Hematological Profile and Gametocyte Carriage in Malaria Patients from Southern Pakistan

Molecular identification of vivax malaria relapse patients in the Yunnan Province based on homology analysis of the Plasmodium vivax circumsporozoite protein gene

More than 85% of the malaria burden in the Yunnan Province is caused by imported vivax malaria, and Yunnan is also where the majority of vivax malaria patients are diagnosed in China. Timely removal of the infection sources of Plasmodium vivax and its breeding environment remains the key to eliminating the secondary transmission of imported malaria. To that end, blood samples were collected from cases diagnosed and revalidated as single species infection with P. vivax in the Yunnan Province from 2013 to 2020. Specifically, samples from vivax malaria patients with suspected relapses episodes were subjected to PCR amplification, product sequencing, and analysis of the P. vivax circumsporozoite protein (pvcsp) gene. In total, 77 suspected relapse patients were identified out of 2484 cases infected with P. vivax, with a total of 81 recurrent episodes. A total of 156 CDS (coding DNA sequence) chains were obtained through PCR amplification and sequencing of the pvcsp gene from 159 blood samples, 121 of which can be matched to the paired sequences of 59 vivax malaria patients with both primary attack and recurrent experience. Of the 59 pairs of pvcsp gene sequences, every one of 31 pairs showed only one haplotype and no variant sites (VS), meaning every two paired sequence was completely homologous. Every one of the remaining 28 paired sequences had two haplotypes but no length polymorphism, indicating that the paired sequences was "weakly heterologous" with no fragment insertions (or deletions). All 59 vivax malaria patients with recurrences were caused by the activation of P. vivax hypnozoites originated from the same population as the primary infection. The paired analysis of the similarity between high variant genes allowed the identification of relapse episodes caused by P. vivax homologous hypnozoites and also demonstrated pvcsp gene as one of the candidate molecular markers for tracing infection origin.

A Novel Ex Vivo Drug Assay for Assessing the Transmission-Blocking Activity of Compounds on Field-Isolated Plasmodium falciparum Gametocytes

The discovery and development of transmission-blocking therapies challenge malaria elimination and necessitate standard and reproducible bioassays to measure the blocking properties of antimalarial drugs and candidate compounds. Most of the current bioassays evaluating the transmission-blocking activity of compounds rely on laboratory-adapted Plasmodium strains. Transmission-blocking data from clinical gametocyte isolates could help select novel transmission-blocking candidates for further development. Using freshly collected Plasmodium falciparum gametocytes from asymptomatic individuals, we first optimized ex vivo culture conditions to improve gametocyte viability and infectiousness by testing several culture parameters. We next pre-exposed ex vivo field-isolated gametocytes to chloroquine, dihydroartemisinin, primaquine, KDU691, GNF179, and oryzalin for 48 h prior to direct membrane feeding. We measured the activity of the drug on the ability of gametocytes to resume the sexual life cycle in Anopheles after drug exposure. Using 57 blood samples collected from Malian volunteers aged 6 to 15 years, we demonstrate that the infectivity of freshly collected field gametocytes can be preserved and improved ex vivo in a culture medium supplemented with 10% horse serum at 4% hematocrit for 48 h. Moreover, our optimized drug assay displays the weak transmission-blocking activity of chloroquine and dihydroartemisinin, while primaquine and oryzalin exhibited a transmission-blocking activity of ~50% at 1 μM. KDU691 and GNF179 both interrupted Plasmodium transmission at 1 μM and 5 nM, respectively. This new approach, if implemented, has the potential to accelerate the screening of compounds with transmission-blocking activity.

Hematological indices and abnormalities among patients with uncomplicated falciparum malaria in Kosti city of the White Nile state, Sudan: a comparative study

BACKGROUND

Hematological abnormalities are common features in falciparum malaria but vary among different populations across countries. Therefore, we compared hematological indices and abnormalities between Plasmodium falciparum-infected patients and malaria-negative subjects in Kosti city of the White Nile State, Sudan.

METHODS

A comparative, cross-sectional study was conducted at the Clinical Laboratory Unit of Kosti Teaching Hospital from June to December 2018. A total of 392 participants (192 P. falciparum-infected patients and 200 malaria-negative subjects) were recruited in the study. Hematological indices of hemoglobin (Hb), red blood cells (RBCs), white blood cells (WBCs) and platelets were measured, and their median values were statistically compared.

RESULTS

The majority of P. falciparum-infected patients (67.6%) showed a low-level parasitemia. The median values of Hb concentration, RBC count, mean corpuscular volume (MCV), mean corpuscular Hb (MCH) and mean corpuscular Hb concentration (MCHC) were significantly lower in P. falciparum-infected patients, while the median red cell distribution width (RDW) was significantly higher in the patients compared to malaria-negative subjects. Anemia, low MCV, low MCH, low MCHC and high RDW were significantly associated with falciparum malaria, but parasitemia level was not significantly associated with anemia severity. The median total WBC count was non-significantly higher in P. falciparum-infected patients, with neutropenia being significantly associated with falciparum malaria. The median platelet count was significantly lower in P. falciparum-infected patients, with thrombocytopenia being significantly associated with falciparum malaria.

CONCLUSIONS

Falciparum malaria among patients in Kosti city of the White Nile State, Sudan is predominantly of low-level parasitemia. It is significantly associated with anemia, low MCV, low MCH, low MCHC, high RDW, thrombocytopenia and neutropenia. However, parasitemia level is not a significant predictor of anemia severity. On the other hand, leucopenia is not useful to predict falciparum malaria. Further large-scale studies in community and healthcare settings and inclusion of patients with complicated or severe malaria and those with high parasite densities are recommended.

Genetic characterization of Plasmodium vivax isolates from Pakistan using circumsporozoite protein (pvcsp) and merozoite surface protein-1 (pvmsp-1) genes as genetic markers

Background

Plasmodium vivax contributes to over 70% malaria burden in Pakistan, but limited data exists on various aspects including genetic diversity of the parasite as compared to other parts of the world. Since the information about the genetic diversity of P. vivax assists to understand the population dynamics of the parasite, the current study was designed to understand population divergence of P. vivax in Pakistan using circumsporozoite protein (pvcsp) and merozoite surface protein-1 (pvmsp-1) genes as molecular markers.

Methods

The PCR for pvcsp and pvmsp-1 genes was carried out for 150 P. vivax isolates, followed by DNA sequencing of 35 and 30, respectively. Genetic diversity and polymorphism were analysed using ChromasPro, ClustalW, MEGA7, DnaSP v.5 and WebLogo programs.

Results

The PCR for pvcsp and pvmsp-1 genes was carried out for 150 P. vivax isolates and resulting the PCR products of 1100 bp for pvcsp and ~ 400 bp for pvmsp-1 genes, respectively. In the central-repeat region (CRR) of pvcsp gene, sequences comprised of four variable repeats of PRMs, out of which GDRADGQPA (PRM1), GDRAAGQPA (PRM2) were more extensively dispersed among the P. vivax isolates. Partial sequences (~ 400 bp) of block 2 of pvmsp-1 gene depicted high level of diversity.

Conclusion

The results revealed the polymorphism and genetic diversity especially at the CRR of pvcsp and block 2 of pvmsp-1 genes, respectively. The base-line data presented here warrants future studies to investigate more into the genetic diversity of P. vivax with large sample size from across the country for better understanding of population dynamics of P. vivax that will help to control malaria at individual and community level.