Arboviruses Flashcards
From the name, what are arboviruses?
arthropod-borne viruses
In virology, what is a dead-end host?
In virology, a dead-end host (also known as an incidental or accidental host) is an organism that becomes infected with a virus but does not contribute to the transmission of the virus to other susceptible hosts. This means that the virus cannot complete its life cycle or spread further from the dead-end host.
The virus does not reach sufficient levels in the blood to be transmitted to other hosts.
List four families of arboviruses.
Togaviridae, Flaviviridae, Bunyaviridae, Reoviridae
Eastern Equine Encephalitis Virus
(a) Family
(b) Genus
(c) Reservoir host
(d) Vector
(e) Dead end host
(a) Family: Togavirus
(b) Genus: Alphavirus
(c) Reservoir host: birds
(d) Vector: mosquitoes
(e) Dead end host: horses, humans
[Diagram]
Briefly discuss the structure and genome of EEEV.
➤ EEEV is an enveloped virus with an icosahedral capsid. The envelope contains glycoproteins E1 and E2, which form spikes on the virus surface. These spikes are crucial for the virus’s ability to infect host cells.
➤ EEEV has a positive-sense single stranded RNA genome.
[Diagram 1] [Diagram 2] [Diagram 3]
symptoms of EEEV infection
In humans, symptoms can include high fever, headache, vomiting, diarrhea, seizures, and behavioral changes. Severe cases can lead to encephalitis (inflammation of the brain), which can cause long-term neurological problems or even be fatal.
Further notes:
➤ The illness lasts 1 to 2 weeks, and most people recover completely when there is no central nervous system involvement.
➤ Approximately 1/3 of all people with encephalitis due to EEE die. Death usually occurs 2 to 10 days after onset of symptoms but can occur much later.
➤ Many people who recover are left with long-term physical or mental impairments, which can range from mild brain dysfunction to severe intellectual impairment, personality disorders, seizures, paralysis, and cranial nerve dysfunction.
➤ People with severe impairments often require long-term care and die within a few years.
Briefly discuss diagnosis of EEEV infection.
Diagnosis is based on the patient’s clinical symptoms and laboratory diagnosis by testing blood or spinal fluids, which will show if the virus or antibodies against the virus are present in the person.
Briefly discuss treatment of EEEV infection.
➤ No vaccine or specific antiviral treatmens for EEE are available.
➤ Over-the-counter pain relievers can be used to reduce fever and relieve some symptoms.
➤ In severe cases, patients often need to be hospitalized to receive supportive treatment, such as IV fluids, pain medication and nursing care.
Family Flaviviridae
(a) structure
(b) genome
(c) vectors
(d) genera
(a) structure: These viruses have an icosahedral geometry and are enveloped.
(b) genome: single-stranded positive-sense RNA
(c) vectors: arthropods - primarily ticks and mosquitoes
(d) genera:
➤ Flavivirus: Includes viruses like dengue, Zika, and West Nile virus, Yellow Fever virus
➤ Hepacivirus: includes the hepatitis C virus
➤ Pestivirus: Includes viruses that infect livestock, such as bovine viral diarrhea virus.
Dengue Fever Virus
(a) Family
(b) Serotypes
(c) Main hosts
(d) Clinical manifestations
(a) Family: Flaviviridae
(b) Serotypes: DEN1, DEN2, DEN3, DEN4
(c) Main hosts: non-human primates
(d) Clinical manifestations
febrille illness associated with headache, bone, muscle and joint pain, rash and leucopenia. In severe cases, symptoms manifest as dengue hemorrhagic fever (DHF): severe abdominal pain, persistent vomiting, bleeding from gums or nose, petechiae (bleeding under the skin), blood in urine, stools or vomit… [Diagram 1] [Image 1]
Further notes:
A febrile illness refers to any medical condition that causes a rise in body temperature above the normal range.
Leukopenia (also spelled leucopenia) is a condition characterized by a lower-than-normal number of white blood cells (WBCs) in the blood.
Discuss the transmission of dengue fever virus.
Dengue virus is primarily spread through the bites of infected Aedes mosquitoes, particularly Aedes aegypti and Aedes albopictus.
[Image]
In relation to dengue fever virus, explain the following statement: “Infected mosquitoes can also transmit the virus via the trans-ovarian mode.”
Trans-ovarian transmission refers to the process where an infected female mosquito passes the dengue virus to her offspring through her eggs. This means that the virus can be transmitted from one generation of mosquitoes to the next without the need for the offspring to bite an infected person.
causes of bleeding in dengue haemorrhagic syndrome
(a) thrombocytopenia: This is a condition where the platelet count drops significantly.
(b) increased vascular permeability: The dengue virus can cause the blood vessels to become more permeable.
(c) coagulopathy: This refers to a condition where the blood’s ability to clot is impaired, leading to prolonged excessive bleeding.
Dengue Fever Virus
Explain Antibody Dependent Enhancement.
This is a phenomenon whereby non-neutralizing antibodies from a previous infection can bind to a different serotype of dengue virus during a subsequent infection. Instead of neutralizing the virus, these antibodies facilitate its entry into host cells, potentially leading to more severe disease.
[Diagram 1] [Diagram 2]
