Present status of the insecticide susceptibility of Aedes mosquitoes in Thailand

デング熱の伝播を止めるのに現在使われている方法は、流行地域に殺虫剤を噴霧することである。そのような場合、媒介昆虫の殺虫剤感受性についての情報があれば、適切な殺虫剤を散布できるであろう。このことは対策プログラムの重要な要素でもある。そこで、WHO 感受性評価キットを使って、ネッタイシマカAedes aegypti とヒトスジシマカAe.albopictus の殺虫剤に対する感受性を調べた。2008 年から2010 年にかけて、バンコク、Phra Nakhon Si Ayutthaya(プラ・ナコーン・シー・アユタヤー)、Chantha Buri(チャンタブリー)、Prachin Buri(プラチンブリー)で採集し、実験室で飼育した蚊の成虫または幼虫に、WHO が推奨している識別判定が可能な投与量の殺虫剤に1 時間暴露させ、24時間後の死亡率を調べた。おおむね、ネッタイシマカはマラチオンを除く全ての殺虫剤に対して耐性あるいは抵抗性を示した。殺虫剤抵抗性の程度は、バンコク、プラ・ナコーン・シー・アユタヤー、プラチンブリー、チャンタブリーで、それぞれ高いレベルから低いレベルまで分布していた。バンコクのBang Khae(バンケー)区およびThung Khru(トゥンクル)区では、殺虫剤に対する抵抗性が毎年増してきていた。ピレスロイド抵抗性と関係があるノックダウン型抵抗性(kdr)型抵抗性が、ネッタイシマカで観察された。一方、プラチンブリー、バンコク、Phang-nga(パンガー)から採集したヒトスジシマカは、DDT に対して耐性を示した。しかし、ピレスロイドあるいはマラチオンに対して耐性/ 抵抗性を示したヒトスジシマカはいなかった。The current method for interrupting dengue fever transmission is spraying insecticide in the area affected by the epidemic. In such cases, information about the insecticide susceptibility of the vector would allow an appropriate insecticide to be applied. It is also a key factor for control programs. Therefore, the insecticide susceptibility of Aedes aegypti and Ae. albopictus were investigated using the WHO susceptibility test kit. Adult mosquitoes or larvae collected from Bangkok, Phra Nakhon Si Ayutthaya, Chanthaburi, and Prachin Buri from 2008-2010 and reared in a laboratorywere exposed to insecticide for 1 hour at discriminating diagnostic doses recommended by the WHO, and mortality was examined after 24 hour. In general, Ae. aegypti were tolerant or resistant to all insecticides except malathion. Their degrees of insecticide resistance ranged from high to low in Bangkok, Phra Nakhon Si Ayutthaya, Prachin Buri, and Chanthaburi, respectively. In the Bang Khae and Thung Khru districts of Bangkok, insecticide resistance increased each year. knock down resistance, which is related to pyrethroid resistance, was observed in Ae. aegypti. On the other hand, Ae. albopictus from Prachin Buri, Bangkok, and Phang-nga were able to tolerate DDT. However no Ae. albopictus that were tolerant/resistant to pyrethroid or malathion were found in this study

Susceptibility of Aedes flavopictus miyarai and Aedes galloisi mosquito species in Japan to dengue type 2 virus

Objective: To evaluate the potential of local mosquitoes to act as vectors for dengue transmission in Japan. Methods: Serotype 2 ThNH28/93 was used to test the dengue susceptibility profiles of Aedes flavopictus miyarai (Ae. f. miyarai), Aedes galloisi (Ae. galloisi) and Aedes albopictus (Ae. albopictus), which were collected in Japan. We used Aedes aegypti from Thailand as a positive control. The mosquitoes were infected with the virus intrathoracically or orally. At 10 or 14 days post infection, the mosquitoes were dissected and total RNA was extracted from their abdomens, thoraxes, heads and legs. Mosquito susceptibility to dengue virus was evaluated using RT-PCR with dengue virus-specific primers. Differences in the infection and mortality rates of the different mosquito species were tested using Fisher's exact probability test. Results: The infection rates for dengue virus administered intrathoracically to Ae. f. miyarai, Ae. galloisi and Aedes aegypti mosquitoes were identical by RT-PCR on Day 10 post infection. All of the body parts we tested were RT-PCR-positive for dengue virus. For the orally administered virus, the infection rates in the different body parts of the Ae. f. miyarai mosquitoes were slightly higher than those of Ae. albopictus mosquitoes, but were similar to the control mosquitoes (P > 0.05). The mortality rates for Ae. f. miyarai and Ae. albopictus mosquitoes were similar (P = 0.19). Our data indicated that dengue virus was able to replicate and disseminate to secondary infection sites in all of the four mosquito species (Japanese and Thai). Conclusions: Ae. albopictus is a well-known candidate for dengue transmission in Japan. However, our data suggest that Ae. f. miyarai from Ishigaki Island (near Okinawa Island) and Ae. galloisi from Hokkaido (Northern Japan) should also be regarded as potential vectors for dengue transmission in these regions. Further studies on these mosquitoes should be conducted

Global research alliance in infectious disease: a collaborative effort to combat infectious diseases through dissemination of portable sequencing

Objective: To disseminate the portable sequencer MinION in developing countries for the main purpose of battling infectious diseases, we found a consortium called Global Research Alliance in Infectious Diseases (GRAID). By holding and inviting researchers both from developed and developing countries, we aim to train the participants with MinION’s operations and foster a collaboration in infectious diseases researches. As a real-life example in which resources are limited, we describe here a result from a training course, a metagenomics analysis from two blood samples collected from a routine cattle surveillance in Kulan Progo District, Yogyakarta Province, Indonesia in 2019. Results: One of the samples was successfully sequenced with enough sequencing yield for further analysis. After depleting the reads mapped to host DNA, the remaining reads were shown to map to Theileria orientalis using BLAST and OneCodex. Although the reads were also mapped to Clostridium botulinum, those were found to be artifacts derived from the cow genome. An effort to construct a consensus sequence was successful using a reference-based approach with Pomoxis. Hence, we concluded that the asymptomatic cow might be infected with T. orientalis and showed the usefulness of sequencing technology, specifically the MinION platform, in a developing country