L. martiniquensis was identified in 4 sport horses during 2019–2023 (Table). Case 1 (identified in May 2019) was in a 4-year-old Akchal-Teke mare admitted to the veterinary clinic of the University of Veterinary Sciences in Brno, Czech Republic. The mare had several small nodules (3–10 mm) on the left upper eyelid; the largest was localized near the medial canthus, measuring ≈1 cm in diameter. The mare lived in north Moravia and had been imported from Ukraine 2 years previously without any obvious lesions. Equine sarcoid was suspected on the basis of clinical examination, and bovine papillomavirus type 1 was detected by PCR in the skin smear. Case 2 (identified in May 2021) was in a 5-year-old Kladruber mare from a large stud farm that was admitted to the clinic with a group of small nodules (5–15 mm) located unilaterally on the facial area near to the lower eyelid. Case 3 was in a 5-year-old Fjord mare seen in May 2021 by veterinarians at the Equine Clinic of the Veterinary University (Vienna, Austria) with nodular lesions on the lower eyelid, chest, and udder; Leishmania was detected in the eyelid and udder lesions and bovine papillomavirus was detected in all 3 lesions. Case 4 was in a 12-year-old gelding living in the northwestern Czech Republic, first seen by the veterinarian in January 2023 for lesions on the left facial area. The clinical manifestation was very similar to those seen in cases 1–3. Again, the lesions were initially suspected to be sarcoid tumors, but the surface eventually exulcerated into an open wound. With supportive treatment, the lesion resolved over a period of 15 months; follow-up at 27 months showed no recurrence of lesions.

Figure 1

Figure 1. Cutaneous lesions during initial clinical examination and detection of Leishmania amastigotes from study of autochthonous Leishmania (Mundinia) martiniquensisinfections in horses, Czech Republic...

Figure 2

Figure 2. Phylogenetic analysis of isolates from study of autochthonous Leishmania (Mundinia) martiniquensisinfections in horses, Czech Republic and Austria, 2019–2023. Analysis of the internal transcribed spacer...

We obtained bioptic samples from cutaneous lesions using a fine needle aspiration biopsy (FNAB) for cases 1, 2, and 4 or as impression smears for case 3. We conducted routine microscopic evaluation of the FNAB material after Diff-Quick staining. Examination of the smears revealed intracytoplasmic Leishmania amastigotes in cells tentatively identified as neutrophiles (Figure 1). We cultured material obtained by FNAB from periorbital lesions (cases 1, 2, and 4) at 23°C on rabbit blood agar SNB-9 supplemented with fetal bovine serum, RPMI-1640, Schneider’s medium, and antibiotics; we then cryopreserved a single strain. Conventional PCR targeting the Leishmania internal transcribed spacer 1 (10) performed on clinical material revealed identical sequences in all 4 cases with 100% identity to other GenBank sequences of L. martiniquensis worldwide but only 99.5% concordance with previous cases in Germany and Switzerland (Figure 2).

Antibodies to Leishmania were detected by an indirect fluorescent antibody test using glass slides coated with promastigote L. infantum (VMRD, https://www.vmrd.com) and antihorse IgG (whole molecule) FITC conjugate (Sigma Aldrich, https://www.sigmaaldrich.com). We diluted serum samples in a 2-fold series starting with a 1:50 base dilution and used positive and negative control serum samples. We considered a titer >50 positive. We found antibodies to Leishmania at titers of 50 (cases 1, 2, and 3) and 100 (case 4).

We report 4 equine cases of L. martiniquensis infection outside the known range of the typical leishmaniasis caused by L. infantum in Europe, detected >12 years after the last published L. martiniquensis cases in Germany (2) and Switzerland (3). The cases occurred over a period of >3 years with no proven link between them and were also geographically dispersed across central Europe, suggesting that horses play a nonnegligible role as reservoir hosts throughout the range of L. martiniquensis. The symptomatology of L. martiniquensis cases in horses is strikingly uniform. In all 4 newly described cases, infection was diagnosed as cutaneous lesions near the eyes or in the facial area, resembling previous instances in which 7 of 10 cases were reported as lesions on the head (2,11,12).

All 4 cases were initially suspected to be sarcoid, a common skin tumor in horses caused by bovine papillomaviruses types 1, 2, and 13. Of note, in 2 cases (case 1 and 3) bovine papillomavirus types 1 and 2 were detected by PCR in lesions with Leishmania but also in lesions without the parasite. This association between sarcoid-like lesions and Leishmania infection is very suggestive. We therefore believe that the sarcoid may be attractive to blood-sucking insects (including biting midges, the potential vectors of Mundinia), thus opening the window for parasite infection. Additional cases of L. martiniquensis infection could possibly be underreported because of misdiagnosis and treatment as sarcoid or masked by a true sarcoid. Also, cases of cutaneous leishmaniosis in herbivores diagnosed in Europe should always be evaluated for the possibility of being caused by L. martiniquensis, even in areas in which L. infantum is endemic (13), particularly in the absence of sand flies.

The serologic response to L. martiniquensis remains poorly understood. A single case of cutaneous leishmaniasis in a cow revealed a robust antibody response (3). More recently, Carbonara et al. (13) reported low antibody titers in equids, including those with skin lesions or asymptomatic infections. Consistent with those observations, our findings confirm that horses with mild skin lesions exhibit only a limited antibody response. Nevertheless, serologic testing during active infection could serve as a valuable diagnostic tool.

The presence of biting midges is ubiquitous in Europe (14), and the equine population is in daily contact with them during active season. The occurrence of 4 independent cases of equine leishmaniosis caused by L. martiniquensis suggests its endemic status and circulation in Central Europe. The extent of distribution of this kinetoplastid in the equine population and other hosts in Europe remains speculative, as does its transmission biology. Given its zoonotic potential, this pathogen should be widely investigated in cases of equine skin lesions using a combination of cytology and PCR followed by sequencing. Similarly, possible L. martiniquensis infection should be anticipated in suspected visceral and cutaneous cases of human leishmaniasis, including patients without a history of travel to endemic areas.