The objectives of the present study were to observe the temporal pattern of avian influenza virus (AIV) introduction into Japan and to determine which migratory birds play an important role in introducing AIV. In total, 19,407 fecal samples from migratory birds were collected at 52 sites between October 2008 and May 2015. Total nucleic acids extracted from the fecal samples were subjected to reverse transcription loop–mediated isothermal amplification to detect viral RNA. Species identification of host migratory birds was conducted by DNA barcoding for positive fecal samples. The total number of positive samples was 352 (prevalence, 1.8%). The highest prevalence was observed in autumn migration, and a decrease in prevalence was observed. During autumn migration, central to southern Japan showed a prevalence higher than the overall prevalence. Thus, the main AIV entry routes may involve crossing the Sea of Japan and entry through the Korean Peninsula. Species identification was successful in 221 of the 352 positive samples. Two major species sequences were identified: the Mallard/Eastern Spot-billed duck group (115 samples; 52.0%) and the Northern pintail (61 samples; 27.6%). To gain a better understanding of the ecology of AIV in Japan and the introduction pattern of highly pathogenic avian influenza viruses, information regarding AIV prevalence by species, the prevalence of hatch-year migratory birds, migration patterns and viral subtypes in fecal samples using egg inoculation and molecular-based methods in combination is required.
There is limited information about virus epidemiology of shorebirds (family Charadriidae and Scolopacidae) in the East Asia-Australasia flyway. We investigated the prevalence of avian influenza viruses (AIVs) in shorebirds in Hokkaido, Japan, the stopover site of the flyway, to understand the ecology of AIV translocation in the flyway from 2006 to 2010. In total, 1,698 shorebirds belonging to 26 species were captured and released into two different sites using mist nets. Tracheal and cloacal swabs were collected from each bird using cotton swabs. The RNA of influenza A viruses was detected using reverse transcription loop-mediated isothermal amplification. One AIV-positive sample was obtained from a Lesser Sand Plover (Charadrius mongolus) captured in September 2010 at Lake Komuke. Full lengths of hemagglutinin (HA), neuraminidase (NA), polymerase acidic protein, nucleoprotein, matrix protein 1, and nuclear export protein genes were successfully amplified from the AIVpositive sample. All sequences showed the highest identity with sequences obtained from virus strains from Anseriformes species. Shorebirds migrated to Japan 1 mo earlier than did Anseriformes species. Therefore, the Lesser Sand Plover could have been infected by the virus from Anseriformes species on the breeding grounds. The HA sequence showed the highest identity with the H10 sequence whereas the NA sequence exhibited the highest identity with the N7 sequence. Phylogenic analysis showed that the detected subtype H10N7 belongs to the Eurasia lineage and the related strain might have widely spread in Asia in 2009.
An adult male grey heron, Ardea cinerea (Aves: Ciconiiformes), was rescued in Mikunigaoka 590-0021, Sakai, Osaka, Japan, and euthanized because of severe injury to both legs. At necropsy, a large number of deutonymphs (hypopi) of the hypoderatid mite, Hypodectes propus (Acarina: Hypoderatidae), were found in the subcutis and in the fasciae of the adipose tissue in the pectoral muscle and abdominal regions. The mites were 1.26 mm in length and 0.35 mm in width on average. The present hypopi were identified as H. propus, based on the dimensions of the mite, together with the distinct typical coxal apodemes in the anterior part. The present case reported the subcutaneous mite, H. propus, in the grey heron, A. cinerea, as a new host record in Japan.
A Japanese golden eagle, Aquila chrysaetos japonica, was found dead in Nagano Prefecture PB 399-8200, Japan, and subjected to necropsy. The necropsy revealed that the entire length of the intestine was filled with several masses of intestinal parasites. The recovered helminths were identified as one digenean trematode species, Neodiplostomum reflexum; two species of nematodes, Synhimantus sp. and larvae of Porrocaecum sp.; and a single species of Acanthocephala, Centrorhynchus sp. Digenea and acanthocephalans were found in massive numbers, obliterating the intestinal lumen, which suggests that the bird died as a result of the parasitic intestinal obstruction. The same type of helminths as those observed in this case was previously recorded in crested serpent eagles (Spilornis cheela perplexus) in Japan, but the present study emphasizes the presence of the four species in the Japanese golden eagle as a new host record. To the authors' knowledge, this is the first report of N. reflexum in Japan.
Background Despite considerable environmental changes over the last 160 years, 1,2 Japan is an important transit country for a wide range of migratory avian species. It is situated on the East Asian Flyway, a principal migratory route connecting Northeast Asia with Southeast Asia. Major branches pass through the Nansei-Shoto Islands, Kyushu, Honshu, and Hokkaido into northeast Russia, and via Kyushu and the Korean Peninsula into eastern China. 3 So far, Japan has escaped the outbreaks of infectious disease that have significantly impacted bird populations in other parts of the world. 1,2,4 During these outbreaks, tens of thousands of birds become sick leading to death in extreme cases. 5 In addition to the changing avian fauna and ecosystems in Japan, a large number of captive birds are kept in over 150 zoological gardens and/or aquariums throughout the country (http://www.jaza. jp/z_map/z_seek00.html). It is therefore likely that these captive birds would also be affected if a disease outbreak occurs. Although there are numerous infectious diseases that affect both free-ranging and captive avian species, this review contains a brief overview of the situation regarding avian influenza (AI) in Japan, as well as suggestions for the implementation of countermeasures for the prevention and management of potential AI outbreaks. First described in the late 19th century, AI is a highly contagious viral disease affecting birds, especially poultry, worldwide. AI viruses are generally isolated from wild birds, particularly migratory waterfowl belonging to the orders Anseriformes and Charadriiformes, which are considered natural reservoirs of the viruses. 5 However, since 2004, highly pathogenic (HP) AI has been classified as a typical and re-emerging infectious disease of avian species by the Japanese government and the science community responsible for animal health. 1-4 Therefore, the current review provides an overview of recent changes in AI and its causative agents in both free-ranging and captive avian species worldwide, including Japan, and provides potential strategies to manage epidemic risk in facilities with captive birds or zoological collections. General characteristics of AI and its causative agents AI is caused by influenza type A viruses, consisting of negativesense, single-stranded RNA viruses belonging to the family Orthomyxoviridae. Influenza A virus genomes contain eight segments encoding 11 proteins. Segments one to six encode PB2, PB1, PB1-F2, PA, hemagglutinin (HA), nucleoprotein NP, and neuraminidase (NA) in decreasing order in size. The seventh and eighth segments encode M1, M2, NS1, and NS2. The viruses are further categorized into various subtypes based on the combination of HA (H1-H16) and NA (N1-N9) antigens. Various influenza A virus subtypes occur in wild birds, especially aquatic species, and may also infect mammals such as humans and pigs. 1,3,6 AI viruses are globally distributed and are probably prevalent in area with higher host population. 3 AI or its causative viruses have been reporte...
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