Leishmania donovani (infantum)

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Leishmania donovani (infantum)

Location and host

These parasites are found in skin, liver, spleen of human, dog, fox, black rat, raccoon, jackal, wolf
Vector: sand flies (Phlebotomus spp. )

Morphology

Amastigotes are small, round or oval shaped bodies, measuring 1.5-3 x 2.5-6.5 µm.
Possess large nucleus and rod shaped kinetoplast associated with rudimentary flagellum

Life cycle

Pathogenesis

Disease caused by this species is called ‘kalazar’ or ‘Dum dum fever’ in man
After promastigote forms are injected in skin capillary by sand flies, local reaction takes place
Infiltration of large number of macrophages resulting in formation of papillae on the skin
Macrophages engulf the promastigote form in which leishmanial stage is formed. Through way of macrophages, they reach to different organs of body such a liver, spleen, lymph gland and bone marrow.

Note: Malaise: General feeling of discomfort, illness or unease whose exact cause is difficult to identify.

Growth and multiplication of parasites in these organs which results in impairment of their function.
Visceral leishmaniasis occurs from this process and progress to cutaneous leshmaniosis but not vice-versa.
Incubation period is 3-6 months, 1-2 years in some cases.
Hematopoietic process gets hampered leading to anemia, leucopenia with neutropenia and thrombocytopenia.
Hypoproteinemia, reduced immunity and muscle wasting can also be seen.
Macrophages , myelocytes and neutrophils of bone marrow are filled with parasites. These are called ‘Leishman donovan’ bodies (LD).

Clinical signs

In human

Irregular fever followed by headache, malaise, abdominal pain, dysentery or diarrhea.
Bleeding of mucous membrane of mouth and nostrils.
Skin becomes dark with brittle hairs
In advanced cases, there is ulceration of digestive tract, with enlargement of liver and spleen.
Recovered case after treatment show whitish spots as lentil-sized nodules in skin, particularly on face and neck.
These nodules are called post kala-azar dermal leis monoids (PKADL). These contains numerous leishmanial organisms which results in premunition state giving life-long immunity in donovanl infection in man.

Note: Cachexia: ‘Wasting’ disorder that causes extreme weight loss and muscle wasting and can include loss of body weight.

In Dog

In cutaneous form, lesion is confined to shallow skin ulcers often on lip or eyelid.
In visceral form, dog initially develop ‘spectacles’ due to depilation of hair around eyes. It is followed by generalized loss of body hair and eczema.
Typical signs include: Intermittent fever, anemia, cachexia, generalized lymphadenopathy.

Diagnosis

Demonstration of amastigote parasites in smears or scrapings from affected skin, lymph nodes or marrow biopsies.
Intracellular or extracellular amastigotes can be identified in Giemsa or Leishman’s-stained aspirates, impression or biopsy samples from L.N, bone marrow, spleen or skin lesions.
Serological test : IFAT, ELISA and western blot
PCR

Treatment

In dogs

Meglumine antimoniate @ 100 mg/kg subcutaneous for 3-4 weeks.
Allopurinol @ 20 mg/kg orally daily or combined with meglumine antimoniate and then continue with 20 mg/kg, allopurinol indefinitely.
Amphotericin @0.5-0.8 mg/kg, IV or SC, 2-3 times weekly.

Control

Destruction of infected dogs/ stray dogs from public health aspect but it is not acceptable.
Control of sand flies population, though chemical control has limited success.
Impregnated collar offers some protection of dogs from sandfly bites.
Sub-unit vaccine has been developed in south America. Vaccine is based on surface fructose-mannose-ligand antigen complex.
Parasite lyophilizate vaccine ( caniLesh) is available commercially in Europe for immunization of dogs. These vaccines contain excretory / secretory proteins of “Leishmania infantum’.