The common associated diseases and condition names are Visceral Leishmaniasis, Kala Azar or Dum Dum Fever.The Leishmania donovani complex of organisms is found in India, Pakistan, Thailand, Africa, the People’s Republic of China, the Mediterranean region, Europe,the Middle East, parts of the former Soviet Union,Yemen, Oman, Iraq, Kuwait, Saudi Arabia, United Arab Emirates, Bahrain and Central and South America.This group consists of Leishmania donovani, Leishmania infantum and Leishmania chagasi.This Leishmanial complex and the diseases for which its organisms are the pathogens can also be called the Old or New World, depending on the geographical location of the Leishmania species involved.
General Morphology of Hemoflagellates
The genera Leishmania and Trypanosoma include members of the clinically significant group of parasites that are found in blood and tissue and move by means of flagella, the so-called hemoflagellates.
There are four morphological forms of clinical importance associated with these hemoflagellates: Amastigote, Promastigote, Epimastigote and Trypomastigote. Trypomastigote is only present in the trypanosome
The average round to oval amastigote has a size of 5 x 3 µm.The amastigote contains a core, a basal body structure (called blepharoplasty) and a small parabasal body.The large single nucleus is typically located outside the centre and is sometimes more at the edge of the organism.The punctiform blepharoplasty leads to an axoneme and is attached to it.The axonem extends to the edge of the organism.The single parabasal body is located next to the blepharoplasty.Kinetoplast is an umbrella term often used for blepharoplasty and the small parabasal body.
|Size||5 by 3 µm|
|Shape||Round to oval|
|Nucleus||One, usually off center|
|Other features||Kinetoplast present, consisting of dotlike blepharoplast from which emerges a small axoneme Parabasal body located adjacent to the blepharoplast|
The typical promastigote is 9 to 15 µm long. The large single core is located in or near the center of the long, slender body. The kinetoplast is located at the front end of the organism. A single free flagellum extends forward from the axonema.
|Size||9-15 µm long|
|Appearance||Long and slender|
|Nucleus||One, located in or near center|
|Other features||Kinetoplast, located in anterior endSingle free flagellum, extending from anterior end|
The average epimastigote has a length of about 9 to 15 µm.The body is slightly wider than that of the promastigote.The large single nucleus is located at the rear end of the organism.The kinetoplast is located anterior to the nucleus.An undulating membrane, half the length of the body, forms a free flagellum at the anterior end of the epimastigote.
|Size||9-15 µm long|
|Appearance||Long and slightly wider than promastigote form|
|Nucleus||One, located in posterior end|
|Other features||Kinetoplast located anterior to the nucleus.Undulating membrane, extending half of body length.Free flagellum, extending from anterior end.|
The typical Trypomastigote is 12 to 35 um long and 2 to 4 um wide and can often take the form of the letters C, S or U in coloured blood films.The Trypomastigote is presented in its straight form for comparison purposes, as it clearly identifies the individual structures.The long, thin organism is characterized by a kinetoplast located in the posterior position from which emerges an undulating membrane covering the entire length of the body.The single large nucleus is in front of the kinetoplast.An anterior free flagellum may or may not be present.
|Size||12-35 µm long by 2-4 µm wide|
|Shape||C, S or U shape often seen in stained blood films|
|Appearance||Long and slender|
|Nucleus||One, located anterior to the kinetoplast|
|Other features||Kinetoplast located in the posterior end. Undulating membrane, extending entire body length.Free flagellum, extending from anterior end when present .|
Life Cycle of Leishmania donovani complex
The life cycle of the members of the Leishmania Donovani complex is identical to that of Leishmania braziliensis, with only two exceptions.First, the specific sandfly species responsible for the transmission of Leishmania Donovani varies with each of the three subspecies .
Secondly, Leishmania donovani mainly affects the infected human visceral tissue (visceral disease).
|Subspecies||Geographic Distribution||Vector||Reservoir Hosts|
|Leishmania donovani chagasi||Central America, especially Mexico, West Indies, South America||Lutzomyia sandfly||Dogs, cats, foxes|
|Leishmania donovani donovani||Parts of Africa, India, Thailand, People’s Republic of China, Burma, East Pakistan||Phlebotomus sandfly||India, none; China, dogs|
|Leishmania donovani infantum||Mediterranean Europe, Near East, Africa; also in Hungary; Romania, southern region of former Soviet Union, northern China, southern Siberia||Phlebotomus sandfly||Dogs, foxes, jackals, porcupines|
Clinical symptoms of Leishmania donovani complex
Patients with visceral (in the body’s internal organs) leishmaniasis, also known as kala-azar or dum dum fever, often have undescribed abdominal disease and hepatosplenomegaly (spleen and liver enlargement).
Early stages of disease can be similar to malaria or typhoid fever when fever and chills develop.The onset of these symptoms is gradual and takes a period of incubation from 2 weeks to 18 months.
Diarrhea and anemia can often be present.Additional symptoms, including weight loss and weight loss, tend to occur after a parasitic invasion of the liver and spleen.In contrast to a rare papule, which most probably occurs at the bite site, skin lesions are absent.
Advanced stages of the disease lead to kidney damage (e.g. glomerulonephritis, inflammation of the renal glomeruli) and granulomatous skin areas.
A characteristic darkening of the skin is recognizable.This symptom is called Kala Azar or kala azar symptoms, which means black fever (black sick).Chronic cases usually lead to death after 1 to 2 years, whereas acute diseases weaken the patient and lead to death within a few weeks.
Laboratory Diagnosis of Leishmania donovani complex
The Montenegro skin test is a similar screening test to the tuberculin skin test (tuberculosis); it is used to screen large populations at risk for Leishmania spp infections. Its reliability in detecting exposure to the organisms causing leishmaniasis is related to the patient’s disease status.It is not a good diagnostic method for active disease.
Blood slides stained with Giemsa, bone marrow, lymph node aspirates and biopsies of the infected areas are better choices for diagnostic amastigote forms.
Some people consider the sternal marrow aspirate to be the specimen of choice, but the organism can be seen in Giemsa-buffy coat films made from venous blood, a safer, less invasive procedure.
Blood, bone marrow and other tissues may also be cultured; these samples frequently show promastigote forms.
IFA (indirect fluorescent antibody), ELISA (enzyme-linked immunosorbent test) and DAT (direct agglutination test) are available for serological testing.
Furthermore, schizodemic analysis, zymodeme analysis and nuclear DNA hybridization are primarily available on a research basis, which may become a more popular method of leishmaniasis diagnosis in future.
Treatment of Leishmania donovani complex infections
- The drug of choice for the treatment of visceral leishmaniasis is Liposomal amphotericin B (ambisome).
- Sodium stibogluconate (Pentostam) is also an effective treatment for Leishmania donovani complex infections, but organisms in India and the Mediterranean have demonstrated resistance.
- Successful treatment with gamma interferon in combination with pentavalent antimony has been carried out.
- Infected patients with AIDS seem to have a good response to allopurinol.It is also recommended that people with HIV receive secondary prophylaxis in their treatment plan.
Prevention and Control Leishmania donovani complex infections
- Protection from repellents, protective clothing and screening are essential measures to reduce future complex infections in Leishmania donovani.
- The prompt treatment of human infections and the control of the sandfly population and hosts in the reservoir will also help to stop the spread of the disease.
Notes of Interest and Emerging Trends
It is important to know that Leishmania donovani can be transferred from person to person through blood transfusions.Special concern about this type of transmission of leishmaniasis arose during and after the Gulf War.It remains a concern today due to the number of members of the armed forces serving in the Persian Gulf region.Persons in and around this region have been or are at risk of contracting the disease.The potential of those in the area to contract these organisms and bring them home has led to the postponement of people who have been there for at least 12 months after their departure.
Research was conducted to investigate persistent concentrations of galactosyl-alpha (1 – 3) galactose antibodies in patients successfully treated for visceral leishmaniasis.It is suspected that these high levels indicate the presence of parasite remains, which remain even after the disease has been cured.Further studies on this mystery could provide scientists with additional valuable information for understanding and treating Leishmania donovani.