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.

Filth flies associated with municipal solid waste and impact of delay in cover soil application on adult filth fly emergence in a sanitary landfill in Pulau Pinang, Malaysia.

Two types of municipal solid waste (MSW), newly arrived and 2 weeks old, were sampled from a sanitary landfill in Pulau Pinang, Malaysia at a fortnightly interval and kept under field conditions for 2 weeks. A total of 480 kg of each type of MSW was sampled to study species composition and impact of delays in cover soil applications on filth fly emergence. Out of 960 kg of MSW sampled, 9.2 ± 0.5 flies emerged per kilogram. Weekly adult fly emergence rates of newly arrived and 2-week-old waste did not differ significantly and MSW remained suitable for fly breeding for up to 1 month. Eight species of flies emerged from the MSW: namely, Musca domestica, Musca sorbens, Synthesiomyia nudiseta, Hydrotaea chalcogaster, Chrysomya megacephala, Lucilia cuprina, Hemipyrellia ligurriens and Sarcophaga sp. Newly arrived waste was determined to be the main source for M. domestica, C. megacephala and L. cuprina in the landfill owing to significantly higher mean emergence compared with 2-week-old waste. Musca sorbens was found in newly arrived waste but not in 2-week-old waste, suggesting that the species was able to survive transportation to landfill but unable to survive landfill conditions. Hemipyrellia ligurriens, H. chalcogaster and S. nudiseta were not imported into the landfill with MSW and pre-existing flies in and around the landfill itself may be their source. The results show that landfills can be a major source of fly breeding if cover soil or temporary cover is not applied daily or on a regular schedule.

The biology and demographic parameters of Aedes albopictus in northern peninsular Malaysia.

OBJECTIVE: To generate life table characteristics for the dengue vector Aedes albopictus (A. albopictus) under uncontrolled conditions, incorporating both the aquatic and the adult stages. METHODS: Ten females derived from wild pupae were allowed to fully blood-feed on restrained mice. 774 eggs were hatched in seasoned water. F1 larvae were followed for development until their F2 counterparts emerged as adults. Some population parameters were monitored (F1) or estimated (F2). RESULTS: A. albopictus exhibited increased fecundity and egg hatch success. Immature development was quick. Immature survival was high, with lowest rate in the pupal stage. Adult emergence was about 81% and sex ratio was close to 1:1. Generational mortality (K) was about 28%. A high proportion of females completed a reproductive cycle and the obtained parity rate was predicted to lead to higher fecundity in the next generation. CONCLUSIONS: It can be concluded that natural A. albopictus populations in Penang seem largely determined by quick development in combination with low immature loss and increased oviposition.

Comparative performance of two commercial neonicotinoid baits against filth flies under field conditions.

Two performance (efficacy and attractiveness) comparisons of neonicotinoid baits QuickBayt® (imidacloprid) and Agita® (thiamethoxam) against filth flies were conducted under field conditions to determine suitability for use outdoors. The first experiment compared bait performance and the second compared effects of different applications on QuickBayt® performance. Applications compared were: (i) scattered in petri dish (SPD); (ii) wet-down in petri dish (WPD); (iii) scattered on cardboard (SCB) and (iv) painted on cardboards (PCB). Efficacy and attractiveness were assessed based on knockdown percentage (KD%) and number of flies feeding on baits, respectively. The KD% of QuickBayt® (34% ± 3.0%) was not significantly higher than Agita® (29% ± 1.3%) (t-test, P>0.05). Agita® (101 ± 5.7 flies) was significantly more attractive to flies than QuickBayt® (76 ± 4.8 flies) and the sugar solution (49 ± 7.2) (one-way ANOVA, P<0.05). The PCB and SCB applications were significantly more attractive to filth flies than WPD and SPD (One-way ANOVA, P<0.05), however differences in KD% were not significantly different (One-way ANOVA, P>0.05). The two baits provided the same level of efficacy in a wide-open area against filth flies of various species. QuickBayt® was more versatile; efficacy was not significantly affected by different applications. Surface area and moisture affects attractiveness of the bait.

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%).