Immunohistochemical Study to DemonstrateSarcocystis Neuronain Equine Protozoal Myeloencephalitis

Abstract

Abstract. A 5-year (1985-1989) retrospective immunohistochemical study was conducted using an avidinbiotin complex (ABC) immunoperoxidase method to demonstrate Sarcocystis neurona in histologically suspect cases of equine protozoa1 myeloencephalitis (EPM). Primary antibodies against S. neurona and S. cruzi were utilized for the ABC technique. The findings were compared with those from cases in which the organisms were detected by examination of hematoxylin and eosin (HE)-stained neuronal sections. HE-stained sections detected the presence of the organisms in 20% of the suspect cases; whereas the ABC technique confirmed the presence of S. neurona in 51% and 67% of the cases by S. neurona and S. cruzi antibodies, respectively. A review of clinical case histories showed that 21/47 (45%) of the EPM horses with parasites in the tissue sections had prior treatment with antiprotozoal drugs and/or steroids. Using the test results of S. neurona and S. cruzi as a standard reference, HE test sensitivity based on examination of up to 30 neuronal sections per case was only 25%, and test specificity was 91%. Equine protozoal myeloencephalitis (EPM) is a progressive disease of horses affecting the central nervous system (CNS).1,2,4,6 The causative agent is a protozoan, Sarcocystis neurona.5 An antemortem diagnostic test for the disease is not yet available. Postmortem diagnosis is based on the presence of characteristic histopathologic lesions and on the identification of the etiological agent.2,9 However, the detection of the protozoan by histopathology is laborious and often unrewarding 1,9 In a recent retrospective investigation of horses necropsied at the Laboratory of Large Animal Pathology, New Bolton Center (NBC), Kennett Square, Pennsylvania, over 20% of the cases had neurologic disease.7 Of these neurologic cases, 34% were considered to have an infectious cause (protozoal, viral, fungal, or bacterial). Within this group, EPM was the most frequent etiologic diagnosis based on the presence of characteristic microscopic lesions.2,4,9 However, the etiologic agent, S. neurona, 5 was identified in only 14 of the 70 positive cases of EPM. 7In the present study, we report of the immunohistochemical findings on these 70 histologically suspect cases of EPM. Materials and methodsClinical case histories and necropsy reports of 70 cases with lesions histopathologically compatible with EPM that were diagnosed between 1985 and 1989 at the NBC were examined. These records showed that an average of approximately 30 neuronal hematoxylin and eosin (HE)-stained sections were examined per case. Two histologic sections with the presence of S. neurona (determined from the necropsy report) or, in cases where the organisms were not observed, 2 sections with the most severe and extensive morphologic lesions from each of the suspect EPM cases were selected for immunohistochemistry. Consecutive tissue sections from the selected paraffin blocks (2 per horse) were cut at 5 µm and stained by an avidin-biotin complex (ABC) immunoperoxidase method ...

Os parasitas de ovinos

“…Para aumentar a sensibilidade e especificidade do diagnóstico histológico, foram desenvolvidos métodos imunoistoquímicos (Uggla; Buxton, 1990;Hamir et al, 1993), porém, podem ocorrer reações cruzadas entre as várias espécies de Sarcocystis spp. (Burgess, et al, 1988;O'Donoghuee;Weyreter, 1984), ou ainda com outros protozoários como, Toxoplasma gondii e Neospora caninum (Tenter, 1995).…”

Characterization of monoclonal antibodies developed against Sarcocystis neurona

“…Individual zoites of these protozoal organisms cannot be distinguished based on light microscopy of infected tissues; therefore, immunohistochemistry is an important postmortem diagnostic test for identification of parasites associated with EPM (Granstrom et al 1991;Hamir et al 1993;Marsh et al 1996a, b). However, polyclonal antibodies may crossreact with closely related parasites, which has been shown for Sarcocystis cruzi antibodies and S. neurona merozoites (Hamir et al 1993). In order to better characterize S. neurona isolates, two different monoclonal antibodies (mAb) were developed against S. neurona.…”

Equine Protozoal Myeloencephalitis

“…In 2 reported series, organisms were seen in hematoxylin and eosin sections of CNS tissue in 10% to 36% of suspected cases. 23,65 Sensitivity was increased from 20% to 51% by immune staining with antibody against S neurona. 65 The likelihood of finding organisms is reduced by prior treatment with antiprotozoal drugs and may be increased by treatment with corticosteroids.…”