‘Invisible’ species of malaria that hides inside body

Thursday May 16 2019

malaria

A worker of the Entomologist Research Centre, Kenya, takes a mosquito to analyse it for the presence of malaria parasite. Tanzania's malaria prevalence rate has declined over the past few years. PHOTO | CRISTINA ALDEHUELA | AFP 

VERAH OKEYO
By VERAH OKEYO
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Scientists in Tanzania have discovered that a species of malaria can live in the body for decades without showing any clinical signs, but still manage to contribute to the transmission of malaria in the country.

In a study published last week in Malaria Journal, the researchers reported two men who tested positive for Palcifarum malariae, confirming a suspicion in the scientific community that the human malaria species can live in the body for an extended period of time.

The two healthy looking men aged 20 and 22 were from Bagamoyo, the town in which Ifakara Health Institute, which was part of the study is located.

The men were part of an ongoing study that was testing the efficacy of a vaccine. They underwent a battery of tests to rule out any possibility of other diseases.

Lead investigator Tobias Schindler, at the Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute in Switzerland, wrote to The EastAfrican: It is not sure if asymptomatic cases of Palcifarum malariae infections ever will develop symptoms...there are cases where people lived for decades with this parasite without any reports of malaria-like symptoms.”

Prof Schindler said that while the mechanisms that this species uses to hide are still unclear, it is well adapted to humans and avoids detection by the immune system.

The men were later given three doses of artesunate/amodiaquine for three days. After four days, another set of tests was run and it was found that the parasite was no longer in their bodies.

There are five human malaria species, and all can be found in Tanzania. Plasmodium falciparum is the most common and dangerous one in Africa, and responsible for the majority of malaria deaths.

The other, Plasmodium vivax, was imported into Tanzania through Indian immigrants during the First World War.

Since 1917 there have been very few cases of this species reported in Tanzania. The other two are Plasmodium knowlesi and Plasmodium ovales. The fifth is alcifarum malariae.

The specie in question has been observed in an average of 15 per cent of malaria infections, and even in this instance, it was existing and causing disease alongside the common and more dangerous Palcifarum in children.

Dr Schindler said that it would be hard to distinguish between the species using a microscope alone, and recommends another approach.

“It is important to use new and better technologies such as Polymerase chain reaction (PCR).

This is a confirmatory technique that is more sensitive than microscopy and capable of identifying malaria parasites at the species level when microscopy was equivocal.

“PCR is an attractive addition to microscopy for confirmatory identification of Plasmodium spp. in clinical specimens, which are better at detecting disease, even when there are very few parasites in blood,” Dr Schindler wrote.

Tremendous progress

Tanzania has reported tremendous progress in combating malaria. The WHO reported that Tanzania’s under-five mortality had dropped from 112 per 1,000 in 2005 to 67 per 1,000 in 2016.

Additionally, the incidence of malaria dropped from 18 million cases per year to 5.5 million between 2008 and 2017, an estimated 60,000 child deaths averted annually.

These advances have been attributed to increased access to long lasting insecticide-treated nets and improved availability of quality assured Artemisinin-based combination therapies.

However, challenges exist as the fight against malaria intensifies in Tanzania. One is lack of diagnostic capacity in public health facilities to differentiate between these species, as well as detecting them at their lowest level in the blood.

Then there are the complications brought about by global warming.

Tanzania’s highlands—like many countries where malaria is endemic—are colder and uninhabitable for malaria, but could be at risk.

“Increasing temperatures, however, could transform many of these areas into stable malaria zones,” said the director for health at Ifakara Health Institute Dr Fredros Okumu.