title: An explorative study to assess the efficacy of toltrazuril-sulfone (ponazuril) in calves experimentally infected with Neospora caninum.
abstract: BACKGROUND
  Neospora caninum is an important cause of infectious abortion and stillbirth in cattle world-wide. Infection is common and may frequently be passed from mother to calf (vertical transmission) with no signs of disease. Based on our previous observation that N. caninum-infection can be efficiently controlled with toltrazuril-sulfone (ponazuril) in experimentally infected mice, we addressed the question if efficacy could also be obtained in experimentally infected calves.
  
  
  METHODS
  The study included 19 calves and represents an initial explorative approach to document a basic effectiveness at first. Fifteen animals received each 2 x 10(8) N. caninum trophozoites, half of the dose being injected intravenously and the other half subcutaneously. Efficacy of treatment was assessed using molecular detection of parasite DNA with PCR and pathological alterations by immunohistochemistry in different organs of the animals. Assessment included also clinical, serological and pathophysiological parameters.
  
  
  RESULTS
  In those calves medicated with ponazuril (one, or six consecutive days, respectively, starting one day after infection), a complete abrogation of the parasite detectability was obtained in the brain and other organs, while 50% of non-treated calves became PCR-positive in brain and muscles. Clinically, ponazuril chemotherapy of infected calves--in comparison to non-treated infected animals--reduced symptoms (fever), but no differences were observed between treated and non-treated animals with regard to serum enzymes and metabolites. Efficacy of a six-day treatment was also reflected by significantly lower anti-Neospora antibody concentrations developed after infection, when compared to non-treated animals.
  
  
  CONCLUSIONS
  Based on our findings in this initially explorative approach that indicate a basic effectiveness of ponazuril against experimental N. caninum infection in calves, we plan to follow our chemotherapeutical intervention strategy to control bovine neosporosis with a subsequent more extensive field study with naturally infected calves.
authors.affiliation: Institute of Parasitology, University of Berne, Länggass-Strasse 122, CH-3012 Berne, Switzerland. bruno.gottstein@ipa.unibe.ch
authors.forename: Sandra
authors.initials: S
authors.lastname: Kritzner
authors.forename: Heinz
authors.initials: H
authors.lastname: Sager
authors.forename: Jürg
authors.initials: J
authors.lastname: Blum
authors.forename: Ralph
authors.initials: R
authors.lastname: Krebber
authors.forename: Gisela
authors.initials: G
authors.lastname: Greif
authors.forename: Bruno
authors.initials: B
authors.lastname: Gottstein