Leishmania tropica complex - Laboratory diagnosis, Treatment, Prevention, Control

Laboratory diagnosis of Leishmania tropica complex

The laboratory diagnosis of the Leishmania tropica complex begins with the collection of samples.

Specimen

The specimen for lab diagnosis of Leishmania tropica complex includes

• the outer edge of the ulcer aspirates

• a swab of ulcer margin

• skin biopsy from the ulcer margin

Microscopy

• stains such as Leishman stain, Giemsa stain, Brown-Hopps stain, or Wright stain can be used for microscopy

• presence of amastigotes confrims the diagnosis

Culture

This method of culture is followed in cases of Leishmaniasis recidivans and in cases suspected of cutaneous leishmaniasis but the parasites are not seen in direct microscopy of Leishmania tropica complex.

In-vitro culture

• media used for in-vitro cultures includes NNN, Schneider Drosophila medium, or any biphasic medium

• samples are inoculated into the water of condensation or into the fluid of a liquid medium

• incubated at 22° C - 26° C for 1-4 weeks

• at the end of each week, a drop of culture is microscopically examined for promastigotes

• motile promastigotes can be observed in positive cultures

• has a sensitivity of 75%

Animal inoculation

• laboratory animals such as Chinese and golden hamsters are inoculated intraperitoneally for animal inoculation

• skin biopsy, lesion aspirations are stained and visualized under a microscope

Serodiagnosis

Immunodiagnosis/serodingaosis methods for Leishmania tropica complex diagnosis such as Complement Fixation Test (CFT), Indirect Immuno-fluorescent (IFA), Enzyme-Linked Immunosorbent Assay (ELISA), and Direct Agglutination test (DAT) are not used in the diagnosis of cutaneous leishmaniasis due to low level of leishmanial antibodies in the serum.

Aldehyde test of Napier

Although a very useful test for the diagnosis of Leishmania donovani, Aldehyde test of Napier is negative and not useful in cutaneous leishmaniasis.

Leishmania skin test (Montenegro test)

Leishmania tropica complex infection can be diagnosed by the Leishmania skin test (Montenegro test).

• delayed hypersensitivity test and is helpful

• the antigen used in this method is obtained from killed cultured promastigotes of Leishmania tropica

• indicates positive results just a few days after the infection

• positive skin test results are also seen in treated cases as well as Leishmaniasis recidivans

• negative in cases of Diffuse cutaneous leishmaniasis

• 0.2 ml of Leishmania antigen is injected intradermally and read after 48-74 hours

• induration and erythema of 5mm diameter or larger are seen in positive cases

Treatment of Leishmania tropica complex

The treatment for Leishmania tropica complex infection involves:

• in endemic areas, treatment is not started until the ulcers develop as it induces the development of host immunity

• if the ulcers have been persisting for more than 6 months or the ulcers are disfiguring, they are treated with antimonial drugs

Drugs used include:

• Pentavalent antimonials

  megalumine antimonate

  sodium stibugluconate solution

• Pentamidine

  pentamidine isethionate

  pentamidine dimethane

• Amphotericin B

• Miltefosine

• Interferon

Prevention, Control of Leishmania tropica complex

The prevention, control of Leishmania tropica complex can be done by following methods:

• reduction of sand-fly population by using insecticides to reduce the source of Leishmania tropica complex

• evade contact with potential animal vectors such as dogs, foxes, and rodents

• use of bed nets, window nets, or insect repellents