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Rift Valley Fever Rift Valley Fever Sherine

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					Rift Valley Fever
Sherine Shawky, MD, Dr.PH Assistant Professor Department of Community Medicine & Primary Health Care College of Medicine King Abdulaziz University shshawky@hotmail.com

Rift Valley Fever
• Acute febrile viral disease • Affecting animals & humans • Causes influenza-like illness • May lead to high morbidity, mortality & economic loss

Geographic Location & Geologic Feature of Rift Valley
• Length: 6,000miles • Site: Lebanon to Mozambique • Largest part: Kenya • Development: Subterranean forces • Feature: Dambos

Causes of Outbreaks
Rainfall or Inundation Wetlands & Stagnant water

Vegetation Growth
Flourishing of mosquitoes Transmission of Infection

Outbreaks in the Last Half Century
Date 1950-1951 1967-1970 1969 1976-1977 1977-1980 1987 1990-1991 1993 1997 1999 2000-2001 Country Kenya Nigeria Central African Republic Sudan Egypt Mauritania Madagascar Egypt – Senegal Kenya – Somalia South Africa Saudi Arabia - Yemen

Glycoprotein spikes G1 G2

RVF Virus
S L M Lipid envelope

Coiled nucleocapsid RNA+N protein

transcriptase

Mode of Transmission
• Mosquitoes • Other blood suckling insects • Contact with blood or other body fluids of infected animals • Consumption of infected milk

Mode of Transmission (cont.)
• Contact with blood or other body fluids of infected humans in late stages of disease • Airborne transmission • Inoculation through broken skin

Target
• Liver: focal necrosis • RBCs: haemagglutination • Brain: necrotic encephalitis

Clinical Picture 1- Non-Human Host
• Fever • Hepatitis • Abortion • Death –Adults: 10-30% –Neonates: 100%

2- Human Host
• Incubation period of 2-6 days • Asymptomatic • Flu-like illness • Abdominal pain • Photophobia • Recovery in 2-7days

Complications of RVF 1- Ocular Lesions
• Rate: 0.5-2.0% • Lesions: • Onset: 1-3 weeks –Macular lesions –Retinitis • Presentation
–Localized pain –Blurred vision –Loss of vision: 1.0-10.0% –Retinal detachment

• Death: rare

2- Meningoencephalitis
• Rate: < 1.0% • Presentation: • Onset: 1-3 weeks –Severe headache –Vertigo • Death: rare
–Seizures –Coma

3- Haemorrhagic fever
• Rate: < 1.0% • Lesions: • Onset: 2-4 days –Acute fulminant hepatitis • Presentation: –DIC –hemorrhagic –Hemolytic phenomenon anemia • CFR: 50.0%

High Risk Groups
• People who sleep outdoors at night • Slaughterhouse workers, butchers veterinarians and others who handle blood, other body fluids or tissues of infected animals

High Risk Groups (cont.)
• Doctors and nurses in contact with infected cases at late stages of the disease • Laboratory technicians • Travellers visiting epidemic areas

Diagnosis of RVF
• Antibody detection -ELISA -EIA • Virus detection -Virus isolation -Antigen detection -PCR

Prevention & Control I. Animal
• Vaccination of unaffected animals –Live attenuated vaccine –Killed vaccine • Notification of affected animals • Application of safe insecticides to eradicate blood suckling insects

I- Animal (cont.)
• Periodic surveillance of susceptible animals to assess immune status • Application of quarantine measures for testing of imported animals • Rapid burial of dead bodies

II- Vector
• Removal of stagnant water • Weekly treatment of water collections using insecticides • Application of insecticides every other day in all gardens • Removal of objects that can act as possible water containers

III- Humans: 1- General Measures
• Sleeping indoors • Using bed nets during sleep • Putting screens on windows • Wearing clothes that protects whole body

III- Humans: 1-General Measures (cont.)
• Applying mosquito repellents • Using spray on clothes • Avoiding peaks of mosquito activity • Avoiding presence near vegetations in the evening

III- Humans 1-General Measures (cont.)
• Avoiding direct contact with animals • Washing hands after contact with animals, their blood or other body fluids • Avoid drinking raw milk

III- Humans 2- Community Measures
• Health education • Epidemiologic research program • Active disease surveillance • Check measures at air, sea and land entry points

III- Humans 3- Occupational Measures
• Wearing masks, gloves, gowns and other barriers according to infected host’s condition • Laboratory samples should be handled by trained staff

III- Humans 3- Occupational Measures (cont.)
Application of water, soap and antiseptic solution on exposed parts • Application of copious water and eye wash solution on exposed conjunctiva
•

Management of Suspected Cases
• Notification • Ascertainment of cases • Identification, screening and surveillance of contacts

Recommended Investigations For Suspected Cases
• CBC • Urea • Creatinine • AST, ALT • ALP,Bilirubin • Albumin • PT & PTT • LDH & CPK • Hepatitis A IgM & IgG, HBsAg, HBcAB, HCV Ab • RFV seriology & viral culture

Management of unhospitalised Patients
• Isolation at home • Contacts should wear masks, gloves and protective clothes • Safe disposal of patients linens & clothes • Close follow-up for 6 weeks

Indications For Hospitalisation
• Thrombocytopenia< • Shock 3 100,000/mm • Decreased urine • Anaemia< 8gm/dL output • AST & ALT > • Creatinine>150mol/L • Confusion or other 200U/mL • Bilirubin>100 CNS manifestation • Evidence of DIC mol/L

Management of Hospitalised Patients
• General Supportive Measures • Isolation in negative airway pressure room • Safe disposal of soiled linens • Safe disposal of solid medical waste • Safe sewage disposal

Management of Hospitalised Patients (cont.)
• Ribavirin, Interferon, Immune Modulators & Convalescent Phase Plasma give promising results • Introduction to ICU or haemodialysis unit if indicated

• Hospital discharge after: – Improvement in general status –Decline in liver symptoms –Recovery from DIC • Follow-up in ophthalmology and medical clinics for 6 weeks • Safe burial practice for dead cases

Conclusion
• RVF is spreading outside Africa • Although often mild, may lead to high morbidity and mortality • No vaccine for humans • No specific treatment • Preventive measures are crucial


				
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posted:11/13/2009
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