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Rift valley-virus
- 1. RIFT VALLEY VIRUS PRESENTED BY: NAFIZ NOOR SWARNO Id: JANNATUL MEHNAJ MEEM Id:2016-1-77-038 FAMEEMA TASNEEM Id:2015-
- 2. RIFT VALLEY VIRUS It is virus of Bunyavirales family It causes Viral Zoonotic disease Affects primarily livestock (cattle, sheep, goats, camels, etc.) are spread mostly by mosquitoes. Can be transmitted to humans Infection can lead to high rates of disease and death in animals and humans. The Disease Classified as an OIE List A disease (A080)
- 3. Origin In September 2000, an outbreak was confirmed in Saudi Arabia and Yemen, marking the first reported occurrence of the disease outside the African continent and raising concerns that it could extend to other parts of Asia and Europe The total case fatality rate has varied widely between different epidemics but, overall, has been less than 1% in those documented. Most fatalities occur in patients who develop the Hemorrhagic jaundice form. The virus was first identified in 1931 during an investigation into an epidemic among sheep on a farm in the Rift Valley of Kenya. Since then, outbreaks have been reported in sub-Saharan and North Africa.
- 4. Rift Valley fever Phlebovirus Virus classification: Realm: Riboviria Phylum: Negarnaviricota Class: Ellioviricetes Order: Bunyavirales Family: Phenuiviridae Genus: Phlebovirus Species: Rift Valley fever phlebovirus
- 5. Structure of the Virus RVFV belongs to the genus Phlebovirus, family Bunyaviridae. Bunyaviruses are enveloped and have a tri-segmented single- stranded RNA genome of negative or ambisense polarity. The envelope is composed of a lipid bilayer containing the Gn and Gc glycoproteins forming surface subunits. Transcription and replication take place in the cytoplasm The viral genome has three segments which are L,M and S. The L and M segments are of negative polarity while the S segment utilizes an ambisense strategy to code for both N and NSs.
- 6. ETIOLOGY Causative agent: The Rift Valley Fever Virus A family of enveloped negative strand RNA viruses RVF is an Arborvirus which means it is transmitted by arthropod (insects, arachnids, centipedes, crustaceans) vectors and vertebrates Transmitted by mosquito vectors to livestock There is only one serotype of RVF virus. Stable at 60 C to 23 C *Lipid solvents *Detergents *Low pH
- 7. Mode of Action There is no direct person-to-person transmission. Human can be infected in RVF by handling of animal tissues during slaughtering & butchering. By Vector: RVF virus is transmitted primarily by infected mosquitoe bites, mainly the Aedes species, which can acquire the virus from feeding on infected animals. The female mosquito is also able to transmitted the virus directly to her offspring via eggs leading to new generations of infected mosquitoes hatching from eggs.
- 8. Transmission Via Mosquito to Animal & Human Heavy Rainfall, flooding leads to high Mosquito abundance Endemic transmission cycle (rare) Epizootic transmission cycle at the, Dambo Endemic transmission cycle at the, Dambo
- 9. Mode Of Action (Human) The virus infects humans through inoculation, for example via a wound from an infected knife or through contact with broken skin, or through inhalation of aerosols produced during the slaughter of infected animals. Caused by a cytopathic virus that targets the liver and the brain It is suspected that the virus moves from the skin to draining lymph nodes, where it replicates and spreads throughout the body. It may also cross the blood-brain barrier and infect neurons and glia, leading to meningoencephalitis and retinitis two to three weeks after onset of infection
- 10. Susceptibility Susceptibility appears to be general in both sexes at all ages. Humans are highly susceptible to infection but represent dead end hosts. Inapparent infections and mild disease are common. Since infection leads to immunity, susceptible in endemic areas are mainly young children.
- 11. Incubation Period Experimentally, incubation period of this virus in new-born lambs, kids, calves, and puppies, is about 12 hours. The incubation period in adult sheep, cattle, goats, and dogs may be as long as 3 days. In humans, the incubation period is 4 to 6 days.
- 12. SIGNS AND SYMPTOMPS IN ANIMAL Fever Listlessness Weight loss Loss of Appetite Bloody Diarrhea Increased respiratory rate Blood tinged nasal discharge
- 13. SIGNS AND SYMPTOMPS IN ANIMAL Majority have mild symptoms or no symptoms at all. Flu like symptoms: fever, headache, muscle pain, joint pain, etc. Other symptoms that may occur are neck stiffness, sensitivity to light, loss of appetite, and vomiting. Symptoms usually last 4 to 7 days
- 14. Pathogenesis of RVF in Animal Most of the mice infected with wild-type (wt) RVFV ZH548 or ZH501 strains die in 3 to 5 days. The symptom is often followed by death within one hour Mouse: Hamster: The Syrian hamster is one of the most susceptible rodents to RVFV. Death occurs in 2 to 3 days after intraperitoneal inoculation with massive liver necrosis Sheep: Sheep with more than one week old were relatively resistant to RVFV infection, yet did exhibit fever (39 to 40 属C), viremia, diarrhea, nasal discharge, and decreased activity.
- 15. Pathogenesis of RVF in Humans Patients suffer from a self- limiting, febrile illness. Some patients develop neurological disorders,vision loss, hemorrhagic fever or thrombosis. Figure: The pathological forms of Rift Valley fever in humans.
- 16. Advantages and disadvantages of animal models for Rift Valley fever.
- 17. Diagnosis There are several different methods: Serological tests such as enzyme-linked immunoassay (the "ELISA" or "EIA" methods) may confirm the presence of specific IgM & IgG antibodies to the virus. Antigen detection tests and RT-PCR. Virus isolation by cell culture. FIG: RIFT Valley Fever Virus Diagnosis
- 18. Differential Diagnosis Nairobi Sheep diseases: No Hepatitis,not in new born lambs Bluetongue: Foot lesions, also no hepatitis Heartwater: Serous fluid in body Cavities and Neurological Sign Ephemeral fever: Rapid recovery
- 19. Treatment and Vaccines As most human cases of RVF are relatively mild and of short duration. No specific treatment is required for these patients. In severe cases, the predominant treatment is general supportive therapy. Experimentally vaccine has been developed for human use. However, this vaccine is not licensed and is not commercially available.
- 20. Prevention and control Controlling RVF in animals Rift Valley Fever can be controlled by restricting or banning the movement of livestock may be effective in slowing the expansion of the virus from infected to uninfected areas. Animals can be prevented by a sustained programme of animal vaccination. Public health education and risk reduction Practicing hand hygiene, wearing gloves and other appropriate individual protective equipment when handling sick animals or their tissues or when slaughtering animals. Infection control in health care settings
- 21. Prevention and control Vector control: Other ways in which to control the spread of RVF involve control of the vector and protection against their bites. RVF forecasting and climatic models: Forecasting can predict climatic conditions that are frequently associated with an increased risk of outbreaks, and may improve disease control. Strategic larvicidal treatment of mosquito breeding habitats is recommended.
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