Raccoons contraband - The metazoan parasite fauna of free-ranging raccoons in central Europe

Abstract

The invasive raccoon (Procyon lotor) is an abundant carnivore and considered as an important potential vector of infectious diseases and parasites in Europe. Raccoons show a broad, opportunistic, omnivorous food spectrum. Food supply and habitat quality in urban areas are very attractive for the generalist raccoon. This inevitably leads to increased interaction with humans, domestic animals and livestock, making the raccoon a potentially suitable zoonosis vector. In its autochthonous range, especially in the Eastern and Midwestern United States, the raccoon has been studied very intensively since the beginning of the 20th century. Whereas, basic field biology and parasitology studies in Germany and Europe are lacking and have only been conducted sporadically, regionally and on small sample sizes. In the presented study 234 raccoons from central Germany were comprehensively examined for their metazoan parasite fauna. The present study shows for the first time an extremely diverse parasite fauna in raccoons outside their native range and proves their essential role as intermediate hosts and hosts for ecto- and endoparasites. A total of 23 different parasite species were identified, five of which are human pathogens, 14 of which are new for the parasite fauna of raccoons in Europe. The human pathogenic raccoon roundworm Baylisascaris procyonis is the most common parasite species in this study, with a prevalence of up to 95%. The digenetic trematode Plagiorchis muris, another human pathogenic parasite species, was detected for the first time in raccoons. The ongoing spread of invasive carnivores and the associated spread and transmission of their parasites and other pathogens increases the potential health risk of wild and farmed animals as well as humans. An increase in parasitic diseases in humans (e.g. raccoon roundworm) is to be expected, especially in urban areas, where raccoons are becoming more and more abundant.

Keywords: Baylisascaris procyonis; Invasive species; Metazoan parasite fauna; Plagiorchis muris; Raccoon (Procyon lotor); Zoonotic diseases.

Graphical abstract

Fig. 1

Geographic origin of examined Procyon lotor (N = 234).

Fig. 2

Light micrographs of different endo- and ectoparasite species showing the general morphology of the identified parasites in the investigated raccoons; A: Euryhelmis squamula, B: Plagiorchis muris, C: Porrocaecum ensicaudatum, D: Polymorphus minutus, E: Neotrombicula autumnalis, F: Sarcoptes scabiei.

Fig. 3

Several factors influence the spread of Baylisascaris procyonis, infestation rates are higher in urban and agricultural environments than in semi-natural sites. Thus, a denser population of raccoons in urban areas has a beneficial effect on infestation numbers. However, other factors such as vegetation density as well as available food resources, microclimate, soil characteristics, and land use also influence the rate of B. procyonis infestation and zoonotic potential. An Unembryonated eggs are shed by the raccoon. Eggs undergo 2–4 weeks of development outside the body until the embryonated and infective stage is reached. Embryonated eggs can remain in the environment for several months and remain infectious. B In urban and agricultural areas, new intermediate hosts are frequently infected. These are either eaten by the raccoon or can become infected like the raccoon (e.g., dogs) and then also excrete eggs. C In urban and agricultural areas, there are usually other off-target hosts than in semi-natural areas. Here, for example, cattle or chickens have been confirmed as false hosts. In these hosts, visceral or ocular larva migrans is induced without the larvae being ingested by the raccoon. D Children can become infected with infectious stages and contract Larva migrans through constructed latrines as well as simple defecation in or near play facilities (e.g., sandboxes, climbing houses). E Due to the steady spread of raccoons, new false hosts are increasingly infected with eggs of B. procyonis, such as chicken birds (pheasants), even in semi-natural areas. F The normal life cycle of B. procyonis includes the prey of P. lotor such as various small mammals or birds. In Europe, these species also play the main role in semi-natural habitats. G Raccoons, as the primary host, become infected with B. procyonis by direct ingestion of embryonated eggs through contact with latrines and via excreted feces of infected raccoons. Numerous small mammals or birds serve as paratenic or intermediate hosts, passing larvae directly to the raccoon. The worms grow in the raccoon and can reach high densities in the raccoon's intestine.