Protozoa transmitted by sand flies cause leishmaniasis, and several pathogenic species affect humans. Various clinical forms of the disease have been described, including visceral, cutaneous, and mucocutaneous leishmaniasis (1). Leishmania (Viannia) lainsoni was described in Brazil in 1987 as the causative agent of human cases of cutaneous leishmaniasis. Its vector is the Lutzomyia ubiquitalis sand fly (2). Other countries in Latin America have reported human cases of L. (V.) lainsoni infection. Researchers isolated the parasite from the rodent species Cuniculus paca, the lowland paca, in the state of Pará, Brazil, suggesting a potential wild reservoir (3,4).

This study reports the case of a dog (Canis familiaris) infected with L. (V.) lainsoni that was from the municipality of Barra Mansa, an urban area in Rio de Janeiro state with widespread visceral leishmaniasis (VL) (Appendix). The Ethics Committee on the Use of Animals–Fiocruz approved this work (license no. LW 19/20; https://www.ceua.fiocruz.br/ceuaw000.aspx).

Figure 1

Figure 1. Histologic sections from autochthonous Leishmania (Viannia) lainsoni in dog (Canis familiaris), Rio de Janeiro state, Brazil, 2023. A, B) Skin of the...

A 5-year-old male dog of mixed breed domiciled in Barra Mansa tested positive for VL by both rapid immunochromatographic testing and enzyme immunoassay (Bio-Manguinhos, https://portal.fiocruz.br/en/unidade/immunobiological-technology-institute-biomanguinhos) during epidemiologic surveillance in 2023 and was euthanized using the recommendations of the Brazilian Ministry of Health (https://www.gov.br). The dog had not moved to other regions and had localized alopecia, crusted skin ulcers, onychogryphosis, keratoconjunctivitis, normocytic normochromic anemia, hyperproteinemia, hyperglobulinemia, hypoalbuminemia, and a low albumin:globulin ratio (Appendix). Histopathologic changes included skin with hyperkeratosis and multifocal and moderate granulomatous dermatitis, as well as lymphoid hyperplasia of the spleen. Immunohistochemistry was positive for amastigote forms of Leishmania in skin and spleen (Figure 1).

Figure 2

Figure 2. Evolutionary analysis of autochthonous Leishmania (Viannia) lainsoni in dog (Canis familiaris), Rio de Janeiro state, Brazil, 2023. Bold text indicates isolate from...

We performed parasitologic and PCR tests (Appendix Table 2). We used multilocus enzyme electrophoresis with 5 enzyme profiles (phosphoglucomutase, glucose-6-phosphate dehydrogenase, nucleoside hydrolase, 6-phosphogluconate dehydrogenase, and phosphoglucose isomerase) (5). We extracted DNA from the isolated parasite and used it for PCR restriction fragment length polymorphism analysis (HaeIII and BstUI). We sequenced the 70-kDa heat shock protein products with the same primers by Sanger sequencing (primers: BankIt2825220 and Seq1PP760383) (6). Those techniques identified the parasite as L. (V.) lainsoni in all profiles studied in the bone marrow sample (Figure 2).

Like other species of the subgenus Viannia, L. (V.) lainsoni can cause ulcerative or nodular dermal lesions in humans (4). The clinical signs found in this infected dog included onychogryphosis and skin alterations. Development of skin lesions can lead to hematogenous dissemination and parasitemia of internal organs, as observed in this case, and visceral involvement of lymph nodes and spleen (7). The positive results of serologic tests show flaws in the specificity of the techniques because those tests were validated for detecting dogs with canine VL caused by L. (Leishmania) infantum. Hematocrit values less than the reference range, along with a slight increase in total protein, are expected in chronic diseases. We observed no changes in renal function markers. The host–parasite interaction has been extensively studied in dogs infected with L. (L.) infantum; however, little is known about that interaction in dogs infected with other Leishmania species.

In Latin America, L. (V.) lainsoni is found in tropical and sub-Andean regions with different climatic conditions. Its presence in other countries highlights the high dispersal capacity of the parasite and potential involvement of unidentified mammalian host vectors. Barra Mansa has a crucial migratory flow because it is located on the banks of the Paraíba do Sul River and influences the Médio Paraíba region and southern part of the south-central region of Rio de Janeiro State.

The dog lived in an area surrounded by natural and abundantly wooded areas. A large portion of the Hemlock Forest is located in Barra Mansa, and C. paca rodents are part of the local fauna and could serve as reservoirs of L. (V.) lainsoni in that area (8).

Few entomologic surveys have been conducted in Barra Mansa, and only Lu. sallesi and Lu. longipalpis sand flies were confirmed, limiting the conclusions of this study (9). Although the Lu. ubiquitalis sand fly is considered the primary vector of L. (V.) lainsoni in Brazil, other species such as Lu. nuneztovari anglesi and Lu. velascoi sand flies in Bolivia have been reported (10). Therefore, identification of a dog infected with L. (V.) lainsoni in Barra Mansa may be linked to transmission by other yet undocumented sand fly species in that municipality. The dog did not have a history of moving to other locations. We consider environmental changes caused by humans in the region, as well as local wildlife and migratory flows, as possible causes of infection. This study raises several questions. Is a new and yet unknown disease cycle being established locally? What is the risk for the disease becoming endemic in the population? Will the cycle persist? Also, could other regions in Brazil or elsewhere face similar risks of emerging Leishmania species infecting dogs? Further epidemiologic investigations and taxonomic characterization studies are essential and should be continuously supported. Efforts to create clearer specificity in serologic diagnostic techniques are also needed.

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Suggested citation for this article: Santos ICdS, de Avelar DM, Miranda LdFC, Júnior AAVM, Oliveira LK, Ventura LdS, et al. Autochthonous Leishmania (Viannia) lainsoni in dog, Rio de Janeiro State, Brazil, 2023. Emerg Infect Dis. 2025 May [date cited]. https://doi.org/10.3201/eid3105.241058