Evaluating noninvasive methods for estimating cestode prevalence in a wild carnivore population

Abstract

Helminth infections are cryptic and can be difficult to study in wildlife species. Helminth research in wildlife hosts has historically required invasive animal handling and necropsy, while results from noninvasive parasite research, like scat analysis, may not be possible at the helminth species or individual host levels. To increase the utility of noninvasive sampling, individual hosts can be identified by applying molecular methods. This allows for longitudinal sampling of known hosts and can be paired with individual-level covariates. Here we evaluate a combination of methods and existing long-term monitoring data to identify patterns of cestode infections in gray wolves in Yellowstone National Park. Our goals were: (1) Identify the species and apparent prevalence of cestodes infecting Yellowstone wolves; (2) Assess the relationships between wolf biological and social characteristics and cestode infections; (3) Examine how wolf samples were affected by environmental conditions with respect to the success of individual genotyping. We collected over 200 wolf scats from 2018–2020 and conducted laboratory analyses including individual wolf genotyping, sex identification, cestode identification, and fecal glucocorticoid measurements. Wolf genotyping success rate was 45%, which was higher in the winter but decreased with higher precipitation and as more time elapsed between scat deposit and collection. One cestode species was detected in 28% of all fecal samples, and 38% of known individuals. The most common infection was Echinococcus granulosus sensu lato (primarily E. canadensis). Adult wolves had 4x greater odds of having a cestode infection than pups, as well as wolves sampled in the winter. Our methods provide an alternative approach to estimate cestode prevalence and to linking parasites to known individuals in a wild host system, but may be most useful when employed in existing study systems and when field collections are designed to minimize the time between fecal deposition and collection.

Detection of prions from spiked and free-ranging carnivore feces

“…CWD had not been detected in the study area during sampling periods, nor had CWD been detected in cervids within 30 kilometers of the study area. Fecal collection methods for wolf 43 ). This region is characterized by high CWD prevalence 44 -an area where CWD was first established in WI, has been estimated to have been present in the environment for over 20 years 45 , and studied extensively in prior research [46][47][48] .…”

“…CWD had not been detected in the study area during sampling periods, nor had CWD been detected in cervids within 30 kilometers of the study area. Fecal collection methods for wolf 43 , followed by fox, coyote, cougar, and raven from the NYE are described briefly. Feces from GPS radio collared wolves (IACUC IMR YELL Smith wolves 2012) were collected in 2020 during early winter (30 days: November 15-December 15) approximately 17 days following deposition.…”

Wildlife parasitology: sample collection and processing, diagnostic constraints, and methodological challenges in terrestrial carnivores

“…In the recent decade, detection of genomic material of parasites by end-point PCR, real-time PCR, or metabarcoding has become popular [ 78 ]. Molecular analysis is especially useful in the differential diagnosis of taxa whose diagnostic stages cannot be identified to species, such as the case of taeniid, strongylid, or ancylostomatid eggs.…”

“…Furthermore, Echinococcus granulosus sensu lato, Echinococcus canadensis , Echinococcus multilocularis , Taenia serialis , Dipylidium caninum , and other unidentified Taenia and Mesocestoides spp. were detected in wolf scats from the USA by using a multiplex PCR for the detection of cestode species [ 78 ].…”

Challenges of copro‐parasitological surveys in wild Iberian ibex (Capra pyrenaica) populations addressed through a combination of molecular and statistical tools

“…Field identification of fecal samples can be inaccurate (e.g., 18% inaccuracy in carnivore samples – Monterroso et al, 2019 ). One way to minimize the bias from non‐invasive sampling for copro‐parasitological surveys in wildlife is to identify the host species using fecal DNA (Brandell et al, 2022 ; Cardoso et al, 2021 ; Zhang et al, 2011 ).…”