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Epidemiology of Neospora caninum infection in cattle

evaluation of diagnostic tests and herd studies

Frössling, Jenny (2004). Epidemiology of Neospora caninum infection in cattle. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae. Veterinaria, 1401-6257 ; 175
ISBN 91-576-6670-9
[Doctoral thesis]

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The intracellular parasite Neospora caninum is an important cause of abortion in cattle. The aims of this thesis were to characterize N. caninum dynamics in infected herds and to validate diagnostic tests for individual- and herd-level testing. The thesis is based on four separate studies. To validate an N. caninum iscom ELISA, sera from 244 Swedish dairy cattle were analysed. These were also analysed by an IFAT, which was considered an imperfect reference test. Estimates of sensitivity and specificity at different cut-offs were therefore obtained using a latent class method (Gibbs sampling). The best over all cut-off was 0.20 where sensitivity and specificity were 99% and 96%, respectively. Optical densities ≤0.15 and ≥0.55 were suggested limits to rule out and rule in infection. A three-year study of an American beef herd demonstrated how the avidity iscom ELISA is used to describe the duration of infection. The avidity pattern gradually changed as the peak shifted towards a higher avidity. It was concluded that postnatal infection was first frequent but decreased during the following years. The high avidity values at the end of the study confirmed that the majority of cows were chronically infected and that their calves were congenitally infected. Both increased and decreased prevalences of N. caninum were seen when 15 Swedish dairy herds were investigated in a longitudinal study. These changes were not related to the prevalence that each herd had when first sampled. Avidity measurements and investigation of serological status of related animals revealed that most seropositive individuals were chronically infected and that vertical transmission was the dominant transmission route. Test results from three groups of herds (total n=244) were used in an evaluation of the iscom ELISA when used to analyse bulk milk. Accuracy was estimated for different cut-off levels by using a standard cross-tabulation technique and also, in order to adjust for milk yield covariates, a logistic regression model. There was a relationship between within-herd prevalences and bulk milk optical densities. Herds with test results >0.20 are likely to be infected and herds with results <0.05 will have a within-herd prevalence of at most 10-15%.

Authors/Creators:Frössling, Jenny
Title:Epidemiology of Neospora caninum infection in cattle
Subtitle:evaluation of diagnostic tests and herd studies
Series Name/Journal:Acta Universitatis Agriculturae Sueciae. Veterinaria
Year of publishing :December 2004
Number of Pages:41
ALLI. Frössling J, Bonnett B, Lindberg A & Björkman C. 2003. Validation of a Neospora caninum iscom ELISA without a gold standard. Preventive Veterinary Medicine 57, 141-153. II. Björkman C, McAllister M, Frössling J, Näslund K, Leung F & Uggla A. 2003. Application of the Neospora caninum IgG avidity ELISA in assessment of reproductive losses after an outbreak of neosporosis in a herd of beef cattle. Journal of Veterinary Diagnostic Investigation 15, 3-7. III. Frössling J, Uggla A & Björkman C. Prevalence and transmission of Neospora caninum within infected Swedish dairy herds. Manuscript. IV. Frössling J, Lindberg A & Björkman C. Evaluation of an iscom ELISA used for detection of antibodies to Neospora caninum in bulk milk. Manuscript submitted for publication.
Place of Publication:Uppsala
ISBN for printed version:91-576-6670-9
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:L Animal production > L73 Animal diseases
Subjects:Not in use, please see Agris categories
Agrovoc terms:dairy cattle, beef cattle, neospora caninum, analytical methods, milk yield, infection, elisa
Keywords:bovine, sensitivity, specificity, vertical, horizontal, transmission, prevalence, gold standard, latent class, Gibbs sampling, cut-off, genealogic trees, avidity, milk yield
Permanent URL:
ID Code:707
Department:(VH) > Institutionen för idisslarmedicin och epidemiologi ( 970401-040630)
Deposited By: Jenny Frössling
Deposited On:01 Dec 2004 00:00
Metadata Last Modified:02 Dec 2014 10:06

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