Transcript herbal antimalarial? - World Agroforestry Centre

African medicinal plants
against malaria
Dr Merlin Willcox, RITAM
(Research Initiative on Traditional
Antimalarial Methods)
Meeting Objectives
To share information
To develop a collaborative action
programme for Africa-wide production
and distribution of appropriate herbal
antimalarials
The economics of malaria
2-5 billion febrile episodes a year
resembling malaria
500 million cases of malaria
1.1 million deaths
90% of deaths are in African children
58% of deaths in poorest 20% of
population
Economics of malaria (2)
Up to 75% use traditional herbal
medicine as first line treatment
Adult course of ACT = $2.4, may reduce
to $1
Diagnostic test = $1
Big pharma is not investing in malaria
What is your main objective?
To reduce malaria mortality and
morbidity?
To create jobs and businesses?
What is your market?
Poor people in remote areas with no
access to modern health care?
People who already have access to
modern pharmaceuticals?
Public health programmes?
Herbal prophylactics for ex-pats?
What is an “appropriate” herbal
antimalarial?
Standardised phytomedicine or homegrown plants?
Cheaper than ACTs?
Parasite clearance or adequate clinical
response?
Efficacy or cost-effectiveness?
Depends on context….
Types of R&D:
Different products, endpoints &
methodologies
Bioprospecting for active molecules:
new leads for conventional drug
development
Phytomedicines: standardised herbal
extracts.
Traditional medicine: prepared
according to traditional formulations
The competitive advantage of
herbal antimalarials
Affordable
Available
Sustainable
Reach the parts that modern drugs
don’t reach…
Ways of using plants against
malaria
Insect repellents
Vector Control
Prophylaxis
Treatment
The limitations of traditional
medicine
There is little clinical data on safety and
efficacy
Content of active compounds in plants
is variable
There is no consensus on what plants,
preparations and dosages to use
These are all remediable, through
research…
RITAM
Research Initiative on Traditional AntiMalarial Methods
Founded in 1999 by GIFTS of Health,
with support from TDR, Rockerfeller
www.gifts-ritam.org
Specialist Groups
Policy, Advocacy and Funding
Networking, publications, funding, ethics,
intellectual property rights
Preclinical
Database, guidelines
Clinical Development
Database, systematic reviews, guidelines
Insect repellence and vector control
Database, systematic reviews, guidelines
Artemisia annua Task Force
Overview of literature
Clinical trials planned
The bottom line
Herbal insect repellents: some evidence
Herbal insecticides: some evidence
Herbal treatments: controversial, some
clinical evidence
Herbal prophylactics: NO clinical
evidence
Chicken or egg?
“Show us the evidence that it works”
Who will pay to generate the evidence?
Herbal treatments
No herbal treatments have yet been
described to be as efficacious as ACTs
for parasite clearance
Several herbal treatments could
potentially be more cost-effective than
ACTs in certain contexts
Where could herbal antimalarials be
more cost-effective?
Home management
Presumptive malaria
Semi-immune patients (Adults, children
> 5 years old)
When is it unethical to recommend
herbal antimalarials?
[on current evidence]
Non-immune patients
Children aged <5
Pregnant women
? If a proven treatment is locally
available and affordable to the patient?
The Artemisia annua debate
Jansen, 2006: “I believe that the herbal
tea approach to artemisinin as a
therapy for malaria is totally misleading
and should be forgotten as quickly as
possible”.
Anamed: promoting A. annua
cultivation and use as a tea.
RITAM response: Need more research
Approaches to A. annua
Grow the plant as a cash crop, to sell to
pharmaceutical companies, which will
make ACTs
Grow the plant for local distribution as
tea bags
Grow the plant in village “green
pharmacies” where no other healthcare
is available.
Problems with A. annua tea
High level of recrudescence at doses
tested
Optimal method of preparation and
dosage not yet defined
Variability in artemisinin content
Potential of A. annua tea
Cheaper than ACTs
Could it be more cost-effective in
certain situations, e.g. for home
treatment of malaria?
Could it be more effective if combined
with other herbal antimalarials?
Prophylaxis
Many herbal prophylactic preparations
are used
Almost none have been investigated
Some Hausa tribes have lower than
expected incidence of malaria (Etkin &
Ross, 1991)
In the malaria season, they eat plants
with antimalarial properties
Neem as a repellent
Neem oil on cardboard mats is as
effective as synthetic repellents
Costs $0.50 per room per year (cf. $25
for synthetic repellents)
Also effective topically (2% in coconut
oil) for 12 hours
Neem oil is larvicidal (LC50 = 3-8ppm)
Phytolacca dodecandra
Widespread tropical plant
Crushed, powdered berries used as
soap and as pesticide
Effective at killing schistosomiasis
transmitting snails
Effective at killing mosquito larvae
24HR MORTALITY RATES OF
Aedes aegypti LARVAE
100
% MORTALITY
90
80
Control
25ppm
50ppm
Vectron
70
60
50
40
30
20
10
0
0
5
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
DAYS POST TREATMENT
Possible roles for medicinal
plants
Vector control and repellence
Prophylaxis
Treatment, especially:
Presumptive malaria
Home management
Adults and children >5
Conclusions
Herbal antimalarials have huge potential
More research IS needed (esp clinical
and public health)
But who will pay for it?
Need to go beyond laboratory studies in
order to deliver a health impact.
www.gifts-ritam.org