Researcher Eva Calvo Pinilla is considered one of the greatest experts in the study of the epizootic hemorrhagic disease virus -EHE-. She works at the INIA-CSIC Animal Health Research Center (CISA) and is part of the team led by Dr. Javier Ortego that is working on a vaccine to combat this disease in Spain.
What consequences has EHE had on livestock farming?
—This virus is producing a disease that can be serious in cattle and deer, although not in all infected animals. It produces clinical signs such as fever, lack of appetite, cyanosis and edema of the tongue, conjunctivitis, reduced milk, diarrhea and lameness, among other symptoms. They usually last about 2-3 weeks, producing great economic losses, especially due to the reduction of milk and meat. It is very difficult to know what the mortality rate is in cattle, because I really don’t know how many animals have been infected for sure. However, there has been a significant increase in animal mortality in those infected farms, and more abortions and fetal malformations are being recorded; according to information that has not come from veterinarians. In other global epidemics of this virus, the fatality rate in cattle has been around 1-5%, and the economic losses have been very high due to the morbidity caused by the disease.
Infertility is detected in bulls, calves that are born blind… Is it attributable to EHE?
—This virus replicates in a large number of the animal’s organs, hence the pathology it produces. The virus also reaches the testicles and is believed to be transmitted through semen. This could be the reason for the infertility detected in infected animals. Another closely related virus, bluetongue virus, causes infertility in some cases. Abortions and fetal malformations are probable since the virus could cross the placental barrier.
Why does it affect some animals and others differently?
—Viruses generally cause disease or go unnoticed asymptomatically. This depends on genetic factors and the previous immune status of the animal. The most common form of HEV manifests itself with fever, lack of appetite, edema of the tongue, conjunctivitis, and general deterioration of the animal.
Why do some farms suffer from the disease and other neighboring farms do not?
—The disease manifests itself in some animals, not all. The VEHE virus is transmitted by Culicoides insects, they are not mosquitoes, but they are usually called that, although they are more like gnats. The movement of Culicoides depends greatly on wind currents, so this can cause infected insects to reach one farm and not another even if it is close. The movement of the virus will depend on the transport of infected ruminants or the spread of the infected vector with livestock or wind.
Why do you think the incidence in Andalusia could have been lower than in Castilla y León or Extremadura?
—This may be because there was some immunity on the farms in Andalusia, at least in some areas where outbreaks were detected in November 2022. As many animals are asymptomatic, many could have been infected without the knowledge of the farmers, and in them there would be immunity against the virus.
Can anything be done to prevent the disease?
—Prevention measures are to try to control the Culicoides population and the movement of animals. In view of the spread of this virus throughout the country, these measures are not enough. A similar situation occurs with the bluetongue virus, closely related to HEV, whose control has only been improved with vaccines.
Is the vaccine possible in 2024?
—It will be very difficult to have an effective recombinant vaccine in 2024 due to the little time we have for the entire process. It may be more likely to have an inactivated vaccine from a company in the sector in a shorter time. This type of vaccine is faster, but it is less effective than the recombinant ones and does not allow serological differentiation between infected and vaccinated animals.
Is there enough research?
—In our research group at the CISA-CSIC, directed by Doctor Ortego, we are dedicated to the study of recombinant vaccines. We have recently obtained small funding from the EU to develop a recombinant vaccine against HEV in collaboration with Dr. Martínez Costas, from Ciqus-USC. Recombinant vaccines seek greater effectiveness than conventional vaccines, as well as a longer duration of immunity and that allow serological differentiation between infected and vaccinated animals (DIVA strategy), something that inactivated vaccines do not allow and which is essential for transport and livestock trade.
Would more financing allow it to be obtained in 2024?
—The call for the national research plan is open in January and we have requested funding to accelerate the development of the recombinant vaccine. But it takes time. Furthermore, research with animals is going slowly, we believe that we will be able to do the first tests on mice this year but the definitive tests on cows are more complicated due to authorizations and facilities. In our center there is a security level 3 facility (required for this virus) but few cattle could be housed due to their size, so it would have to be done in several experiments and this lengthens the time. We are a public research center that It belongs to the CSIC and our vaccine research goes as far as obtaining small-scale results. Then it has to be a veterinary vaccine production company that markets said vaccine.
Are there more groups in Spain investigating the vaccine?
—I am not aware that any other Spanish public laboratory is researching a vaccine for HEV. But it could happen that a veterinary vaccine company was thinking about producing an inactivated vaccine (faster but less effective).
What immunity do you think the cattle that overcame the disease have now?
—It has not yet been proven how long immunity could last but it is believed that it could be more than a year, since in epidemics in other parts of the world they have observed a lower incidence in the following year.
2024-01-22 18:19:00
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