Systemic Infection by Aspergillus flavus in a Mare.

Background: Aspergillus spp. are dimorphic fungus widely distributed in the environment, including in soil, dust and decaying vegetation. Clinical signs of aspergillosis in horses including rhinitis, pneumonia, guttural pouch mycosis, keratomycosis, endometritis, abortions and systemic involvement. In addition, horses with a history of enterocolitis may be predisposed to pulmonary or systemic mycotic infection. However, reports about systemic aspergillosis in horses are restricted to infections by A. fumigatus and A. niger. There have been no reports of systemic infection caused by A. flavus in horses or in other domestic species. Thus, the objective of this work was to describe the epidemiological, clinical and pathological aspects of systemic infection by Aspergillus flavus in a mare. Case: A 3-year-old pregnant mare of the Manga Larga, had signs of colic two days prior to admission after grazing in a landfill area to which it had free access. The owner observed remains of plastic bags in the stool. Clinically, there was dehydration, apathy, ocular mucosal congestion, oral cyanosis, reluctance to move, diarrhea, fever, drooling and tachypnea. Due to its clinical condition, the animal was referred to the surgical center for exploratory laparotomy, where compaction in the colon and cecum was verified. Enterotomy and enterolith removal were performed in the small colon region. The mare died after eight days of hospitalization, and necropsy was performed. Macroscopically disseminated lesions were observed in the small colon, stomach, kidneys, lungs, heart and brain. Fragments of tissues from organs in the abdominal and thoracic cavities, as well as from the central nervous system, were collected, fixed in 10% buffered formalin solution, and subsequently routinely processed and stained with hematoxylin and eosin and special histochemical stains to visualize the infectious agent and its morphological characteristics. Samples of lung lesions were submitted to microbiological culture for isolation. Fragments of fungal colonies were conserved in mineral oil for molecular analysis. Histologically, lesions showed acute, necrosuppurative colitis, gastritis, pneumonia, myocarditis, nephritis and meningoencephalitis, associated with vasculitis, thrombosis, infarction and intralesional hyphae that were morphologically compatible with Aspergillus spp. The species A. flavus was identified based on isolation and polymerase chain reaction analysis. Discussion: A diagnosis of systemic aspergillosis caused by Aspergillus flavus was determined by the microscopic examination of lesions associated with characteristic intralesional fungal hyphae and the isolation and identification of the fungal DNA by PCR. A pre-existing disease associated with debilitating factors, including the period of pregnancy, postpartum stress, internment, surgery and the intensive use of antimicrobials and corticosteroids, probably contributed to immunosuppression that favored the proliferation of the infectious agent. Grazing for a long period of time in a place with abundant decomposing organic matter, which is favorable to the proliferation of fungi of the genus Aspergillus, may have been a determining factor leading to the infection in the present case as the animal was likely exposed to an excessive number of spores. It is believed that the fungal microorganisms already present in the gastrointestinal tract invaded the surgery-induced lesions present in the mucosa of the small colon and later disseminated to various organs, including heart, lungs, stomach, kidneys and brain. Aspergillus flavus can cause enteric infection and hematogenous dissemination in horses, triggering lesions in the heart, lungs, stomach, kidneys and brain, which are characteristic of the systemic form of aspergillosis. [ABSTRACT FROM AUTHOR]