First serological evidence of circulation of equine rhinitis A virus and molecular detection of equine rhinitis B virus in horses in North Africa.

Equine rhinitis A virus (ERAV) and equine rhinitis B virus (ERBV) are major respiratory pathogens of horses with a global distribution. The aim of this study was to evaluate, for the first time in Algeria, the seroprevalence of ERAV antibodies, and to investigate a wide range of equine viruses (EIV, EHV-1, EHV-4, ERAV and ERBV). A total of 298 serum samples were collected between May 2022 and October 2023, from 11 provinces. Serological analysis for the presence of ERAV was performed using the complement fixation test (CFT). Our results revealed that 16.8% (50/298) samples tested positive for antibodies to ERAV. In parallel, 23 nasal swabs (NS) collected during this period were analyzed by RT-PCR for the detection of ERAV and ERBV. In addition, 74 different sample materials (50 NS, 21 fecal samples, and 3 urine samples), were taken from horses presenting with cough and mucopurulent nasal discharge, between November 2023 and June 2025. The prevalence of equine respiratory virus infections was examined using polymerase chain reaction (PCR). One, or more, of five equine respiratory viruses were detected in the nasal swabs of 3 of 72 horses (4.2%) and the detection rate of equine herpesvirus type 4 (EHV-4) and ERBV were 4.2% and 2.8%, respectively. Unfortunately, viruses could not be sequenced due to low viral load i.e. they had high Cycle Threshold (Ct) values. Equine herpesvirus type 1 (EHV-1), equine influenza virus (EIV) and ERAV were not detected in any samples. Among the three infected horses, two were co-infected with EHV-4 and ERBV. ERAV seroprevalence possibly varied according to sampling period. This study is the first to report the circulation of ERAV and ERBV in the Algerian horse population. Further studies are necessary to isolate and obtain molecular characterisation of ERAV and ERBV from horses in Algeria. Detailed research on epidemiological risk factors for ERVs infections in horses is essential to support and improve diagnosis, prevention and control strategies against these viruses.