Slow clearance of Plasmodium vivax with chloroquine amongst children younger than six months of age in the Brazilian Amazon

Plasmodium vivax is the most widespread parasite causing malaria, beingespecially prevalent in the Americas and Southeast Asia. Children are one of themost affected populations, especially in highly endemic areas. However, there arefew studies evaluating the therapeutic response of infants with vivax malaria.This study retrospectively evaluated the parasitaemia clearance in childrendiagnosed with vivax malaria during the first five days of exclusive treatmentwith chloroquine (CQ). Infants aged less than six months old had a significantlyslower parasitaemia clearance time compared to the group of infants and childrenbetween six months and 12 years old (Kaplan-Meier survival analysis; Wilcoxontest; p = 0.004). The impaired clearance of parasitaemia in younger children withvivax malaria is shown for the first time in Latin America. It is speculated thatCQ pharmacokinetics in young children with vivax malaria is distinct, but thisspecific population may also allow the detection of CQ-resistant parasites duringfollow-up, due to the lack of previous immunity.