2. Importance of diagnosis

The available therapies for leishmaniasis are far from optimal due to their toxicity, high costs, lack of efficacy, lack of access in certain areas, and emerging drug resistance. Treatment efficacy depends on strains and species and there are currently no effective vaccines available for any form of human leishmaniasis [2].

Some vaccines exist for veterinary use. Being launched in Portugal in 2011, CaniLeish® was the first vaccine for CanL in the European Union. In Brazil, LeishTec® vaccine was also registered but only offers about 40% of protection against infection. LetiFend® has recently been registered in Europe, but there is limited information available [19]. Despite the efforts, Leishmania vaccinology still has a lot to improve till an effective and universal vaccine is developed [20].

In the absence of human vaccines and due to the zoonotic character of the disease, accurate detection of infection in humans and dogs is crucial for the control of leishmaniasis [21].

Several specific challenges associated to Leishmania infection and leishmaniasis must be overcome. As for any disease, the diagnostic process should be simple, robust, automated, requiring inexpensive reagents and minimal operator intervention without diminishing the fidelity of the results. Notwithstanding, considering that this disease affects mostly poor people in countries with undeveloped and underfinanced health systems, the tests should be cheap and easy to perform in field conditions [22, 23]. Moreover, the detection of asymptomatic infection, often characterized by reduced parasite loads and low specific serology, is essential. In fact, clinical and epidemiological management of Leishmania infections can only be fully successful once a diagnostic test with these characteristics is available [24]. The available tools are adequate for detection of disease, (in conjunction with clinical evaluation) but present limitations for diagnosis of infection in asymptomatic patients and dogs. Therefore, the information of real prevalence of infection and overall burden of disease is believed to be underestimated [22].

Coinfection with HIV is common in VL cases and has a disastrous impact since immunocompromised individuals have more severe manifestations and atypical symptoms that complicate treatment [2]. Pregnant women can be considered a risk population, as HIV-infected patients, being more susceptible to Leishmania relapse and changes in immune response. Immunosuppression by HIV had an enormous impact and highly contributed to the increased number of leishmaniasis cases [3]. Coinfection of L. donovani and L. infantum with HIV has been identified as a meaningful clinical problem, and presents higher mortality rates. Up to 70% of VL cases in southern Europe are associated with HIV infection. VL is the third most frequent opportunistic infection in many parts of the world, and the coinfection with HIV is now reported in 35 countries [25].
