Malaria Diagnostic Test Safely Determines Infection During Ebola Outbreak

The Ebola virus is associated with a high case fatality ratio, as well as a high rate of transmission to health care professionals. As a result, countries affected by outbreaks of Ebola virus disease face a high degree of strain on their health care systems. The consequences of such a strain include insufficient access to health care facilities.

Both malaria and the Ebola virus are prevalent in the West African country of Liberia and present with similar symptoms, such as fever, headache, chills, and vomiting in their earliest stages. Insufficient access to health care for those infected with the Ebola virus threatens to undermine efforts to control the prevalence of malaria.

A diagnosis of malaria can be made using a molecular technique that assesses the presence of Plasmodium spp. parasitemia in the blood; however, the incidence and utility of this malaria marker in those with suspected Ebola virus infection had not been investigated.

In order to address this question, Dr. Emmie de Wit, PhD, a research fellow at the National Institutes of Health and the lead author on the study, spent 4 months working in a field laboratory in Monrovia, Liberia during the Ebola outbreak in West Africa. The results of the study were recently published in Emerging Infectious Diseases.

In the Centers for Disease Control and Prevention—National Institutes of Health (CDC–NIH) diagnostic laboratory located at the Eternal Love Winning Africa (ELWA) campus in Monrovia, blood samples were collected from 1,058 individuals suspected of infection with the Ebola virus between October 12, 2014 and March 28, 2015.The blood samples were analyzed for both Ebola virus infection and the malaria marker Plasmodium spp. parasitemia. Real-time quantitative reverse transcription PCR (qRT-PCR) was the method used to detect Plasmodium spp. parasitemia, as it is considered to be the most sensitive of the available diagnostic tests.

The diagnosis of Ebola virus infection was found to be higher in samples collected during the early portion of the study (October—November) as compared with those collected towards the end of the study.

Unlike the pattern seen in Ebola virus infections over the course of the study, the diagnosis of Plasmodium spp. parasitemia was observed to be relatively stable. Even when taking the reduced number of Ebola virus infections detected later in the study into account, study results revealed that 40%—60% of the weekly samples collected showed Ebola virus infections, Plasmodium spp. parasitemia, or both.

Roughly one quarter (24.5%) of the 1,058 samples tested were positive for Ebola virus infection alone. An additional quarter (23%) of the samples tested positive for Plasmodium spp. parasitemia alone, and a very small percentage of the samples (4.4%) showed both Ebola virus infection as well as Plasmodium spp. parasitemia. Further testing of Plasmodium-positive samples showed a clear dominance (95%) of P. falciparum, making it the most common of the Plasmodium species causing parasitemia in this patient population.

In additional findings, significantly fewer Plasmodium spp. parasites were found in those infected with the Ebola virus when compared with non-infected individuals. The study authors speculated that this finding was, "likely because clinical symptoms in these patients were caused by the Ebola virus infection rather than malaria."

The primary advantage associated with the use of PCR-based detection of Plasmodium spp. parasitemia is the loss of any need for additional handling of potentially dangerous clinical specimens. For this reason, the addition of PCR-based diagnostic tests for Plasmodium spp. parasitemia would not result in any additional safety risks for those conducting this laboratory-based work. Furthermore, the use of multiplex PCR would not result in a need for additional testing time or materials.

Based on the analyses of the data generated in the study, the authors concluded that, "our findings suggest that PCR-based testing for Plasmodium spp. parasitemia can be implemented easily and safely in laboratories performing Ebola virus diagnostics to assist with case-patient management during Ebola virus disease outbreaks in malaria-endemic areas."

Because malaria remains a substantial public health issue in the West African countries most severely affected by the Ebola virus disease epidemic, new and safer diagnostic techniques for its detection in this patient population are urgently needed. Ideally, any new diagnostic technique would be easy to perform while also limiting exposure to potentially infected blood samples. By proving the feasibility of a malaria molecular diagnostic technique that is both easy and safe to perform, the results of this study demonstrate an improved diagnostic approach for malaria detection in a West African region heavily impacted by Ebola virus outbreaks.

William Perlman, PhD, CMPP is a former research scientist currently working as a medical/scientific content development specialist. He earned his BA in Psychology from Johns Hopkins University, his PhD in Neuroscience at UCLA, and completed three years of postdoctoral fellowship in the Neuropathology Section of the Clinical Brain Disorders Branch of the National Institute of Mental Health.