Clinical evolution of equine leishmaniasis with self-limiting cutaneous disease caused by Leishmania infantum in northeastern Brazil: A case report.

This study describes a case of a horse that was naturally infected by a parasite known as Leishmania infantum and experienced a self-limiting cutaneous disease. The results provide insights into the diagnostic and epidemiological aspects of equine leishmaniasis.

Clinical Presentation and Progress of the Disease

• The researchers investigated a case involving a four-year-old horse from the Pernambuco state, which was obtained at an auction. Upon arrival at its new home in the Bahia state in November 2019, the horse had several nodules under her skin on her head and neck.
• A few weeks later, these nodules became multiple and also appeared on both of the horse’s right limbs. Some of them were ulcerated while others were not.
• Additionally, blood tests indicated the horse was anemic and had heightened number of lymphocytes, monocytes, and plasma fibrinogen level, which is an inflammatory marker.

Diagnostic Findings and Treatment

• Upon inspecting a sample from the nodules, the researchers found signs of granulomatous dermatitis, an immune response to chronic inflammation. Macrophages – which are types of immune cells – that contained Leishmania amastigotes were identified.
• Using a polymerase chain reaction (PCR) method, the researchers found evidence of Leishmania in the skin lesions. However, it was not detected in either the horse’s blood or in samples from her spleen. Further molecular testing, involving restriction fragment length polymorphism (RFLP) and DNA sequencing, confirmed the presence of the L. infantum species of the parasite.
• Even without specific treatment for Leishmania, the horse’s condition gradually improved after applying a topical antiseptic and insect-repellent. At a 14-month follow-up, the horse’s condition had fully resolved.

Significance of the Study

• This case is the first documentation of a natural infection of L. infantum causing skin disease in a horse in an area where the parasite is endemic.
• The study underscores the necessity for further epidemiological studies and highlights the importance for clinicians to consider equine leishmaniasis in differential diagnosis.