Immunohistochemical Evidence of Multiple Viral and Bacterial Associations in Caprine Pneumonia in Nigeria: Implications for Vaccines

Caprine pneumonia is a major cause ofeconomic loss and the conventional vaccines are not optimal in protectinggoats. A better understanding of the associations of respiratory pathogens mayhelp improve our knowledge for vaccination to effectively control caprinepneumonia. One hundred and fifty goats (140 pneumonic and 10 normal) wereexamined for various lung pathologies using standard gross and histologictechniques. Antigens of parainfluenza 3 virus (PI3V), respiratory syncytialvirus (RSV) and peste des petits ruminants virus (PPRV) and bacterial antigensof Mannheimia haemolytica (M.haemolytica) and Pasteurella multocida (P.multocida) were demonstrated immunohistochemically in the lungs. The data ofgoats positive and negative for the viral and bacterial antigens were analysedusing descriptive statistics.Viral antigens were detected in 113 (81%) ofthe pneumonic lungs (100 as single, 11 dual and 2 triple). Bacterial antigenswere detected in 120 (86%), M. haemolytica in 47 (34%), P. multocida in 59 (42%) and combinedbacterial antigens in 14 (10%) of the pneumonic lungs. Multiple agents weredetected in 108/140 positive cases; virus-bacterium association was observed in106/108. PPRV antigens alone were observed in 15 cases. PPRV coexisted mostfrequently with M. haemolytica (n=20), P. multocida (n=13), PI3V with P.multocida (n=18), and RSV with M. haemolytica (n=9). The lesions correspondedto cranioventral (n=45), diffuse (n=75), and lobar consolidations (n=20)manifested as fibrinous bronchopneumonia (n=22), suppurative bronchopneumonia(n=20), bronchointerstitial pneumonia (n=61), interstitial pneumonia (n=25) andbronchiolitis (n=12). Thus, multiple infections are involved in pneumonia,hence we must consider combined vaccination strategies incorporating multipleantigens for adequate control of caprine pneumonia.