The application of immunological, molecular and epidemiological approaches to the study of Neosporosis in cattle

Hall, CA

The application of immunological, molecular and epidemiological approaches to the study of Neosporosis in cattle

Hall, CA

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Publication Type:: Thesis
Issue Date:: 2006

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Field	Value	Language
dc.contributor.author	Hall, CA
dc.date.accessioned	2011-07-12T01:43:56Z
dc.date.accessioned	2012-12-15T03:53:37Z
dc.date.available	2011-07-12T01:43:56Z
dc.date.available	2012-12-15T03:53:37Z
dc.date.issued	2006
dc.identifier.uri	http://hdl.handle.net/10453/20381
dc.description	University of Technology, Sydney. Faculty of Science.
dc.description.abstract	A prospective study was undertaken on a 260-head dairy herd in NSW, Australia to determine the modes of transmission, prevalence, effect on abortion and reproduction parameters and the impact on milk production of Neospora caninum. A test-and-cull method of control was also evaluated. The possible infectivity of milk from N. caninum infected cows was also investigated using a mouse model. As ELISAs form an important part of diagnosing N. caninum infection, studies were undertaken to evaluate two serum and one milk ELISA. Analysis was performed for each of the ELISAs to determine cut-off thresholds, Se and Sp. The milk ELISA was subsequently used to determine the overall prevalence of N. caninum in NSW dairy cows. In the prospective study, 11.4% of the herd’s cattle were seropositive to N. caninum by ELISA and the dominant route of transmission was vertical as the majority of the infected cattle were related and only a few seropositive cattle were born from seronegative dams (i.e. reflecting postnatal transmission). As 90% of offspring born from seropositive cows were also seropositive this suggests a high vertical transmission rate. Neospora caninum was found to be a major cause of abortion as cows seropositive to N. caninum had a 13-fold higher risk of abortion then seronegative cattle. Early foetal loss was also predicted to be associated with N. caninum infection as seropositive cows required a significantly greater number of inseminations and took longer to conceive than seronegative cattle. BVDV and IBR alone were not associated with causing abortion in this herd. This is the first report of an effective control strategy for N. caninum by either culling seropositives or not breeding from seropositive cows. This method was effective in reducing the number of infected cattle and was feasible due to the low prevalence of N. caninum on the farm and thus did not place too high a financial burden on the farmer. Neospora caninum DNA was also detected by PCR on milk samples from seropositive cows. This is the first Australian report demonstrating N. caninum DNA in milk. Of the serum ELISA evaluated, one was determined to have high Se and Sp at the cut-off recommended by the manufacturer while the other required modification of the cut-off value to gain the same high Se and Sp. After choosing the most suitable milk dilution, the milk ELISA was determined to have high Se and Sp of 97%. Using this ELISA the prevalence of N. caninum in NSW dairy cattle was determined to be 21.1%. Neospora caninum was found to be a significant cause of abortion and also foetal loss in the study herd and was vertically transmitted efficiently. Control efforts using a test-and– cull approach were successful without placing economic hardship on the farmer. The evaluation of several ELISAs was useful as these can be used in diagnosing infection. In particularly the milk ELISA will now make sampling easier so enabling whole herd sampling by the farmer. This ELISA may be of particular use in test-and- cull programs or in epidemiological studies. The concept of detecting N. caninum DNA in milk could be of great importance to the dairy industry as it suggests a new route of infection. Although milk extracts from seropositive cows were not infective to SCID mice in this study this should be investigated further.	en
dc.format	Thesis (PhD)	en
dc.language.iso	en	en
dc.relation	https://opus.lib.uts.edu.au/bitstream/10453/20381/2/02Whole.pdf
dc.relation.replaces	http://hdl.handle.net/2100/1257
dc.rights	info:eu-repo/semantics/openAccess
dc.rights	The author owns the copyright in this thesis including all reproduction and reuse rights for the work. The work may not be altered without the permission of the copyright owner. Attribution is essential when quoting or paraphrasing from this thesis.
dc.rights	au.edu.uts.lib/ppc
dc.subject	Dairy cattle.	en
dc.subject	Neosporosis.	en
dc.title	The application of immunological, molecular and epidemiological approaches to the study of Neosporosis in cattle	en
dc.type	Thesis
utslib.copyright.status	open_access

Abstract:

A prospective study was undertaken on a 260-head dairy herd in NSW, Australia to determine the modes of transmission, prevalence, effect on abortion and reproduction parameters and the impact on milk production of Neospora caninum. A test-and-cull method of control was also evaluated. The possible infectivity of milk from N. caninum infected cows was also investigated using a mouse model. As ELISAs form an important part of diagnosing N. caninum infection, studies were undertaken to evaluate two serum and one milk ELISA. Analysis was performed for each of the ELISAs to determine cut-off thresholds, Se and Sp. The milk ELISA was subsequently used to determine the overall prevalence of N. caninum in NSW dairy cows. In the prospective study, 11.4% of the herd’s cattle were seropositive to N. caninum by ELISA and the dominant route of transmission was vertical as the majority of the infected cattle were related and only a few seropositive cattle were born from seronegative dams (i.e. reflecting postnatal transmission). As 90% of offspring born from seropositive cows were also seropositive this suggests a high vertical transmission rate. Neospora caninum was found to be a major cause of abortion as cows seropositive to N. caninum had a 13-fold higher risk of abortion then seronegative cattle. Early foetal loss was also predicted to be associated with N. caninum infection as seropositive cows required a significantly greater number of inseminations and took longer to conceive than seronegative cattle. BVDV and IBR alone were not associated with causing abortion in this herd. This is the first report of an effective control strategy for N. caninum by either culling seropositives or not breeding from seropositive cows. This method was effective in reducing the number of infected cattle and was feasible due to the low prevalence of N. caninum on the farm and thus did not place too high a financial burden on the farmer. Neospora caninum DNA was also detected by PCR on milk samples from seropositive cows. This is the first Australian report demonstrating N. caninum DNA in milk. Of the serum ELISA evaluated, one was determined to have high Se and Sp at the cut-off recommended by the manufacturer while the other required modification of the cut-off value to gain the same high Se and Sp. After choosing the most suitable milk dilution, the milk ELISA was determined to have high Se and Sp of 97%. Using this ELISA the prevalence of N. caninum in NSW dairy cattle was determined to be 21.1%. Neospora caninum was found to be a significant cause of abortion and also foetal loss in the study herd and was vertically transmitted efficiently. Control efforts using a test-and– cull approach were successful without placing economic hardship on the farmer. The evaluation of several ELISAs was useful as these can be used in diagnosing infection. In particularly the milk ELISA will now make sampling easier so enabling whole herd sampling by the farmer. This ELISA may be of particular use in test-and- cull programs or in epidemiological studies. The concept of detecting N. caninum DNA in milk could be of great importance to the dairy industry as it suggests a new route of infection. Although milk extracts from seropositive cows were not infective to SCID mice in this study this should be investigated further.

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