An observational field study of porcine post-weaning diarrhea: clinical and microbiological findings, and fecal pH-measurements as a potential diagnostic tool

Abstract

Background: Recently, in-feed medicinal zinc has been phased out in pig production in the European Union. This makes updated knowledge about porcine post-weaning diarrhea (PWD) crucial. The objectives of the present study were to investigate (i) the clinical presentation of PWD in pigs housed in Danish herds that did not use medicinal zinc, specifically the prevalence of diarrhea and whether PWD was associated to clinical signs of dehydration or altered body temperature; (ii) which microorganism are associated to PWD; and iii) whether measurements of the fecal pH have a potential to be used diagnostically to differentiate between infectious etiologies in cases of PWD.

Results: The prevalence of diarrhea varied considerably between the outbreaks in the nine studied herds (median = 0.58, range = 0.10; 0.94). In a cross-sectional design (n = 923), diarrhea was associated with reduced rectal temperature and alkaline feces. Diarrhea was also associated with observably reduced skin elasticity, possibly indicating dehydration. In both diarrheic case pigs (n = 87) and control pigs (n = 86), the presence of Brachyspira pilosicoli, Clostridium perfringens, Cryptosporidium spp., Cystoisopora suis, enterotoxigenic Escherichia coli, Lawsonia intracellularis, porcine circovirus types 2 and 3, rotavirus A, B, C, and H, Samonella enterica spp. enterica, and Trichuris suis was described. PWD was associated with high levels of enterotoxigenic E. coli shedding (odds ratio versus no E. coli detection = 4.79 [CI 1.14; 12.62]). Diarrhea was associated with high levels of rotavirus A shedding (odds ratio versus no/low rotavirus A = 3.80 [CI 1.33; 7.97]). The association between microbiological findings in diarrheic pigs and fecal pH was negligible.

Conclusions: Enterotoxigenic E. coli was confirmed to be a cause of PWD; however, cases of PWD where enterotoxigenic E. coli was not detected in high levels occurred commonly, and this adds to the increasing evidence suggesting that PWD is not necessarily a result of enteric colibacillosis. Rotaviral enteritis might be a differential diagnosis of PWD. pH-measurements cannot be used to differentiate between differential diagnoses for PWD.

Keywords: Enterotoxigenic Escherichia coli; Pig; Post-weaning diarrhoea; Rectal temperature; Rotavirus; pH.

Fig. 1

Graphical abstract of the methodology applied in an observational field study of post-weaning diarrhea. The illustration was created with BioRender.com. PWD: Post-weaning diarrhea. CHR: The Danish Central Husbandry register

Fig. 2

The true prevalence proportion (with 95% credible interval) of post-weaning diarrhea. Data was collected at the time of initiation of antimicrobial batch medication in nine Danish herds weaning without medicinal zinc

Fig. 3

The color of the non-diarrheic feces (left) and diarrheic feces (n = 400) (right). The data was collected from pigs in outbreaks of post-weaning diarrhea in nine Danish commercial indoor herds weaning without medicinal zinc

Fig. 4

The rectal temperature (°C) of newly weaned pigs (n = 698) sorted by fecal consistencies. The data displayed in the boxplots was collected in outbreaks of post-weaning diarrhea in nine Danish commercial indoor herds weaning without medicinal zinc

Fig. 5

Rectal temperature (°C) of pigs (n = 87) suffering from post-weaning diarrhea sorted by assumed etiology. The data displayed in the boxplots was collected in outbreaks of post-weaning diarrhea in nine Danish commercial indoor herds weaning without medicinal zinc. no infection: Pathogens were not detected or only detected at low level. ETEC: High levels of Enterotoxigenic E. coli. RVA: High Levels of rotavirus A. Salmo: Salmonella enterica

Fig. 6

Number of pigs with single or mixed infections in pigs with and without post-weaning diarrhea. The left panel displays pigs without diarrhea (n = 86), and the right panel displays pigs with diarrhea (n = 87). Values for ETEC were missing for two pigs with diarrhea and two pigs without diarrhea

Fig. 7

The fecal pH versus the dry-matter content in fecal samples from post-weaning pigs (n = 516). The polynomial line with associated confidence interval was smoothed using a third-degree Epanechnikov function. The cut-offs defining the color and shape of the markers in the plot are described in Table 3