Leishmania sp. is a protozoan parasite that is responsible for the disease Leishmaniasis. It is transmitted through female sandflies. Their primary hosts are vertebrates (humans). Leishmaniasis is the third most important vector-borne disease, and it is estimated that worldwide there are an annual 1.5 to 2 million cases, with up to 350 million people at risk of infection and disease.
There are multiple species of Leishmania sp. Those that are included are:
- Leishmania braziliensis
- Leishmania donovani
- Leishmania infantum
- Leishmania mexicanum
- Leishmania tropica
Vector: Female Sand flies. Phlebotomus spp. in Old World. Lutzomyia spp. in New World. Phlebotomus spp. generates other parasites as well.A sandfly takes a blood meal from a human, by doing so it is injecting the promastigote stage of the parasite into the human’s skin. The promastigotes are phagocytized by macrophages and then transformed into amastigotes inside macrophages. The amastigotes multiply within cells (including macrophages) of various tissues.
A nother sandfly will come and take a blood meal from the infected human and will ingest the macrophages infected with amastigotes. Within the fly, the amastigotes transform into promastigotes in the midgut and reproduce. This allows the cycle to repeat.
SymptomsEditFirst sign: A small erythema at the site where an infected sand fly has bitten and regurgitated parasites into the skin. Once infection is established, depending on the parasite species, host immunity, parasites will cause an inflammatory reaction that leads the erythema to develop into either cutaneous; muco-cutaneous; or visceral (Kala Azar) leishmaniasis.
- Leishmania braziliensis (Muco-cutaneous): Ulcerations of the nasal and bucal cavities (mouth, lips, gums). It is not self-limiting.
- Leishmania donovani (Visceral; anthroponotic): Kala Azar of internal organs. Causes a systemic infection; fever, fatigue, weakness, loss of appetite and weight loss. Enlarged spleen and swollen stomach are also signs. Fatal if left untreated.
- Leishmania infantum (Visceral; zoonotic): Common in Old World children and dogs. Similar to L. donovani, causes a systemic infection; fever, fatigue, weakness, loss of appetite and weight loss. Enlarged spleen and swollen stomach are also signs. Fatal if left untreated.
- Leishmania mexicanum (Cutaneous): Common in the New World; attacks and creates lesions on ears.
- Leishmania tropica (Cutaneous): Oriental sores. It is self-limiting; lasts several months. However, leaves permanent scarring.
Antimony-cointaining compunds (heavy metal) cures Leishmaniasis. However, a major side effect of the medication is severe neurological problems.
A study that was conducted in March 2002 in India registered the first oral drug, miltefosine, for the treatment of visceral leishmaniasis. The drug showed cure rates of up to 98%. Advantages to miltefosine; it does not require refrigeration, can be used to treat cases resistant to conventional antimony therapy. Disadvantages to the treatment; potential gastrointestinal side effects, and the medication is a potential teratogen (WHO).
A more recent study from 2011 determined a non-invasive method to diagnose visceral leishmaniasis. Researchers tried to detect Leishmania sp. antibodies and DNA in oral fluid samples which were collected using an Oracol device. The results of the study illustrated that utilizing oral fluid samples is equally effective compared to the gold-standard of extracting blood samples. The use of diagnostic tests using oral fluid is highly advantageous because these fluid samples are more simple to obtain in field conditions, and more importantly, easier to collect from children (Galai 3150-3153).
Galai, Yousr. "Diagnosis of Mediterranean Visceral Leishmaniasis by Detection of Leishmania Antibodies and Leishmania DNA in Oral Fluid Samples Collected Using an Oracol Device ." Journal of Clinical Microbiology. 49.9 (2011): 3150-3153. http://jcm.asm.org/content/49/9/3150.full?sid=2766773b-d55b-4c26-b403-a1156963912a
WHO. Leishmaniasis research on leishmaniasis. http://www.who.int/entity/leishmaniasis/research/en/