Factors associated with recurrent Plasmodium vivax malaria in Porto Velho, Rondônia State, Brazil, 2009

Abstract

This open retrospective cohort study aimed to describe the incidence of recurrent Plasmodium vivax malaria and associated factors in Porto Velho, Rondônia State, Brazil, in 2009. Data were collected from the National Information System for Malaria Epidemiological Surveillance. There were 23,365 reported P. vivax malaria cases in 2009, 23% of which were classified as relapses. Incidence density of P. vivax recurrence was 45.1/100 patient-years, mostly occurring between the 4th and 13th week after initiating treatment. Male gender, shorter time since onset of symptoms, and higher parasitemia in the initial infection increased the risk of relapse during the year, with a 10% reduction in relative risk for longer symptoms and 11% and 15% increases in relative risk for males and higher initial parasitemia, respectively. However, the results show low clinical relevance for these associations, thereby limiting their applicability to decision-making at the public health level.

Fixed-Dose Artesunate–Amodiaquine Combination vs Chloroquine for Treatment of Uncomplicated Blood Stage P. vivax Infection in the Brazilian Amazon: An Open-Label Randomized, Controlled Trial

“…Despite this caveat, we believe the observed late recurrences indicate the existence of low-grade resistance to CQ, which would suppress but not completely eliminate circulating parasites [12]. This is based on 2 important assumptions: very low risk of reinfection, as most patients (90.5%) resided in urban areas with no active malaria transmission [23], and negligible contribution of relapses, which usually occur after day 35 in the region [32, 45, 46]. …”

Plasmodium vivax Landscape in Brazil: Scenario and Challenges

“…Using routine surveillance data, the number of P. vivax episodes per person per year was evaluated for 2011 to show that from 23,365 reported episodes at least 23% could be classified as possible relapses. In this study, the number of episodes per person varied from one to more than seven,30 despite regular prescription of primaquine. The median time reported from the first episode to first recurrence was 65 days, longer than expected, and the interval to subsequent episodes tended to decrease progressively 30.…”

“…In this study, the number of episodes per person varied from one to more than seven,30 despite regular prescription of primaquine. The median time reported from the first episode to first recurrence was 65 days, longer than expected, and the interval to subsequent episodes tended to decrease progressively 30. However, the NMCP operational definition classifies episodes occurring within 60 days as relapses, leading to possible missed relapses that occur with longer intervals as well as to inappropriate classification as reinfection and recrudescence can also be an important cause of repeated episodes within this interval range.…”

Tafenoquine and its potential in the treatment and relapse prevention of <em>Plasmodium vivax</em> malaria: the evidence to date

“… 19 Studies have also identified that the events of vivax relapse are associated with patient and parasite factors. 20 , 21 …”