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Chapter 14 : “Emerging” Neglected Tropical Diseases
Category: Clinical Microbiology; Bacterial Pathogenesis
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The vector-borne neglected tropical diseases (NTDs), such as the filarial infections (lymphatic filariasis and onchocerciasis) and the kinetoplastid infections (leishmaniasis, human African trypanosomiasis [HAT], and Chagas’ disease), often exhibit features that are characteristic of emerging infections. Among some key factors responsible for the emergence or reemergence of selected NTDs are conflict and human migration, urbanization and deforestation, and climate change. The chapter discusses each of these factors and their impact on the emergence and reemergence of specific NTDs in detail. The most common manifestation is cutaneous leishmaniasis, which is usually caused by Leishmania braziliensis, Leishmania mexicana, and related species in the Americas and Leishmania major and Leishmania tropica in Africa, Asia, and Europe. Trachoma is another NTD that has reemerged in the context of conflict and insecurity. Caused by ocular infection with certain serovars of the bacterium Chlamydia trachomatis, trachoma is the leading infectious cause of preventable blindness worldwide. Today in Latin America, urbanization has become an important social force for the emergence of both cutaneous and visceral leishmaniasis. The effect of rising world temperatures on the NTDs is seen primarily on the geographical distribution of vectors and reservoir hosts. Some of the factors related to the emergence or reemergence of these diseases are discussed and include conflict, deforestation, urbanization, and climate change.
Number of reported cases of HAT (bar graph) and the number of people screened (line graph) from 1939 to 2004. The implementation of novel control strategies circa 1939 helped bring the sleeping sickness epidemic under control ( 81 ).
Distribution of HAT in Africa along the conflict-ridden tsetse belt ( 25 ).