Non-Strongyloides rhabditida identified in fecal samples – two case reports: lessons learned from morphological and molecular diagnostic approaches

Abstract

SUMMARYNematodes in the order Rhabditida, including species ofStrongyloidesandPelodera, may be parasites of domestic animals. In this paper, we describe two apparent cases of rhabditid infections, one in a dog and one in a litter of piglets. The dog infection was originally considered likely to be an infection withStrongyloides, based on superficial morphological examination and PCR results without sequencing. However, more careful morphological analysis and inclusion of several molecular analyses, including sequencing, revealed that an infection withPeloderasp. was more likely, probablyPelodera pseudoteres. Treatment with fenbendazole and selamectin was apparently successful. Similarly, based on both morphological and molecular analyses the apparent piglet infections were considered most likely to be withRhabditisspp., possiblyRhabditis axei. The detection of larvae of nematodes in the order Rhabditida in fecal samples, particularly from dogs, may easily be considered as being indicative ofStrongyloidesinfection. Given the zoonotic potential of canineStrongyloides, correct diagnosis is important. However, as illustrated by these two cases, careful morphological examination and measurement, supported by full molecular investigations, including sequencing, are essential in order to avoid this misdiagnosis.