Leishmaniasis Flashcards
Leishmaniasis is Neglected Disease
Leishmaniasis is a globally important but neglected disease, affecting approximately two million people every year. For most people, infection results in a slow-to-heal skin ulcer. In others, however, the parasite targets the liver, spleen and bone marrow, leading to over 70,000 deaths annually.
The Parasite
Phylum Sarcomastigophora
Order Kinetoplastida
Family Trypanosomatidae
Genus Leishmania
Types of Leishmania Parasites and Diseases
Skin:Cutaneous leishmaniasis
* Leishmania tropica
* Leishmania major
* Leishmania aethiopica
* Leishmania mexicana
Skin and mucous membrane: Mucocutaneous leishmaniasis
* Leishmania braziliensis
Organs:
Visceral leishmaniasis e.g
* Leishmania donovani
* Leishmania infantum
* Leishmania chagasi
Morphology
Promastigote (flagellated)
Amastigote (non-flagellated)
Morphology and Life Cycle of Amastigotes
Amastigotes
* measure 2-3 micrometers, with a large nucleus and Kinetoplast.
Amastigotes mainly live within cells of the RE system, but have been found in nearly every tissue and fluid of the body.
Endemic in Saudi Arabia
Leishmania donovani
Leishmania infantum
Leishmania tropica
Leishmania major
Life cycle of Amastigotes
The organism is transmitted by the bite of several species of blood- feeding sand flies (Phlebotomus) which carries the Promastigote in the anterior gut and pharynx. It gains access to mononuclear phagocytes where it transform into Amastigote and divides until the infected cell ruptures.
The released organisms infect other cells. The sand-fly acquires the organisms during the blood meal, the Amastigote transform into flagellate Promastigote and multiply in the gut until the anterior gut and pharynx are packed. Dogs and rodents are common reservoirs.
What is Kala-Azar
Kala-azar means dark pigmentation which is characteristic of cases of visceral leishmaniasis. It is caused by Leishmania donovani bodies and may be present either in endemic, epidemic or sporadic forms. It is widely prevalent in India in epidemic form in states of Bihar, Assam and Bengal. Kala azar found in East and North Africa is a disease of young children and young adults, being more common in males as compared to females.
Clinical types of cutaneous leishmaniasis
Leishmania major: Zoonotic cutaneous leishmaniasis: wet lesions with severe reaction
Leishmania tropica: Anthropologic cutaneous leishmaniasis: Dry lesions with minimal ulceration
Oriental sore (most common) classical self-limited ulcer
How is it transmitted
KALA AZAR
Leishmaniasis is a disease caused by protozoan parasites of to the genus Leishmania and is transmitted by the bite of sand fly.
This disease is also known as kala azar, black fever, sandfly disease, Dum-Dum fever.
Human infection is caused by about 21 of 30 species that infect mammals. These include the L. donovani complex with three species (L. donovani,
L. infantum, and L. chagasi
Uncommon types
Diffuse cutaneous leishmaniasis (DCL):
Caused by L. aethiopica, diffuse nodular non- ulcerating lesions. Low immunity to Leishmania antigens, numerous parasites.
Leishmaniasis recidiva (lupoid leishmaniasis):
Severe immunological reaction to Leishmania antigen leading to persistent dry skin lesions, few parasites.
Post Kala-azar Dermal Leishmaniasis
Post Kala-azar Dermal Leishmaniasis (PKDL) is a condition when Leishmania donovani invades skin cells, resides and develops there and manifests as dermal leisions. Some of the kala-azar cases manifests PKDL after a few years of treatment. Recently it is believed that PKDL may appear without passing through visceral stage.
Pathogenesis
Infections range from asymptomatic to progressive, fully developed kala-azar.
Incubation period is usually 2 – 4 months.
Symptoms – Begins with low-grade fever and malaise, followed by progressive wasting, anemia, and protrusion of the abdomen from enlarged liver and spleen.
Fatal after 2 – 3 years if not treated.
In acute cases with chills, fevers up to 104 degrees Fahrenheit, and vomiting; death may occur within 6 – 12 months.
Immediate cause of death is usually an invasion of a secondary pathogen that the body is unable to combat.
Life cycle
- The sandflies inject the infective stage (i.e., promastigotes) from their proboscis during blood meals
- Promastigotes that reach the puncture wound are phagocytized by macrophages
- Promastigotes transform in these cells into the tissue stage of the parasite-amastigotes detrying the infected cells and being released
- multiply by simple division and proceed to infect other mononuclear phagocytic cells and amastigote infects other cells
- Sandflies become infected by ingesting infected cells during blood meals
- they are ingested into the midgut
- amastigotes transform into promastigotes, develop in the gut
- they migrate to the proboscis
