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Members of the Ascarididae family are common zoonotic pathogens in humans and play an economic role in domestic and livestock animal husbandry. This family includes the obligatorily parasitic nematodes of the genus Baylisascaris , with the raccoon roundworm Baylisascaris procyonis being the most well-known representative. B. procyonis uses the raccoon ( Procyon lotor ) as its primary host and can utilise a broad range of mammals as paratenic hosts. Sexual reproduction of the adult nematodes occurs in the small intestine. Eggs are excreted into the environment through feces, where they develop into the infectious stage under suitable conditions within a few days to weeks. Infection of primary and paratenic hosts occurs through the oral ingestion of these infectious eggs. Raccoons can also become infected by ingesting infected paratenic hosts. Humans serve as accidental hosts and can suffer significant damage to organ tissues, the visual system, and the central nervous system after ingesting infectious eggs. The aim of the study was to investigate the effects of ambient temperature on embryonic development and to document the morphological changes during embryogenesis. Live specimens were collected from the raccoon intestine and incubated. Single-celled eggs were collected during this process. The eggs were decorticated and then preserved. To test the effects of ambient temperature, the eggs were incubated at 5 °C, 10 °C, 15 °C, 20 °C, 25 °C, 30 °C, 35 °C, and 38 °C and monitored at 24-h intervals for their developmental stages. Detailed photographic documentation of the developmental stages was conducted. An increase in ambient temperature led to a reduction in development time. The temperature range within which embryogenesis proceeded to the L1 larval stage was between 10 °C and 30 °C. Incubation at 5 °C did not produce L1 larvae even after 11 months. Incubation at 35 °C and 38 °C resulted in the complete degeneration of the eggs before reaching the L1 larval stage., Competing Interests: The authors declare no competing interests., (© 2024 The Authors.)

To demonstrate predation and potential impacts of raccoons on various species, a total of 108 raccoons from aquatic-associated nature reserves and natural areas in three federal states of Germany, Hesse (n = 36), Saxony-Anhalt (n = 36) and Brandenburg (n = 36), were investigated from a dietary ecological perspective in the present study. Fecal analyses and stomach content examinations were conducted for this purpose. Additionally, as a supplementary method for analyzing the dietary spectrum of raccoons, the parasite fauna was considered, as metazoan parasites, in particular, can serve as indicators for the species and origin of food organisms. While stomach content analyses allow for a detailed recording of trophic relationships solely at the time of sampling, parasitological examinations enable inferences about more distant interaction processes. With their different developmental stages and heteroxenous life cycles involving specific, sometimes obligate, intermediate hosts, they utilize the food web to reach their definitive host. The results of this study clearly demonstrate that spawning areas of amphibians and reptiles were predominantly utilized as food resources by raccoons in the study areas. Thus, common toad ( Bufo bufo ), common newt ( Lissotriton vulgaris ), grass frog ( Rana temporaria ), and grass snake ( Natrix natrix ) were identified as food organisms for raccoons. The detection of the parasite species Euryhelmis squamula , Isthmiophora melis , and Physocephalus sexalatus with partially high infestation rates also suggests that both amphibians and reptiles belong to the established dietary components of raccoons from an ecological perspective, as amphibians and reptiles are obligate intermediate hosts in the respective parasitic life cycles of the detected parasites. The study clearly demonstrates that raccoons have a significant impact on occurrence-sensitive animal species in certain areas and, as an invasive species, can exert a negative influence on native species and ecosystems., (© 2024 The Authors. Published by Elsevier Ltd on behalf of Australian Society for Parasitology.)

Originally from Asia, the raccoon dog Nyctereutes procyonoides is an invasive alien species in Europe, listed since 2019 on the List of invasive alien species of Union concern. The raccoon dog is considered to have negative impact on native biodiversity, as well as a crucial role in hosting and transmitting diverse parasites and pathogens of human and veterinary importance. In the present study, stomach content analyses and parasitological examinations were performed on 73 raccoon dogs from Germany. In addition, fecal samples were analyzed. The results of the study confirm the assumption that the examined raccoon dogs were infested with a various ecto- and endoparasite fauna. A total of 9 ecto- and 11 endoparasites were detected, with 6 of the endoparasites having human pathogenic potential. Trichodectes canis (P = 53.42%), Toxocara canis (P = 50.68%) and Uncinaria stenocephala (P = 68.49%) were the most abundant parasite species. The stomach contents consisted of approximately one-third vegetable and two-thirds animal components, composed of various species of amphibians, fish, insects, mammals and birds. Among them were specially protected or endangered species such as the grass frog Rana temporaria . The study shows that the raccoon dog exerts predation pressure on native species due to its omnivorous diet and, as a carrier of various parasites, poses a potential risk of infection to wild, domestic and farm animals and humans., Competing Interests: The authors declare no competing interests., (© 2023 The Authors.)

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., Competing Interests: The authors declare no competing interests., (© 2023 The Authors.)

Unlike farm animals, wild animals are not subject to continuous health surveillance. Individual projects designed to screen wildlife populations for specific pathogens are, therefore, also of great importance for human health. In this context, the possible formation of a reservoir for highly pathogenic zoonotic pathogens is a focus of research. Two of these pathogens that have received particular attention during the last years are the novel severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), due to its fast global spread and high impact to the human health, and, since its introduction into Germany, the flavivirus West Nile virus (WNV). Especially in combination with invasive vertebrate species (e.g., raccoons ( Procyon lotor ) and raccoon dogs ( Nyctereutes procyonoides ) in Germany), risk analysis must be done to enable health authorities to assess the potential for the establishment of new wild life reservoirs for pathogens. Therefore, samples were collected from raccoons and raccoon dogs and analyzed for the presence of SARS-CoV-2 and WNV infections in these populations. Molecular biological and serological data obtained imply that no SARS-CoV-2 nor WNV reservoir has been established in these two wild life species yet. Future investigations need to keep an eye on these invasive carnivore populations, especially since the close contact of these animals to humans, mainly in urban areas, would make animal-human transmission a challenge for human health.