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Suggested Title:
Prevalence of caseous lymphadenitis in sheep in
Argentina (Patagonia).
Authors:
Estevao Belchior, Silvia
Graciela ; Abalos, María
Andrea; Mas, Mirta ; Clapera, Eduardo ; Gallardo, Adriana Alicia; Alvarez, Laura
Alejandra.
ID: 296125-2011
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4.REPORT: A large cohort has been used to determine
the prevalence of ovine caseous lymphadenitis in
southern Argentina. This is large sheep production region and the results which
rely on a very large sample of 1 million animals appear to be accurate. The
macroscopic and microscopic methods confirmed the presence of CLA from
carcass samples. The results should be of interest to the sheep and abbatoir industries. The survey would be of interest to
many world agricultural organizations for comparison purposes and disease
prevention. However, the paper is not
well written with numerous grammatical errors and these have been pinpointed in
the attached text below.. The abstract is quite
confusing and the authors have left out basic results (see alternative below),
The introduction is relevant with few minor changes required. Matwerials and
methods have grammar mistakes. The findings justify the conclusions. Accept with minor modifications as suggested
below.
Suggested
ABSTRACT
A total
of 1,023,793 Merino lambs and 196,737 adults (122,774 males and 73,963 females)
carcasses were examined for caseous lymphadenitis
(CLA). Lamb, ewe and ram carcasses were
examined visually and by palpation of
lymph nodes, lungs, liver and kidneys.
CLA was detected in 946 lambs (0.09%) and 19,798 adults (10.06%), with the
thoracic cavity being involved in most cases. The lymph nodes more frequently
affected were the pre-scapular, pre-femoral and supra-mammary and mediastinal lymph nodes. Visceral CLA was observed in 89%
of cases with abscesses in the lung and liver. There was no significant
increase in incidence during the study period.
INTRODUCTION
Sheep
production is an economically important activity in Argentina, mainly in the
Patagonian region. Sheep products such as wool, meat, hide and milk are
supplied to the domestic and foreign markets (www.sagpya.mecon.gov.ar, 2005).
However, infectious diseases are the major sources of morbidity and mortality
in sheep, leading to substantial economic losses. Among these, caseous lymphadenitis (CLA), also called boils, cheesy
gland or thin ewe syndrome, is a common cause of sheep condemnation at
slaughter, mainly affecting adults. The occurrence of CLA in sheep flocks may
be as high as 30%, with an average of about 10% among adult sheep culled at
abattoirs (Hollins 2008).
Corynebacterium pseudotuberculosis
is the causative agent of CLA. The purulent contents of ruptured lesions are an
important source of cross-infection between animals. The organism can be
transmitted by contamination of skin wounds or acquired by penetration of
intact skin and, probably, through mucous membranes of the digestive and
respiratory tracts (Severini and others 2003;
Fontaine and Baird 2008). In Argentina
there is very little epidemiological information on the prevalence of CLA,
despite its impact on economy and human health. The aim of this short
communications was to evaluate the occurrence of CLA and the distribution of
associated lesions in culled sheep from Argentine Patagonia, on the basis of
data collected from a sheep abattoir.
The
frequency of the typical lesions caused by C. pseudotuberculosis
was evaluated in the context of a survey carried out over the last few years in
a slaughterhouse processing Merino and Corriedale
sheep, located in Comodoro Rivadavia
City, province of Chubut, southern Patagonia, Argentina.
Suggested
MATERIALS and METHODS
Data
sampling was performed between January 2000 and April 2007. The study design
was non-experimental and cross-sectional. Animals
< 6 mth age were classified as lambs and those
over, as adult ewes or rams. Post-mortem inspection of animals was done
following national standard criteria (Res. 475/07 de Ministerio
de Economía y Producción de
la Nación, SAGPYA). This included visual examination,
palpation and incision of the main lymph nodes and other affected organs. Lymph
nodes, lungs and liver were removed and kept at -20ºC until further analysis.
Samples were cut with disinfected stainless steel knifes and contents were then
exposed and characterized. The same were examined macroscopically for
morphology, size, color and external/internal condition. Bacteriological
examinations were performed on nodule and abscess samples (Estevao
Belchior and others 2007).
A case of CLA was recorded when visual
inspection and palpation of lymph channels, organs and viscera showed
consistency, abnormal size, purulent abscesses or cheese like matter. Unaffected sheep did not show those
characteristics. Confirmation of CLA was verified by isolation of bacterial
cultures characterized by native strains of C. pseudotuberculosis
biovar ovis.
Univariate
and multivariate statistical analyses were used to analyze changes in the
variables of culled sheep; sheep affected by CLA, condemned carcasses and
condemned viscera over the study period. Statistical analyses were performed
using v. 15.0 Statistical Package for Social Sciences.
The
seasonal variation in parasite prevalence was investigated using Analysis of
Variance (ANOVA), Scheffe's test and Fisher's Least
Significant Difference (LSD) test. A p value of <0.05 or less was considered
statistically significant.
RESULTS
A total
of 1,023,793 merino lambs and 196,737 merino adults (122,774 males and 73,963
females) were examined. Caseous lymphadenitis cases
were detected in 946 lambs (0.09% of lambs examined) and in 19,798 adult sheep
(10.06% of adults examined). The characterization established the distinctive
features of the lesions of pseudotuberculosis in
sheep from the southern Patagonian region of Argentina. The samples sizes were between
2 and 15 centimeter of diameter. Macroscopic observations showed a fibrous
membrane enclosing necrotic tissue. Macroscopic observations showed a fibrous
membrane enclosing necrotic tissue.
The
lesions were classified into two types according to macroscopic characteristics
of its contents: nodules (87%) and abscesses (13%). The content of the nodules
were differentiated by the following features: 47% with caseous
content, 21% with calcified foci, and 19% with necrotic tissue arranged in
onion-like concentric layers. In pseudotuberculosos
abscesses, necrotic tissue showed consistency of green thick pus.
Bacteriological examination revealed the presence of C pseudotuberculosis
in the nodules and abscesses analyzed. The number of sheep having abscesses and
their location were as follows: 1,841 (93%) in carcasses, 16,752 (85%) in liver
and 18,209 (92%) in lungs.
Figure 1 shows the number of adult
sheep slaughtered and the percentages of occurrence (number of positive cases
per 100 cases examined) of CLA recorded from the harvest 1999-2000 to the
harvest 2006-2007.
Figure
1. Number of
sheep slaughtered and percentage of occurrence of CLA abscesses by harvest
period (from July 1 of a year to June 30 of the following year).
After post-mortem
veterinary inspection, half or quarter carcasses were condemned and sent to
digesters. The mean monthly weight of condemned meat was 196 kg and that of
condemned viscera was 208 kg. Figure 2 shows the mean monthly weights of meat
and viscera condemned and processed in digesters during the study period.
Figure
2. Distribution
of mean monthly weight of meat and viscera condemned and processed in digesters
during the study period.
There was
a positive association between the number of adult sheep slaughtered and the
number of adult sheep with CLA each year (p<0.001). The weight of condemned
meat was positively associated with the number of sheep exhibiting lesions
(p<0.001). The analysis revealed a significant increase in prevalence in summer
and autumn.
DISCUSSION
Published
data show that ovine pseudotuberculosis is prevalent
worldwide, and although it is accepted that CLA is present in the majority of
the sheep-rearing areas, variations in prevalence have been observed in different
geographic regions (Baird and Fontaine, 2009; Severini
et al., 2003). The present study revealed a CLA frequency of 10% in adult
sheep, with the thoracic cavity being involved in most cases.
No
significant increase was found in the incidence of the disease in the study
period. The lymph nodes more frequently affected were the superficial lymph
nodes (prescapular, prefermoral
and supramammary) and mediastinal
lymph nodes. The visceral form was observed in 89% of the cases and abscesses
occurred in lungs and liver. The predominance of visceral abscess is
significant by the serious systemic effects in sheep and associated with
significant economic losses by trimming and carcass rejection at abbatoir.
ACKNOWLEDGEMENTS
We
acknowledge the owner and the staff of the slaughterhouse.
REFERENCES
Baird, G.
J., Fontaine, M. C. (2007) Corynebacterium pseudotuberculosis and its Role in Ovine Caseus Lymphadenitis. Journal of Comparative Pathology 137,
179-210.
Estevao Belchior, S., Gallardo, A., Abalos,
A., Diaz, Y., Alvarez, L., Callejo, R., Prieto, M., Jodor, N., Jensen, O.
(2007) Diagnosis of caseous lymphadenitis in sheep
from Patagonia. Revista Argentina de Microbiología
39, 44-46.
Fontaine,
M.C., Baird, G.J. (2008) Caseous
lymphadenitis. Small Ruminant Research 76, 42–48.
Hollins, J.D. (2008) Boils – Caseous Lymphadenitis (CLA) In: Farm Management Handbook,
Falkland Islands Government, Department of Agriculture, Falkland Islands, pp.
1-3.
Severini, M., Ranucci, D., Miraglia, D., Cenci goga, B.T. (2003) Pseudotuberculosis
in sheep as a concern of veterinary public health.
Veterinary Research Communities 27, 315–318.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.
References
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D. M., Cavalcante, G. T., Rodrigues,
A. A. R., Labruna,
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L. M. A., Camargo, E. P. and Gennari,
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Amazon, Brazil, in association with some possible risk factors. Vet. Parasitol.
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Anderson,
M.L., Blanchard, P.C., Barr, B.C., Dubey, J.P.,
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Bartels,
C.J.M., Wouda, W. and Schukken,
Y.H. 1999. Risk factors for Neospora caninum-associated abortion storms in dairy herds in the
Netherlands (1995 to 1997). Theriogenology 52:
247–257.
Corbellini, L. G., Smith,
D.R., Pescador, C.A., Schmitz, M., Correa, A.,
Steffen, D.J. and Driemeier, D. 2006. Herd-level risk factors for Neospora caninum seroprevalence in dairy farms in southern Brazil. Prev.
Vet. Med. 74: 130–141.
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67: 1-59.
Dubey,
J.P. 1999. Recent advances in Neospora and neosporosis. Vet. Parasitol. 84: 349–67.
Dubey, J.P., Schares, G., Ortega-Mora, L.M. 2007. Epidemiology and
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and neosporosis in animals. Korean J. of Parasitol.
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D.E. 2004. Coyotes (Canis latrans)
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J. and Risco, C., Donovan, A. 2001. Association between exposure to Neospora caninum and milk production in dairy cows. J. of Am. Vet. Med. Assoc. 219: 632–635.
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J. C., Duffield, T. F., Kelton, D., Lissemore, K., Hietala, S. K.,
Leslie, K. E., McEwen, B. and Peregrine,
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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
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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