Mitsuhiko Asakawa

Seroprevalence of Borna disease virus in domestic animals in Xinjiang, China

To investigate the animals infected with Borna disease virus (BDV) in Xinjiang, China, we examined for BDV antibodies in the sera from groups of 20 horses, sheep and cattle, and from 165 wild rodents (18 species) by ELISA and immunoblot. The serological study disclosed the presence of antibodies to both BDV-p24 and -p40 in the horses (20%) and sheep (25%), whereas no apparent positive reaction was detected either in cattle or rodents. The results suggested that BDV is prevalent in horses and sheep in the district investigated.

Molecular evidence for the presence of new Babesia species in feral raccoons (Procyon lotor) in Hokkaido, Japan.

We recently reported that feral raccoons (Procyon lotor) with splenomegaly native to Japan were carriers of a Babesia microti-like parasite identical to that found in the United States, which was likely introduced to Japan from North America via raccoons imported as pets. Thus, we attempted extensive molecular survey for piroplasma infections of feral raccoon with normal spleen in Hokkaido, Japan using nested PCR that target broadly to 18S ribosomal RNA gene (SSU-rDNA) of all the parasites in the genus Babesia, Theileria, Cytauxzoon and B. microti group. Of the 348 raccoon samples analyzed, 9 gave positive signals. Cloning and phylogenetic analysis on SSU-rDNA sequences revealed that six of nine positives were found to be infected with Babesia and the remaining three with previously unreported Sarcocystis. Babesia sequences were further separated into two distantly related groups, those that reside in a novel phylogenetic group were consisted solely of four parasites found in this study, while those which included one identical sequence found in the three of our specimens were assembled together with both Babesia parasites of ticks in Japan and of raccoons in U.S. These results may indicate that not only a B. microti-like parasite but also at least two yet undescribed Babesia species are being established in their new life cycles in the feral raccoon populations in Japan.

Echinococcus species from red foxes, corsac foxes, and wolves in Mongolia.

The small intestines of 420 wild canids (111 corsac foxes, 191 red foxes and 118 wolves) from Mongolia, were examined for adult worms of the genus Echinococcus. The Mongolian genotype of Echinococcus multilocularis was found in fifteen red foxes and four wolves, whereas two genotypes (G6/7 and G10) of Echinococcus canadensis were found in two and three wolves, respectively. No adult Echinococcus worms were found in the corsac foxes examined. The genotypes of E. multilocularis and E. canadensis are discussed in terms of host specificity and distribution in Mongolia. The importance of wolves in the completion of the life cycle of Echinococcus spp. is also discussed.

Antibodies to Flaviviruses in Wild Ducks Captured in Hokkaido, Japan: Risk Assessment of Invasive Flaviviruses

Recently, the distribution of Japanese encephalitis virus (JEV) and West Nile virus (WNV) has expanded into new territories. The invasion of WNV into Japan is of great concern. The migration of birds is suggested to be involved in the expanded distribution of these flaviviruses. In this study, 92 wild ducks--20 Anas poecilorhyncha (migratory breeders), 50 Anas platyrhynchos (undetermined), 16 Anas acuta (winter visitors), and 6 Anas penelope (winter visitors)--were captured in autumn of 2005 and 2006, in the central part of Hokkaido, a low JEV activity area. A seroepidemiologic analysis of flavivirus infections was conducted with 90% and 50% focus reduction neutralization tests (FRNT(90) and FRNT(50)). Of the 92 serum samples, 1 (1.1%) and 5 (5.4%) tested positive for WNV-specific and JEV-specific antibodies, respectively, in the FRNT(90), and 61 (66.3%) and 79 (85.9%) tested positive for WNV and JEV, respectively, in the FRNT(50). These results indicate that wild ducks in this study had been exposed to flaviviruses. The results together with the recognized distribution of flaviviruses and migratory routes of individual duck species strongly suggested that the birds captured in this study had been exposed to flaviviruses, including WNV, on the flyway, not in Hokkaido.

Parasitic helminths from feral raccoons (Procyon lotor) in Japan

SummaryAn epidemiological survey of 1688 free-ranging raccoons (Procyon lotor) captured on the Japanese main islands of Hokkaido, Honshu and Kyushu was undertaken to determine whether Baylisascaris procyonis, which provokes fatal neurological larva migrans was present; however, the worm was not detected in any of these individuals. A helminthological investigation was carried out on 229 of the captured racoons and the following worms obtained: Toxocara tanuki, Porrocaecum sp., Molineus legerae, Ancylostoma kushimaense, Aonchotheca putorii, Centrorhynchus sp., Centrorhynchus bazaleticus, C. elongatum, Plagiorhynchidae gen sp., Hemiechinosoma sp., Metagonimus takahashii, M. miyatai, Euparyphium sp., Plagiorchis muris, Brachylaima sp., and Taenia hydatigena. These were the first records of Porrocaecum sp., M. miyatai, Brachylaima sp. and T. hydatigena obtained from Japanese feral raccoons. Scanning electron microscopic and/or molecular analyses were performed for both T. tanuki and T. hydatigena as these helminths both have a zoonotic counterpart amongst their families.

Detection of the virulent Marek’s disease virus genome from feather tips of wild geese in Japan and the Far East region of Russia

SummaryMarek’s disease (MD) virus (MDV) is known to cause malignant lymphomas in chickens. In 2001, we first reported an MD case in a white-fronted goose (Anser albifrons) in Japan. Therefore, the prevalence of MDV in the wild geese was surveyed by nested PCR using feather-tip samples in Japan and the Far East region of Russia, breeding habitats of geese migrating to Japan. MDV was detected in about 30% of analyzed white-fronted geese. Furthermore, by nucleotide sequence analysis, we confirmed that this MDV shows high homology to very virulent MDV, suggesting that highly virulent MDV is widespread in white-fronted geese migrating between Japan and Far East region of Russia.

Borna disease virus RNA detected in Japanese macaques (Macaca fuscata)

We have examined the seroprevalence of BDV in wild Japanese macaques (Macaca fuscata) in the peninsula (Chiba prefecture), Japan. Serum samples from macaques were examined by the ELISA, Western blot and immunofluorescence assays to detect the presence of serum antibodies that react specifically to BDV antigens. Among 49 investigated individuals, 6 (12.2%) showed positive reaction to BDV antigens. RT-PCR studies detected BDV sequences in brain tissue of one case among four seropositive cases examined. Sequence analysis revealed a high degree of genetic conservation between BDV sequences derived from Japanese macaques and those documented for other animal species. Nevertheless, phylogenetic analysis revealed unique differences between macaque and other species derived BDV sequences.

Particle-Induced X-ray Emission Analysis of Elements in Plasma from Wild and Captive Sea Turtles (Eretmochelys imbricata, Chelonia mydas, and Caretta caretta) in Okinawa, Japan

The aim of this study was to evaluate the reliability of direct determination of trace and major element concentrations in plasma samples from wild (six hawksbill, nine green, and nine loggerhead) and captive sea turtles (25 howksbill, five green, and three loggerhead) in Okinawa, Japan. The particle induced X-ray emission method allowed detection of 23 trace and major elements (Al, As, Br, Ca, Cl, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Ni, P, Pb, S, Se, Si, Sr, Ti, Y, and Zn). The wild sea turtles were found to have high concentrations of As and Pb in plasma compared with captive, but there were no significant changes in the Al and Hg concentrations. Loggerhead sea turtles were found to have significantly higher accumulation of As and Pb in plasma in comparison to other species. These findings may be useful when adjusting environmental and species-related factors in severely polluted marine ecosystems. Our results indicate that measuring the plasma As and Pb concentrations in wild sea turtles might be of help to assess the level of pollution in marine ecosystems, keeping in mind that loggerhead sea turtles had been shown to have higher levels of As and Pb in plasma.

Epidemiology, histpathology, and muscle distribution of Trichinella T9 in feral raccoons (Procyon lotor) and wildlife of Japan

The prevalences of Trichinella T9 in trapped raccoons (Procyon lotor) and several other potential mammalian reservoirs in Hokkaido, Wakayama, and Nagasaki Prefectures were investigated. Muscle samples were collected from 2003 to 2006 from 1,080 raccoons, 113 raccoon dogs including 2 species (Nyctereutes procyonoides albus and N. p. viverrinus), 41 wild boars (Sus scrofa leucomystax), 14 martens (Martes melampus), 10 badgers (Meles meles), 5 Siberian weasels (Martes sibirica coreana), 7 mink (Mustela vison), and 1 red fox (Vulpes vulpes japonica). The samples were digested, and the prevalence and mean intensity of infection with the Trichinella muscle larvae were determined. The prevalence and intensity of the muscle larvae were 0.9% and 93.3 larvae/g (range 0.4–201.8) in raccoons, and 1.6% and 61.6 larvae/g in raccoon dogs, respectively. The infected animals were captured in different areas in Hokkaido Prefecture. These results confirmed that raccoons, which have been introduced from North America since the 1970s, are involved in the sylvatic cycle of Trichinella in Japan. In raccoons, the muscle density of Trichinella T9 larvae was highest in the tongue, and larvae were not found in the heart muscle or diaphragm. This is the first report of Trichinella T9 infection of feral raccoons in Japan.

Surveillance of Marek’s disease virus in migratory and sedentary birds in Hokkaido, Japan

Mareks disease virus serotype 1 (MDV-1) strains cause malignant lymphoma in chickens. MDV-1 has been previously reported to be widespread in white-fronted geese (Anser albifrons); however, the prevalence of MDV-1 in other wild birds has not been determined. In this study, we investigated the prevalence of MDV-1 in various wild birds in Hokkaido, Japan. The MDV-1 genome was widespread in geese and ducks, but was not detected in other birds. MDV-1 was detected in both sedentary and migratory species. These results suggest that, in Japan, MDV-1 is widespread in wild goose and duck populations, and that resident ducks may be significant carriers and reservoirs of MDV-1.