Rift Valley FeverSherine 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 OutbreaksRainfall or Inundation

Wetlands & Stagnant water

Vegetation Growth

Flourishing of mosquitoes

Transmission of Infection

Outbreaks in the Last Half CenturyDate Country1950-1951 Kenya1967-1970 Nigeria1969 Central African Republic1976-1977 Sudan1977-1980 Egypt1987 Mauritania1990-1991 Madagascar1993 Egypt – Senegal1997 Kenya – Somalia1999 South Africa2000-2001 Saudi Arabia - Yemen

RVF Virus

Coiled nucleocapsidRNA+N protein

Glyco-proteinspikes

transcriptase

Lipid envelope

S L

MG1G2

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%

• Onset: 1-3 weeks

• Presentation–Localized pain

–Blurred vision

–Loss of vision: 1.0-10.0%

• Lesions:–Macular lesions

–Retinitis

–Retinal detachment

• Death: rare

2- Meningoencephalitis

• Rate: < 1.0%

• Onset: 1-3 weeks

• Death: rare

• Presentation:–Severe headache

–Vertigo

–Seizures

–Coma

3- Haemorrhagic fever• Rate: < 1.0%

• Onset: 2-4 days

• Presentation:

–hemorrhagic phenomenon

• Lesions:

–Acute fulminant hepatitis

–DIC

–Hemolytic 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 & ControlI. 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- Humans1-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- Humans3- Occupational Measures

• Wearing masks, gloves, gowns and other barriers according to infected host’s condition

• Laboratory samples should be handled by trained staff

III- Humans3- 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

• Shock

• Decreased urine output

• AST & ALT > 200U/mL

• Bilirubin>100 mol/L

• Thrombocytopenia< 100,000/mm3

• Anaemia< 8gm/dL

• Creatinine>150mol/L

• Confusion or other CNS manifestation

• Evidence of DIC

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