Rift valley fever overview

Rift valley fever Microchapters
Home
Patient Information
Overview
Historical Perspective
Pathophysiology
Causes
Differentiating Rift valley fever from other Diseases
Epidemiology and Demographics
Risk Factors
Natural History, Complications and Prognosis
Diagnosis
History and Symptoms
Physical Examination
Laboratory Findings
Imaging Findings
Other Diagnostic Studies
Treatment
Medical Therapy
Surgery
Prevention
Cost-Effectiveness of Therapy
Future or Investigational Therapies
Case Studies
Case #1
Rift valley fever overview On the Web
Most recent articles
Most cited articles
Review articles
CME Programs
Powerpoint slides
Images
American Roentgen Ray Society Images of Rift valley fever overview All Images X-rays Echo & Ultrasound CT Images MRI
Ongoing Trials at Clinical Trials.gov
US National Guidelines Clearinghouse
NICE Guidance
FDA on Rift valley fever overview
CDC on Rift valley fever overview
Rift valley fever overview in the news
Blogs on Rift valley fever overview
Directions to Hospitals Treating Rift valley fever
Risk calculators and risk factors for Rift valley fever overview

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Aakash Hans, MD[2]

Overview

Rift valley fever (RVF) is a zoonotic disease caused by the RVF Virus (RVFV) that mainly affects livestock and is responsible for illness in humans. The disease process in humans ranges from a simple febrile illness to fatal hemorrhagic conditions. Other symptoms include eye involvement and encephalitis. RVF is also known to have caused miscarriage in women. Mosquitoes, livestock and humans form parts of the virus’ life cycle. With a complex transmission process and lack of specific vaccines or treatment makes the disease difficult to control. Since mosquito breeding is an important factor for the spread of disease, regions with heavy rainfall are at risk to have increased numbers of cases and mortality.

Historical Perspective

In the year 1930, Rift Valley fever virus (RVFV) was discovered as the pathogen causing an increased incidence of hepatitis in animals belonging to the Rift Valley in Kenya. The primarily affected animals were sheep, with deaths and miscarriages in sheep along with mortality in lambs born recently.

Classification

• There is no classification used for Rift valley fever.

Pathophysiology

RVF is transmitted to humans either via mosquito bite or via exposure to infected animals. There is no evidence of human to human transmission of the disease. The disease manifests in three major stages:

• Early infection
  • It is mainly due to entry and survival of the virus in macrophages and dendritic cells.
• Liver infection
  • The virus most commonly infects liver cells and causes inflammation via IL-10.
• Late infection
  • The virus begins to invade neuronal cells leading to neurological symptoms.

Cause

Rift valley fever is caused by the Rift Valley fever virus (RVFV). The virus is a single-stranded RNA virus belonging to the Bunyaviridae family.

Differentiating Rift valley fever from other Conditions

The majority of differential diagnoses for RVF arise from other diseases which are prevalent in travelers and present with fever. All these disease would share a similar history of recent travel to an endemic area, followed by development of fever and body aches.

Epidemiology and Demographics

The virus is able to stay active outside the human body even when it is not being actively transmitted amongst animals. Heavy rain causes mosquitos to breed in large numbers, which translates into increased transmission to livestock. As more animals get infected, the risk of the virus being transmitted to humans increases. Humans acquire the infection by being exposed to animal fluids and products. Most of the disease surges till now have been seen in some regions of Africa and countries belonging to the Arabian peninsula. Since its discovery around the year 1930, there have been outbreaks of RVF, starting in the 1950 in the African countries, South Africa and Kenya.

Risk factors

Risk factors applicable to Rift valley fever are similar to other zoonotic diseases. Exposure to mosquitos feeding on infected animals is the main cause of acquiring the infection. All human activities and habits which expose them to mosquitos or the infected animals would qualify as risk factors of the disease.

Natural History, Complications and Prognosis

Rift valley fever is a self-limiting illness in majority of patients. The symptoms appear around 2-3 days after exposure. The main symptoms are fever and body aches. Fever usually subsides by 3-4 days after the beginning of symptoms. Complications can arise if the fever recurs again after remission and the patient continues to be febrile. Neurological, ophthalmological and hemorrhagic features are the commonly seen complications. Prognosis is good for most of the patients who only have the febrile illness which subsides on its own. The patients who suffer from complications usually recover at a slower pace out of which some succumb to the complications.

Diagnosis

Diagnosing Rift valley fever requires index of suspicion for individuals presenting with fever, especially after exposure to infected animals or mosquitos.

Diagnostic study of choice

• RT-PCR is used to diagnose RFV in the earlier days of the illness.
• ELISA test can also be used for diagnosis during the early phase of the disease.
• IgM Antibodies test can be used if 3-4 days have passed since the onset of symptoms

History and Symptoms

• The hallmark of Rift valley fever is the development of a febrile illness in the individual with a history of recent exposure to animals or mosquitos.
• Other common symptoms include headache, fatigue, joint pain and loss of appetite.
• Individuals may also present directly with complications of RVF like disorientation, yellowish discoloration of skin or bleeding from mucosal sites.

Physical Examination

• The physical examination in individuals with Rift valley fever can be significant for:
  • Fever
  • Low Blood Pressure
  • In cases of severe RVF, findings like body rash, yellow colored skin or disorientation may be seen.

Laboratory Findings

• Anemia
• Deranged coagulation profile
• Raised serum bilirubin

Electrocardiogram

There are no ECG findings associated with Rift valley fever.

X Ray

There are no x-ray findings associated with Rift valley fever.

Echocardiography and Ultrasound

On ultrasound imaging of the abdomen Rift valley fever may show an enlarged liver and an enlarged spleen.

CT scan

There are no CT scan findings associated with Rift valley fever.

MRI scan

There are no MRI findings findings associated with Rift valley fever.

Treatment

Medical therapy

The optimal therapy for Rift valley fever is conservative and supportive management with anti-pyretics and intravenous fluids.

Surgery

There are no established surgical therapies for Rift valley fever.

Primary Prevention

• Avoiding exposure to ill animals.
• Protection from mosquito bites.
• Vaccination of the livestock.

Secondary Prevention

There are no established measures for the secondary prevention of Rift valley fever.