Leishmaniasis is a vector-born chronic infectious disease caused by a group of protozoan parasites of the genus Leishmania. Whereas most immunocompetent individuals will not develop disease after Leishmania infection, immunosuppression is a well-established risk factor for disease. The most severe form is visceral leishmaniasis (VL), which is typically fatal if untreated. Whereas human immunodeficiency virus (HIV) co-infection (VL-HIV) was initially mainly reported from southern Europe, it is now emerging in other regions, including East Africa, India, and Brazil. VL has also been found in a wide range of non-HIV-related immunosuppressive states, mainly falling under the realm of transplantation medicine, rheumatology, haematology, and oncology. Clinical presentation can be atypical in immunosuppressed individuals, being easily misdiagnosed or mistaken as a flare-up of the underlying disease. The best diagnostic approach is the combination of parasitological and serological or molecular methods. Liposomal amphotericin B is the drug of choice. Treatment failure and relapse rates are particularly high in cases of HIV co-infection, despite initiation of antiretroviral treatment. Primary prophylaxis is not recommended, but secondary prophylaxis is recommended when the patient is immunosuppressed. Cutaneous leishmaniasis can have a number of particular features in individuals with immunosuppression, especially if severe, including parasite dissemination, clinical polymorphism with atypical and often more severe clinical forms, and even visceralization. Mucosal leishmaniasis is more common. Treatment of cutaneous and mucosal leishmaniasis can be challenging, and systemic treatment is more often indicated. With globally increased travel and access to advanced medical care in developing countries, the leishmaniasis burden in immunosuppressed individuals will probably continue to rise, warranting increased awareness and enhanced surveillance systems.

Canine leishmaniasis is an important zoonosis caused by uncontrolled infection with Leishmania infantum, where an inappropriate immune response is not only responsible for permitting this intracellular parasite to multiply, but is also responsible for several of the pathological processes seen in this disease. Effective canine vaccines are therefore a highly desirable prevention tool. In this randomised, double-blinded, controlled trial, the efficacy of the LiESP/QA-21 vaccine (CaniLeish, Virbac, France) was assessed by exposing 90 naïve dogs to natural L. infantum infection during 2 consecutive transmission seasons, in two highly endemic areas of the Mediterranean basin. Regular PCR, culture, serological and clinical examinations were performed, and the infection/disease status of the dogs was classified at each examination. The vaccine was well-tolerated, and provided a significant reduction in the risk of progressing to uncontrolled active infection (p = 0.025) or symptomatic disease (p = 0.046), with an efficacy of 68.4% and a protection rate of 92.7%. The probability of becoming PCR positive was similar between groups, but the probability of returning to a PCR negative condition was higher in the vaccinated group (p = 0.04). In conclusion, we confirmed the interest of using this vaccine as part of a comprehensive control program for canine leishmaniasis, and validated the use of a protocol based on regular in-depth assessments over time to assess the efficacy of a canine leishmaniasis vaccine. Canine leishmaniasis is caused by uncontrolled infection with Leishmania infantum. The dog is also the principle reservoir of this parasite which can infect humans. The key determinant of the outcome of infection is the ability of the dog's immune system to respond appropriately. This should be mainly cell-mediated immunity; the antibody responses often desired for viral or bacterial infections are not protective. Therefore, vaccines capable of inducing this cell-mediated immune profile are a desirable prevention tool. Previous studies with CaniLeish (consisting of the parasite's excreted-secreted proteins with an adjuvant) have demonstrated the ability of this vaccine to induce an appropriate immune profile and to protect against an intravenous challenge, as well as to reduce the risk of transmission of the parasite to the sandfly vector. This paper reports a study where vaccinated dogs were exposed to natural parasite transmission over two full seasons in two Mediterranean locations (one in Italy and one in Spain). Data from the unvaccinated control group confirmed that the levels of exposure were high. We demonstrated that the vaccine significantly reduces the risk of progressive infections and disease confirming the interest of using vaccination as part of a comprehensive control program for this disease.

We compared xenodiagnosis with quantitative polymerase chain reaction in skin biopsies from 3 patients with maculopapular or nodular post–kala-azar dermal leishmaniasis (PKDL). All patients infected sand flies. Parasite loads in skin varied from 1428 to 63 058 parasites per microgram. PKDL detection and treatment are important missing components of the kala-azar elimination program.

The protective capabilities of three Leishmania recombinant proteins - histone 1 (H1) and hydrophilic acylated surface protein B1 (HASPB1) immunized singly, or together as a protein cocktail vaccine with Montanide, and the polyprotein MML immunized with MPL-SE adjuvant - were assessed in beagle dogs. Clinical examination of the dogs was carried out periodically under blinded conditions and the condition of the dogs defined as asymptomatic or symptomatic. At the end of the trial, we were able to confirm that following infection with L. infantum promastigotes, five out of eight dogs immunized with H1 Montanide, and four out of eight dogs immunized with either the combination of HASPB1 with Montanide or the combination of H1+HASPB1 with Montanidetrade mark, remained free of clinical signs, compared with two out of seven dogs immunized with the polyprotein MML and adjuvant MPL-SE, and two out of eight dogs in the control group. The results demonstrate that HASPB1 and H1 antigens in combination with Montanide were able to induce partial protection against canine leishmaniasis, even under extreme experimental challenge conditions.