Porcine enteric disease caused by Clostridium difficile and Clostridium perfringens: Epidemiology, pathogenesis and immunity

Clostridium difficile and Clostridium perfringens are among the most common agents of enteric disease in both humans and domestic animals. The former continues to increase in prevalence and diseases caused by the latter persist. Infection with a recently emerged hypervirulent strain (NAP1/027/III) of C. difficile is increasingly common and serious sequelae and fatalities are much more common in these patients. In neonatal piglets, C. difficile infection (CDI) has become a common occurrence. Historically, isolation of C. perfringens type A from patients with enteric disease has been considered inconsequential due to its presence in the normal intestine and to the mild nature of disease syndromes such as porcine enteritis. However, both CDI and type A disease cause losses to the swine industry and pigs have been implicated as a possible source of C. difficile for infection in humans. We investigated the epidemiology and pathogenesis of porcine CDI, and immunity against porcine CDI and type A enteritis. The occurrence of CDI in integrated swine production facilities was most common in neonatal pigs. Infection in sows was rare, and finisher pigs were culture negative. All C. difficile strains were ribotype 078. Hypervirulent strain NAP1/027/TTIII was more virulent in neonatal pigs than both a historic human historic human strain and a porcine strain with toxin producing potential similar to ribotype 027 strains. Inoculation of anti-microbial-treated adolescent pigs with NAP1/027/III did not cause disease. Ingra-gastric inoculation of pigs with purified TcdA resulted in severe small intestine damage which is uncharacteristic of natural disease; effects of TcdB were minimal. Passive immunization of piglets against C. difficile TcdA or C. perfringens type A alpha (CPA) and beta 2 (CPB2) toxins did not prevent disease.