Summary
Mosquito-borne diseases are a group of viral infections transmitted by the bite of an infected mosquito, typically from the Culex, Anopheles, or Aedes species. Vertical and human-to-human transmission (e.g., via blood transfusions, organ, and tissue transplants) are also possible. These viral diseases belong to three main families: Togaviridae (Chikungunya virus, Eastern equine encephalitis (EEEV), Western equine encephalitis (WEEV), Flaviviridae (West Nile virus, Dengue virus, Zika virus, Yellow fever virus, Japanese encephalitis virus), and Bunyaviridae (Rift Valley fever virus, La Crosse encephalitis virus). Clinical features of these diseases vary but often include an initial systemic febrile illness (i.e., fever, headache, myalgias, gastrointestinal symptoms) that progresses to a neuroinvasive disease (e.g., meningitis, encephalitis). Diagnosis is made via antibody detection (e.g., IgM, IgG), ELISA, FIA, or PCR. Treatment is typically supportive. Prevention primarily consists of mosquito control measures (i.e., adequate clothing, insect repellents, mosquito nets, minimizing mosquito breeding).
Mosquito-borne Togavirus diseases
Overview
Overview of mosquito-borne Togavirus diseases | ||||||
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Chikungunya fever | Eastern equine encephalitis (EEE) | Western equine encephalitis (WEE) | Venezuelan equine encephalitis (VEE) | Ross River fever (RRF) | ||
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Chikungunya fever [1][2]
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Epidemiology
- Mainly occurs in the tropical and subtropical regions
- Outbreaks occur sporadically
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Etiology
- Pathogen: Chikungunya virus (belongs to the alphavirus genus of the family Togaviridae)
- Vectors: mosquitoes (Aedes aegypti and Aedes albopictus), possibly leading to coinfection with dengue
- Reservoirs: nonhuman or human primates
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Transmission route: Clinical features
- Incubation period: usually 3–7 days
- Fever, malaise
- Headache
- Lymphadenopathy
- Severe bilateral polyarthralgia
- Periarticular edema
- Maculopapular rash
- Diagnostics
- Differential diagnosis
- Treatment: supportive
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Complication: chronic arthritis
- Most common and severe complication
- May last for months to years and lead to long-term disability
- Prognosis: Most individuals fully recover within a week.
Eastern equine encephalitis (EEE)
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Epidemiology
- Found primarily in the Americas
- In the US, occurs east of the Mississippi River (e.g., New York, New Jersey, Michigan)
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Bimodal distribution
- ≤ 5 years of age
- ≥ 60 years of age
- Outbreaks occur from late spring to early fall.
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Etiology
- Pathogen: Eastern equine encephalitis virus (EEEV)
- Vectors: mosquitoes (Culiseta melanura, Aedes, Coquillettidia, and Culex spp.)
- Reservoirs: horses, birds
- Route of transmission
- Mosquito bite
- Human-to-human: organ transplantation
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Clinical features
- Incubation period: 4–10 days [3]
- Systemic febrile illness (acute EEE)
- EEE
- A life-threatening inflammation of the CNS
- Occurs in ∼ 5% of patients [3]
- Seen shortly after the systemic febrile illness
- Neurological symptoms include seizures, confusion, focal disabilities (cranial nerve palsies), and coma.
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Diagnostics
- Laboratory studies: ↑ WBCs
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Serology (gold standard)
- IgM and/or rising levels of IgG antibodies detected using ELISA, IFA, or hemagglutination assays
- Confirmation: ≥ 4-fold antibody titer increase in serum samples collected after the first week of symptoms
- Reverse transcriptase PCR
- PRNT
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CSF analysis
- ↑ Neutrophils and proteins
- Normal or decreased glucose
- Analyzed using ELISA test for EEV-specific antibodies
- Brain MRI
- Viral culture
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Differential diagnosis
- Aseptic meningitis
- Viral encephalitis (e.g., measles, echovirus)
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Treatment: mainly supportive
- Analgesics for pain and fever
- Management of fluids and electrolyte balance
- Maintenance of blood pressure and oxygenation
- Anticonvulsive treatment of seizures
- Complications
Western equine encephalitis (WEE)
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Epidemiology
- Occurs on the west coast of the United States and Canada
- Outbreaks during summer
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Etiology
- Pathogen: Western equine encephalitis virus (WEEV)
- Vectors: mosquitoes (Culex tarsalis, Aedes spp.)
- Reservoirs: horses, mules, birds
- Route of transmission
- Mosquito bite
- Human-to-human
- Blood transfusions from an infected host
- Transplacental
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Clinical features
- Incubation period: 2–7 days [5]
- Most affected individuals are asymptomatic.
- Systemic febrile illness (acute WEE)
- WEE
- Adults have more mild symptoms than children and elderly individuals.
- Severe forms of encephalitis are more common in children.
- Neurological symptoms include seizures, confusion, somnolence, spasticity, cognitive impairment, and coma.
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Diagnostics
- Laboratory studies: ↑ WBCs
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Serology
- IgM and/or rising levels of IgG antibodies detected using ELISA, IFA, or hemagglutination assays
- Confirmation: ≥ 4-fold antibody titer increase in serum samples collected after the first week of symptoms
- Reverse transcriptase PCR
- PRNT
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CSF analysis
- ↑ Opening pressure, lymphocytes, and proteins
- Normal glucose
- Analyzed using ELISA test for WEEV-specific antibodies
- Brain MRI
- Viral culture
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Differential diagnosis
- Murray Valley encephalitis
- West Nile virus encephalitis
- Japanese encephalitis
- HSV encephalitis
- EEE
- VEE
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Treatment: mainly supportive
- Analgesics for pain and fever
- Management of fluids and electrolyte balance
- Maintenance of blood pressure and oxygenation
- Anticonvulsive treatment of seizures
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Complications
- Neurological sequelae
- Epilepsy
- Spasticity
- Behavioral changes
- Death
Venezuelan equine encephalitis (VEE)
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Epidemiology
- Found predominantly in the Americas (Colombia, Venezuela, Panama, Guatemala, Mexico, the United States, Ecuador, Nicaragua, Costa Rica, Peru)
- Sporadic outbreaks
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Etiology
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Pathogen
- Venezuelan equine encephalitis virus (VEEV)
- Subtypes IAB and IC are responsible for VEE in humans.
- Vectors: mosquitoes (Ochlerotatus taeniorhynchus, Ae. sollicitans, and Ae. taeniorhynchus transmit epizootic strains )
- Reservoirs: horses, mules, donkeys, rodents
- Route of transmission
- Mosquito bite
- Inhalation of aerosols
- Human-to-human: vertical transmission
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Pathogen
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Clinical features
- Incubation period: 2–5 days [6]
- Systemic febrile illness (acute VEE)
- Lasts 3–4 days [6]
- Fever
- Headache
- Myalgias, arthralgias
- Sore throat
- Retroorbital pain
- Gastrointestinal symptoms (nausea, vomiting)
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Venezuelan equine encephalitis
- Manifests in ≤ 15% of patients [6]
- Severe forms of encephalitis are more common in children.
- Neurological symptoms include seizures, confusion, motor/cognitive impairment, and focal disabilities.
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Diagnostics
- Laboratory studies
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Serology (gold standard)
- IgM and/or rising levels of IgG antibodies detected using ELISA, IFA, or hemagglutination assays
- Confirmation: ≥ 4-fold antibody titer increase in serum samples collected
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Reverse transcriptase PCR
- Blood or pharyngeal sample
- Can be performed on the 8th day after symptom onset
- PRNT
- CSF analysis: ↑ lymphocytes, proteins, and glucose
- Analyzed using ELISA test for VEEV-specific antibodies
- EEG: diffuse slowing activity
- Viral culture
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Differential diagnosis
- Dengue fever
- Chikungunya
- EEE
- Zika
- HSV encephalitis
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Treatment: mainly supportive
- Analgesics for pain and fever
- Management of fluids and electrolyte balance
- Maintenance of blood pressure and oxygenation
- Anticonvulsive treatment of seizures
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Complications
- Neurological sequelae
- Cognitive disabilities
- Behavioral changes
- Pregnant women
- Death
- Neurological sequelae
Ross River fever (RRF)
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Epidemiology
- Found predominantly in Australia, Papua New Guinea, the Solomon Islands, and other parts of Southeast Asia
- Outbreaks during summer and early autumn
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Etiology
- Pathogen: Ross River virus (RRV)
- Vectors: mosquitoes (Aedes vigilax, Aedes camptorhynchus, Culex annulirostris, and Aedes aegypti)
- Reservoirs: wallabies, kangaroos, possums, horses
- Route of transmission
- Mosquito bite
- Human-mosquito-human transmission
- Human-to-human: blood transfusions from an infected host
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Clinical features
- Incubation period: 3–9 days [7]
- Febrile illness
- Usually self-limited
- Classic triad: fever, rash, and arthritis Can also manifest as chronic arthralgias or arthritis
- Fever of 39°C, may last up to 3 days [7]
- Rash is maculopapular, affecting the trunk, arms, palms, soles, and face.
- Arthritis is symmetrical, mainly involving the knees, ankles, wrists, and fingers.
- Generalized fatigue, myalgias, and lymphadenopathies are also common.
- Other clinical manifestations
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Diagnostics
- Laboratory studies: ↑ ESR
- Serology (gold standard): IgM and/or rising levels of IgG antibodies detected using ELISA
- PCR
- Viral culture
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Differential diagnosis
- Barmah Forest virus
- Chikungunya
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Treatment: mainly supportive
- Analgesics for pain and fever
- Management of fluids and electrolyte balance
- Maintenance of blood pressure and oxygenation
- Anticonvulsive treatment of seizures
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Complications
- Persistent symptoms (arthritis, fatigue) [8]
- Septic arthritis
Mosquito-borne Flavivirus diseases
Overview of mosquito-borne Flavivirus diseases | ||||
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West Nile virus | Murray Valley encephalitis (MVE) | St. Louis encephalitis | ||
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Lumbar puncture |
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Brain MRI |
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- See also “Yellow fever,” “Dengue,” “Zika virus infection,” and “Japanese encephalitis.”
Mosquito-borne Bunyavirus diseases
Overview of mosquito-borne Bunyavirus diseases | |||
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La Crosse encephalitis | Rift Valley fever | ||
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Prevention
Mosquito bite prevention
- Clothing
- Wear light-colored clothing.
- Long-sleeved shirts and long pants
- Insect repellent
- Use insect repellants (e.g., DEET, permethrin, oil of lemon eucalyptus)
- Apply to clothing and footwear.
- Mosquito nets
- Place screens at doors and windows.
- Use mosquito nets on baby strollers, carriers, and cribs.
- Remove open water containers, trash containers, and water-holding plants to minimize mosquito breeding.
Obligation to report
- Mosquito-borne diseases are nationally notifiable diseases in most countries worldwide (i.e., the physician is required by law to report cases of such diseases).