Pathogenicity and horizontal transmission studies of caprine parainfluenza virus type 3 JS2013 strain in goats

Parainfluenza virus type 3 (PIV3) is one of the most important viral respiratory pathogens for humans and for many animals, but goat infection has been rarely reported. In 2014, one novel PIV3 strain was first isolated from goats suffered respiratory diseases in Jiangsu and Anhui provinces of eastern China and named as caprine PIV3 (CPIV3) JS2013. In order to systematically evaluate the pathogenicity and horizontal transmission ability of this new virus, experimental infection of goats with the CPIV3 strain was done. The virus-inoculated goats (challenge control (CC) group) displayed coughing and nasal discharges from 3 days post infection (dpi) and lasted for about 2 weeks. Two goats in group CC showed fever between 7 and 12 dpi. As detected by a TaqMan real time quantitative RT-PCR (qRT-PCR), viremia was detected during 3-11 dpi, peaked at 6 dpi; and virus shedding from nasal discharge and faeces were confirmed during 3-21 dpi and 4-21 dpi, respectively. Virus-specific HI antibodies and neutralizing antibodies (NAs) became positive since 7 dpi and 14 dpi; peaked at 14 dpi and 28 dpi, respectively; and lasted at least 70 days. Pathological lesions were mainly found on the lungs and tracheas. In addition, viruses were also detected in part of the tracheal secretion and lung samples, and the viral load in tracheal secretion was higher than that in lungs. Goats in horizontal infected group (hCC, kept in different cages in the same house with CC group) showed to be horizontally infected, with slightly milder clinical signs and pathological changes; and slightly shorter period of viremia and virus shedding. This was the first report of the detailed pathogenicity characterization of the novel CPIV3 and demonstrated its horizontal transmission ability. The results would be helpful for further studies on the preventive and control strategies for CPIV3 infections.