Molecular investigation of mixed malaria infections in Southwest Saudi Arabia

Objective: To investigate the incidence of mixedspecies (MS) malaria infection, and compare the results with microscopically confirmed cases of malaria. Methods: During 2010, blood spots collected from 371 clinically suspected cases of malaria were microscopically examined in a cross-sectional study. The DNA was extracted from the samples, and a nested polymerase chain reaction (PCR) was performed. The results obtained by the 2 methods were compared. Results: From the microscopic analysis it was determined that 369 samples (99.5%) were positive for Plasmodium falciparum (P. falciparum) and 2 were Plasmodium vivax (P. vivax) mono-infections. There were no mixed malaria infections. The PCR analysis, however, showed that in 7 cases (1.9%) the infection was caused by MS malaria comprising of P. falciparum and P. vivax, 2 of these representing the cases that were microscopically diagnosed as P. vivax monoinfections. All cases were negative for Plasmodium malariae, Plasmodium ovale, and Plasmodium knowlesi. Conclusion: Mixed malaria infections are currently overlooked when using microscopy. The PCR assays are essential complementary techniques that should be used with microscopic examination of blood smears. Saudi Med J 2015; Vol. 36 (2): 248-251 doi: 10.15537/smj.2015.2.10874 M is among the most prevalent of endemic tropical diseases. Human infection with malaria is caused by 4 species of plasmodia: Plasmodium falciparum (P. falciparum), Plasmodium vivax (P. vivax), Plasmodium malariae (P. malariae), Plasmodium ovale (P. ovale), and, rarely, Plasmodium knowlesi (P. knowlesi). Each of these species is associated with different clinical features and outcomes. The risk of severe malaria symptoms increases considerably if treatment is delayed. In 2012, 99 countries documented ongoing malaria transmission with around 3.3 billion people at risk of contracting the disease. Globally, 219 million cases of malaria were reported with 660,000 associated deaths.1 In Africa, the predominant malaria species is P. falciparum. Elsewhere; however, including Russia, the tropical regions of Asia, the Pacific, and South, and Central America, P. vivax is the most common species. In geographical areas where more than one malaria species is present, these infections may combine and such combined infections are usually under-reported.2 In the Kingdom of Saudi Arabia (KSA), Jazan and Aseer provinces, in the south-west of the country, are the most malaria-endemic areas with a prominence of P. falciparum. No mixed-infection cases have been reported from these regions.3 In early 2008, Artemisinin-based combination therapy (ACT) was introduced to KSA to treat all malaria-positive cases. For P. vivax malaria, chloroquine is used, but when P. vivax is resistant to chloroquine, an appropriate ACT regimen is recommended together with a primaquine regimen.4 Severe and complicated malaria is most commonly caused by P. falciparum, although P. vivax, and P. knowlesi may also be responsible for severe infections. Research on the P. vivax parasite has tended to lag behind, since it was previously thought that mono-infection with P. vivax resulted only in benign tertian fever, and that severe cases of P. vivax infection were the result of coinfection with P. falciparum. Recent evidence, however, suggests that clinical symptoms for this infection have changed and that P. vivax mono-infections can result in severe malaria (SM) and even death.5 Incorrect diagnosis of the malaria species causing infection in a patient is a potentially significant problem, since misdiagnosis could result in the infection becoming severe, in the case of P. falciparum, or relapse in the case of P. vivax.6 False-negative diagnoses for P. vivax are common in endemic areas, and many untreated patients therefore serve as reservoir hosts of malaria parasites.7 In addition, if P. vivax schizonts are detected in venous blood, coinfection with P. falciparum may be missed, since P. falciparum schizonts are only present in the capillaries of internal organs.7 Microscopic examination of Giemsa-stained blood films is the best technique for detecting the malaria parasite due to its low cost and ability to distinguish between malaria species. Nevertheless, accurate diagnosis Disclosure. The experimental work was partially funded by King Khalid University Scientific Deanship, Abha, Kingdom of Saudi Arabia. The author declares that there was no conflict of interest and this work was not presented in a conference proceeding.