Symptomless Plasmodium vivax parasitemias and malaria eradication in Santa Catarina State, Brazil

• Published in: Revista da Sociedade Brasileira de Medicina Tropical
• Main Authors: S. Avery Jones, Joaquim Alves Ferreira Neto
• Format: Article in Journal/Newspaper
• Language: English; Spanish; Portuguese
• Published: Sociedade Brasileira de Medicina Tropical (SBMT) 1971
• Subjects: Arctic medicine. Tropical medicine; RC955-962; Arctic
• Online Access: https://doi.org/10.1590/S0037-86821971000100003; https://doaj.org/article/4bf64fdb687a452c90a494401149b318

Thirty-nine symptomless carriers of P. vivax parasites in the blood gave blood films at monthly intervals for four to six months during the non- transmission season. It was found that parasitaemias can continue for many months. Thirteen of those studied relapsed with symptoms and were treated with chloroquine at a dosage of 600 mg for adults with proportionate doses for children. Of these nine relapsed silently while under observation: a symptomless relapse rate of approximately 70 per cent. One case had symptoms attributable to malaria close to the time of the original survey (the day before). Of the remaining 38 asymptomatic parasite carriers four showed microgametocytes in a density that suggested a potentially high infectivity and six showed microgametocytes in a density suggesting a potentially low to moderate infectivity for mosquito vectors. There was thus a proportion of one smptomatic case of malaria to 10 potentially infective symptomless parasite carriers. Because they feel no need to seek treatment, such persons may form an important reservoir of infection when vectors cannot be fully controlled by spraying. Some possible methods of dealing with such situations are discussed.