Neosporosis is one of the most frequently diagnosed causes of abortion in cattle worldwide. Epidemiological studies in Belgium and the United Kingdom revealed that approximately 12 % of abortions in cattle are caused by N. caninum. In cattle herds, N. caninum infection can lead to persistently increased abortion rates or outbreaks of abortions.
Dogs are the definitive hosts of the protozoal pathogen N. caninum. However, they can also act as intermediate hosts like cattle and develop N. caninum infection. As definitive hosts, dogs may excrete oocysts in their faeces which are able to survive in the environment for some time. Oocyst-contaminated food or drinking water can cause infections in cattle.
Projects on neosporosis of cattle carried out at the Institute of Epidemiology of the FLI mainly focus on the development, evaluation and standardization of methods for detection of N. caninum infections which can then be used in epidemiological studies
Assessment of Neospora caninum seroprevalence in cattle holdings
To estimate the Neospora caninum seroprevalence in dairy and beef cattle, a cross sectional study was conducted in the German state of Rhineland-Palatinate in collaboration with the Landesuntersuchungsamt Rheinland-Pfalz and the Landeskontrollverband Rheinland-Pfalz e.V.. Within an EU funded project, this study started in 2003 and ended 2004. Out of the farms organized in a dairy farmers organisation (Landeskontrollverband Rheinland-Pfalz e.V.) (n = 2082) 100 dairy herds were randomly selected for participating in the study. Individual milk samples from 4343 cows were taken. The milk samples were examined by an ELISA previously modified and evaluated for the examination of milk samples. The total prevalence in the milk-ELISA was 4.0% (172/4343). The intra-herd prevalence varied from 0% to 42.86%. 35% (35/100) of dairy herds had an intra-herd prevalence of >5% whereas in 15% (15/100) of the herds it was >10%.
In the context of serological examinations on bovine herpes virus type 1 and bovine leucosis virus serum sets of serum samples collected from 106 beef herds were haphazardly selected from those submitted to the investigation centre of state (Landesuntersuchungsamt Rheinland-Pfalz). The total prevalence in the serum-ELISA was 4.9% (131/2680). The intra-herd prevalence varied from 0% to 54.5%. 37% (39/106) of dairy herds had an intra-herd prevalence of >5% whereas in 21% (22/106) of the herds it was ≥10%.
The proportion of dairy or beef herds with intra-herd-prevalences of >5% was at 54.6% or 50.0% in the province Rheinhessen/Pfalz, respectively, at 39.0% or 41.8% in the province Koblenz, respectively, and at 27.1% or 24.3% in the province Trier, respectively (Blumröder et al., 2006).
Detection of Neospora caninum oocysts in naturally infected dogs
Among 11586 canine faecal samples submitted between March 2001 and February 2004 to two private veterinary labs localized in Baden-Württemberg (Tierärztliches Labor Freiburg, Vet-Med-Labor), 31 (0.27%) samples were found to contain oocysts morphologically similar to those of Hammondia heydorni and N. caninum (Fig. 2). To determine the species, oocysts isolated from 14 dogs were further examined at FLI by gerbil inoculation. Five induced in gerbils a specific antibody response against antigens of N. caninum NC-1 tachyzoites, i.e. these isolates contained N. caninum. The remaining isolates induced neither a specific antibody response against N. caninum nor against Toxoplasma gondii (Schares et al., 2005).