Icipe scientists find invasive weed helps spread of malaria

A highly invasive weed found in several parts of Kenya has the potential of increasing incidence of malaria, a new study shows, raising the risk of rolling back gains against the killer disease.

A study by the International Centre of Insect Physiology and Ecology (Icipe) has found that famine weed (parthenium hysterophorus), has the ability to extend the lifespan of the malaria-transmitting mosquito, anopheles gambiae, even in the absence of a blood meal.

“Our results show that when female anopheles mosquitoes feed on parthenium, they survive much longer, and they also accumulate substantial energy reserves,” Icipe scientist and lead study author Baldwyn Tortor said in Nairobi last week. The study was published recently in the journal PLoS ONE.

The finding is a setback to the fight against malaria that has seen injection of billions of shillings towards preventive measures as well as search for vaccine. Malaria claims about 23,000 lives in Kenya annually.

In the current fiscal year, the Treasury set aside Sh19.7 billion to fight HIV/Aids, malaria and tuberculosis

Mr Tortor said: “Specifically, the mosquitoes are able to store lipids, the most efficient form of energy that has high caloric value and is critical in a variety of functions in the insects.

For instance, lipids have been implicated in the development of embryos in mosquitoes and therefore their ability to reproduce.”

Famine weed, a native of North and South America, is considered one of the world’s most serious invasive plants. Its success as an invasive weed is based on its ability to adapt to harsh environmental conditions. In addition, the weed grows very fast, and is able to store large amounts of seeds in the soil.

Its seeds are also small and light and can be transported by a variety of mediums over long distances. In Kenya, the weed has colonised parts of the high-risk malaria regions in the Coast, Nairobi, Kisumu, Mbita, Homa Bay and other parts of western Kenya.

“In Kisumu, people only talk of the hyacinth. We have really tried to establish a local name for this toxic plant in vain. It is important to keep an eye on it,” said Mr Torto.

The weed, he added, produces a highly toxic compound called parthenin, which can cause dermatitis, hay fever and asthma in humans.