Rabies immune status of raccoon dogs residing in areas where rabies bait vaccine has been distributed

Since 2000, large amounts of rabies bait vaccine have been distributed in two provinces where raccoon dog-mediated rabies has occurred. A total of 146 raccoon dogs were caught in Gangwon and Gyeonggi Provinces from January 2017 to June 2018, and raccoon dog blood samples were collected. Of the 146 raccoon dogs, 13.7% (20/146) had rabies antibodies. In Gyeonggi and Gangwon provinces, the rate of rabies antibody was 8.5% (5/59) and 17.2% (15/87), respectively. Considering these results, it would be desirable to improve the distribution method or use a new bait vaccine to prevent animal rabies in South Korea.

Detection of viral infections in wild Korean raccoon dogs (Nyctereutes procyonoides koreensis)

Wild raccoon dogs (Nyctereutes procyonoides koreensis) may play a role transmitting several pathogens to humans and pet animals. Information concerning the incidence of rabies, canine distemper virus (CDV), canine parvovirus (CPV), canine adenovirus type 2 (CAdV-2), canine parainfluenza virus type 5 (CPIV-5), and canine herpesvirus (CHV) is needed in wild raccoon dogs. In total, 62 brain samples of raccoon dogs were examined for rabies virus (RABV) and CDV, and 49 lung samples were screened for CDV, CAdV-2, CPIV-5, and CHV. No RABV, CAdV-2, CPIV-5, or CHV was identified, but nine CDV antigens (8.1%, 9/111) were detected. Moreover, 174 serum samples from wild raccoon dogs were screened for antibodies against the five major viral pathogens. The overall serosurveillance against CDV, CPV, CAdV-2, CPIV-5, and CHV in wild raccoon dogs was 60.3%, 52.9%, 59.8%, 23.6%, and 10.3%, respectively. Comparisons of the sero-surveillance of the five pathogens showed that raccoon dogs of Gyeonggi province have slightly higher sero-positive rates against CDV, CPV, and CHV than those of Gangwon province. These results indicate high incidences of CDV, CPV, and CAdV-2 in wild raccoon dogs of two Korean provinces and a latent risk of pathogen transmission to companion and domestic animals.

Safety and immunogenicity of recombinant rabies virus (ERAGS) in mice and raccoon dogs

PURPOSE: The development of a genetically modified live rabies vaccine applicable to wild raccoon dogs is necessary for the eradication of rabies in Korea. Thus, we constructed a recombinant rabies virus (RABV) called the ERAGS strain, using a reverse genetic system and evaluated its safety and efficacy in mice and its safety and immunogenicity in raccoon dogs. MATERIALS AND METHODS: ERAGS, which has Asn194Ser and Arg333Glu substitutions in the glycoprotein, was constructed using site-directed mutagenesis. Mice were inoculated with the ERAGS strain (either 10(5.0) or 10(7.0) FAID(50)/mL) via intramuscular (IM) or intracranial injections and then challenged with a virulent RABV. Raccoon dogs were administered the ERAGS strain (10(8.0) FAID(50)/mL) either orally or via the IM route and the immunogenicity of the strain was evaluated using fluorescent antibody virus neutralization tests. RESULTS: The ERAGS strain inoculated into murine neuroblastoma cells reached 10(7.8) FAID(50)/mL at 96-hour post-inoculation. The virus was not pathogenic and induced complete protection from virulent RABV in immunized 4- and 6-week-old mice. Korean raccoon dogs immunized with the ERAGS strain via IM or oral route were also safe from the virus and developed high titer levels (26.4-32.8 IU/mL) of virus-neutralizing antibody (VNA) at 4 weeks post-inoculation. CONCLUSION: The ERAGS RABV strain was effectively protective against rabies in mice and produced a high VNA titer in raccoon dogs.

Application of recombinant adenoviruses expressing glycoprotein or nucleoprotein of rabies virus to Korean raccoon dogs

PURPOSE: A new rabies vaccine for animals, including raccoon dogs, in Korea is needed to eradicate rabies infection. In this study, we constructed two recombinant adenoviruses expressing the glycoprotein or nucleoprotein of the rabies virus (RABV). We then investigated the safety and immunogenicity of these strains in raccoon dogs, depending on inoculation route. MATERIALS AND METHODS: Recombinant adenoviruses expressing the glycoprotein (Ad-0910G) or nucleoprotein (Ad-0910N) of rabies were constructed in 293A cells using an adenoviral system. One-year-old raccoon dogs underwent intramuscular (IM) inoculation or oral administration of the recombinant Ad-0910G and Ad-0910N. Clinical symptoms were observed and virus-neutralizing antibodies (VNA) against RABV were measured at 0, 2, 4, and 6 weeks after the immunization. Raccoons were considered positive if VNA titers were > or = 0.1 IU/mL. RESULTS: Raccoon dogs inoculated with the combined Ad-0910G and Ad-0910N virus via the IM route did not exhibit any clinical sign of rabies during the observation period. All raccoon dogs (n = 7) immunized IM had high VNA titers, ranging from 0.17 to 41.6 IU/mL at 2 weeks after inoculation, but 70% (7/10) of raccoon dogs administered viruses via the oral route responded by 6 weeks after administration against RABV. CONCLUSION: Raccoon dogs inoculated with Ad-0910G and Ad-0910N viruses showed no adverse effects. Immunization with the combined Ad-0910G and Ad-0910N strains may play an important role in inducing VNA against RABV in raccoon dogs.

Safety and Immunogenicity of a Recombinant Rabies Virus Strain (ERAG3G) in Korean Raccoon Dogs

A new alternative rabies bait vaccine strain named ERAG3G, which is applicable to wild animals, was developed to eliminate rabies in South Korea. In this study, the safety and immunogenicity of the strain was evaluated in Korean raccoon dogs. The ERAG3G was propagated in BHK/T7-9 cells. Korean raccoon dogs were administered ERAG3G (1 ml, 10(8.0) FAID50/ml) orally or intramuscularly to evaluate its safety and immunogenicity. The raccoon dogs were observed for 70 days after administration, and immunogenicity was measured using a fluorescent antibody virus neutralization test. The ERAG3G strain was not pathogenic to Korean raccoon dogs immunized via the intramuscular or oral route. Raccoon dogs administered the candidate vaccine via the oral route developed high virus neutralizing antibody (VNA) titers ranging from 13.7 to 41.6 IU/ml 70 days post administration. Raccoon dogs inoculated intramuscularly with the ERAG3G strain developed moderate VNA titers ranging from 0.5 to 13.7 IU/ml. These findings suggest that the ERAG3G strain is safe and induces a protective immune response in raccoon dogs.

Seroepidemiological Survey of Aujeszky's Disease Virus in Wild Boar (Sus scrofa) and Raccoon Dogs (Nyctereutes procyonoides koreensis) in Korea

Aujeszky's disease caused by Aujeszky's disease virus (ADV) is one of the most important diseases in the pig industry. In this study, we conducted a seroepidemiological survey of ADV in wild boars and raccoon dogs in South Korea. In total, 217 wild boar sera collected between March and August 2013, and 96 raccoon dogs between 2011 and 2012 were screened for the presence of antibodies against ADV. The sero-positive rates in wild boars and raccoon dogs tested for ADV were found to be 3.55% (8/225) and 0% (0/96), respectively. The presence of virus neutralization antibody titer against ADV means that small number of wild boars was infected with ADV and AD may be circulated continuously in Korean wild boar populations, and that wild boars may act as a potential reservoir of ADV. Therefore, to achieve the declaration of AD free, effective preventive measures to block transmission of AD should be taken to the wild boars.

Strategic model of national rabies control in Korea

Rabies is an important zoonosis in the public and veterinary healthy arenas. This article provides information on the situation of current rabies outbreak, analyzes the current national rabies control system, reviews the weaknesses of the national rabies control strategy, and identifies an appropriate solution to manage the current situation. Current rabies outbreak was shown to be present from rural areas to urban regions. Moreover, the situation worldwide demonstrates that each nation struggles to prevent or control rabies. Proper application and execution of the rabies control program require the overcoming of existing weaknesses. Bait vaccines and other complex programs are suggested to prevent rabies transmission or infection. Acceleration of the rabies control strategy also requires supplementation of current policy and of public information. In addition, these prevention strategies should be executed over a mid- to long-term period to control rabies.

Serologic Survey of Rabies Virus, Canine Distemper Virus and Parvovirus in Wild Raccoon Dogs (Nyctereutes procyonoides koreensis) in Korea

Oral rabies vaccination (ORV) program for the wild animals in rabies risk regions of Korea has been conducted since 2000. Evaluation of ORV program under field condition and information concerning the incidence of exposure to canine distemper and canine parvovirus (CPV) are needed in wild raccoon dogs (Nyctereutes procyonoides koreensis). Ninety four sera of wild raccoon dogs were screened for antibodies against rabies, canine distemper virus (CDV) and CPV in Korea. The overall prevalence of antibodies against rabies virus (RABV), CDV and CPV in wild raccoon dogs was 35.1%, 89.4% and 24.5%, respectively. Comparisons of sero-prevalences of RABV, CDV and CPV were assayed in two regions (Gyeonggi-do and Gangwon-do). The Gyeonggi-do (36.4%) showed higher sero-positive rate against CPV than Gangwon-do (20.8%). In contrast, Gangwon-do (41.7% and 97.2%) showed higher sero-positive rates against RABV and CDV than Gyeonggi-do (13.6% and 63.6%). These results indicate that there was severe circulation of CDV and CPV among wild raccoon dogs in the two regions of Korea. Furthermore, raccoon dogs showing a protective antibody titer (0.5 IU/ml) were 15.9%, suggesting that new rabies control program such as trap-vaccination-release (TVR) should be launched urgently in rabies risk regions.

Epidemiological Characteristics of Rabies in South Korea from January 2004 to March 2011

Over the seven years from January 2004 to March 2011, 105 rabies cases in three different animal species and one case in human were recorded in South Korea. Forty three (40.6%) cattle and 33 (31.1%) dogs, 29 (27.4%) raccoon dogs were affected and one (0.9%) death in human was reported. The highest annual incidence of rabies was recorded with 27 cases in 2004, and then decreased to a median of 14 cases per year. Eighty cases (76.2%) occurred in Gangwon and 24 cases (22.9%) in Gyeonggi and one case in Seoul Province. All rabies cases occurred in the northern part of the country, namely, Seoul, Gyeonggi and Gangwon Provinces. Since 2007, rabies cases were not reported in Gyeonggi Province, but continued to occur and move eastward in Gangwon Province. The monthly distribution of animal rabies during the seven year period peaked in January, and the incidence was the highest during winter, from December to February, and the least common in summer, from June to September. The epidemiological study indicated that preventive measures including distribution of bait vaccine for the control of rabies in wild animals was helpful to a substantial decrease in number of rabies cases in South Korea.

Outbreaks and Control of Animal Rabies in Korea

Since rabies virus infection is fatal for both human and animals, the protective immunization by vaccines against animals is a critical importance for disease prevention and control. In Korea, recurrence of sylvatic rabies was reported in Gangwon province, which is the northern border area in 1993. During the years of 1994-2009, 417 animal rabies cases were registered in Gangwon and Gyeonggi provinces. The national animal rabies eradication program has performed to reduce rabies outbreaks by annual vaccination of dogs and cattle since 1995, and the oral vaccination of raccoon dogs with annual vaccinia-rabies glycoprotein (V-RG) bait vaccine. Additionally, serological surveillance on domestic animals has been executed since 1999 to monitor the anti-rabies antibody titers from Gangwon and Gyeonggi provinces where the vaccination campaign has been implemented.

Arthrostoma miyazakiense (Nematoda: Ancylostomatidae) infection in raccoon dogs of Korea and experimental transmission to dogs

Arthrostoma miyazakiense (Nematoda: Ancylostomatidae) is a hookworm species reported from the small intestines of raccoon dogs (Nyctereutes procyonoides) in Japan. Five Korean raccoon dogs (N. procyonoides koreensis) caught from 2002 to 2005 in Jeollanam-do (Province), a southeastern area of South Korea, contained helminth eggs belonging to 4 genera (roundworm, hookworm, whipworm, and Capillaria spp.) and cysts of Giardia sp. in their feces. Necropsy findings of 1 raccoon dog revealed a large number of adult hookworms in the duodenum. These hookworms were identified as Arthrostoma miyazakiense based on the 10 articulated plates observed in the buccal capsule and the presence of right-sided prevulval papillae. Eggs of A. miyazakiense were 60-65 x 35-40 micrometer (av. 62.5 x 35 micrometer), and were morphologically indistinguishable from those of Ancylostoma caninum. The eggs were cultured to infective 2nd stage larvae via charcoal culture, and 100 infective larvae were used to experimentally infect each of 3 mixed-bred puppies. All puppies harbored hookworm eggs in their feces on the 12th day after infection. This is the first report thus far concerning A. miyazakiense infections in raccoon dogs in Korea, and the first such report outside of Japan.