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Sörgel, Stephanie Christina (2008): Beteiligung von Neospora caninum bei Rinderaborten in Nordbayern. Dissertation, LMU München: Tierärztliche Fakultät



Abstract Participation of Neospora caninum in abortions in cattle populations in Northern Bavaria Stated aim of this study was to investigate the incidence and the potential importance of Neospora caninum as a cause of abortion in cattle populations in Northern Bavaria. For this purpose the available diagnostic methods of the LGL in Erlangen were compared with each other relating to their efficiency. Aim was to find out which method or which combination of methods is most useful in the routine diagnosis. To serve this purpose, all abortion cases which were sent in for analysis to the LGL Erlangen (232 cases) within a year (2005-2006) were tested with different direct and indirect methods. Direct diagnosis of the infection was determined by histopathology, immunohistochemistry and PCR (polymerase chain reaction). ELISA (Enzyme Linked ImmunoSorbent Assay) and Western Blot were used for indirect analysis. 23 of the 232 cases were considered to be infected by at least one of the diagnostic techniques used. That implies that Neospora caninum is involved in 10% of abortions in Northern Bavaria. It’s impossible to prove beyond doubt if Neospora caninum is the main cause of abortions or an innovator for further infections. Suspicious cases could be identified by routine histopathology because of characteristic lesions – particularly in brain and heart. Typical histological lesions consisted overbalancing in multifocal nonsuppurative necrotizing encephalitis and non-purulent myocarditis. Most of these cases were confirmed by immunohistochemical staining with using a polyclonal antibody. Frequently low numbers of disease agents necessitate more (up to 4) immunohistochemical runs in some cases to verify the agent. Especially in cases of bold autolysis or mummified fetuses histology was applicable only with restrictons, Immunohistochemistry not at all. PCR is able to detect DNA of the parasit in these cases. Altogether the PCR got the most positive results. In cause of this three different techniques (conventionell PCR, Real Time SYBR Green, Real Time TaqMan) could adduce approximately same results. The Real Time TaqMan Technique gained slightly advantage over the two other methods. High costs and difficulties to take positive results are detriments of the PCR-method. There is no qualified statement about the importance of Neospora caninum as a cause of abortion, using the PCR method only. Therefore the PCR method should be combined with one additionally morphological method. Serological tests of Neospora caninum intrinsic antibodies in fetal fluids proved not to be very useful. Fetuses in early pregnancy develop partly no specific antibodies against Neospora caninum so that these cases were seronegative in spite of showing typical morphological lesions. Compared with this, 4 seropositive cases did not show any histopathological alterations. A final interpretation of such cases is impossible. Summarising this study confirms the importance of Neospora caninum as a cause of abortion in Northern Bavaria and underlines the need to use different diagnostic techniques to increase the chance to detect the infection in aborted fetuses. The best combination is histopathology with PCR. After a screening with histopathology, suspicious fetal tissues should be verified by PCR. Furthermore the PCR has got the highest sensitivity of all used methods. It is able to detect also cases without lesions although inspite of presenting the parasit. PCR was confirmed to be the best tool for the diagnosis of Neospora caninum in aborted fetuses.