Vector-Borne Viral Infections Flashcards
3 most common vectors for ARBO viruses
Mosquitoes, ticks, and sandflies
Where do ARBO viruses replicate?
Virus replicates in reticuloendothelial system and vascular endothelium, then secondary viremia seeds target organs.
US viruses transmitted by mosquitoes (5)
- Eastern / Western Equine Encephalitis Virus
- St. Louis Encephalitis Virus
- California Group Encephalitis Viruses
- LaCrosse Encephalitis Virus in Wisconsin (endogenous in Mississippi river valley)
- West Nile virus is endemic throughout the US
Which virus is transmitted by ticks?
Clinical signs
Heartland virus
Causes high fever, leukopenia, and thrombocytopenia
Traveler diseases caused by mosquitoes (5)
- Dengue Fever/Hemorrhagic Fever – endemic in the Caribbean, Latin America, and Key West Florida
- Venezuelan Equine Encephalitis virus
- Yellow Fever – hemorrhagic fever. Endemic in parts of Brazil and Central America.
- Chikungunya virus – Arthritis, now endemic in Caribbean region
- Zika virus
3 main syndromes caused by ARBO viruses
- Encephalitis – predominant syndrome seen in US. Confusion, lethargy, poor balance (including difficulty sitting upright), speech problems, fever. May enter coma.
- Hemorrhagic fever
- Arthritis / arthralgia (Chickungunya)
2 main animal-borne viruses in North America
Rabies and Hanta virus (Sin Nombre virus)
Rabies
Transmission
Sxs
Bats, skunks, raccoons, and foxes.
Most often via bites, but can occur w/ inhalation of dried urine.
Encephalitis, salivation, difficulty swallowing
Hanta / Sin Nombre Virus
Transmission
Sxs
Death rate for pulmonary
- Inhaled in dried rodent (mouse) urine / feces.
- Target organ is lungs → pulmonary edema (Hantavirus Pulmonary Syndrome). Little inflammation, necrosis, or cytopathic effect.
- Also causes kidney failure (uremia) and fever.
- 75% death rate for HPS
3 travel-related animal-borne viruses
- Junin virus – Hemorrhagic fever virus from South America. Rodents are natural host.
- Lassa Fever – Hemorrhagic fever virus in Africa. Rodents are natural host.
- Ebola virus – Hemorrhagic fever, bats are possibly host.
Ebola virus Transmission Incubation periods Sxs 2 diff strains
- Transmission occurs via direct contact w/ fluids
- 21 day incubation period
- Fever, headache, myalgia → pharyngitis, vomiting, diarrhea, maculopapular rash (flat, red) → bleeding / multi-organ failure → death w/in 7-10 days.
- Zaire strain (Africa) up to 80% mortality
- Reston strain (Phillipines). Very little / no mortality. Usually subclinical.
Urban transmission pattern
3 virus examples
- Human –> mosquito –> human, etc
- Requires high titer, prolonged viremia in vertebrate host (long enough for mosquito to pick it up). Humans are reservoir species.
- Ex: yellow fever, dengue, St. Louis encephalitis.
Examples of sylvan (forest) cycle
WEE, VEE, La Crosse, West Nile, Yellow fever (has both urban and sylvan cycles)
3 viruses passed via animal urine / feces / butchering
Hantavirus, Lassa fever, Ebola
Pathogenesis of West Nile Encephalitis
Virus replicates locally in endothelial cells. Secondary viremia occurs, resulting in seeding of the CNS, where the virus replicates in neurons and meninges. Symptoms are caused by both cell death and the host inflammatory response. Almost all deaths occurs in those older than 50 y/o.
