The neurotropism of the APMVs in 1-day old chicks also was evaluated by immunohistochemistry analysis of brain tissue harvested on day 3 (Fig. 5) . Viral antigens were detected in the brain tissues that had been infected with APMV-1 strain BC and APMV-3, confirming the replication of the two viruses in chicken brain. Our result showed a more extensive distribution of viral antigens in brain tissue infected with BC compared to APMV-3. In contrast, presence of viral antigens was not detected in the brain tissues that had been infected with the other APMVs (Fig. 5) .