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.     

Helminth findings in indigenous raccoon dogs Nyctereutes procyonoides (Gray, 1843)

Internal organs of 74 racoon dogs originating from the eastern districts of the Federal Land Brandenburg were subjected to a complete helminthological dissection. In addition, samples of diaphragma muscles from 46 further animals were examined for Trichinella larvae. Altogether 3 trematode- (Alaria alata, Isthmiophora melis, Metorchis bilis), 3 cestode- (Mesocestoides sp., Echinococcus multilocularis, Taenia polyacantha) and 7 nematode species (Capillaria aerophila, C. plica, Trichinella spiralis, Uncinaria stenocephala, Molineus patens, Crenosoma vulpis, Toxocara canis) could be identified. Thereby, the racoon dog has a comparable helminth spectrum as well known in red foxes. Differences in the frequency of the occurrence of helminths in both hosts can be explained by different food preferences.     

Nematodes from raccoon dogs (Nyctereutes procyonoides viverrinus) introduced recently on Yakushima Island, Japan

Nematodes were collected from 14 raccoon dogs (Nyctereutes procyonoides viverrinus) on Yakushima Island, Kagoshima Prefecture (Kyushu), Japan, that were the progeny of recently introduced animals to this World Natural Heritage Area, probably within the last 2 decades. Seven nematode species (Toxocara tanuki, Ancylostoma kusimaense, Arthrostoma miyazakiense, Strongyloides planiceps, Trichuris vulpis, Gongylonema sp., and Dirofilaria immitis) were collected from the raccoon dogs. Two nematode species (Molineus legerae and Strongyloides martis) were collected from 2 Japanese weasels (Mustela itatsi) indigenous to this island that were killed by traffic accidents. Considering that foxes and other carnivores, except for weasels, dogs and cats, are not distributed on this island, most of soil-borne nematodes such as roundworms, hookworms, and threadworms in raccoon dogs should have been introduced by the original population from the mainland Japan, and the infection hence maintained at a high level by new generations. Recovery of the third-stage larvae of Gongylonema sp. from the esophagus of raccoon dogs was remarkably frequent (79%), suggesting that the animals might vigorously take insect hosts. Although S. martis have never been recorded from weasels in Japan until this study, this threadworm might be prevalent in a variety of mustelids in Eurasia.     

Juvenile bird acanthocephalans recovered incidentally from raccoon dogs (Nyctereutes procyonoides viverrinus) on Yakushima Island, Japan

Helminth parasites were collected from 14 raccoon dogs (Nyctereutes procyonoides viverrinus) and 2 Japanese weasels (Mustela itatsi sho) on Yakushima Island, Kagoshima Prefecture (Kyushu), Japan. In addition to trematodes and nematodes reported separately, everted cystacanths of 3 bird acanthocephalans (Mediorhynchus robustus in 5 animals, Porrorchis leibyi in 2 animals, and Sphaerirostris lanceoides in 1 animal) were collected from the raccoon dogs introduced recently on this World Natural Heritage Area. A cystacanth of P. leibyi was collected also from a weasel indigenous to this island that were killed by traffic accidents. Recovery of everted cystacanths of M. robustus from the intestine of raccoon dogs was remarkably frequent (36%), suggesting that this acanthocephalan should be highly prevalent in passerine hosts on Yakushima Island, and the animals might vigorously take insect hosts or paratenic hosts. Furthermore, the present report is the second on M. robustus after its first record in Japan (Aichi Prefecture, Honshu) as M. garruli from a Eurasian jay (Garrulus glandarius japonicus) by Yamaguti in 1939. Porrorchis leibyi has never been recorded in Japan.     

Radiographic evaluation of congenital vertebral anomalies in Korean raccoon dogs (Nyctereutes procyonoides koreensis)

BackgroundThe normal vertebral anatomy of Korean raccoon dogs and their variants require research attention as a prerequisite for identifying pathologies and anomalies.ObjectivesThis retrospective study aimed at describing the vertebral formula and congenital vertebral anomalies in Korean raccoon dogs (Nyctereutes procyonoides koreensis).MethodsRadiographs of 82 raccoon dogs (42 males, 40 females) acquired from May 2013 to June 2020 in the Gangwon Wildlife Medical Rescue Center were reviewed to evaluate the cervical, thoracic, and lumbar vertebrae of the spine.ResultsNormal morphology of all vertebrae was observed in 50 of the 82 raccoon dogs, and the vertebral formula was cervical 7, thoracic 13, and lumbar 7. Congenital vertebral anomalies were found in 32 raccoon dogs: transitional vertebrae (TV) in 31 and block vertebrae in 2. Two raccoon dogs had 2 types of vertebral anomalies: one had TV and block vertebra, and the other had 2 types of TV. Twenty-nine raccoon dogs had thoracolumbar TV (TTV) and 3 had lumbosacral TV. TTV was morphologically classified into 4 different types: unilateral extra-rib in 5 raccoon dogs, bilateral extra-ribs in 14, bilateral elongated transverse processes in 4, and an asymmetric mixed formation of extra-rib with elongated transverse process in 6.ConclusionsThis study showed that TTV is common in Korean raccoon dogs, and that the vertebral formula is relatively diverse. The bilateral extra-ribs type TTV is the most common variant, which is almost similar to normal rib to be confused the radiographic evaluation.     

Severe hydrocephalus in a raccoon dog (Nyctereutes procyonoides)

Hydrocephalus is one of the most common central nervous system malformations in domestic dogs, yet they are poorly documented and studied in wild carnivoran mammals. A pup of raccoon dog (Nyctereutes procyonoides) was rescued and brought to Wildlife Center. The pup showed generalized ataxia, a domed skull, and an open bregmatic fontanelle. Ultrasound and MRI showed severe enlargement of the lateral ventricle with the loss of septum pellucidum resulting in a single large ventricle and cervical syringohydromyelia. Although treatment was attempted, the animal was euthanized due to poor prognosis. At necropsy, macroscopic findings were identical to the diagnostic imaging, where marked enlargement of the calvarium, and attenuated gyri and sulci were observed. Finally, hydrocephalus was confirmed. Here, we describe a case of hydrocephalus in a raccoon dog (Nyctereutes procyonoides).     

Epidemiology of canine distemper virus in wild raccoon dogs (Nyctereutes procyonoides) from South Korea

Raccoon dogs (Nyctereutes procyonoides) are widespread and common in South Korea. In 2011, we obtained serum samples from 102 wild raccoon dogs to survey their exposure to canine distemper virus (CDV). Forty-five of the 102 animals (44.1%) were seropositive. Field cases of canine distemper in wild raccoon dogs from 2010 to 2011 were investigated. Fourteen cases of CDV infection were identified by a commercially available CDV antigen detection kit. These cases were used for virus isolation and molecular analysis. Sequence analysis of hemagglutinin genes indicated that all viruses isolated belonged to the Asia-2 genotype. H protein residues which are related to the receptor and host specificity (residues 530 and 549) were analyzed. A glutamic acid (E) residue is present at 530 in all isolates. At 549, a histidine (H) residue was found in five isolates and tyrosine (Y) residue was found in 6 isolates. Our study demonstrated that CDV infection was widespread in wild raccoon dogs in South Korea.     

Detection of antibodies against the rabies virus in Korean raccoon dogs (Nyctereutes procyonoides koreensis)

Rabies has been reported in dogs, cattle, and raccoon dogs in Korea, especially in the provinces of Gyeonggi and Gangwon. The aim of this study was to investigate the seroprevalence of the rabies in wild Korean raccoon dogs by using 50 blood samples collected in Gyeonggi and Gangwon provinces. Antibodies against rabies were measured by using a fluorescent antibody virus neutralization test. Of the 50 blood samples tested, 20 raccoon dogs (40%) tested positive. Seropositive animals were distributed in Paju, Yangpyeong, Goyang, Yangju, Yanggu, and Hoengseong cities.     

Effects of alprazolam on capture stress-related serum cortisol responses in Korean raccoon dogs (Nyctereutes procyonoides koreensis)

The purpose of this study was to evaluate the effect of alprazolam on the stress that Korean raccoon dogs (Nyctereutes procyonoides koreensis) may experience while caught in a live trap by measuring their serum cortisol response. The animals were placed in a live trap with or without being pretreated with oral doses of alprazolam. In both groups, pre-trap blood samples were initially collected without anesthesia before the animals were positioned in the live trap; then post-trap blood samples were collected after the animals had remained in the live trap for 2 h. Changes in cortisol levels were observed using a chemiluminescent immunoassay. The level of cortisol increased in the control group and decreased in the alprazolam-pretreatment group (p < 0.05). In this study, we demonstrated that alprazolam pretreatment reduced stress during live trap capture.     

Clinical features of experimental trichinellosis in the raccoon dog (Nyctereutes procyonoides)

Three groups of six raccoon dogs (Nyctereutes procyonoides) were provided for the experiment: the first group was infected with pig-origin Trichinella spiralis, the second with raccoon dog-origin Trichinella nativa, and the third served as controls. Infection dose for both parasite species was 1000 larvae/kg of body weight, which led to intense final infection. Clinical signs, haematology and serum biochemistry with repeated blood samples were monitored up to 12 weeks post-infection. The most significant findings were a short-term eosinophilia in peripheral blood from the end of the first week post-infection until the end of the third week, loss of weight, and mild anaemia. In the early phase of the infection, the animals had gastrointestinal signs, loss of appetite and diarrhoea. No specific differences in clinical findings could be noticed between the groups infected with T. nativa and T. spiralis. In contrast to the symptoms reported in human outbreaks, fever was not observed in any of the infected animals and serum levels of muscle-specific enzymes did not change. No acute-phase response was observed in the enteral or parental phase of the infection. These findings indicate that because Trichinella spp. are very well adapted to the raccoon dog, it thus, could serve as the most crucial reservoir animal for sylvatic trichinellosis in Finland.     

Mange caused by Sarcoptes scabiei (Acari: Sarcoptidae) in wild raccoon dogs, Nyctereutes procyonoides, in Kanagawa Prefecture, Japan

Parasitological and histopathological examinations were performed in 25 raccoon dogs (Nyctereutes procyonoides) obtained in Kanagawa Prefecture, Japan, all of which were found to be heavily infected with Sarcoptes scabiei. The mites detected on these raccoon dogs were morphologically indistinguishable from the human species, and no Demodex mites were detected. Histopathological examinations showed prominent hyperkeratosis and acanthosis with eczema, and numerous burrows containing mites were observed in the epidermis. The enzootic dermatitis of wild raccoon dogs in recent years was clearly demonstrated to be caused by S. scabiei in the present study.     

Listeriosis in a raccoon dog (Nyctereutes procyonoides) associated with canine distemper

A wild raccoon dog (Nyctereutes procyonoides) that manifested severe illness and died was examined. Necropsy revealed severe emaciation, systemic icterus and petechial hemorrhages on the mucous membranes. Histopathologically, necroses were seen in the liver and brain stem associated with meningitis. Eosinophilic intranuclear inclusion bodies were observed in the spleen and intestinal mucosa, and eosinophilic intracytoplasmic inclusion bodies were seen in transitional epithelium in the bladder. Listeria monocytogenes 4b was isolated from the liver, spleen, kidneys and lungs, and the pathogen was also detected in the liver and brain stem immunohistopathologically. The disease was diagnosed as listeriosis associated with canine distemper virus infection in a raccoon dog.     

Paragonimus westermani and some rare intestinal trematodes recovered from raccoon dogs (Nyctereutes procyonoides viverrinus) introduced recently on Yakushima Island, Japan

Helminth parasites were collected from 9 raccoon dogs (Nyctereutes procyonoides viverrinus) and 2 Japanese weasels (Mustela itatsi sho) on Yakushima Island, Japan. The former carnivore was introduced to this World Natural Heritage Area presumably within the last two decades, expanding its population thence, although detailed process(es) of the introduction is unknown. The collected trematodes from raccoon dogs included the triploid form of Paragonimus westermani, Brachylaima tokudai, Maritrema eroliae, and Pseudocryptotropa sp. Simultaneously, Paragonimus ohirai was found in one weasel killed by a traffic accident. Although the triploid form of P. westermani and P. ohirai are known to be distributed in some river-mouth areas of Yakushima Island based on previous surveys on crab hosts, natural infection was detected for the first time in wild final hosts. Particularly, the raccoon dog infected with P. westermani was caught in a mountainous area, distant from human residence or river-mouth areas. Although it is possible that the infected raccoon dog moved from a river-mouth area endemic with P. westermani after infection, the alternative scenario remains to be pursued; the endemic area of this zoonosis is expanding along with the recent expansion of raccoon dogs or feral cats (Felis catus), that became prevalent recently on this island including the mountainous areas. Maritrema eroliae taking a variety of shorebirds as its natural final hosts, and a minute trematode, Pseudocryptotropa sp., taking unknown natural final host(s) were recorded for the first time in raccoon dogs.     

First record of Cryptosporidium infection in a raccoon dog (Nyctereutes procyonoides viverrinus)

Cryptosporidium species have been found in more than 150 species of mammals, but there has been no report in raccoon dogs. Here we found the Cryptosporidium organism in a raccoon dog, Nyctereutes procyonoides viverrinus, and identified this isolate using PCR-based diagnostic methods. Cryptosporidium diagnostic fragments of the 18S ribosomal RNA, Cryptosporidium oocyst wall protein and 70-kDa heat shock protein genes were amplified from the isolate and sequenced to reveal the phylogenetic relationships between it and other Cryptosporidium species or genotypes reported previously. The results showed that the raccoon dog isolate represented the C. parvum cattle genotype which could be a causative agent in human cryptosporidiosis.     

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.     

Seasonal changes in immunolocalization of inhibin/activin subunits and testicular activity in wild male raccoon dogs (Nyctereutes procyonoides)

Thirty-four pairs of testes from wild adult raccoon dogs (Nyctereutes procyonoides) were obtained between September 2000 and May 2003. The cellular localization of the inhibin alpha and inhibin/activin (betaA and betaB) subunits in wild raccoon dog testes was investigated. The testicular weight and size and seminiferous tubule diameters were measured. There were marked seasonal variations in testicular weight and size and seminiferous tubule diameters, with values relatively low in September and high in March. Spermatogonia and primary spermatocytes were observed in September, and spermatogonia, spermatocytes, and round spermatids were present in January. All types of spermatogenic cells, including mature spermatozoa, were found in March, indicating that the breeding season is around March in Japan. Thereafter, spermatogonia and degenerating spermatocytes were observed in April. The sections of testes were immunostained by the avidin-biotin-peroxidase complex method (ABC) using polyclonal antisera raised against porcine inhibin alpha, inhibin/activin betaA and inhibin/activin betaB. The inhibin alpha and inhibin/activin (betaA and betaB) subunits were only expressed in Leydig cells in September. On the other hand, the inhibin alpha, betaA, and betaB subunits were observed in Leydig cells and Sertoli cells, but not in germ cells, in March. These results suggest that the testes of wild raccoon dogs have the ability to synthesize inhibins, and the cellular localization of inhibin/activin subunits showed season-related changes in the breeding and non-breeding seasons.     

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.