Experiment with the Rift Valley fever virus: an achievement at European level

2019-04-08T11:34:40+02:00March 29, 2019|Tags: , , |
  • One of the great achievements of the laboratories of high biological security of the RLASB has been to experimentally reproduce in sheep the cycle of the infection by the virus of the Rift Valley fever.
  • The study allowed obtaining clinical, virological and immunological data on the consequences of virus infection in ovine animals, in addition to confirming the susceptibility of native ruminants to infection with the virus and to better understand the pathology of this disease.

Inoculación del virus en una oveja. RLASB CC BY 2.0 NC

Inoculation of the virus in a shep. Photo: RLASB (CC BY 2.0 NC)

Rift Valley fever is an endemic disease of the African continent that mainly affects sheep, cattle and also camelids, but totally unknown in Europe. It mainly affects sheep, cattle and camelids. The virus that causes this disease is transmitted through the bite of infected mosquitoes between animals and also from animals to people, so it is also considered a zoonotic disease. Although infection in men is usually accompanied by limited or moderate symptoms-similar to those of influenza-a percentage of patients can develop severe symptoms, such as vision problems, encephalitis and, in more severe cases, the appearance of a hemorrhagic syndrome. In some cases, both in animals and humans, the infection can be lethal.

In animals, prevalence ranges have been described ranging from 100 cases per year to more than 100,000 in the most serious outbreaks, whose most notable feature is the large number of abortions in cattle. In men less than 1% of the most severe cases usually end in hemorrhagic disease. The last major outbreak of the disease occurred in 2006-2007 in Kenya, Tanzania and Somalia, where more than 180,000 people were affected in the areas of the outbreak and the case fatality rate (the percentage of deaths of hospitalized patients) was unusually high (28%)

Towards a better understanding of Rift Valley fever epidemiology in the south-west of the Indian Ocean - Scientific Figure on ResearchGate. Available from: https://www.researchgate.net/figure/Cycle-of-Rift-Valley-fever-The-virus-can-be-maintained-in-an-enzootic-cycle-involving_fig2_256478007 [accessed 19 Mar, 2019]

Towards a better understanding of Rift Valley fever epidemiology in the south-west of the Indian Ocean – Scientific Figure on ResearchGate.

Rift Valley fever is a paradigm among infectious diseases as it is the only viral hemorrhagic disease transmitted by mosquitoes that affects livestock and people alike. The characteristics of this pathogen suppose an additional difficulty to its study, since facilities of high biological security are needed to manipulate the virus and to make experimental infections in animals. All this work involves using special personal protective equipment for this type of conditions and secondary engineering barriers, but also procedural.

Experimental infections with Rift Valley fever virus in ruminants for the first time in Europe

In 2017, the first experiment with this virus was carried out in sheep at the facilities of the INIA-CISA and IRTA-CReSA nodes. The study allowed obtaining clinical, virological and immunological data on the consequences of virus infection in ovine animals, in addition to confirming the susceptibility of native ruminants to infection with the virus and to better understand the pathology of this disease. After establishing the infection model, different efficacy studies of experimental vaccines were carried out both in laboratory animals (mice) and in sheep. In addition, collections of specific sera were obtained that have been used to prepare and validate diagnostic tests for the disease.

Imagen de microscopio del virus del Valle de Rift.

Microscope image of the Rift Valley virus.

Finally, it was demonstrated under experimental conditions that some mosquito species present in Spain such as the common mosquito (Culex pipiens) or the tiger mosquito (Aedes albopictus) can transmit the virus and, in this way, contribute to the spread of the disease. The study that found it was recently awarded by the Royal Entomological Society as the best article published during the period 2017/2018.

Thanks to the experiments carried out in the facilities of the RLASB, more information about this disease is available to improve the diagnosis, Know the cycle of the infection and analyze the consequences on human and animal health.

Is the Rift Valley fever virus in Spain?

Currently in Spain there is no circulation of the Rift Valley fever virus. The arrival of the Rift Valley fever virus could have serious consequences for both human and animal health, as it could put at risk the economy associated with animal production and the agri-food industry. In addition, it has been seen that the virus could be perpetuated endemically in the peninsula, since there are native species of mosquitoes that are capable of transmitting the virus to their offspring, which would maintain and further spread the disease.

For this reason, it is It is even more important to use high biocontainment facilities (level 3 and 4 OIE biosecurity) to avoid any type of transmission or release of the pathogen to the environment during the research tasks with this virus, which could trigger the start of an endemic cycle. The more knowledge available about this disease, the better preventive strategies can be designed, such as vaccines, and control in the event that the virus reaches Spain.