Prevalence of antibodies to Toxoplasma gondii in horses in the province of Kars, Turkey

Vet. Med. – Czech, 49, 2004 (1): 9–13 Original Paper
Prevalence of antibodies to Toxoplasma gondii
in horses in the province of Kars, Turkey
A. A???1, C. B????2, M.O. A?????1, Y. G????1, M. K???1, S. K????2
1Department of Parasitology, Faculty of Veterinary Medicine, Kafkas University, Kars, Turkey
2Parasitology Laboratory, Refik Saydam Hygiene Centre, Sihhiye, Ankara, Turkey
ABSTRACT: This study investigates the seroprevalence of Toxoplasma gondii in horses from seven villages in the prov-
ince of Kars in north-eastern Turkey. A total of 189 serum samples from clinically healthy, local crossbred horses were
tested for anti-T. gondii antibodies using the Sabin-Feldman dye test. Antibodies to T. gondii were found in 39 (20.6%)
horses, with specific titres of 1 : 16 (27), 1 : 64 (11) and 1 : 256 (1). The 95% confidence interval for the population
proportion ranged from 13.3 to 27.9%. The number of seropositive horses in Yucelen village (40%) was considerably
higher than in other villages, whereas in the villages of Caglayan (8%) and Cerme (10.5%) the seroprevalence was
lower than elsewhere. However, the differences in seroprevalence between the seven villages were not statistically
significant (P > 0.05). In contrast, the overall seroprevalence in the province of Kars was significantly higher than
that reported previously in studies carried out on army and private horse stud farms elsewhere in Turkey (P < 0.05).
The relevance of these findings to the epizootiology of toxoplasmosis in Kars and Turkey is discussed.
Keywords: Toxoplasma gondii; horse; seroprevalence; dye test; Turkey
Toxoplasma gondii is an intracellular protozoan the first study in 1970 by Weilland and Dalchow,
parasite capable of infecting a wide variety of no report has been published on toxoplasmosis
tissues in a number of mammals and birds. The in horses kept by peasant farmers in Turkey. The
parasite has a worldwide distribution and is of province of Kars is located in north-eastern Turkey
both medical and veterinary importance. Although at an altitude of approximately 2 000 metres and is
symptoms such as fever, ataxia, retinal degenera-
relatively underdeveloped when compared to the
tion and severe encephalomyelitis may be observed other parts of the country. The region has the larg-
occasionally (McDonald and Cleany, 1970; Beech, est horse population in Turkey and horses are still
1974; Cusick et al., 1974), in general T. gondii infec-
widely used for short distance transportation, ag-
tions in horses progress subclinically and, therefore, riculture and in traditional sports and ceremonies.
diagnosis relies largely on serological techniques to Therefore the area was felt to be an appropriate
detect the parasite-specific antibodies.
choice for our study which aims to establish the
The seroprevalence of toxoplasmosis in horses seroprevalence of toxoplasmosis in horses main-
varies with country, ranging from 1% to 74% (Zardi tained under extensive farming conditions and to
et al., 1968; Eugster and Joyce, 1976; Tizard et al., discuss its epizootiological relevance.
1978; Beyer and Shevhunova, 1986; Uggla et al., 1990;
Hejlicek and Literak, 1994). Toxoplasmosis in horses
was reported for the first time in Turkey by Weilland MATERIAL AND METHODS
and Dalchow (1970), with a seroprevalence of 14.3%
in 154 horses from different regions. Subsequently, Study area and the design of the study
seroprevalence ranging from 1.9% to 8.3% was re-
ported in studies carried out at army stud farms
Turkey is divided into administrative provinces
or specialist horse farms using the Sabin-Feldman which generally bear the name of their central city.
dye test (SFDT) (Inci et al., 1996; Zeybek et al., 1998; The central city and its associated provincial towns
Babur et al., 1998; Aktas et al., 1999). However, since are each directly responsible for the administration
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Original Paper Vet. Med. – Czech, 49, 2004 (1): 9–13
Vet. Med. – Czech, 49, 2004 (1): 9–13 Original Paper
of a number of villages in their respective vicini-
ples by centrifugation at 4 000 rpm for 10 minutes,
ties. Kars province in the north east of Turkey is and stored at –20°C. At the Refik Saydam Hygiene
the major animal (mainly ca?le) breeding area of Centre, Ankara, the serum samples were inactivated
the country and has the largest horse population. A at 56°C for 30 minutes, then tested for anti-T. gondii
recent programme for the control and eradication antibodies in fourfold dilutions (1 : 16; 1 : 64; 1 : 256;
of Glanders infection recorded an overall popula-
1 : 1 024), using the standard Sabin-Feldman dye
tion of approximately 32 000 horses in the province test as routinely performed according to the modi-
(personal communication, Governmental Animal fied method of Feldman and Lamb (1966) in the
Health Unit of Kars Province). In this study, an toxoplasmosis laboratory of the Centre.
estimate of the seroprevalence of T. gondii is made
for the population of approximately 7 000 horses
in 62 villages spread within the 1 400 km2 area di-
Statistical analysis
rectly administered by the city of Kars. Seven vil-
lages (10%), at points north, south, east and west
Seroprevalence was expressed as the percentage
of the city, were selected to carry out the study and of animals tested positive and the 95% confidence
were visited between February and April, 2001. A interval (CI) for one-stage cluster sampling was cal-
one-stage cluster sampling method was applied ac-
culated according to Thrusfield (1995). Statistical
cording to Thrusfield (1995). Each village was con-
analysis was performed according to Petrie
sidered to be a cluster and an a?empt was made to and Watson (1999) and Petrie and Sabin (2000).
sample all the horses in each cluster, resulting in a Differences in seroprevalence between the clusters
total of 189 horses sampled. This preliminary study were analysed using the Chi-squared test (for more
is assumed to be representative of the rest of the than two independent categories). The overall se-
province because the animal management practices roprevalence found in this study was compared by
of farmers in the region are very similar.
Chi-squared test (for two independent groups) with
each of the various figures reported previously for
horses elsewhere in Turkey (Weilland and Dalchow,
Collection of samples and serological
1970; Inci et al., 1996; Zeybek et al., 1998; Babur et
testing
al., 1998; Aktas et al., 1999).
Ten ml blood samples were taken from the jugular
vein of horses into evacuated tubes and transported RESULTS
to the Parasitology Laboratory of the Faculty of
Veterinary Medicine, Ka?as University, Kars.
Table 1 summarises the results of the study. Serum
Serum was removed from the clo?ed blood sam-
antibodies to T. gondii were found in 39 out of the
Table 1. The prevalence of serum antibodies to T. gondii in horses of Kars province
Number of
Number of posi-
Antibody titres*
Villages
serum samples
tive samples*
1/16
1/64
1/256
Bayraktar
40
10 (25%)
9 (22.5%)
1 (2.5%)
0
Caglayan
25
2 (8%)
2 (8%)
0
0
Cerme
19
2 (10.5%)
2 (10.5%)
0
0
Dikme
31
7 (17.5%)
5 (16%)
2 (6.4%)
0
Maksutcuk
17
4 (23.5%)
0
3 (17.6%)
1 (5.9%)
Sogutlu
32
4 (12.5%)
3 (9.4%)
1 (3.1%)
0
Yucelen
25
10 (40%)
6 (24%)
4 (16%)
0
Total
189
39 (20.6%)
27 (14.3%)
11 (5.8%)
1 (0.5%)
*per cent positive
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Original Paper Vet. Med. – Czech, 49, 2004 (1): 9–13
Vet. Med. – Czech, 49, 2004 (1): 9–13 Original Paper
189 horses tested. The overall seroprevalence was at starting dilution 1 : 16 to avoid the risk of overes-
20.6% with a 95% CI ranging from 13.3 to 27.9%. timating the rate of prevalence of the infection and
Antibodies to T. gondii were found in all 7 villages to enable us to make a direct comparison with other
sampled. Antibody titres were found in 27 horses studies performed in horses in Turkey where the
at a 1 : 16 dilution, in 11 horses at a 1 : 64 dilution same test and the same cut off titre were applied. In
and in 1 horse at a dilution of 1 : 256. The highest Turkey, using the SFDT, seroprevalence was found
seroprevalence was observed in Yucelen village to be 1.9% in 103 horses at Gemlik Army Stud (Inci et
(40%), while the lowest seropositivity was found al., 1996), 8.3% in 60 horses at the serum production
in Caglayan (8%) and Cerme villages (10.5%). unit of the Refik Saydam Hygiene Centre, Ankara
Although the prevalence rate differed greatly be-
(Babur et al., 1997), 2% in 50 horses slaughtered to
tween the clusters (i.e. villages), statistical evalua-
feed carnivorous animals in Ankara Zoo (Babur et
tion of the data produced no significant differences al., 1998), 8.2% in 194 horses sampled from stud
(P > 0.05). The overall seroprevalence found in this and horse farms in different parts of the country
study differed significantly from that reported previ-
(Zeybek et al., 1998), and 6.4% in 124 horses at the
ously for army and specialist horse stud farms else-
Government Horse Breeding Enterprise in Malatya
where in Turkey (P < 0.05), but not from that found (Aktas et al., 1999). When the prevalence rate found
in 1970 in the only other report to date on horses kept for Kars (20.6% with a 95% CI ranging from 13.3
by peasant farmers in the country (P > 0.05).
to 27.9%) is compared statistically with each of
the results cited above for elsewhere in Turkey, it
emerges as significantly higher (P-values ranging
DISCUSSION
from 0.05 to 0.001). The reason for this difference
may be that in the previous studies, the serum sam-
Toxoplasma gondii causes subclinical infections in ples were obtained from the horses of army and
horses. Therefore, the diagnosis of the infection is state studs or from specialist horse farms where
performed using various serological tests to detect good animal management practice is applied and it
T. gondii antibodies. While a number of serologi-
may therefore be assumed that measures are taken
cal tests to detect antibodies to T. gondii have been to control access to the premises by cats, the defini-
thoroughly studied in various hosts, in horses tive host of the parasite, thus limiting the likelihood
none of the tests has been optimised or validated of infection. In contrast, the serum samples in our
to date and the test of preference has not been de-
study were obtained directly from horses kept by
termined yet (Dubey and Bea?ie, 1988). Although peasant farmers under very different conditions. In
the requirement for the use of live parasites means particular, village farmers in Kars and the surround-
that the SFDT is not commonly used, it remains ing provinces keep semi-wild cats for the purpose
the gold standard in many hosts and we therefore of controlling the mouse population. These cats
selected it for our study. Using the test, we found have free access both to stables and pastures, thus
that the overall seroprevalence of toxoplasmosis in increasing the likelihood of infection. Furthermore,
horses in the province of Kars was 20.6%. Although in the only other study to date on the prevalence
a direct comparison with the results published in of toxoplasmosis in horses kept under similar
horses in other countries is not possible because conditions in Turkey, a rate of 14.3% was reported
of the variety of serological tests employed and (Weilland and Dalchow, 1970), which does not dif-
the lack of correlation between them (Dubey et al., fer significantly from our result (P > 0.05), again
1999), nonetheless when these figures, which range indicating that the animal management conditions
from 1% to 74%, are considered (Zardi et al., 1968; may be associated with the rate of prevalence.
Uggla et al., 1990; Tenter et al., 2000), it emerges
The horse is not only an important working ani-
that the prevalence rate of toxoplasmosis in Kars mal in Kars province but also it is held in people’s
province is higher than elsewhere with the excep-
high regard. Nonetheless, the high altitude of the
tions of Nigeria (37.1%) (Aganga et al., 1983) and area, the relative poverty of the inhabitants and the
Italy (74%) (Zardi et al., 1968).
fact that the consumption of horsemeat is prohib-
Although viable T. gondii cysts were reported ited by law and by religious belief result in any old
in some experimentally infected horses at dye test and unwanted horses either being culled before the
titres of 1 : 2 and 1 : 8 (Al-Khalidi and Dubey, 1979; onset of the long, hard winter to avoid the expense
Al-Khalidi et al., 1980), we preferred to test our sera of feeding them, and being fed to village cats and
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Original Paper Vet. Med. – Czech, 49, 2004 (1): 9–13
Vet. Med. – Czech, 49, 2004 (1): 9–13 Original Paper
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Received: 03–06–18
Accepted a?er corrections: 04–01–08
Corresponding Author
Dr. Atila Akca, University of Ka?as, Faculty of Veterinary Medicine, Department of Parasitology,
36040 Kars, Turkey
Tel. +90 474 242 6801, fax +90 474 242 6839, e-mail: atilaakca@hotmail.com
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