The Devastating weed that favours mosquitoes and is the probable cause of widespread malaria incident in East Africa
The malaria-causing mosquitos have found a new safe
haven in an invasive plant previously known to be habitat in South and North America.
Researchers from Kenya-based International Centre of
Insect Physiology and Ecology (icipe)
say they generated new evidence of the immense threat posed by a highly
destructive invasive plant, known scientifically as Parthenium hysterophorus.
They say the invasive plant
believed to have entered East Africa through Ethiopia could be linked to the probable escalation of malaria
incidents in East Africa.
The researchers in a study published
mid-last month (https://rdcu.be/cpfvh
the weed, nicknamed ‘famine weed’ due to its phenomenal adverse impact on
people’s health, agriculture, livestock and the environment, has contrastingly
favourable effects on Anopheles
mosquitoes, which transmit the malaria
Also, the researchers note the
possibility of exploiting the Parthenium
-mosquito relationship to
control the insects whose effects immensely contribute to Africa disease burden.
“In general, mosquitoes lay their
eggs in standing water. However, we have established that Parthenium
releases from its roots, chemicals known as terpenes that have a distinct blend
of mosquito-attractive fragrances. When these chemicals leak into stagnant
water, they enhance its attractiveness as an egg laying site for mosquitoes, in
comparison to plain water,” explains Prof. Baldwyn Torto, Head, icipe
and Chemical Ecology Unit (BCEU).
Professor Torto said their research
further demonstrates that preference has major implications on the ability of
mosquitoes to survive and thrive.
root chemicals enable
mosquito larvae to emerge two to three days earlier, and they also extend the
lifespan of the adult mosquitoes arising from the contaminated breeding sites
to a week longer than normal, thus boosting their chances to bite people and
transmit the malaria parasite.” he said
These findings are especially
significant considering that Parthenium –
a native of North and
South America and one of the world’s most devastating invasive plants – is
widely spread across East Africa including in flooding-prone malaria
Parthenium aggressively colonises its invaded regions, killing other
plants and reducing crop yields. It also produces a highly toxic compound
called parthenin that causes dermatitis, hay fever and asthma in people,
poisons animals and contaminates meat and dairy products in livestock that has
fed on it.
Farmers in Ethiopia named Parthenium hysterophorus: “Faramsissa,” or
“sign your land away.”because of its colonizing nature with to wipes out other biodiversity.
In 2015, icipe
published a seminal study that made the first global
connection between Parthenium
The research demonstrated that the
weed is a preferred nectar source for Anopheles
mosquitoes and it
can sustain these insects by extending their lifespan even in the absence of a
blood meal from people.
Researchers also found that the female
mosquitoes that feed on Parthenium
longer, accumulate substantial energy reserves and they are capable of laying
“Importantly, the researchers found
that parthenin does not have the same toxic effect on adult female mosquitoes
as it does on people and animals, indicating that the insects can tolerate and
possibly detoxify themselves of the compound” reads part of the findings.Prospective
“Our recent findings present a
silver lining in that the chemical fragrances found in the roots of Parthenium
could be used as a bait in combination with traps, to selectively capture pregnant
female mosquitoes seeking egg laying sites,” explains Trizah Milugo, a Kenyan
student who conducted the study as part of her PhD research based within the icipe
“We also noted that only half of the
eggs deposited in water containing these chemicals hatched. We singled out
parthenin as being responsible for the low egg hatch rate, meaning that female
mosquitoes can compensate the cost of exposing their juveniles to plant toxins
for improved survival as adults.”
“Globally, invasive species are considered one of the most important perils to
nature due to their severe impact on many socio-economic aspects,” notes
Dr Segenet Kelemu, icipe
Director General & CEO
“Africa is one of
the most susceptible regions, with a long and diverse list of such menace.
has prioritised the management of invasive species as a
key area of focus.”
Studies have found that a single mature
Parthenium plant produces a minimum of 25000 and a maximum of 100,000 seeds The
seeds are then dispersed by vehicles, wind, water, machinery, animals, and
along with fodders and grains.
hysterophorus was in 2015 identified by NEMA as one of the dangerous invasive
plants in Uganda. The national biodiversity strategy 2015 -2025 list among the invasive plants threatening biodiversity.
But it is common to find the
wed thriving along the roads side.
Studies within Uganda indicate
that it may have invaded the country less than a decade ago.
was first identified at Bugembe and Mbikko near Jinja in 2008. It has since 2010
been listed among the top invasive plants devastating Queen Elizabeth
National Park poisoning cattle, buffalos and antelopes. It reportedly causes allergic
reactions in humans after prolonged contact.