- Phylum- Protozoa
- Sub-phylum- Plasmodroma
- Class- Mastigophora
- Sub-class- Zoomastigina
- Order- Protomonadina
- Genus- Leishmania
- Species- tropica
This parasite causes Oriental sore, also known as human skin Leishmaniasis which is distributed commonly in India, Pakistan, Central Africa, Iran and Iraq. The primary host of this protozoa is man or other mammal and the secondary host is sand-fly.
Life Cycle :
This species of Leishmania causes classical lesion of cutaneous leishmaniasis which is known as oriental sore. The tissue infection starts with the introduction of the leptomonas stage of the parasite into the dermis due to the bite of sand fly carrying leptomonas stage of this parasite. A wandering histiocyte in the vicinity picks up the parasite, which is soon changed to leishmania stage, multiplies and destroys the attacking macrophages resulting into the destruction of the tissue in the surrounding area. The destruction of cells starts in the centre of the lesion which becomes necrotic and the margins containing parasitized macrophages may become infiltrated with a giant and plasma cells.
The lesion appears first as a macula, and then a papule with a slightly raised centre covered with a thin blister like layer of epidermis. The lesion now bursts with the discharge of a small amount of clear or purulent exudate. At its base in the dermis, a granulating layer is formed and the margin becomes hard by infiltrating of fibroblasts. If there occurs bacterial or any other infection, an open frequently verrucous disfiguring ulcer develops. But if there is no secondary infection, it tends to dry up and the leishmaniasis slowly disappears with a slightly raised, depigmented wound at the site. Primarily there is only one ulcer for each infected sand fly bite at or near the point of inoculation on the exposed skin. Sometimes multiple new sores are formed from accidental autoinoculation if ulcers are open. The incubation period may vary from 2 weeks to 3 years but commonly it is for a period of 2 to 6 months.
Prevention and control :
This disease may be prevented by avoiding the bite of sand fly but of course it may not be practised properly by the persons of very poor economic community. It is very interesting to note that the preventive inoculation was first employed against oriental sore. Mothers in ancient time deliberately get infected their children with material from active sores in order to prevent the later acquisition of a disfiguring facial ulcer. The relationship between this age old practice and the modern use of vaccination is well known in the medical history.
The resulting ulcers should not be terminated chemotherapeutically for a period of about 30 days of inoculation, otherwise immunization will not be satisfactory. Dog reservoirs should be destroyed. The sand flies should be killed by any method, around the human habitat.
Leishmania tropica can be treated readily with chemotherapy :
- Antimony tartrate should be applied locally after removal of scab and crusts to heal ordinary ulcers.
- Atebrin and berberin sulphate should be injected around sores.
- In case of secondary infection of ulcers, penicilline, bacitracin or other latest antibiotics should be injected.
- To avoid secondary infection regular cleaning and dressing of boils should be practiced.
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