Northeastern states of India share international borders with Myanmar, China, Bangladesh, and Bhutan, contributing 7.45% of the overall malaria cases in the country. Mizoram accounts for the highest malaria burden in the northeastern states, with perennial transmission in the hilly and deep-forested areas. Plasmodium falciparum (93%) is the most prevalent human Plasmodium species, followed by P. vivax; however, information on P. ovale and P. malariae is negligible. Rapid diagnostic tests (RDTs) are the most preferred malaria diagnostic tool followed by microscopy in this high malaria-endemic region. The present epidemiological study was carried out in July and August 2019 to assess the malaria burden in and around the Chawngte primary health center, Lawngtlai District of Mizoram, using RDTs and microscopy as diagnostic tools. World Health Organization-certified level I microscopists examined the blood smears. Diagnosis using RDTs resulted in 151 malaria cases (P. falciparum: 136; P. vivax: 15) out of 948 screened fever cases. However, blood smear examination detected 179 cases (P. falciparum: 154; P. vivax: 17; mixed P. falciparum + P. vivax infection: 3; P. malariae: 5). Analysis revealed that the risk of malaria infection was higher in the ≥5-year-old subjects than in the under-5 age group. The mean parasite density of P. malariae (1455.00/μL blood) was the lowest; cf. with P. falciparum: 12,275.08/μL blood. Surveillance at the point-of-care level using microscopy was able to detect all the four human Plasmodium species and their mixed infections, including P. malariae, which were missed with RDTs. Thus, the quality of microscopy along with trained manpower should be strengthened to diagnose all human malaria parasite species (particularly P. malariae and P. ovale) until the molecular tools are deployed at the field level to achieve malaria elimination by 2030.

: Malaria elimination is one of the top health care priorities in India, necessitating accessible and accurate diagnosis for effective treatment. A malaria slide bank in India is a collection of quality-controlled malaria-positive and -negative slides and is considered a vital asset for quality diagnosis. The collection of blood samples, preparation of blood smears, staining, quality control, molecular characterizations, and slide validation were carried out according to standard operating procedures in accordance with the WHO reference laboratory. The true count and parasite density per microliter were computed in accordance with WHO guidelines. Over 27 months, 48 batches (8,196 slides) were prepared. Overall, the majority of slide batches were Plasmodium vivax (45.9%; 22/48), followed by Plasmodium falciparum (25%; 12/48), malaria-negative infections (25%; 12/48), and mixed infections (4.1%; 2/48). All 48 batches passed internal validation by WHO-certified level-1 microscopists. For a batch, the true count was the median of the validators’ counts (range, 111–280,795 parasites/µL). Except for mixed infections, the PCR results agreed with the verified microscopy results. Malaria slide bank slides would be a valuable tool for quality control, assurance, and microscopist training.

Plasmodium vivax malaria elimination requires radical cure with chloroquine/primaquine. However, primaquine causes hemolysis in glucose-6-phosphate dehydrogenase-deficient (G6PDd) individuals. Between February 2016 and July 2017 in Odisha State, India, a prospective, observational, active pharmacovigilance study assessed the hematologic safety of directly observed 25 mg/kg chloroquine over 3 days plus primaquine 0.25 mg/kg/day for 14 days in 100 P. vivax patients (≥ 1 year old) with hemoglobin (Hb) ≥ 7 g/dL. Pretreatment G6PDd screening was not done, but patients were advised on hemolysis signs and symptoms using a visual aid. For evaluable patients, the mean absolute change in Hb between day 0 and day 7 was −0.62 g/dL (95% confidence interval [CI]: −0.93, −0.31) for males (N = 53) versus −0.24 g/dL (95%CI: −0.59, 0.10) for females (N = 45; P = 0.034). Hemoglobin declines ≥ 3 g/dL occurred in 5/99 (5.1%) patients (three males, two females); none had concurrent clinical symptoms of hemolysis. Based on G6PD qualitative testing after study completion, three had a G6PD-normal phenotype, one female was confirmed by genotyping as G6PDd heterozygous, and one male had an unknown phenotype. A G6PDd prevalence survey was conducted between August 2017 and March 2018 in the same region using qualitative G6PD testing, confirmed by genotyping. G6PDd prevalence was 12.0% (14/117) in tribal versus 3.1% (16/509) in nontribal populations, with G6PD Orissa identified in 29/30 (96.7%) of G6PDd samples. Following chloroquine/primaquine, notable Hb declines were observed in this population that were not recognized by patients based on clinical signs and symptoms.

Since 2010, malaria rapid diagnostic tests (RDTs) are widely used to detect malaria. The Indian Council of Medical Research–National Institute of Malaria Research performed lot testing (LT) according to WHO procedures since 2016. Lot testing is performed to evaluate the lot-to-lot variation in performance of malaria RDTs. Four sets of positive quality control (QC) panels for P. falciparum (Pf) and P. vivax (Pv) and 10 negative panels tested RDTs. RDTs were reported as pass, failed, or deferred on the basis of WHO criteria. In the past 5 years, 275 lots containing 15,488 RDT kits for malaria diagnosis were subjected to LT. The monovalent RDTs (n = 1,216), based on either Pf histidine rich protein 2 (HRP2) or Pan-Plasmodium lactate dehydrogenase (Pan-pLDH) antigens, showed 90.4% sensitivity and 100% specificity, whereas RDTs based on HRP2 + Pan-pLDH or HRP2 + pLDH (n = 13,924) had sensitivity 95.6% and specificity 99.5%, respectively. RDTs based on PfHRP2 + Pv-pLDH + Pan-pLDH (n = 348) had 100% sensitivity and specificity. In a comparison between HRP2 + pLDH or HRP2 + Pan-pLDH to HRP2 + pLDH + Pan-pLDH RDTs, it was found that the sensitivity of PfHRP2 with Pan-pLDH RDTs (n = 2,382) was only 83%. Of the 275 lots analyzed, 15 lots of PfHRP2 with Pan-pLDH were deferred. The QC panel for Pf revealed a faint Pan band in the tested lots, which is a cause for concern. The results of deferred lots were reported to concerned government agencies. Quality-compromised RDTs may lead to an incorrect diagnosis. It is critical to have a QC system in place for effective malaria management.