Improving the quality of malaria diagnosis in southern Africa through the development of a regional malaria slide bank.

BACKGROUND: A malaria slide bank (MSB) is a useful asset for any malaria microscopy testing laboratory to have access to. However, it is not feasible for every country to have its own MSB. If countries are able to pool their resources, a regional MSB is a viable solution. This paper describes the methodology, costing and lessons learnt of establishing and maintaining an MSB over a 3-year period, for a Southern Africa Development Community region. METHODS: A national reference laboratory in South Africa was granted funding for setting up the MSB; it possessed experienced staff and suitable resources. Two additional full-time personnel were employed to carry out the activities of this project. Strict protocols for donor/patient blood sample screening, smear preparation, mass staining, quality control and slide validation were followed. Slides from the MSB were used for training and proficiency testing purposes. The initial and recurrent yearly costs to set up and maintain the MSB were calculated. RESULTS: Over 35 months, 154 batches (26,623 slides) were prepared; the majority were Plasmodium falciparum. Ninety-two percent (141/154) of batches passed internal quality control, and 89% (93/104) passed external validation. From these slides, two training slide sets and six proficiency testing slide sets were sent out. The initial year's cost to establish an MSB was calculated at approximately $165,000, and the recurrent year-on-year cost was $130,000. CONCLUSIONS: The key components for maintaining a high-quality MSB are consistent funding, competent staff and adherence to standardized protocols. Travel to malaria-endemic areas for access to non-falciparum malaria species, and dilution of P. falciparum blood to desired parasite densities, are extremely useful to ensure variety. The MSB created here supported multiple laboratories in eight countries, and has the potential to expand.

Major Threat to Malaria Control Programs by Plasmodium falciparum Lacking Histidine-Rich Protein 2, Eritrea.

False-negative results for Plasmodium falciparum histidine-rich protein (HRP) 2-based rapid diagnostic tests (RDTs) are increasing in Eritrea. We investigated HRP gene 2/3 (pfhrp2/pfhrp3) status in 50 infected patients at 2 hospitals. We showed that 80.8% (21/26) of patients at Ghindae Hospital and 41.7% (10/24) at Massawa Hospital were infected with pfhrp2-negative parasites and 92.3% (24/26) of patients at Ghindae Hospital and 70.8% (17/24) at Massawa Hospital were infected with pfhrp3-negative parasites. Parasite densities between pfhrp2-positive and pfhrp2-negative patients were comparable. All pfhrp2-negative samples had no detectable HRP2/3 antigen and showed negative results for HRP2-based RDTs. pfhrp2-negative parasites were genetically less diverse and formed 2 clusters with no close relationships to parasites from Peru. These parasites probably emerged independently by selection in Eritrea. High prevalence of pfhrp2-negative parasites caused a high rate of false-negative results for RDTs. Determining prevalence of pfhrp2-negative parasites is urgently needed in neighboring countries to assist case management policies.

Molecular evidence of high rates of asymptomatic P. vivax infection and very low P. falciparum malaria in Botswana.

BACKGROUND: Botswana is one of eight SADC countries targeting malaria elimination by 2018. Through spirited upscaling of control activities and passive surveillance, significant reductions in case incidence of Plasmodium falciparum (0.96 - 0.01) was achieved between 2008 and 2012. As part of the elimination campaign, active detection of asymptomatic Plasmodium species by a highly sensitive method was deemed necessary. This study was carried out to determine asymptomatic Plasmodium species carriage by nested PCR in the country, in 2012. METHOD: A cross-sectional study involving 3924 apparently healthy participants were screened for Plasmodium species in 14 districts (5 endemic: Okavango, Ngami, Tutume, Boteti and Bobirwa; and 9 epidemic: North East, Francistown, Serowe-Palapye, Ghanzi, Kweneng West, Kweneng East, Kgatleng, South East, and Good Hope). Venous blood was taken from each participant for a nested PCR detection of Plasmodium species. RESULTS: The parasite rates of asymptomatic Plasmodium species detected were as follows: Plasmodium falciparum, 0.16 %; Plasmodium vivax, 4.66 %; Plasmodium malariae, (Pm) 0.16 %; Plasmodium ovale, 0 %, mixed infections (P. falciparum and P. vivax), 0.055 %; and (P. vivax and P. malariae), 0.027 %, (total: 5.062 %). The high proportion of asymptomatic reservoir of P. vivax was clustered in the East, South Eastern and Central districts of the country. There appeared to be a correlation between the occurrence of P. malariae infection with P. vivax infection, with the former only occurring in districts that had substantial P. vivax circulation. The median age among 2-12 year olds for P. vivax infection was 5 years (Mean 5.13 years, interquartile range 3-7 years). The odds of being infected with P. vivax decreased by 7 % for each year increase in age (OR 0.93, 95 % CI 0.87-1.00, p = 0.056). CONCLUSION: We have confirmed low parasite rate of asymptomatic Plasmodium species in Botswana, with the exception of P.vivax which was unexpectedly high. This has implication for the elimination campaign so a follow up study is warranted to inform decisions on new strategies that take this evidence into account in the elimination campaign.