Detection of Spirocerca lupi and an unknown Trichinella-like nematode in raccoon (Procyon lotor)

Abstract

The raccoon Procyon lotor (Carnivora: Procyonidae) is an invasive species of growing importance for the introduction of alien pathogens or as additional hosts for autochthonous pathogens in Europe, including zoonotic parasites. As the population is steadily increasing and outcompeting the red fox (Vulpes vulpes) in Germany, the consumption of raccoon meat raises concerns about pathogens they may transmit. Therefore the presence of Trichinella larvae was here investigated in muscle samples (n = 904) of raccoons from northern Germany. No Trichinella larvae were found, thus confirming the general low occurrence of this parasite in Germany. However, Spirocerca lupi (n = 12) and an unidentified Trichinella-like nematode (n = 1) were accidently detected in the examined samples. The first is not a zoonotic parasite but has a high veterinary relevance as it can cause severe diseases in dogs. It is the first documented autochthonous infection of this nematode in Germany. The larvae of an unidentified Trichinella-like nematode were found in high abundance in all examined muscles of one raccoon, though they could not be identified to species level. Histological investigation revealed intramuscular cystic structures. This is the largest study investigating muscular parasites of raccoons in Europe so far, which suggests that this invasive animal species is infected by S. lupi and by a yet unknown Trichinella -like parasite.

Keywords: Foodborne zoonoses; Game meat; Germany; Procyon lotor; Spirocerca lupi; Trichinella.

Graphical abstract

Fig. 1

A: Origin of animals used for this study and the origin of the Trichinella-like infected individual (red dot). B [reproduced from Hagag et al. (2022)]: average yearly regional hunting bags during seasons 2014/15 to 2017/18 (harvested Individuals/100 ha). All regions with high regional hunting bags are represented in this study. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 2

Trichinella-like nematode larva: several hundreds of these larvae occurred during trichinella investigation.

Fig. 3

Abundance of unidentified nematode larvae at investigated muscle sites of one individual (larvae per gram). Density varies strongly between different muscles.

Fig. 4

Fig. 5. Masseter. HE. Bar = 50 μm. Parasitic cyst located within skeletal musculature containing two cross- and one longitudinal section of nematode larvae (arrowheads). Note the presence of a compressed, flattened, presumable myocyte nucleus (arrow) adjacent to the cyst wall.

Fig. 5

Tongue. PAS. Bar = 50 μm. Parasitic cyst in the skeletal musculature, containing three cross- and one longitudinal section of nematode larvae. Note the PAS-positive cyst wall (arrow) and the presence of bilateral hypodermal structures (stars) and a central degenerated digestive tract (arrowheads).

Fig. 6

Larvae in striated musculature of raccoon by trichinoscopy. Note the absence of a visible capsule (Original magnification A: 25 x).

Fig. 7

L 3 of Spirocerca lupi: These larvae occurred as accidental findings.