Visceral leishmaniasis caused by Leishmania infantum is a widespread and potentially fatal zoonotic disease. Domestic dogs, the major reservoir for human L infantum infection, transfer it to humans via sandflies. Allopurinol, the main drug used for treatment, is used alone or in conjunction with other drugs. Most dogs experience clinical remission but do not have complete parasite elimination.
This study demonstrated that, in dogs suffering from relapse of leishmaniasis, 3 forms of the parasite displayed allopurinol resistance. Dogs infected with an allopurinol-resistant L infantum strain pose a significant risk to humans and other dogs.