ABSTRACT
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 admin-istered 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.
ABSTRACT
Objective:Accurate laboratory testing is a critical component of dengue surveillance and control. The objective of this programme was to assess dengue diagnostic proficiency among national-level public health laboratories in the World Health Organization (WHO) Western Pacific Region.Methods:Nineteen national-level public health laboratories performed routine dengue diagnostic assays on a proficiency testing panel consisting of two modules: one containing commercial serum samples spiked with cultured dengue viruses for the detection of nucleic acid and non-structural protein 1 (NS1) (Module A) and one containing human serum samples for the detection of anti-dengue virus antibodies (Module B). A review of logistics arrangements was also conducted.Results:All 16 laboratories testing Module A performed reverse transcriptase polymerase chain reaction (RT–PCR) for both RNA and serotype detection. Of these, 15 had correct results for RNA detection and all 16 correctly serotyped the viruses. All nine laboratories performing NS1 antigen detection obtained the correct results. Sixteen of the 18 laboratories using IgM assays in Module B obtained the correct results as did the 13 laboratories that performed IgG assays. Detection of ongoing/recent dengue virus infection by both molecular (RT–PCR) and serological methods (IgM) was available in 15/19 participating laboratories.Discussion:This first round of external quality assessment of dengue diagnostics was successfully conducted in national-level public health laboratories in the WHO Western Pacific Region, revealing good proficiency in both molecular and serological testing. Further comprehensive diagnostic testing for dengue virus and other priority pathogens in the Region will be assessed during future rounds.
ABSTRACT
In late August 2014, three autochthonous dengue cases were reported in Japan. Since then, as of 17 September 2014, a total of 131 autochthonous cases have been confirmed. While cases were reported from throughout Japan, the majority were linked to visiting a large park or its vicinity in Tokyo, and the serotype detected has been serotype 1. We report preliminary findings, along with the public health response activities, of the first documented autochthonous dengue outbreak in Japan in nearly 70 years.Dengue is an acute, mosquito-borne febrile illness caused by a flavivirus found widely in the Asia-Pacific region, particularly in South-East Asia. While the most competent mosquito species for dengue virus transmission is believed to be Aedes aegypti, Aedes albopictus is also a competent vector present in much of Japan during the warmer months. Infection with dengue virus may cause fever, headache, muscle pain and/or rash but may also be mild or asymptomatic. While there is no specific treatment, with early and appropriate medical care, the likelihood of infections resulting in severe forms or death is rare. In Japan, dengue has been a notifiable disease since April 1999. Physicians are required to report demographic, clinical and exposure history information of laboratory-confirmed cases to the local public health centre that are then reported to the Ministry of Health, Labour and Welfare (MHLW) and the National Institute of Infectious Diseases (NIID).