Toxocara canis

Holland, Celia V., 2023, A walk on the wild side: A review of the epidemiology of Toxocara canis and Toxocara cati in wild hosts, International Journal for Parasitology: Parasites and Wildlife 22, pp. 216-228 : 220

2.2. Wolf ( Canis lupus)

Several species of wolves have been the focus of helminth parasite surveys including Canis lupus (Linnaeus, 1758), the European wolf, the Italian or Apennine wolf – Canis lupus italicus, a subspecies of the gray wolf native to the Italian Peninsula, the Iberian wolf Canis lupus signatus, a subspecies living in the Iberian peninsula and the Ethiopian wolf – Canis simensis which is endemic to the Ethiopian highlands. C. simensis is the world’ s rarest canid with its main prey being the endemic giant mole rat (Sillero-Zubiri and Gottelli, 1995). To my knowledge, the only published study on the Ethiopian wolf is by van Kesteren et al. (2014) who recorded a prevalence of T. canis of 15% with a very low median epg of 3.

The extent of T. canis infections in European wolves ( Canis lupus) have received some attention in the published literature, although to a much lesser extent than that given to red foxes, with studies from 15 different countries ( Table 3). The first and most obvious observation is the much lower prevalences of T. canis in wolves, compared to red foxes, with many values below 10%. Notable exceptions are the high prevalences reported from Egypt (Radwan et al., 2009) and Kazakhstan (Abdybekova and Torgerson 2012). Of interest, is the fluctuation in prevalences between four studies from Italy ranging from 4.34% to 33% (albeit based upon a sample of 3). In general, worm burdens are low with only one study including a measure of aggregation (Segovia et al., 2003).

The prevalence of T. canis in wolves varies quite considerably ( Table 3) and this may be explained in part, by the fact that wolves rarely consume small mammals compared to other canids ( Guberti et al., 1993). In Latvia, a study of the feeding habits of wolves revealed wild ungulates (cervids and wild boar) and beavers as the wolves’ most frequent prey. Several species of small and medium-sized carnivores including the domestic dog, raccoon dog, red fox, badger, otter and weasel as well as some small rodents and insectivores were detected in the stomach content of wolves. However, their occurrence was comparatively low (Andersone and Ozolins, 2004). The range of parasite species infecting wolves may vary markedly dependent upon locally available prey species, the wolf biome and zoogeographical region, reflecting prey species biodiversity, the particular wolf-infective parasite stages they harbour and their relative population densities (Craig and Craig 2005; Guberti et al., 1993). An extensive study by Ståhlberg et al., (2017) compared the feeding habits of European wolves ( Canis lupus) from Northern and Southern Europe exemplified by Sweden and Italy. Diet composition varied between the two locations with higher prey abundance and choice associated with the greater ecological diversity of Italy compared to Sweden. However, in both locations, small mammals played a very small part in wolf diets in contrast to large prey such as moose in Sweden and wild boar and roe deer in Italy.

Differences in the prevalence of Toxocara between studies may be explained in part by the diagnostic method employed and environmental conditions at collection. Popiołek et al. (2007) highlighted how data from wolf scats based upon coprological analysis, including their own data at 5.6%, tend to be lower (see Table 3) than those values based on necropsies that are usually much higher, for example 17% in Italy, 16.6% in Greece or 21.2% in Belarus ( Guberti et al., 1993; Papadopoulus et al., 1997; Shimalov and Shimalov, 2000). According to Kloch and Bajer (2003) this may suggest that the eggs could be washed out of the faeces before collection, for example by rain or thawing snow.

Daszak et al. (2000) has emphasised the potential for pathogen transfer between wolves, companion animals, livestock and people, especially in anthropogenically modified cultural landscapes with a high human population density (Chapron et al., 2014). In a study that focused upon the recolonisation of wolves in Germany and the consequent founder effects on endoparasite diversity, LesniakHeckmann et al. (2017) suggested that it might be useful to implement endoparasite screening in order to benefit both domestic dog owners and hunters in wolf habitats, and to provide information to assist in well-informed decisions on anthelminthic dog treatment.