Molecular, pathological and immunohistochemical investigation of Helicobacteraceae in the abomasum of dairy cattle and sheep in Northern Italy.

Although several Helicobacter species have been associated with gastric disease in humans and animals, their role in domestic ruminants is still unclear. This study aimed to investigate the prevalence of H. pylori, "Candidatus H. bovis" and other Helicobacteraceae in the abomasum of dairy cattle and sheep reared in Northern Italy, to shed light on their role as potential reservoir of H. pylori for humans and to evaluate the involvement of Helicobacter spp. in the gastric pathology of these animal species. Abomasa from 25 dairy cows and 24 sheep were collected at slaughter. Following macroscopic examination, samples of fundic and pyloric mucosa were analysed by a screening PCR for Helicobacteraceae, followed by specific PCRs (H. pylori, "Candidatus H. bovis", and Wolinella spp.), histological examination, and immunohistochemistry for Helicobacter spp. Overall, 96 % of the bovine and 42 % of the ovine abomasa tested positive for Helicobacteraceae. No samples tested positive for H. pylori, while 68 % of bovine samples tested positive for "Candidatus H. bovis", mostly in the pyloric mucosa. Immunohistochemistry showed colonisation by Helicobacter spp. only in the pyloric glands of 11 bovine abomasa (44 %), while in ovine abomasa colonisation was not detected. Our results confirmed that "Candidatus H. bovis" is the most common Helicobacteraceae in the bovine abomasum and specifically colonises bovine pyloric glands. No association was found between Helicobacter spp. infection status and abomasal inflammation, suggesting a high degree of adaptation to the bovine host. The role of cattle and sheep as potential source of H. pylori for humans appears to be negligible.