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Open access

Othman Wan-Norafikah, Wasi Ahmad Nazni, Han Lim Lee, Pawanchee Zainol-Ariffin and Mohd Sofian-Azirun

Abstract

Background: Insects control using insecticides is used extensively and intensively in vector control programs in many countries including Malaysia. Because of this, mosquito species have been found to develop various levels of resistance towards these insecticides, leading to failure in vector control activities.

Objectives: We determined permethrin resistance status in laboratory susceptible, permethrin-selected, and field strains of Aedes albopictus.

Methods: The susceptibility status of laboratory susceptible strain, permethrin-selected strain, and four field strains of Aedes albopictus collected from Kuala Lumpur were determined using three standard laboratory tests, WHO larval bioassay, WHO adult mosquito bioassay, and microassay of mixed function oxidases (MFOs).

Results: The LC50 values of permethrin-selected strain and field strains obtained from the WHO larval bioassay were almost two times higher (0.38-0.44 mg/L) than the LC50 value of the laboratory strain (0.20 mg/L). In the WHO adult bioassay, the susceptibility of permethrin-exposed of both permethrin-selected strain, and field strains (LT50 = 19.39 to 20.65 min) were reduced for 1.31 to 1.72 times after been exposed to the synergist, piperonyl butoxide (PBO) prior to permethrin. Complete mortalities were also recorded in both permethrin-exposed and PBO + permethrin-exposed Ae. albopictus of all strains, twenty-four hours post-exposure. For the MFOs enzyme microassay, a significant difference (p <0.05) in the mean absorbance of elevated oxidase activity at 630 nm was observed between all strains of both the non-exposed and PBO-exposed Ae. albopictus. Strong and significant positive correlations were also observed between LT50 values of permethrin-exposed and PBO + permethrinexposed with oxidase level in Ae. albopictus tested (r = 0.943; p <0.05).

Conclusion: These results indicate the association of oxidase activity with permethrin resistance development in Ae. albopictus.

Open access

Chong Chin Heo, Baha Latif, Hiromu Kurahashi, Siew Hwa Tan, Wai Kian Chew, Wasi Ahmad Nazni and Baharudin Omar

Abstract

A preliminary study on the ecological activities of necrophagous Diptera on a highrise building in Malaysia was conducted from April to August 2010. Fresh chicken livers (approximately 500 g) serving as bait were placed on the rooftop (101.6 m from the ground). Three replicates were carried out, each replicate lasting 30 days with daily observations and fly sampling. Maggots found in the bait were collected at random: some were preserved in 70% ethanol while the others were reared to the adult stage. Results showed that the flies arrived on the bait between 8 hours and 3 days after placement. The oriental latrine blow fly Chrysomya megacephala (Diptera: Calliphoridae) was the first to reach this altitude, followed by the scuttle fly Megaselia scalaris (Diptera: Phoridae) and the flesh fly Liopygia ruficornis (Diptera: Sarcophagidae). The larvae of Chrysomya megacephala were first recovered from the bait. However, they were succeeded by sarcophagid larvae. The predominant sarcophagid larvae were then raised to the adult stage and the resulting adults were identified as Parasarcophaga dux. The other sarcophagid pupae were either parasitized by hymenopteran parasitoids or dead. We recorded two species of parasitoids emerging from Liopygia ruficornis pupae: Exoristobia philippinensis (Hymenoptera: Encyrtidae) and Dirhinus himalayanus (Hymenoptera: Chalcididae). Liopygia ruficornis is recorded as a new host for these parasitoids for the first time.

Open access

Thary Gazi Goh, Chee Dhang Chena, John Jeffery, Amri Azizan Izzul, Koon Weng Lau, Han Lim Lee, Rosli Ramli, Wasi Ahmad Nazni and Mohd Sofian-Azirun

Abstract

Background: Blowflies (order: Diptera, family: Calliphoridae) and house flies (order: Diptera, family: Muscidae) are important indicators to determine postmortem intervals in forensic entomology. Knowledge of the ecology and bionomics of individual species is necessary for the use of these flies as forensic indicators. Baited trapping is often employed to collect flies for such studies. However, the effect of baits on the diversity and abundance of baited trap collections is not known.

Objective: To compare the sampling effectiveness of several types of bait in terms of diversity and abundance of forensically important flies.

Materials and methods: The effectiveness of belacan (fermented shrimp paste), sugar, beef, ox liver, and fish were tested in three locations at different altitudes in Malaysia; Gombak Field Study Station (about 200 m above sea level (a.s.l.); N3°19′28″, E101°45′09″), Awana (about 1100 m a.s.l.; N3°24′03″ E101°46′59″) and Bukit Cincin (about 1700 m a.s.l.; N3°25′58″ E101°47′05″).

Results: Fish consistently attracted more flies and species than other baits. Beef and ox liver produced moderate or inconsistent results. Flies were rarely attracted to preserved baits such as shrimp paste or odorless baits such as sugar. At higher elevations, flies were attracted to a wider variety of baits. Meat may cause a bias towards mated gravid females and produce a biased sample of the true population.

Conclusion: Fish produced the most consistent results in terms of highest number of flies collected and wide diversity of species sampled, odor, especially from rotting meat, is important in attracting carrion flies.