1. A paper presented at DIMACS Workshop on Economic epidemiology,
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
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What is Leishmaniasis
parasitic disease Transmitted by a bite of the infected female sand fly, that is usually infected with one species of Leishmania
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
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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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4. 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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5. 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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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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10. Cutaneous Leishmaniasis distribution
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11. 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 Leishmaniasis in Central and South America
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13. 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 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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16. 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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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
Repellents
Early diagnosis and treatment
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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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20. 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-poverty-malnutrition-disease!
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22. 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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26. 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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27. END.. THANK YOU and special thanks to DIMACS
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