A Case of Cutaneous Leishmania
This soldier, returning from his tour of duty in Afghanistan, has a case of cutaneous leishmaniasis. Cutaneous leishmaniasis in this geographic location is most likely caused by the species Leishmania tropica and the developmental forms seen in the smear are amastigotes. Amastigotes are the tissue form of the parasite and in this form can spread to other areas of the host body. Promastigotes are the motile forms of the parasite which are are found in the insect vector stage while the amastigote is found intracellularly in the vertebrate stage. Promastigotes utilize glucose as their primary source of energy and have a long flagellum for locomotion. The amasitigote are round to oval and utilize the amino acids and fatty acids as their carbon source.
The Vector
The vector of Leishmania tropica are species and subspecies of the sandfly Phlebotomus (sergenti species in this part of the world) which is considered the Old World. While in the New World the species and subspecies are transmitted by the Lutzomyia sandflies. Only the female sandfly bites are infectious.
Favorable Geographical and Environmental Conditions
Afghanistan is notoriously endemic for cutaneous leishmaniasis where environmental factors support the vector. The World Health Organization (WHO) has designated Kabul in Afghanistan as the epicenter of cutaneous leishmaniasis in the world. The presence of wild dogs and desert rodents provide excellent reservoirs for the parasite. Soldiers deployed in Afghanistan were strongly advised to not feed dogs around the encampment or have as pets for this very reason. The presence of favorable scrub vegetation and climate also provide an environment that favors the sandfly vector. Most settlements are in oasis areas with vegetation where the sandfly can be found rather then in the harsh desert where scrub vegetation is rare and thus not favorable for sandflies to flourish.
Leishmaniasis Forms Described
There are three forms of leishmaniasis. Cutaneous leishmaniasis (CL), visceral leishmaniasis (VL), and finally mucocutaneous leishmaniasis (MCL).
The three forms can be broken down further as CL being the most common of the leishmaniasis and having the ability to turn into VL by lymphatic spread. VL is the most severe form of leishmaniasis due to its propensity for visceral involvement. And finally MCL as being the most disfiguring of the leishmaniasis. CL will mainly involve the cutaneous skin tissue but as mentioned previously can progress to VL. VL is systemic with organ involvement such as the spleen and liver resulting in death if not treated. While MCL will involve the mucocutaneous tissues of the face (lips, mouth, nose) causing destruction of the tissue and thereby significant disfigurement that can lead to social stigma and life threatening secondary infections.
L. mexicana (New World) and L. tropica (Old World) are mainly responsible for cutaneous leishmaniasis. L. donovani is mainly responsible for visceral leishmaniasis. While L. braziliansis is mainly responsible for mucocutaneous leishmaniasis. This is a rather simplified description as there are numerous species and subspecies described for each Leishmania that are unique to specific geographic areas of the world.
Leishmaniasis Infective Process and Treatment
Leishmania have the ability to survive/live and replicate within the cells of the host immune system. Specifically the macrophages of the immune system. It does this by its ability to resist proteolytic degradation within the macrophage via proton pumps and acid phosphatases. Its location within the macrophages make cutaneous leishmaniasis difficult to treat and for it to easily spread to other sites. In the case of CL, eradication of infections may involve various treatment modalities that include topical ointments, cryotherapy, cutterage, and finally the use of pentavalent antimony which is toxic. Treatments may be lengthy with 21 days of painful intramuscular injections, 1-2 applications to lesions per week for 3-7 weeks. The effectiveness can be <50%. Sodium stibogluconate and meglumine are the drugs of choice and result in reversible though unpleasant side effects such as chemical pancreatitis, arthralgia, myalgia, headache, fatigue. There can be cardio toxicity that can lead to death.
Conclusion
The deployment of American troops to Afghanistan was expected to result in soldiers contracting leishmaniasis. Therefore the suspicion of CL is high in a soldier returning from Afghanistan presenting with a unsealing lesion. The Russian campaign in Afghanistan, prior to American involvement, resulted in heavy infections of soldiers to endemic diseases in Afghanistan resulting in the eventual withdrawal of the troops. The Russians were ill prepared for the infectious diseases endemic to the area. American troop deployment strategies included preparedness for infectious diseases to the area and leishmaniasis was proactively targeted. Active education, the availability of insect repellant, bed netting and other provisions were made available to minimize the risk of infection. This effectively reduced the incidence of infections in soldiers deployed in Afghanistan and other Middle East countries even with reported shortages of bed netting, insect repellent, and an initial emphasis on education.