Sensitivity of Methods to Determine Presence of Baylisascaris procyonis Eggs in Raccoon (Procyon lotor) Feces

Baylisascaris procyonis, a nematode parasite of raccoons (Procyon lotor), has important implications for human health and ecological conservation. Several techniques are available for detecting B. procyonis, and it is important to consider their limitations for the specific question to be answered. The sensitivity of molecular tools to detect B. procyonis in comparison to traditional methods is unknown. We compared the sensitivity fecal flotation with PCR to identify raccoons infected with B. procyonis as determined by seeing worms at necropsy. We collected 2-6 g of fecal material from along the ascending, transverse, and descending colon of 31 raccoons, resulting in 48 fecal samples across 31 individuals. Samples were aliquoted into two sets to compare fecal flotation and PCR. Of the 31 raccoons, 7/31 (23%) were infected with B. procyonis, but fecal flotation analysis identified only 4/31 positive raccoons (13%). Using fecal flotations from known positive individuals, 4/10 (40%) were positive, but PCR did not discover any infected individuals. Our results demonstrate the importance of using multiple techniques to confirm B. procyonis presence or absence. Dissection of raccoon intestines is the most sensitive technique because it enables visualization of worms. Fecal flotations remain the most efficient method of determining environmental prevalence and positive individuals from fecal sampling. Although PCR is technically very sensitive, it is limited by the quality and quantity of DNA in a sample.