Microscopic detection of mixed malarial infections: improvement by saponin hemolysis

The role of cholesterol in invasion and growth of malaria parasites

Malaria parasites are unicellular eukaryotic pathogens that develop through a complex lifecycle involving two hosts, an anopheline mosquito and a vertebrate host. Throughout this lifecycle, the parasite encounters widely differing conditions and survives in distinct ways, from an intracellular lifestyle in the vertebrate host to exclusively extracellular stages in the mosquito. Although the parasite relies on cholesterol for its growth, the parasite has an ambiguous relationship with cholesterol: cholesterol is required for invasion of host cells by the parasite, including hepatocytes and erythrocytes, and for the development of the parasites in those cells. However, the parasite is unable to produce cholesterol itself and appears to remove cholesterol actively from its own plasma membrane, thereby setting up a cholesterol gradient inside the infected host erythrocyte. Overall a picture emerges in which the parasite relies on host cholesterol and carefully controls its transport. Here, we describe the role of cholesterol at the different lifecycle stages of the parasites.

Difference between Microscopic and PCR Examination Result for Malaria Diagnosis and Treatment Evaluation in Sumba Barat Daya, Indonesia

Microscopic examination is the backbone of malaria diagnosis and treatment evaluation in Indonesia. This test has limited ability to detect malaria at low parasite density. Inversely, nested polymerase chain reaction (PCR) can detect parasites at a density below the microscopic examination’s detection limit. The objective of this study is to compare microscopic and PCR results when being used to identify malaria in suspected patients and patients who underwent dihydroartemisinin–piperaquine (DHP) therapy in the last 3–8 weeks with or without symptoms in Sumba Barat Daya, Nusa Tenggara Timur, Indonesia. Recruitment was conducted between April 2019 and February 2020. Blood samples were then taken for microscopic and PCR examinations. Participants (n = 409) were divided into three groups: suspected malaria (42.5%), post-DHP therapy with fever (4.9%), and post-DHP therapy without fever (52.6%). Microscopic examination found five cases of P. falciparum + P. vivax infection, while PCR found 346 cases. All microscopic examinations turned negative in the post-DHP-therapy group. Conversely, PCR result from the same group yielded 29 negative results. Overall, our study showed that microscopic examination and PCR generated different results in detecting Plasmodium species, especially in patients with mixed infection and in patients who recently underwent DHP therapy.

Assessing the reliability of microscopy and rapid diagnostic tests in malaria diagnosis in areas with varying parasite density among older children and adult patients in Nigeria

Background:

Current malaria control strategies are based on early diagnosis and appropriate treatment of malaria cases. The study aimed at comparing the performance of blood film microscopy and rapid diagnostic test (RDT) in Plasmodium falciparum detection in patients ≥6 years of age.

Materials and Methods:

A total of 154 consecutive pyretic patients aged 6-62 years were enrolled, sampled, and tested for malaria using RDT (first response) and microscopy by Giemsa staining. Genomic DNA was extracted after saponin hemolysis and nested polymerase chain reaction (PCR) was used to detect Plasmodium falciparum. The endpoints were sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV).

Results:

Of the 154 patients, 80 (51.9%) had fever of ≥37.5°C. 106 (68.8%) were positive by First response^®, 132 (85.7%) by microscopy, and 121 (78.6%) by PCR. The sensitivity, specificity, PPV, and NPV of first response compared to microscopic method were 82.2%, 100.0%, 100.0%, and 34.3%, respectively, while it was 75.4%, 75.0%, 95.3%, and 31.2%, respectively, when compared to PCR. The sensitivity, specificity, PPV, and NPV of the microscopic method compared to PCR were 92.3%, 50.0%, 90.91%, and 54.5%, respectively. There was a significant difference in the performance of RDT and film microscopy methods (P ≤ 0.05).

Conclusion:

Microscopy performed better and is more reliable than first response (RDT) in areas with low parasite density among patients ≥6 years of age. Rapid diagnostic tests could be useful in aareas with high parasite density as an alternative to smear microscopy

Laboratory diagnosis of malaria in nonhuman primates

Nonhuman primates (NHPs) are commonly used for biomedical research because of the high level of gene homology that underlies physiologic similarity to human beings. Malaria parasites of the genus Plasmodium cause one of the most frequent parasitic diseases of NHPs originating from tropical and subtropical areas and as such represent a significant research confounder. Malaria in NHPs presents a diagnostic challenge especially to those laboratories that see no more than a few malaria cases per year in NHPs. The accurate and timely diagnosis of malaria infection in NHPs facilitates the appropriate treatment of individuals infected with the malaria parasites. Conventional microscopy based on the examination of Giemsa-stained thick and thin blood films remains the mainstay of laboratory diagnosis of malaria infection because of the high diagnostic sensitivity and specificity and also the capability for Plasmodium species identification and parasite counts. This procedure is recognized as technically difficult and time-consuming, requiring considerable training to obtain the necessary skills. In the past few years, efforts to replace the traditional but tedious reading of blood films have led to different techniques for the detection of malaria parasites, including fluorescence microscopy, detection of intraleukocytic hemozoin or malaria pigment using automated blood cell analyzers, immunochromatographic rapid diagnostic tests based on malaria antigen detection, and PCR assays. These techniques offer new approaches for diagnosing malaria in NHPs. This review focuses on the available laboratory diagnostic tools for malaria in NHPs.