
Brucella canis in pit bull breed dogs/ Özavci et al. __________________________________________________________________________________
4 of 6
and transmission, as the potential for venereal contamination can 
continue for at least two more years in dogs known to be healthy [26].
A higher prevalence of B. canis has been reported in stray dogs in 
rural settings and on the streets. However, the prevalence of B. canis 
infection in shelter dogs was reported as 2.3%, with a seroprevalence 
of 17.8% [27]. The prevalence of B. canis seropositivity varies from 2 to 
30% in different countries [28]. Studies in Brazil have used serological 
surveys to identify cases of B. canis infection in dogs. Reports show 
that seropositivity in dogs can range from 0 to 54.8% [29]. A study 
in the United States found a seroprevalence of B. canis infection in 
dogs of 6.8%, with age, breed and breeding history being risk factors 
associated with the disease [30]. In Mississippi, a recent study found 
a 2.3% prevalence of B. canis infection in shelter dogs [27]. Dogs in 
Colombia had a seroprevalence of 1.96% for B. canis [31]. In Egypt, 
research showed an apparent prevalence of 3.8% and an actual 
prevalence of 13.2%, with stray dogs having a higher estimated true 
prevalence of 15% compared to owned dogs at 12.5% [32]. Positive 
B. canis antibodies were also found in studies conducted in Italy, 
where 25 out of 2328 sera were positive (1.1%), and Brazil, where 72 
out of 280 sera (25.7%) were positive results.
The prevalence of B. canis antibodies in dogs varies across different 
countries. In Canada, out of 33 sera tested, 60.6% were positive, 
with a range of 0.8 to 44.5%. In Argentina, 14.7% of 224 sera were 
positive, while in Japan and Korea, 2.5 and 39.1% of 485 and 463 
sera, respectively, were positive [33]. In Turkey, studies have shown 
seroprevalence in dogs ranging from 5.4% and 7.7% [34]. Positive B. 
canis antibodies were found in 7.7% of 362 sera by Oncel et al. [28], in 
5.4% of 111 sera by Yılmaz and Gümüşsoy [33], in 6.3% of 222 samples 
by Diker et al. [35], and in 6.7% of 134 sera by IstanBulluoğlu and Diker 
[36]. A study found that dogs fed with leftovers and poor–quality 
food had the highest prevalence of canine brucellosis (25%), while 
dogs fed with commercial and formulated quality dog food had lower 
prevalence values (0.19%) [37].
An epidemiological study of brucellosis among 415 domestic dogs 
in Being, China, between 2006 and 2007 reported a seroprevalence 
of 0.24%. Another study of domestic dogs in 2012–2013 reported an 
incidence rate of 47% [22]. Pit Bull dogs have been found to have a 
signicantly higher rate of seropositivity. In fact, it has been suggested 
that males are more likely to be seropositive for B. canis than females, 
while females may be more susceptible to seropositivity than males 
[30]. However, in the current study, all seropositive dogs were either 
neutered or spayed and the gender distribution was almost equal. 
Therefore, gender was not considered to be an important factor in 
the disaggregation of data. Due to transmission associated with 
reproduction, it is normal for B. canis seroprevalence to be reduced 
in neutered or spayed dogs. Also, when the results of the current study 
were compared with those of previous studies, a lower proportion of 
samples were found to be positive for B. canis antibodies. It was thought 
that the change in the number of positive samples might be due to the 
difference in the strains used to prepare the antigen.
The serological methods most commonly used to screen for B. canis 
infection are the rapid slide agglutination test, the 2–mercaptoethanol 
rapid slide agglutination test (2–ME RSAT), agar gel immunodiffusion 
and ELISA [24]. The 2–ME RSAT can detect antibodies to B. canis in 
serum samples from dogs [38]. However, this test has restrictions 
such as low specicity and sensitivity [5, 24]. The limited humoral 
response observed in dogs infected with B. canis may account for 
this reduced sensitivity of serological tests. This may be due to 
the intracellular nature of Brucella bacteria [39]. Also, treatment 
of serum with 2–mercaptoethanol increases the specicity of the 
test by destroying IgM pentamers, which can interfere with the 
evaluation of IgG, but does not completely eliminate false positives 
due to heterologous cross–reactions [24].
Molecular techniques are also often used to diagnose canine 
brucellosis [5, 39]. PCR is a rapid sensitive, and specic test that 
can be used on blood samples, semen samples from male dogs and 
vaginal uid samples from female dogs. PCR can detect inactive 
bacteria and is unaffected by other bacterial contaminants [40, 41]. 
However, several factors, including the presence of inhibitors, the 
use of antibiotics and blood collection techniques involving heparin, 
can reduce the sensitivity of PCR results [29]. The present study 
demonstrated that the detection rates of B. canis antibodies in pit 
Bull blood samples ranged from 22.85 to 20% when assessed by 2–
ME RSAT and PCR, respectively. Notably, six sera (17.14%) that were 
initially positive by 2–ME RSAT were negative by PCR. In general, the 
use of the 2–ME RSAT test for the diagnosis of brucellosis–positive 
dogs increases the specicity of the test but may result in reduced 
sensitivity and an increased number of negative results that may still 
be present in the population [27]. The present diagnostic sensitivity 
of 2ME–RSAT (37.14%) was similar to that reported by Keid et al. [39] 
(31.76%) and Hensel et al. [24] (31.76–70%). When PCR was compared 
with the 2ME–RSAT serological test, Keid et al. [41] stated that PCR 
diagnostic sensitivity and specicity for the detection of B. canis DNA 
in dog blood was 100%. Sensitivity and specicity results for PCR 
and 2ME–RSAT are low due to the small number of dogs in our study. 
However, our research has shown that the combination of 2ME–RSAT 
and PCR as complementary diagnostic tools for canine brucellosis can 
signicantly increase diagnostic accuracy. This nding also highlights 
the potential to increase diagnostic accuracy through the synergistic 
use of these tests. The RSAT test has a high sensitivity, resulting 
in minimal false negative results. However, its lack of specicity is 
known to contribute to frequent false–positive results. The reduced 
humoral response observed in dogs infected with B. canis may offer 
an explanation for the reduced sensitivity of serological tests, given 
that Brucella are facultative intracellular organisms [39, 42].
Therefore, complementing the analysis with PCR testing is essential 
to achieve accurate results. Several factors could contribute to the 
discrepancy in test results, including possible infections at different 
stages in the animals, the presence of different immunoglobulins in the 
blood serum, or the occurrence of cross–reactions. Human infection with 
B. canis is rare and self–limiting, with only an estimated 1% of diagnosed 
cases of human brucellosis attributed to this agent [5]. Despite the 
relatively low prevalence of brucellosis, dog breeders and veterinarians 
must remain vigilant because of the associated public health risk.
CONCLUSIONS
This study concludes that the combination of the 2–ME RSAT test with 
PCR is recommended to achieve accurate results and avoid false–positive 
results in the serological diagnosis of B. canis infection in dogs. Although 
2–ME RSAT is a widely used diagnostic method for canine brucellosis, 
PCR–based assays offer higher sensitivity and specificity for the 
detection of B. canis. In addition, PCR–based assays have demonstrated 
good diagnostic performance for various sample types, making them a 
valuable tool for the early and accurate diagnosis of canine brucellosis. 
Further studies are needed to understand the prevalence and risk factors 
associated with B. canis infection in Pit Bull dogs.