Pruritus or itch is associated with malaria infection and/or chloroquine chemotherapy. This study examined the relationship between parasitaemia and chloroquine (CQ) on body scratching (BS) in healthy (un-infected) and malaria-infected rats. The malaria parasite induced a significant (p< 0.001) increase in body scratching (28.3 ± 4.6) compared to un-infected rats (7.7 ± 1.0). Intraperitoneal administration of CQ (20 mg/kg, i.p) increased the frequency of body scratching (28.7 ± 8.1) compared to control animals (7.5 ± 1.0, p < 0.001). The -opioid receptor antagonist, naltrexone (0.25mg/kg i.p given 15 minutes prior) blocked both parasite and CQ (20mg/kg)–induced body scratching. In morphine tolerant rats, the frequency of BS was significantly reduced (12.7 ± 3.7, p