Beteiligung von Neospora caninum bei Rinderaborten in Nordbayern

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.