Clinical evolution of equine leishmaniasis in northeastern Brazil
Leishmania infantum infections have long been described in humans and dogs worldwide, but characterization of equine cases remains scarce. This study describes the clinical evolution of a natural L. infantum infection to contribute to the diagnostic knowledge and epidemiology of equine leishmaniasis (EL).
In Brazil, zoonotic leishmaniasis caused by Leishmania infantum is a major concern since human visceral leishmaniasis (HVL) and canine leishmaniasis (CanL) caused by this parasite may progress to severe systemic disease and death.
Dogs are considered the most important domestic reservoir due to their susceptibility to infection and extensive cutaneous parasitism if untreated. However, other animal species, such as horses that interact with humans or live in endemic areas, could be exposed to Leishmania transmission and may undergo active infection.
An auction-acquired four-year-old Mangalarga Marchador mare from Pernambuco state presented with a few subcutaneous nodules on the head and neck upon arrival at the purchaser's stud at Bahia state in November 2019. These nodules progressed to multiple ulcerated and non-ulcerated nodules and spread to both right limbs in seven weeks.
Hematology revealed anemia, lymphocytosis, monocytosis, and elevated plasma fibrinogen. Histopathology of the biopsied nodules identified a granulomatous dermatitis with macrophages containing Leishmania amastigotes.
PCR detected Leishmania in skin lesions, but not in blood or spleen aspirate samples; ITS1 PCR-RFLP and DNA sequencing confirmed L. infantum species. A topical antiseptic and insect-repellent therapy and a monthly follow-up were established.
All lesions improved progressively, without specific anti-Leishmania treatment, and 14 months later there was a consistent resolution.
In conclusion, this first description of EL by L. infantum in an endemic area is relevant to emphasize the need for epidemiological studies, and to enhance clinicians' awareness for differential diagnosis.
Flaviane Alves de Pinho, et al. “Clinical evolution of equine leishmaniasis with self-limiting cutaneous disease caused by Leishmania infantum in northeastern Brazil: A case report.” Vet Parasitol Reg Stud Reports. 2023 Jun; 41:100881.
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