Leishmaniasis Life Cycle and Effective Prevention Tips
Leishmania major is a parasitic genus of parasitic parasites that are linked to the disease zoonotic cutaneous leishmaniasis. L. major is an intracellular pathogen that infects the immune system's macrophages and dendritic cells. It is popularly referred to as oriental sore or kala-azar. After 2–4 weeks, an oriental sore or localised Cutaneous Leishmania occurs on the site of the sandfly bite or an insect bite. Let us explore more about oriental sore, their types of diagnosis, treatment and preventive methods.
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Life Cycle of Leishmania
Leishmania is a genus of flagellate protists in the Kinetoplastida order that includes many species. These parasitic protists are transmitted to vertebrates by species of Phlebotomus, a genus of blood-sucking sand flies. The leishmanial parasites exist in two forms- a round or oval leishmanial stage that lives and multiplies in the vertebrate host, and a leptomonad, an elongate, motile, flagellated organism found in the sand fly's alimentary tract. The species are taken in with the fly's meal in their leishmanial stage, where they turn into leptomonads and multiply in the fly's stomach. They finally migrate to the mouthparts of the fly, where the leptomonads enter the wound created during the next feeding, causing a new infection.
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The trypanosomatid Leishmania major starts its life cycle in the midgut of the main vector, female sand flies, as an amastigote. The parasites transform from flagellated amastigotes to flagellated promastigotes in the gut of the sand fly for 1–2 weeks until they are fully grown, at which point they make their way to the proboscis.
Promastigotes are released into the bloodstream after biting a mammalian host, where they are engulfed by macrophages. Promastigotes differentiate into amastigotes after being engulfed. Amastigotes are oval or circular, with a diameter of 2 to 3 metres. They also have a big, eccentrically positioned nucleus as well as a kinetoplast that holds extracellular DNA.
The amastigotes reproduce by binary fission, a mechanism that allows them to survive the acidic environment within macrophage phagosomes. The amastigotes are then released into the body, where they can be consumed by female sand flies, completing the cycle. The sexual cycle of L. major includes a meiotic phase. The sand fly vector is the only species that mates, making it more harmful and dangerous with each multiplication.
The genus Leishmania contains three distinct species, each of which causes three distinct human diseases known as leishmaniasis. L. In Africa, Europe, and Asia, donovani causes kala-azar by attacking the liver, spleen, bone marrow, and other viscera. L. Oriental sore is caused by tropical diseases. On the skin of the hands, feet, legs, and face in Africa, Europe, and the East, lesions ranging from pimples to massive ulcers type. L. brasiliensis, which causes American leishmaniasis in Central and South America, cause similar skin lesions as well as deeper oral and nasal mucous membrane lesions.
Types of Oriental Sore or Leishmaniasis Infections
Diagnosis
Characteristic symptoms and signs, a comprehensive case history, a thorough clinical examination, and a number of specialised tests are used to diagnose leishmaniasis. A thorough case history will reveal whether or not the patient has travelled to places where the disease is prevalent. A non-healing or progressive skin lesion in a person who has travelled to or resided in an area where leishmaniasis is found, for example, should always be considered cutaneous leishmaniasis.
Infected tissue samples are taken by doctors to be analysed. They can take a biopsy or scraping samples from skin lesions if cutaneous leishmaniasis is suspected, or from bone marrow if visceral leishmaniasis is suspected. The antibody test is only for the case of visceral leishmaniasis and not cutaneous or mucosal.
Treatment of Different Types of Leishmaniasis
Cutaneous leishmaniasis can recover on its own, but it takes a long time and sometimes results in scarring. For small, uncomplicated lesions, treatment can involve applying heat or cold to the sores to kill the parasites or applying an antibiotic called paromomycin as an ointment directly to the sores.
Treatment options for people with cutaneous leishmaniasis include liposomal amphotericin B, miltefosine, or sodium stibogluconate if they have many large skin lesions, a compromised immune system, or are infected with Leishmania species that may cause mucosal leishmaniasis.
For mucosal leishmaniasis, the best treatment choice is unknown. Liposomal amphotericin B, miltefosine, and sodium stibogluconate have also been used to treat this disease. For people with serious complications of the mouth and nose mucous membranes, surgery may be needed (orofacial surgery).
Treatment for HIV infection with antiretroviral therapy can improve the response to antileishmanial treatment, prevent or postpone leishmaniasis relapses, and improve overall survival in people with both leishmaniasis and HIV.
Prevention At Home
Stay in places that are well-screened or air-conditioned.
Be aware that Sandflies are much smaller than mosquitoes, so they can fit into smaller gaps to avoid even a tiny passage of entry.
To kill insects, spray the living/sleeping areas with an insecticide.
Use a bed net and tuck it under your mattress if you are not sleeping in a well-screened or air-conditioned area.
Using a bed net that has been soaked in or sprayed with a pyrethroid-containing insecticide if at all necessary. Screens, curtains, and sheets should all be used in the same way, and clothes can retreat after five washes.
Conclusion
People of all ages are at risk of contracting leishmaniasis if they reside or work in areas where the disease is present. Leishmaniasis is more common in rural areas than in towns, but it can be found on the outskirts of some cities. Since sand flies are most active from dusk to dawn, the risk of transmission is greatest during this period. Adventure travellers, ecotourists, Peace Corps volunteers, missionaries, soldiers, ornithologists (people who specialise in the study of birds), and other people who do research (or are active) outdoors at night/twilight are examples of people who may be at an increased risk for infection (especially with the cutaneous form). Even though adventurous and outgoing people are at risk, care and prevention must be practised by everybody.
FAQs on Leishmaniasis: Symptoms, Causes, and Treatment
1. What is leishmaniasis and which organism is responsible for causing it?
Leishmaniasis is a parasitic disease caused by a protozoan parasite of the genus Leishmania. It is not a virus or bacterium. The disease is transmitted through the bite of an infected female phlebotomine sandfly, which acts as the vector. The parasite exists in two forms: the amastigote in the vertebrate host and the promastigote in the sandfly's gut.
2. What are the main types of leishmaniasis, and how do their symptoms differ?
There are three primary forms of leishmaniasis, each with distinct symptoms:
- Cutaneous Leishmaniasis: This is the most common form, causing skin sores or ulcers at the site of the sandfly bite. The sores can be painless or painful and may leave permanent scars.
- Visceral Leishmaniasis (Kala-azar): This is the most severe form and can be fatal if untreated. It affects internal organs like the spleen, liver, and bone marrow, leading to symptoms like fever, weight loss, anaemia, and enlargement of the spleen and liver.
- Mucocutaneous Leishmaniasis: A rarer form where the infection spreads from the skin to the mucous membranes of the nose, mouth, and throat, causing partial or total destruction of the tissues.
3. How is the Leishmania parasite transmitted to humans?
The transmission cycle begins when a female sandfly bites an infected animal or human, ingesting blood containing the amastigote form of the parasite. Inside the sandfly's gut, these transform into the motile promastigote form and multiply. When the infected sandfly bites another person, it injects these promastigotes into the new host's skin, initiating a new infection.
4. What are the most effective ways to prevent sandfly bites and reduce the risk of leishmaniasis?
Currently, there is no vaccine for leishmaniasis. Prevention focuses on avoiding sandfly bites, especially during their most active times from dusk to dawn. Key measures include:
- Using insect repellent containing DEET on exposed skin.
- Wearing long-sleeved shirts, long pants, and socks to minimise skin exposure.
- Sleeping in screened areas or using bed nets treated with insecticide.
- Avoiding outdoor activities in endemic areas during peak sandfly activity hours.
5. Why is visceral leishmaniasis, or Kala-azar, considered the most severe form of the disease?
Visceral leishmaniasis is the most severe form because the parasite does not remain at the skin but migrates to and attacks vital internal organs, primarily the spleen, liver, and bone marrow. This systemic infection disrupts critical bodily functions, including the production of blood cells (leading to anaemia and susceptibility to other infections) and the proper functioning of the liver and spleen. If left untreated, the massive enlargement of these organs and damage to the immune system are almost always fatal.
6. How does the Leishmania parasite manage to survive and multiply inside the human body's immune cells?
The Leishmania parasite has a remarkable survival strategy. Upon being injected into the skin, it is quickly engulfed by immune cells called macrophages, which are designed to destroy pathogens. However, instead of being destroyed, the parasite transforms into the amastigote form, which is resistant to the macrophage's digestive enzymes. It then multiplies safely within these cells, eventually bursting them to infect more macrophages, thereby hijacking the host's own defence system to spread throughout the body.
7. Can a person who has recovered from cutaneous leishmaniasis get infected again?
Yes, it is possible. While recovery from cutaneous leishmaniasis often provides some immunity, this protection is not always complete or lifelong. The level of immunity can depend on the specific Leishmania species that caused the initial infection. Therefore, even after healing, individuals in endemic areas should continue to take precautions to prevent new sandfly bites, as re-infection can occur, potentially with a different or more virulent strain of the parasite.
