Leishmaniasis

History of Leishmaniasis

Leishmaniasis is a disease caused by the protozoa genus Leishmania, especially prevalent in tropical conditions, and is currently present in 98 countries globally, distributed in Europe, Africa, Asia and America1. Leishmaniasis is estimated to have about 900,000 to 1.7 million new cases annually, 90% of which are found in only 13 countries mostly spread in Asia, Africa and Latin America, while also estimated to cause about 200-300 deaths annually 1. The origin of Leishmaniasis has no specific particular date, but the available theories indicate that the disease evolved in the Mesozoic era, with the specific geographic area of origin remaining a matter of ongoing debate 2. The first theory of the origin of the disease suggests that the Leishmania parasite originated in the Palaearctic region, which is an expansive region touching on Europe, north Asia, Africa, the Himalayas and northern Arabia 1. The protozoan species was then introduced into the Nearctic region that covers North America and the highlands of Mexico during the Oligocene era 1. Around three million years ago, the protozoan species was then introduced into the Neotropical largely covering the low lands of Mexico, Central America and South America, as well as the Caribbean islands in the Pliocene era 2. Through climate change and increasing temperatures, the arboreal mammals became the major hosts of the parasite in the New World, resulting in the increased diversity of the parasite in the New World, compared to the Old World1.

On the other hand, the second theory holds that the origin of the parasite Leishmania was the Neotropical region, and the climate change and during this region led to the increasing hosts range adaptation as well as geographic isolation of the parasite 1. Therefore, the sloths became the first major vertebrate hosts of the parasite, after which the hosting change to porcupine the Eocene era1. It is from this region that infected porcupines then introduced the parasite to the Nearctic region, after which the transmission further went to the Palaearctic region around the Miocene era 1. 

The third theory of the origin of Leishmaniasis diseases holds that the disease originated simultaneously in two different regions, with some subgenus of the parasite emerging in Africa, while another subgenus emerging in South America 2. Considering that all the Old World species of the subgenus Leishmania were only found in Ethiopia and Kenya, it was reasoned that this subgenus originated in Africa1. Therefore, it is from Africa that the parasite was transmitted through rodents to the Nearctic region during the Eocene era 1. The entry of the parasite in Nearctic then may have led to the further speciation of the parasite to emerge with more species specific to this region. On the other hand, the subgenus Viannia of the parasite is reasoned to have originated in South America, considering that this species is only specific to the Neotropical region 2.

In this respect, the history of the Leishmaniasis diseases can be explained in very diverse theories that do not seem to hold a common notion. Nevertheless, based on the assertions of the three theories, the history of the Leishmaniasis diseases can be traced back to the supercontinent Gondwana, during a certain time period in the Mesozoic era 1.

Causes of Leishmaniasis

The Leishmaniasis disease is caused by the infection with Leishmania protozoan parasites 3. The infection majorly occurs in the form of an individual being bitten by the female phlebotomine sand flies 3. The phlebotomine sand flies are infected when they ingest blood meals from hosts that are infected with the parasite. Thus, when the infected phlebotomine sand flies then bites an individual, the protozoan parasite is transmitted from the fly at its infective stage to the individual’s body 4. Once in the bitten individual’s body, the parasites multiplies in the infected cells and goea ahead to affect the surrounding tissues, based on the exact region of the body where the bite occurs, and the specific type of the parasite infected 4. 

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The infection with the protozoan parasites causes three different types of the Leishmaniasis disease. The first category of the disease is the coetaneous leishmaniasis, which is a category of the disease that affects the skin 3. The second type of Leishmaniasis disease caused by the infection with protozoan parasite Leishmania is the visceral leishmaniasis, which does not show in the outward signs, but affects the internal body organs that may include the bone marrow, the spleen and the river. The third type of Leishmaniasis disease is the mucocutaneous leishmaniasis, which refers to the category that causes a total destruction of the mucous membrane of the affected individual’s nose, throat and mouth 4. The greatest percentage of the third category of the disease, over 90%, occurs in four countries namely Bolivia, Ethiopia, Brazil and Peru 4. 

Signs and Symptoms

The three different categories of the disease manifest different signs and symptoms.

Cutaneous leishmaniasis

The cutaneous leishmaniasis manifests the symptoms of sores and rushes on the skins, which then cracks open to project purple ulcers and lesions across the area of the skin where the infection is spread 3.  

An Image of cutaneous leishmaniasis; Source https://img.medscapestatic.com/pi/meds/ckb/18/37218tn.jpg

The diffuse cutaneous of the disease produces a widespread skin lesion that may resemble the lesion of a leprosy infection.  The surface of the skin remains with a large and unpleasant scar. Central scarring is common, with plaques, enlarge or coalescence papules also characterizing the infected region 5. There is also the tendency of the lesion and the ulcers to expand at the periphery as time passes by. 

Mucocutaneous leishmaniasis

The category of the disease is characterized by the excessive tissue obstruction of the nose and throat, as well as the continuous production of nares and membrane plaques of from the nose due to the continued and persistent destruction of the mucous membrane 3. Nasal, throat and mouth perforations are also common as the disease infection continues to advance. External changes to the structure of the nasal cavity also occurs, giving rise to the characteristic camel’s nose 5. The mouth of the infected individual also manifests the signs of ulceration, granulation and erosion of the lips and the pharynx, while bony structures around the nose and the throat projects conspicuously.  Other signs include hoarseness, gingivitis and periodontitis with occasional genital mucosal and optical lymphadenopathy under severe infection cases 4.  

Visceral leishmaniasis

The Visceral leishmaniasis category of the disease is characterized by pentad fever, weight loss, and darkening of the skin around the regions of the infection 3. Unproductive cough, abdominal tenderness, fatigue, intermittent diarrhea, malaise and myalgias, headache, and nausea, are also other common symptoms of this category of the disease 5.

Treatment 

The treatment of Leishmaniasis disease is tailored to the individual infection, category of disease and the signs and symptoms present, considering that the disease is caused by multiple species infections 3. The treatment of visceral leishmaniasis normally uses a single dose of liposomal amphotericin B, where the infection is in the regions of South America, the Mediterranean and India 4. Administering a single dose of amphotericin on patients infected in these regions proves to be highly successful, especially considering that the species in these areas are high resistant to medication. Nevertheless, the species in Africa are also resistant to medication, such that administering a dose of combined paromomycin  and pentavalent antimonials is effective in treating the symptoms of the disease in the region 3. The Miltefosine oral medication is also administered as treatment for the mucocutaneous disease cutaneous and visceral and leishmaniasis, although it should not be adminsistered to pregnant women because it can occasion serious side effects such as birth defects 5.  The other treatment medications administered based on the specific category of the disease and the specific parasite responsible for the infection include full doses of paromomycin, fluconazole or Pentamidine may not be full treatments for the disease, but can be effective for accelerating cure and hindering progression 3. Other common treatments normally offered for the disease include local heat therapies.

Prevention and Management

The prevention and management of the Leishmaniasis disease demands a combination of interventions. The disease is transmitted under a complex system of biological environment interactions between humans and their immediate surroundings of the animal hosts, the infectious sand fly and the human victims 4. 

Sleeping under nets treated with insecticides for individuals in the highly prone tropical areas for this infection is also a partial-preventive measure that can be taken against this disease. Insect control methods that include insecticide sprays to control the parasitic flies especially in the domestic environments is also another important preventive measure that should be taken against the Leishmaniasis disease infection 5. Additionally, the control of the animal reservoirs through proper disinfectant treatment is also important to prevent the possible transmission of the infectious parasitic fly from the animal hosts to human beings.  

The management of the Leishmaniasis disease is also important, in addition to the administered treatment. The critical aspects of management of the disease include controlling the infection and preventing further infections to the already affected and infected areas, especially on the surface of the skin 4. The treatment of other concurrent illnesses is also important, to boost the immunity and the recovery systems o the body, thus allowing the treatment to be more effective. Controlling malnutrition is equally important, because malnutritioned individuals are especially vulnerable to the parasitic infection symptoms 5. Effective disease monitoring and early treatment also effective management practices for the disease, because they serve to mitigate the spread of the disease from the early stages. 

Conclusion

Leishmaniasis is a disease caused by the infection of an individual by the protozoan parasite Leishmania. The disease is common in the tropical regions of Asia, Africa, Europe and America. The nature of the symptoms and disease occasioned by the infection depends specifically on the region of the infection, as well as the species of the parasitic Leishmania that has infected the individual. While there are varied medical treatments for this disease, the preventive and management practices are also very vital to ensure that the transmission of the disease is controlled from the very early stages. Therefore, domestic control of parasites through insecticides, sleeping under treated nets and the proper treatment of the animal shelters with disinfectant are some strategies of preventing the disease.