egg populations in three selected dengue hotspots of Penang, Malaysia. The weekly ovitrap collection was carried out to determine the abundance of Aedes eggs in field population in some selected areas. The ARIMA models were able to estimate actual egg abundance using two criteria. The first criteria is determine the reliability of statistics and the second is to measure the accuracy of forecasting ability of the model equation. The parsimonious model with a lowest order of AR or MA and RMSE value of the forecast for each data set was considered the best. ARIMA (1,0,0), ARIMA (2,0,0) and ARIMA (0,1,1) models were judged to be the best fit for the suburban, urban squatter and urban area data sets respectively. The models were able to forecast the number of eggs within a range of one to eleven weeks. The developed models were able to estimate the egg abundance adequately to permit their use in Aedes control programme in Penang Island. Thus, it can be a useful tool for health officials to improve the management of mosquito control and alert the public to reduce the possibility of dengue outbreaks.

Larval Distributions and breeding habitats of Aedes aegypti and Ae. albopictus in Kuala Terengganu.

Aedes aegypti and Ae. albopictus play an important role in spreading dengue and chikungunya virus in Malaysia. Currently dengue fever is still the most important threat to this country. The number of dengue cases are on the rise in some states despite the efforts made by the government to keep the surroundings of houses clean and free from Aedes breeding sites. This study was carried out to determine the breeding sites of Aedes in Kuala Terengganu. Samplings were carried out between August 2009 until February 2010 at six study sites from both the urban and rural areas. Samples collected were counted and the distribution classes (class 1 (C1) to class 5 (C5)) were determined. Water tank, glass container and used paint bucket were found to be the most preferable breeding sites in the study areas. Many Ae. aegypti larvae were collected in the urban areas and the highest number of Ae. albopictus larvae were collected from the rural areas. As for the larval distributions, Ae. aegypti recorded a frequent distribution (C4: 60.1-80%) in urban areas while Ae. albopictus recorded infrequent distribution (C2: 20.1-40%). Frequent distributions of Aedes larvae were recorded when relative humidity is high. Apart from environmental factors, human density also could affect the distributions of Aedes larvae in the urban area.

Population analysis of Aedes albopictus (Skuse) (Diptera:Culicidae) under uncontrolled laboratory conditions.

A semi laboratory experiment using 3 cohorts of Aedes albopictus adults was performed to obtain age-specific mortality and fecundity information and to derive statistical estimates of some population growth parameters. Life expectancy was calculated for both males and females. The following population parameters were estimated: intrinsic rate of increase (rm= 0.21), net reproductive (replacement) rate (Ro= 68.70), age at mean cohort reproduction (To=10.55 days), birth rate (B=0.23), death rate (D=0.02) and generation time (G=20.14 days). The high rm/B (0.91) and B/D (11.50) ratios indicated the high colonizing ability of Ae. albopictus in nature.

Field evaluations of the granular fly bait, Quick Bayt and the paint-on fly bait, Agita against synanthropic flies.

The efficacy and residual efficacy of commercial baits, Quick Bayt (0.5% w/w imidacloprid) and Agita (10.0% w/w thiamethoxam) against synanthropic flies were evaluated under field conditions. Efficacy was evaluated based on knockdown percentage (KD %). The bait efficacy and residual efficacy evaluation were conducted for a period of 3 weeks and 6 weeks respectively. Baits were applied onto bait targets and placed on fly-count targets to facilitate the counting of flies. All baits were applied according to the manufacturer's recommended application rate. Three replicate treatments for each type of bait were placed at the study site each week. The number of flies feeding on baits and the knocked down flies were counted and collected. The efficacy of Agita and Quick Bayt did not differ significantly (t-test, P>0.05) over the 3-week period, even though Quick Bayt had a slightly higher KD% than Agita. In the residual efficacy evaluation, the (knockdown) KD% of Quick Bayt was consistent at around 36% for the first five weeks but dropped to 33.8 +/- 0.4% on the sixth week. The KD% for Agita on the first week was 33.6 +/- 12.2% and remained relatively consistent for the first 4 weeks at around 31%. KD% dropped to 16.7 +/- 3.3% on week 5 and to 15.7 +/- 1.2% on week 6. The difference in residual efficacy of the two baits was significant (t-test, p < 0.05).

Species composition surveys of synanthropic fly populations in northern peninsular Malaysia.

Three species composition surveys were conducted in a rural location in Kedah and an urban location in Pulau Pinang. Two of the surveys were conducted in November 2003, the first was at the Kedah site and the second was at the Pulau Pinang site. The third survey was conducted at the Pulau Pinang site again on the last week of April 2004. All these surveys were conducted one week prior to field evaluations of commercial chemical fly baits. The predominant species recovered from the surveys was the house fly, Musca domestica, which ranked first in prevalence in all three studies. Catches of Musca sorbens, Chrysoma megacephala and Lucillia cuprina were lower than M. domestica. Sarcophaga sp. was not present at the Kedah site and was only present at the Pulau Pinang site during the survey in April 2004. The other fly species present at the Kedah site were Megaselia sp., Psycoda sp., Piophila sp. and Fannia sp. These species were scarce and never exceeded 1% of the total catch.

Daily foraging pattern and proteinaceous food preferences of Solenopsis geminata (Fabricius) (Hymenoptera:Formicidae).

A field study on foraging activity and proteinacous food preference was performed on the tropical fire ant (Solenopsis geminata) (Fabricius) at the School of Biological Sciences and Desasiswa Bakti Permai, Universiti Sains Malaysia (USM), Penang. Foraging activity studies of 4 colonies of S. geminata were conducted in the field for 24 hours. Foraging activity significantly increased 4 hours before sunset and maximum foraging occurred at midnight until early morning. Three types of proteinacous food; anchovy, meat and egg yolk were tested among the five colonies of S. geminata in the field. The egg yolk was the most preferred food (100%) followed by meat (31%) and anchovy (15%).