Hemoflagellates: Developmental Stages, Types, Clinical Features

The Hemoflagellates/flagellates are the parasites that infect the blood and tissues of humans and animals. These live in the blood and tissues of man and other hosts and the gut of the insect vectors. These have a flagellum which is a thin hair-like structure. There are different developmental stages of the parasite.

Developmental Stages of Hemoflagellates

• Amastigote - The Amastigote is a stage in which the flagella is absent but it is present in all the other 3 developmental stages.
• Promastigote - It is a stage that is elongated and the kinetoplast is present anterior to the nucleus. The flagella arises near it and emerges from the anterior end of the body.
• Epimastigote - It is an elongated form with a juxta nuclear kinetoplast. The flagella arises near it and emerges from the side of the body to run along the membrane.
• Trypomastigote- It is a true trypanosome type. It has a post-nuclear kinetoplast and flagella arise near it to run along a long undulating membrane.

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Types of Flagellates

1. Trypanosoma cruzi
   • Human is a definitive host.
   • Reduviid bug or kissing bug is an intermediate host.
   • Many animals like armadillos, cats, dogs, and pigs are reservoirs.
   • All developmental stages will be seen.
   • Trypomastigote is an infective stage and it is present in the Reduviid bug. The bug bites the human and it will get converted into an amastigote form in humans. Later the amastigote form develops into trypomastigote which enters blood and subsequently the bug comes and bites again taking away the trypomastigote.
   • In insects, epimastigote and trypomastigote forms are found.

Clinical Features of Hemoflagellates

• Acute Chagas Disease- The features are:
  • Chagoma (It is an entry site edema)
  • Lymphadenopathy
  • Periorbital edema is also called a Romana sign.
  • Hepatosplenomegaly
• Chronic Chagas disease- The features are:
  • This disease affects the heart and causes myocarditis and dilated cardiomyopathy.
  • On the esophagus, it causes a Megaesophagus. It is also called Achalasia cardia.
  • It can lead to a Megaesophagus.
  • Meningoencephalitis is also it’s another manifestation.

Diagnosis of Hemoflagellates

• A blood sample is taken for the diagnosis.
• Trypomastigotes are seen with the nucleus at the center and post-nuclear kinetoplast.
• Novy Nicolle McNeal used as a culture medium.

Treatment

• The drug of choice is Benznidazole.
• Symptomatic treatment is given.

1. Trypanosoma brucei
   • This parasite causes a famous disease known as sleeping sickness.
   • It has two types of parasites. These are:
   • T.B Gambiense:
     • It is also called West African sleeping sickness.
     • The vector is the Tse Tse fly.
     • The primary reservoir is humans.
     • The clinical features mainly include posterior cervical lymphadenopathy. It is also called as Winterbottom sign.
     • The parasitemia and virulence are less in this case.
     • The treatment is Pentamidine.
   • T.B Rhodesiense
     • It is also called East African sleeping sickness.
     • The vector is the Tse Tse fly.
     • The main reservoir is animals.
     • The parasitemia and virulence are more in this case.
     • The treatment is Suramine.

Diagnosis

• Blood or CSF samples are taken for diagnosis.
• Weinmann’s medium is used to culture.

2. Leishmania Donovani

• Leishmania is caused by unicellular eukaryotic protozoan which produces different clinical syndromes ranging from cutaneous ulcers to fatal visceral diseases. 
• The organisms are transmitted by sandflies (phlebotomus) which acts as a vector. 
•  Transmission may be anthroponotic ( from infected humans to healthy humans) and it can be zoonotic ( from animal reservoir to humans). 

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Leishmania Types And Symptoms

There are multiple types of leishmania depending upon the type of symptoms it produces.

1. Visceral Leishmaniasis-
   • It is also called as Kala Azar or Black fever. The disease is named after the symptoms that is pigmentation of the skin ( Dark, blackened and scaly skin). 
   • Patient will present with fever, chills and rigors during the intial stages of the disease. There will be protuberant abdomen due to hepatosplenomegaly.

1. Cutaneous Leishmaniasis
   • It is caused by L. Tropica. After getting bitten by the sandfly , an oriental sore develops also called as Baghdad Boil.
   •  It has erythematous border with lot of yellow colour exudative discharge present in the center. 
   • The lesions produced on the exposed body parts( Face and hands) can lead to permanent scar formation.
   • It has a variant called as Diffuse Cutaneous Leishmaniasis which spreads from the face to rest of the body.
2. Mucocutaneous Leishmaniasis
   • It is caused by L.Brasiliensis and it is associated with lesions on the buccal mucosa and skin. 
   • The parasite enters via the lymphatics and reached the blood stream and can cause intense inflammation and destruction. 
   • The lesions are mainly in the mouth or around the mouth or nose. 
   • Other parts like soft palate, cheeks and lips can also get involved and there is risk of development of secondary bacterial infection..
3. Leishmaniasis Recidivans
   • It is also called as Relapsing Leishmaniasis and it occurs due to inadequate treatment. There will be nodular lesions or rashes seen around a central healing.

Diagnosis

• The clinical history and physical examination plays an important role in the diagnosis. Spleen will be heavily enlarged.
• Amastigotes also known as LD bodies are diagnostic. These donot have any flagella. Amastigotes can be appreciated in the splenic smears (most sensitive) of the patients but bone marrow is preferred for sample.               

Amastigote and Promastigote of Leishmania

• Blood smear/Bone marrow analyis can detect the LD bodies being engulfed by Macrophages.
• On CBC there will be pancytopenia as the parasite destroys the reticuloendothelial system.
• The medium used is Novy-McNeal-Nicolle medium and PCR technique can also be used for qualitative detection of leishmanial nucleic acid.

Leishmania Treatment

• Severe anemia can be treated with the blood transfusion and manage the comorbid conditions carefully.
• Drug of choice for Visceral Leishmaniasis is Liposomal Amphotericin B. But there is a disease called as Post Kala Azar Dermal Leishmaniasis (PKDL) which happens in Kala azar patients getting treatment with Liposomal Amphotericin B. They develops hypopigmented nodules after 1-2 years. Treatment for PKDL is Oral Miltefosine.
• Multidrug therapy for leishmaniasis is likely to be preferred in the future.
• The treatment for Mucocutaneous and Cutaneous Lesihmaniasis is Sodium Stibogluconate and regular follow-up is required after the treatment.

Also Read: Myxoviruses: Structure, Function, and Impact on Health

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