Neospora caninum DNA distribution in tissues of gerbils as experimental models of chronic neosporosis

G Toscan,G.R Pereira,P.B.D Gonçalves,A.C Vargas,A.S Cezar,P Bräunig,F.S.F Vogel,L.A Sangioni

doi:10.1590/1678-4162-11603

Abstract

ABSTRACT Neospora caninum is the main etiologic agent of neosporosis in domestic animals and its pathogenesis comprises two characteristic phases: acute and chronic. Rodents are used as experimental models to mimic acute and chronic bovine neosporosis. In this study, we inoculated a total of 27 female gerbils, with different doses of N. caninum tachyzoites aiming to induce chronic disease. DNA was extracted from different organs of each animal after spontaneous death or euthanasia. Encephalic tissues were submitted to a highly sensitive real time PCR aiming to detect chronically infected animals. All the other samples were submitted to standard PCR. A total of 11 gerbils died due to acute neosporosis, as confirmed by N. caninum DNA detection in organs. 5x103 tachyzoites/mL of N. caninum was the dosage of antigen that can induce chronic infection in gerbils. In the encephalon sections of some animals that showed clinical signs of persistent infection, we found 70% positive for the anterior encephalon section, suggesting this area as preferential for cyst formation. Therefore, we determined the doses of tachyzoites that cause acute or chronic infection and detection of positive tissues, preferably, systemic organs during acute and encephalon in chronic phases.

Highlights

N. caninum infection is a major cause of abortion in cattle and can cause myositis, encephalitis and several reproductive disorders in many species of mammals (Dubey and Schares, 2011)
The parasite may be found in a form of rapid multiplication and cell invasion named tachyzoite and tends to evade immune response of the host forming tissue cysts containing bradyzoites in the chronic phase
Tachyzoites are the predominant form in acute neosporosis and tissue cysts containing bradyzoites characterize the chronic disease (Dubey and Lindsay, 1996)

Summary

INTRODUCTION

N. caninum infection is a major cause of abortion in cattle and can cause myositis, encephalitis and several reproductive disorders in many species of mammals (Dubey and Schares, 2011). The parasite may be found in a form of rapid multiplication and cell invasion named tachyzoite and tends to evade immune response of the host forming tissue cysts containing bradyzoites in the chronic phase. Tachyzoites are the predominant form in acute neosporosis and tissue cysts containing bradyzoites characterize the chronic disease (Dubey and Lindsay, 1996). The clinical consequences of these two phases differ significantly (Aguado-Martínez et al, 2009) and this is fundamental to the determination of replication sites of N. caninum and its location in animal tissue. This study used gerbils as experimental model, aiming to determine the tachyzoites inoculation dosage and presence of N. caninum DNA in different tissues from acute and chronic infected animals, enabling the use of conventional PCR and real time PCR (qPCR). Techniques for diagnosis and to establish which sites are preferable for cysts localization of the parasite in these animals, especially in the central nervous system (CNS)

MATERIAL AND METHODS

RESULTS AND DISCUSSION

CONCLUSION