INTH 301/401 Fundamental Concepts in Global Health
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Transcript of INTH 301/401 Fundamental Concepts in Global Health
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INTH 301/401 Fundamental Concepts in Global Health
Ron BlantonCGHD, CWRU
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Infectious Agents of Disease
• Viruses• Bacteria• Parasites
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Viruses
• Acellular organisms• Nucleic Acids• Origins• Employ host cellular machinery to make
proteins, nucleic acid and new virus• Do not divide• Do not generate/manipulate energy• Miniscule
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Viral Structure
envelope
protein coat(capsid)
DNA or RNA0.01-0.1 μm
Negative strand
RNA polymerase
Ribosomes
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Classification
• Disease• Transmission• Nucleic Acid• Sequence
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Classification
• Disease– Cold– Hepatitis– Encephalitis– Hemorrhagic fever– Oncogenic
• Transmission• Nucleic Acid• Sequence
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Classification
• Disease• Transmission
– Respiratory– Enterovirus– Arbovirus
• Nucleic Acid• Sequence
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Classification
• Disease• Transmission• Nucleic Acid
– DNA– RNA
• Sequence
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Nucleic Acid Classification
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Classification
• Disease• Transmission• Nucleic Acid• Sequence
– International Committee on Taxonomy of Viruses
– 7 Genera DNA viruses– 15 Genera RNA viruses
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Classification Hemorrhagic Fever Viruses
• Disease– Rift Valley Fever – Lassa, SAHF– Marburg, Ebola – Dengue, Yellow Fever
• Nucleic Acid– RNA
• Sequence– Bunyavirus – Arenavirus– Filovirus – Flavivirus
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Life cycle
• Recognition - Receptor• Invasion• Transcription/translation or
translation/transcription• Packaging• Release
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RNA
Invading virion New virions
Cell membrane
Cap
CapCap
CapCap
Cap
RNA
Flaviviral Replication
Proteases
Mature proteins
Viral particle = virion
Receptor
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RNA
Invading virion New virions
Cell membrane
Filoviral ReplicationViral particle = virion
Cap CapCap CapCap CapCap Cap
RNA
Viral polymerase
Protein synthesis
Receptor
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Implications
• Rapidly reproduced to high density• Mutation• Easily transported• Wide host range (sometimes)• Limited range of viral poisons • Many modes of transmission
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Viral Tramission• Respiratory Measles• Respiratory-oral Colds• Urine-Respiratory Hanta pulmonary syndrome• Fecal-oral Rotavirus diarrhea• Direct contact Chickenpox• Veneral HIV• Congenital Rubella• Zoonoses Congo-Crimean Hemorrhagic• Vector borne Dengue• Transfusion Cytomegalovirus
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Virus and Disease
• Cytopathic effect• Inhibit DNA, RNA protein synthesis• Apotosis• Proliferation
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Viral Prevention/Treatment
• Isolation (migration)• Host Response• Vaccination• Antivirals
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Infectious Agents of Disease
• Viruses• Bacteria• Parasites
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Bacteria
• Simple cells• Cell membrane and wall (and envelope)• Reproduction by division
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Bacterial Structure
http://pathmicro.med.sc.edu/fox/protype.htm
LPS
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Gram Staining Reveals Structure
E. coli S. aureus
http://www.buddycom.com/bacteria/gnc.html
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“Bacterial Genetics”
• Bacteria & Archea• Eukaryotes
– Plant– Yeast– Parasites– Insects– People
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Implications
• “Rapidly reproduce” in the right context• Resistance• Persistance• Mutation/Gene transfer• Toxin production
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Bacterial Prevention/Treatment
• Contact• Host response• Vaccines• Antimicrobials/Antibiotics
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Infectious Agents of Disease
• Viruses• Bacteria• Parasites
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Parasites
• Single cell or multicellular eukaryotes living within a larger
• Complex developmental programs
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Conceptual Basis of Parasitism
Commensalism Mutualism Parasitism
SYMBIOSIS
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Host - Parasite Relationships
• Definitive host = Sexual reproduction– Echinococcosis - dogs– Schistosomiasis - humans– Pork tapeworm - humans– Malaria - mosquito
• Intermediate host = Asexual reproduction– Echinococcosis - humans– Schistosomiasis - snail– Pork tapeworm - humans– Malaria - humans
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Parasitism in Human Biology and Medicine
• Parasite – usually refers to protozoa and helminths• Distinction from other classes of infectious agents (bacteria and viruses) – historical
significance more than biological distinction• A ‘re-emerging’ cause of illness in industrialized nations.• Health impact greatest in developing nations and among impoverished people
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Classification
• Eukayrotes – membrane-bound organelles• Complex developmental programs
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Epidemiology and Clinical Characteristics
• Helminths (Macroparasites)
• Chronic and persistent infections
• Disease related to intensity of infection
• Asymptomatic, chronic • Aggregated distribution
• Protozoa (Microparasites)
• Usually acute and transient infections
• Disease initiated by small inoculum
• Asymptomatic, acute• Distribution is random
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Parasitic Protozoa
Single cell organismsMultiply in human host
Organelles analogous to tissues or organ systems
ApicomplexaInclude chloroplast-like structures
Malaria, toxoplasma
ArchezoaLack mitochondria, anaerobic
AmebaeGiardia lamblia
KinetoplastidaSingle large mitochondria
Trypanosomes Leishmania
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Parasitic Helminths
TrematodesFlukes
CestodesTapeworms
MulticellularDoes not multiply in hostSpecialized organ systems
NematodesRound worms
PlatyhelminthesFlat worms
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Transmission of Parasitic Diseases
• Fecal-oral route – common for food-borne pathogens, including Giardia lamblia and Entameba histolytica (protozoa), many geohelminths including Ascaris, Trichuris, Taenia (tapeworm) and Enterobius (pinworm)
• Vector-borne – includes mollusks (snails) and multiple arthropods (mosquitoes, black flies). Examples are schistosomes, lung flukes, filarial worms, leishmaniasis, trypanosomiasis, malaria
• Note: Vectors are required for completion of parasite life cycles. Not simply a vehicle for transfer to mammalian host.
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Parasite Disease Mechanisms• Physical damage – invasion, attachment to tissues, tissue consumption,
obstructions, parasite proteases and other products• Innate immune responses – TNF-a, other cytokine production• Immunopathology – host immune response leads to parasite containment
coincidental with secondary tissue damage• Spectrum of disease modified by transmission (i.e. intensity/chronicity of
exposure), parasite burden and innate factors (genetic, immunologic, developmental)
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Additional Courses
Medicine• INTH 484: Geographic Medicine and Epidemiology • INTH 494: Infectious Disease Epidemiology • INTH 5001: Orientation to International Health • FAMD 5023: International Health Practice• IMMU 3002 Tuberculosis and AIDS• IMMU 3003: Tuberculosis and History• EPBI 592: Geographic Information Systems and Statistical
Analysis of Spatial Data