3.1 Detection of the causative agent(s) causing the death of goats
In November 2015, most of black goats showing clinical signs of possible PRV infection were reported in a farm in Yunnan, China. Subsequently, a detailed survey was conducted, the symptoms in these goats included high fever, appetite loss, skin itch and fidgety with no ages and sexes limitation (Fig. 1A-B ). Additionally, some of the ill goats displayed severe diarrhea (Fig. 1C ), and all of these goats died eventually. The pathological examination showed the occurrence of pneumonia hemorrhage, lymphadenopathy syndrome with hemorrhage, brain hyperemia and hemorrhage in dead goats (Fig. 1D ).
Further investigation revealed that these goats were fed together with fatted pigs only by the separation of a wall, while all pigs in this farm had been immunized with the PRV attenuated live vaccine (Bartha-K61 strain) at the development stage of piglets. Furthermore, all animals were fed by the same breeder.
To explore the possible causative agent(s) leading to the death of goats in this case, the viral nucleic acids were extracted from brain tissues of the dead goats, PCR and RT-PCR methods were performed to detect the presence of pathogens such as PRV, RV, and GEAV. Interestingly, the specimens presented PRV positive while RV and GEAV negative. Furthermore, the treatment of these diseased goats with antibacterial drugs, such as Cefatriaxone and Sulfadiazine, had poor therapeutic effect. Meanwhile, 10 serum specimens from the fattening pigs raised near the goats were positive for PRV gE antibody, while only 1 of 16 fecal samples from these pigs were tested positive for PRV by PCR method (data not shown). Thus, we concluded that PRV infection was the leading cause resulting in the death of goats.