It is suspected that, on rare occasions, certain animals that
are exposed to MAP can generate a protective immune response
resulting in full clearance of the MAP (28). It is unclear whether
this capacity, if it exists, is restricted to mature animals, or
whether some young animals also have this capability.
In some studies, Jersey and Shorthorn cows have been shown
to have a higher susceptibility for paratuberculosis (34,35).
However, these observed differences were confounded by the
differences in these breeds being linked to husbandry practices
in specific regions (herds with these breeds in these particular
studies had worse hygiene). Due to these confounding
circumstances, genetics and breed appear to be minor
factors.