This review is aimed at providing a comprehensive outline of the immune response displayed against cutaneous leishmaniasis (CL), the more common zoonotic infection caused by protozoan parasites of the genusLeishmania.Although of polymorphic clinical presentation, classically CL is characterized by leishmaniotic lesions on the face and extremities of the patients, which can be ulcerative, and even after healing can lead to permanent injuries and disfigurement, affecting significantly their psychological, social, and economic well-being. According a report released by the World Health Organization, the disability-adjusted life years (DALYs) lost due to leishmaniasis are close to 2.4 million, annually there are 1.0–1.5 million new cases of CL, and a numerous population is at risk in the endemic areas. Despite its increasing worldwide incidence, it is one of the so-called neglected tropical diseases. Furthermore, this review provides an overview of the existing knowledge of the host innate and acquired immune response to cutaneous species ofLeishmania.The use of animal models and ofin vitrostudies has improved the understanding of parasite-host interplay and the complexity of immune mechanisms involved. The importance of diagnosis accuracy associated with effective patient management in CL reduction is highlighted. However, the multiple factors involved in CL epizoology associated with the unavailability of vaccines or drugs to prevent infection make difficult to formulate an effective strategy for CL control.

Leishmania parasites are a group of kinetoplastid pathogens that cause a variety of clinical disorders while maintaining cell communication by secreting extracellular vesicles. Emerging technologies have been adapted for the study of Leishmania-host cell interactions, to enable the broad-scale analysis of the extracellular vesicles of this parasite. Leishmania extracellular vesicles (LEVs) are spheroidal nanoparticles of polydispersed suspensions surrounded by a layer of lipid membrane. Although LEVs have attracted increasing attention from researchers, many aspects of their biology remain unclear, including their bioavailability and function in the complex molecular mechanisms of pathogenesis. Given the importance of LEVs in the parasite-host interaction, and in the parasite-parasite relationships that have emerged during the evolutionary history of these organisms, the present review provides an overview of the available data on Leishmania, and formulates guidelines for LEV research. We conclude by reporting direct methods for the isolation of specific LEVs from the culture supernatant of the promastigotes and amastigotes that are suitable for a range of different downstream applications, which increases the compatibility and reproducibility of the approach for the establishment of optimal and comparable isolation conditions and the complete characterization of the LEV, as well as the critical immunomodulatory events triggered by this important group of parasites.

African trypanosomiasis or sleeping sickness is a zoonotic disease caused by Trypanosoma brucei, a protozoan parasite transmitted by Glossina spp. (tsetse fly). Parasite introduction into mammal hosts triggers a succession of events, involving both innate and adaptive immunity. Macrophages (MΦ) have a key role in innate defence since they are antigen-presenting cells and have a microbicidal function essential for trypanosome clearance. Adaptive immune defence is carried out by lymphocytes, especially by T cells that promote an integrated immune response. Like mammal cells, T. b. brucei parasites release extracellular vesicles (TbEVs), which carry macromolecules that can be transferred to host cells, transmitting biological information able to manipulate cell immune response. However, the exact role of TbEVs in host immune response remains poorly understood. Thus, the current study examined the effect elicited by TbEVs on MΦ and T lymphocytes. A combined approach of microscopy, nanoparticle tracking analysis, multiparametric flow cytometry, colourimetric assays and detailed statistical analyses were used to evaluate the influence of TbEVs in mouse mononuclear cells. It was shown that TbEVs can establish direct communication with cells of innate and adaptative immunity. TbEVs induce the differentiation of both M1- and M2-MΦ and elicit the expansion of MHCI⁺, MHCII⁺ and MHCI⁺MHCII⁺ MΦ subpopulations. In T lymphocytes, TbEVs drive the overexpression of cell-surface CD3 and the nuclear factor FoxP3, which lead to the differentiation of regulatory CD4⁺ and CD8⁺ T cells. Moreover, this study indicates that T. b. brucei and TbEVs seem to display opposite but complementary effects in the host, establishing a balance between parasite growth and controlled immune response, at least during the early phase of infection.

The tick Amblyomma dissimile Koch feeds preferentially on reptiles (Squamata), although amphibians (Anura) also seem to be important hosts. We report an A. dissimile nymph infesting a blue-winged macaw, Primolius maracana, held in captivity in the Mangal das Garças Park, State of Pará, Brazil. Environmental observations suggest that free-living iguanas (Iguana iguana), which used to walk on the bird enclosure in the park, were the source of the A. dissimile tick that infested the blue-winged macaw. We provide the second world record of a bird host for A. dissimile, and the first bird record for this species in South America.

Leishmania parasites often infect different host types over the course of their complex life cycle, and the interspecific correlations exist between traits expressed in natural reservoirs and potential new hosts or vectors. Comparable to other eukaryotes, Leishmania release extracellular vesicles that promote crucial interactions, modulating the subsequent systemic immune response to establish host infection, which seriously affects the health of humans and pets (dogs or cats). Recent studies in endemic areas of Brazil concluded that canine leishmaniases were predominantly due to Leishmania amazonensis and not restricted to Leishmania infantum (syn. Leishmania chagasi). Under these premises, the diagnosis of canine leishmaniasis needs improvement, including the identification of the current etiological agent, clinical differential diagnosis, and histopathologic features. The study aims to achieve two main objectives: to present findings on natural canine infections and to highlight the importance of differential diagnosis in companion animals. It also seeks to investigate the role of lipids in Leishmania extracellular vesicles (LEVs) in vitro, focusing on the emerging research area that explores the mechanisms and biological aspects of parasite–host interactions. In essence, the study aims to bridge gaps in our understanding of how lipids in LEVs influence parasite–host interactions, while emphasizing the significance of accurate diagnosis in companion animals. Therefore, future studies of parasitology research for both fields are important for advancing diagnostics, prognostics, and treatments, as well as addressing the ongoing global need for prevention, control, elimination, and eradication.