Correction: Colorimetric Detection of Plasmodium vivax in Urine Using MSP10 Oligonucleotides and Gold Nanoparticles.

[This corrects the article DOI: 10.1371/journal.pntd.0005029.].

Colorimetric Detection of Plasmodium vivax in Urine Using MSP10 Oligonucleotides and Gold Nanoparticles.

Plasmodium vivax is the most prevalent cause of human malaria in the world and can lead to severe disease with high potential for relapse. Its genetic and geographic diversities make it challenging to control. P. vivax is understudied and to achieve control of malaria in endemic areas, a rapid, accurate, and simple diagnostic tool is necessary. In this pilot study, we found that a colorimetric system using AuNPs and MSP10 DNA detection in urine can provide fast, easy, and inexpensive identification of P. vivax. The test exhibited promising sensitivity (84%), high specificity (97%), and only mild cross-reactivity with P. falciparum (21%). It is simple to use, with a visible color change that negates the need for a spectrometer, making it suitable for use in austere conditions. Using urine eliminates the need for finger-prick, increasing both the safety profile and patient acceptance of this model.

Relationship of hepcidin with parasitemia and anemia among patients with uncomplicated Plasmodium falciparum malaria in Ghana.

The pathogenesis of malarial anemia is incompletely understood. Hepcidin, a recently discovered peptide hormone, is a major regulator of iron metabolism and is thought to play a central role in the anemia of chronic inflammation. The specific aim of the study was to characterize the association between urinary hepcidin, hemoglobin, and parasitemia in 199 patients presenting for evaluation of Plasmodium falciparum malaria in Ghana. Urinary hepcidin was semi-quantitatively assessed using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry. Urinary hepcidin (intensity/mmol creatinine) was associated with log parasitemia in 86 children (beta = 0.086, standard error [SE] = 0.035, P < 0.017), 31 pregnant women (beta = 0.218, SE = 0.085, P < 0.016), and 82 adults (beta = 0.184, SE =0.043, P < 0.0001). Urinary hepcidin was not significantly associated with hemoglobin or anemia. Urinary hepcidin is more strongly associated with parasitemia than hemoglobin or anemia among patients with acute P. falciparum malaria in Ghana.

Detection of malaria sporozoites by standard ELISA and VecTestTM dipstick assay in field-collected anopheline mosquitoes from a malaria endemic site in Ghana.

We compared the VecTestTM dipstick assay for detection of Plasmodium sporozoites in Anopheles vectors of malaria with standard circumsporozoite (CS) microplate ELISA for detection of Plasmodium falciparum circumsporozoite protein (PfCSP) in Anopheles mosquitoes. Mosquitoes were collected from a malaria endemic site (Kassena Nankana district) in northern Ghana. Of 2620 randomly sampled mosquitoes tested, the standard CS-ELISA gave a sporozoite rate of 10.8% compared with 11.2% by VecTestTM, which was not statistically different (P = 0.66). Visual reading of the CS-ELISA results gave a sporozoite rate of 13.4%, which was higher than the other tests (P > 0.05). To allow a more objective evaluation of the sensitivity of the dipstick, an additional 136 known CS-ELISA-positive specimens were analysed. The prevalence of the test (including the additional samples) was 14.6% and 14.7% for CS-ELISA and dipstick, respectively (P > 0.05). The estimated prevalence by visual assessment of the CS-ELISA results was 17.5%. The relative specificity and sensitivity of the VecTestTM dipstick and visually read ELISA were estimated based on the CS-ELISA as a gold standard. The specificities of the dipstick and visual ELISA were high, 98.0% and 96.6%, respectively. However, the sensitivities of the two assays were 88.8% for VecTest and 100% for visual ELISA (P < 0.01). Concordance between VecTest and CS-ELISA was good (kappa = 0.86). Similarly, there was a good concordance between the dipstick and the visually read ELISA (kappa = 0.88). Extrapolating from PfCSP controls (titrated quantities of P. falciparum sporozoites), mean sporozoite loads of CS-ELISA-positive An. gambiae (286 +/- 28.05) and An. funestus (236 +/- 19.32) were determined (P = 0.146). The visual dipstick grades showed high correlation with sporozoite load. The more intense the dipstick colour, the higher the mean sporozoite load (+ = 108, ++ = 207, +++ = 290, r = 0.99, r2 = 1). The VecTest dipstick offers practical advantages for field workers needing rapid and accurate means of detection of sporozoites in mosquitoes.