Large Human Brucella melitensis Outbreak in Israel, 2014

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Israel Journal of Veterinary Medicine  Vol. 70 (4)  December 2015 63 Brucellosis Outbreak in Israel
Large Human Brucella melitensis Outbreak in Israel, 2014
Armon, L.,
Hadani, Y.,
Chechik, C.
and Bardenstein, S.
Kimron Veterinary Institute, Bet Dagan, Israel.
Veterinary Services, Israel.
Corresponding Author: Dr. Svetlana Bardenstein, Department of Bacteriology, Brucella OIE, FAO Reference laboratory, Kimron Veterinary Institute,
POB 12, Bet Dagan, 50250, Israel. Tel: +972-3-9681715. E-mail:
A case study is presented of a large Brucella melitensis outbreak in the North of Israel presumably due to the
consumption of infected goat cheese. Over a period of six months a total number of 41 isolates were tested
and all of them were confrmed to be B. melitensis biovar 1, feld strain, by standard bacteriological methods.
Fourteen goat herds in the region were tested for brucellosis of which 10 were found serologically positive
out of which B. melitensis was isolated from 5 herds. Four herds had B. melitensis biovar 1 and one herd B.
melitensis biovar 2. Te intra-herd prevalence of seropositive animals did not appear to be a factor determining
the number of sick family members. Additionally, the major route of infection in humans was found to be
the consumption of contaminated dairy products.
Keywords: Human brucellosis; Outbreak; Brucella melitensis, Goat cheese; Israel
Brucella melitensis, the cause of Malta fever, Mediterranean
fever, or undulant fever is a zoonotic disease endemic in many
areas of the world including Israel (1). It is mostly acquired by
consumption of contaminated unpasteurized dairy products
or by a close contact with infected animals.Te greatest risk
of Brucella melitensis transmission is considered to be associ-
ated with the products derived from sheep and goats (2). In
humans brucellosis causes non-specifc ‘fu-like symptoms
often together with joint pain, but may cause severe compli-
cations when treated inappropriately (3). Brucella melitensis is
intracellular gram-negative, facultative bacteria of the Brucella
species (4). In Israel Brucella melitensis may be present in
sheep, goats and humans. Sometimes it was also found in
cattle (5) and camels (6). Te control of brucellosis in Israel is
carried out by the Veterinary Services using Rev1 vaccination
of the young females and annual serological testing of unvac-
cinated males. In cases where human brucellosis is reported,
herds suspected to be the source of the disease are extensively
tested and sick and seropositive animals eradicated.
Tis report describes an outbreak of brucellosis caused
by Brucella melitensis in the North of Israel with a descrip-
tion of the epidemiological investigation and bacteriological
Here we describe a large human brucellosis outbreak due to
Brucella melitensis in a small town (about 15,000 residents)
at the north of Israel. Tis town is composed of a relatively
isolated population with close contacts between the families.
Many of the town’s people have sheep or goat herds as small
milk production units mainly for domestic usage. For many
years there have been infrequent cases of human brucellosis
(up to two cases per year), although occasionally some of
the herds were found to be serologically positive. In April
2014 a number of Brucella isolates from hospitalized pa-
tients from this town were sent to the Brucellosis Reference
Israel Journal of Veterinary Medicine  Vol. 70 (4)  December 2015 Armon, L. 64
Laboratory for confrmation. During a period of six months
a total number of 41 isolates were received. All of them were
confrmed to be B.melitensis biovar 1, feld strain, by standard
bacteriological methods (7).
It was suspected that the actual number of brucellosis
patients was probably higher than the number of submitted
isolates. Te disproportionate number of infected people
over a short time period suggested a single source of the
disease outbreak and therefore, an intensive epidemiologi-
cal investigation was initiated in order to determine the
source of the outbreak. All of the patients mentioned were
found to be purchasing goat cheese from a certain family’s
herd of goats. All of the goats in this herd together with
additional 13 herds were tested for brucellosis. As shown
in Table 1, out of the 14 herds, 10 were found serologically
positive using the agglutination (SAT) and complement
(CFT) tests. Out of the positive herds we were able to
isolate Brucella melitensis from 5 herds (using milk pools
of up to 5 serologically positive animals). Four herds had
B. melitensis biovar 1 and one herd B. melitensis biovar
2. All of the positive animals were slaughtered and the
Brucella infection in the herds was controlled by the “test
and slaughter” paradigm.
When analyzing brucellosis distribution between the pa-
tients, it was notable that most of them were not in a direct
contact with infected animals, but rather acquired the disease
via consumption of the contaminated goat cheese. Te fam-
ily with the highest number of infected family members (9
members) was in fact the distributor of the contaminated
cheese (herd number 5). Furthermore the intra-herd preva-
lence of seropositive animals did not appear to be a factor
determining the number of sick family members: i.e. herd
number 12 had an incidence of 39% of animals infected and
showed the same infection prevalence among goats as that
in herd 5 with 42% of goats infected without any human
isolates obtained from this family. Additionally, there did
not appear to be any age or gender specifc preference for
infection by B.melitensis.
In conclusion, we describe a large brucellosis outbreak
occurring in Israel in 2014. Tis outbreak is a typical example
of a brucellosis outbreak, apparently from a single source.
Our data suggests that in this case the highest risk factor
for brucellosis infection was consumption of contaminated
unpasteurized dairy products rather than direct contact with
infected animals due to the multiplicity character of such
Case Reports
Table 1: Infected herds and related human infections
Herd number Animal type
Total number of
Prevalence (%) Brucella isolation
Sick family
1 Goat 177 3 2 1
2 Sheep 177 13 7 Biovar 2 1
3 Goat 98 0 0 0
4 Goat 97 19 20 1
5 Goat 31 13 42 Biovar 1 9
6 Goat 22 4 18 Biovar 1 0
7 Sheep, goat 185 49 26 0
8 Goat 132 24 18 0
9 Goat 100 0 0 1
10 Goat 200 62 31 Biovar 1 0
11 Goat 79 6 8 1
12 Goat 122 47 39 Biovar 1 0
13 Goat 18 0 0 0
14 Goat 10 0 0 0
Israel Journal of Veterinary Medicine  Vol. 70 (4)  December 2015 65 Brucellosis Outbreak in Israel
an infection route, goat cheese being consumed by many
associated individuals.
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Case Reports

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