Arboviruses

• Arbovirus


  Arthropod-borne viruses
• Arboviruses


  • Maintained in nature through biological transmission between susceptible vertebrate hosts by blood-feeding arthropods
  • Vertebrate infection occurs when the infected arthropod takes a blood meal
• Arbovirus families


  • TOGAVIRIDAE
  • FLAVIVIRIDAE
  • BUNYAVIRIDAE
  • REOVIRIDAE
• Arthropod vectors of arboviruses

  • Mosquitoes
  • Ticks
  • Sandflies
• Diseases caused by arboviruses

  • Fever and rash
  • Encephalitis
  • Haemorrhagic fever
• Eastern equine encephalitis (EEE)

  • Togavirus, Alphavirus genus
  • Reservoir is birds
  • Transmitted by mosquitos
  • Horse is a dead end host
  • Children more likely to have severe clinical symptoms than adults
• Transmission cycle of EEE

  1. Reservoir host: Birds

  2. Vector: Mosquitoes

  3. Incidental hosts: Humans, Horses
• Symptoms of EEE


  • Febrile illness (fever, chills, body aches, joint pain)
  • Neurologic disease (fever, headache, vomiting, diarrhea, seizures, behavioral changes, drowsiness, coma)
• Approximately a third of all people with encephalitis due to EEE die
• Many people who recover from EEE are left with long-term physical or mental impairments
• Diagnosis of EEE


  Based on clinical symptoms and laboratory testing of blood or spinal fluid
• Treatment of EEE


  • No vaccine or specific antiviral treatments available
  • Over-the-counter pain relievers can be used
  • Severe cases require supportive treatment like intravenous fluids, pain medication, and nursing care
• Flaviviridae


  Family of positive, single-stranded, enveloped RNA viruses found in arthropods (primarily ticks and mosquitoes) that can infect humans
• Dengue fever virus (DFV)


  • There are four different serotypes: DEN 1, DEN2, DEN3 and DEN4
  • Main hosts are non-human primates
  • 2.5 billion individuals at risk of infection, 40-80 million infected each year with thousands of deaths
• Clinical manifestations of dengue

  • Dengue fever: Febrile illness with headache, bone/muscle/joint pain, rash, leucopenia
  • Dengue hemorrhagic fever: High fever, hemorrhagic phenomena, circulatory failure, may develop dengue shock syndrome
• Transmission of DFV


  1. Human-to-human transmission through Aedes mosquitoes

  2. Infected mosquitoes can transmit vertically (to offspring)

  3. Sylvatic/enzootic transmission between primates and mosquitoes

  4. Epidemic transmission to humans
• Treatment of dengue


  Replacement of plasma expander and electrolytes for DHF/DSS
• Yellow fever virus


  • Acute viral hemorrhagic disease
  • Up to 50% of severely affected persons without treatment will die
• An estimated 200,000 cases of yellow fever, causing 30,000 deaths, worldwide each year
• Endemic zones for yellow fever

  • Tropical areas of Africa and Latin America, with a combined population of over 900 million people
• Clinical diagnosis of yellow fever

  Incubation period of 3-6 days, followed by an "acute phase" with fever, muscle pain, headache, etc. and a "toxic phase" with high fever, jaundice, abdominal pain, vomiting, and hemorrhage (15% of patients)
• Transmission of yellow fever virus

  1. Sylvatic (jungle) yellow fever: Monkeys, mosquitoes, and humans

  2. Intermediate yellow fever: Semi-domestic mosquitoes infect monkeys and humans

  3. Urban yellow fever: Infected people introduce virus to areas with Aedes mosquitoes and non-immune people
• Treatment of yellow fever

  No cure, only symptomatic treatment to reduce patient discomfort
• Prevention of yellow fever

  • Vaccination: Safe, affordable, provides effective immunity within 1 week for 95% of those vaccinated
  • Mosquito control: Eliminate breeding sites, use mosquito nets
• Bunyaviridae


  Family includes Crimea Congo hemorrhagic fever virus, Rift Valley Fever virus, and Hantaviruses
• Rift Valley Fever


  • Viral zoonosis that primarily affects animals but can also infect humans
  • Mild form in humans has sudden onset of flu-like fever, muscle/joint pain, headache
  • Severe form can cause ocular disease, meningoencephalitis, or hemorrhagic fever