Frequency of detection and load of amastigotes in the pancreas of Leishmania infantum-seropositive dogs: clinical signs and histological changes

Clinical findings and prognostic factors for mortality in hospitalized dogs with leishmaniosis: aretrospective study

This retrospective study evaluated factors responsible for mortality of dogs hospitalized for Canine Leishmaniosis. Medical records of 31 dogs with leishmaniosis from a Portuguese Veterinary Teaching Hospital were examined between August 2018 and January 2022. Females (n = 18) and pure breed dogs (n = 27) were overrepresented, with higher frequency of Labrador Retriever (n = 4). Median age was 7 years (interquartile range=7). Most had historical findings of lethargy (n = 26) and the commonest clinicopathological abnormality was hypoalbuminemia (n = 26). Eleven dogs were classified as LeishVet stage II, 10 stage III and 10 stage IV. Fourteen dogs (45.2%) died or were euthanized, with azotemia, leukocytosis, stage IV, absence of diagnosis before hospitalization and lack of leishmaniosis specific treatment during hospitalization contributing to mortality. Absence of hypoalbuminemia and stages II/III increased survival. Mean hospitalization length prior to discharge was 5.41days ( ± 1.84) and diarrhea prolonged hospital stay.

Leishmania infantum Axenic Amastigotes Induce Human Neutrophil Extracellular Traps and Resist NET-Mediated Killing

Neutrophils are multifaceted cells that, upon activation, release meshes of chromatin associated with different proteins, known as neutrophil extracellular traps (NETs). Leishmania amazonensis promastigotes and amastigotes induce NET release, and we have identified the signaling pathways involved in NET extrusion activated by promastigotes. Amastigotes maintain the infection in vertebrate hosts, and we have shown the association of NETs with amastigotes in human biopsies of cutaneous leishmaniasis. However, the interaction of amastigotes and neutrophils remains poorly understood. Our study aimed to characterize the pathways involved in the formation of NETs induced by axenic amastigotes from L. infantum, the causal agent of visceral leishmaniasis. Human neutrophils pretreated with signaling pathway inhibitors were incubated with amastigotes, and NET release was quantified in the culture supernatant. Amastigote viability was checked after incubation with NETs. We found that the release of NETs by neutrophils stimulated with these amastigotes requires the participation of elastase and peptidyl arginine deaminase and the involvement of PI3K, ROS, and calcium. Moreover, amastigotes are not susceptible to NET-mediated killing. Altogether, these findings improve our comprehension of the signaling pathways implicated in the interaction between amastigotes and human neutrophils.

Report of the presence of Leishmania infantum in the milk of a naturally infected female dog in Brazil

Dogs are the most important reservoir of Leishmania infantum, the causal agent of visceral leishmaniasis in Brazil. Although lymphoid tissue is the most important biological tissue where amastigotes can be found, this paper describes the presence of L. infantum DNA in the milk of a lactating naturally infected female dog. This finding suggests the need for further studies to elucidate whether breastfeeding can be a route of infection.

Canine Leishmaniasis: Update on Epidemiology, Diagnosis, Treatment, and Prevention

Dog are the main reservoir of Leishmania infantum, causing canine leishmaniasis, an incurable multisystemic disease that leads to death in symptomatic dogs, when not treated. This parasite causes visceral, cutaneous, and mucosal leishmaniasis in people in the Mediterranean Basin, North Africa, South America, and West Asia. This disease is mostly unknown by veterinarians outside the endemic areas, but the disease is expanding in the Northern Hemisphere due to travel and climate change. New methodologies to study the epidemiology of the disease have found new hosts of leishmaniasis and drawn a completely new picture of the parasite biological cycle. Canine leishmaniasis diagnosis has evolved over the years through the analysis of new samples using novel molecular techniques. Given the neglected nature of leishmaniasis, progress in drug discovery is slow, and the few drugs that reach clinical stages in humans are unlikely to be commercialised for dogs, but several approaches have been developed to support chemotherapy. New-generation vaccines developed during the last decade are now widely used, along with novel prevention strategies. The implications of the epidemiology, diagnosis, treatment, and prevention of canine leishmaniasis are fundamental to public health.