Low serum iron may help dengue virus grow and flourish, finds recent study

Dengue fever is a disease spread by mosquitoes in the tropics causing fever, rash, terrible aches and shock in some cases. It is the cause of about 60 million cases a year, with 18% requiring hospitalization and about 13,600 deaths, and costs about $9 billion annually worldwide. Therefore scientists are always on the lookout to curb spread of this deadly disease.

In a recent study, researches have reported that serum iron in human blood influences the acquisition of dengue virus by mosquitoes. The findings have appeared in the journal Nature Microbiology.

According to the study, the dengue virus acquisition by Aedes aegypti was inversely correlated with the serum iron concentration from human donors. In a mouse–mosquito acquisition model, iron supplementation reduced the prevalence of dengue virus and viral load. On the other hand, neutralization of serum iron facilitated dengue virus infection in A. aegypti mosquitoes.

Mosquitoes feeding on iron-deficient (sideropenic) mice exhibited a higher prevalence of dengue virus. Reversal of the sideropenic status of hosts largely reduced dengue virus acquisition and infection by mosquitoes, noted the researchers.

The results imply that supplementing people's diets with iron in places where both iron deficiency anemia and dengue fever are a problem could potentially limit transmission of the disease, but there are risks.

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Dengue is most commonly acquired in urban environments, and the expansion of cities in the tropics has been accompanied by an expansion in dengue infections. A vaccine exists, but it can actually make the disease worse if given to someone who has never been previously infected. Public health officials are actively looking for ways to reduce the prevalence of the disease.

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Penghua Wang, University of Connecticut Health Center, Farmington, CT, USA, and colleagues wanted to see if blood quality had an impact on the spread of the dengue virus. Blood levels of various substances can vary tremendously from person to person, even among healthy people. To explore the idea they ran a series of experiments.

They collected fresh blood from healthy human volunteers, then added the dengue virus to each sample. Then they fed the blood to mosquitoes and checked how many mosquitoes were infected from each batch. They found it varied quite a lot. And the variation correlated very closely with the level of iron in the blood.

"The more iron in the blood, the fewer mosquitoes were infected," says Wang. The team found it held true in a mouse model, too: mosquitoes feeding on mice infected with dengue were much more likely to acquire the virus if the mice were anemic.

The reason has to do with the mosquitoes' own immune systems. Cells in a mosquito's gut take up iron in the blood and use it to produce reactive oxygen. Reactive oxygen kills the dengue virus.

"In areas where dengue is endemic, iron deficiency is more common. It doesn't necessarily explain it, the high prevalence of dengue...but it could be possible that iron supplementation could reduce dengue transmission to mosquitoes in those areas," Wang says. But there's a big caveat.

Malaria tends to be common in the same areas as dengue. And plasmodium, the microorganism that causes malaria, thrives in an iron-rich environment and might actually worsen if everyone is supplementing with iron. Public health authorities need to weigh the costs and benefits before embarking on any population-wide supplementation program.

In any case, Wang says, understanding how dengue is transmitted will help public health authorities and scientists develop new ways to control the disease, and hopefully similar viruses such as Zika and West Nile virus as well.

The bottom line of the study is --> The more iron in the blood, the fewer mosquitoes are infected.

To read the complete study log on to https://doi.org/10.1038/s41564-019-0555-x