Biomolecular investigation for Capillaria spp. infections on bronchoalveolar lavage fluid of owned domestic dogs presented for chronic cough in Belgium

The trichuroid parasitic nematode Capillaria aerophila (syn. Eucoleus aerophilus) is responsible for lower respiratory infections and Capillaria boehmi (syn. Eucoleus boehmi) for sino-nasal infections in wild and domestic carnivores. Animals become infected by eating environmental embryonated eggs or earthworms. The adult worms live embedded in the epithelia of the bronchioles, bronchi, and trachea or in the nasal sinuses, respectively. Infections with C. aerophila can be sub-clinical or lead to chronic bronchial inflammation, rarely bronchopneumonia. C. boehmi may cause nasal discharge, sneezing or olfactory impairment. Knowledge about prevalence and distribution of both parasites beyond Eastern Europe and Mediterranean countries is lacking. The aim of this study was to assess the prevalence of C. aerophila infection in coughing, client-owned, domestic dogs in Belgium. Stored bronchoalveolar lavage fluid (BALF) from 125 dogs (median age 7.3 years, range: 0.3-17.2 years) from March 2018-2022 was retrieved. All dogs had history of chronic cough (> 2 weeks duration) and underwent BALF collection for microbiologic testing of common respiratory pathogens. DNA extracted from BALF samples was stored at -80°C until further analysis. A conventional polymerase chain reaction targeting a region internal to the cox1 gene of C. aerophila, a Capillarinae consensus sequence, was performed on BALF samples in duplicate and in batch analysis using previously published primers sequences. DNA of adult C. boehmi specimens was included as a positive control. Molecular grade water was used as a negative control. Neither DNA of C. aerophila nor C. boehmi were detected in the BALF samples. Sixty-seven dogs (54%) had a recent history of deworming against lungworms with either moxidectin or fenbendazole (deworming protocol not standardized), 9 dogs (7%) were not up to date with deworming therapy, and the remaining 49 dogs (39%) had unknown deworming status. Result of this study suggest that C. aerophila infection is not prevalent in Belgium in dogs with chronic cough. This might be explained by recent deworming therapy in half of the included dogs. Epidemiosurveillance of capillarid infection may be considered in wild canids, such as foxes, to determine whether these parasites are a potential risk for domestic animals.