Validation of a species-specific probe-based qPCR for detection of (Filarioidea: Onchocercidae) in Alaskan moose ().

Northern ungulates contend with and , filarioid nematodes that are transmitted by ectoparasitic blood-feeding arthropods, which can result in animal and population level impacts. microfilariae can be detected in fresh blood samples using a modified Knott's test, or by postmortem detection by genetic sampling or through the retrieval of adult specimens in the peritoneal cavity. In this study we validated a novel qPCR for detection of . DNA in blood samples of moose (). Additionally, we compared quantitative values from modified Knott's test to detect both and from both fresh and frozen blood samples. Species-specific primers targeting a 121-base pair fragment of the cytochrome oxidase c subunit 1 () of , and a species-specific probe were designed. The qPCR had a detection threshold of 0.157 pg/μL of parasite DNA. We collected 166 blood samples from wild moose captured on the Kenai Peninsula, Alaska from 2019 to 2022. Matching blood aliquots were tested by modified Knott's test and subjected to DNA extraction for subsequent qPCR. Quantitatively, blood samples had an average microfilaremia (mf) of 472.2 mf/mL (0-14,490 mf/mL) and of 72.9 mf/mL (0.0-5071.5 mf/mL). Qualitatively, 32.53% ( = 54) of samples tested positive for in each of the tests, and 37.35% ( = 62) when both tests were combined, with very good agreement between the results from Knott's test and qPCR ( 0.90). The validation of the qPCR test for allows for faster, less labor-intensive diagnosis and epidemiological surveillance of this emerging parasite in moose and other cervid hosts.