Cases of high mortality in cull sows and feeder pigs associated with Streptococcus equi subsp. zooepidemicus septicemia

Abstract

Investigations of 2 cases of high mortality in cull sows and feeder pigs from a buying station in Ohio and cull sows at an abattoir in Tennessee were conducted at the Iowa State University Veterinary Diagnostic Laboratory. The animals were presented as weak, lethargic, and some with high fever. Rapidly escalating mortality was reported to be as high as 30–50% within groups at the buying station over 8–10 d, and 30–40% over 5–7 d at the abattoir. Splenomegaly and red lymph nodes were the most consistent macroscopic findings, with scant fibrinous polyserositis observed in one sow. The microscopic lesions of vasculitis, fibrin thrombi, fibrinosuppurative polyserositis, and intralesional bacteria were consistent with acute bacterial septicemia. Bacterial culture isolated Streptococcus equi subsp. zooepidemicus ( S. zooepidemicus) from multiple organs, including spleen, lung, and kidney. PCR tests were negative for African swine fever virus, classical swine fever virus, Erysipelothrix rhusiopathiae, porcine reproductive and respiratory syndrome virus, porcine circovirus 2, and Salmonella spp. Porcine circovirus 3 was inconsistently detected at low levels by PCR, with a lack of associated lesions. Next-generation sequencing identified S. zooepidemicus and porcine partetravirus in the serum sample of the feeder pig from the buying station. Phylogenetic analysis of the szP gene indicated that the S. zooepidemicus isolates from Ohio and Tennessee are in genotype VI. We conclude that the cause of these high mortality events in swine was S. zooepidemicus septicemia.

Bacterin Vaccination Provides Insufficient Protection Against Streptococcus equi Subspecies zooepidemicus Infection in Pigs

“…Pigs rapidly develop depression, anorexia, and high fever. Field mortality rates reach 30–50% ( 6 ). Experimental replication of disease revealed the susceptibility of healthy, conventionally raised pigs to SEZ which results in 100% mortality within 72 h of challenge ( 7 ).…”

“…It has been infrequently associated with disease in pigs in North America (3); however, in 2019, SEZ was isolated from swine that died during high mortality events in the USA and Canada (4)(5)(6). Pigs developed weakness, lethargy, high fever, and mortality rates of 30-50% over 5-10 days following infection (6). Initial investigation into the pathogenesis of mortality event isolates revealed that SEZ is capable of causing disease in healthy, conventionally raised pigs and experimental exposure resulted in 100% mortality within 72 h post-challenge (7).…”

“…Streptococcus equi subspecies zooepidemicus (SEZ) is a pathogen of horses and other mammals, including humans ( 1 , 2 ). It has been infrequently associated with disease in pigs in North America ( 3 ); however, in 2019, SEZ was isolated from swine that died during high mortality events in the USA and Canada ( 4 – 6 ). Pigs developed weakness, lethargy, high fever, and mortality rates of 30–50% over 5–10 days following infection ( 6 ).…”

Occurrence and Antimicrobial Susceptibility Profiles of Streptococcus equi subsp. zooepidemicus Strains Isolated from Mares with Fertility Problems

“…Streptococcus equi subsp. zooepidemicus ( S. zooepidemicus ), is a β-hemolytic streptococcus belonging to the Lancefield group C. It is a rare human pathogen, but it is commonly isolated from bacterial infections in a wide range of animal species like horses [ 1 ], dogs [ 2 , 3 ], felines [ 4 , 5 , 6 ], swine [ 7 , 8 ], guinea pigs [ 9 ], ruminants [ 10 , 11 ], camelids [ 12 ] and non-human primates [ 13 ].…”

Visualization and application of disease diagnosis codes for population health management using porcine diseases as a model

“…zooepidemicus . 10 The ability to internally validate Dx code alignment is possible. For example, respiratory and digestive systems represented 61.4% of the overall Dx code assignments; body system can be automatically implied or can have additional validation by confirming the presence of compatible lesion codes such as bronchopneumonia or enteritis, both of which are encountered commonly.…”