Leishmania Infantum

Leishmaniases are parasitic diseases of the monocyte-macrophage system, whose pathogenic agent is a flagellated protozoan of the Leishmania genus. They are transmitted at night by the female phlebotominae. The parasite, counting more than fifty different species including 20 infecting humans, has a zoonotic or anthroponotic transmission, from the vector to the mammalian reservoir (Lachaud et al., 2017).

The parasite has two morphological stages in its life cycle: a flagellated promastigote form, extracellular and mobile, found in the digestive tube of the phlebotominae. The amastigote form, immobile and intracellular, actively multiplies within the mammalian host macrophages until their lysis, releasing them to infect other macrophages (Pace, 2014).

The disease is endemic in four continents (Africa, Latin and South Americas, Europe), with 10 to 20 million people suspected of being infected worldwide, 400,000 new cases of visceral leishmaniasis every year, and 350,000,000 people at risk of infection (Okwor & Uzonna , 2016).

Three forms of leishmaniases are described: visceral, cutaneous or mucocutaneous, asymptomatic carriers also exist. Clinical signs differ according to the species of Leishmania and the immune response of the host.

Asymptomatic forms are very common in endemic areas, where prevalence is high: 12,5% of blood donors are asymptomatic in the region of Bologna (Ortalli et al., 2019).

Cutaneous leishmaniasis, or Oriental sore, corresponds to a circular lesion at the vector sting zone. It starts as a small inflammatory papule that grows progressively.

Mucocutaneous leishmaniasis is observed in Latin America. After a facial cutaneous lesion, a granuloma grows, destroying the nasal then buccal walls and the larynx (espundia).

Visceral leishmaniasis (VL) is a slow evolution of a visceral infection, caracterised by the triad anemia, splenomegalia and irregular fever. In Europe, VL, induced by L. infantum, is endemic of several regions in France, Italie, Greece and Spain. Usually observed among children under 8 years old and in limited areas, adult (mostly aged patients) and imported cases are increasing. It is an opportunistic disease of immunodepressed patients, lethal without treatment and commonly associated with AIDS (Burza et al., 2018).

Associated to direct detection techniques (medullary sampling), serology is considered as a major tool for the diagnosis of VL (Lévêque et al., 2020a) and classical techniques (immunofluorescence and ELISA) are widely used. Nevertheless, these techniques may lack sensitivity and specificity in particular for immunodepressed or asymptomatic patients, as their immune reaction is low (Elmahallawy et al., 2014, Griensven et al., 2014, Lévêque et al., 2020b).