Abstracts for the Annual Meetings of the Japan Society of Medical Entomology and Zoology

Ascogregarines are protozoan parasites of the phylum Apicomplexa, which generally infect insects. So far fourteen species of Ascogregarina have been reported from Culicidae, Psychodidae and Phoridae. In view of the difficulty to identify the parasite by optical microscopic study, the scanning electron microscopic study of the oocysts and gamont stage of the parasite has been undertaken. Besides, the sequencing of ITSI and ITSII region of ribosomal DNA was done as a supportive method of molecular identification of the paraiste. The study revealed a new Ascogregarina parasite, which was found to infect Ochlerotatus j. japonicus. The new Ascogregarina species, e. g. Ascogregarina japonicus demonstrated significant differences in the oocysts and gamonts structure as well as the in its nucleotide sequences of ITSI and ITSII region from the other two well known ascogregarine parasites e. g. A. culicis and A. taiwanensis. In Japan, since Ae. albopictus and Oc. japonicus japonicus often share their larval habitats, the cross infection of the two host by the two different ascogregarine parasites may happen in nature. Therefore, a study of cross infection was also conducted considering the aforesaid two hosts and the two parsites. All the findings will serve as basic bio-molecular information in the field of Ascogregarina research. Key words: New Ascogregarina sp., Ochlerotatus japonicus japonicus, oocysts, ITSI, ITSII.

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Understanding larval behavior can provide insights into larval behavior organization which can be exploited to design new larva control methods.
We compared the behavior of three mosquito species to determine differences in behavior organization and the time budget of each behavior. Transitions from one behavior to another for all observations were collated into a matrix of preceding and succeeding behavior with the diagonal held at logical zero. G-test was used to test first-order transitions for significantly greater occurrence than expected by chance.
The common behavior in Anopheles stephensi larvae was float/interfacial feed followed by bottom feeding, float/suspension feeding and diving. The other behaviors were not common. The common behavior in Aedes albopictus larvae was float/suspension feed followed by rise and brushwall. The other behaviors were not common. The common behavior in Culex pipiens larvae was suspension feed. The other behaviors were not common.
These differences in the behavior organization can be exploited to design new larval control methods or improve existing ones.
Key words: Anopheles stephensi, Culex pipiens, Aedes albopictus, larva, behavior, behavior organization, behavior transition, time budget.

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Anopheles farauti s.s. is a major malaria vector mosquito in the Solomon Islands (SI) and Papua New Guinea (PNG) which are the most malaria endemic countries among Melanesian region. Two major islands (Guadalcanal and Malaita) of SI, and three inland zones (Dagua, Boiken and Kaboibus) along with two offshore islands (Walis and Kairiru) of PNG were evaluated here. Solomon Sea is acting as a potential barrier for gene flow and maintaining significant genetic differentiation between SI and PNG populations, though little or no genetic structuring was detected within each population. Moreover, SI population showed a status of population expansion, whereas PNG showed a stationary state. Beside this, discrepancy was also noted in timing of population expansion and PNG being older.
This work was collaborated with Dr. Masato Kawabata (International Center for Medical Research, Kobe University), Mr. Hugo Bugoro and Mr. Bobogare Albino (Solomon Island Medical Training and Research Institute, Solomon Islands)
Keywords: Anopheles farauti s.s., cytochrome oxidase II, genetic diversity, gene flow, population history, colonization, Melanesia.

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Recent studies of mathematical modeling indicate that theoretical vector density (i.e. adult female Ae. aegypti per person) to cause dengue outbreak can be calculated with average temperature and seloprevalence in a target area. Field collection of Ae. aegypti adults and larvae have been known as problematic. Therefore, pupal collection is considered as an appropriate collection method to estimate the density. Several studies demonstrated the potential of using pupal counts in each container category and theoretical transmission threshold for a selective and cost-effective wet container reduction. We used this "pupal productivity survey" methodology to verify "key" container(s) to suggest an effective vector control in urban area of Vietnam.
The survey was conducted in NhaTrang City in middle Vietnam. Two well-defined study area were selected from central and north area of the city respectively (Area A; 119 premises and 520 residents, Area B; 124 premises and 524 residents). The survey was conducted in dry season (July and August 2006) and rain season (December 2006 and January 2007) by 6 stuff (separated in two teams of NIHE, NhaTrang Pasteur entomology staff and community leader) for 3 or 4 days in one area. All potential wet containers were investigated to record container type, location, volume existence of Ae. aegypti pupae/larvae and their number.
In dry season, concrete tank, old tire and large plastic bucket were main resources of pupae (55% of total collection number); however, these containers were only 10.8% of total number of wet containers. Pupal density in Area B was nearly 3 times more than transmission threshold (pupae per person in area A, B were 0.25, 0.81 respectively and theoretical transmission threshold was 0.3 assuming temperature 29C and seroprevalence 33%). Composition of container type in two areas was significantly differed from and the number of container types with Ae. aegypti highly infested were recorded more in area B. Pupal density in two study area was depended on the existence of few types of containers with high level of Ae. aegypti infestation approach at least during dry season. The survey in rain season was carried out recently and the result will be reported additionally.

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