Leishmania Life Cycle

Introduction

Leishmania are protozoan parasites that fall under the class Kinetoplastea and the genus Leishmania. This parasite causes a vector-borne disease known as Leishmaniasis and it is transmitted through bites of infected sandflies. The disease Leishmaniasis has three primary forms namely visceral (most fatal form), cutaneous (most common form) and mucocutaneous. The parasite Leishmania is known to live and multiply inside a female sandfly.

The visceral leishmania, also known as the kala-azar, is the most fatal and causes anaemia, weight loss, irregular periods of fever and enlargement of spleen and liver.

The cutaneous leishmania is the most common one and causes ulcers, skin damage that leads to long term scars.

The mucocutaneous leishmania causes complete or incomplete destruction of mucous membranes in the nose, throat and mouth. Thus, we see how different forms of leishmania parasites affect the host in different ways.

These protozoan parasites are mostly active during the night, in humid and warm temperatures.

Now, let’s look at the life cycle of Leishmania parasites in a sand fly host, to get a better understanding.

Life Cycle of Leishmania

1) The Sandfly Stage –

The infected phlebotomine female sand fly finds a suitable host and inject the promastigote parasites into the skin during a blood meal. The promastigotes are elongated, flagellated and infective parasites that grow in the midgut of the female sandfly.

2) The Human Stage –

When these promastigotes parasites reach the wound, they are phagocytized or ingested by macrophage cells. In macrophage cells, these promastigotes transform to amastigotes, which is the tissue stage of the parasite. Amastigotes parasites multiply by the process of simple division.

After multiplying and forming a larger group, they infect other phagocytic cells.

Later, when a sandfly ingests these infected cells during a blood meal from an infected person it gets infected with the parasite. Inside the sandflies, the amastigotes turn into promastigotes and develop inside the fly’s gut. After developing, the parasite migrates to the sucking organ of the fly known as a proboscis. After arriving at the proboscis, it is only a matter of time when the sandfly bites a human host and passes on the disease leishmaniasis.

Conclusion

According to the World Health Organization, approximately 90 species of sandfly are known to transmit the protozoan parasite Leishmania. With human beings, there are about 70 species of animals who have unfortunately fallen host to the parasite.

Frequently Asked Questions on Leishmania Life Cycle

How do people get infected with Leishmania parasites?

The primary way that people get infected with Leishmania parasites is through the bite of an infected female sandfly. These sandflies are one fourth the size of mosquitoes, they are silent and don’t make noise when they fly. Even the bites of the infected sandfly are painless and almost invisible. Therefore, chances are the host might not even notice the bite marks.

How can leishmaniasis be prevented?

Spraying insecticides in all areas of the household, especially bedrooms, wearing clothes that cover the majority of the skin, and using insect repellent creams on the exposed skin.

What are the symptoms of leishmaniasis in dogs?

The leishmaniasis in dogs is the visceral leishmaniasis, which shows symptoms like diarrhoea, nose bleed, blood in stool, vomiting, loss of appetite and swollen lymph nodes.

Can leishmaniasis be transmitted from dogs to human beings?

No, the disease leishmaniasis cannot be transmitted from dogs to human beings.

What is the treatment for the disease leishmaniasis?

For people who have this disease, doctors might suggest antiparasitic drugs like amphotericin. But, the treatment for leishmaniasis differs, depending on the type of leishmaniasis infecting the person.

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