Rift Valley fever: what do we know today?

Rift Valley fever virus (FVRV) has shown the ability to inflict significant damage to livestock and is also a threat to public health. A review published by researchers of the Centro de Investigación en Sanidad Animal (CISA-INIA) and CReSA discuss several aspects of the virus and measures proposed to limit future epidemics.

A threat for livestock and humans

RVFV is a zoonotic pathogen that primarily affects ruminants but can also be lethal in humans. A negative-stranded RNA virus of the family Bunyaviridae, this pathogen is transmitted mainly via mosquito vectors. While outbreaks have traditionally occurred in sub-Saharan Africa, recent outbreaks in the Middle East have raised awareness of the potential of this virus to spread to Europe, Asia, and the Americas.

Although the virus was initially characterized almost 80 years ago, the only vaccine approved for widespread veterinary use is an attenuated strain that has been associated with significant pathogenic side effects. However, increased understanding of the molecular biology of the virus over the last few years has led to recent advances in vaccine design and has enabled the development of more-potent prophylactic measures to combat infection.

Concern about recent lethal outbreaks

Other considerations, such as RVFV's recent classification as a potential bioterrorist agent, have renewed interest in the study of the virus as well as in the development of prophylactic measures to contain future outbreaks.

Another important factor in recent RVF outbreaks is the increasing number of human fatalities. Human symptoms of this disease range from photophobia and headaches to retinitis and encephalitis. While RVF was originally associated with livestock, recent outbreaks in Kenya have resulted in increased fatality rates among humans, thereby presenting an increased threat to public health.

Nevertheless, due to increased trade with and traffic to the African continent, as well as to climate change affecting northern Africa and southern Europe, there is an increasing consensus that it is only a matter of time before RVF outbreaks will start to affect the agricultural industry in Europe and Asia. The combination of all these factors has resulted in the increased study of RVFV pathogenesis and to more comprehensive research on protection from and prevention of RVF.

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Countries with confirmed cases of Rift Valley fever from July 2009 to November 2010 (indicated in red). Data were obtained from ProMed-mail (International Society For Infectious Diseases [http://www.promedmail.org]).

Prevention and measures

Major advances in the study of RVFV and an extensive assortment of prophylactic strategies have been developed over the last several years. There is increasing consensus that the spread of RVF beyond Africa is no longer a question of if, but when. While the scientific community has started to address the possibility of large-scale epidemics and preventive measures that can be used to stop them, there are still no low-cost, broadly effective vaccines approved for use by the general public. Furthermore, the safety and cost limitations associated with the current approved veterinary vaccines leave significant room for improvement. Hopefully, some of the vaccine candidates discussed will be approved for wide-scale use in the near future.

There is hope that in conjunction with recent epidemiological advances, the health and economic costs associated with RVF virus can be contained.

More information:

Boshra H, Lorenzo G, Busquets N, Brun A. Rift valley fever: recent insights into pathogenesis and prevention. J Virol. 2011 Jul;85(13):6098-105. Review. 

To contact the co-author of this review:

Dr Nuria Busquets Martí
Researcher. Arboviruses and arthropod vectors.
Email: nuria.busquets@cresa.uab.cat
Telephone no.: +34 93 581 4342
Fax: +34 93 581 44 90
Edifici CReSA. Campus UAB
08193 Bellaterra (Cerdanyola del Vallès) Spain

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