Rift valley fever (patient information)

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

Rift valley fever

Overview

What are the symptoms?

What are the causes?

Who is at highest risk?

Diagnosis

When to seek urgent medical care?

Treatment options

Where to find medical care for Rift valley fever?

Prevention

What to expect (Outlook/Prognosis)?

Possible complications

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## Overview

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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. Patients contracting this disease will usually be individuals who live in close proximity to livestock and those who frequently get mosquito bites. The main presenting symptoms are fever, headache and weakness. The disease is usually self-limiting in most individuals and requires supportive treatment measures.

## What are the symptoms of Rift valley fever?

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* Common Symptoms
* Fever
* Body aches
* Weakness
* Loss of Appetite
* Vomiting
* Profuse sweating
* Headaches
* Bleeding from the nose

* Symptoms due to complications
* Decreased vision
* Pain behind the eye
* Increased sensitivity to light
* Spots in the visual field
* Yellowish discoloration of skin
* Blood in vomit, urine or stools
* Body rash
* Hallucinations
* Disorientation
* Paralysis

## What causes Rift valley fever?

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* RVF is caused by the Rift Valley fever virus or RVFV, which belongs to the Bunyaviridae family.
* The genetic composition of the virus is a single-stranded RNA consisting of three segments (L, M and S) out of which L and M possess a negative charge while the S segment has both sense and antisense orientation.[1]
* The virus’ RNA polymerase is coded by the L component which is responsible for replication and transcription of messenger RNA (mRNA) while glycoproteins and protein are encoded via the M segment. [2]
* Nucleoproteins and non-structural proteins are coded by the S segment in its antisense and sense orientation respectively.

## Who is at highest risk?

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* Travel to endemic areas of RVF are at increased risk of exposure to the disease [3]
* Visiting rural areas and sleeping outside in locations where RVF incidence is high can increase exposure to mosquitos.
* Farmers, herdsman and veterinarians, who handle livestock in endemic areas increase their risk of exposure to the virus.

## Diagnosis

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* The main purpose is to detect the virus in the blood, which can be accomplished by a few tests.
* RT-PCR (reverse transcriptase-polymerase chain reaction) and ELISA test (for antigen detection) may be used during the initial phase of the illness.
* IgM Antibodies : Once the viral load decreases in the blood, IgM antibody tests are helpful in detecting the presence of ongoing infection.
* IgG Antibodies : In recovered cases, testing for IgG antibodies aid in identifying cases who may have had a recent episode of RVF.

## When to seek urgent medical care?

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In case of unremitting fever, bleeding from any mucosal site, disorientation, blurred vision, focal muscle weakness or severe weakness, the patient should seek medical care as these symptoms point towards the complications of RVF and require medical attention.

## Treatment options

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* Mainstay of treatment in most RVF patients is usually supportive with monitoring of body temperature and blood pressure.
* Fluids may be given to patients reporting weakness or low blood pressure.
* There is no specific recommendations for treatment for RVF by the FDA. [4]
* Drugs having renal, hepatic or coagulation side effects should be avoided in RVF patients.
* Ribavirin showed promise in rodent models but was stopped after development of neurological symptoms in some of the patients it was administered during the RVF outbreak in Saudi Arabia in the year 2000. [5]

## Where to find medical care for Rift valley fever?

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* Treatment can be sought at the nearest medical center.
* Usually areas where Rift valley fever is endemic, will have dedicated health care centers catering to people with corresponding symptoms.

## Prevention

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* Avoiding exposure to infected or unwell livestock.
* Separating and isolating animals with symptoms from the rest of the herd will help in curtailing the spread amongst the animals, which in turn will decrease the risk of transmission of the virus from animals to humans.
* Effective mosquito control is pertinent in reducing transmission to humans.
* Many vaccines have been developed over the course of history, with the major challenge being, formulating a one-shot vaccine for livestock. Few vaccines are undergoing testing to gain approval for use in animals. [6]

## What to expect (Outlook/Prognosis)?

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* Majority of individuals develop a mild to moderate course of fever and body aches, from which they recover spontaneously.
* Complications are seen rarely with ocular problems occurring in about 1 to 2% cases, while encephalitis and hemorrhage developing in approximately 1% cases or less. [7]
* Hemorrhagic fever is associated with a high fatality rate of 50%, while the fatalities reported overall are only around 1% of total cases.
* Only 1 to 10% of cases with ocular manifestations continue to have lifelong, irreversible impairment of vision.

## Possible complications

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* Neurological manifestations
* Cases of encephalitis following infection with RVFV have been described in the literature. [8] [9]
* Paralysis of body like hemiparesis has also been reported in RVF cases. [10]
* Brain lesions due to RVF present with features of coma, increased salivation, irregular flailing movements of the upper limbs and hallucinations. [11]
* Hemorrhage
* Cases with hemorrhage due to RVF can be fatal, with variable times reported till the occurrence of death.
* Clot formation
* Ophthalmological manifestations
* Loss of peripheral vision or blurred vision is commonly reported after infection.
* Unilateral or bilateral eyes may be involved with features of edema in the macula, retinal bleeding or loss of transparency in the vitreous.[12]

## Sources

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1. ↑ Giorgi C. et al. 1991. Sequences and coding strategies of the S RNAs of Toscana and Rift Valley fever viruses compared to those of Punta Toro, Sicilian sandfly fever, and Uukuniemi viruses. Virology 180:738–753
2. ↑ Gerrard S. R. and Nichol S. T.. 2007. Synthesis, proteolytic processing and complex formation of N-terminally nested precursor proteins of the Rift Valley fever virus glycoproteins. Virology 357:124–133.
3. ↑ https://www.cdc.gov/vhf/rvf/exposure/index.html
4. ↑ Hartman A. Rift Valley Fever. Clin Lab Med. 2017;37(2):285-301. doi:10.1016/j.cll.2017.01.004
5. ↑ Bird BH, Reynes JM, Nichol ST. Rift Valley Fever. In: Magill AJ, Strickland GT, Maguire JH, Ryan ET, Solomon T, editors. Hunter’s Tropical Medicine and Emerging Infectious Disease. 9. Elsevier Health Sciences; 2012.
6. ↑ Njenga MK, Njagi L, Thumbi SM, et al. Randomized controlled field trial to assess the immunogenicity and safety of rift valley fever clone 13 vaccine in livestock. PLoS neglected tropical diseases. 2015 Mar;9(3):e0003550.
7. ↑ https://www.nj.gov/agriculture/divisions/ah/diseases/riftvalley.html
8. ↑ Maar SA, Swanepoel R, Gelfand M. Rift valley fever encephalitis. A description of a case. Cent Afr J Med. 1979;25:8–11.
9. ↑ Alrajhi AA, Al-Semari A, Al-Watban J. Rift valley fever encephalitis. Emerg Infect Dis. 2004;10:554–555
10. ↑ Laughlin LW, Girgis NI, Meegan JM, Strausbaugh LJ, Yassin MW, Watten RH. Clinical studies on rift valley fever. Part 2: Ophthalmologic and central nervous system complications. J Egypt Publ Health Assoc. 1978;53:183–184
11. ↑ van Velden DJ, Meyer JD, Olivier J, Gear JH, McIntosh B. Rift valley fever affecting humans in south africa: A clinicopathological study. S Afr Med J. 1977;51:867–871.
12. ↑ Siam AL, Meegan JM, Gharbawi KF. Rift valley fever ocular manifestations: Observations during the 1977 epidemic in egypt. Br J Ophthalmol. 1980;64:366–374