Leshmania and Vectors

• Leishmaniasis is a parasitic disease caused by the protozoa belonging to the genus, Leishmania
• Types of Leishmaniasis

  • Visceral Leishmaniasis
  • Cutaneous Leishmaniasis
  • Mucocutaneous Leishmaniasis
  • Diffuse Cutaneous Leishmaniasis
• The clinical spectrum of the disease depends on the age, previous exposure and immune status of the host
• The infection is a zoonosis that occurs in numerous geographical zones
• Synonyms for Leishmaniasis

  • kala azar
  • black fever
  • sandfly disease
  • Dum-Dum fever
  • espundia
• Leishmaniasis is endemic in 88 countries on five continents
• 350 million people are at risk of leishmaniasis
• 12 million people are affected by leishmaniasis
• 1.5-2 million new cases of leishmaniasis are estimated to occur annually
• 500,000 new cases of visceral leishmaniasis occur annually
• Leishmania species and their associated diseases

  • Leishmania tropica (Cutaneous leishmaniasis)
  • Leishmania major (Cutaneous leishmaniasis)
  • Leishmania aethiopica (Cutaneous leishmaniasis)
  • Leishmania mexicana (Mucocutaneous leishmaniasis)
  • Leishmania braziliensis (Mucocutaneous leishmaniasis)
  • Leishmania donovani (Visceral leishmaniasis)
  • Leishmania infantum (Visceral leishmaniasis)
  • Leishmania chagasi (Visceral leishmaniasis)
• Vectors in the old world

  Leishmania is transmitted by Phlebotomus sp (Sand fly)
• Vectors in the new world

  Leishmania is transmitted by Lutzomia sp
• Sandflies breed in cracks of house walls, piles of rubbles and trash
• In Ghana, Leishmaniasis is common in the Volta region and Northern Ghana
• Promastigote

  Insect, motile stage of Leishmania
• Amastigote

  Mammalian, non-motile stage of Leishmania
• Amastigotes live and multiply in macrophages and other phagocytic cells in the internal organs
• Amastigotes live and multiply in the skin in the case of cutaneous leishmaniasis
• Amastigotes live and multiply in mucocutaneous tissue in the case of mucocutaneous leishmaniasis
• Promastigotes

  Flagellated and highly motile forms of the parasite found in sand flies
• Promastigotes multiply in the gut of the sand flies
• Transmission and life cycle of Leishmania

  1. Infection acquired by promastigotes inoculated

  2. Promastigotes taken up by phagocytic cells

  3. Promastigotes develop into amastigotes

  4. Amastigotes spread in the blood

  5. Female sand fly ingests amastigotes
• In rare cases, Leishmaniasis is spread from a pregnant woman to her baby
• Blood transfusion or contaminated needles and sexual contacts can also spread Leishmaniasis
• Symptoms of Visceral Leishmaniasis

  • Irregular bouts of fever
  • Substantial weight loss
  • Swelling of the liver and spleen
  • Chills
  • General anaemia
• Visceral Leishmaniasis could be fatal if not treated
• Post Kala-azar Dermal Leishmaniasis (PKDL) may arise after several years of successful treatment of L. donovani infection
• Cutaneous leishmaniasis is the most common form of the disease
• Cutaneous leishmaniasis normally produces skin ulcers on exposed parts of the body
• Cutaneous leishmaniasis lesions can leave ugly scars
• Mucocutaneous leishmaniasis can lead to partial or total destruction of the mucosa membranes
• Symptoms of Mucocutaneous Leishmaniasis

  • Nasal stuffiness
  • Runny nose
  • Bleeding of nose
  • Ulcer & erosion of mouth
  • Destructive inflammation of the mucosa of the nose
• Dogs can act as reservoirs of Leishmania parasites
• The incubation period for leishmaniasis is usually from 6 weeks to 6 months
• In the early stages of the disease, there is mild irregular fever accompanied by chills and sweating
• Enlargement of the spleen and liver is common in leishmaniasis
• Amastigotes can frequently be seen in pharyngeal and nasal secretions
• Diagnosis methods for Leishmaniasis

  • Clinical signs & symptoms
  • Bone marrow biopsy
  • Spleen or liver biopsy
  • Detecting amastigotes in smears
  • Culturing ulcer material
• Diagnosing Leishmaniasis can be difficult