Malaria Prevention: Treating Silent Malaria Cases Can Stop Spread of Disease

Treating silent malaria cases can prevent the spread of disease to others, according to a new study conducted by the University of Maryland School of Medicine (UMSOM).

In regions where malaria illness is widespread, it is common to find many individuals who are infected with malaria parasites (Plasmodium falciparum), but without symptoms.

Malaria - Causes, Symptoms, Diagnosis, Prevention, Treatment
Malaria is caused by a parasite that enters blood through the bite of an infected mosquito. It is characterized by fever, vomiting, shivering, sweating and other symptoms.

‘Most of the malaria parasites (Plasmodium falciparum) are being carried by people who are not sick. Treating these silent carriers of malaria, who don't have symptoms, could help stop the spread of disease.’

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UMSOM researchers conducted a study of 114 participants in Malawi ranging from children to adults to better understand the role asymptomatic malaria infections have in the spread and occurrence of malaria illness. It is the first study to use prospective, longitudinal detection of asymptomatic malaria infection to examine the subsequent risk of malaria illness among all ages.

These asymptomatic infections may never develop into illness, but they are an important contributor to the spread of malaria and pose a public health challenge.

"We know that in Malawi, like many parts of Africa, most of the malaria parasites are being carried by people who are not sick. They don't get treatment for their infections, because of their infections a silent, but when they get bitten by mosquitoes, they can transmit malaria" said Miriam Laufer, MD, MPH, Associate Professor of Pediatrics and Associate Director for Malaria Research in UMSOM's Center for Vaccine Development and Global Health (CVD).

Malaria - Protection Strategies
Malaria is a dangerous disease with lethal consequences that requires protective measures for prevention and control of malaria in endemic regions of the world.

Researchers examined the association between asymptomatic malaria infections and subsequent risk of malaria illness and demonstrated that carrying P. falciparum infection without symptoms was associated with a 50% decrease in the risk of malaria illness.

Using a genotyping method to determine the molecular fingerprint of each parasite, they discovered when people who have asymptomatic malaria infection and get sick from malaria, it is because they acquire a new infection (from the bite of a mosquito) rather than having the asymptomatic infection develop into clinical disease.

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With new infections, adults and children with and without asymptomatic infection were equally likely to get sick. The researchers concluded that asymptomatic infection did not protect against new infections that made them sick.

"We have always worried that if we give medicine to treat malaria to people with asymptomatic infection, they might get sicker the next time they get malaria. This has been a challenge to introducing new policies like mass drug administration or screening and treating campaigns to interrupt malaria transmission.

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Our results suggest that treating asymptomatic infection will not lead to increased risk of disease in the short term. Now we need to evaluate these new interventions to determine the long-term impact both on the individual's health and also on malaria transmission" said Dr. Laufer.

Researchers enrolled participants seeking treatment for uncomplicated malaria at the Mfera Health Centre in Chikhwawa district in Malawi between June 2014 and March 2015. Subjects were eligible if they had symptomatic P. falciparum infection, detected by malaria rapid diagnostic test (RDT) and confirmed by microscopy, and were HIV-negative at time of screening. They were treated for their initial illness and then followed every month and evaluated every time they were ill.

Source-Eurekalert