NAVLE（北美执业兽医考题）Day 681

A 3-year-old male neutered Labrador retriever from the Ohio river valley basin is presented with chronic large bowel diarrhea and signs of respiratory disease (cough, fever).
A lymph node smear shows round to ovoid (1-4 micrometers) encapsulated structures inside macrophages and giant cells. The organisms have thin cell walls, with thin clear zone between cell wall and cytoplasm. What is the diagnosis？
一只来自俄亥俄河流区域的3岁雄性已去势的拉布拉多猎犬患有慢性大肠性腹泻和呼吸道疾病（咳嗽，发烧）的迹象。淋巴结涂片显示巨噬细胞内有圆形到卵圆形（1-4微米）的包囊结构。 这个生物体具有一层薄的细胞壁，细胞壁和细胞质之间还有一部分薄的透明区域。 诊断是什么？