Infectious bronchitis virus (IBV) and low-pathogenic avian influenza virus (LPAIV) H9N2 are commonly identified in poultry, individually or in association with other pathogens. This study monitored 183 broiler farms affected by respiratory diseases across seven regions of Morocco from January 2021 to December 2023. Among these farms, 87.98% were vaccinated against IBV, while 57.92% were against AI H9N2. Abnormally high mortality rates were observed in 44.26% of the farms, with 24.69% of cases attributed to IBV, 50.62% to LPAI H9N2, and 13.58% due to coinfection with both IBV and H9N2. RT-PCR analysis of tissue samples and cloacal and tracheal swabs collected from 183 broiler farms revealed that 33.33% were positive for IBV and 34.97% for H9N2. Coinfection by IBV and H9N2 was detected in 12.57% of cases, peaking at 17% in 2022. Co-infected flocks exhibited severe clinical signs and lesions, such as reduced food consumption, diarrhea, and renal issues. The predominant lesions were in the respiratory tract, affecting 91.26% of infected broilers. Additionally, among the 183 flocks, 50 farms that tested positive for IBV infection were randomly selected from the seven regions of Morocco for further investigation of other respiratory pathogens, including Mycoplasma gallisepticum (MG), Mycoplasma synoviae (MS), and infectious laryngotracheitis (ILT), using real-time RT-PCR. Detection rates for these pathogens were 26% for MG, 30% for MS, 4% for ILTv (vaccine strain), and 18% for ILTw (wild strain). Detection rates for single, dual, triple, and quadruple infections were 34%, 42%, 18%, and 4%, respectively. The most common dual and triple coinfections were IBV + H9N2 (14%) and IBV + MG + MS (10%). Phylogenetic analysis of the S gene identified two main IBV genotypes, namely, 793B and D181, with the latter being a strain circulating for the first time in Moroccan poultry. This underscores the urgent need to establish surveillance systems to track pathogen circulation and implement strategies to control virus spread, ensuring the protection of animals and public health.

Under commercial conditions during a respiratory challenge, birds fed 25 mg Hydroxytyrosol (HT)/kg of feed had higher body weight (BW) (p=0.02) and BW gain (BWG) (p=0.02) compared with birds fed 50 mg HT/kg of feed from 1 to 20 days. Over the entire period (40 days), HT affected BW, BWG, and feed conversion ratio (FCR) (p≤0.01), whereas feed intake (FI) and viability were not affected. Broilers fed 25 mg HT/kg of feed showed the highest BW and BWG (p=0.01), while the birds fed 10 mg HT/kg of feed showed the best feed conversion ratio (FCR) (p=0.004). RT-PCR analysis of throat swabs of dead animals and litter revealed the presence of infectious bronchitis virus (IBV) and low pathogenic avian influenza (LPAI) H9N2 in chickens treated and untreated with HT. In vitro assays indicated that HT reduced H9N2 infectivity after 24 h at concentrations as low as 0.01 mg/mL. In the in ovo model, HT concentrations ≥1 mg/mL were well tolerated and were associated with fewer typical IBV macroscopic lesions (dwarfism or hemorrhage) compared with the positive control.