Scientists Suggest Herbal Solution To Control River Blindness

Worried by lack of suitable medicines for the treatment of human onchocerciasis and the emergence of ivermectin-resistant
nematodes of veterinary importance,
researchers have identified Margaritaria
discoidea and Homalium africanum plants
as potential source of medicines for the
treatment of this disease.
Researchers testing these popularly plants
used in the traditional treatment of
onchocerciasis in North West Cameroon in
the laboratory, found out that non-polar
extracts of M. discoidea and H. africanum
roots and/or leaves are potential sources of
new microfilaricidal compounds for the
treatment of onchocerciasis.
Margaritaria discoidea and Homalium
africanum are acclaimed effective in the
treatment of onchocerciasis by traditional
medicine practitioners in North West
Cameroon. In the area, the dried plant
material is ground into powder which is
consumed directly, or boiled in water and
the decoction drunk.
Onchocerciasis, also known as river
blindness is a parasitic disease caused by
Onchocerca volvulus, a parasitic worm that
is spread through the bite of a black fly
which breeds in fast-flowing rivers and
streams. When the fly bites, it deposits the
larvae of a parasitic worm, which matures
to adulthood and produces millions of tiny
worms, called microfilaria that migrates
throughout the body.
When the microfilariae migrate throughout
the body and give rise to a variety of
symptoms such as rashes, lesions, intense
itching and depigmentation of the skin;
lymphadenitis, which results in hanging
groins and elephantiasis of the genitals,
general debilitation and serious visual
impairment, including blindness.
Usually, many bites are necessary before
the infection to cause symptoms. Thus, the
infection is much less likely to develop in
visitors to affected areas. But the symptoms
occur when the microfilariae die. Their
death can cause intense itching, which may
be the only symptom.
A rash with redness may develop. Over
time, the skin may thicken, roughen, and
wrinkle. It may lose its pigment in patchy
spots. Lymph nodes, including those in the
genital area, may become inflamed and
swollen. Nodules containing adult worms
may be seen or felt under the skin.
The vast majority of infections occur in sub-
Saharan Africa and experts estimate that 18
million people are infected with river
blindness, 6.5 million suffer from severe
itching or dermatitis, 770,000 people suffer
serious sight impairment, and 270,000 are
blind.
However, researchers reported in the 2010
Middle East African Journal of
Ophthalmology that the level of knowledge
and attitudes of rural/semi-urban
communities, as depicted by this study that
was carried out in Ife North Local
Government Area of Osun State, was very
low.
The study on the perception and attitude of
people toward river blindness in south
western Nigeria by AO Adeoye and AO
Ashaye from the Ophthalmology
Department, University College Hospital
(UCH), Ibadan, Oyo State and OH Onakpoya
from the Ophthalmology Unit, Obafemi
Awolowo University Teaching Hospital
(OAUTH), Ile-Ife, Osun State indicated that
river blindness was well known by its local
name among 458 (91.6 per cent) of the
respondents.
Nonetheless only seven (1.4 per cent) knew
that it affects both the eyes and skin and
the cause was commonly attributed to
impure blood by 114 (22.8 per cent),
whereas transmission was thought to be
through fomites by 161 (32.2 per cent).
Only 12 (2.4 per cent) respondents
attributed the disease to black fly bites.
Fomites are inanimate objects that carry
disease-causing germs that spread
infections.
The researchers’ prepared16 crude extracts
of the various parts of M. discoidea and
leaves of H. africanum using different
organic solvents such as hexane and
methanol. Their filaricidal activities were
then determined using motile microfilariae.
Also investigated was their toxicity on
monkey kidney epithelial cells and in mice.
The study found that four out of the 16
extracts showed microfilaricidal activity
based on motility reduction, and no form of
acute toxicity wasobserved in mice.
Burkill H.M in his book entitled “The useful
plants of West tropical Africa” wrote that
Homalium africanum is called ekalado in
Edo and oyuru uguru in Igbo.
Margaritaria discoidea is a tree reaching
height of 30m and called emi in Yoruba,
ka’danya in Hausa and osisi in Ibo. It is
common in Senegal, western Cameroon, and
the rest of tropical Africa. The stringy and
fibrous bark is commonly used as a
purgative in West Africa and as worm
expeller in Central Africa.
The Fula of Sierra Leone use the bark for
toothache while in Central Africa Republic its
decoction is used for the relief of post-
partum pains. In Congo (Brazzaville) the
bark decoction is also used to relieve
stomach and kidney complaints and to
facilitate parturition. In Malawi, powdered
bark-extract is applied to swellings and
inflammation for quick relief.
According to scientists in a study they
entitled “Anti-inflammatory and analgesic
activities of the aqueous extracts of
Margaritaria discoidea (Euphorbiaceae) stem
bark in experimental animal models” which
was published in the 2009 edition of the
journal International Journal of Tropical
Biology, this plant extract exhibited anti-
inflammatory and analgesic activities.
Adeolu A. Adedapo from the Department of
Veterinary Physiology, Biochemistry and
Pharmacology, University of Ibadan;
Margaret O. Sofidiya from the Department
of Pharmacognosy, University of Lagos and
Anthony J. Afolayan from the Department of
Botany, University of Fort Hare, South Africa
based on their finding wrote: “The study
has thus provided some justification for the
folkloric use of the plant in several
communities for conditions such as
stomachache, pain and inflammations.”
Over the years, black fly, the vectors of
river blindness have been controlled by the
use of synthetic chemical compounds and
this is known to leave behind toxic chemical
residues which get accumulated into the
food chain. Attempt is therefore carried out
to develop alternative control of insect
vectors of parasitic disease through the use
biodegradable plant materials.
An assessment of ethanol extracts of five
plants, namely Parkia biglobosa
(Dawadawa tree), Vitelaria paradoxa (shea
butter tree), neem, Chromolaena odorata
(Siam weed) and Lippia multiflora (Efinrin
gogoro in Yoruba) found that siam weed
was the most potent of the five plant
extract while shea butter tree was the least
potent to control black fly.
Matar B. Malau and Davou B. James from the
University of Abuja reporting in the 2008
edition of The Internet Journal of
Toxicology said considering that C. odorata
recorded 73.09 per cent larval mortality per
three hours of exposure time while other
crude extracts (L. multiflora, P. biglobosa, A.
indica and V. paradoxa) recorded 43.75 per
cent, 48.79 per cent, 33.95 per cent and
27.18 per cent, they might be of use in the
control of black fly.