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Secondary infection with Streptococcus suis serotype 7 increases the virulence of highly pathogenic porcine reproductive and respiratory syndrome virus in pigs.

Xu M, Wang S, Li L, Lei L, Liu Y, Shi W, Wu J, Li L, Rong F, Xu M, Sun G, Xiang H, Cai X - Virol. J. (2010)

Bottom Line: To determine whether PRRSV-SS7 coinfection was the cause of the PHFS outbreak, we evaluated the pathogenicity of PRRSV and/or SS7 in a pig model of single and mixed infection.Respiratory disease, diarrhea, and anorexia were observed in all infected pigs.HP-PRRSV infection increased susceptibility to SS7 infection, and coinfection of HP-PRRSV with SS7 significantly increased the pathogenicity of SS7 to pigs.

View Article: PubMed Central - HTML - PubMed

Affiliation: Division of Swine Infectious Diseases, National Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, CAAS, Harbin, China.

ABSTRACT

Background: Porcine reproductive and respiratory syndrome virus (PRRSV) and Streptococcus suis are common pathogens in pigs. In samples collected during the porcine high fever syndrome (PHFS) outbreak in many parts of China, PRRSV and S. suis serotype 7 (SS7) have always been isolated together. To determine whether PRRSV-SS7 coinfection was the cause of the PHFS outbreak, we evaluated the pathogenicity of PRRSV and/or SS7 in a pig model of single and mixed infection.

Results: Respiratory disease, diarrhea, and anorexia were observed in all infected pigs. Signs of central nervous system (CNS) disease were observed in the highly pathogenic PRRSV (HP-PRRSV)-infected pigs (4/12) and the coinfected pigs (8/10); however, the symptoms of the coinfected pigs were clearly more severe than those of the HP-PRRSV-infected pigs. The mortality rate was significantly higher in the coinfected pigs (8/10) than in the HP-PRRSV- (2/12) and SS7-infected pigs (0/10). The deceased pigs of the coinfected group had symptoms typical of PHFS, such as high fever, anorexia, and red coloration of the ears and the body. The isolation rates of HP-PRRSV and SS7 were higher and the lesion severity was greater in the coinfected pigs than in monoinfected pigs.

Conclusion: HP-PRRSV infection increased susceptibility to SS7 infection, and coinfection of HP-PRRSV with SS7 significantly increased the pathogenicity of SS7 to pigs.

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Macroscopic lesions in the coinfected group. (a) Kidney and pelvic hemorrhage; (b) Trichocardia and hydropericardium; (c) Stomach hemorrhage; (d) Bacterial infection in the thoracic cavity; (e) Lymph node intumescentia and hemorrhage; (f) Lung consolidation.
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Figure 2: Macroscopic lesions in the coinfected group. (a) Kidney and pelvic hemorrhage; (b) Trichocardia and hydropericardium; (c) Stomach hemorrhage; (d) Bacterial infection in the thoracic cavity; (e) Lymph node intumescentia and hemorrhage; (f) Lung consolidation.

Mentions: No macroscopic lesions were observed in the control pigs. The pigs in HP-PRRSV-infected and coinfected groups developed macroscopic brain lesions mainly due to meningitis, meningeal congestion and hemorrhage, swallowed gyri, and brain tissue colliquation. The lung lesions showed multifocal distribution. The affected lung parenchyma appeared mottled, tan, and rubbery, and failed to collapse. Several pigs in the coinfected group had pleuritis or purulent airway exudates. The severity of the lung lesions in SS7-infected pigs was lower than that in HP-PRRSV-infected and coinfected pigs. Pigs in all the 3 experimental groups showed lymph node lesions, including intumescentia and hemorrhage. The scores of lung and lymph nodes were evaluated in detail at necropsy, and are summarized in Figure 1. Kidney lesions in HP-PRRSV-infected and coinfected pigs included punctiform hemorrhage in the cortex, inner hemorrhage, shrunken or disappeared substantia medullaris, and change of color to cinnamon. Macroscopic lesions were also detected in other organs in HP-PRRSV-infected and coinfected pigs; these pigs had grayish-white spots in the liver, and trichocardia, hydrops pericardial, tonsillitis, hemorrhage of the stomach fundus, and spleen infarcts. The SS7-infected pigs had macroscopic lesions mainly in the lungs and lymph nodes with few lesions in other organs. Peritonitis was observed in SS7-infected pigs (2/10) and coinfected pigs (4/10). There was no evidence of arthritis in any of the pigs. The representative images of the macroscopic lesions are presented in Figure 2.


Secondary infection with Streptococcus suis serotype 7 increases the virulence of highly pathogenic porcine reproductive and respiratory syndrome virus in pigs.

Xu M, Wang S, Li L, Lei L, Liu Y, Shi W, Wu J, Li L, Rong F, Xu M, Sun G, Xiang H, Cai X - Virol. J. (2010)

Macroscopic lesions in the coinfected group. (a) Kidney and pelvic hemorrhage; (b) Trichocardia and hydropericardium; (c) Stomach hemorrhage; (d) Bacterial infection in the thoracic cavity; (e) Lymph node intumescentia and hemorrhage; (f) Lung consolidation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2927530&req=5

Figure 2: Macroscopic lesions in the coinfected group. (a) Kidney and pelvic hemorrhage; (b) Trichocardia and hydropericardium; (c) Stomach hemorrhage; (d) Bacterial infection in the thoracic cavity; (e) Lymph node intumescentia and hemorrhage; (f) Lung consolidation.
Mentions: No macroscopic lesions were observed in the control pigs. The pigs in HP-PRRSV-infected and coinfected groups developed macroscopic brain lesions mainly due to meningitis, meningeal congestion and hemorrhage, swallowed gyri, and brain tissue colliquation. The lung lesions showed multifocal distribution. The affected lung parenchyma appeared mottled, tan, and rubbery, and failed to collapse. Several pigs in the coinfected group had pleuritis or purulent airway exudates. The severity of the lung lesions in SS7-infected pigs was lower than that in HP-PRRSV-infected and coinfected pigs. Pigs in all the 3 experimental groups showed lymph node lesions, including intumescentia and hemorrhage. The scores of lung and lymph nodes were evaluated in detail at necropsy, and are summarized in Figure 1. Kidney lesions in HP-PRRSV-infected and coinfected pigs included punctiform hemorrhage in the cortex, inner hemorrhage, shrunken or disappeared substantia medullaris, and change of color to cinnamon. Macroscopic lesions were also detected in other organs in HP-PRRSV-infected and coinfected pigs; these pigs had grayish-white spots in the liver, and trichocardia, hydrops pericardial, tonsillitis, hemorrhage of the stomach fundus, and spleen infarcts. The SS7-infected pigs had macroscopic lesions mainly in the lungs and lymph nodes with few lesions in other organs. Peritonitis was observed in SS7-infected pigs (2/10) and coinfected pigs (4/10). There was no evidence of arthritis in any of the pigs. The representative images of the macroscopic lesions are presented in Figure 2.

Bottom Line: To determine whether PRRSV-SS7 coinfection was the cause of the PHFS outbreak, we evaluated the pathogenicity of PRRSV and/or SS7 in a pig model of single and mixed infection.Respiratory disease, diarrhea, and anorexia were observed in all infected pigs.HP-PRRSV infection increased susceptibility to SS7 infection, and coinfection of HP-PRRSV with SS7 significantly increased the pathogenicity of SS7 to pigs.

View Article: PubMed Central - HTML - PubMed

Affiliation: Division of Swine Infectious Diseases, National Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, CAAS, Harbin, China.

ABSTRACT

Background: Porcine reproductive and respiratory syndrome virus (PRRSV) and Streptococcus suis are common pathogens in pigs. In samples collected during the porcine high fever syndrome (PHFS) outbreak in many parts of China, PRRSV and S. suis serotype 7 (SS7) have always been isolated together. To determine whether PRRSV-SS7 coinfection was the cause of the PHFS outbreak, we evaluated the pathogenicity of PRRSV and/or SS7 in a pig model of single and mixed infection.

Results: Respiratory disease, diarrhea, and anorexia were observed in all infected pigs. Signs of central nervous system (CNS) disease were observed in the highly pathogenic PRRSV (HP-PRRSV)-infected pigs (4/12) and the coinfected pigs (8/10); however, the symptoms of the coinfected pigs were clearly more severe than those of the HP-PRRSV-infected pigs. The mortality rate was significantly higher in the coinfected pigs (8/10) than in the HP-PRRSV- (2/12) and SS7-infected pigs (0/10). The deceased pigs of the coinfected group had symptoms typical of PHFS, such as high fever, anorexia, and red coloration of the ears and the body. The isolation rates of HP-PRRSV and SS7 were higher and the lesion severity was greater in the coinfected pigs than in monoinfected pigs.

Conclusion: HP-PRRSV infection increased susceptibility to SS7 infection, and coinfection of HP-PRRSV with SS7 significantly increased the pathogenicity of SS7 to pigs.

Show MeSH
Related in: MedlinePlus