Kala-Azar is a slow progressing indigenous disease caused by a protozoan parasite of the genus Leishmania. The parasite primarily infects the reticulo-endothelial system and may be found in abundance in bone marrow, spleen and liver.
Post Kala-Azar Dermal Leishmaniasis (PKDL)
Post Kala-Azar Dermal Leishmaniasis is a condition in which Leishmania donovani parasites invades in skin cells. The parasite resides and develops there and manifests as dermal lesions. Recently it is believed that PKDL may appear without passing through visceral stage. However, adequate data is yet to be generated on course of PKDL manifestation.
Recurrent fever intermittent or remittent with often double rise of temperature.
- Loss of appetite, pallor and weight loss with progressive emaciation
- Skin – Dry, thin and scaly and hair may be lost. Light colored person show grayish discoloration of the skin of hands, feet, abdomen and face which gives the Indian name Kala-Azar meaning “Black fever”.
- Anemia – develops rapidly
- Splenomegaly – spleen enlarges rapidly to massive enlargement, usually soft and non-tender.
- Liver – enlargement not to the extent of spleen, soft, smooth surface, sharp edge.
There is only one sand fly vector of Kala-Azar in India i.e. Phlebotomus argentipes. Sand flies are small insects, about one fourth of the size of a mosquito. The length of a sand fly body ranges from 1.5 to 3.5 mm.
Sand flies breed in high relative humidity, warm temperature, high subsoil water and abundance of vegetation. Sandflies breed in favourable micro-climatic conditions in places with high organic matter that serve as food for larvae.
These are ecologically sensitive insects, fragile and cannot withstand desiccation.
A case of fever of more than two weeks duration not responding to anti-malarials and antibiotics. Clinical laboratory findings may include anemia, progressive leucopenia thrombocytopenia and hypergammaglobulinemia.
- Serology tests: A variety of tests are available for diagnosis of Kala-azar. The most commonly used tests based on relative sensitivity; specificity and operational feasibility include Direct Agglutination Test (DAT), rk39 dipstick and ELISA. However all these tests detect IgG antibodies that are relatively long lasting. Aldehyde Test is commonly used but it is a non-specific test. IgM detecting tests are under development and not available for field use.
- Parasite demonstration in bone marrow/spleen/lymph node aspiration or in culture medium is the confirmatory diagnosis. However, sensitivity varies with the organ selected for aspiration. Though spleen aspiration has the highest sensitivity and specificity (considered gold standard) but a skilled professional with appropriate precautions can perform it only at a good hospital facility.
Diagnosis and treatment of Kala-Azar are problematic because of a variety of reasons. While treatment is lengthy and relatively costly, definitive diagnosis of Kala-Azar requires tissue specimens, which are conventionally obtained by organ needle aspiration for microscopic demonstration of amastigote forms in stained smears. Bone marrow the spleen, and lymph-node (in some regions) are the tissues most often sampled in patients with suspected infection. The diagnostic sensitivity of splenic aspiration is high (95% – 98%), but the procedure carries a risk of bleeding; the sensitivity of examination of bone marrow specimens is considered to be lower (53% – 95%). Organ aspiration and accurate examination of smears also require technical skills that are not uniformly available in rural areas. Culture or PCR testing of aspirate material improves parasitologic yield, but these methods are seldom undertaken outside of research laboratories.
There are no vaccines or preventive drugs for visceral leishmaniasis. The most effective method to prevent infection is to protect from sand fly bites. To decrease the risk of being bitten following precautions are suggested:
-Avoid outdoor activities, especially from dusk to dawn, when sand flies generally are the most active. When outdoors (or in unprotected quarters): Minimize the amount of exposed (uncovered) skin. To the extent that is tolerable in the climate, wear long-sleeved shirts, long pants, and socks; and tuck your shirt into your pants.
-Apply insect repellent to exposed skin and under the ends of sleeves and pant legs. Follow the instructions on the label of the repellent. The most effective repellents generally are those that contain the chemical DEET (N,N–diethylmetatoluamide)
-Stay in well-screened or air-conditioned areas.
-Keep in mind that sand flies are much smaller than mosquitoes and therefore can get through smaller holes.
-Spray living/sleeping areas with an insecticide to kill insects. If you are not sleeping in a well-screened or air-conditioned area, use a bed net and tuck it under your mattress.
-If possible, use a bed net that has been soaked in or sprayed with a pyrethroid-containing insecticide. The same treatment can be applied to screens, curtains, sheets, and clothing (clothing should be retreated after five washings).”