Abstract
Background A screening for malaria parasites was conducted with asymptomatic residents in Colombia. Methods A descriptive study was carried out in December 2012 in four municipalities of Urabá region in Colombia. A convenience sample of 400 subjects was selected. Participants responded to a survey regarding epidemiological data and blood samples were taken from capillary blood obtained by finger prick for thick smear, rapid diagnostic test (RDT), and polymerase chain reaction (PCR). Results 399 subjects aged 0.2-98 years were studied (median 22; 221 female (55%)). Episodes of malaria in the last year confirmed by thick film were reported by 47 participants (12%). In 399 samples tested by RDT 4 (1%) were positive (1 with P. falciparum, 3 with P. vivax), and 3 were confirmed by PCR. In 399 thick blood smears examined 5 (1.3%) were positive (2 with P. falciparum, 3 with P. vivax), and 3 were confirmed by PCR. In 227 samples, PCR showed 6 (2.6%) positive samples. The parasitaemia was below 1,440 parasites/μL. The best agreement between diagnoses was found between the RDT and thick blood smears (Kappa = 0.75). Conclusion Plasmodial afebrile infection was found in 2% of the studied population, by three diagnostic methods, in residents from a low endemic malaria region in Colombia.
Highlights
A screening for malaria parasites was conducted with asymptomatic residents in Colombia
Blood smears and rapid diagnostic tests were performed to all subjects; the polymerase chain reaction (PCR) was made in 227 subjects
This study found two negative rapid diagnostic test (RDT) in blood samples that corresponded to subjects with positive thick smears, a situation probably explained by the low parasitaemia or by the fact that because of the presence of parasites that lack pfhrp2 gene the enzyme detected by the RDTs is applied [26]
Summary
A screening for malaria parasites was conducted with asymptomatic residents in Colombia. Plasmodial afebrile infection was found in 2% of the studied population, by three diagnostic methods, in residents from a low endemic malaria region in Colombia. Asymptomatic infections by Plasmodium spp. have not been rigorously defined and generally are referred to as asymptomatic malaria [4,5,6], which is an imprecise definition In this topic, the afebrile infection especially has been studied; it must be taken into account that this classification leaves out the infections that manifest without fever but with other symptoms. This afebrile infection can show some alteration in hematological parameters and show an increased level of inflammatory markers [7] or contribute to poor outcomes in pregnant women [8]
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