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Dengue

Dengue. ACVPM Board Review Ronald L. Burke, DVM, DACVPM. Dengue Disease Facts. Flaviviridae Four serotypes Most common arbovirus affecting man 100 countries, 2.5 billion at risk 50-100 million cases per year Sylvatic strains in monkeys Four clinical manifestations. Clinical Disease.

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Dengue

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  1. Dengue ACVPM Board Review Ronald L. Burke, DVM, DACVPM

  2. Dengue Disease Facts • Flaviviridae • Four serotypes • Most common arbovirus affecting man • 100 countries, 2.5 billion at risk • 50-100 million cases per year • Sylvatic strains in monkeys • Four clinical manifestations

  3. Clinical Disease • Undifferentiated illness • Classical dengue fever • “Break-bone fever” • Fever, myalgia, arthralgia, retro-orbital pain • Explosive outbreaks in adults and older children • Dengue Hemorrhagic Fever • Dengue Shock Syndrome

  4. DHF/DSS • Hypovolemia due to increased vascular permeability • Severity related to: • Age, race, viral strain, nutritional status • Hyperendemicity a requirement • Lifelong immunity (serospecific) • Vaccine challenges

  5. DHF/DSS • Exact mechanism unknown • Original antigenic sin • Immune mediated enhancement • Generally confined to children • 8-10 years old • Infants from immune mothers • Case Fatality Rate ~5%

  6. Disease resurgence • Incomplete eradication of vector • Increased global travel • Urban growth • Inadequate public health infrastructure • Inadequate vector control programs • ULV operations are focused on adults • Little residual activity and insecticide resistance

  7. Aedes aegypti • Primary vector of dengue fever • Highly anthropophilic • Day biter • Multiple feedings • Endophilic • “Clean” water producer • Artificial containers • Eggs are highly resistant to desiccation

  8. Aedes aegypti • Extrinsic incubation period affected by temperature • Anautogenous reproduction • Secondary vector for many other diseases • Yellow Fever • Chikungunya

  9. Vector Incrimination • Isolation of disease from wild-caught specimens • Vector infection with feeding on parasitemic host • Demonstration of vector ability to transmit disease • Field association between host and vector

  10. Types of transmission • Mechanical (filth flies and roaches) • Biological • Propogative (plague, rickettsia) • Cyclo-developmental (filiriasis, onchocerciasis) • Cyclo-propogative (malaria, African trypanosomiasis)

  11. Disease Transmission • Vertical Transmission • Transovarial • Transstadial • Venereal • Co-feeding

  12. Disease Transmission • Horizontal • Salivarian (malaria) • Stercorarian (American trypanosomiasis) • Regurgitation (plague) • Assisted escape (American trypanosomiasis) • Active escape (onchocerciasis) • Ingestion of vector (tapeworms)

  13. Sand Flies • Two genus • Lutzomyia (New World) • Phlebotomus (Old World) • Nocturnal feeders • Weak fliers • Diseases: • Sand fly fever (Mediterranean Basin) • Bartonella bacilliformis (Peru, Ecuador, Columbia) • Leishmaniasis

  14. Myiasis • Genus Calliphoridae and Cuterebridae most common • Cochliomyia hominivorax (Primary screwworm) • Chrysomya bezziana (Old World screwworm) • Dermatobia hominis (human bot fly)

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