Introduction

Classification

Taxonomy

• Kingdom: Protista
• Phylum: Sarcomastigophora
• Subphylum: Mastigophora
• Class: Zoomastigophora
• Order: Kinetoplastida
• Family: Trypanosomatidae
• Genus: Leishmania
• Species: Infantum

Etymology

• Leishmania infantum is in the Leishmania donovani complex. It is occasionally incorrectly referred to as L donovani.
• The name, Leishmania chagasi is a synonym for L. infantum used in South America.

Active Forms

Clinical Effects

Epidemiology

Habitat

• Sand flies of the genera Phlebotomus and Lutzomyia.
• Found mainly in tropics and subtropics, some species in temperate regions.
• Habitats range from desert to savanna to rainforest with each species possessing specific ecological requirements.
• Peridomestic species of sand flies vector Leishmania infections to man.

Lifecycle

• Flagellated promastigotes  multiply asexually in the sand fly midgut by longitudinal binary fission.
• Promastigotes inoculated into mammalian host while sand fly takes blood meal.
• Promastigotes enter macrophages and transform into amastigotes  .
• Amastigotes divide by binary fission until the host cell ruptures and the parasites are released.
• Amastigotes infect nearby macrophages or move through vasculature to infect other organs, eg spleen and liver.
• Lifecycle completed when sand fly ingests amastigotes while blood feeding.

Transmission

• Usual route of transmission between dogs and between dog and human is by competent sand fly species.
• Direct transmission between dogs and humans has not been reported.
• Alternative routes of transmission:
  • Infected blood transfusions.
  • Contaminated needles/syringes.
  • Direct transfer from dog to dog through close contact, exchange of body secretions.
  • Congenital transmission reported in dogs.
  • Venereal transmission reported between dogs especially if mucosal ulcerations.

Pathological effects

Host immunological response to infection

• Cell-mediated immune responses (Th1 type) required for resistance.
• Antibodies produced but are not protective.
• Dogs that develop clinical leishmaniosis thought to have a genetic disposition to mount a humoral rather than cell-mediated immune response.
• Cell-mediated response to Leishmania antigen and other antigens is decreased in dogs with leishmaniosis.
• Dogs with clinical leishmaniosis have higher levels of IgG1 antibodies. Asymptomatic dogs have higher levels of IgG2 antibodies.

Host clinico-pathological response to infection

• Most infected dogs are asymptomatic. In endemic areas, only 10% of infected dogs develop overt clinical disease.
• Dogs with partial immunity may show only localized nodular/ulcerative lesions at site of sand fly bites.
• Susceptible dogs may develop clinical signs referable to one body system or multiple systems:
  • Chronic porgressive weight loss, malaise, lethargy, variable appetite loss.
  • Cutaneous lesions.
  • Lymphadenopathy, splenomegaly.
  • Muscle wasting.
  • Ocular lesions.
  • Lameness.
  • Polyuria, polydipsia.
  • Epistaxis Epistaxis.
  • Anemia Anemia: overview.
  • Diarrhea Diarrhea: parasitic.

Control

Control via animal

Initial therapy

• See Meglumine antimoniate Meglumine antimoniate.
  Meglumine antimoniate and miltefosine are licensed for the treatment of canine leishmaniosis in several European countries but may require importation and authorization in non-endemic countries.

Insecticide/repellent application to dogs

• Synthetic pyrethroids including deltamethrin collars, permethrin or permethrin/imidocloprid combination spot-on products Control of canine leishmaniosis.

Control via environment

• Destruction of sand fly habitat.

Vaccination

• CaniLeish® - the first vaccine against Canine leishmaniosis registered by the European Medicines Agency in 2011 by Virbac.

Diagnosis

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Solano-Gallego L, Koutinas A, Miró G et al (2009) Directions for the diagnosis, clinical staging, treatment and prevention of canine leishmaniosis. Vet Parasitol 165 (1-2), 1-18 PubMed.
• Tabar M D, Francino O, Altet L et al (2009) PCR survey of vectorborne pathogens in dogs living in and around Barcelona, an area endemic for leishmaniosis. Vet Rec 164 (4), 112-116 PubMed.
• Baneth G, Koutinas A F, Solano-Gallego L et al (2008) Canine leishmaniosis - new concepts and insights on an expanding zoonosis: part one. Trends Parasitol 24 (7), 324-330 PubMed.
• Miró G, Cardoso L, Pennisi M G et al (2008) Canine leishmaniosis - new concepts and insights on an expanding zoonosis: part two. Trends Parasitol 24 (8), 371-377 PubMed.
• Baneth G & Shaw S E (2002) Chemotherapy of canine leishmaniasis. Vet Parasitol 106 (4), 315-324 VetMedResource.
• Lindsay D S, Zajac A M & Barr S C (2002) Leishmaniasis in the American foxhounds: an emerging zoonosis? Comp Cont Ed Pract Vet 24 (4), 304-313 VetMedResource.
• Mauricio I L, Howard M K, Stothard J R et al (1999) Genomic diversity in the Leishmania donovani complex. Parasitol 119 (3), 237-246 PubMed.

Other sources of information

• European Medicines Agency: http://www.ema.europa.eu/ema/index.jsp?curl=pages/medicines/veterinary/medicines/002232/vet_med_000234.jsp&mid=WC0b01ac058001fa1c
• Advanced management of Canine Leishmaniosis. Proceedings of Southern European Veterinary Conference (SEVC) 2011 Symposium, Barcelona, Spain. September 30, 2011.
• Canine Leishmaniasis: an update. (1999) Ed R Killick-Kendrick.Proc Int Canine Leishmania Forum. Barcelona, Spain.
• Molyneux D H & Ashford R W (1983) The biology of Trypanosoma and Leishmania, parasites of man and domestic animals. International Publications Service, pp 185-225.