(a) Fundus photograph of the right eye of a patient with Rift Valley fever shows a large active geographic retinitis involving the macula. (b) Six months later, the focus of retinitis healed leading to severe sheathing with optic disc atrophy (Courtesy, E. Abboud)
(a) Fundus photograph of the right eye of a patient with Rift Valley fever shows a large active geographic retinitis involving the macula associated to retinal hemorrhages. (b) Fundus photograph of the same eye four months later shows resolution of the focus of retinitis leading to an atrophic macular retinochoroidal scar (Courtesy, E. Abboud)
Once an outbreak is recognized and early cases are diagnosed, it becomes easier to suspect further cases of RVF. The most common method of laboratory diagnosis is based on serologic testing to detect anti-RVF virus IgM antibodies or a rising titer of IgG antibodies in the serum by ELISA technique. Furthermore, viral RNA by RT-PCR in serum or other tissue samples confirms the diagnosis of RVF [15, 16].
14.6 Differential Diagnosis
The differential diagnosis for RVF retinitis includes other infectious entities such as measles, rubella, influenza, cytomegalovirus, varicella zoster virus, herpes simplex virus, Chikungunya, Dengue fever, rickettsial infection, Lyme disease, syphilis, and cat scratch disease . Other hemorrhagic fever viruses have been reported to have ocular involvement such as Hantaan virus, Puumala, Marburg, and Ebola viruses . The differential diagnosis of RVF retinitis may also include non-infectious entities like Behçet’s retinitis.
These diseases can be differentiated from RVF by clinical history and serologic testing.
The current treatment of RVF is entirely supportive with intravenous fluids and when indicated, blood transfusion, hemodialysis, or mechanical ventilation. There is no antiviral therapy with proven efficacy in this setting . Preventive measures are recommended including intensified mosquito control, and protection against mosquito bites in areas of epizootic and human RVF activity [17, 18]. Education regarding modes of disease transmission and necessary precautions, especially protection against mosquito bites is vital. Vaccination of livestock may be a key element in breaking the chain of human epidemics, and could lead to control of this significant public health threat .
Prognosis of RVF virus infection systemic disease is good in most patients. However, severe cases may result in death . Ocular involvement is frequently associated with permanent visual loss resulting from macular and paramacular scarring, vascular occlusion, or optic atrophy [4–10].
RVF infection should be considered in the differential diagnosis of macular or paramacular retinitis in a patient living in or returning from a specific endemic area, especially during confirmed outbreaks of the disease. Systemic involvement in RVF infection is usually self-limited; however, ocular involvement may lead to severe permanent visual impairment in most cases.
Systemic disease: influenza-like symptoms with a biphasic-pattern fever, life- threatening hemorrhagic fever.
Ocular disease: macular or paramacular necrotizing retinitis, anterior uveitis, occlusive retinal vasculitis, retinal hemorrhages, vitritis, optic disc edema.
Diagnosis: primarily based on epidemiologic data and systemic symptoms, and confirmed by serologic testing or PCR.
Treatment: entirely supportive, with prevention the mainstay of RVF infection control.
Systemic disease: usually self-limited.
Ocular involvement: persistent severe visual loss due to macular scarring, vascular occlusion, and/or optic atrophy.