How to cite this article: Vet. Res. (2009) 40:49
DOI: 10.1051/vetres/2009032

Experimental infection with a low virulence isolate of Neospora caninum at 70 days gestation in cattle did not result in foetopathy

Silvia Rojo-Montejo, Esther Collantes-Fernández, Javier Blanco-Murcia, Antonio Rodríguez-Bertos, Verónica Risco-Castillo and Luis Miguel Ortega-Mora

SALUVET, Animal Health Department, Faculty of Veterinary Sciences, Complutense University of Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain

Received 27 February 2009; accepted 3 June 2009; published online 6 June 2009

Abstract - The Nc-Spain 1H isolate of Neospora caninum, which was newly obtained from the brain of a congenitally asymptomatic infected calf, demonstrated a reduced in vitro tachyzoite yield and viability rate, as well as low virulence in mouse models. The objective of the present study was to determine the ability of this isolate to induce foetal death in a pregnant bovine model. For this purpose, 13 naïve pregnant heifers were divided into three groups and were experimentally challenged with either 10⁷ tachyzoites of Nc-1 (group 1, n = 5), Nc-Spain 1H (group 2, n = 5) isolates or phosphate-buffered saline (group 3, n = 3) intravenously at 70 days of gestation. After inoculation, pregnancy was monitored and dams were sacrificed when foetal death was detected. The remaining animals were slaughtered at 45 days post-infection. Maternal and foetal samples were collected for examination by histology and parasite DNA detection. Parasitaemia, specific anti- N. caninum IgG and interferon responses were also studied. At 3–4 weeks after infection, foetal death was detected in 3 out of 5 Nc-1-infected dams. However, no evidence of foetal death was observed in either Nc-Spain 1H-infected or control groups during the period studied. The most severe histopathological lesions were observed in the placenta and foetal organs from Nc-1-infected cattle that exhibited foetal death. It was in these animals that N. caninum DNA was more frequently detected. Parasitaemia was observed in all Nc-1-infected dams and in only 3 out of 5 Nc-Spain 1H-infected animals. The magnitude of the immune response was significantly higher in the Nc-1-inoculated group than in the group inoculated with the Nc-Spain 1H isolate. These data reveal the reduced virulence of the Nc-Spain 1H isolate in cattle.

Key words: Neospora caninum / low virulence isolate / cattle / foetopathy / Nc-Spain 1H

Corresponding author: luis.ortega@vet.ucm.es

© INRA, EDP Sciences 2009