Genotype profiling of Mycobacterium avium subspecies paratuberculosis isolates recovered from feces and milk of Iranian bovine, ovine and caprine hosts, are the sheep (S) type strains mysteriously overlooked in Iran

Mycobacterium avium subspecies paratuberculosis (MAP) is known worldwide for its role in causing paratuberculosis (Ptb), a chronic incurable intestinal tract infection of ruminants. Concerns remain in place as the elusive MAP epidemiology and its potential zoonotic nature continue to challenge veterinarians across the world. Almost half a century since its initial reports, Ptb is still not a notifiable disease in Iran leading to the unfortunate lack of a public-funded control scheme. We undertook this study to extend our knowledge of the MAP population genetic in diverse hosts in Iran. During seven months, 35 MAP isolates collected from milk and feces obtained from sheep, goat and cattle originating 8 provinces plus a further eleven archived MAP isolates were genetically interrogated. The Collins strategy was conducted on examined isolates to differentiate between cattle and sheep types of MAP bacteria. The study was further expanded by RFLP-IS900 analysis using PstI in search for genetic diversity. The findings of Collins strategy showed that all animal species covered by the study were exclusively infected by 'cattle' strains. In genotyping, on the other hand, RFLP-IS900 analysis yielded 10 largely similar genotypes with five of them infecting multiple hosts. Nevertheless, no trace of varying profiles was detected in individual farms and conspecifics. These data, taken together with earlier observations by others, raise the question of the mysterious absence of sheep-type strains in Iran. Circulation of highly similar strains in Iranian farm ruminants might be an indication of a homogenic MAP population with a tendency for diversification started only recently. The extent of temporal and spatial characteristics of such diversification is still unclear and left for future works.