Fatal Cutaneous and Visceral Infection in a Rottweiler Dog Associated with a Sarcocystis-Like Protozoon

Abstract

A 10-month-old male Rottweiler dog from Ottawa, Illinois, had persistent diarrhea for 2 months. After the diarrhea stopped, the dog developed multiple cutaneous abscesses all over its body, particularly in the hind limbs. The limbs were swollen, hot, and painful. A skin biopsy was fixed in 10% formalin solution. The dog died, and the carcass was frozen until necropsy. No other history was available. Portions of liver, unspecified lymph node, lungs, kidney, and skin from the frozen-thawed carcass were fixed in 10% formalin solution. Paraffin-embedded sections of tissues were cut at 5 pm and stained with hematoxylin and eosin (HE). Paraffin-embedded sections from the biopsy specimens of skin were deparaffinized and reacted with Toxoplasma gondii antiserum and Neospora caninum antiserum with an avidinbiotin complex (ABC) immunohistochemical staining method? To further identify the protozoon, biopsy specimens of skin were deparaffinized and processed for transmission electronmicroscopy. Severe necrotizing fibrinosuppurative dermatitis was evident in the sections of skin (Figs. 1, 2). Numerous neutrophils, fewer eosinophils and macrophages, and abundant edema and fibrin expanded extensive areas of deep dermis and occasionally extended into superficial dermis and subcutaneous fat. Multifocal areas of dermal connective tissue and rare hair follicles were necrotic. Capillaries and venules were markedly congested. Many of them contained fibrin thrombi, and the walls of some were disrupted and infiltrated by neutrophils. Hemorrhage had occurred in some areas. A focally extensive area of epidermal necrosis and ulceration overlain by a fibrinohemorrhagic crust was present. A 1-cm-diameter focus of necrosis and fibrinosuppurative inflammation was present in the lung. Alveolar septa in this area were necrotic. Numerous neutrophils, fewer macrophages, and abundant fibrin filled alveoli and expanded re-