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.
What is the Parasite causing the disease and its taxonomy? (Mostly phylum and species)
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 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.
- flagella is absent
Which species of Leishmania are Endemic in Saudi Arabia?
Leishmania donovani
Leishmania infantum
Leishmania tropica
Leishmania major
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 of kala azar
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, destroy the macrophage and are then 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 anterior gut and pharynx
- they migrate to the proboscis
Dogs and rodents are common reservoirs.
L. tropica
Host and Clinical features?
Host: Dogs
CF: Oriental sore(Baghdad
boil)
L. major
Host and Clinical features?
Host: Gerbils, desert rodents
CF: Rapid necrosis, wet sores
L. aethiopica
Host and Clinical features?
Host: Hydraxes
CF: Solitary facial lesions with satellites
Diagnosis of Cutaneous leishmaniasis
Smear: Giemsa stain – microscopy for LD bodies (Amastigote)
Biopsy: microscopy for LD bodies or culture in NNN medium for promastigotes
What type of specimen is used for diagnostic testing?
L. donovani bodies may be demonstrated in buffy coat preparations of blood and bone marrow aspirate.
Aspirates taken from enlarged lymph nodes show parasites in 60 percent of cases.
Diagnosis of Visceral leishmaniasis
What specimen is used for diagnotic testing?
Microscopy and culture in NNN medium
Specimen:
Bone marrow aspirate Splenic aspirate
Lymph node
Tissue biopsy
Diagnostic Methods in Leishmaniasis include:
Antibody detection. Specific sero diagnostic tests are also employed. Conventional methods include gel diffusion, complement fixation test, indirect haem agglutination test, indirect immuno-fluorescent antibody test (IFAT) and counter immuno electro phoresis. Most of these tests have limited sensitivities and specifies.
Culturing of the Parasite
Organisms can be cultured in Nicolle- NovyMacneal (NNN media) media from clinical specimens obtained from splenic or bone marrow aspirates.
Immunological Diagnosis
Specific serologic tests: Direct Agglutination Test (DAT), ELISA, IFAT
Skin test (leishmanin test) for survey of populations and follow-up after treatment.
Non specific detection of hypergammaglobulinaem by formaldehyde (formal-gel) test or by electrophoresis.
Direct agglutination test
Direct agglutination test (DAT) based on agglutination of the trypsenized whole promastigotes is useful in endemic regions. Its sensitivity ranges from 91-100% and specificity from 72 to 100%.
ELISA
ELISA is an important sero diagnostic tool for leishmaniasis. It is a highly sensitive test and its specificity depends upon the antigen used.
Chromatographic strip test
A ready to use immuno chromatographic strip test based on rk 39 antigen has been developed as a rapid test for diagnosis of kala azar. An important limitation of this test is the presence of antibodies in healthy controls hailing from endemic regions.
Treatment
Pentavalent antimony (Pentostam)
Amphotericin B
Treatment of complications:
Anemia
Bleeding
Infections etc.
Management of Kala-azar Patients
It includes both supportive and curative. All patients of Kala azar should preferably be hospitalized. Any infection complicating the disease be treated by use of proper antibiotics. Nutrition must be maintained. Cases with severe anemia may require blood transfusions. Pentavalent antimony compounds are the drug of choice. Sodium antimony gluconate (Pentostam) is the most commonly used drug.
Kala-azar prevention
Multipronged approach is needed.
Sand-flies are extremely sensitive to insecticides & vector control through insecticide spray is very important.
Mosquito nets or curtains treated with insecticides will keep out the tiny sand-flies.
In endemic areas with zoonotic transmission, infected or stray dogs should be destroyed.
In areas with anthroponotic transmission, early diagnosis & treatment of human infections, to reduce the reservoir & control epidemics of VL, is extremely important.
Serology is useful for screening of suspected cases in the field.
No vaccine is currently available .
