Risk factors associated to Streptococcus suis cases in swine farms in Spain

Abstract

Abstract Background: Streptococcus suis, an early colonizer of the upper respiratory tract, can cause the S. suis-associated disease, a major infection characterized by meningitis, polyarthritis, and acute death, in piglets mainly around weaning age. However, little is known about the factors responsible for triggering the disease. Therefore, a longitudinal study was carried out, in which a total of six batches from two Spanish swine farms with S. suis problems were repeatedly examined, once in the farrowing unit and twice in the weaning unit. Results: Potential risk factors evaluated included: a) concomitant pathogens such as porcine reproductive respiratory syndrome virus (PRRSV), porcine circovirus type 2, swine influenza virus, and Glaesserella parasuis; b) biomarkers associated to stress (cortisol), inflammation (haptoglobin), and oxidative status (hydrogen peroxide); c) farm environmental factors such as temperature, relative humidity, CO2, and temperature-humidity index; and d) parity and S. suis presence in sows. Three models were built to study the effect of these variables, including two to assess the risk factors involved in the subsequent development of the disease. Presence of S. suis problems during the study was confirmed by its isolation in lesions in both farms. Risk factors for S. suis disease included PRRSV coinfection at weaning (Odds ratio (OR) = 6.69), sow parity (OR = 0.71), haptoglobin before weaning (OR = 1.01), and relative humidity in the farrowing unit as well as temperature at weaning (OR = 1.11 and 0.13, respectively). Conclusions: This study confirms the multifactorial nature of S. suis-associated disease, for which both environmental factors and factors related to the host seem to be involved in the development of the disease.