Bovine Respiratory Disease: Sero-Epidemiological Surveys in Unvaccinated Cattle in Morocco

Viral respiratory diseases are a major cause of severe clinical symptoms and substantial economic losses in cattle breeding. This study aimed to evaluate the epidemiological status of four respiratory viruses in cattle including Bovine Viral Diarrhea Virus/Mucosal Disease Virus (BVDV/MDV), Infectious Bovine Rhinotracheitis/Infectious Pustular Vulvovaginitis Virus (IBR/IPV), Bovine Respiratory Syncytial Virus (BRSV), and Bovine Parainfluenza Virus type 3 (PI3). A total of 1,741 blood samples were collected from 242 unvaccinated herds. The animals comprised 1314 females and 427 males, aged between 6 months and 5 years. The herds included both pure breeds (Holstein or Montbéliarde breeds) and crossbreeds (local-Holstein or local-Montbéliarde), and were located in 89 rural communes of six regions of Morocco including Casablanca-Settat, Rabat-Salé-Kénitra, Marrakech-Safi, Béni Mellal-Khénifra, Fès-Meknès, and Oriental. The samples were analyzed using the I-ELISA technique. The results indicated seroprevalence rates of 56.1, 21.5, 86.4, and 85.4% for BVD/MD, IBR/IPV, BRSV, and Parainfluenza-3, respectively. Co-infections were observed in 88% of the infected cattle, and 95% of the cattle were infected with at least one of the four viruses. Seroprevalence rates varied significantly with age, sex, breed, breeding systems, and practices. These findings confirmed the endemic status of bovine respiratory viral diseases and highlighted their direct and indirect impacts on livestock losses in Morocco.