Zika virus (Flaviviridae) is an emerging arbovirus. It was first isolated from rhesus monkeys in Zika forest in Uganda in 1947 and was isolated from Aedes africanus mosquitoes collected from the canopy of Zika forest in 1948. The first human case was reported in Nigeria in 1954. For half a century, the virus was reported to cause sporadic human infections in Africa and Asia, with mild symptoms comparable to dengue. In 2007, a Zika disease epidemic occurred in the Yap Islands, Micronesia. In 2013 a large epidemic was reported in French Polynesia with more than 70 cases of Guillain-Barre syndrome and other neurological conditions, and 333 confirmed Zika cases. There were more than 30,000 cases of suspected Zika infection in French Polynesia in 2013. Following this, a Zika outbreak on the Cook Islands of New Caledonia was reported, with 932 suspected and 50 confirmed cases, and 51 confirmed cases were reported on Easter Island in 2014. In early 2015, several patients presenting symptoms of mild fever, rash, conjunctivitis and arthralgia were reported in northeastern Brazil. It seems there were more than 1.5 million cases of Zika disease in Brazil. The Brazilian epidemic of microcephaly in newborn infants is of greater concern. In the northeastern states, a greater than 20-fold increase in the incidence of microcephaly was observed from 2014 to 2015. Some public health officials believe that there is a strong relationship between Zika virus infection in pregnant women and microcephaly. Microcephaly and other fetal malformations that are potentially associated with Zika virus infection or suggestive of congenital infection have been reported in Brazil, Cabo Verde, Colombia, French Polynesia, Martinique and Panama, although the incidence of microcephaly was different in each endemic country. Scientists at the Centers for Disease Control and Prevention (CDC) reviewed the existing evidence and concluded that Zika virus is a cause of microcephaly and other severe fetal brain defects.

The vector mosquitoes belong to the genus Aedes. It is known that the vector species differ in each epidemic areas. In the Yap Islands, Ae. hensilli seems to be the vector, while the vectors in French Polynesia were apparently Ae. polynesiensis and Ae. aegypti; however, the virus has not been isolated from these species. In Brazil, Zika virus might be transmitted by Aedes aegypti and Ae. albopictus. The possibility that Zika virus has become highly adapted to Ae. albopictus should be cause for concern, even in temperate countries in Asia, Europe and North and South America.

In Akita Prefecture, patients with Kato type of tsutsugamushi disease (Sucrub typhus) transmitted by Leptotrombidium akamushi were identified in August 2008 for the first time in 15 years, and in 2010 as well. We conducted surveys of the habitat of L. akamushi using Suzuki’s Method (MITORI-HO) between 2011 and 2014 in 74 areas of riverbed in which the disease was prevalent, including the upstream, midstream, and tributary areas of the Omono River. Habitats of L. akamushi were identified in 40 areas in three cities and one town, and the total distance along Omono River was approximately 10 km shorter than that reported by a survey conducted in 1964. Some of those areas were inhabited by L. akamushi gradually after river improvement work and the disease temporarily became prevalent there, although no patient had been identified in these areas prior to the construction. L. akamushi was only collected from sand, sandbanks, and other areas in the vicinity of the river, which can easily be flooded when the water level rises. No extensive research has been conducted on the re-emergence of tsutsugamushi disease transmitted by L. akamushi. It is necessary to continue to provide people with information and increase their awareness.

According to the literature, the northern limit of distribution for the cockroach, Blattella nipponica Asahina was near Tokyo in 1999. In 2012, it was reported that this cockroach was observed up to Iwaki City, Fukushima Prefecture in the Pacific Ocean coastal areas and Nasushiobara City, Tochigi Prefecture in the inland. In the present study, we investigated the distribution of B. nipponica in the Kanto and Tohoku districts during a period from May to September, 2015. This cockroach was observed at an altitude less than 150 m at 11 localities in 2 prefectures. In the coastal areas, B. nipponica was found commonly from the northern part of Ibaraki Prefecture (36.86°N) to Naraha-machi (37.30°N), Fukushima Prefecture and less commonly in Tomioka-machi (37.33°N), Fukushima Prefecture., However, no individual was observed in Ohkuma-machi (37.38°N). The results suggested that the northern limit of distribution for B. nipponica was Akagi, Motooka, Tomioka-machi, Fukushima Prefecture (37.34°N, 40.96°E), indicating that the northern limit moved northward as much as approximately 190 km in 24 years.

A total of 512 mosquito specimens, collected in 2013 and 2014 from 18 study sites from Hokkaido to Kagoshima, Japan, were analyzed for DNA barcoding based on the nucleotide sequence of cytochrome c oxidase subunit I (COI) region, following which the gene sequences of 240 mosquitoes from 45 species in 11 genera were registered in GenBank. Aedes mosquitoes with black legs that belong to the punctor-subgroup, such as Ae. punctor and Ae. communis, found in northern Japan, were difficult to identify morphologically, but the specimens separated into two genetically distinct populations by COI gene sequence analysis. Morphological differences between the two populations were examined and the presence of postprocoxal scales was suggested as a key characteristic for identifying female specimens. The intraspecific divergence of nucleotide sequence was examined using Kimura two-parameter distance model for each species; 44 species showed an average sequence divergence at less than 2%, except for Anopheles lindesayi japonicus. Intraspecific variation in nucleotide sequence and neighbor-joining phylogenetic analyses indicated the existence of genetically heterogeneous populations in the following Japanese mosquito species: An. lindesayi japonicus, Culex rubensis, Cx. hayashii hayashii, Cx. kyotoensis, Ae. esoensis, and Toxorhynchites towadensis.

横浜市街で2014～2016年の2月または3月に捕獲したドブネズミの齢構成（水晶体重量から月齢を推定）から，個体群への加入数の季節的変動を調べた．捕獲された12カ月齢までの27頭（2014年），43頭（2015年）および27頭（2016年）を見ると，加入数の山は8～10月の高温期にある場合，1月の寒冷期にある場合，および春・秋の二峰性を示す場合があった．山が年によって異なることは，気温以外の要因が繁殖活動に影響していることを示す．