Parasitic and Bacterial Infections of Myocastor coypus in a Metropolitan Area of Northwestern Italy

The coypu (Myocastor coypus) is a widespread rodent throughout Europe. The European coypu population can significantly affect ecosystems, resulting in adverse socioeconomic and health consequences for humans and animals (e.g., Kettunen et al. 2008; Aviat et al. 2009). In Italy, coypus are mostly found in wetlands of northern and central regions. In northern Italy, they are present in flatland areas, where rivers represent the main means dispersal. In Lombardy, a northwestern region, the coypu population reached a high density of 16.7 coypus per km², or approximately 500,000 individuals.

The most common causes of death for juvenile coypu in Europe are trapping, shooting, and predation by foxes (Vulpes vulpes) and domestic dogs (Canis lupus familiaris). Information on diseases affecting coypus in Italy is insufficient (e.g., Bollo et al. 2003; Nardoni et al. 2011). We performed a population health survey in the metropolitan area of Milan (northwestern Italy) to determine the prevalence of selected parasitic and bacterial infections of veterinary and zoonotic importance.

Our study was approved by the Milan University Institutional Animal Care and Use Committee (A23/08, 09-2008). We surveyed 153 coypus killed during a regional culling program (November 2008–March 2011). Coypus were found shot within Milan province (Lombardy; 45°30′N, 9°30′E), a densely human-populated area where coypus are abundant because of farms, climate, and the absence of natural predators. Gross necropsy examinations were performed, and lung, fecal, and blood samples were collected. Carcasses were screened for macroscopically visible ecto- and endoparasites, and age, sex, and body weight were recorded. No pathologic gross lesions and visible parasites were found at necropsy.

Fecal samples (153) were examined by FLOTAC® dual technique (Cringoli 2006). The eggs-per-gram count was determined for worms, but only qualitative data were recorded for coccidia. We performed a parasitologic intestinal examination of a subset of animals whose fecal samples contained helminth eggs. Adult helminths were collected and identified according to Rossin et al. (2006, 2009). An immunoenzymatic assay (RIDASCREEN® Giardia and RIDASCREEN Cryptosporidium, R-Biopharm, Darmstadt, Germany) was used to detect coproantigens of Giardia duodenalis and Cryptosporidium spp. Coypus were infected by intestinal nematodes (Strongyloides myopotami and Trichostrongylus duretteae) and coccidia, but no coproantigens of G. duodenalis and Cryptosporidium spp. were detected. The highest prevalence was found for Eimeria coypi and Strongyloides spp., with the latter being the more abundant taxon compared to Trichostrongylus spp. by quantitative analysis (Table 1).

An indirect enzyme-linked immunosorbent assay (ELISA) (ID Screen® Toxoplasmosis Indirect Kit, IDVET, Montpellier, France) was used to detect serum antibodies to Toxoplasma gondii. Thirty-seven of 128 (28.9%) animals had detectable antibodies to T. gondii. Antibody titers corresponding to an acute (sample index >200) or chronic infection (sample index 50–200) were observed in 19 and 18 coypus, respectively. We extracted DNA from lung tissues of 19 coypus with acute T. gondii infection (as determined by ELISA) using QIAampDNA Mini Kit (QIAGEN, Valencia, California, USA) following the manufacturer’s instructions and processed DNA by real-time PCR as described by Hurtado et al. (2001). The PCR products were purified (Wizard® SV gel, Promega, Madison, Wisconsin, USA) and sent to a commercial sequencing service (Primm Biotech, Milan, Italy). The PCR amplified T. gondii DNA from all analyzed lungs, resulting in a group of 16 identical sequences and a group of three identical sequences. One sequence for each group was submitted to the European Molecular Biology Laboratory database (HG793393–HG793394).

We performed bacterial culture analysis on 89 lungs by using sheep blood agar, brain heart infusion agar with 5% horse serum, and MacConkey agar according to usual protocols, and we used the Analytical Profile Index system to identify genera. Fecal samples (128) were examined for Salmonella spp. by a technique similar to ISO 6579 (International Organization for Standardization 2002), adapting it to the available quantitative of feces by using buffered peptone water. Results of bacterial analysis are summarized in Table 2.

A microagglutination test was used to detect serum antibodies to Leptospira interrogans (minimum significant titer was 100) with a panel of eight serovars: Australis/Bratislava, Ballum/Ballum, Canicola/Canicola, Grippotyphosa/Grippotyphosa, Icterohaemorrhagiae/Copenhageni, Pomona/Pomona, Sejroe/Hardjio, and Tarassovi/Tarassovi (World Organization for Animal Health 2008). Antibodies to L. interrogans were found in 66 coypus (44.9%); Australis/Bratislava (42.8%), Icterohemorrhagiae/Copenhageni (12.2%), Ballum/Ballum (0.7%), and Canicola/Canicola (0.7%) were the only four serovars detected. High titers (800; 1,600; 3,200; and ≥6,400) were found in 13 animals with antibodies to Australis/Bratislava serovar.

A backward elimination logistic regression analysis using SPSS version 19.0 (SPSS Inc., Chicago, Illinois, USA) was performed on qualitative data to determine factors that could be considered predictors of infections. Weight was the main risk factor for both parasitic and bacterial infections in coypus, particularly, the risk of being infected with Trichostrongylus, Strongyloides, Toxoplasma, and Leptospira increased with increasing weight. Sex was a risk factor for Strongyloides; females were at higher risk than males. Season was not a risk factor for any pathogen (Table 3).

The intestinal parasites found in M. coypus were typical for this species (S. myopotami, E. seideli, and E. coypi) or for other species of Rodentia (T. duretteae) (e.g., Rossin et al. 2009). Usually found in animals captured in their native habitats, they were recorded here for the first time in coypus from Italy, suggesting that the introduction and spread of coypus in the metropolitan area of Milan could have allowed spread and establishment of nonindigenous parasitic species. As suggested by egg counts and prevalence values, these parasites seem well established in this environment, and some (i.e., T. duretteae) could represent a risk for native animals related to coypus. For example, S. myopotami is a zoonotic parasite that causes a severe itchy cutaneous rash some hours after contact with water or soil contaminated by its larvae (Bonilla et al. 2000). In contrast with previous studies in Europe, hepatic flukes were not found in the coypus (Menard et al. 2001).

The antibody prevalence (30%) of the cosmopolitan zoonotic protozoan T. gondii confirmed the wide presence of this parasite in coypus. Their infection is likely to be sustained by ingestion of oocysts contaminating vegetables, mollusks, and drinking water, or it might be transmitted congenitally (Holmes 1977). Infected coypus could transmit T. gondii to domestic dogs and cats (Felis catus) via feeding on their carcasses. Given that humans may become infected with T. gondii by oocysts contaminating the same areas where the coypu acquired the infection, other risks for infection of humans could be preparing meat or ingestion of undercooked tissue from infected coypus (Tenter et al. 2000).

The most frequent bacterial species identified was Staphylococcus aureus (10.1%), an etiologic agent of pneumonia in farmed and feral coypu (Martino and Stanchi 1994). The prevalence of other isolated bacteria was low; however, some of them are likely to cause disease in livestock or humans (Bert et al. 1998; Benedito et al. 2011). In agreement with Bollo et al. (2003), no Salmonella spp. infections were identified in fecal samples.

Leptospira spp. are zoootic pathogens and have variable prevalence and variable serovars infecting coypus. In northern Italy, Bollo et al. (2003) found only Bratislava (11.5%) and Icterohaemorrhagiae (3.4%) serovars, but we detected antibodies to four serovars of L. interrogans in coypu. Comparing serology, renal carriage, and shedding of leptospires in urine from coypus and other rodents, it was demonstrated that coypu are likely to carry Leptospira, although they are less efficient than muskrats (Ondatra zibethicus) and rats (Rattus norvegicus) in maintaining and spreading the infection by shedding leptospires (Aviat et al. 2009; Vein et al. 2013). More studies are needed to determine whether coypus could represent an actual risk for animal and human health in the surveyed area.

In urban areas, coypu populations are increasing. Although coypus in our study seemed healthy, and no infected animals showed clinical signs, these rodents likely play a role as reservoir for parasitic and bacterial infections. Therefore, they are a risk for domestic animals that scavenge them and for humans consuming their meat improperly. A careful monitoring of pathogens, including parasites, should be performed within a management program for M. coypus.

We thank all provincial rangers for help with collecting coypus, the three anonymous reviewers, and the assistant editor for constructive comments.