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.     

Maternal immunity against rabies in raccoon dogs.

The objective of the study was to examine possible maternally transferred antibodies (maAb) against rabies in raccoon dogs. Ten cubs born from a rabies-immune animal were bled on days 31, 36, 43, 50, 57 and 64 post partum. The geometric mean titres of the cubs were 1.19, 1.18, 0.45, 0.25, 0.25 and 0.16 IU/ml, respectively. Up to 36 days post partum maAb were detected in all cubs at levels > or = 0.5 IU/ml and at day 56 post partum all animals had maAb levels < 0.5 IU/ml. Based on the results of this study, it is suggested that vaccine baits should not be distributed before July if the vaccination campaign is aimed at immunizing young raccoon dogs as well.     

外源褪黑激素对乌苏里貉冬皮成熟日期的影响

在１９９３年—１９９５年期间，进行了外源褪黑激素对乌苏里貉冬皮成熟日期影响的研究。对４９６只乌苏里貉进行了皮下埋植褪黑激素植入物的试验，所用的植入物均为东北林业大学野生动物繁殖实验室研制的新型褪黑激素植入物。试验结果表明，在夏至前后期间用适量的外源褪黑激素处理，有促进乌苏里貉冬皮早熟的效果。成年母貉在６月４日、１５日、２２日埋植含１０．６ｍｇ，１２ｍｇ或１５ｍｇ褪黑激素的植入物，冬皮成熟日期提前到９月２５日，１０月４和８日，比正常提前６周—８周。当年生幼貉在７月６日、１１日期间埋植含８．６ｍｇ，１０ｍｇ，１２ｍｇ褪黑激激素植入物，冬皮成熟日期提前到１０月１５和２８日。     

Rabies, an emerging disease in Korea

Since the first rabies case was reported in a dog in 1907, the disease was enzootic up to 1975 in Korea. After a steady decrease in the number of rabies cases from 1976 to 1984, no case was reported for 8 years from 1985 to 1992. Then, a resurgence of the disease was noted in 1993, and a continuous increase of rabies cases was observed during the following years. This report provides information on rabies in South Korea during the reemerging period 1993-2003. A total of 364 rabies cases in five different animal species and five deaths in human beings as a result of rabies were reported. Cattle and dogs accounted for 46.4% and 40.4% of total animal cases, respectively, and raccoon dogs commanded an overwhelming majority (44/48) of rabies cases in wildlife animal species. All animal and human rabies cases occurred only in two provinces, Gyeonggi and Gangwon; majority of them in two counties of Gyeonggi and one county of Gangwon province that border the demilitarized zone. From the three counties, the disease continued to expand to the other areas of the two provinces. The average monthly frequency of animal rabies cases during the 11-year period peaked in January, and the incidence was highest during winter. There were three major rabies outbreaks in animals and the number of animal rabies cases increased with time. Data indicate that the temporal patterns were attributable to the ethology of raccoon dogs in the areas of outbreak.     

An epidemic of sylvatic rabies in Finland--descriptive epidemiology and results of oral vaccination.

When rabies reappeared in Finland in April 1988, the country had been rabies free since 1959. Soon a picture of sylvatic rabies become evident, its main vector and victim being the raccoon dog (Nyctereutes procyonoides). Between 8 April 1988 and 16 February 1989, 66 virologically verified cases were recorded (48 raccoon dogs, 12 red foxes, 2 badgers, 2 cats, 1 dog and 1 dairy bull) in an area estimated at 1700 km2 in south-eastern Finland. The greatest distance between recorded cases was 67 km. A positive reaction with monoclonal antibody p-41 indicated that the virus was an arctic-type strain. A field trial on oral immunization of small predators was initiated in September 1988 using Tübingen fox baits according to the Bavarian model of bait distribution. Each bait contained 5*10(7) TCID50/ml modified live rabies virus (SAD-B19). The 6 months' surveillance indicate a seroconversion rate of 72% (N = 126) in the raccoon dog population, 67% (N = 56) in the red foxes and 13% (N = 16) in the badgers, when titers greater than or equal to 1.0 IU/ml are considered seropositive. In the whole follow-up period, no statistically significant difference could be detected between the raccoon dogs and red foxes in the rate of seroconversion or in the uptake of tetracycline from the baits. Notably high antibody levels were recorded in both raccoon dogs and red foxes within 4-5 months after vaccination. Of the seropositive animals, the proportion of animals with titers 3.0 IU/ml or greater was higher in raccoon dogs (73%) than in red foxes (51%) (x2 = 5.29, p less than 0.05). The trial shows that raccoon dogs can be immunized against rabies in the field with vaccine baits originally developed for controlling sylvatic rabies in foxes.     

Epidemiology of sarcoptic mange in free-ranging raccoon dogs (Nyctereutes procyonoides) in Yokohama,Japan

Free-ranging raccoon dogs (Nyctereutes procyonoides) from Nogeyama Zoological Gardens, Kanazawa Zoological Gardens, and Yokohama Zoological Gardens frequently rescued dogs having Sarcoptes scabiei infestation. However, the epidemiology of S. scabiei infestation has not yet been elucidated. In the present study, we investigated the epidemiology of S. scabiei infestation in raccoon dogs and its influence on the population of masked palm civets in Yokohama, Japan. We examined records of raccoon dog rescue between 1981 and 2010 and classified the dogs into the following 4 categories on the basis of the reason for rescue: dogs with S. scabiei infestation, scabies-infested dogs involved in car accidents, uninfested dogs involved in car accidents, and other reasons for rescue. We found that the number of dogs rescued due to car accidents and other reasons increased from 1989 onwards, and an S. scabiei outbreak was recorded since 1993. The infestation spread from the southern to the northern regions of Yokohama. The total number of raccoon dogs rescued annually peaked in 1995 and declined thereafter. The number of masked palm civets (Paguma larvata) rescued gradually increased with a decline in the number of raccoon dogs rescued. In the present study, we revealed the epidemiology of S. scabiei infestation in the raccoon dog. The outbreak might be induced by the increased population density, and the infestation spread immediately from the southern to the northern regions of Yokohama since 1993. Further, the population of masked palm civets may have increased due to the decrease in the population of the raccoon dog.     

Phylogenetic identification of Cystoisospora spp. from dogs, cats, and raccoon dogs in Japan

Cystoisospora spp. from feces in dogs, cats, and raccoon dogs were isolated, sequenced at the small subunit ribosomal RNA gene locus and compared to other Cystoisospora spp. Cystoisospora oocysts from dogs and raccoon dogs were morphologically similar with those of C. ohioensis, and cat isolates were similar with those of C. felis. The sequences from dogs and raccoon dogs, and cats have a homology with C. ohioensis and C. felis, respectively. Phylogenetic analysis of the DNA sequences showed that the dog and raccoon dog isolates were nested in a clade with other Cystoisospora spp. including C. ohioensis, C. belli, and C. orlovi. The cat isolate formed a sister group with C. felis that was a separate clade from the dog and raccoon dog group. We report sequence variation in these Cystoisospora sequences and have identified raccoon dogs as another carnivore host for Cystoisospora spp. infecting dogs.     

Histopathological comparison of pulmonary artery lesions between raccoon dogs (Nyctereutes procyonoides) and domestic dogs experimentally infected with Dirofilaria immitis

Five raccoon dogs (Nyctereutes procyonoides) and two domestic dogs (Canis familiaris) were subcutaneously infected with 100 infective larvae (L3) of Dirofilaria immitis. Two and five worms, respectively, were collected from two of three raccoon dogs. Villous endarteritis was found in the raccoon dog with five worms and two dogs at 116 days after infection. The number of recovered worms in the raccoon dogs was significantly smaller than that of the domestic dogs having 22 and 29 worms, while histopathological features and the severity of the lesions in the raccoon dogs were similar to those in the domestic dogs. The vascular lesions in two chronically-infected raccoon dogs turned into much severe at 565 and 590 days after inoculation.     

Detection of canine coronaviruses genotype I and II in raised Canidae animals in China

An RT-nPCR assay was used for testing fecal samples of dogs, foxes, raccoon dogs and minks for the presence of canine coronavirus (CCV). The animals were raised in homes, dog schools or farms. Seventy out of 81 healthy dog feces from three cities and 21 out of 48 diarrhea feces from pet dogs were positive for type II CCV. From a total of 61 healthy fox feces, 43 were positive for type II and 29 for type I CCV, out of which 25 were simultaneously positive for the two different genotypes. Among 24 raccoon dogs samples, 22 were CCV type II-positive, and from those 16 were additionally type I positive. No CCVs was detected from healthy mink feces. Sequence analysis found that ten type II CCVs fragments of M gene shared a high similarity with reference strain CCV 1-71 (96.5-99.5%), and four type I CCVs shared a high similarity (96.7%-98.1%) with a reported FCV-like CCV strain. The sequence of one particular M gene fragment was found to cluster between the type I and type II CCV branches in phylogenetic analysis, suggesting the existence of a novel strain. Our study confirmed that type II CCVs infection is very common in domestic dog, fox, and raccoon dog populations in China. This is also the first report on the co-existence of two CCV genotypes in healthy foxes and raccoon dogs.     

Altered expression of melanocortin-1 receptor (MC1R) in a yellow-coloured wild raccoon dog (Nyctereutes procyonoides)

Background – The melanocortin 1 receptor (MC1R) gene plays a key role in determining coat colour in mammals by controlling the proportion of eumelanin and pheomelanin granules. Wild raccoon dogs have a mixed coat colour, with black to brown and grey hairs. Hypothesis/Objectives – The study was performed to identify the cause of the variant yellow coat colour in a wild raccoon dog. Animals – A wild raccoon dog that showed coat colour change to yellow and four wild‐type raccoon dogs that showed normal coat colour were included. Methods – To identify the cause of the variant yellow coat colour, we examined the sequence of the MC1R gene and its expression at the mRNA and protein levels. Results – The coding region of the MC1R gene of this raccoon dog comprised 954 bp, the same as for wild‐type raccoon dogs and domestic dogs. By comparing the gene with that in the wild‐type raccoon dog, a 2 bp deletion was detected in the 5′‐untranslated region, positioned 152 bp upstream of the start codon. However, there was no significant difference in the mRNA expression level. The yellow raccoon dog revealed a significantly decreased MC1R protein level compared with the wild‐type raccoon dogs, indicating an increase in pheomelanin synthesis. Conclusions and clinical importance – These results suggest that the variant coat colour in the yellow raccoon dog was associated with decreased MC1R function.     

Missense polymorphisms in the MC1R gene of the dog,red fox,arctic fox and Chinese raccoon dog

Coat colour variation is determined by many genes, one of which is the melanocortin receptor type 1 (MC1R) gene. In this study, we examined the whole coding sequence of this gene in four species belonging to the Canidae family (dog, red fox, arctic fox and Chinese raccoon dog). Although the comparative analysis of the obtained nucleotide sequences revealed a high conservation, which varied between 97.9 and 99.1%, we altogether identified 22 SNPs (10 in dogs, six in farmed red foxes, two in wild red foxes, three in arctic foxes and one in Chinese raccoon dog). Among them, seven appeared to be novel: one silent in the dog, three missense and one silent in the red fox, one in the 3′‐flanking region in the arctic fox and one silent in the Chinese raccoon dog. In dogs and red foxes, the SNPs segregated as 10 and four haplotypes, respectively. Taking into consideration the published reports and results of this study, the highest number of missense polymorphisms was until now found in the dog (9) and red fox (7).     

The effect of short-term fasting on sleep in pigs

Trials were conducted with twelve piglets of the German Large White breed, intended for fattening. Their age was 56 +/- 2 days and their average weight was 21 +/- 3.7 kg. The piglets were studied for the effect of short fasting on the time and nature of sleep. After 18 hours of fasting (skipping the morning feeding), the piglets were fixed to obtain a combined record, including the electroencephalogram (EOG). This record was used for analyzing the time of waking and sleep, both the NREM stage and REM episodes. The same observations were performed in the piglets after feeding. The differences in the obtained data between the groups of animals were subjected to statistical evaluation. The fasting animals slept for about 15% of all the time under study and their sleep included short NREM periods interrupted by waking. No REM sleep was observed in the fasting piglets. After feeding the piglets slept significantly longer (p less than 0.01), more than half the period of study. Episodes of REM sleep occurred repeatedly in four animals. It is indicated by the results that fasting reduces the length of sleep and the nature of sleep.     

乌苏里貉生长发育规律研究及其生长曲线模型拟合

选取60只分窝乌苏里仔貉,按出生窝别、出生时间、性别、体重分为4组,生长期和冬毛期分别饲喂4种不同的试验E／粮,研究其生长发育规律,拟合其体重和体长生长模型。结果表明：乌苏里貉周平均日增重在8～12周龄和18～24周龄有2个高峰期（分别为40g／d和50g／d）,体长生长速度在9～14周龄和20～22周龄有2个高峰期（分别为0．3cm／d和0．2cm／d）;体重和体长适宜生长曲线方程分别为：Y=241．47＋42．242X＋19．041X^2-0．399X^3（R^2=0．994）,Y=9．517＋3．374X-0．067X^2（R^2=0．992）。     

Efficient distribution of oral vaccines examined by infrared triggered camera for advancing the control of raccoon dog rabies in South Korea

The field distribution of the oral rabies vaccine is effective in controlling the spread of rabies. The present study aimed to investigate efficient distribution locations based on the environment, contact rate, and consumption by target wildlife species in South Korea. The target species (Korean raccoon dogs, domestic dogs, and feral cats) accounted for 945 contacts (52.2%), in total 1,808 contacts. There were 863 (47.8%) contacts by non-target species. Raccoon dogs, a main reservoir of rabies in South Korea, had the highest contact rate (34.1%) among all species. The contact rate by target species was highest at riparian sites and bushy mountainous vegetation, where raccoon dogs are abundant. There was remarkable contact by raccoon dogs in mountainous areas below 150 m with bushy vegetation. Our results indicate that these locations are efficient areas for vaccine distribution, especially targeting the raccoon dog. Vaccines were continuously contacted with intervals ranging from one hour to one day. Vaccines at 94.4% of the distribution points were completely consumed within two weeks. The mean consumption rate was 95.2 ± 1.93% during the overall study period. These findings suggest that the oral rabies vaccine attracts wildlife including domestic dogs and feral cats. Our results suggest that low sections of mountainous areas with bushy vegetation and/or neighboring riparian areas are rich in target wildlife species (especially raccoon dogs) and are efficient locations for vaccine distribution to control rabies in South Korea.     

Parasitological survey on wild carnivora in north-western Tohoku, Japan.

In the winter of 1997-1998, we collected parasitological data from 60 wild carnivora in the north-western part of Tohoku region, Japan. These included 7 foxes (Vulpes vulpes japonica), 20 raccoon dogs (Nyctereutes procyonoides viverrinus), 29 martens (Martes melampus melampus), 3 weasels (two Mustela sibirica itatsi and one M. nivalis namiyei), and one Japanese badger (Meles meles anakuma). Roundworms (Toxocara canis in foxes and Toxocara tanuki in raccoon dogs), hookworms (Ancylostoma kusimaense and Arthrostoma miyazakiense) and Molineus sp. in the small intestine were the most prevalent in foxes and raccoon dogs. In martens, Aonchotheca putorii in the stomach, Concinnum ten in the pancreatic duct, Molineus sp. and Euryhelmis costaricensis in the small intestine were the most prevalent. Collected parasites include some new helminth species for this region or Japan; the strobilar stage of Taenia polyacantha from foxes, Pygidliopsis summa from a raccoon dog, Eucoleus aerophilus, A. putorii, and Soholiphyme baturini from martens.     

Epidemiological situation of rabies in Lithuania from 1990 to 2000

The epidemiological situation of rabies was investigated in Lithuania. Over the last decade, 2277 cases of rabies were registered among wild and domestic animals (mean number of cases per districts was 44). The highest distribution of rabies was found in the districts of Lazdijai and Utena (116 and 81 cases, respectively), and the lowest in the Svencioniai and Zarasai districts (one and eight cases, respectively). It was found that rabies among wildlife comprised 54% with the majority of cases being registered in foxes (626 cases, 27%) followed by raccoon dogs (470 cases, 21%). Within the last 3 years, cases of rabies among foxes and raccoon dogs increased significantly (three and six times, respectively), compared with the period from 1990 to 1997. Among domestic animals, 46% cases of rabies were registered, with cattle comprising 27%, and the cases among cats and dogs at 9 and 8%, respectively. During the period from 1993 to 1997 in Lithuania, 11,385 of humans were attacked by domestic and wild animals, and 21,173 humans were vaccinated against rabies for prophylactic reasons. Our survey has shown that, during the period from 1997 to 2000, the number of people attacked has increased drastically-31,348 (60%), but only 8021 (18%) of them were vaccinated.     

Immunolocalization of steroidogenic enzymes P450scc, 3betaHSD, and P450c17 in the ovaries of wild raccoon dogs (Nyctereutes procyonoides)

We investigated the distribution of 3 types of steroidogenic enzymes, P450scc, 3betaHSD, and P450c17, in wild raccoon dog ovaries by immunohistochemistry. Six pairs of ovaries were obtained from wild raccoon dogs between 2001 and 2003, with 3 of the 6 pairs of ovaries containing corpora lutea. P450scc, 3betaHSD, and P450c17 were localized in the granulosa and theca cells of these raccoon dogs. Furthermore, lutein cells were stained positively for P450scc and 3betaHSD in the pregnant and non-pregnant raccoon dogs. These results suggest that granulosa and theca cells may synthesize progesterone and androgens, which may play an important role in follicular development, and that lutein cells are a major source of progesterone in wild raccoon dogs.     

Effects of a dental food on plaque accumulation and gingival health in dogs

Recent studies have demonstrated that typical dry dog foods have significantly less efficacy in reducing accumulation of dental substrates compared to a specifically formulated and processed dental food. This study compared the effects of a typical dry food and a dental food on plaque accumulation and gingival inflammation in dogs during a 6-month period. Daily feeding of the dental food significantly reduced plaque and gingivitis by 39% and 36%, respectively, compared with daily feeding of the typical dry food. Feeding a food that decreases plaque accumulation and reduces gingivitis contributes to canine oral health maintenance.     

Molecular characterization of Korean rabies virus isolates

The nucleoprotein (N) and glycoprotein (G) of 11 Korean rabies virus (RABV) isolates collected from animals diagnosed with rabies between 2008 and 2009 were subjected to molecular and phylogenetic analyses. Six isolates originated from domestic animals (cattle and dogs) and five were obtained from wild free-ranging raccoon dogs. The similarities in the nucleotide sequences of the N gene among all Korean isolates ranged from 98.1 to 99.8%, while those of the G gene ranged from 97.9 to 99.3%. Based on the nucleotide analysis of the N and G genes, the Korean RABV isolates were confirmed as genotype I of Lyssavirus and classified into four distinct subgroups with high similarity. Phylogenetic analysis showed that the Korean isolates were most closely related to the non-Korean NeiMeng1025B and 857r strains, which were isolated from rabid raccoon dogs in Eastern China and Russia, respectively. These findings suggest that the Korean RABV isolates originated from a rabid raccoon dog in Northeastern Asia. Genetic analysis of the Korean RABV isolates revealed no substitutions at several antigenic sites, indicating that the isolates circulating in Korea may be pathogenic in several hosts.     

Predilection muscles and physical condition of raccoon dogs (Nyctereutes procyonoides) experimentally infected with Trichinella spiralis and Trichinella nativa

The predilection muscles of Trichinella spiralis and T. nativa were studied in 2 experimental groups of 6 raccoon dogs (Nyctereutes procyonoides), the third group serving as a control for clinical signs. The infection dose for both parasites was 1 larva/g body weight. After 12 weeks, the animals were euthanized and 13 sampling sites were analysed by the digestion method. Larvae were found in all sampled skeleton muscles of the infected animals, but not in the specimens from the heart or intestinal musculature. Both parasite species reproduced equally well in the raccoon dog. The median density of infection in positive tissues was 353 larvae per gram (lpg) with T. spiralis and 343 lpg with T. nativa. All the infected animals had the highest larvae numbers in the carpal flexors (M. flexor carpi ulnaris). Also tongue and eye muscles had high infection levels. There were no significant differences in the predilection sites between these 2 parasite species. Trichinellosis increased the relative amount of fat, but not the body weight in the captive raccoon dogs. Thus, Trichinella as a muscle parasite might have catabolic effect on these animals.