A parasitological survey of wild red foxes (Vulpes vulpes) from the province of Guadalajara, Spain

An epizootiological survey of leishmaniosis, coccidiosis and parasitic helminths in 67 foxes (Vulpes vulpes) was conducted in Guadalajara (central Spain). Examination for parasitic protozoa revealed prevalences of 74% Leishmania (determined by molecular methods) and 2.9% coccidia oocysts (fecal flotation). Survey of parasitic helminths (fecal flotation/necropsy) demonstrated the presence of nine species, including six nematodes, two cestodes and one trematode. Nematodes were the most common parasites of foxes, followed by cestodes and trematodes. Greater levels of nematodes like Uncinaria, with a free-living stage in its life-cycle, were found in foxes in areas where moist soils were likely to exist, in contrast to areas of semiarid characteristics, where Toxascaris leonina or Trichuris vulpis were predominant. With regard to helminths of importance as human pathogens, trichinoscopy revealed the presence of a relatively high number of foxes (8.9%) infected with Trichinella spiralis. Finally, Toxocara canis infection was less frequent (4.4%) than trichinellosis.     

Spatial distribution of Trichinella britovi, T. pseudospiralis and T. spiralis in red foxes (Vulpes vulpes) in Hungary

The red fox (Vulpes vulpes) is considered one of the main reservoir of Trichinella spp. in Europe. As limited information on Trichinella infection in wildlife of Hungary is available, 2116 red foxes, representing more than 3% of the estimated fox population of the country, were screened to detect Trichinella larvae by a digestion method. Trichinella larvae from the 35 positive foxes were identified by a multiplex PCR as Trichinella britovi (30 isolates, 85.7%), Trichinella spiralis (4 isolates, 11.4%), and Trichinella pseudospiralis (1 isolate, 2.9%). The true mean intensity of T. britovi, T. spiralis and T. pseudospiralis larvae in lower forelimb muscles was 23.6, 3.5 and 13.5larvae/g, respectively. T. spiralis was detected only in the southern and eastern regions. The non-encapsulated T. pseudospiralis was recorded for the first time in Hungary. Although the overall true prevalence of Trichinella infection in foxes was only 1.8% (95% confidence interval, CI=1.5-2.1%), the spatial analysis reveals different risk regions. In the north-eastern counties bordering Slovakia and Ukraine (21% of the Hungarian territory), the true prevalence of Trichinella infection is significantly higher than that observed in other regions (6.0%, CI=4.8-7.1%). In the southern counties bordering Croatia, Serbia and Romania (41% of the Hungarian territory), the true prevalence of Trichinella infection is moderate (1.4%, CI=1.0-1.8%). In the north-western and central counties (38% of Hungarian territory), the prevalence of Trichinella infection is significantly lower (0.2%, CI=0.1-0.4%) than that of the other regions. Based on the statistical analysis and the evaluation of epidemiological data, none of the counties can be considered free of Trichinella infection. In the past decade, Trichinella infection has been detected only in few backyard pigs, and only few wild boar-related autochthonous infections in humans were described. Nevertheless, these results highlight the need of the maintenance of a strict monitoring and control programmes on Trichinella infection in farmed and hunted animals of Hungary.     

Factors affecting the flow among domestic, synanthropic and sylvatic cycles of Trichinella

Nematodes of the genus Trichinella are maintained in nature by sylvatic or domestic cycles. The sylvatic cycle is widespread on all continents, from frigid to torrid zones, and it is maintained by cannibalism and scavenging behavior of carnivores. Trichinella is primarily a parasite of carnivorous mammals, although one non-encapsulated species, Trichinella pseudospiralis, has also been detected in birds. The anaerobic metabolism of larvae in nurse cells allows their survival in extremely decayed meat. Encapsulated larvae in the decomposing carcass function similarly to the species-dispersing population of eggs or larvae of other nematodes, suggesting that the natural cycle of Trichinella includes a free-living stage when the parasite is no longer protected by the homeothermy of the host. Consequently, environmental temperature and humidity play an important role in the transmission of Trichinella among wildlife. Of the 10 recognized genotypes of Trichinella, only Trichinella spiralis is transmitted and maintained in a domestic cycle, although it can be present also in wildlife. All other genotypes (Trichinella nativa, Trichinella britovi, T. pseudospiralis, Trichinella murrelli, Trichinella nelsoni and Trichinella papuae, Trichinella T6, T8, and T9) are transmitted and maintained only in a sylvatic cycle. This generalization does not preclude sylvatic species of Trichinella from invading the domestic habitat, and T. spiralis may return to this habitat when humans fail in the management of wildlife and domestic animals. However, the presence of sylvatic genotypes of Trichinella in the domestic habitat represents a "dead-end" for the sylvatic cycle. Synanthropic animals (rats, foxes, mustelids, cats, dogs, etc.) contribute to the flow of sylvatic Trichinella genotypes from wildlife to domestic animals and of T. spiralis from domestic to sylvatic animals. Furthermore, human behavior not only influences the transmission patterns of Trichinella genotypes in the domestic habitat, but also it can contribute to the transmission and spread of this infection among wildlife, for example by improper hunting practices.     

Identification of sylvatic Trichinella (T3) in foxes from France.

Thirty-three foxes (Vulpes vulpes) from a sample of 1912 collected in France were found to be infected with Trichinella spp. Four isolates were obtained for genetic identification. Isoenzymatic and biological analysis of these isolates revealed the presence of two distinct genetic types of Trichinella, Trichinella spiralis s.str. (T1) and Trichinella sp. (T3) (Trichinella nelsoni according to Soviet authors) in the fox population. The reproductive capacity index of these isolates in Wistar rats was high for T. spiralis and low for T3. This is the first report of T3 type from wild animals in France. The epidemiological implications are discussed.     

Prevalence of Trichinella larvae and extra-intestinal nematodes in Norwegian red foxes (Vulpes vulpes)

A survey of the parasitic fauna of the Norwegian red fox (Vulpes vulpes) population was carried out in 1994/1995 and 2002-2005. All foxes were killed during the licensed hunting season from October to April and, in total, 393 animals from all regions of the country were examined. The present study details the results of extra-intestinal nematode and Trichinella larvae examinations. All individuals were examined for Trichinella, using routine digestion methods. Parasitological examination of the internal organs of some of the foxes also identified a number of different extra-intestinal nematodes. The following prevalences were identified (number positive/number foxes examined): Trichinella larvae 19/393 (4.8%); Capillaria b?hmi (C. b?hmi) 88/174 (51%); Capillaria aerophila (C. aerophila) 160/181 (88%); Crenosoma vulpis (Cr. vulpis) 105/181 (58%) and Capillaria plica (C. plica) 81/154 (53%). No evidence of Angiostrongylus vasorum infection was found. The 19 different Trichinella isolates were species typed by PCR and sequence analysis; 18 isolates were identified as Trichinella nativa and one as Trichinella britovi. A wide geographical distribution of the parasites was seen. The following exceptions were recorded: C. b?hmi, the prevalence of which was significantly lower in northern Norway (6%) compared to other regions (central Norway, eastern Norway and southern and western Norway; 52-57%). There was a significantly higher prevalence of Trichinella infection in eastern Norway (8.1%), when compared with the rest of the country (0.6%). Cr. vulpis prevalence was significantly higher in central Norway (83%) than in other regions (41-56%). There were no significant differences in age and sex distribution of the parasites with the exception of Cr. vulpis where juvenile foxes had a greater likelihood of infection. The data also indicated that adult foxes were more commonly infected with Trichinella larvae (5.8%) than juveniles (3.3%) (no statistical significance).     

Ascarid nematodes in domestic and wild terrestrial mammals

The biology of the ascarid nematodes has been discussed in the context of their important economic role in farm animals, pet animals and zoo animals with special attention to carnivores and primates. In farm animals, infection with the most common roundworm of horses (Parascaris equorum) and swine (Ascaris suum) depend on many factors such as environmental conditions (larval development in the egg and egg survival), age of the host, breed, husbandry system, hygiene and treatment schedule. The monoxenic ascarids Toxocara canis and T. cati are the most important nematodes in carnivorous animals (dogs, cats, foxes) and carnivores in the zoo. In the period of March 2000 till March 2001, 57.1% of examined representatives of Felidae, Ursidae and Canidae in the Zoological Garden of Wroc?aw were found to be infected with ascarids (T. canis, T. cati, Toxascaris leonina). The prevalence of T. canis in the Canidae was 66.7%, of T. cati in the Felidae was 14.3%, while 57.1% of the Felidae carried T. leonina infection. Ascaris lumbricoides, a typical parasite of primates, was found in some gorillas, chimpanzees and orang-utans during parasitological survey.     

Contamination of public children's playgrounds in Hannover with helminth eggs

Fifty-two public sand pits on children playgrounds in Hannover were investigated for the presence of parasites. A large proportion (63.5%) of these playgrounds were contaminated with parasite eggs. Eggs from Toxocara spp., Toxascaris leonina and other common helminth parasites were found in 55.8%, 9.6% and 26.1% of these playgrounds, respectively. A total of 208 sand samples were collected, and 30.8% of them contained eggs from Toxocara spp. (24.5%), Toxascaris leonina (2.4%) or other common helminths (9.1%). In 45.1% of the Toxocara positive samples, the eggs were embryonated. Eggs from Toxocara spp. were found in 33.0%, 31.0% or 14.0% of samples from districts with low, medium or high numbers of dogs per hectare, respectively.     

Presence of Trichinella spiralis in free-living red foxes (Vulpes vulpes) in Sweden related to trichinella infection in swine and man

One thousand one hundred and fifty-one free-living foxes (Vulpes vulpes) from different parts of Sweden were investigated. Totally 19.6 % were infected with trichinella. Infected foxes were found in all counties except the geographically isolated island of Gotland. In the different counties 6–48 % of investigated foxes were infected.Trichinella was more common in old foxes than in young, 40 % and 11 %, respectively. Regarding male and female, however, the frequency was the same.The number of trichinella per g of muscle varied between 0.05 and 200. Less than 1.0 trichinella larva per g muscle was established in 27.3 % of the foxes, between 1 and 49.9 trichinella larvae in 69.3 % and 50 or more trichinella larvae per g muscle in 3.4 % of the foxes. The number of trichinella larvae per infected fox was roughly the same in both sexes as well as in different age groups.The potential danger of transmitting trichinella from foxes and other carnivores to swine and man is pointed out.The high frequency of trichinella in foxes, 19.6 %, was compared to the very low frequency in swine, 0.00018 %, and in man, 0.00003 %.     

Parasite fauna of red foxes in Berlin (West)

The infestation with ecto- and endoparasites of red foxes in Berlin (West) was investigated. As shown by post mortems of 100 animals (47 males and 53 females), none of them was found to be free of parasites. With regard to ectoparasites, 3 species of ixodes ticks, 7 flea species, one species of biting lice and mite species were demonstrated. The sarcoptic mange is often inducing the death of the foxes and is considered to be a limiting factor of the population increment. Concerning endoparasites, cestodes (6 species), trematodes (7 species), nematodes (10 species) and 3 coccidian species were found. The infestation rate with different species of hook worms, ascarids and mesocestoides was remarkably high. However, none of the foxes were infected with Trichinella spiralis or Echinococcus multilocularis. As shown by ELISA, in 15% of foxes antibodies against Borrelia burgdorferi were found. Therefore, the red fox must be considered as a reservoir host for Lyme-borreliosis.     

Vaccination of rats and pigs against Trichinella spiralis spiralis using the subspecies, T. spiralis nativa.

Rats and pigs were vaccinated against Trichinella spiralis spiralis either by feeding infective larvae of the subspecies, Trichinella spiralis nativa in musculature or by gavage. The number of larvae established in the musculature of vaccinated nonchallenged and vaccinated challenged rats and pigs were negligible and statistically comparable, while highly significant infections were established in the nonvaccinated challenged rats and pigs. High vaccination doses of T. spiralis nativa gave virtually complete protection to challenge with T. spiralis spiralis in pigs. The results of one trial in rats with a lower vaccination dose of larvae suggest that there is a minimal vaccination dose of larvae required to elicit marked resistance to challenge. The low numbers of muscle larvae established due to the high vaccination doses of larvae confirm the low infectivity of the subspecies, T. spiralis nativa in rats and pigs.     

Epidemiological investigations on Trichinella infections in farmed fur animals of Estonia

Farming of fur animals represents an important income in Estonia. Even though Trichinella worms does not induce a symptomatic disease in carnivores, the carcasses of skinned animals can increase the biomass of the parasite in the environment, if they are not properly destroyed. The aim of the present survey was to study the prevalence of Trichinella worms in farmed fur animals of Estonia. Of 281 muscle samples from blue foxes (Alopex lagopus), silver foxes (Vulpes vulpes fulva), minks (Mustela vison) and raccoon dogs (Nyctereutes procyonoides), which were collected in eight farms, Trichinella larvae have been detected in 21 animals (8%) from two farms by HCl-pepsin digestion. The highest number of larvae per gram of muscle was found in the front limb muscles. Larvae of the 21 isolates have been identified as Trichinella britovi or Trichinella nativa by a multiplex-PCR analysis.     

Factors affecting preconditioning of Trichinella spiralis nativa larvae in musculature to low temperatures.

The influence of preconditioning temperature, length of the preconditioning period, host and age of the infection on the survival of Trichinella spiralis nativa larvae in musculature to low temperature refrigeration was investigated. Dogs, foxes, ferrets, mink and guinea pigs were infected with a T. spiralis nativa isolate, killed at various times postinfection, preconditioned at temperature of -10 degrees C, -15 degrees C or -20 degrees C for varying periods of time prior to low temperature refrigeration and subsequent pepsin digestion to determine survival of larvae. The preconditioning temperature played an important role in the subsequent survival of larvae in musculature at low refrigeration temperatures. Under the conditions of this study, survival of larvae was greater as the preconditioning temperature became lower. The minimum period of preconditioning required had an inverse relationship with the refrigeration temperature. Preconditioning of the T. spiralis nativa isolate used occurred in the musculature of guinea pigs, foxes, ferrets, mink and dogs with larvae surviving longer in vulpine and canine musculature than in the other hosts studied. Age of the infection was not a major factor in the survival of preconditioned larvae in musculature at low refrigeration temperatures although survival was slightly longer in older infections.     

Epizootiological survey of Trichinella spp. infection in carnivores, rodents and insectivores in Hokkaido, Japan

In order to evaluate the present epidemiological situation of Trichinella infection in wild animals in Hokkaido, Japan, red foxes (Vulpes vulpes), raccoon dogs (Nyctereutes procyonoides) , brown bears (Ursus arctos) , martens (Martes melampus), rodents and insectivores captured in Hokkaido were examined for muscle larvae by the artificial digestion method from 2000 to 2006. Foxes (44/319, 13.8%), raccoon dogs (6/77, 7.8%) and brown bears (4/126, 3.2%) were found to be infected with Trichinella larvae and all other animal species evaluated were negative. Multiplex PCR and DNA sequencing revealed that larvae from a fox captured in Otofuke, in south-eastern Hokkaido, were T. nativa, and larvae from 27 animals including 21 foxes, 2 raccoon dogs and 4 brown bears captured in western Hokkaido were Trichinella T9.     

A Study on the Predilection Sites of Trichinella spiralis Muscle Larvae in Experimentally Infected Foxes (Alopex lagopus,Vulpes vulpes)

Kapel, Chr. M., Sv. Aa. Henriksen, H. H. Dietz, P. Henriksen, P. Nansen: A study on the predilection sites of Trichinella spiralis muscle larvae in experimentally infected foxes (Alopex lagopus, Vulpes vulpes). Acta vet. scand. 1994, 35, 125-132.–Studies were carried out on the predilection sites of Trichinella spiralis muscle larvae in experimentally infected arctic foxes (Alopex lagopus) and silver foxes (Vulpes vulpes) reared in cages. The highest number of larvae per gramme tissue was found in the muscles of the legs, eyes, diaphragm, and tongue. The 2 fox species showed no significant differences with regard to predilection sites.     

旋毛虫各隔离种雌虫生殖能力的实验研究

本试验对旋毛虫各隔离种雌虫体外产新生幼虫能力进行了研究。结果显示，猪旋毛虫和旋毛形线虫(Trichinella spiralis)雌虫体外培养24h平均产新生幼虫数分别为66.00±7.34和76.20±7.57，而犬旋毛虫和本地毛形线虫(Trichinella nativa)分别是28.80±4.30和22.00±3.22，前者在雌虫体外产幼虫能力上明显高于后者。研究结果表明，黑龙江猪旋毛虫相当于旋毛虫形线虫，犬旋毛虫相当于本地毛形线虫。     

旋毛虫新生幼虫p46 000抗原基因的克隆及序列分析

应用旋毛虫感染猪血清，对旋毛虫新生幼虫cDNA文库进行了免疫筛选。对阳性克隆pBK-cMV-WN10的序列分析结果表明。cDNA全长为1352bp。含有1个1218bp的完整的开放阅读框架(ORF)，编码的多肽由406个氨基酸残基组成，其相对分子质量理论推导值为45900，等电点为5．43，N末端的信号肽及糖基化位点(NCS)表明其可能为分泌性糖蛋白，氨基酸序列19～156与158～295为重复区域，相似性为74％．C末端有1个半胱氨酸蛋白酶抑制剂结构域，但旋毛虫p46000抗原与其他线虫的半胱氨酸蛋白酶抑制蛋白结构有很大差异，可能已经失去半胱氨酸蛋白酶抑制蛋白的功能。PCR结果显示。从旋毛虫新生幼虫、肌幼虫、3日龄成虫和5日龄成虫cDNA中均扩增出此基因，表明此基因在旋毛虫各个时期均有表达。     

旋毛虫死活快速鉴别的实验研究

为了寻找快速鉴别旋毛虫死活的染色方法。用0．03％美蓝、美蓝-伊红-硼砂染液(M．E．B)和1％中性红3种染液，对死或活旋毛虫幼虫和成虫进行染色。结果3种染液均能使死亡旋毛虫幼虫在1分钟内着色，活虫则不着色。3种染液对旋毛虫死、活成虫均不着色。结论认为3种染液染色均可快速鉴别旋毛虫幼虫死活。     

Muscle distribution of sylvatic and domestic Trichinella larvae in production animals and wildlife

Only a few studies have compared the muscle distribution of the different Trichinella genotypes. In this study, data were obtained from a series of experimental infections in pigs, wild boars, foxes and horses, with the aim of evaluating the predilection sites of nine well-defined genotypes of Trichinella. Necropsy was performed at 5, 10, 20 and 40 weeks post inoculation. From all host species, corresponding muscles/muscle groups were examined by artificial digestion. In foxes where all Trichinella species established in high numbers, the encapsulating species were found primarily in the tongue, extremities and diaphragm, whereas the non-encapsulating species were found primarily in the diaphragm. In pigs and wild boars, only Trichinella spiralis, Trichinella pseudospiralis and Trichinella nelsoni showed extended persistency of muscle larvae (ML), but for all genotypes the tongue and the diaphragm were found to be predilection sites. This tendency was most obvious in light infections. In the horses, T. spiralis, Trichinella britovi, and T. pseudospiralis all established at high levels with predilection sites in the tongue, the masseter and the diaphragm. For all host species, high ML burdens appeared to be more evenly distributed with less obvious predilection than in light infections; predilection site muscles harbored a relatively higher percent of the larval burden in light infections than in heavy infections. This probably reflects increasing occupation of available muscle fibers as larger numbers of worms accumulate. Predilection sites appear to be influenced primarily by host species and secondarily by the age and level of infection.     

Experimental trichinosis in sheep.

Trichinella spiralis spiralis infections were established in sheep by administering infective larvae via gavage or feeding infected musculature. Trichinella spiralis nativa infective larvae had a low infectivity for sheep although light infections may be established in some animals with large infective doses. For the most part, sheep were averse to ingesting musculature mixed in a grain ration unless it was camouflaged with molasses. The heaviest infections usually occurred in the masseter muscle. The fact that sheep are averse to ingesting muscle tissue may reduce the likelihood of trichinosis. Anti-Trichinella antibodies to both T: spiralis spiralis and T. spiralis nativa were produced as demonstrated by the enzyme-linked immunosorbent assay. Seroconversion occurred in several sheep challenged with T. spiralis nativa even though larvae were not recovered from the musculature by pepsin-digestion.