Neonatal porcine diarrhoea

Diarrhoea in newborn piglets is an old but still relevant problem in pig production globally. During the last decades, reports from a number of countries describe problems with neonatal porcine diarrhoea (NPD) despite the use of previously effective preventive measures. The aim of this thesis was to investigate and characterise the problem with NPD in Swedish piglet-producing herds. The magnitude of the problem was estimated by a questionnaire study distributed to 170 randomly selected herds. A response rate of 58% was achieved. The total herd-level prevalence of NPD, including herds with sporadic cases, was 79.6%, indicating that NPD is a substantial problem. Ten herds affected by NPD were selected for in-depth studies on the potential causes of the diarrhoea. From each herd, five diarrhoeic and two healthy control piglets were selected. The piglets were blood-sampled for analysis of serum ɣ-globulin, and thereafter euthanized and necropsied. The intestines were sampled for histopathology, virology, and bacteriology. There was no difference in serum ɣ-globulin concentration between diarrhoeic and non-diarrhoeic piglets and pathological lesions in the intestines were generally mild. Porcine enterotoxigenic Escherichia (E.) coli was only found in two piglets. Further, extended virulence gene profiling did not suggest involvement of other diarrhoeagenic pathotypes of E. coli. Clostridium (C.) perfringens type C was not detected, and neither C. perfringens type A nor C. difficile could be related to the diarrhoea. Furthermore, no protozoa such as Cystoisospora suis were observed in the intestinal mucosa. By viral metagenomics analyses of intestinal samples, the only previously well-established porcine enteropathogen found was rotavirus that was present in two herds. Otherwise, the data did not suggest involvement of previously known viruses. The only consistent finding associated with diarrhoea was small intestinal colonisation by Enterococcus (E.) hirae. Enteroadherent E. hirae was detected in 60% of the diarrhoeic piglets from six of the herds and was associated with small intestinal mucosal lesions in more than 50% of the cases (10/18). Thus, our results show that diarrhoea in newborn piglets may have other causes than the well-established pathogens previously associated with NPD and a potential involvement of E. hirae is suggested.