Long-term survey on Trichinella prevalence in wildlife of Slovakia

In Slovakia, monitoring the prevalence of Trichinella spp. in wildlife was performed since 2000 in the main reservoir animals, the red fox (Vulpes vulpes) and wild boar (Sus scrofa), using artificial digestion method as recommended by International Commission on Trichinellosis. The results of investigation performed in 5270 red foxes showed that Trichinella infection is widespread across Slovakia and prevalence increased significantly from 4.9% in 2000 to 20.5% in 2007. Recently, a higher Trichinella prevalence (0.11%) in wild boars was also demonstrated. The results indicate that foxes and wild boars are involved in the spread of Trichinella, although the latter host species seems to play a secondary role in the maintenance of the sylvatic cycle in Slovakia. Trichinella britovi is the predominant species circulating in Slovakia, both in foxes and wild boars, and Trichinella spiralis occurs only sporadically. Mixed infections of T. britovi and Trichinella pseudospiralis were recorded in 2005 in one wild boar from Eastern Slovakia and in 2006 in one red fox from the same region. These findings are important with respect to an outbreak caused by T. pseudospiralis in a pig farm in the same district 3 years ago. This study provides a complex picture on Trichinella occurrence in all regions of Slovakia and may be a good basis for evaluating the risk of parasite transmission to the domestic cycle and human beings.     

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.     

Detection and surveillance for animal trichinellosis in GB

The zoonotic disease trichinellosis is considered one of the re-emerging diseases with surveillance and control methods constantly gaining more importance worldwide. Recent change in European Union (EU) legislation introduces Trichinella-free production, and the possibility of risk-based monitoring for Trichinella in pigs. This has increased the role of wildlife surveillance programmes and their impact on protecting human health as well as highlighted the need for harmonised surveillance protocols and test methods for these infections. A modified digest method, based on the EU reference method for Trichinella testing of pig meat, was used to screen foxes present in Great Britain (England, Scotland and Wales) for trichinellosis. The method was validated using batched pools of 10 g foreleg muscle from up to 20 foxes (maximum amount 200 g). The method gave an average trichinae recovery rate of 71% for spiked samples. Assuming this recovery rate applies to all contaminated samples, then the test sensitivity would be 70% for all tissue samples with 0.1 trichinae per 10 g of foreleg muscle, 99.9% for samples with 1 trichinae per 10 g, and 100% for samples with 2 or more trichinae per 10 g. In two separate studies, conducted between 1999 to 2001 (Smith et al., 2003) and 2003 to 2007, over 3500 wild foxes have been screened for Trichinella with negative results. In the second study reported here, foxes were collected from locations throughout Great Britain using a stratified sampling method based on fox population densities. All work was conducted in compliance with appropriate quality assurance systems, latterly under ISO 9001. Results to date indicate the national prevalence of trichinellosis in foxes is <0.001 based on a 10 g individual sample size, an infection level of 1 larva per gram (l pg) and 95% confidence interval. This, together with no reports of trichinellosis in domesticated pigs, suggests that Britain can be considered a region of negligible risk of trichinellosis.     

Screening for infection of Trichinella in red fox (Vulpes vulpes) in Denmark

A total of 6141 foxes (Vulpes vulpes) were examined for infection with Trichinella. The foxes were killed in Denmark during the hunting season 1995-1996 and 1997-1998; 3133 and 3008, respectively. Foxes included in the investigation came from throughout the country with the exception of the island of Bornholm. The right foreleg from each fox was submitted for investigation. The legs were stored at -20 degrees C for 3-10 months prior to examination. Following thawing, muscle tissue (10 g) from each leg was examined by trichinoscopy and by a pepsin-HCl digestion technique. In 1995-1996, three foxes were found positive corresponding to a prevalence of 0.001. Each of the infected foxes harboured an extremely low infection, i.e. about one larva per 10 g muscle tissue. It was not possible to obtain sufficient larval material for species identification. All three foxes were shot in the vicinity of a small village in the north-western part of Denmark. In 1997-1998 no Trichinella cases were found. The results, compared with previous studies, indicate that the prevalence of infection of Trichinella sp. among wild living foxes in Denmark is very low. This is further supported by the fact, that no infection of Trichinella sp. has been found in slaughtered pigs in Denmark for more than 65 years, which suggests that the infection pressure is very low. Considering the facts above we conclude that the risk of Trichinella infections is negligible in intensive indoor pig production units in Denmark whereas high local prevalence of Trichinella infections in the wildlife might constitute a serious risk for the expanding outdoor pig production.     

Spatial distribution of Trichinella britovi, T. spiralis and T. pseudospiralis of domestic pigs and wild boars (Sus scrofa) in Hungary

Trichinellosis is a foodborne disease caused by the consumption of raw meat and raw meat-derived products from swine, horse and some game animals infected with nematode worms of the genus Trichinella. Between June 2006 and February 2011, 16 million domestic pigs and 0.22 million wild boars (Sus scrofa) were tested for Trichinella sp. in Hungary. Trichinella infection was not found in any pigs slaughtered for public consumption. Nevertheless, Trichinella spiralis was detected in four backyard pigs when trace back was done following a family outbreak. Trichinella infection was demonstrated in 17 wild boars (0.0077%). Larvae from wild boars were identified as Trichinella britovi (64.7%), T. spiralis (29.4%) and Trichinella pseudospiralis (5.9%). Although the prevalence of Trichinella sp. infection in wild boars and domestic pigs is very low, the spatial analysis reveals that the level of risk differs by region in Hungary. Most of the T. britovi infected wild boars (63.6%) were shot in the north-eastern mountain area of Hungary; whereas domestic pigs and wild boars infected with T. spiralis were detected only in the southern counties bordering Croatia and Romania. In the north-western and central counties, the prevalence of Trichinella infection seems to be negligible.     

Trichinella pseudospiralis foci in Sweden

In Sweden, the prevalence of Trichinella infection in domestic pigs has greatly decreased since the 1970s, with no reports in the past 4 years. However, infected wild animals continue to be found. The objective of the present study was to identify the species of Trichinella present in animals of Sweden, so as to contribute to the knowledge on the distribution area and hosts useful for the prevention and control of this zoonosis. In the period 1985-2003, Trichinella larvae were detected in the muscles of 81/1800 (4.5%) red foxes (Vulpes vulpes), 1/6 (16.7%) arctic fox (Alopex lagopus), 1/7 (14.3%) wolf (Canis lupus), 10/200 (5.0%) lynxes (Lynx lynx), 4/8000 (0.05%) wild boars (Sus scrofa), and 27/66 x 10(6) (0.000041%) domestic pigs. All four Trichinella species previously found in Europe were detected (Trichinella spiralis, T. nativa, T. britovi and T. pseudospiralis). The non-encapsulated species T. pseudospiralis was detected in three wild boars from Holo (Stockholm area) and in one lynx from Froso (Ostersund area), suggesting that this species is widespread in Sweden. These findings are consistent with those of a study from Finland, both for the unexpected presence of T. pseudospiralis infection and the presence of the same four Trichinella species, suggesting that this epidemiological situation is present in the entire Scandinavian region. The widespread diffusion of T. pseudospiralis in the Scandinavian region is also important in terms of it potential impact on public health, given that human infection can occur and the difficulties to detect it by the trichinelloscopic examination.     

Trichinella spiralis in wild boars (Sus scrofa)

During the period 1.7. 1972--31.6. 1977 muscle samples from 137 wild boars were examined for Trichinella spiralis. Larvae of T. spiralis were demonstrated in 4 animals. The major part (83) of the wild boars examined, including the 4 positive ones, originated from one particular game park. The rate of infection with T. spiralis in the game park concerned was 4.8%. Calculated on the basis of the total of animals examined, the rate of infection was 2.9%.     

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.     

The epidemiology of animal trichinellosis in China

The epidemiology of animal trichinellosis in China based mainly upon original Chinese literature published between 1937 and 2004 is reviewed. The seroprevalence of Trichinella infection in herbivores was 0.7% (2/300) in cattle and 0.8% (4/500) in sheep. The prevalence of trichinellosis in naturally infected cattle was 1.2% (2/163). Trichinella larvae were detected in 1.4% (3/215) of sheep and in 2.1% (1/47) of beef cattle sold at markets. Canine trichinellosis was recorded in 13 Provinces, Autonomous Regions or Municipalities (P/A/M) and the average prevalence of the infection in dogs slaughtered in abattoirs was 16.2% (5654/34,983) ranging from 1.2% to 44.8%, with the highest prevalence located in northeast China. The prevalence in dog meat sold at markets was 3.5% (988/27,898) in 5 P/A. Feline Trichinella infection was reported in 10 P/A/M. The prevalence of Trichinella infection in rats varied from 1.1% (51/459) to 15.1% (50/332). Trichinella larvae were detected in 1.5% (9/587) of house rats (Rattus norvegicus) as well as in 0.8% (3/369) of wild rats (Apodemus chevrieri), and the infection was recorded also in other wildlife (foxes, bears, wild boar, weasels, raccoon dogs, muntjak and bamboo rats). Trichinella larvae were detected in 2.6% (4/156) of weasels (Mustela sibirica), 1.5% (2/135) of shrews (Tupaia belangeri) and 7.7% (1/13) of moles (Parascapter leucurus). All Trichinella isolates from domestic pigs were identified as T. spiralis. Some Trichinella isolates from dogs in north-eastern China were identified as T. nativa, which has muscle larvae that are highly resistant to freezing. Twenty-seven outbreaks of human trichinellosis associated with mutton, dog and game meat occurred in China between 1964 and 2004, but the quarantine of Trichinella larvae in such meat is not mandatory in China at present.     

Occurrence of Giardia and Cryptosporidium in Norwegian red foxes (Vulpes vulpes)

Faecal samples from 269 Norwegian wild red foxes (Vulpes vulpes) shot during the hunting season (October-April) in 2002-2004 were examined for the presence of Giardia and Cryptosporidium. Cryptosporidium oocysts were detected in samples from 6 (2.2%) of the foxes, and Giardia cysts in 13 (4.8%) of the foxes. The prevalence of Giardia infection was significantly higher in juvenile male foxes than in adult male foxes, but no other significant differences between age and sex were found. No significant differences in prevalence related to geographical origin of animals were found. Insufficient nucleated Cryptosporidium oocysts were isolated for successful PCR, but genotyping of Giardia duodenalis isolates from seven foxes demonstrated a high degree of heterogeneity amongst them, with all isolates belonging to the zoonotic Assemblages A and B.     

A Survey of Trichinella spiralis in Wild Carnivores in Southwestern Quebec

In 1982-1983, 144 muscle samples from 11 different species of wild carnivores from southwestern Quebec, Canada, were examined for the presence of Trichinella spiralis larvae, using direct microscopic examination and the peptic digestion method. Two red foxes (Vulpes vulpes) (out of 29) and one pine marten (Martes americana) (out of 56) were found positive, giving a 2.1% prevalence for the whole sample.     

Survey for Trichinella spp. in red foxes (Vulpes vulpes) in Belgium.

Concurrently with a survey for Echinococcus multilocularis in the red fox (Vulpes vulpes) in Flanders, northern Belgium, serological and parasitological analyses for Trichinella spp. were carried out from 1996 to 1999. Muscle samples from foxes in Wallonia, southern Belgium, were obtained during a survey for rabies and alveolar echinococcosis from 1998 to 2000.In muscle samples from tongue, diaphragm, hindlegs and tail of 179 Flemish foxes no larvae were found by trichinoscopy. Serum and muscle juice of, respectively 176 and 26 animals were examined using an ELISA for the detection of antibodies against excretory-secretory (ES) antigen. There were eight (4.5%) positive sera, but no positive muscle juice samples.All muscle samples from 639 foxes in Wallonia proved to be negative for larvae in artificial digestion. Serum and muscle juice of 130 and 478 foxes, respectively were examined in ES-ELISA. There were 61 (46.9%) positive sera and 90 (18.8%) positive muscle juice samples. A comparison between 88 serum and muscle juice samples of the same foxes showed that only half of the serum-positive animals were detected using muscle juice. However, for establishing the true meaning of these results, a more profound epidemiological study on the vulpine population in Belgium is necessary.     

The use of tetracycline in anthelmintic baits to assess baiting rate and drug efficacy against Echinococcus multilocularis in foxes

Anthelmintic (praziquantel) baiting of wild red foxes against Echinococcus multilocularis infection was studied in a highly epizootic suburban area of Otaru, Hokkaido (the northern island of Japan) during the summer and autumn in the years 1999-2004. Acceptance of baits containing the biomarker tetracycline (TC) was evaluated. The prevalence of E. multilocularis infection in foxes before baiting (1999-2000) was 58% (88/153), whereas in the fourth year of bait distribution year (2004), it decreased to 11% (5/45). Analysis of TC marking in the teeth of foxes showed that 39% (77/195) of those captured after baiting were estimated to have consumed baits in the year of capture. Importantly, more juvenile (56%, 49/87) than adult foxes (26%, 28/108) were marked, indicating efficient baiting of juveniles, which tended to have a higher worm burden of E. multilocularis. Of 77 marked foxes, E. multilocularis and Alaria alata (monitored as the second indicator species of deworming) were not detected in 70 (90%) and 76 (99%) foxes, respectively. The results suggest effective deworming by bait consumption. However, it was also demonstrated that 9% of the marked foxes were infected or re-infected after bait consumption, suggesting high infection pressure and the importance of frequent baiting.     

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).     

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.     

Antibodies to West Nile virus and related flaviviruses in wild boar, red foxes and other mesomammals from Spain

Red foxes (Vulpes vulpes), wild boar (Sus scrofa) and Iberian pigs (Sus scrofa domestica) that are raised extensively outdoors, as well as other wild mesomammals from south central Spain and wild boar from Do?ana National Park (DNP), were tested for antibodies against related flaviviruses by ELISA and for antibodies against WNV by VNT. Mean flavivirus seroprevalence according to ELISA was 20.4±7.8% (21 out of 103) in red foxes, 12.6±2.8% (69 out of 545) in wild boars, and 3.3±2.7% (6 out of 177) in Iberian pigs. A stone marten (Martes foina) also tested positive. Flavivirus seroprevalence in wild boar was significantly higher in DNP, and increased with age. Haemolysis of the serum samples limited interpretation of VNT to 28 samples, confirming WNV seroprevalence in one red fox, four Iberian pigs and nine wild boars. ELISA positive, microVNT negative samples suggest presence of non-neutralizing antibodies against WNV or antibodies to other antigenically related flaviviruses. Despite the importance of wetlands for flavivirus maintenance and amplification, WNV/flavivirus seroprevalence in wild boar and red foxes was not associated to wetland habitats. This is the first report of exposure of red foxes to WNV. With view to use of the tested species as sentinels for flavivirus activity, limited exposure of Iberian pigs that would be available for regular sampling, low numbers of foxes collected and concentration of wild boar harvest in the winter season are major drawbacks.     

Low seroprevalence of antibodies to Neospora caninum in wild canids in Israel

The role of domestic dogs in the epidemiology of Neospora caninum as well as the relationship between N. caninum infection of farm dogs and cattle were demonstrated, however, evidence is scarce regarding the role of wild canids in domestic animal neosporosis. The present study was undertaken to evaluate the role of wild canids in the epidemiology of bovine neosporosis in Israel by analyzing the prevalence of antibodies to N. caninum in wild canids. Sera samples were collected from 114 free ranging wild golden jackals (Canis aureus), 24 red foxes (Vulpes vulpes) and nine wolves (Canis lupus), which were collected in Israel during the years 1999-2004. Of a total of 147 wild canids tested antibodies to N. caninum were only found in two golden jackals with IFAT titers of 1:50, and in one red fox and one wolf with IFAT titer of 1:400. The low seroprevalence found in this study (2.7%) indicated that wild canids probably do not have an important role in the epidemiology of N. caninum in Israel. However, since the diet of different species of wild canids and even diverse populations of the same canid species vary, it is possible that other results might be obtained from specific wild canids populations, which scavenge in the vicinity of infected bovines.     

Trichinella spiralis in wild animals, cats, mice, rats and farmed fur animals in Finland

A total of 1 399 samples of wild animals, cats, mice, rats and fur animals were examined for Trichinella larvae during the period 1.1.1982-30.6.1984. Samples were obtained both from the problem area, were Trichinella larvae had been found in pigs, and for comparison from the rest of Finland. The frequency of the infection in wild carnivores, badgers, pine martens, raccoon dogs, foxes and wild mink was significantly higher in the problem area than in the rest of Finland.     

Extraintestinal nematode infections of red foxes (Vulpes vulpes) in Hungary

A survey was carried out to investigate the prevalence and worm burden of extraintestinal nematodes in 100 red foxes (Vulpes vulpes) of Hungary. The overall prevalence of nematode infections of the respiratory tract was 76%. Eucoleus aerophilus (Capillaria aerophila) was the predominant species (66%), followed by Crenosoma vulpis (24%), Eucoleus (Capillaria) b?hmi (8%) and Angiostrongylus vasorum (5%). Pearsonema (Capillaria) plica was found in 52% of the urinary bladders. In 3% of the foxes, Trichinella britovi was present in muscle samples. The high prevalence of lungworms and P. plica and the fox colonisation in urban areas may enhance the prevalence of these nematode infections in domestic dogs and cats, and the flow of T. britovi from the sylvatic cycle to the domestic cycle, enhancing the risk of infections in humans.     

Prevalence of zoonotic important parasites in the red fox (Vulpes vulpes) in Great Britain

A national necropsy survey of red foxes was carried out across Great Britain to record Echinococcus, Trichinella and Toxoplasma. The survey did not record directly, or indirectly using coproantigen/PCR tests, evidence for the presence of Echinococcus multilocularis in 588 animals, although E. granulosus was suspected in six animals. Parasitological evidence for Trichinella spp. could not be found in 587 fox muscle digests, and a specific PCR test also failed to detect Toxoplasma in a sub-set of 61 random fox tongue biopsies. The upper 95% confidence interval for the above parasites was 0.60% (E. multilocularis), 0.60% (Trichinella spp.) and 5.6% (Toxoplasma). The commonest gut parasites were the hookworm Uncinaria stenocephala (41.3%) and the ascarid Toxocara canis (61.6%). This study also reports the second occurrence of Trichuris vulpis in Great Britain.