Detection of Avian Metapneumovirus Subtypes A and B in Moroccan Broiler Farms

Background: Avian metapneumovirus (aMPV) is a widespread infectious respiratory pathogen affecting turkeys and chickens, with co-predominance of the subtypes A and B. Objectives: There is no official reports in Morocco about the subtypes of aMPV circulating. Hence, using quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) subtypes-specific A and B, we aimed at detecting and identifying the potential subtype(s) circulating. Methods: We conducted a longitudinal study on three broiler flocks that were strictly not vaccinated against aMPV and were located in two different geographical regions. We studied two flocks that expressed typical swollen head syndrome (SHS) and sampled them once. Furthermore, we sampled dead birds of one flock confirmed seropositive from a previous study. A total of 118 swabs pooled in 24 samples were subjected to RNA extraction and amplified using a triplex RT-PCR for specific detection of aMPV subtypes A and B. Additionally, serum samples were taken at slaughtering age to cross-check the molecular results. A total of 84 sera were analyzed with a commercial indirect enzyme-linked immunosorbent assay (ELISA) kit to detect and titer antibodies against the two subtypes. Results: Avian metapneumovirus was detected by qRT-PCR in all flocks. About 87.50% of the samples were positive for aMPV-B, and 16.67% for aMPV-A and aMPV-B simultaneously. All flocks showed seropositivity, confirming the molecular findings. Conclusion: The present investigation is the first molecular study in Morocco to elucidate the circulation of aMPV-A and aMPV-B in broiler farms in Morocco with a dominance of aMPV-B and the possibility of co-presence of both subtypes.