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Zoonotic Diseases

Zoonotic Diseases. Zoonotic diseases:. Synanthropic : urban or domestic animal life cycle Leptospirosis Toxoplasmosis Plague Exoanthropic : feral or wild animal cycle Rabies Plague Tularemia. Zoonotic diseases:.

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Zoonotic Diseases

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  1. Zoonotic Diseases

  2. Zoonotic diseases: • Synanthropic: urban or domestic animal life cycle • Leptospirosis • Toxoplasmosis • Plague • Exoanthropic: feral or wild animal cycle • Rabies • Plague • Tularemia

  3. Zoonotic diseases: • Infectious diseases naturally transmitted from non-human animals to humans • >250 etiologic agents are known to cause zoonotic infections • 40+ involve companion animals

  4. Vector transmitted diseases • Mechanical vectors • Biological vectors • Arboviruses

  5. Vector transmitted diseases • Changes in geographic distribution • Introduction or natural migration of vectors • Altered distribution of natural hosts • Aberrant feeding patterns of vector, i.e. due to habitat disruption or destruction • Introduction of etiologic agent to region with endemic competent vectors • Complex life cycles may involve one or more animal reservoirs • Confluence of reservoirs, vectors, etiologic agents, and hosts may be sporadic, stable, or evolving

  6. biological vector  an arthropod vector in whose body the infecting organism develops or multiplies before becoming infective to the recipient individual. • mechanical vector  an arthropod vector which transmits an infective organism from one host to another but which is not essential to the life cycle of the parasite.

  7. Sapronoses = environmentally acquired infections • Infections affecting humans and other animals in which the agent is maintained in nature (replication in soil, water, feces, decaying vegetation or flesh) • Humans and animals acquire infection independently • Companion animals can serve as sentinels

  8. Sapronoses • Fungal infections: • Cryptococcosis, blastomycosis, histoplasmosis, coccidiodomycosis • Anthrax • Phythiosis

  9. Anthropozoonoses • Disease agent found primarily in humans, with animals acquiring infection via human-animal contact or contact with fomites contaminated by infected humans: • Mycobacterium tuberculosis: elephants; non-human primates; rarely dogs • Methicillin-resistant Staphylococcus aureus • Entamoebahistolytica: non-human primates • Herpes viruses (non-human primates)

  10. Routes of transmission • Bite or saliva: rabies, tularemia • Aerosol: plague, Q fever • Fecal-oral: toxoplasmosis, salmonellosis • Urine: leptospirosis • Vector borne-diseases: tularemia, plague, Rocky Mountain spotted fever, equine encephalitis viruses (EEE, WEE, VEE) • Consumption of infected meat: toxoplasmosis, trichinellosis,

  11. Rabies

  12. Rabies • Rabdovirus family (Rabdoviridae) • Receptors used for binding, entry, trafficking in neurons are highly conserved • Reservoir in many countries = feral dogs • Reservoir in US: depends on region • Bat • Skunk • Raccoon

  13. Rabies: terrestrial reservoirs in the U.S.

  14. Rabies virus: entry & exit strategies?

  15. Tularemia • Francisellatularensis • Gram negative, non-spore-forming, non-saprophytic coccobacillus/small bacillus • Disease in humans: • Normal life cycle (complex, diverse) • Type A: primarily tick-rabbit • Type B: complex (ticks, rodents, mosquitos, mud, beavers…) • Intracellular pathogen • Very sensitive to dessication, but can survive for weeks in infected carcass if not desiccated • Reportable disease: immediate • classified as catergory A select agent due to potential use as bioterrorism agent

  16. Q fever: Coxiellaburnettii • Primary reservoir = goats & sheep • Subclinical infection is common • Organism is shed in urine, milk, feces • Causes abortion, high # of organisms in placenta & amniotic fluid • Disease in people usually = fever, headache, myalgia, +/- vomiting, diarrhea • More severe cases: pneumonia, myocarditis, hepatitis, meningitis, encephalitis • Can cause pre-term delivery or miscarriage in pregnant women • Chronic disease: endocarditis, orchitis, osteomyelitis

  17. Coxiellaburnetti • Small Gram-negative rod • Intracellular pathogen: survives in the phagolysozome • Extremely hardy organism – survives for long periods in environment, resistant to desiccation, many detergents

  18. Plaque: Yersinia pestis • Prokaryote = Gram negative rod; Enterobacteriaceae family, facultative anaerobe • Vector = flea; or direct transmission • Endemic in rodent populations

  19. Yersinia pestis: Black Death

  20. Toxoplasmagondii Domain: Eukarya Kingdom: Protista Apicomplexan Etiologic agent of toxoplasmosis

  21. Life cycle of Toxoplasmagondii Int. hosts Definitive host

  22. Arboviral encephalitis • Eastern equine encephalitis • Western EE • West Nile Virus

  23. Arboviral encephalitis: natural history

  24. Anthropozoonosis • Methicillin-resistant Staphylococcus aureus • Primary human pathogen • Infections identified in dogs, cats, horses • Risk factor: exposure to infected humans or human medical health workers • Canine & feline staph isolates: • Staphylococcus pseudintermedius • Staphylococcus schleiferi

  25. Anthropozoonosis • Mycobacterium tuberculosis • Acid fast bacterial rod • Live in macrophages • Primary human pathogen: reservoir = people • Elephants and non-human primates esp. susceptible • Rare cases in dogs living with infected person • Risk factor: exposure to infected humans • Treatment: financial & ethical dilemmas

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