Some perspectives of dynamics of
leishmaniasis infection in poor nations
by
J.Y.T. Mugisha* & Ibrahim M.ELmojtaba+
*Biomathematics Group, Makerere University
+University of Khartoum, Faculty of Mathematical Sciences
A paper presented at DIMACS Workshop on Economic epidemiology,
Makerere University,
3 – 5 August, 2009
Thursday, 30 June 2016
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1
What is Leishmaniasis
•
parasitic disease Transmitted by
•
About 30 species of sand flies can
become infected when taking a
blood meal from a reserviour host.
•
Most of the leshmaniasises are
zoonotic (transmitted from to
human from animals esp. dogs)
•
The human becomes a sole
reservoir if the transmission is
anthroponotic
a bite of the infected female sand
fly, that is usually infected with one
species of Leishmania
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Forms of the disease
•
Visceral leishmaniasis, (also known as kala-azar) the
most severe form in which the parasites migrate to
vital organs, and potentially fatal if un treated
•
Cutaneous leishmaniasis, the most common form which
causes a sore on the site of bite which heals in few
months to a year leaving unpleasant scar
•
Diffuse cutaneous leishmaniasis that produces wide
spread skin lesions (similar to leprosy) and very
difficult to treat, never heals spontaneously and tends
to relapse after treatment
•
Mucocutaneous leishmaniasis that starts with an ulcer
which spreads causing tissue damage esp. nose, mouth
There is also the Post-kala- azar dermal leishmaniasis
(PKDL) that is an illness condition got after cutaneous
(with depigmented eruptions mainly on the face, arms,
feet, upper part of the trunk etc)
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Symptoms-V Leishmaniasis
In children
•Vomiting, Diarrhea, Fever, Cough
In adults
•Fever for 2 weeks to 2 months,
along with fatigue, Weakness,
Night sweats, Weight loss etc…
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Symptoms-C Leishmaniasis
•
Skin sores
•
Skin ulcer
•
Erosion of tissue on the
mouth, tongue, gums, lips,
nose and inner nose
•
Swallowing difficulty
•
Stuffy nose, runny nose,
nosebleeds
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The disease
• The disease begins as an
erythematous papule at the site
of the sand fly bite on exposed
parts of the body. The papule
increases in size and becomes a
nodule. It eventually ulcerates
and crusts over. The border is
usually raised and distinct. There
may be multiple lesions,
especially when the patient has
encountered a nest of sand flies.
• The ulcer is typically large but
painless unless there is secondary
bacterial or fungal infection
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Disease…
• The mucosal form
usually occurs after an
initial cutaneous
infection and they
usually begin in the
nose or palate (WHO
fact sheet, 2003).
• Lesions progress to
destruction of mucosa
and even cartilage.
They result in scarring
and disfigurement and
can cause pulmonary
aspiration and death.
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Deformities
• Cutaneous leishmaniasis
can become disseminated
(diffuse cutaneous
leishmaniasis), especially in
immunosuppressed
persons. This can result in
deformities and disfiguring
of the face
• This illness can go on for
years. Patients with human
immunodeficiency virus
(HIV) infection are
particularly susceptible.
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8
Distribution
•
Although cutaneous leishmaniasis
can be traced back many hundreds
of years, one of the first and most
important clinical descriptions was
made in 1756 by Alexander
Russell following an examination
of a Turkish patient
•
Mainly a disease of Developing
world and rarely known in
developed world
•
Now endemic in 88 countries on
five continents. Bangladesh,
Brazil, India,, Nepal, Sudan, Peru,
Saudi Arabia, Syria, Afghanistan,
Iran (check WHO sheet for
numbers)
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Cutaneous
Leishmaniasis
distribution
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Distribution examples cont…
Distribution of
cutaneous
leishmaniasis
caused
by L. major with a
rodent reservoir
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Distribution Cont…
Distribution
of
Leishmania
species
causing
cutaneous
Leishmaniasi
s in Central
and South
America
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12
Public Health Concerns
•
WHO estimated that the
global prevalence of all
forms of these diseases is
12 million cases and that
the annual incidence is 1.5
- 2 million cases.
•
Of human diseases caused
by protozoan parasites,
visceral leishmaniasis
alone comes second in
public health importance
(after malaria) as
measured by DALYs
(Disability Adjusted Life
Years) (Markle & Makhoul
(2004) ).
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Public concerns…
•
Cutaneous leishmaniasis occurs
throughout the Americas from
Texas to Argentina, and in the
Middle East and North Africa.
The condition is diagnosed
every year in travelers,
immigrants, and military
personnel. It is endemic in 88
countries throughout Africa,
Asia, Europe, and North and
South America (Dedet and
Pratlong, 2003).
•
There are an estimated 12
million cases worldwide, with
1.5 to 2 million new cases each
year. Leishmaniasis is a disease
associated with rural areas and
poverty, but it has adapted to
the urban environment as well.
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Public Concerns…
• As a disease very closely associated
with poverty, leishmaniasis usually
affects the poorest people of the
poorest countries; 72 of 88 countries
affected are developing and 13 of
them are among the least developed.
It is here where more than 80% of
the population earns less than US$2
per day (Davis et al 2003).
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Control of Leishmaniasis
• No effective vaccine exists against the disease and no
prophylactic drugs.
• Treatment is expensive and frequently followed by a
relapse.
• Current means of control are aimed at the sand fly
vectors
• No preventive vaccines or drugs
(Reithinger, 2007)
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16
Control…
Vector control
– Insecticide spraying
– Genetic control
– Biological control
– Chemical control
Are these manageable in poor countries?
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Intervention targets
• Control of animal reservoirs
– Drugs
– Vaccine
• Personal protection
– Vaccine
– Repellents
• Early diagnosis and treatment
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18
Exams and Tests
Tests include:• Biopsy of the spleen and culture
• Bone marrow biopsy and culture
• Direct agglutination assay
• Skin Biopsy
• Complete blood count
• Montenegro skin test
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Possible complications
•
Deadly infection due to immune system damage
•
Disfiguration
•
Hemorrhage (bleeding)
•
Treatment: Medicines called antimony –containing compounds, Amphotericin B,
Pentamidine often expensive
•
Treatment cycle cost $30 - $120.
•
In case of relapse, patient needs to be treated with far more toxic second line
medicine $60-$70
•
Amphotericin B has no side effects but costs > $1500
•
Plastic surgery unmanageable in developing countries
•
Removal of spleen (splenestomy) may be needed on drug-resistant cases, this is
very expensive surgical process in many cases these countries have not theatres
to carry out this procedure
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Poverty trap
• In some parts of Asia, a family in
which there is a case of leishmaniasis
is three times more likely to have
sold its cow or rice field, than
unaffected family; plunging it into a
vicious circle of disease-povertymalnutrition-disease!
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21
Need for a cost-effective control exits
•
•
•
•
•
WHO report 2006: no well-defined cost-effective
control exits. There is need to strengthen both active
case detection and diagnostic capacity in rural health
centres where most of the patients are usually
treated
Cost of medication and cost of admission to hospitals
as many of the drugs need intravenous admin
Unit costs of vector control and active case detection
need to be synchronized
Costs associated with public training, surveillance etc
Mathematical model
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Threat
• Co-infection with other emerging
infections rendering leishmaniasis a
neglected disease of Africa
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What are we doing?
• Mathematical models
• consider the dynamics of the disease between
three different populations,
-human host
-animal reservoir and
-vector population
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Model
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Basic reproduction number
•
•
•
•
numerical solution shows that human treatment is the key parameter
in the disease control among human population, but is not sufficient
to eliminate the disease, even if it is high and effective.
to eradicate the disease from the community high rate of human
treatment should be followed by vector control strategies by either
using treated bed-nets
or direct killing of sand flies, and reservoir control strategies either by
killing all infective reservoirs
or by separating all reservoir from humans to a safe distance.
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END..
THANK YOU
and special thanks to DIMACS
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