Molecular Study of Gamma Coronaviruses in Birds from the Southern Caspian Sea Coast of Iran

Gammacoronaviruses (γ-CoVs), including infectious bronchitis virus (IBV), cause economically important diseases in poultry and may act as reservoirs or bridges for viral dissemination. This study aimed to determine the frequency and genetic relationships of γ‑CoVs in asymptomatic wild and free-ranging birds of northern Iran. From February to December ۲۰۲۰, ۶۰ cloacal swabs were collected from ۱۱ bird species (n=۳–۱۰ per species); RNA was extracted and a one‑step RT‑PCR targeting a ۲۶۶‑bp fragment of the ۳’ untranslated region (۳’ UTR) was performed, positive amplicons were Sanger‑sequenced, sequences were aligned with reference γ‑CoV sequences, and phylogenetic analysis was carried out. Six of ۶۰ samples (۱۰.۰%) were RT‑PCR positive—۴/۱۰ rural chickens (۴۰.۰%) and ۲/۱۰ white‑headed ducks (۲۰.۰%)—while all other sampled species were negative. Sequence analysis of six isolates placed chicken‑derived viruses in a cluster with known chicken IBV strains (one isolate clustering closely with the H۱۲۰ vaccine sequence and two forming a separate subcluster), whereas the two duck-derived sequences were identical to each other and formed a distinct cluster with reference γCoV sequences from wild birds (e.g., duck, pigeon, and other avian hosts), indicating a shared lineage but not necessarily genetic identity with those reference strains. These findings indicate that asymptomatic free-ranging chickens and white-headed ducks in Golestan Province harbor γ-CoV RNA, suggesting local viral circulation and potential interactions at the wild–domestic interface Gammacoronaviruses (γ-CoVs), including infectious bronchitis virus (IBV), cause economically important diseases in poultry and may act as reservoirs or bridges for viral dissemination. This study aimed to determine the frequency and genetic relationships of γ‑CoVs in asymptomatic wild and free-ranging birds of northern Iran. From February to December ۲۰۲۰, ۶۰ cloacal swabs were collected from ۱۱ bird species (n=۳–۱۰ per species); RNA was extracted and a one‑step RT‑PCR targeting a ۲۶۶‑bp fragment of the ۳’ untranslated region (۳’ UTR) was performed, positive amplicons were Sanger‑sequenced, sequences were aligned with reference γ‑CoV sequences, and phylogenetic analysis was carried out. Six of ۶۰ samples (۱۰.۰%) were RT‑PCR positive—۴/۱۰ rural chickens (۴۰.۰%) and ۲/۱۰ white‑headed ducks (۲۰.۰%)—while all other sampled species were negative. Sequence analysis of six isolates placed chicken‑derived viruses in a cluster with known chicken IBV strains (one isolate clustering closely with the H۱۲۰ vaccine sequence and two forming a separate subcluster), whereas the two duck-derived sequences were identical to each other and formed a distinct cluster with reference γCoV sequences from wild birds (e.g., duck, pigeon, and other avian hosts), indicating a shared lineage but not necessarily genetic identity with those reference strains. These findings indicate that asymptomatic free-ranging chickens and white-headed ducks in Golestan Province harbor γ-CoV RNA, suggesting local viral circulation and potential interactions at the wild–domestic interface

کلیدواژه ها:

Gamma Coronavirus ، Infectious Bronchitis Virus ، Wild Birds ، Rural Chickens ، White headed Duck