Primary lung neoplasms are infrequent in veterinary medicine, particularly in large animals. The most frequently affected species are dogs and cats. These neoplasias are usually malignant and the adenocarcinoma type is the most frequent. This paper describes a case of pulmonary adenocarcinoma in a mare, including its pathological and immunohistochemical features. The animal had natural death and was submitted for necropsy. Diffuse jaundice, splenomegaly due to red pulp hyperplasia, pulmonary edema and congestion were observed. Cytological evaluation of the spleen revealed intracytoplasmatic structures in erythrocytes, compatible with Babesia sp. Histopathology of the lung revealed a neoplastic proliferation of epithelial cells, forming acinar and tubular structures supported by a fibrovascular stroma. Immunohistochemistry of such lesions was positive for cytokeratin and napsin A, negative for vimentin and thyroid transcription factor 1, corroborating the diagnosis of adenocarcinoma. Lung carcinomas in equines are described in animals ranging from four to 23 years old, without breed or sex predisposition. Clinical signs, when present, are related to the compromise of respiratory function, which was not observed in the present case. Pulmonary neoplasms must be considered among the diagnostics of chronic respiratory diseases. Histopathological and immunohistochemistry exams are highly valuable for classification of primary lung neoplasms.

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Lawsonia intracellularis is a bacterium already described in several species and most prevalent in pigs, in which it causes enteric problems. Horses can also be affected, developing a disease known as equine proliferative enteropathy, which results from the proliferation of intestinal crypt cells in response to infection by the bacterium. Despite the existence of reports of the disease in several countries, including Brazil, there are still no reports of the disease or epidemiological studies of its occurrence in symptomatic or asymptomatic horses in the state of Paraná. Thus, the present study was conducted to examine the occurrence of L. intracellularis in asymptomatic horses raised in the west, northwest and north regions of Paraná by means of serological testing and the real-time polymerase chain reaction (qPCR) technique. In the serological approach, the immunoperoxidase monolayer assay (IPMA) technique was employed. Feces were processed and subjected to qPCR. In total, samples were collected from 162 animals from 20 farms. Of these, 9/162 (5.55%) showed specific antibodies against L. intracellularis. Real-time PCR, on the other hand, identified 7/162 (4.32%) fecal samples positive for the presence of the bacterium. When the techniques were compared, none of the samples was positive by both, demonstrating that, for a better diagnosis, they must be performed together. In contrast to most reports in horses, the present study describes higher serological and molecular occurrence in animals older than two years. These results are of great epidemiological relevance, as they indicate that the bacterium is present in the sampled regions of the state of Paraná. Therefore, the disease must be included in the differential diagnosis of diseases with similar clinical manifestations.