Protozoans - Hemo flagellates

• Key Genera
  • Trypanosoma species
  • Leishmania spp.

Morphologic Forms of Trypanosoma

• Amastigote (Leishmanial form)
• Promastigote (Leptomonad)
• Epimastigote (Crithidia)
• Trypomastigote (Trypanosomal)

Trypanosoma spp.

Trypanosoma cruzi

• Common Name: American trypanosomes
• Disease: Causes Chaga's disease

Trypanosoma brucei complex

• Common Name: African trypanosomes
• Disease: Causes Sleeping sickness
  • T. brucei rhodesiense: East African Sleeping sickness
  • T. brucei gambiense: West African Sleeping sickness

Diagnostic Procedure

• Blood smear used to identify infection

Vectors

• American Trypanosomes
  • Vectored by the Reduviid bug (Triatomine), also known as Kissing bug
• African Trypanosomes
  • Vectored by Tsetse fly (Glossina)

Lifecycle

• Metacyclic trypanosomes passed out with the feces of the bug invade muscle in American Trypanosomes.
• Metacyclic trypomastigote passed out through salivary glands invading CNS in African Trypanosomes.

Pathology

Trypanosoma cruzi (Chaga's disease)

• Romana Sign: Unilateral swelling of the eye
• Cardiomegaly
• Megadisease: Enlargement of organs
• Chagoma: Nodule at bite site

Trypanosoma brucei complex

• Winterbottom Sign: Enlargement of lymph nodes
• Chancre: At the bite site
• Nagana disease: Affects animals
• Kerandell sign

Lab Diagnosis

• For T. cruzi
  • Amastigote found in tissue scraping
  • Xenodiagnosis: Trypanosome detection via vectors
  • Finding Leishman-Donovan bodies in heart at autopsy
  • Trypomastigote found in blood: C-shaped, thick organism with prominent kinetoplast.

Treatment

• African Sleeping Sickness: Pentamidine, Suramin, Melarsoprol (for late-stage with CNS involvement)
• Chagas Disease: Nifurtimox, Bezuidazole, Eflornithine (resurrection drug)

Leishmania spp.

Transmission

• All species transmitted by the sandfly (Phlebotomus spp.)

Morphological Forms

• Amastigote form: Observed in humans
• Promastigote form: Found in the gut of the sandfly

Diseases

• L. tropica: Oriental sore or Old World cutaneous leishmaniasis
• L. mexicana: Chiclero's ulcer or New World cutaneous leishmaniasis
• L. braziliensis: Espundia or mucocutaneous leishmaniasis
• L. donovani: Kala-azar or visceral leishmaniasis (black fever)

Diagnosis

• Blood smear, needle aspiration, punch/wedge biopsy
• Culture: Novy-McNeal-Nicolle (NNN)
• Intrademal test: Dr. Montenegro Skin Test.

Apicomplexan

• Characteristics
  • No locomotor organelles
  • Structural features include micronemes, subpellicular tubules, polar ribs, conoids, rhoptries.
• Complex life cycle stages: Sporogony, gamogony, schizogony.

Coccidians

• Includes Plasmodium spp., Babesia spp., Toxoplasma gondii.

Plasmodium spp.

• Infections: Most common cause of malaria.

Lifecycle Details

• Spends part of its life cycle in mosquitoes, infects and ruptures blood cells.
• Main stages include schizogony (asexual reproduction), gamogony (gamete formation), and sporogony (sexual reproduction).

Malaria Overview

• Common Terms: Defined as "bad air."

Host Information

• Definitive Host: Anopheles mosquitoes
• Intermediate Host: Humans

Vectors in the Philippines

• Anopheles minimus var. flavirostris is principal malaria vector.

Plasmodium species and their characteristics

• P. falciparum: Most frequent; causing malignant tertian malaria, 48h cycle.
• P. vivax: Benign tertian malaria, 48h cycle.
• P. malariae: Quartan malaria, 72h cycle.
• P. ovale: Exclusive rare, benign tertian malaria, 48h cycle.
• P. knowlesi: Simian malaria parasite; isolated from humans since 1965.

Symptoms of Malaria

• Cold Stage: Feeling of intense cold, vigorous shivering, lasts 15-60 minutes.
• Hot Stage: Intense heat, dry skin, lasts 2-6 hours.
• Sweating Stage: Profuse sweating, exhausted, lasts 2-4 hours.

Plasmodium falciparum

• Associated with "Black water fever" due to hemoglobin excreted in urine.

Diagnostic Features

1. Trophozoite stage
2. Schizont stage
3. Gametocyte stage

Features of Plasmodium spp.

• Characteristics such as vacuoles, nuclei/chromatin dots, and cytoplasm are key identification markers.

Plasmodium knowlesi

• Found primarily in long-tailed monkeys, also infects humans as the fifth malaria parasite.
• Diagnostically similar to P. malariae but with a rapid 24-hour erythrocytic cycle.
• Confirmed through PCR analysis; often misreported as P. malariae.

Parasite Counting in Diagnostics

• Key for determining parasitological severity and monitoring treatment responses.

Methods of Counting

• Thick Film: Recommended cross-sectional method; count parasites after observing 200 WBCs; results = Number of parasites x 8000/200 WBCs.
• Example Counting: 115 rings/trophozoites x 8000/200 WBCS = 4,600/µL blood.

Laboratory Diagnosis of Malaria

• Thick smear: Gold standard for detecting parasites.
• Thin smear: Used for species identification post thick-film detection.

Babesia spp.

Babesia microti

• Infects RBC; closely related to Plasmodium falciparum causing non-Tufted fever/Babesiosis.
• Transmitted mainly by ticks (Isodes scapularis).

Diagnostic Features

• Recognized by "Tetrad formation" and "Maltese cross".

Other Babesia spp.

• Babesia canis: Infectious jaundice in dogs.
• Babesia bigemina: Red water syndrome in carabaos.

Toxoplasma gondii

• Host Information: Cats are definitive hosts, others like cattle, pigs, etc., act as intermediate hosts.

Infective Stage

• Mature oocysts containing two sporocysts, each with four sporozoites.

Transmission Routes

• Includes ingestion, blood transfusion, bone marrow transplantation, and transplacental.

Lifecycle in Humans

• Humans serve as intermediate hosts; tachyzoites are rapidly formed in tissues and can cause serious health issues during pregnancy.

Other Coccidians

• Isospora belli and Cryptosporidium parvum: Notable causes of diarrhea.
  • Identification methods include sugar concentration and other specialized techniques.
  • Cyclospora cayetanensis: Characterized by round, fluorescent structures.