Neglected Tropical Diseases and Malaria: The need for mapping

Neglected Tropical Diseases and Neglected Tropical Diseases and Malaria: The need for mappingMalaria: The need for mapping

Neglected Tropical DiseasesNeglected Tropical Diseases

Diseases of poverty and of the poor

Neglected in terms of funding and efforts at their control

Schistosomiasis Chagas Disease Buruli ulcer STH Onchocerciasis Lymphatic Filariasis Dengue fever HAT Leishmaniasis Trachoma Leprosy

OnchocerciasisOnchocerciasis

Elimination of onchocerciasis in AfricaElimination of onchocerciasis in Africa

Prospects– Preventive Chemotherapy– MDA through CDTI

Challenges– Loa loa– Determining transmission zones

MDA and eliminationMDA and elimination

MDA and eliminationMDA and elimination

Transmission zonesTransmission zones

Factors to determine transmission zones based on species distribution– Vector cytospecies identification– The frequency of polymorphic inversions – The identification of non-vector cytospecies in

adjacent areas

Species identification in MalawiSpecies identification in Malawi

Mapping of vector distributionMapping of vector distribution

Chromosomal inversion dataChromosomal inversion data• Frequency of polymorphic inversions: Maegga et al in press

Centromere of chromosome 3

Vector migration issues and determination of a Vector migration issues and determination of a transmission zone (Maegga et al in press)transmission zone (Maegga et al in press)

Man-made ecological changes Man-made ecological changes

Wilson et al (2002)

LeishmaniasisLeishmaniasis

• Ghana: first reported in 1999 from 3 sub-districts; Ho/Shia, Kpedze/Vane and Tsito of the Ho District

• 1996-1998 –Burkina Faso• Late 1990’s till now – Mali

Leishmaniasis in Ghana and other Leishmaniasis in Ghana and other West African countriesWest African countries

What is known in outbreak areasWhat is known in outbreak areas

Parasite species identified

Vector species in some areas identified

Others not known but attempts being made All belonged to the

genus Sergentomyia, ◦ S. simillima, (31%)◦ S. ingrami, (23%)◦ S. africana africana (14%)◦ S. antennata

Species composition of blood-fed sand flies

38.2%

0.4%26.9%

34.5%

S.simillima

S. ingrami

S. a. africana

S. antennata

73% 69%

27%

0%

0%10%20%30%40%50%60%70%80%

Per

cen

t

Chicken Human Goat Bovine

Host

Total percentages of reactive sand flies feeding on the 4 blood meals

Blood-fed sand flies

What is not knownWhat is not known

What climatic factors led to the series of outbreaks in West Africa?

What are the reservoir hosts?Can the situation in the late 1990’s be

modeled to provide some insight into future outbreaks?

SchistosomiasisSchistosomiasis

Current mapsCurrent maps

Clustering of infection within a communityClustering of infection within a community

to understand the spatial distribution of disease in order to achieve a better epidemiological analysis towards an effective control strategy for the disease in the community

Need for mappingNeed for mappingWater-related development projects: e.g. in

Ghana building of a new dam– How is it going to influence prevalence in the

new area?– Can this be predicted?• Identification of S. bovis/S. haematobium hybrids How does that change the epidemiology? How will that influence the predictive maps already

available?

• Create a household level map of infected cases within the community

Lymphatic filariasisLymphatic filariasis

Need for mappingNeed for mapping

Why is MDA not working in certain areas of the same country?

Can information gathered from such areas be used to develop a predictive map of areas where MDA may not lead to elimination?

Vector-borne Viral diseases:Vector-borne Viral diseases:Dengue and Yellow feverDengue and Yellow fever

Aedes transmitted Emerging especially

dengue Impact of climate

change Less studied in most

endemic countries especially in Africa

Malaria: MARA MAPSMalaria: MARA MAPS

MARA MALARIA PREVALENCE MAPMARA MALARIA PREVALENCE MAP

These models analyse the malaria data against some environmental determining factors (such as climate, altitude, vegetation cover, agro-ecological zones, etc.). The level of prevalence is then predicted for the entire country or region, based on the established relationships between malaria prevalence and environmental data

Duration of Malaria transmission seasonDuration of Malaria transmission season

Current mapsCurrent maps

None of the maps has entomological information– Different species have different vectorial capacities– Insecticide resistance will influence transmission

even in the face of control measures– If data is obtained from area of permanent water

body e.g. dam, it will influence the seasonality maps

In the era of malaria elimination/eradication these maps are inadequate

Thank youThank you