Diarrhea-induced Changes in Chemical Phenotypes of Enteric Neural Structures in the Pig Are Not Sufficient to Discriminate between the Viral and Bacterial Etiology of the Disease

The present study was aimed at disclosing whether changes in the chemical coding of neural structures observed within the intestinal wall may be of diagnostic importance for distinguishing between the viral vs. bacterial etiology of a naturally acquired diarrhea in piglets. Sections from the jejunum of pigs with clinically and microbiologically diagnosed viral (V group) and bacterial diarrhea (B group) were labelled by means of indirect immunofluorescence technique. Antibodies against galanin (GAL), somatostatin (SOM), substance P (SP) and vasoactive intestinal polypeptide (VIP) were used to compare the chemical coding of enteric nervous structures in age-matched, clinically healthy control animals (C group) with those observed in specimens from the diarrhea-suffering littermates. While in the healthy animals, the distribution pattern of nerve fibres/intrinsic neurons exhibiting substances studied virtually resembled that described elsewhere, both, viral and bacterial diarrhea induced a dramatic increase in the number of neural structures (both nerve fibres and neuronal cell bodies) exhibiting GAL and SP. An increase observed in the number/density of elements containing SOM or VIP was less pronounced. It should be stressed that both kinds of changes observed as well as their intensity were very similar in V and B groups of animals making a distinction between the viral or bacterial diarrhea virtually impossible. Thus, although the procedure described may be of importance for better understanding the neural aspects of the diarrhea-induced changes in, e.g., intestinal motility, water resorbtion or changed epithelial secretion, this technique per se appears to be not sufficient for clear-cut diagnosis of the diarrhea etiology.