Patterns of mixed Plasmodium species infections among children six years and under in selected malaria hyper-endemic communities of Zambia: population-based survey observations.
BACKGROUND
Although malaria is preventable and treatable, it still claims 660,000 lives every year globally with children under five years of age having the highest burden. In Zambia, malaria rapid diagnostic tests (RDTs) that only detect Plasmodium falciparum are the main confirmatory means for malaria diagnosis in most health facilities without microscopy services. As a consequence of this P. falciparum species diagnostic approach, non-falciparum malaria is not only under-diagnosed but entirely missed, thereby making the exact disease burden unknown. We thus investigated the prevalence of various Plasmodium spp. and associated burden of infection in selected communities in Zambia.


METHODS
Data from two malaria hyper-endemic provinces (Eastern and Luapula) of the 2012 National Malaria Indicator Survey (MIS), conducted between April and May 2012, were used. The MIS is a nationally representative, two-stage cluster survey conducted to coincide with the end of the malaria transmission season. Social, behavioural and background information were collected from households as part of the survey. Thick blood smears, RDTs and dried blood spots (DBS) were collected from children below six years of age. Slides were stained using Giemsa and examined by microscopy while polymerase chain reaction (PCR) was used to analyse the DBS for malaria Plasmodium spp. Multivariate logistic regression was employed to examine the association between background factors and malaria.


RESULTS
Overall, 873 children younger than six years of age were surveyed. The overall prevalence of Plasmodium spp. by PCR was 54.3% (95% CI 51-57.6%). Of the total Plasmodium isolates, 88% were P. falciparum, 10.6% were mixed infections and 1.4% were non-falciparum mono infections. Among the mixed infections, the majority were a combination of P. falciparum and P. malariae (6.5% of all mixed infections). Children two years and older (2-5 years) had three-fold higher risk of mixed malaria infections (aOR 2.8 CI 1.31-5.69) than children younger than two years of age.


CONCLUSIONS
The high prevalence of mixed Plasmodium spp. infections in this population stresses review of the current malaria RDT diagnostic approaches. The observed less incidence of mixed infections in children under two years of age compared to their older two-to-five-year-old counterparts is probably due to the protective maternal passive immunity, among other factors, in that age group.
Department of Biomedical Science, University of Zambia, School of Medicine, Lusaka, Zambia. lungowesitali@gmail.com.|Department of Paediatrics and Child Health, School of Medicine, Malaria Research Unit (SMUTH-MRU), Lusaka, Zambia. lungowesitali@gmail.com.|John Hopkins Malaria Research Institute, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA. lungowesitali@gmail.com.
Lungowe
L
Sitali
Department of Paediatrics and Child Health, School of Medicine, Malaria Research Unit (SMUTH-MRU), Lusaka, Zambia. jameschipeta@smuth-mru.org.zm.|Department of Paediatrics and Child Health, University of Zambia, School of Medicine, Lusaka, Zambia. jameschipeta@smuth-mru.org.zm.
James
J
Chipeta
PATH-Malaria Control and Elimination Partnership in Africa (MACEPA), National Malaria Control Centre, Lusaka, Zambia. jmiller@path.org.
John M
JM
Miller
Ministry of Health, National Malaria Control Centre, Lusaka, Zambia. mhawela@yahoo.co.uk.
Hawela B
HB
Moonga
Department of Tropical Medicine, Tulane University School of Public Health and Tropical Medicine, New Orleans, USA. nkumar@tulane.edu.
Nirbhay
N
Kumar
John Hopkins Malaria Research Institute, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA. wmoss1@jhu.edu.
William J
WJ
Moss
Department of Paediatrics and Child Health, School of Medicine, Malaria Research Unit (SMUTH-MRU), Lusaka, Zambia. ccmichelo@yahoo.com.|Department of Public Health, University of Zambia, School of Medicine, Lusaka, Zambia. ccmichelo@yahoo.com.
Charles
C
Michelo
D002648:Child; D002662:Child Health Services; D002675:Child, Preschool; D003955:Diagnostic Tests, Routine; D019353:Endemic Diseases; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008288:Malaria / Q000453:epidemiology* / Q000469:parasitology; D016778:Malaria, Falciparum / Q000453:epidemiology / Q000469:parasitology; D008297:Male; D010961:Plasmodium / Q000235:genetics / Q000302:isolation & purification*; D010963:Plasmodium falciparum / Q000235:genetics / Q000302:isolation & purification; D016133:Polymerase Chain Reaction; D015995:Prevalence; D012621:Seasons; D011795:Surveys and Questionnaires; D015024:Zambia / Q000453:epidemiology