Abstract
Cattle besnoitiosis due to Besnoitia besnoiti is spreading across Europe and is responsible for severe economic losses in newly infected herds. Experimentally speaking, rabbits have been found to be susceptible to this parasite. The adaptation of B. besnoiti to rabbits may offer a new, easier and cheaper model of investigation for this disease. This study compared the virulence between tachyzoites and bradyzoites of B. besnoiti in rabbits. Eighteen New Zealand rabbits were allocated into three groups of six animals each. The rabbits from the control (group C), “tachyzoite” (group T) and “bradyzoite” (group B) groups were subcutaneously injected in the right flank with 66 μg of ovalbumin, 6.106 tachyzoites (125th passage on Vero cells) and 6.106 bradyzoites (collected from a natural infected cow) of B. besnoiti, respectively. Clinical follow-up and blood sampling for serological survey and qPCR were performed during 10 weeks until euthanasia. Molecular and immunohistochemistry examination was achieved on 25 samples of tissue per rabbit. Seroconversion occurred in group T without any clinical signs. Rabbits of group B exhibited a febrile condition (temperature above 40 °C from day 8 to day 11 following injection) with positive qPCR in blood. Cysts of B. besnoiti were found on skin samples and organs of rabbits from group B in tissue explored with threshold cycle (Ct) values below 30. These results suggest a higher virulence of bradyzoites in rabbits than Vero cell-cultivated tachyzoites. The proposed model could be used to assess the in vivo effectiveness of vaccine or drugs against cattle besnoitiosis.
Highlights
Cattle besnoitiosis is caused by a protozoan parasite Besnoitia besnoiti, a cyst-forming Apicomplexa intimately related to Toxoplasma gondii and Neospora caninum (Ellis et al 2000)
The first aim of this study was to reproduce the clinical course of bovine besnoitiosis in rabbit by subcutaneous injection of B. besnoiti
The first inoculations of rabbits by B. besnoiti tachyzoites were performed by Pols (1954a) in South Africa
Summary
Cattle besnoitiosis is caused by a protozoan parasite Besnoitia besnoiti, a cyst-forming Apicomplexa intimately related to Toxoplasma gondii and Neospora caninum (Ellis et al 2000). This disease is widespread in Africa, Asia and the southwest of Europe (Jacquiet et al 2010). Considered as an emerging disease in cattle according to the European Food Safety Authority (EFSA 2010), recent outbreaks have been reported in Germany (Mehlhorn et al 2009), Italy (Mutinelli et al 2011; Gentile et al 2012), Switzerland (Lesser et al 2012), Croatia (Cortes et al 2014) and in Hungary (Hornok et al 2014). The classical course of the disease in cattle is divided into three successive clinical phases (Jacquiet et al 2010).
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