A large-scale outbreak of bovine hemorrhagic disease in Israel
Yadin, H.1, Brenner, J.1, Gelman, B.1, Bumbarov, V.1, Stram, Y.1, Oved, Z.2,
Galon, N.3, Klement, E. 4
1. Kimron Veterinary Institute,
2. Israel Veterinary Services, 50250, Bet Dagan.
3. Hachaklait, Caesarea,38900,
4. Koret Veterinary School, Faculty of Agriculture Rehovot, University of Jerusalem, Israel
The Israeli Veterinary Services were notified of a novel disease syndrome
affecting cattle on September 5, 2006, however, the first clinical signs were
seen toward the end of August 2006. The outbreak was first reported from
several dairy farms located in the southern Jordan River Valley in Israel. The
first reports described a decrease in milk production of 10-20% and partial
anorexia, followed by clinical signs of reduced rumination, low rise of
temperature of short duration, weakness and stiff gait. In addition, prominent
serous to purulent nasal discharge, excessive salivation, and nasal and lip
redness with scaling and tongue swelling. Cynosis and erosions were
observed, and petechiae on the tips of the lingual and buccal papillae were
similar to those reported in several hemorrhagic syndromes of ruminants(1)
(Figure 1). Ocular lesions appeared in some animals as epiphora, conjunctival
hyperemia and pulpebral edema (Figure 2). Also evident in some animals
were a stiff gait, muscular tremors of the appendages, and in some animals,
recumbency. Several animals were seen with red to purple discoloration of
the udder and hoof edema with ecchymotic hemorrhages. Not all the above
mentioned clinical signs were seen on the same farm.
Over the following weeks, the disease outbreaks extended northwards and
southwards in the Jordan Valley into the Upper Galilee and the Dead Sea
area, while at the beginning of October the disease spread westward to dairy
farms in the Jezreel Valley and the Golan heights. Several epidemic foci
appeared in the Mediterranean Coastal Plain. A total of 105 cattle herds were
involved, 80 of these were dairy cattle, 21 beef cattle and 4 feedlots. Morbidity
rate within a herd was from 5% to 80% of the milking cows with variable
involvement of replacement heifers. The mortality rate was very low, and the
duration of the disease in affected animals was reported to range from 3 to 30
days. There were no reports of a distinctive parallel disease syndrome in
sheep or goats in these areas.
A tentative diagnosis was made of Bovine Ephemeral Fever (BEF), an
arboviral disease that appeared in 1999, 2000, 2001 and 2004 at the same
season and in the same geographical regions (2-5). The clinical signs,
however, in this syndrome, were different and resembled more the
descriptions of the bluetongue (BT) outbreaks in cattle that were reported in
August 2006 from Europe (6, 7). The observed lesions were not typical of
BEF, although a few BEF-PCR positive reactions were obtained (H.Y.,
personal communication). The differential diagnosis also took BT into
consideration, which exhibited some of the same clinical signs, but there was
no ovine involvement, a finding which led us to consider Enzootic
Hemorrhagic Disease Virus (EHDV) as a possible etiology.
Laboratory investigations: the first samples were tested for BEF and BT by
PCR and for virus isolation in embryonated chicken eggs. Since EHD was
never seen in Israel nor in the region, no diagnostic procedures were readily
available, and therefore, samples were sent to the BT reference laboratory at
Pirbright, UK.
Of a total of 31 samples submitted, 11 were confirmed positive for EHD virus
type 7 by PCR while all samples were BTV negative. These results were from
15 farms of which 10 were positive for EHDV, and in addition the results were
confirmed also by the detection of specific antibodies to EHDV by ELISA.
During the summer of 2006, an EHD disease was reported from Morocco and
a similar disease picture was reported from Jordan (M. Haimovitch, CVO personal communication). Hemorrhagic diseases caused by orbiviruses are
seasonal since their vector might be some blood sucking insects, as is the
case of BTV which is transported in our region by Culicoides imicola.
Nevertheless, the source and the vector of the EHDV in this outbreak are still
unknown.
Several small scale serological surveys carried out in past years to assess
observations by bovine clinicians about the probable appearance of sporadic
cases of hemorrhagic syndrome, apparently caused by Ibaraki virus were
inconclusive (Yeruham I, personal communication).
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Acknowledgment: The authors thanks Dr. Carrie Batten and Prof. Philip
Mellor, the Arbovirology Reference Laboratory, IAH, Pirbright, UK for the
identification of EHDV-7 and to the Hahaklait Organization for the collection of
epidemiological data.