Page 155 - TBE_Book_V2_2019

Chapter 8: TBE in animals

Prevention The few case reports available suggest that
clinical TBE in horses is a rare event, although
There is no licensed anti-TBE vaccine for dogs, basic horse population-based data are
although dogs develop detectable antibody missing. Looking at the few seroprevalence
titers after vaccination with a human studies in horses, the prevalence of anti-TBE-
27
vaccine. Tick protection is the most impor- antibodies ranged from 26.1% and 13% in
29,32
30
tant measure to avoid transmission and Austria to 2.9% in central Germany, and
31,33
infection, mainly performed by regular admin- 5.2% and 23.4% in southern Germany 34 to 0
istration of acaricidal substances (spot on, of 40 horses investigated in Hungary or 0 of
35
tablets, shampoos, collars) and immediate tick 2349 horses from the Czech Republic. Cross-
3 reactivity to other flavivirus may influence
removal after detection by the owner. 35,36
these results. Horses have been suggested
Regular anti-tick measures are essential to to be good sentinel animals for human TBEV
reduce transmission risk all through the year infection risk, because they readily sero-
as single canine cases have been reported convert upon infection, but they stick more to
21
even during the cold seasons of the year. a given territory in comparison to dogs who,
as family members, travel more.

Horses
Domestic ruminants
Although the first clinical case of laboratory-
confirmed TBE in a horse was published more
28
than 35 years ago, our knowledge about the For more than half a century, grazing cattle,
impact of TBEV in horse populations is scarce. goats, and sheep have been known to be
To the best of our knowledge, there are 4 susceptible to TBEV infection. Interestingly,
these ruminants do not develop any clinical
published studies where clinical signs of
symptoms, and even after experimental
neurological disorder could be traced to the
TBEV as etiology. After the aforementioned infection, a slight elevation of body tempera-
37,38
initial published case from Switzerland, 8 ture is a rare finding. However, in 2015, a
horses with clinical symptoms were described five-month-old lamb in Bavaria dis-played
29
in Austria, 2 of which were severely ill; 1 out symptoms of a neurological disorder, and after
euthanasia, TBEV infection was subsequently
of 3 diseased animals from a study in Germany 39
30
had to be euthanized; and again in Germany, diagnosed. Whether this case was the result
some years later, an infected animal had to be of an unknown underlying disease or immuno-
31 suppressive factors cannot be determined.
euthanized.
TBE in domestic ruminants, if it occurs at all,
The clinical picture in horses mirrors that appears to be an extreme exception. Never-
which we described for dogs, displaying a theless, infected animals develop viremia with
40
broad spectrum of neurological symptoms: a duration of up to 19 days. A study in the
ataxia, tonic-clonic seizures, apathy and Swiss canton of Valais found 4.25% of the
stupor, inappetence, mydriasis, convulsions of tested goats to be seropositive according to an
the legs, skittishness, bruxism, and altered ELISA test, with 40.4% of these testing positive
41
reactions to environmental stimuli. Regarding on a serum neutralization test.
therapeutic options and prognosis, a horse
with recumbent status due to TBE has a poor Even if the viremia is shorter than 1 week,
virus is shed via milk and remains infectious in
prognosis as long as it is not possible to force
cheese or other products prepared from
the horse to stand up again.

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