Newcastle disease (ND) is an important viral disease that threatens the global poultry industry. The urgent need
for a safe and effective antiviral alternative prompted us to evaluate neem methanolic leaf extract against Newcastle disease
virus (NDv) in broilers. A total of Sixty Cobb chicks (day old) were allocated randomly into 4 equal groups; group A was a
control negative, and group B was a control positive. Groups C and D received a methanolic neem leaf extract (MNLE) in
drinking water for five days at 500 and 1000 μg/kg BW, respectively. At 25th days old, chicks in groups B, C and D were
challenged via the oculonasal route with 0.2 ml of virulent NDv. The use of MNLE in groups C and D significantly reduced
morbidity and mortality as well as the macroscopic and microscopic scoring lesions of all examined organs compared to
the infected untreated group B. The high dose of MNLE (1000 μg/ kg BW; group D) was more efficient and significant in
relieving the clinical and pathological abnormalities caused by ND challenge compared with the low dose (500 μg/ kg BW;
group C).Moreover, positive effects of the herbal treatment on the experimentally ND-infected chickens were evidenced by
reducing viral RNA concentrations in the oropharyngeal swabs at 3, 5, and 7 days post challenge and the infectivity titer
of the virus isolated from the trachea, spleen, and cecal tonsils at 7 days post challenge. In conclusion, the study showed
that MNLE had a positive and helpful role in the control of NDv infection and shedding. So, MNLE could be a source of
inspiration for new alternative antivirals.