Evidence for the transfer of macrolide-resistant microorganisms from animals to humans has been scant,[40][41] and most evidence shows that pathogens of concern in human populations originated in humans and are maintained there, with rare cases of transference to humans. Macrolides are also extremely useful in the effective treatment of some Mycoplasma species in poultry, Lawsonia in pigs, respiratory tract infections in cattle and in some circumstances, lameness in sheep.[3]