Intestinal Helminths of the Wisconsin Muskrat (Ondatra zibethicus)

Abstract

Ondatra zibethicus, also known as the muskrat, is a semiaquatic rodent commonly found in North America. These rodents contribute significantly to the local economy, environment, and public health. Every year, from October to March, trappers capture these rodentss in Horicon Marsh located in Dodge County, Wisconsin. Once caught, the animals are skinned, and the pelts are sold. The role of this rodent, as a bioindicator, cannot be ignored. Due to its sensitivity to change, the muskrat population can be viewed as an alert system for a deteriorating ecosystem. Several environmental conditions afflicting Ondatra zibethicus include drought, anthropogenic contamination, and predation. Most importantly, their ability to be a host for a variety of diseases makes the fur bearer a useful model. In collaboration with trappers at Horicon Marsh, the carcasses of 45 muskrats were examined in this two-part study. Thirty-six carcasses were collected by Sarah Woody, a previous graduate student at UWO, and necropsied in May of 2021. In January 2023 nine more were collected for the same purpose. The tongues retrieved from the muskrats were assayed for the presence of helminths. Trichinella spp. is an intracellular nematode that can encyst in the muscle of many hosts including mammals, birds and reptiles. In order to establish their presence within a muskrat, the tongues collected were digested with the help of artificial digestive fluids concocted using HCL and Pepsin. The tongues were cut into pieces, blended, and the mixture observed under a dissecting microscope for the presence of Trichinella spp. The small and large intestines were assayed all parasites recovered from the small and large intestines were placed in 80% ethanol. Thereafter, the collected parasites were separated based on visual differences, fixed in formaldehyde, mounted on slides, and morphologically identified. Morphologic identification revealed the presence of intestinal helminths such as Plagiorchis proximus, Quienquiseriales quienquiserialis, Echinostoma spp., Trichuris opaca, and a Cestode spp. Mitochondrial and Ribosomal DNA was extracted, and the genetic samples were sent out for sequencing via third party to confirm morphologic identification.