European brown hare syndrome (SLP onwards) is a very contagious acute disease. It affects the European hare, Lepus europaeus, and to the mountain hare, Lepus timidis.
Brown hare syndrome: characteristics
It was first described in 1980 in the north of the continent, but its etiology was not clearly known until years later, when the presence of a virus with characteristics very similar to that produced by rabbit hemorrhagic disease (EHC) was demonstrated. Because of these similarities, At first, both pathologies were considered as one.
The only animals that have been shown to be affected by this disease are the hares. Although it is true that, in some experiments, certain rabbit breeds have shown seropositive reactions in the laboratory.
Distribution, history and evolution
There have been cases of brown hare syndrome in many European countriesas: Germany, Italy, Belgium, United Kingdom, Croatia, Sweden, Finland, Spain, among others. Nevertheless, it was not released outside the European territory until 2003.
Interestingly, SLP appeared in Europe long before rabbit hemorrhagic disease, a disease nowadays well known to breeders of these animals.
The origin of this virus is difficult to track. It is known that he could have mutated a Calicivirus from the predecessors of lagomorphs Eurasian. Or by the introduction of rabbits and hares from Latin America.
Clinical signs of brown hare syndrome
As expected, the symptomatology is quite similar to that of rabbit hemorrhagic disease. While it is true that, even the most acute forms, last a little longer than the EHC, and cause less casualties.
Even so, the hares can die suddenly, hardly showing signs of disease. But the habitual thing is the appearance of changes in the behavior. For example, the escape reflex disappears, they spin, movements are uncoordinated, etc. And finally seizures and death occur.
In the breeding grounds of hares, other symptoms can also be observed, such as anorexia, excitation, and respiratory distress during agony.
During an outbreak in one of these hatcheries, up to 50% of the hares may show chronic or milder signs of the disease.They usually become evident by jaundice in the mucous membranes and subcutaneous tissues.These animals can recover or die after several days.
During necropsy, the most common findings are edema and congestion of the respiratory mucosa, internal hemorrhages, enlarged liver and spleen, and generalized jaundice.
Transmission, epidemiology and impact on hare populations
Brown hare syndrome is a very contagious disease, oral-fecal or respiratory transmission. Both humans, such as birds and insects can act as vectors. The virus, in addition, is quite resistant in the medium, withstanding acidic pH. It can remain infective for up to 3-4 months.
The disease has not yet been described in hares less than 40-50 days old. And children under 2-3 months usually suffer subclinically and do not have to die.
Although a rapid increase in mortality in a population of hares is usually associated with PFS, the truth is that, after the first outbreak, the disease usually becomes endemic. And the areas where it becomes endemic tend to keep their hare populations stable. This is because most individuals have developed immunity, and mortality drops.
Treatment and control of brown hare syndrome
There is no specific treatment against the SLP virus. But it has been proven that the administration of an antiserum from convalescent or hyperimmunized individuals reduces mortality.
There are no commercial vaccines for hares. But when a serious outbreak appears on a farm, vaccines can be prepared from the livers of diseased hares.
However, in nature the transmission cannot be controlled. And eradication is so difficult that it is considered impossible.
In breeding centers prevention is based on:
- The use of quarantines.
- The hygiene of the facilities.
- The absence of contact with wild hares or predators.
- Serological tests on animals that enter the farm for the first time.