Self-assembled raccoon dog parvovirus VP2 protein confers immunity against RDPV disease in raccoon dogs: in vitro and in vivo studies.

BACKGROUND: Raccoon dog parvovirus (RDPV) causes acute infectious diseases in raccoon dogs and may cause death in severe cases. The current treatment strategy relies on the extensive usage of classical inactivated vaccine which is marred by large doses, short immunization cycles and safety concerns. METHODS: The present study aimed at optimization of RDPV VP2 gene, subcloning the gene into plasmid pET30a, and its subsequent transfer to Escherichia coli with trigger factor 16 for co-expression. The protein thus expressed was purified with ammonium sulfate precipitation, hydrophobic chromatography, and endotoxin extraction procedures. VLPs were examined by transmission electron microscopy, dynamic light scattering, and the efficacy of VLPs vaccine was tested in vivo. RESULTS: Results indicated that RDPV VP2 protein could be expressed soluble. Transmission electron microscopy and dynamic light scattering results indicated that RDPV VP2 self-assembled into VLPs. Hemagglutination inhibition antibody titers elicited by Al(OH)3 adjuvanted RDPV VLPs were comparable with RDPV inactivated vaccines, and the viral loads in the blood of the struck raccoon dogs were greatly reduced. Hematoxylin and eosin and Immunohistochemical results indicated that RDPV VLPs vaccine could protect raccoon dogs against RDPV infections. CONCLUSIONS: These results suggest that RDPV VLPs can become a potential vaccine candidate for RDPV therapy.

Detection of antibodies against Japanese encephalitis virus in raccoons, raccoon dogs and wild boars in Japan.

Japanese encephalitis virus (JEV) infects numerous animal species including humans, horses and pigs. In this study, antibodies against JEV in feral raccoons (Procyon lotor), wild boars (Sus scrofa) and raccoon dogs (Nyctereutes procyonoides) in Japan were examined. The results showed that 40.7% (22 out of 54), 64.5% (40 out of 62), 69.1% (47 out of 68) and 0% (0 out of 20) of raccoons in Hyogo, Osaka, Wakayama and Hokkaido, respectively, had virus-neutralizing antibodies against JEV. In addition, 83.3% (30 out of 36) of wild boars and 63.2% (12 out of 19) of raccoon dogs in Wakayama were seropositive for JEV. There were no significant differences in seroprevalence of JEV between males and females or between adults and juveniles in these wild animals. JEV seroprevalence was compared between 37 raccoons and 30 wild boars captured in a limited period (November 2007 to February 2008), and we found that wild boars (86.7%) were significantly more seropositive for JEV antibody than raccoons (59.5%). In conclusion, JEV was prevalent in wild mammals, indicating that the possibility of JEV infection in humans may still be high in Japan. In addition, these wild animals may be good sentinels to estimate JEV infection risk in residents, as they live near humans and are not vaccinated.

Molecular and serological surveillance of Hepatitis E virus in wild and domestic carnivores in Brandenburg, Germany.

Hepatitis E virus (HEV) is a zoonotic virus which circulates in pigs and wild boars as main reservoir species. To reveal the infection rate in carnivores, we have carried out a monitoring study of raccoons, raccoon dogs, dogs and cats sampled in Brandenburg, Germany. In summary, 53.8% (43 of 80) of the raccoons, 34.3% (25 of 73) of the raccoon dogs, 56.6% (47 of 83) of dogs and 32.3% (21 of 65) of cats were tested positive for HEV-specific antibodies. No viral RNA could be detected. This first description of anti-HEV antibodies in raccoons and raccoon dogs worldwide and in dogs and cats in Germany highlights the natural host range expansion of HEV.

Cross reactive antigenicity in orally vaccinated foxes and raccoon dogs against European Bat Lyssavirus type 1 and 2.

For the first time, the effectiveness of oral rabies vaccines against European Bat Lyssaviruses Type 1 (EBLV-1) and Type 2 (EBLV-2) by means of cross-neutralization assays was investigated. Sera from orally vaccinated red foxes (Vulpes vulpes) and raccoon dogs (Nyctereutes procyonoides) with the Street Alabama Dufferin (SAD) B19 and SAD P5/88 live-modified vaccine viruses were used to study the cross reactive antigenicity against CVS-11 (genotype 1), EBLV-1 (genotype 5) and EBLV-2 (genotype 6). For comparison, similar crossneutralization assays with sera from EBLV-1 and EBLV-2 infected ferrets (Mustela putorius furo) and/or foxes were conducted. Sera from animals vaccinated with the two oral rabies vaccines were reactive against CVS-11 (homologous virus), EBLV-1 and EBLV-2 (heterologous virus). There was a positive relationship among the virus neutralising antibody titres (VNA); high VNA titres against CVS-11 also resulted in high VNA titres against each EBLV, whereas in general, the VNA-titres obtained with homologous virus were statistically higher than those with the heterologous virus except for SAD P5/88 vaccinated raccoon dogs. No significant difference was found between EBLV-1 and EBLV-2 VNA titres. A similar trend was observed when the results of the cross-neutralization data of the foxes and ferrets inoculated i.m. with EBLV-1 and/or EBLV-2 was analysed. Based on the similarity of the EBLV-VNA titres obtained in our study questions were raised on whether the genetic distance of genotype 5 & 6 within phylogroup 1 really does reflect their antigenetic characteristics or whether this is a feature of attenuated live vaccine viruses. This broad cross protection, however, demonstrated that the representatives of attenuated SAD strains of oral rabies vaccines currently used in Germany are most likely able to protect the reservoir species, red fox and raccoon dog, against EBLV-1 and EBLV-2 infection.

Raccoon dog rabies surveillance and post-vaccination monitoring in Lithuania 2006 to 2010.

BACKGROUND: Oral rabies vaccination (ORV) in rabies infected regions should target the primary rabies vector species, which in Lithuania includes raccoon dogs as well as red foxes. Specific investigations on ORV in raccoon dogs are needed e.g. evaluation of vaccine effectiveness under field conditions. The objective of the current study was to investigate the efficacy of the ORV programme 2006-2010 in Lithuania by examining the number of rabies cases and estimating the prevalences of a tetracycline biomarker (TTC) and rabies virus antibodies in raccoon dogs. METHODS: From 2006 to 2010, 12.5 million rabies vaccine-baits were distributed by aircraft. Baiting occurred twice per year (spring and autumn), targeting raccoon dogs and red foxes in a 63,000 km2 area of Lithuania. The mandibles of raccoon dogs found dead or killed in the vaccination area were analyzed by fluorescence microscopy for the presence of the TTC. Rabies virus sera neutralizing anti-glycoprotein antibody titres were determined using an indirect ELISA method and seroconversion (> 0.5 EU/ml) rates were estimated. RESULTS: During the study period, 51.5% of raccoon dog mandibles were positive for TTC. 1688 of 3260 tested adults and 69 of 175 tested cubs were TTC positive. Forty-seven percent of raccoon dog serum samples were positive for rabies virus antibodies. 302 of 621 investigated adults and 33 of 95 investigated cubs were seropositive. In the same time 302 of 684 and 43 of 124 tested samples were TTC and ELISA positive in spring; whereas 1455 of 2751 and 292 of 592 tested samples were TTC and ELISA positive in autumn. There was a positive correlation between the number of TTC and antibody positive animals for both adult and cub groups. CONCLUSIONS: ORV was effective in reducing the prevalence of rabies in the raccoon dog population in Lithuania. The prevalence of rabies cases in raccoon dogs in Lithuania decreased from 60.7% in 2006-2007 to 6.5% in 2009-2010.