In 1983, four paragonimiasis cases were diagnosed in people who had consumed uncooked freshwater crabs captured from the Yourou River in Otaki-machi, Chiba Prefecture, Japan. Although a field survey conducted about 30 years ago demonstrated that the diploid form of Paragonimus westermani was extensively distributed in Otaki-machi, its prevalence in other areas was not well examined. In this study, we examined the infection status of Paragonimus metacercariae in the Japanese freshwater crab Geothelphusa dehaani collected from the Kobado area of Katsuura City in Chiba Prefecture from 2011 to 2014. Our findings indicated that the prevalence was 82.1% in 2011 and reached close to 100% between 2012 and 2014. Additionally, the average rate of metacercariae infection in freshwater crabs for four years was 94.3%, with the number of metacercariae per infected crab ranging from 1 to 329 (mean: 27.8). The lung flukes examined were identified as the diploid form of P. westermani based on both the morphological features of the metacercariae and molecular analyses of the nuclear ribosomal internal transcribed spacer 2 region and mitochondrial 16S rRNA genes. These results suggested that the natural life cycle of the diploid form of P. westermani remained well-preserved in Chiba Prefecture. In addition, the Kobado area was added as a new prevalent locality of this lung fluke in Japan.
In order to control adult blackflies in the upper reaches of the Ukawa River in Kashiwazaki City, Niigata Prefecture, the present study was conducted on the larval habitats of blackfly at a total of 128 sites (a total of 319 sampling times) around the river, small stream and the waterway in the upper reaches of the Ukawa River Basin from June to October in 2013. A total of 12,805 individual blackfly larvae and pupae were captured during the investigation periods. The average number of larvae per site was 40.1 individuals/two investigators·5 minutes and we could collect blackfly larvae and pupae at almost all sampling sites. Noda was the highest capture area where we could collect 51.6 individuals/two investigators⋅5 minutes, followed by the Joujou Area. The fewest captures were in the Betsumata Area (19.5 individuals/two investigators⋅5 minutes). The dominant species was Simulium (Simulium) bidentatum (Shiraki, 1935) (279 total individuals, 34.8%), followed by Simulium (Simulium) quinquestriatum (Shiraki, 1935)(225, 28.1%), and Simulium (Simulium) japonicum Matsumura, 1931 (101, 12.6%).
Hybomitra litoralis sp. nov. is described from Japan. This new species is distinguished from others within the same genus by the following characteristics: the broad and nearly parallel-sided frons and the conspicuous frontal calli stretching from eye to eye. The habitat of H. litoralis sp. nov. is probably limited to the seashore, since all the specimens were collected in that area.
Oncomelania hupensis nosophora (Ohn) is the intermediate snail host of Schistosoma japonicum (Trematoda; Schistosomatidae) (Sj) in Japan. The last domestic schistosomiasis infection in Japan has been thought to occur in Yamanashi Prefecture in 1977. In 1985, the intermediate host snail was isolated from paddy fields along the Obitsu River basin in Chiba Prefecture, Japan. At that time, schistosomiasis was assumed to become a past disease in this area. Thus, activities to exterminate Ohn or annual screening programs of residents in this area had not been conducted. Indeed, this disease represents a neglected endemic disease in Japan. This report describes the epidemiological history of the disease from various approaches including clinical information, philological study, interview surveys, snail collection surveys, and changes in land use and environments using geographic information systems. The assumption of disease elimination was based on the lack of reports of new infection for more than 30 years, environmental modifications, and almost no snail infestation from 2012 onward in known habitats. We concluded that continuous monitoring of the snails is not necessary in the studied area, while a certain level of attention to redistribution of the snail from hidden habitats may be required.
Mosquito collection was carried out monthly using dry-ice traps at Yonago Waterbirds Sanctuary, Tottori Prefecture, Japan, and Culex inatomii was found to be present at a high density. One gynandromorph specimen of Cx. inatomii was collected in July 2017 and the morphology of the head, abdomen, and anterior claws of the foretarsi and midtarsi was examined and the sex was determined. The head and the right midtarsus were identified as female, whereas the abdomen and the left foretarsus and left midtarsus were male. These results indicated that the specimen had the head of a female, the abdomen of a male, and the thorax was divided bilaterally or obliquely. This gynandromorphic finding is the first report for Cx. inatomii worldwide.