Molecular and parasitological evidence of Leishmania (Mundinia) martiniquensis infection in a horse from Brazil.

Molecular and parasitological analyses identified Leishmania (Mundinia) martiniquensis infection in a horse from Brazil that showed persistent skin nodules and lymph node enlargement. This is the first documented natural infection of this parasite species in a Brazilian horse, highlighting the presence of this emerging pathogen in areas already endemic for other forms of leishmaniasis.

Background and Context

• Leishmania (Mundinia) martiniquensis is a newly recognized human pathogen that has been increasingly reported in domestic animals.
• The study area in Brazil is endemic for cutaneous and visceral leishmaniasis, primarily caused by other Leishmania species such as Leishmania (Leishmania) infantum.
• Equine leishmaniasis has been reported previously, generally attributed to L. (L.) infantum.

Case Description

• The subject was a naturally infected mare from Brazil with no travel history to endemic areas outside the country.
• Clinical signs included persistent nodular skin lesions and enlargement of cervical lymph nodes.
• There was no systemic involvement detected in the mare, indicating a localized infection.

Diagnostic Investigations

• Initial suspicion was infection by L. (L.) infantum due to endemicity and clinical signs.
• Indirect immunofluorescence assay detected anti-L. (L.) infantum antibodies with a titer of 320.
• Histopathological examination of the lymph node revealed amastigote forms consistent with Leishmania spp.
• Xenodiagnosis was performed using the sandfly vector Lutzomyia (Lutzomyia) longipalpis to assess parasite transmission potential.
• Limited blood feeding was observed during vector exposure and no transmission was detected.
• Flagellated parasites were isolated in vitro from cervical lymph node biopsy samples.

Molecular Characterization

• Samples and isolates were analyzed using PCR amplification targeting Leishmania-specific kinetoplast DNA (kDNA) and the internal transcribed spacer 1 (ITS1) region of Trypanosomatidae ribosomal DNA.
• Sanger sequencing of the PCR products identified the parasite as Leishmania (Mundinia) martiniquensis, rather than the initially suspected L. (L.) infantum.

Significance and Implications

• This study provides documented molecular and parasitological evidence of natural L. (M.) martiniquensis infection in a horse in Brazil for the first time.
• The findings reveal the circulation of this emerging pathogen in a region already endemic for other types of leishmaniasis, complicating the epidemiological landscape.
• The presence of L. (M.) martiniquensis in domestic animals could have implications for human and animal health, highlighting the need to consider this parasite in diagnoses of equine skin and lymph node lesions.
• The inability to demonstrate vector transmission through the examined sandfly species suggests that the epidemiological cycle and vector-host relationships of L. (M.) martiniquensis require further research to clarify its transmission dynamics.
• Additional studies are necessary to define reservoir hosts, identify competent vectors, and understand the pathogen’s epidemiology in Brazil and other endemic regions.