arboviral dz Flashcards
What are arboviruses
Viruses maintained in nature in cycles involving hematophagous arthropod vectors and susceptible vertebrate hosts
arbovirus vectors and hosts
vectors: Primarily mosquitoes, but also ticks, biting flies. Hosts: 1.Those that serve as main sources of infections for vectors (reservoirs): may or may not develop disease 2.Those that do not serve as reservoirs, but in which overt disease may occur. Humans are dead end hosts for most arboviruses
Which arboviruses can maintain the transmission of viruses via human-vector transmission
dengue virus, urban yellow fever virus, Ross river virus, Chikungunya virus
arbovirus clinical outcomes
asymptomatic (90% of dengue virus/ WNV, 15% of chikungunya virus). Fever, chills, muclse pain. Neuro dz: encephalitis, meningitis, AFP. Arthritis: Fever, intense pain in peripheral joints, inflammation in joints, tendons, skeletal muscle, Development of chronic disease is common. Hemorrhagic fever: Damage to the vascular system, loss of platelet function. Signs of bleeding under skin, internal organs, mouth, eyes. Shock, seizures, and mortality
list the three most important arboviruses
Bunyaviridae, flaviviruses, togaviridae (alphaviruses)
structure of Bunyaviridae, flaviviruses, alphaviruses
Bunyavirus: segmented, Negative sense RNA. Flaviviruses: Single-stranded, Positive sense RNA. Alphaviruses: Single-stranded, Positive sense RNA
List the Flaviviruses
Dengue viruses, Yellow fever virus, Japanese
Encephalitis virus, West Nile virus, St. Louis Encephalitis virusDengue viruses, Yellow fever virus, Japanese
Encephalitis virus, West Nile virus, St. Louis Encephalitis virusDengue viruses, Yellow fever virus, Japanese
Encephalitis virus, West Nile virus, St. Louis Encephalitis virus
major global arboviruses
Yellow Fever virus (YFV), Dengue viruses (DENV), Japanese encephalitis virus (JEV), West Nile virus (WNV), Chikungunya virus (CHIKV)
major arboviruses in US
West Nile virus (WNV) St. Louis encephalitis virus (SLEV) La Crosse virus Eastern equine encephalitis virus Colorado Tick Fever virusWest Nile virus (WNV) St. Louis encephalitis virus (SLEV) La Crosse virus Eastern equine encephalitis virus Colorado Tick Fever virusWest Nile virus (WNV) St. Louis encephalitis virus (SLEV) La Crosse virus Eastern equine encephalitis virus Colorado Tick Fever virus
Yellow fever clinical
Nonspecific syndrome (fever, headache, nausea, vomiting) followed by Remission (1-2 days). 15% of cases progress: Jaundice, Hemorrhagic manifestations, shock, multisystem organ failure. 20-50% of cases with jaundice are fatal
yellow fever treatment/ prevention
supportive only. Live attenutaed vaccine- Not recommended for very young (< 9 mos.), elderly (> 60 yo), immunocompromised. Assoc. with rare, but serious, adverse events
Where is Yellow fever most common
South America and central africa
yellow fever virus transmission
transmitted from monkeys to mosquitos (Aedes aegypti) then to humans and back to mosquitos and back to humans
Dengue virus associated diseases
- Dengue Fever (DF- 25%):An acute febrile illness characterized by headache, muscle and joint pain, and rash. 2. Dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS- 75%): Characterized by thrombocytopenia, capillary leakage, damage to liver. Fluid loss in tissue spaces can lead to hypovolemic shock and death (DSS)
Dengue severity classifications
Dengue without warning signs (dengue fever) > dengue with warning signs > severe dengue. Warning signs include abd pain, persistent vomiting, fluid accumulation. Mucosal bleeding, lethargy, liver enlargement, increased HCT with decreased platelets. Severe dengue: severe plasma leakage, severe hemorrhage or severe organ impairment
Where is Dengue virus most common
central America, northern part of South America, Asia, parts of Africa. High temp and precipitation
Factors contributing to dengue re-emergence
population growth, air travel, urbanization (crowding, poor waste management), lack of mosquito control
Dengue transmission
mosquito borne (Aedes aegypti, Aedes albopictus). Maintained in human-mosquito-human transmission cycle
Risk factors for dengue fever/ dengue hemorrhagic fever
A second dengue infection by a different serotype, Age (under age 15), Host genetic background, Viral genotype, Each of the 4 DENV serotypes is composed of several genotypes
pathogenesis of increased dengue fever risk with second infection
With first infection, Antibody response protects from re-infection with homologous DENV serotype (neutralizing antibodies) and due to cross reaction, initially protects from second infection with a different DENV serotype. Over time these cross reactive Abs decline to subneutralizing levels. Following 2nd infection with different serotype Cross-reactive subneutralizing antibodies generated during the first infection mediate enhanced infection of specific cells via FcγRs. Leads to increased viral replication and immune activation (increased cytokines etc.)
Who gets dengue hemorrhagic fever
- Children and adults with a second infection by a different serotype. 2. Infants with primary DENV infection born to dengue-immune mothers. DENV is rare in infants < 3 months. Occurs primarily 4-12 month infants.
Challenges with Dengue vaccine development
Antibodies play both protective and pathologic roles. Need to provide balanced and lasting responses to all 4 serotypes. Must be tetravalent. Waning of protection over time may put people at risk for severe disease
Why is Dengue so rare in USA today?
air conditioning, increased income, piped water, window screens
List the alpha viruses
Chikungunya virus
Chikungunya virus clinical
fever, symmetrical joint pain, muscle pain, rash, difficulty ambulating. fingers, wrists, elbows, toes, ankles, and knees most commonly affected. symptoms are incapacitating. symptoms may persist for months to years, sometimes fluctuating. Clinically mimics seronegative RA, unless initial fever, rash, and travel history are revealed
Chikungunya virus treatment/ prevention
No vaccines or therapies. Vaccines are in development (live attenuated vaccine)
chikungunya virus locations
US, Africa, Asia
List reoviruses
Colorado Tick Fever
colorado Tick fever vector and reservoir
tick vector. Reservoir included squirrels, chipmunks, porcupines
West nile virus vectors/ hosts
Birds are hosts, mosquitos are vectors. Humans, horses and vertebrates are dead end hosts
West Nile locations
Every continent except Antarctica
West nile virus clinical
80% are asymptomatic. 20% have fever, headache, fatigue. 1% have neuroinvasive dz: Fever, headache, altered mental status, neck stiffness. Typically manifests as encephalitis (63%), meningitis (33%), or acute flaccid paralysis (3%). Most cases occur in elderly people and those with impaired immune systems. Long term neurological sequelae are commo
West nile virus pathogenesis
Replicates in keratinocytes and dendritic cells at site of inoculation > infected cells migrate and spread virus to lymph nodes > primary viremia > virus gains access to CNS (cytokines/ proteases increase endothelial cell permeability) > MNV directly infects neurons > neuronal injury in brain stem, hippocampus, cortex, cerebellum spinal cord
West Nile virus treatment/ prevention
supportive therapy. No vaccine currently
Alternative modes of transmission of WNV
solid organ transplant, blood transfusion
which arboviruses have vaccines
yellow fever (live attenuated), japanese encephalitis virus (inactivated vaccine, chimeric live attenuated, and live attenuated),
