Epidemiology of Toxocara canis in red foxes (Vulpes vulpes) from urban areas of Bristol

Influence of environmental factors on the occurrence of gastrointestinal and cardiopulmonary nematodes in the red fox in the semi-arid Mediterranean areas of the Iberian Peninsula

Human-induced ecosystem fragmentation is one of the drivers causing wildlife migration from their natural habitats to urban areas, among other reasons. The red fox (Vulpes vulpes) is the most abundant wild canid in the semi-arid Mediterranean areas of the Iberian Peninsula. Water scarcity may result in areas shared by synanthropic fox populations and domestic animals becoming hotspots for parasite transmission. This study describes the gastrointestinal and cardiopulmonary nematode species affecting fox populations in these semi-arid areas and the influence of environmental variables on parasite abundance. A total of 167 foxes collected from 2015 to 2021 in the Region of Murcia (SE Spain) were analysed. Parasite abundance and spatial distribution were evaluated using environmental variables and host characteristics with a Generalised Linear Model and the Moran index. Eleven species (seven from the gastrointestinal tract and four from the cardiopulmonary tract) were described. The influence of biotic and abiotic variables was studied for Angiostrongylus vasorum, Crenosoma vulpis, Uncinaria stenocephala, Toxocara canis and Toxascaris leonina. Temperature, humidity and areas of forest or agricultural land influenced the abundance of these parasites, providing optimal conditions for free-living stages of the direct life cycle nematodes and intermediate hosts. Absolute abundance distribution maps showed defined locations for C. vulpis, T. canis and T. leonina. The results for U. stenocephala, T. canis and T. leonina were particularly important as their higher abundance levels were found close to anthropized areas, which need to be carefully evaluated to prevent transmission of these nematodes between domestic and wild canids and human health.

A walk on the wild side: A review of the epidemiology of Toxocara canis and Toxocara cati in wild hosts

Toxocara species are cosmopolitan nematode parasites of companion, domestic and wild hosts. Of the 26 known species of Toxocara, only Toxocara canis and Toxocara cati are definitively zoonotic. The significance of wild carnivores as definitive hosts of T. canis and T. cati respectively, has received far less attention compared to domestic dogs and cats. Complex environmental changes have promoted increasing contact between wildlife, domestic animals and humans that can enhance the risk of pathogen spillover. This review lists a total of 19 species of wild canid host that have been shown to act as definitive hosts for T. canis and a total of 21 species of wild felid host. In general, the number of publications focusing on felid host species is fewer in number, reflecting the general paucity of data on T. cati. The wild canids that have received the most attention in the published literature include the red fox (Vulpes vulpes), the wolf (Canis lupus), and the golden jackal (Canis aureus). The wild felid species that has received the most attention in the published literature is the Eurasian lynx (Lynx lynx). Some non-canid and non-felid hosts also act as definitive hosts of Toxocara species. Certainly, red foxes would appear to be the most significant wild species in terms of their potential to transmit Toxocara to domestic dogs and humans via environmental contamination. This can be explained by their increasing population densities, encroachment into urban areas and their dietary preferences for a wide range of potential paratenic hosts. However, a major challenge remains to assess the relative importance of wild hosts as contributors to environmental contamination with Toxocara ova. Furthermore, one major constraint to our understanding of the significance of wildlife parasitism is a lack of access to samples, particularly from rare host species.

Significance of the red fox as a natural reservoir of intestinal zoonoses in Vojvodina, Serbia

In the present study, 223 foxes were collected from various localities in the northern part of the Republic of Serbia (Vojvodina province) and examined for intestinal helminths. Among the examined foxes 178 (79.8%) were infected. The most frequently identified parasites were Mesocestoides spp. (49.3%) and Toxascaris leonina (36.3%). The parasite with the lowest prevalence was Pterygodermatites affinis (0.9%), and this is the first confirmed finding in Serbia. The other recovered species were Alaria alata (25.6%), Taenia spp. (6.3%), Echinococcus multilocularis (13%), Toxocara canis (16.6%) and Uncinaria stenocephala (14.8%). The highest number of foxes infected with E. multilocularis were in the Srem area. The results of this study indicate the presence of helminth species in red foxes in Vojvodina which may also infect humans.

Intestinal helminths of red foxes (Vulpes vulpes) in north-west Italy

A total of 180 foxes (Vulpes vulpes) from an area scarcely investigated of north-west Italy, were examined for intestinal helminths using sedimentation and counting technique (SCT). Faecal samples were submitted to centrifugation with 50 % zinc sulphate used as flotation solution.

No fox was found completely negative for intestinal helminths. The most frequently identified nematodes were Uncinaria stenocephala (70.0 %), Molineus legerae (27.2 %), Toxocara canis (26.7 %), Toxascaris leonina (25.6 %), Trichuris vulpis (21.1 %), Aonchotheca putorii (8.9 %), Pterygodermatites affinis (5.6 %). Genus Mesocestoides (81.7 %), family Dilepididae (29.4 %) and Taenia spp. (8.3 %) were the most prevalent cestodes. All foxes were negative for E. multilocularis and E. granulosus. In two foxes trematodes belonging to the family Plagiorchidae were found.

The study highlighted that foxes are hosts of intestinal helminths of veterinary and medical importance which may be transmitted to dogs and humans.

Intestinal parasites of the red fox (Vulpes vulpes) in Slovenia

In the present study, 428 foxes were collected and examined for intestinal helminths using the washing-out method. Parasites were found in 93.2% of the examined animals. The most frequently identified nematodes were Uncinaria stenocephala (58.9%), Toxocara canis (38.3%) and Molineus patens (30.6%). Other nematodes found were Pterygodermatites affinis (4.2%), Capillaria sp. (2.8%), Crenosoma vulpis (2.8%), Toxascaris leonina (2.5%), Trichuris vulpis (0.7%) and Physaloptera sp. (0.2%). Mesocestoides sp. (27.6%) and Taenia crassiceps (22.2%) were the most prevalent cestodes, followed by T. polyacantha (6.5%), Hymenolepis nana (2.1%), T. pisiformis (2.1%) and Dipylidium caninum (1.4%). The study also revealed four trematode species: Rossicotrema donicum (1.6%), Heterophyes heterophyes (1.1%), Metagonimus yokogawai (1.1%), Prohemistomum appendiculatum (0.4%) and two protozoan species: oocysts of Sarcocystis (2.8%) and Isospora (0.4%). This is the first extensive study on the intestinal parasites of the red fox (Vulpes vulpes) in Slovenia. The 2.6% prevalence of Echinococcus multilocularis in the same sample population as investigated herein has been reported previously (Vergles Rataj et al., 2010).

A coprological survey of parasites of wild carnivores in Ireland

The increasing movement of people to wilderness areas, shrinking of wildlife habitats and the resulting urbanisation of wildlife has led to growing concerns about the transfer of parasitic diseases, particularly from contaminated faeces. Faecal samples from wild carnivores in Ireland were examined for the presence of protozoan and nematode parasites. Red fox (Vulpes vulpes) samples (n = 91) were positive for Uncinaria stenocephala (38%), Eucoleus aerophilus (26%), Toxocara canis (20%), Trichuris vulpis (4%) and Isospora-like oocysts (9%). Badger (Meles meles) samples (n = 50) were positive for Uncinaria criniformis (40%), E. aerophilus (6%) and Isospora-like oocysts (16%). No parasites were observed in pine marten (n = 48; Martes martes) faeces. Approximately 5% of American mink (Mustela vison) samples were positive for Cryptosporidium by polymerase chain reaction (identified as Cryptosporidium andersoni (n = 3) and 'mink' genotype (n = 1)). The results suggest that wild carnivores in Ireland have a range of parasites, although it is unclear from the present study to what extent these infections are associated with morbidity. While it can be expected that, via their faeces, wild carnivores contribute to the spread of these parasites, they are unlikely the primary source of environmental contamination. Therefore, they should not always be the principal target of control measures.

Contamination of fox hair with eggs ofToxocara canis

Eighty-seven red foxes were investigated for the presence ofToxocaraeggs on a sample of their hair from the peri-anal region. The worm burden ofToxocarain each fox intestine was also assessed and the relationship between eggs on the hair and worms in the intestine explored. Twenty-eight per cent of the foxes were found to haveToxocaraeggs on their hair, with an average of 1.31 ± 3.21 eggs per gram of hair ( ± SD). Sixty-one per cent of foxes harbouredToxocaraworms within their intestines, with a mean worm burden ( ± SD) of 4 ± 8. Host age and sex did not significantly influence the observed eggs on the hair or the worm burden. No significant correlation was found between the numbers of eggs on the hair and the worm burden within the intestine. These data collected from foxes are explored in the context of data from stray dogs and the possible epidemiological differences are discussed.

Influence of urbanization on the epidemiology of intestinal helminths of the red fox (Vulpes vulpes) in Geneva, Switzerland

Dixenous helminths that depend on rodent intermediate hosts are supposed to be negatively affected by urbanization due to lower supply of rodents in urbanized environments. Prevalence rates of dixenous, non-strictly monoxenous, and monoxenous helminths in 228 red foxes (Vulpes vulpes) along a gradient of increasing urbanization were assessed by morphological parasite identification in the city of Geneva, Switzerland. Multivariate analyses for the five most prevalent helminth species or genera revealed a significant decrease of prevalence rates for the dixenous helminths Echinococcus multilocularis and Taenia spp. from the rural (52.1 and 54.3%, respectively) to the urban area (30.0 and 20.0%, respectively), but not for the monoxenous nematode Uncinaria stenocephala (overall prevalence of 78.2%) and the non-strictly monoxenous nematode Toxocara canis (overall prevalence of 44.3%). The lower prevalence of Toxascaris leonina in the urban area (8.0%) compared to the rural area (59.6%) raises the question of whether rodent paratenic hosts play a major role for the population dynamics of this species.

Population dynamics and epidemiology of Toxocara canis in Danish red foxes

Toxocara canis, an intestinal helminth of canids with zoonotic potential, was found in 618 (59%) of 1,040 red foxes (Vulpes vulpes) collected from all Danish provinces (1997-2002). The prevalence and average worm burden were significantly higher for cubs than older foxes and in males than in females. A multiple logistic regression demonstrated that the prevalence was influenced significantly by sex and age of foxes in addition to location, season, and year of collection. The highest prevalence and worm burden were found in rural areas. The size and number of female worms was positively correlated to the fecal egg excretion. The length and fecundity of the worms was significantly higher in male foxes, and a general intensity dependence was suggested from a negative correlation between worm numbers and worm lengths. As compared to intestinal recovery of worms, somatic larvae were recovered from 20% of muscle samples and fecal eggs in 41% of fecal samples. The consistent finding of T. canis larvae in somatic tissues of naturally infected foxes is new.

Echinococcus multilocularis and Toxocara canis in urban red foxes (Vulpes vulpes) in Brussels, Belgium

During the last decades, European red foxes (Vulpes vulpes) have been implicated in the transmission of several viral or parasitic pathogenic agents to domestic animals and humans. In urban areas, risks of zoonoses transmission are likely to increase as a result of a higher rate of intra- and inter-species contacts. Foxes occur on 35% of the Brussels-Capital Region area and local densities reach up to 4 family groups per square kilometre. According to the directive 2003/99/ECC, a first survey for the presence in foxes of Echinococcus multilocularis and Toxocara canis was conducted in Brussels from 2001 to 2004. None of 160 foxes were found to be infected with E. multilocularis and 24 of 134 foxes were found to be infected with T. canis. Considering numbers of examined foxes, the sensitivity and the specificity of tests used for diagnosis, the 95% credibility intervals for the true prevalence of E. multilocularis and T. canis were estimated in a Bayesian framework to be 0 to 1.87% (median value of 0%) and 12.7 to 26% (median value of 18.7%), respectively. For T. canis, a significantly higher risk to be a carrier occurs in cubs and a significantly lower risk in adults.

Toxocara canis in experimentally infected silver and arctic foxes

In two experiments, thirty-six farm foxes of two species were inoculated with various doses of infective Toxocara canis eggs or tissue larvae isolated from mice. In experiment I, six adult arctic foxes (Alopex lagopus; 11-month old) were each inoculated with 20,000 eggs and sacrificed 100, 220, or 300 days post infection (dpi), while ten silver fox cubs (Vulpes vulpes; 6-9-week old) were infected with varying doses of eggs (30-3000) and necropsied 120 dpi. In experiment II, two groups of five cubs and two groups of five adult silver foxes received both a primary inoculation and either one or two challenge inoculations: primary inoculation (day 0) with 400 embryonated eggs were administered to five cubs and five adults and another five cubs and five adults received 400 larvae. At 50 dpi, the first challenge inoculation (400 eggs) was inoculated in all animals. At 100 dpi, three animals from each group were necropsied. The remaining two animals in each group were received a second challenge inoculation of 400 tissue larvae on 100 dpi and were subsequently necropsied at 150 dpi. In both experiments, the highest numbers of larvae per gram (lpg) of tissue was found in the kidneys (100-300 dpi). In adult foxes receiving a high dose (20,000 eggs), increasing larval burdens were found in the kidneys over the course of the experiment (up to 300 dpi). The larval migration from the lungs to other tissues appeared to be dose-dependent with the highest larval burdens found in adult foxes. The faecal egg excretion, larval burden and intestinal worm burdens decreased from the first to the second challenge infection.

A helminthological survey of wild red foxes (Vulpes vulpes) from the metropolitan area of Copenhagen

Sixty-eight red foxes were collected from the metropolitan area of Copenhagen and examined for helminth infections. Standard faecal flotations for intestinal parasites gave the following results: Strongyle eggs (75.0%), Capillaria eggs (36.8%), Toxocara eggs (23.5%), Taenia eggs (1.5%), and coccidia oocysts (2.9%). Gastrointestinal helminths were collected from 21 of the 68 foxes with the following specimens found: Uncinaria stenocephala (85.7%), Toxocara canis (81.0%), Taenia spp. (38.1%), Mesocestoides lineatus (23.8%) and Polymorphus spp. (9.5%). Faeces of 39 foxes were examined by the Baermann method for larvae of cardiopulmonary worms with 20 foxes (51.3%) being infected. Fourteen foxes (35.9%) were infected with Angiostrongylus vasorum, 11 (28.2%) were infected with Crenosoma vulpis, and 5 foxes (12.8%) were infected with both species. Muscle digestion of diaphragms from the 68 foxes indicated that none harboured larvae of Trichinella spiralis.

Epidemiological studies on intestinal helminth parasites of rural and urban red foxes (Vulpes vulpes) in the United Kingdom

An epidemiological study of intestinal helminths in 843 foxes (Vulpes vulpes) from southern England revealed the presence of 13 parasite species: five nematodes--Toxocara canis (prevalence 55.9%), Toxascaris leonina (1.5%), Uncinaria stenocephala (68.0%), Trichuris vulpis (0.5%) and Capillaria aerophila (0.2%); four cestodes--Taenia pisiformis (13.8%), Taenia hydatigena (2.5%), Echinococcus granulosus (0.1%) and Dipylidium caninum (3.8%); two trematodes--Brachylaima recurva (2.9%) and Cryptocotyle lingua (2.3%); two acanthocephalans--Prosthorhynchus transversus (0.7%) and Macracanthorhynchus catulinus (0.1%). Trichuris vulpis, Brachylaima recurva, Macracanthorhynchus catulinus and Prosthorhynchus transversus are new host records for the UK. Results are discussed with reference to variations in the diets of urban and rural foxes and to their potential as reservoir hosts for helminths of medical and veterinary importance.