Life table characteristics of Malaysian strain Aedes albopictus (Skuse)

The survival of a mosquito is the most important aspect that affects its ability as a pathogen transmitting vector, such as Aedes albopictus, which is a vector of chikungunya and dengue. Knowledge on mosquito life demographics is important in providing a foundation for a successful vector control programme. In this study, two strains of Ae. albopictus [Selangor (SEL) and Kuala Lumpur (KL)] were employed in order to determine the life demographics, including the development period, survival rate, mortality rate, and reproductive capability undercontrolled laboratory conditions. A cohort life table was developed based on the data collected. The complete life cycle period was inconsistent and ranged between 6 to 14 days. The males have a shorter survival period compared to the females. The percentage of females surviving and producing eggs has decreased across the gonotrophic cycle for both strains. A fluctuating pattern of oviposition among most of the females was observed throughout the gonotrophic cycle. The apparent mortality was highest at the embryogenesis stage than the other life stages across the gonotrophic cycle, with the pupae stage being recorded as the lowest mortality rate for both strains. Based on the demographic growth parameters calculated in this study, both strains showed favourable capability to be established in the laboratory. The data provided in this study can be used as a basic guideline on the population growth of the mosquito species and their capability as a pathogen vector

Nationwide Investigation of the Pyrethroid Susceptibility of Mosquito Larvae Collected from Used Tires in Vietnam

Pyrethroid resistance is envisioned to be a major problem for the vector control program since, at present, there are no suitable chemical substitutes for pyrethroids. Cross-resistance to knockdown agents, which are mainly used in mosquito coils and related products as spatial repellents, is the most serious concern. Since cross-resistance is a global phenomenon, we have started to monitor the distribution of mosquito resistance to pyrethroids. The first pilot study was carried out in Vietnam. We periodically drove along the national road from the north end to the Mekong Delta in Vietnam and collected mosquito larvae from used tires. Simplified susceptibility tests were performed using the fourth instar larvae of Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus. Compared with the other species, Ae. aegypti demonstrated the most prominent reduction in susceptibility. For Ae. aegypti, significant increases in the susceptibility indices with a decrease in the latitude of collection points were observed, indicating that the susceptibility of Ae. aegypti against d-allethrin was lower in the southern part, including mountainous areas, as compared to that in the northern part of Vietnam. There was a significant correlation between the susceptibility indices in Ae. aegypti and the sum of annual pyrethroid use for malaria control (1998–2002). This might explain that the use of pyrethroids as residual treatment inside houses and pyrethroid-impregnated bed nets for malaria control is attributable to low pyrethroid susceptibility in Ae. aegypti. Such insecticide treatment appeared to have been intensively administered in the interior and along the periphery of human habitation areas where, incidentally, the breeding and resting sites of Ae. aegypti are located. This might account for the strong selection pressure toward Ae. aegypti and not Ae. albopictus

Multimodal pyrethroid resistance in malaria vectors, Anopheles gambiae s.s., Anopheles arabiensis, and Anopheles funestus s.s. in western Kenya.

Anopheles gambiae s.s., Anopheles arabiensis, and Anopheles funestus s.s. are the most important species for malaria transmission. Pyrethroid resistance of these vector mosquitoes is one of the main obstacles against effective vector control. The objective of the present study was to monitor the pyrethroid susceptibility in the 3 major malaria vectors in a highly malaria endemic area in western Kenya and to elucidate the mechanisms of pyrethroid resistance in these species. Gembe East and West, Mbita Division, and 4 main western islands in the Suba district of the Nyanza province in western Kenya were used as the study area. Larval and adult collection and bioassay were conducted, as well as the detection of point mutation in the voltage-gated sodium channel (1014L) by using direct DNA sequencing. A high level of pyrethroid resistance caused by the high frequency of point mutations (L1014S) was detected in An. gambiae s.s. In contrast, P450-related pyrethroid resistance seemed to be widespread in both An. arabiensis and An. funestus s.s. Not a single L1014S mutation was detected in these 2 species. A lack of cross-resistance between DDT and permethrin was also found in An. arabiensis and An. funestus s.s., while An. gambiae s.s. was resistant to both insecticides. It is noteworthy that the above species in the same area are found to be resistant to pyrethroids by their unique resistance mechanisms. Furthermore, it is interesting that 2 different resistance mechanisms have developed in the 2 sibling species in the same area individually. The cross resistance between permethrin and DDT in An. gambiae s.s. may be attributed to the high frequency of kdr mutation, which might be selected by the frequent exposure to ITNs. Similarly, the metabolic pyrethroid resistance in An. arabiensis and An. funestus s.s. is thought to develop without strong selection by DDT

Mothflies (Diptera : Psychodidae) in hospitals: A guide to their identification and methods for their control

Repeated observation of "mothflies" at CHU Brugmann (Horta site hospital in Brussels) is not an isolated incident. Many public buildings have been infested by these Diptera of the Psychodidae Family. Although the species currently seen in Belgium is not a danger to human health, any infestation should be swiftly eradicated so as to limit the risks of a massive proliferation, source of hygiene problems and of potential bacterial dissemination. A good knowledge of adult and larval biology allows the potential sites of infestation to be quickly identified. The method to be envisaged to solve the problem will combine different approaches such as removing the risk factors (decomposing organic matter), monitoring egg-laying sites, applying caustic soda-based products and possibly treating with insecticide

An elusive endosymbiont: Does Wolbachia occur naturally in Aedes aegypti?

Wolbachia are maternally inherited endosymbiotic bacteria found within many insect species. Aedes mosquitoes experimentally infected with Wolbachia are being released into the field for Aedes‐ borne disease control. These Wolbachia infections induce cytoplasmic incompatibility which is used to suppress populations through incompatible matings or replace populations through the reproductive advantage provided by this mechanism. However, the presence of naturally occurring Wolbachia in target populations could interfere with both population replacement and suppression programs depending on the compatibility patterns between strains. Aedes aegypti were thought to not harbor Wolbachia naturally but several recent studies have detected Wolbachia in natural populations of this mosquito. We therefore review the evidence for natural Wolbachia infections in A. aegypti to date and discuss limitations of these studies. We draw on research from other mosquito species to outline the potential implications of natural Wolbachia infections in A. aegypti for disease control. To validate previous reports, we obtained a laboratory population of A. aegypti from New Mexico, USA, that harbors a natural Wolbachia infection, and we conducted field surveys in Kuala Lumpur, Malaysia, where a natural Wolbachia infection has also been reported. However, we were unable to detect Wolbachia in both the laboratory and field populations. Because the presence of naturally occurring Wolbachia in A. aegypti could have profound implications for Wolbachia ‐based disease control programs, it is important to continue to accurately assess the Wolbachia status of target Aedes populations

Validation of sterilization of Lucilia cuprina larvae using raw honey through scanning electron microscope

Background: In the application of Maggot Debridement Therapy (MDT), sterilized maggots (Lucilia cuprina) by standard chemicals were used. Recent potential demands for using a procedure with allnatural products, raw honey has been proposed as a natural sterilization technique to replace the chemical products.Methods: Lucilia cuprina collected from a laboratory colony were divided into treated group (sterilized) and control group (non-sterilized) to undergo sterility testing with honey dilution. Scanning electron microscope (SEM) was used to examine and ascertain the sterility of honey dilution. SEM provided direct observation of microorganism’s presence on external surface L. cuprina after sterilization by disinfectants of raw honey (tualang honey).</p