Acta Parasitologica, Vol. 51, No. 1, 2006, 15-25 Andrew Hemphill and Bruno Gottstein* - Neospora caninum and neosporosis - recent achievements in host and parasite cell biology and treatment
Institute of Parasitology, Vetsuisse Faculty, University of Bern, CH-3012 Bern, Switzerland
*Corresponding author: bruno.gottstein@ipa.unibe.ch
ABSTRACT
Neospora caninum is an apicomplexan parasite, which owes its importance to the fact that it represents the major infectious
cause of bovine abortion worldwide. Its life cycle is comprised of three distinct stages: Tachyzoites, representing the proliferative
and disease-causing stage, bradyzoites, representing a slowly replicating, tissue cyst-forming stage, and sporozoites, which
represent the end product of a sexual process taking place within the intestinal tissue of the final canine host. Tachyzoites are
capable of infecting a large variety of host cells in vitro and in vivo, while bradyzoites have been found mainly within the central
nervous system. In order to survive, proliferate, and proceed in its life cycle, N. caninum has evolved some amazing features.
First, the parasite profits immensely from its ability to interact with, and invade, a large number of host cell types.
Secondly, N. caninum exploits its capability to respond to alterations in living conditions by converting into another stage
(tachyzoite-to-bradyzoite or vice versa). Thirdly, this parasite has evolved mechanisms that modulate its host cells according
to its own requirements, and these must, especially in the case of the bradyzoite stage, involve mechanisms that ensure long term
survival of not only the parasite but also of the host cell. These three key events (host cell invasion - stage conversion - host cell
modulation) represent potential targets for intervention. In order to elucidate the molecular and cellular bases of these important
features of N. caninum, cell culture-based approaches and laboratory animal models are extensively exploited. In this
review, we will summarize the present knowledge and achievements related to host cell and parasite cell biology.
KEY WORDS: Neospora caninum, host cell invasion, cell surface receptors, vaccine, host cell modulation, stage conversion, chemotherapy