©1996-2008 All Rights Reserved. Online Journal of Veterinary Research. You may not store these pages in any form except for your own personal use. All other usage or distribution is illegal under international copyright treaties. Permission to use any of these pages in any other way besides the before mentioned must be gained in writing from the publisher. This article is exclusively copyrighted in its entirety to OJVR publications. This article may be copied once but may not be, reproduced or re-transmitted without the express permission of the editors. Linking: To link to this page or any pages linking to this page you must link directly to this page only here rather than put up your own page.
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Title: Seroepidemiological study of Neospora
caninum in dairy cattle in Shiraz, southern Iran
Author:
Maryam Ansari-Lari * a,
Sara Ahmadnia Motlaghb, Marjan Moravvejib, Somayye Bahramib, Arsalan Hosseinib
ID: 29635-2011
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4.REPORT: This is an interesting survey of the
potential effects of canine populations on dairy cattle. A large representative
cohort was used and extensive history is supplied. The zoonosis
would be of interest to many world agricultural organizations for comparison
purposes and disease prevention. The abstract, introduction are well written
and relevant suggest minor changes only. The findings justify the conclusion
that is not an important reproduction problem for dairy herds in that region. The
last sentence regarding hidden dogs etc needs to be changed. Accept with minor
modifications
Abstract
This
study was performed to determine the prevalence of antibodies to Neospora caninum in
dairy cattle herds in Shiraz, Fars province, southern Iran. Related risk
factors for N. caninum infection as well as
association of N. caninum seropositivity
with abortion in the study herds were also investigated. A total of 32 herds
were selected from dairy herds in the region and in each herd, blood samples
were collected from nearly 10% of the herd population. Overall, 169 serum
samples were obtained and detection of antibodies to N. caninum
was undertaken using a commercial ELISA test. Data regarding to the history of
recent abortion, keeping dogs on the farm, history of repeated abortion and
accessibility of dogs or wild carnivores to feed stuff or aborted materials
were obtained by questionnaire. Individual cow- and herd-level prevalence was
58 (95% CI: 50-66%) and 78% (95% CI: 63-93%), respectively. Thirty percent of
the study herds had history of recent abortion and 8.7% of them had history of
recurrent abortion. No association was observed between serologic status for N.
caninum and abortion or recurrent abortion. No
significant association was observed between keeping dogs on the farm and
serologic status for N. caninum. The association
between abortion and accessibility of wild carnivores to aborted materials was
significant (P=0.006). Our results indicated that seroprevalence
of N. caninum in our study herds is relatively high.
However, further epidemiological studies are needed to evaluate the definite
role of the infection in the region.
Keywords:
abortion, Iran, Neospora caninum,
risk factors, seroprevalence.
Introduction
Neospora
caninum is an apicomplexan
parasite and obligate intracellular parasite of animals with a wide host range
(Dubey, 2003). It was first recognized in 1984 in
dogs in Norway and subsequently has emerged as a serious disease of cattle and
dogs worldwide (Dubey et al. 2007). Neospora caninum is now regarded
as a major cause of bovine abortion with negative economic and reproductive
impacts in the cattle industry (Dubey and Lindsay,
1996; Dubey, 1999). The economic impacts of infection
with N. caninum in cattle herds include costs
associated with abortion (Anderson et al. 1991; Hernandez et al. 2002),
increased number of culled cows (Thurmond and Hietala,
1996) and decreased milk production (Thurmond and Hietala,
1997; Hernandez et al. 2001).
In
the N. caninum life cycle, dogs (McAllister et al.
1998) and coyotes (Gondim et al. 2004) are both
definitive hosts; cattle and other mammals are natural intermediate hosts (Dubey et al. 2007).
Seroprevalence of N. caninum in dogs, dairy
cattle, beef cattle and other domestic animals have been determined in many
countries (Dubey and Lindsay, 1996; Dubey, 2003). In Iran, there are several reports from
various parts of the country about the seroprevalence
of N. caninum antibodies in dairy and beef cattle
farms (Sadrebazzaz et al. 2004; Razmi
et al. 2006; Nourollahi Fard
et al. 2008; Youssefi et al. 2009). Seroprevalence in individual cattle ranging from 12.6% in
Kerman, south east of Iran (Nourollahi Fard et al. 2008) to 46% in Mashhad, north east of the
country (Razmi et al. 2006) has been reported. However, to the best knowledge of the
authors, there is no report from Fars province concerning the seroepidemiologic status of dairy cattle regarding to the
N. caninum infection. Therefore, this study was
performed to determine the prevalence of antibodies to N. caninum
in dairy herds in Shiraz, southern Iran. Related risk factors for N. caninum infection as well as association of N. caninum seropositivity with
abortion in the herds were also investigated.
Materials
and methods
This
cross sectional study was conducted in Shiraz, the capital of Fars province,
southern Iran during May to July 2009. Target population consisted of all dairy
herds which were registered by Veterinary Organization of the province for
brucellosis and tuberculosis control program. Overall, 32 herds were selected
and in each herd, blood samples were collected from nearly 10% of the
population. A total of 169 serum samples were obtained and sera were stored at
-20ºC until use.
For
serological examination and detection of antibodies to N. caninum,
a commercial enzyme linked immunosorbent assay
(ELISA) kit (Svanova Biotech AB, Sweden) was used.
All sera were diluted 1:100 in PBS solution and according to the instruction of
the manufacturer, samples with an absorbance value
above the cut-off level of 0.20 were considered as positive.
A
brief questionnaire was prepared and data regarding to the history of recent
abortion in the herd, keeping dogs on the farm, history of repeated abortion
and accessibility of dogs or wild carnivores to feed stuff or aborted materials
were obtained by interview with the farmers.
For
statistical analysis, herd- and cow-level prevalence with 95% confidence
interval (CI) was calculated. A herd with at least one individual positive
sample was considered as positive. Association of suggested risk factors with
N. caninum seroprevalence
as well as association of N. caninum seropositivity with abortion in the herds was investigated
using chi-square or Fisher's exact analysis. In all analysis, a P-value less
than 0.05 was considered as statistically significant.
Results
From
169 serum samples, a total of 98 samples (58%, 95% CI: 50-66%) were positive
for antibody to N. caninum by ELISA. Twenty five out
of 32 herds were positive with herd-level prevalence of 78% (95% CI: 63-93%).
Dogs were kept in 55% of the herds. Nearly 87.5% of herds with dogs were
positive for N. caninum in comparison with 69.2% of
herds without dogs. However, the difference was not significant (P=0.23). More
than 80% of farmers who keep dogs in the farm reported that their dogs were in
closed situation and were not free in the farm; also more than 88% of dogs had
not accessibility to feed stuff in the farm (Table 1).
Thirty percent of the study herds had history
of recent abortion and 8.7% of them had history of recurrent abortion. No
association was observed between serologic status for N. caninum
and history of abortion (P=0.53) or recurrent abortion in the herds (P=0.49).
Nearly 19% of farmers reported the possible accessibility of wild carnivores to
aborted materials, and 53% refused to answer to this question. No association
was observed between this variable and serologic status for N. caninum (Table 1).
No
significant association was observed between keeping dogs on the farm and
abortion problem. However, the association between abortion and accessibility
of wild carnivores to aborted materials was highly significant (P=0.006); all
herds (100%) with this risk factor had history of abortion compared with 20% of
the herds without this risk factor. No significant relationship was observed
between keeping dogs on the farm and accessibility of wild carnivores to
aborted materials (P=0.14).
Discussion
The
serologic prevalences of N.
caninum in different
countries indicate that there are considerable differences among countries,
within countries and between regions (Dubey et al.
2007). Based on the results of the present study, the individual cow-level and
herd-level prevalence of N. caninum in dairy cattle
in Shiraz, southern Iran was 58 and 78%, respectively. Results of the present
study indicate that the individual- and herd-level seroprevalence
for N. caninum in Shiraz is relatively high. Neospora caninum has been
detected in dairy herds in some other parts of the country. Razmi
et al. (2006) reported a cow-level seroprevalence of
46% in 337 dairy cattle from 30 dairy herds in Mashhad, north eastern of the
country; all selected dairy herds were positive in their study. The individual
cow-level and herd-level prevalences in the present
study are comparable with seroprevalences in Mashhad,
but is relatively higher than prevalences reported
from other parts of the country (Nourollahi Fard et al. 2008; Youssefi et al.
2009). As suggested by Dubey et al., the observed
discrepancies may be due to differences in serologic techniques, study design
and sample size in different regions (Dubey et al.
2007).
Many
studies have assessed risk factors for infection by N. caninum
on the herd level. Presence and number of farm dogs have been associated with seropositivity in dairy herds in several epidemiologic
studies (Corbellini et al. 2006; Pare´ et al. 1998; Schares et al. 2004), but no association has been detected
in some other studies (Aguiar et al. 2006). The
results of the present work did not show association for keeping dogs on the
farm with N. caninum seroprevalence.
Lack of association in this study may be related to the keeping conditions of
dogs on the farms; most of the dogs were in closed status with no accessibility
to feed stuff or aborted materials.
Studies
on the association between N. caninum prevalence and
abortion are numerous with conflicting results (Dubey
et al. 2007). While many studies revealed a positive association between N. caninum and abortion on herd level (Hobson et al. 2005;
Bartels et al. 1999; Sager et al. 2001), not all herds with a high seroprevalence suffer from N. caninum-associated
abortion (Schares et al. 2004; Jensen et al. 1999; Dubey et al. 2007). It has been suggested that recent
exposure to N. caninum infection as evidenced by seroconversion, does not necessarily result in increased
abortion; furthermore this supports the hypothesis that some factors, other
than the infection, may influence the abortion risk (Dubey
et al. 2007).
The
results showed that the risk of abortion was increased in farms with
possibility of wild carnivores to feed on aborted materials. Although there was
no significant relationship between presence and absence of dogs with
accessibility of wild carnivores to aborted materials, the possibility of
confounding effect of keeping dogs could not be eliminated due to the missing
data for the latter variable.
Conclusion
The
results indicated that seroprevalence of N. caninum in our studied herds is relatively high, but at
least based on the present results it seems that this situation. From the
epidemiologic point of view, retrospective assessment generally allows the
identification of putative risk or protective factors, but conclusive data can
be obtained only by prospective cohort or experimental studies (Dubey et al. 2007). Therefore, further epidemiological
studies are needed to evaluate the definite role of the infection in the
region.
Acknowledgment
This
study was supported by a grant from Shiraz University research council. The
authors wish to thanks staff of Shiraz Veterinary Organization for valuable
help in making this study possible.
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Table
1. Distribution
of risk factors for Neospora caninum
antibodies in study dairy herds from Shiraz, southern Iran (2009)
Risk
factors Neospora
positive herds Neospora
negative herds
N % N %
History
of recent abortion
No 17 85 3 15
Yes
6 75 2 25
History
of recurrent abortion
No 21 80.8 5 19.2
Yes
2 100 0 0
Keeping
dogs on the farm
No 9 69.2 4 30.8
Yes
14 87.5 2 12.5
Keeping
status of dogs a
Closed
11 84.6 2 15.4
Free
3 100 0 0
Accessibility
of dogs to feed stuff a
No 11 78.6 3 21.4
Yes
2 100 0 0
Accessibility
of wild carnivores to aborted materials
No 4 80 1 20
Yes
4 66.7 2 33.3
Refuse
to answer 15 88.2 2 11.7
a: only for herds with keeping dogs
©1996-20011All
Rights Reserved.
Online Journal of Veterinary Research. You may
not store these pages in any form except for your own personal use. All other
usage or distribution is illegal under international copyright treaties.
Permission to use any of these pages in any other way besides the before mentioned must be gained in writing from the
publisher. This article is exclusively copyrighted in its entirety to OJVR
publications. This article may be copied once but may not be, reproduced or re-transmitted without the express permission of the
editors. Linking: To link to this page or any pages linking to this page you
must link directly to this page only here rather than put up your own page