Respiratory and intestinal zoonotic cryptosporidiosis in symptomatic domestic pigeons (Columba livia domestica) in Tabriz, Iran.

Background: Domestic pigeons (Columba livia domestica) are the oldest domesticated birds worldwide, harboring many zoonotic parasites and posing potential public health threats.

Aims: To investigate cryptosporidiosis in domestic pigeons in Tabriz, Iran, 100 privately owned pigeons presenting weight loss and diarrhea were tested for Cryptosporidium spp. through parasitological, histopathological, and molecular tests.

Methods: Modified Ziehl-Neelsen-stained fecal smears and histological sections of the trachea and small intestine were examined microscopically. Genomic DNA of fecal and tracheal specimens was examined by nested conventional PCR targeting 18S rDNA, followed by Sanger sequencing of histopathology-confirmed samples and phylogenetic analyses.

Results: All pigeons were positive at PCR in their feces and trachea. Oocysts similar to the size of Cryptosporidium species were observed in stained fecal smears of 62% of pigeons. At the histopathological examination, Cryptosporidium-organisms were observed on the apical epithelial surfaces of the small intestine in 84% and trachea in 78% of pigeons. In 23 pigeons, simultaneous tracheal and intestinal cryptosporidiosis was determined. The lesions in affected tracheas and small intestines included hyperemia, villous atrophy and fusion, dilatation of intestinal crypts, irregular epithelial hyperplasia, and sloughing. Diffused mixed inflammatory cell infiltration in the lamina propria was observed, with dominant lymphocytes, plasma cells, and lower numbers of heterophils. Consensus sequences of detected parasites revealed infection with Cryptosporidium parvum and Cryptosporidium meleagridis.

Conclusion: Considering the high frequency of cryptosporidiosis reported here in symptomatic birds and that both identified Cryptosporidium species are zoonotic parasites, findings claim a public health risk assessment of this species of animals.