Putative equine neorickettsiosis in a mare from Southern Brazil
Marutani, Victor Hugo BrunaldiHeadley, Selwyn ArlingtonBracarense, Ana Paula Frederico Rodrigues Loureiro
Background: This report describes the occurrence of equine neorickettsiosis (EN) in the northern region of Paraná,southern Brazil. EN is a non-contagious infectious disease caused by the Gram-negative bacterium, Neorickettsia risticii.Equine neorickettsiosis was previously known as Potomac horse fever and monocytic ehrlichiosis. The disease occurspredominantly in the USA and Canada; data relative to EN in Brazil is scarce. The aim of this study was to report the firstcase of putative EN in the state of Paraná due to a combination of IHC and molecular testing.Case: A 2-year-old Quarter Horse was referred to a Veterinary Hospital with episodes of abdominal discomfort, fever,anorexia, tachycardia, and tachypnea. The animal reportedly demonstrated episodes of blackened and fetid diarrhea afterthe ingestion of hay. A treatment was established upon arrival at the veterinary hospital, but the mare died after 12 hoursof monitoring. An autopsy examination performed soon after death revealed severe hyperemia of the mucosa of the cecum and colon, with multifocal cecal erosions and ulcerations. The principal histological lesion observed was necrotizingenterocolitis. Additional significant histopathologic lesions included widespread lymphoid depletion affecting the spleen,tonsils, and lymph nodes. An IHC assay designed to identify the antigens of N. helminthoeca (NH) in formalin fixed paraffin embedded (FFPE) tissues, identified antigens of intralesional neorickettsial organisms within macrophages of themucosa of the colon. Additionally, a PCR assay designed to amplify the 16S rRNA gene of Neorickettsia, amplified thedesired amplicon, but sequencing was frustrating.Discussion: A putative diagnosis of equine neorickettsiosis was established due to the combination of epidemiologicalevidence, pathologic findings, immunohistochemical identification of intralesional antigens of neorickettsial agents, andamplification...(AU)
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