of the patient, and ultimately the public, at risk.
Although the exact species of sandflies that transmit Leishmania are not present in Canada, reports of Leishmania maintaining itself within groups of kennelled foxhounds in 18 states and two provinces strongly suggest that the parasite can be transmitted from dog to dog: through bites, breeding or blood transfusions. In addition, it has recently been demonstrated that ticks can also transmit leishmaniosis.
Therefore, although unfortunate, Leishmania establishment in Canada and the U.S. remains possible.
Leishmania’s secret weapon
Treatment of leishmaniosis is currently limited to very few drugs, most of which have been in use for decades. In recent years, there has been an increase in Leishmania drug resistance and treatment failure. Scientists, including us, are searching for clues to better understand how these parasites survive in the presence of anti-leishmanial drugs. A number of experiments have led us (and others) to focus on Leishmania’s release of extracellular vesicles.
Extracellular vesicles are small, round particles with a fatty outer membrane, and they are produced by all living cells, including Leishmania parasites. Although tiny — you need an electron microscope to see them — these particles transport valuable cargo that ranges from DNA to fats and proteins. The contents of these vesicles provide a “snapshot” of their cell of origin, and can be “delivered” to nearby cells.
Recent studies have found that not only do the size and shape of these vesicles differ between sensitive and drug-resistant strains of Leishmania, but vesicles produced by drug-resistant parasites contain special drug-resistance molecules.
A better understanding of extracellular vesicles’ function is another step towards understanding how drug resistance spreads among Leishmania populations with the goal of preventing it. Additionally, research has demonstrated that when an infected sandfly bites a human, it’s not just parasites that are injected into the bloodstream: extracellular vesicles come along too, and are confronted by our immune system.
Studying extracellular vesicles may provide vital information for the development of new Leishmania therapies or a vaccine.
Mandatory reporting of canine leishmaniosis cases by veterinarians, easy access to fast and reliable diagnostic tests and appropriate treatments and an overhaul of animal importation regulations are critical.
A “One Health” approach, requiring the collaboration of human, animal, and environmental health partners, is key to preventing Leishmania cases in Canada and the U.S.
Victoria Wagner is a Veterinarian and M.Sc. student in Molecular Parasitology, Université de Montréal
Christopher Fernandez-Prada is Assistant professor at Université de Montréal (Faculty of Veterinary Sciences); Head of the animal parasitology diagnostic laboratory of UdeM; Adjunct professor McGill University (Faculty of Medicine), Université de Montréal
Martin Olivier is Full Professor at McGill University, Departments of Medicine, Microbiology and Immunology; Senior Investigator at the Research Institute of the McGill University Health Centre and Chair of the Laboratory for the Study of Host-Parasite Interaction., McGill University