1. Epidemiology Molecular epidemiology, Microbial Ecology, Vector Ecology and Population Biology

2. Tracking microorganisms through space Spatial distribution of organisms may depend on: Geographic range Habitat specificity Host specificity Ecosystem specificity Site or tissue specificity

3. Microbes are everywhere Microbes are found all over the world in virtually every habitat and in/on most organisms as symbionts Free living microbes may sometimes become opportunistic parasites Humans’ non-specific defenses help to protect from these opportunists Some microbes are specialized pathogens and have specific abilities and requirements to cause infections

4. Transport and Transmission of microbes Abiotic routes, vehicles and fomites (indirect contact) –Water –Wind/thermal currents –Food –Other Biotic routes –Host to host (Direct contact) Human to human Animal reservoir to human –Vector Biological (blood or feces of vector) Mechanical (vector transports on body) Combination of biotic and abiotic

5. Microbes in Water

7. Contamination of Water affects drinking and recreational water

8. Food Borne Illnesses Fecal contamination of food –From animals (E. coli, Salmonella etc…) –From humans (hepatitis A etc…) Parasites in tissue of meat (helminthes etc…) Food spoilage or intoxication (Botulism, aflatoxins etc..)

9. Direct Contact Transmission Types of contact: Bites, scratches, sneezes, coughs, sexual contact, physical contact, exposure to blood or body fluids Direct contact with: –With humans-examples include VDs (STDs), MRSA –With animals – examples include rabies, ringworm –With vehicles (blood, feces, body fluids etc…) brucellosis, Q fever, Tularemia

10. Vector Transmission Vectors are usually arthropods Biological transmission by haematophagous vectors (blood feeding vectors) Through saliva of vector ‘dirty needle’ transmission by vector’s proboscis (rarely occurs) Through blood or feces of vector Accidental ingestion of vector Mechanical vectors (non blood feeding) On body of vector In feces of vector Accidental ingestions

11. Insects Siphonaptera-fleas Diptera-flies Nematocera Ceratopogonidae-no-see-ums, sand gnats Culicidae-mosquitoes Psychodidae-sand flies Simuliidae-blackflies Brachycera Tabanidae-horse and deer flies Cyclorrhapha Muscidae-houseflies Glossinidae-tetse flies Hemiptera-bugs Reduviidae-conenose (kissing) bugs Cimicidae-bed bugs Dictyoptera Blattidae-roaches Anoplura-sucking lice

12. Some Insect Vectors Flea Mosquito Tsetse fly Cone nose bug

13. Mites (including ticks) Arachnida Acari Ixodidae-hard ticks Argasidae-soft ticks Laelapidae-hematophagous mites Dermanyssidae-hematophagous mites Demodicidae-follicle mites Trombiculidae-chiggers Sarcoptidae-scabies mites Ticks

14. Lone star tick American dog tick Black legged tick (deer tick) Ticks are important vectors Some species also cause tick paralysis

15. Examples of vector-borne diseases Mosquitoes- malaria, hemorrhagic fevers, viral encephalitis, filariasis Black flies- river blindness Sand flies- leishmaniasis, Oroya fever Fleas-plague, maybe bartonellosis, some tapeworms Lice- trench fever, epidemic typhus, relapsing fever Deer flies- loaiasis Conenose (kissing) bugs- Chaga’s disease Tsetse flies- African sleeping sickness Ticks- Lyme disease, ehrlichiosis, RMSF, hemorrhagic fevers Chiggers- scrub typhus Copepods and other crustaceans- cholera, dracunculiasis

16. Reservoirs Reservoirs maintain the disease agent in nature Animals Vertebrates- deer, rodents, monkeys etc.. Invertebrates- clams, crustaceans, insects (remember, sometimes a vector can also be a reservoir) Protists- some amoebas Water or soil- some free-living, infectious organisms can reproduce outside of the host in water or soil (otherwise water and soil are just vehicles)

17. Natural factors that affect distribution and abundance of disease- causing organisms Environmental changes Individual host, vector or reservoir Population of hosts, vectors or reservoirs Microbial antagonism, competitive exclusion Genetic changes in disease agent Natural selection Stochastic effects (e.g. drift, bottlenecks etc…) Host health and immunity (e.g. stress)

18. Environment and Disease Abiotic factors (Weather) E Ecosystem balance Host availability and abundance (including vectors and reservoirs)

19. Anthropogenic and societal factors that influence disease Environmental degradation Overcrowding PollutionPoverty Education Hygiene

20. Studying Temporal Variation The distribution and abundance of microorganisms may vary with time Outbreaks of disease may occur periodically in relation to changes in the environment, changes in hosts, genetic change in the microbe itself, or a combination of factors For example, each year, outbreaks of influenza result in about 30,000 deaths. However, the severity may differ over time as different strains emerge

21. Hospitals and the spread of disease Nosocomial infections occur in hospitals Hospitals may contain more immunocompromised people, who are more susceptible Invasive procedures are conducted, creating portals of entry for pathogens Many opportunistic pathogens Frequent use of antibiotics and the potential spread of antibiotic resistance genes Misdiagnosis of disease especially emerging or obscure pathogens

22. Pathogens frequently causing nosocomial infections Staphylococcus aureus and MRSA Streptococcus spp. Pseudomonas aeruginosa Enterococcus spp. Escherichia coli Klebsiella spp. Enterobacter spp. Clostridium difficile Candida albicans Many others

23. Epidemiology and Infection Terminology Acute- short-term infection with dramatic onset and rapid recovery (or death) Chronic- long-term infection Definitive host- host in which a parasite reaches sexual maturity Endemic-naturally occurring in a particular area Enzootic-presence of pathogen in particular area maintained by local reservoirs and vectors Epidemic-presence of disease agent above normal infection prevalence Epizootic-out break of enzootic pathogen Etiology- cause of disease Fomite-inanimate objects that can transmit pathogens between hosts Incidence-the number of new host who become infected Infectious dose- number of agents required to cause disease Intensity- the number of parasites in a single host Intermediate host- host in which parasite develops to some extent but not to sexual maturity Microbial antagonism- competition between microbes which can lead to suppression of a particular type of disease agent

24. Opportunistic Pathogen/parasite (phoront or commensal becomes parasitic) Obligate Parasite (cannot live without host) Pathogen- organism that causes disease Pathogenicity- organisms ability to cause disease Prevalence-the rate or frequency of an organism as a proportion or percent Reservoir-host that maintains disease agent in nature Resident- symbiont that remains in a host for a significant period of time Sylvatic-exist normally in the wild, not in the human population Transient- symbiont that is in a host temporarily Transovarial transmission-vertical transmission-vector to offspring Transstadial transmission-transmission of agent across life stages of vector Vector- Organism that carries an agent from one host to another Vehicle- inanimate source of pathogens Virulence-degree of pathogenicity of an organism Zoonosis-disease of animals that can be transmitted to humans Suffixes -emia –presence of, -osis, -iasis, -itis - referring to disease state or condition of infection