Rare malaria parasite found in Turkana

Turkana County in northwestern Kenya was supposed to be the land that malaria forgot. With its arid and windy climate, its climate was thought to be too dry for the mosquitoes that carry malaria-causing parasites, and thus was excluded from national efforts to prevent the disease.

However, a recent study conducted by researchers from Moi University in Kenya and the Duke Global Health Institute has annulled this assumption.

Worse still, the findings raise concerns about the emergence of new forms of the disease that could jeopardise the progress made in malaria control in East Africa.

The research team said in a paper in the Journal Emerging Infectious Diseases last Thursday, that they had discovered that approximately 30 percent of the individuals tested in Turkana County had malaria parasites in their blood, indicating that the disease was already endemic in the region. What is even more alarming is the identification of a parasite called Plasmodium vivax, which was historically rare in Sub-Saharan Africa. This study is the first to confirm cases of locally transmitted P. vivax malaria in Kenya.

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The appearance of this parasite may be linked to an invasive mosquito species known as Anopheles stephensi, which has over the past decade been detected in five countries in northern Africa. In 2016, when Anopheles stephensi arrived in Djibouti, there was a 100-fold surge in malaria cases, prompting the World Health Organisation to issue a warning about the insect’s invasion and its potential threat to malaria control and elimination in Africa.

Challenges ahead

According to Eric Ochomo, a medical entomologist with the Kenya Medical Research Institute (Kemri), both the invasive mosquito and the P. vivax parasite pose significant challenges to malaria control efforts in Africa.

P. vivax behaves differently from the most common forms of malaria found in Africa, which enables it to evade screening tests and therapies commonly used on the continent. Moreover, it can remain dormant in the liver, leading to relapses weeks or even months after the initial infection.

“If we don’t do something about it, we’re going to be in trouble very soon,” says Ochomo, who identified the invasive species in northern Kenya in December 2022.

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Dr Wendy O’Meara who has been working on malaria prevention in Kenya since 2003 said: “There are no measures in place for P. vivax malaria control in Kenya, and it needs some targeted mechanisms.”

These mosquitoes, originally from India, thrive in areas with poor sanitation and dirty water, making them adaptable to urban environments. Ochomo warns that regions previously considered low risk or nearing elimination may experience a surge in P. vivax cases.

The fact that they are breeding successfully in hot, dry regions like Turkana should cause public health officials to rethink their assumptions about malarial hot spots, Ochomo says.

“Areas that are either approaching elimination or that are categorised as low risk are going to end up with higher prevalence than they currently see,” he warns.

In response, Kenya’s National Malaria Control Programme is now intensifying efforts to distribute mosquito nets and enhance malaria surveillance in Turkana County. Additionally, the researchers plan to collaborate with local communities to identify and eliminate potential mosquito breeding sites.

The potential increase in P. vivax cases could also undermine the assumed genetic protection against the parasite spreading in Africa. Many Africans possess a genetic trait believed to offer some resistance against P. vivax infection, resulting in relatively few cases.

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However, recent outbreaks suggest that even individuals with this genetic protection might be vulnerable to the evolving parasite.

“There are signs that recent outbreaks may be affecting even those with the genetic protection, a reminder that the parasite is constantly evolving new ways to evade defenses,” O’Meara emphasised.