1.1 Introduction
Malaria is a disease of the tropics and sub-tropics and is transmitted by a vector, female Anopheles mosquito. It is caused by Plasmodium (P.) falciparum, P. malariae, P. ovale and P. vivax. In Nigeria, the prevalent species is Plasmodium falciparum accounting for >90% of all diagnosed cases (95-98%), P. ovale (<2%), P malariae (2-5%) while P. vivax is not endemic in Nigeria. The dominant vector species are Anopheles (An) gambiae s.l. and the An. Funestus(Molta, 2003; 2004; FMH, 2008).
Malaria is a public health problem in Nigeria and accounts for 110 million clinically diagnosed cases per year. The disease is responsible for about 60% outpatient care-visits and 30% hospitalizations. At least 300,000 children die of malaria per year in Nigeria and up to 30% childhood deaths, 25% of deaths in children under one year and 11% maternal deaths are due to malaria (Federal Ministry of Health, 2005; United Nations Children Fund, 2010).
It is estimated that 50% of the population will have at least one episode of malaria annually, with 2-4 episodes in under-5 year old children (Federal Ministry of Health, 2008). An estimated N132 billion is lost due to malaria annually in form of treatment costs, prevention, loss of man hours (Federal Ministry of Health, 2005; United Nations Children Fund, 2010). In 2008; 9,591 deaths were reported out of 3,481,220 reported cases of malaria in Nigeria, giving a Case Fatality Rate of about 0.3% compared to 0.2% in 2001 (Federal Ministry of Health, 2010).
On a global scale, in 2008 there was an estimated 243 million cases of malaria worldwide with the majority of cases (85%) in the African Region, followed by the South-East Asia (10%) and Eastern Mediterranean Regions- 4% (World Malaria Report, 2009).
Over-prescription of antimalarial medicines is a very common phenomenon because the diagnosis of malaria is often presumptive, despite recommendation of routine laboratory diagnosis of malaria by the World Health Organisation (WHO) (Reyburn, Mbakilwa, Mwangi, Mwerinde, Olomi, Drakeley, Whitty, 2007). The use of laboratory methods has become necessary because health workers cannot identify malaria cases reliably using clinical signs and symptoms alone (Perkins, Zucker, Otieno, 2007; Weber, Mulholland, Jaffar, Troedsson, Grove, Greenwood, 2007).
Conventional light microscopy of a blood smear is the reference gold standard for the detection of malaria parasites and the established method for the laboratory confirmation of malaria. It is sensitive and can detect densit ies as low as 5—10 parasites/µL of blood when used by skilled and careful technicians, (World Health Organization, 2000) but realistically at 100 parasites/µL under field conditions (World Health Organisation, 2008).
Microscopy provides information on parasite species (P. falciparum, P. vivax, P. ovale, and/or P. malariae) and their circulating stages (e.g. trophozoites, schizonts, gametocytes). It aids quantification of the parasite densities and assessment of parasitological response to chemotherapy in severe malaria cases. It can provide a permanent record (the smears) of the diagnostic findings and be subjected to quality control.
However, malaria diagnosis based on microscopy is labour-intensive and time-consuming, requiring at least 60 minutes from specimen collection and availability of result. Long delays occur in providing microscopy results to the clinician and as such, decisions on treatment are often taken without the benefit of the results (World Health Organisation, 2000). Microscopy depends absolutely on good techniques, reagents, microscopes and, most importantly, well trained and well supervised technicians. These conditions are hardly met at the more peripheral levels of the health care system making microscopic diagnosis an unreliable tool.
Rapid diagnostic tests (RDT) are recommended by WHO to enhance diagnosis and management of cases, prevention of complications of delayed treatment, prolonging survival and monitoring of treatment especially in children. Moreover, studies have shown that it is acceptable both to the practising physicians and the patients (Reyburn, Mbakilwa, Mwangi, Mwerinde, Olomi, Drakeley, Whitty, 2007). It is timely for case management of malaria and avoids the drawbacks of defective microscope and erratic power supply (Reyburn et al, 2007).
It aids selective treatment of only patients with positive dipstick results and thus slows down the development of drug resistance by preventing drug pressure (Rimon, Kheng, Hoyer, Thach, Ly, Permin, and Piechie, 2003). Health workers with minimal skills can be trained in RDT techniques within periods varying from three hours to one day.(World Health Organisation, 2000), (Banchongaksorn, Prajakwong, Rooney, and Vickers) RDT is robust, non- cold chain dependent and the degree of variability of test reliability and performance among individual users is relatively small.(World Health Organisation, 2000) The specificity and sensitivity of 97% and =95% respectively have been shown, for self-diagnosis among travellers from endemic areas returning to United Kingdom and in remote areas of Philippines (Whitty, Armstrong and Behrens, 2000; Bell, Go, Miguel, Walker, Cacal, Saul and 2001).
Malaria RDT detects serum antigens of Plasmodium species using fixed antibodies on strips of paper. There are three types of newly developed RDTs on the WHO pre-qualified list. According to WHO, Plasmodium Lactate Dehydrogenase (pLDH) based-tests can detect all the Plasmodium species that infect humans.(World Health Organisation, 2000) They can distinguish P. falciparum from the non- falciparum species, but cannot distinguish between P. vivax, P. ovale and P. malariae (i.e. specific for P. falciparum). Some tests detect Aldolase antigens of Plasmodium malariae, ovale and vivax or specifically that of P. falciparum while others detect Plasmodium falciparum Histidine-Rich Protein II (HRP 2) antigen (Rock, Marsh, Saul, Wellems, Taylor, Maloy and Howard, 2007; Meier, Dobeli, and Certa, 2002; Makler, Piper and Milhous, 2008). Other antigen(s) that are present in all four species are also targeted in kits that combine detection of the HRP-II antigen of P. falciparum together with that of an, as yet unspecified, “pan-malarial” antigen of the other species (World Health Organisation, 2000). The choice of RDT depends on the malaria endemicity and species prevalence (Jimoh, 2006).
In 2009, WHO recommended that persons of all ages with suspected malaria cases should undergo rapid diagnostic tests, but only 18 of 35 countries reported adhering to this (World Malaria Report, 2009). In 18 malaria high-burden African Region countries for which data were available, 22% of the reported suspected malaria cases were confirmed with RDT in 2008 (World Malaria Report, 2009). The validity of some RDTs has been investigated over the years and has been shown to be of high specificity and sensitivity in comparison to light microscopy (Bell et al,2001; Bell et al,2005). The WHO recommends a sensitivity of =95% at =100 parasites/µl for P. falciparum. (World Health Organisation, 2000; Bell et al, 2005).
Despite this recommendation and the reported validity of RDT, recent field and clinical-based studies indicated a low specificity and sensitivity compared with routine microscopy. The reasons alluded to were low parasitaemia, defective and inappropriate handling of RDT kits (World Malaria Report, 2009). The National Malaria programme has commenced the “roll out” of rapid diagnostic tests in some health facilities across the country, with the aim of scaling up its use in the field, where there is lack of skilled laboratory scientists and less than optimal conditions for routine microscopy. The recent trend of increasing mortality due to malaria in the general population and in high risk groups of pregnant women and children under the age of 5 years necessitates a more rapid scale up of malaria RDT (Federal Ministry of Health, 2010).
There is a high incidence of malaria in Nigeria with variability in endemicity. The southern part of Nigeria and the lower part of the northern region are associated with endemic and perennial episodes (7-12months). Transmission is endemic and seasonal (4-6months) in the upper north and epidemic or strongly seasonal in the extreme north-eastern part of the country (Federal Ministry of Health, 2008). The proportion of malaria confirmed by laboratory diagnosis in Nigeria is unknown. Diagnosis of malaria is often clinical-based and unreliable (Reyburn et al, 2007).
This could lead to over diagnosis, inappropriate treatment and potential development of drug resistance. The use of routine laboratory microscopy to aid clinical diagnosis is minimal. However, the use of malaria rapid diagnostic tests is a new approach and its implementation is restricted to a few facilities in the country. Artemisinin-based combination therapy, the currently recommended treatment for malaria though efficacious, is costly. There is an urgent need to prioritize its use for cases that are purely due to P. falciparum because of possibility of potential development of drug resistance.
1.2 Aim of the Study
The aim or purpose of this research is to conduct a comparative study between microscopy and rapid diagnostic test among children between 10-15 years in Onitsha, Anambra State.
1.3 Specific Objectives of the Study
Specifically, the objectives needed to achieve the above stated aim is stated as follows to:
- Ascertain the prevalence of malaria among children within the age 10-15 years in Onitsha South Local Government Area.
- Find out the predictive value of malaria rapid diagnostic test in relation to routine light microscopy.
