Abstract: Streptococcus equi subsp. zooepidemicus infection of pigs leads to shedding in feces and a carrier state
In 2019, Streptococcus equi subsp. zooepidemicus was recognized as an emerging pathogen of swine, associated with sudden deaths, increased abortion rates and septicaemia. Limited data is available regarding this disease in pigs. The objectives of this study were to clarify clinical progression, pathogen shedding, transmission, gross and microscopic lesions following infection in pigs. Six-weeks old pigs were inoculated with either S. zooepidemicus sequence type 194 (inoculated, n = 6) or sham inoculated with sterile culture broth (sentinels, n = 4). Animals were housed in the same room, in two pens 2 m apart. Pigs were monitored twice daily for clinical signs, and rectal, nasal and oral swabs were collected once daily. A full necropsy was performed if welfare was a concern, or at 5 days post-inoculation (dpi). All sentinels remained disease free and their samples tested negative for the pathogen of interest. All inoculated pigs developed fever within 8 hours of inoculation, and severe disease was observed after 2 dpi. A total of 4/6 inoculated pigs developed clinical signs that compromised animal welfare and were euthanized. Nasal swabs (15/23), followed by rectal swabs (9/23) yield the highest number of positive ante-mortem samples. Clinically healthy, inoculated pigs had detectable levels of S. zooepidemicus in rectal and nasal swabs. Reactive submandibular lymph nodes, kidney petechiae and splenomegaly were found in 6/6 inoculated pigs. This data suggests that subclinically infected pigs may spread the pathogen through nasal secretions and feces. Direct contact seems to be required for transmission. This article is protected by copyright. All rights reserved.
Costa M, Harding J, Huang Y, Nosach R. Streptococcus equi subsp. zooepidemicus infection of pigs leads to shedding in feces and a carrier state. Transbound Emerg Dis. 2022 Feb. https://doi.org/10.1111/tbed.14481