Hemophagocytic syndrome secondary to canine visceral leishmaniasis: Relationship with clinical score, parasite load and serum cytokines.

Visceral leishmaniasis (VL) is a vector-borne disease which is among the six most important endemic diseases in the world. In Brazil, one of the countries with the highest number of cases, it is caused by the protozoan Leishmania infantum. In humans, VL may be associated with a rare and high-mortality syndrome known as Hemophagocytic Lymphohistiocytosis Syndrome (HLH). This syndrome, not yet described in dogs, is characterized by an exaggerated inflammatory reaction, uncontrolled and dysfunctional activation of T lymphocytes, macrophages, and natural killer (NK) cells. This study aimed to analyze the clinical and laboratory characteristics related to the occurrence of HLH and correlate them with the clinical score, parasite load and serum cytokines in dogs with VL. Of the 55 dogs with canine visceral leishmaniasis (CVL), eight dogs (14.55 %) presented five criteria of the HLH. The clinical score demonstrated a weak indirect association with hemoglobin, the parasite load had a weak indirect relationship with ferritin, and a weak direct relationship with triglycerides. The cytokines IL-6 and IL-2 had an indirect relationship with bleeding time and neutrophils, respectively. These results demonstrated the occurrence of five clinical characteristics of HLH, indicating that this rare and highly fatal syndrome occurs in CVL and is correlated with a worse clinical score.