Arthro 2 bunyaviridae Flashcards
Bunyaviridae: Structural Characteristics
Viral dimensions are approximately 90-100 nm diameter. The viral particles have a helical nucleocapsid, which is surrounded by an envelop with glycoprotein spikes extending outward from it surface.
The genome consists of single stranded RNA which present in 3 segments (Large, Medium and Small). Like members of the Orthomyxoviridae (model for negative polarity RNA virus replication), Bunyaviruses have a negative polarity genome and therefore carries a viral RNA polymerase within the virus particle itself. Also like the Orthomyxovirus, influenza A virus, members of the Bunyavirus family can undergo reassortment of RNA segments as a result of mixed infections of cells by different strains of a particular Bunyavirus.
The replication of the Bunyavirus occurs in the cytoplasm and progeny virus particles acquire their envelops by budding through the membranes of the Golgi apparatus.
Bunyaviridae: Genus Bunyavirus
As in the case of the other Arboviruses, a subset of Bunyaviruses can multiply in arthropod vectors and can cause human disease upon being bitten by the infected mosquito.
Some Bunyaviruses are transmitted by mosquitoes and others by ticks.
There are 10 serogroups within the Bunyaviridae and one of these causes encephalitis in humans
Bunyaviridae: Genus Bunyavirus:
California serogroup: California encephalitis virus
California encephalitis virus is found mainly in the upper Mississippi and Ohio River valleys, where the mosquito vector is most prevalent. The peak incidence of the disease is July through September.
Bunyaviridae: Genus Bunyavirus:
California serogroup: Clinical disease:
The onset of the disease may take mild course or abrupt onset, which includes bifrontal headache, fever, vomiting, sometimes aseptic meningitis. Systemic and meningeal signs abate gradually within a week. 15% of infected children have sequelae.
LaCrosse encephalitis, a member of the California serogroup,
is seen in Nicolas County, WV
There are a number of viruses within the Bunyaviridae that are also capable of causing hemorrhagic fevers.
Bunyaviridae: Genus: Orthobunyavirus: Bunyamwera’ serogroup
Certain members of this genus cause only a febrile illness in humans, whereas others cause Crimean-Congo hemorrhagic fever.
Virus is transmitted by ticks, but the blood and secretions of animals and humans are also infectious
Bunyaviridae: Genus: Phlebovirus: Phlebotomus fever
Phlebotomus fever group are transmitted by sand flies
Clinical symptoms include headache, fever, myalgia, photophobia, stiffness of neck and back and papules over the body surface
Total recovery ensues with immunity for about 2 years
Bunyaviridae: Genus: Phlebovirus: Rift valley fever virus
Rift valley fever virus is transmitted by and can infect sheep and other domestic animals which can then be transmitted humans.
Clinical Symptoms: Saddleback fever, acute onset, GI distress, pain in joints and occasionally hemorrhagic fever
Recovery is usually complete. A vaccine has been developed
Bunyaviridae: Genus Hantavirus: Korean hemorrhagic fever virus
Acquired from urine and excrement of rodents and is hemorrhagic fever virus. The hemorrhagic fever was first seen in US military personnel in Korea with complications of a renal syndrome
Bunyaviridae: Genus Hantavirus: Hantavirus pulmonary syndrome
Hantavirus infections have also been seen in the American southwest particularly among native Americans. Exposure to virus
results from aerosols that originate from mouse feces contaminated dust. The infection often leads to a pulmonary syndrome (HPS)
Higher incidence of HPS is associated with more rainfall in southwest, which provides better habitat quality and increased numbers of rodents.
5% of HPS cases have been confirmed east of the Mississippi River. In July 2004 two cases of Hantavirus Pulmonary Syndrome reported in Randolph County, WV
Ribavirin has shown efficacy in treating HPS if given early in the course of the infection.
Terrorists could aerosolize this agent and disseminate it to produce HPS.
http://www.cdc.gov/ncidod/diseases/hanta/hps/index.htm
Arenaviridae: Structural
Structural characteristics of this virus include a rather wide range of sizes from 50-300 nm in diameter
Virus particles have a helical nucleocapsid which is surrounded by an envelop having a dense lipid bilayer. Within the core particles are seen by EM that resemble ribosomes.
The negative polarity genome of the virus is RNA consists of
multiple segments that appear to be circular
Arenaviruses replicate in cytoplasm using a viral RNA polymerase that is housed within the virus particles.
Arenaviridae: Genus: Arenavirus
Arenaviruses are divided into two serogroups: 1) The Old World Complex and 2) the New World Complex.
The primary old world viruses are Lymphocytic Choriomeningitis Virus (LCM) and Lassa virus
New world viruses include the Tacaribe virus complex including Junin and Machupo viruses
Virus hosts are restricted to rodents in which persistent infections leads to viremia and/or viruria
Arenaviridae: Genus: Arenavirus: Lymphocytic choriomeningitis virus
LCM infects man at frequency of 5%, except for those in close contact with rodents such as laboratory workers.
LCM outbreaks have been reported in humans who purchased hamsters
sold as pets. Urine and feces spread the virus. Also found in USA as a result of house mice infections which can transmit the virus to humans and rodent pets
The clinical disease is usually mild with influenza like
symptoms or infrequently aseptic meningitis.
Fatal disease was reported in organ transplant recipients who received organs from an LCMV infected donor. Three of 4 organs recipients died.
Infection of pregnant women during first and second trimester can be vertically transmitted to fetus causing severe disease of fetus.
Severe disease could result from immune complex formation based on studies with a mouse model
Arenaviridae: Genus: Arenavirus: Lassa fever (Old World Arenavirus)
LFV causes severe febrile illness in humans with 20% mortality rate. Infection involves many organs, but rarely a benign febrile illness has been documented.
Clinical Symptoms: Seen mostly in Africa, patients develop skin hemorrhages, high fever (hemorrhagic fever) mouth ulcers and severe muscle ache.
Virus spreads from human to human and rodent to human. Rats in Africa are chronically infected throughout their lives and shed high levels of virus in the urine
Arenaviridae: Genus: Arenavirus: Tacaribe complex (New World Arenavirues)
These are a group of viruses causing hemorrhagic fever in South America, Trinidad, Florida Everglades, Argentina (Junin)and Bolivia (Machupo). Hemorrhagic fevers often result. Mosquitoes and mites may transmit virus, but rodent urine and feces are the primary means of transmission of animals
Clinical Symptoms: Hemorrhagic fever is characterized by petechiae, bleeding in the GI tract, uterus, nasal cavity and GU tract
15 New world arenaviruses are recognized
Misc
Many of the hemorrhagic fever viruses are candidates for weaponization into bioweapons. One possible mode of dissemination of arbovirus caused hemorrhagic fevers is to raise large populations of infected mosquitoes and release them into a human population. The vectors would do the work of the terrorist in transmitting viral agents. This same principle pertains to Toga and Flavivirures that are also transmitted by mosquitoes or other insect vectors.
