Taxonomic Classification of Parasites PDF

Taxonomic Classification of Parasites Module 01: Principles and Perspectives Julius R. Migrino, MD | Asynchronous ▪ Further subdivided into Tapeworms (Cestoda) and Flukes (Trematoda) ⎻ Arthropods (Arthropoda) ▪ Houses the Insects (Insecta) and Arachnids (Arachnida) ○ Kingdom Protozoa ▸ Houses the re...

Taxonomic Classification of Parasites Module 01: Principles and Perspectives Julius R. Migrino, MD | Asynchronous ▪ Further subdivided into Tapeworms (Cestoda) and Flukes (Trematoda) ⎻ Arthropods (Arthropoda) ▪ Houses the Insects (Insecta) and Arachnids (Arachnida) ○ Kingdom Protozoa ▸ Houses the relatively simpler, unicellular parasites with prominent phyla: ⎻ Sarcomastigophora ▪ Amoebas (Sarcodina) ▪ Flagellates (Mastigophora) ⎻ Apicomplexa ▪ Roundish protozoa (Coccidia) ▪ Blood dwelling protozoans (Hemosporidia and Piroplasmida) ⎻ Ciliates (Ciliophora) TABLE OF CONTENTS LEARNING OBJECTIVES........................................................................ 1 I. MEDICAL PARASITE TAXONOMIC TREE..............................................1 A. MEDICALLY IMPORTANT PARASITES.............................................1 II. PHYLUM NEMATODA.......................................................................1 A. GENERAL CHARACTERISTICS........................................................ 1 B. MEMBERS OF PHYLUM NEMATODA............................................ 1 III. PHYLUM PLATYHELMINTHES...........................................................2 A. CLASS CESTODA........................................................................... 2 IV. PHYLUM ARTHROPODA.................................................................. 2 A. GENERAL CHARACTERISTICS........................................................ 3 B. MEMBERS OF PHYLUM ARTHROPODA........................................ 3 V. PHYLUM SARCOMASTIGOPHORA/COCCIDIA....................................3 A. SARCOMASTIGOPHORA............................................................... 3 B. CILIOPHORA................................................................................. 3 VI. PHYLUM APICOMPLEXA................................................................. 3 A. GENERAL CHARACTERISTICS........................................................ 3 B. COCCIDIA..................................................................................... 3 C. HEMOSPORIDIA........................................................................... 3 V. KEY POINTS..................................................................................... 4 QUICK REVIEW.................................................................................... 4 RATIONALE..................................................................................4 REFERENCES........................................................................................ 4 REQUIRED................................................................................... 4 FREEDOM SPACE................................................................................. 5 LEARNING OBJECTIVES 1. Create the taxonomic tree for common parasites 2. Describe the common features of each taxonomic classification 3. Classify common parasites according to their taxonomic classifications I. MEDICAL PARASITE TAXONOMIC TREE Figure 1. Medical Parasite Taxonomic Tree A. MEDICALLY IMPORTANT PARASITES ● Primarily eukaryotic organisms ○ Those with a membrane-bound nucleus ● Further divided into 2 big kingdoms ○ Kingdom Animalia ▸ Houses the more cellularly-complex worms and “insects” ⎻ Roundworms (Nematoda) ⎻ Flatworms (Platyhelminthes) YL6:01.06 Take Note! ● Some references use the term Nemahelminths/Nemahelminthes for Nematoda ● Coccidia is a subclass, not a class II. PHYLUM NEMATODA A. GENERAL CHARACTERISTICS ● Houses parasites more commonly referred to as roundworms ● General Morphology: looks like a prototypical worm ○ Cylindrical ○ Elongated ○ Noodle-like or thread-like ○ Bilateral symmetry ○ Size range: from microscopic to the length of a typical pencil ● Digestive Tract ○ Complete: with mouth, intestine, and anus ○ With muscular pharynx ● Sex Characteristics ○ Dioecious: male and females are distinct ▸ Males: testes ▸ Females: ovaries and uterus ● Other Features ○ May have amphids, phasmids ▸ Sensory organs ▸ Depend on where they are located in the worm ○ Most nematodes inhabit the GI tract as adults ▸ Some reside in the blood and other tissues where they can steal nutrients from their host using their well-developed digestive tract B. MEMBERS OF PHYLUM NEMATODA ● ● ● ● Ascaris - prototype roundworm Trichuris Hookworms Strongyloides TG06: Abangan, David, Del Corro, Layug, Mendoza J., Mendoza R., Ng, Santiago, Santos, Tseng, Uy, Villavicencio CG15: Bennett, Bunag, Cabrera, Chan, Kim, Lim, Parfan, Pesalbon, Rosario, Siongco, Usa, Zuniga 1 ● ● ● ● ● ● ● Angiostrongylus Capillaria Enterobius Trichinella Filarial Worms - vector-borne Anisakis Members also contain soil-transmitted helminths and food-borne roundworms Figure 3. Phylum Platyhelminthes (Left: Cestoda. Right: Trematoda) A. CLASS CESTODA ● Cestodes are further divided into 2 distinct orders: ○ Pseudophyllidean ○ Cyclophyllidean Table 2. Pseudophyllideans vs Cyclophyllideans Figure 2. Nematoda Pseudophyllidean III. PHYLUM PLATYHELMINTHES Table 1. Summary of Class Cestoda and Class Trematoda Cestoda General Morphology ● ● ● ● Digestive Tract Sex Characteristics ● ● Tapeworms ○ Beef, pork, and fish tapeworms Dorsoventrally flat, bilateral symmetry Segmented into smaller subunits → proglottids Typically longer than flukes ● ● ● Other Features ● ● ● Members ● ● ● ● ● Leaf-like flukes Dorsoventrally flat, bilateral symmetry Unsegmented (leaf-like) Tegument (no internal digestive tract) ○ Metabolically active body covering ○ Acts as both sensory apparatus and nutrient absorbing organ Hermaphroditic/ monoecious Cyclophyllidean ● ● Flat, elongated Spatulate (w/ 2 grooves) ● Globular (w/ 4 prominent suckers) Ovum ● Operculated ● Non-operculated Sex Characteristics ● Scolex prominent anterior portio ● No scolex or proglottids Uterine Pore ● Present ● Absent Uterus ● ● Non-branching Found inside proglottids ● Visible, highly branching Found in proglottids Trematoda ● ● Hermaphroditic/ Monoecious Exception: Schistosoma Scolex - prominent anterior portion Neck Strobila (proglottids) ● No scolex or proglottids Taenia Diphyllobothrium Hymenolepis Echinococcus Diphylidium ● Schistosoma (blood fluke) Fasciolopsis Fasciola Clonorchis Opisthorchis Paragonimus Echinostoma ● ● ● ● ● ● Cyclophyllidean ● Genital Pore ● Ventral ● Lateral Host (01.05, 2024) ● Requires 2 intermediate hosts ● Requires 1 intermediate host Others ● Only Diphyllobothrium belongs in this order ● Contain most medically important tapeworms Figure 4. Cestodes (Left: Pseudophyllideans. Right: Cyclophyllideans) IV. PHYLUM ARTHROPODA ● There are many genera of arthropods that can be considered human parasites ● Most common parasitic arthropods include: ○ Cockroaches YL6:01.06 Taxonomic Classification of Parasites 2 ○ Caterpillars ○ Hornets ○ Wasps ○ Others ● Most parasitic arthropods are ectoparasites ○ Others are also vectors to other parasites ● More common parasitic arthropods belong to the two classes: insects and arachnids A. GENERAL CHARACTERISTICS ● Bilateral symmetry ● Segmented body, jointed appendages ● Chitinous exoskeleton 2. What class is commonly referred to as Amoeba? Answers: 1F, 2 Sarcodina VI. PHYLUM APICOMPLEXA A. GENERAL CHARACTERISTICS ● Obligate intracellular parasites ● Possess apical complex ○ Collection of organelles and secretory structures ○ Helps the parasite infect the host cell B. MEMBERS OF PHYLUM ARTHROPODA ● ● ● ● ● ● ● Mosquitoes Lice Fleas Mites Ticks Flies Others Figure 6. Apical complex (Green cone encircled in red) B. COCCIDIA V. PHYLUM SARCOMASTIGOPHORA/COCCIDIA ● All of these protozoans are ameboid in nature ○ Especially in trophozoite stage A. SARCOMASTIGOPHORA ● Sarcodina (Amoebas) ○ General morphology: asymmetric, amoeboid ○ Locomotory apparatus: pseudopodium ▸ Hyaline foot-like extrusions of ectoplasm ● Mastigophora (Flagellates) ○ General morphology: asymmetric, amoeboid ○ Locomotory apparatus: flagella ▸ One or more flagellum ● General Morphology: maintains a circular shape especially during cystic and oocyst stages ● Habitat: Gastrointestinal tract of definitive host ● Special features ○ Apical complex ▸ WITH conoid (feeding tube) ⎻ Used like a straw to feed on components of other cells ● Members: ○ Toxoplasma– has a more complex life cycle; non-parasitic ○ Cryptosporidium ○ Cystoisospora ○ Cyclospora B. CILIOPHORA ● Ciliophora (Ciliates) ○ General morphology: asymmetric, amoeboid ○ Locomotory apparatus: cilia ▸ Very small, fine, and hairy Figure 7. Coccidia C. HEMOSPORIDIA Figure 5. Sarcodina (left), Mastigophora (middle), Ciliophora (right). In asterisks are organisms not generally considered to be parasitic, but still studied in medical parasitology as indicator organisms Active Recall Box 1. T/F. Roundworms are subdivided into Tapeworms and Flukes. YL6:01.06 Taxonomic Classification of Parasites ● Do not form oocysts ● Habitat: intraerythrocytic (live inside blood cells) ● Special features ○ Apical complex ▸ WITHOUT conoid (feeding tube) ⎻ Will need to invade to gather nutrients ● Members: ○ Plasmodium– best prototype of this group ○ Babesia– technically under Piroplasmida 3 Figure 8. Hemosporidia VII. KEY POINTS ● Medical parasites are single or multicellular eukaryotes composed of animals and protozoans ● Animalia: ○ Nematodes are roundworms with a complete digestive system ○ Platyhelminthes are flatworms that are either: ▸ Segmented Cestodes (tapeworms) or ⎻ Pseudophyllideans with spatula-like scolex with unbranched uterus ⎻ Cyclophyllideans with round scolex and highly branching uterus ▸ Unsegmented Trematodes (flukes) ▸ Parasitic anthropods can be insects, arachnids or a bunch of other bugs ● Protozoa ○ Parasitic protozoans can be classified according to their mode of locomotion ▸ Sarcodineans - pseuodopodium ▸ Mastigophorans - flagella ▸ Ciliophora - cilia ○ Protozoans can also be classified according to infection machinery ● Most parasites in humans inhabit the GI tract, some in blood and blood cells (eg. Hemosporidia and Piroplasmida), and some outside the human host (eg. insecta) ● Some can get nutrients either by simple absorption (via the digestive system) or through complex metabolism of intracellular molecules using different organelles ● Knowing the general features by taxonomic classification can help medical personnel understand why and how certain parasites behave the way they do, and develop appropriate strategies that are most effective against them 4. The following families are under Kingdom Animalia except: A. Platyhelminthes B. Apicomplexa C. Nematoda D. Arthropoda 5. T/F. Class Coccidia has a general circular morphology, lives in the GI tract of the definitive host, and has an apical complex WITH conoid or feeding tube. ANSWER KEY 1T, 2D, 3F, 4B, 5T RATIONALE 1. True. A conoid is the feeding tube that may (Coccidia) or may not (Hemosporida) be part of the apical complex of protozoans. 2. D. Both statements are false. 3. False. Most parasites in humans inhabit the GI tract. 4. B. Apicomplexa. Apicomplexa is found under Kingdom Protozoa 5. True. The statement is true. REFERENCES REQUIRED 💻 Migrino, J.R. (2021, August 5). Taxonomic Classification of Parasites [Video]. Youtube. [https://youtu.be/g3cjFyU0Qnc] ● 📄Migrino, J.R. (2021, August 8). Medical Parasitology Taxonomic Classification. [Lecture slides]. ● Concerns and Feedback form: http://bit.ly/YL6CFF2027 How’s My Transing? form: https://bit.ly/2027YL6HMT Mid-Semester Evaluation form: https://bit.ly/2027YL6MidSem End-of-Semester Evaluation form: https://bit.ly/2027YL6EndofSem YL6 TransMap: https://bit.ly/2027YL6TransMap QUICK REVIEW QUESTIONS 1. T/F. Protozoans can be classified using the presence or absence of a conoid. 2. Coccidia are commonly found in the GI tract. Hemosporida feed on nutrients in the blood. A. The first statement is true. The second statement is false. B. The first statement is false. The second statement is true. C. Both statements are true. D. Both statements are false. 3. T/F. Most parasites in humans inhabit the respiratory tract. YL6:01.06 Taxonomic Classification of Parasites 4 FREEDOM SPACE EADIN 1 YL6:01.06 Taxonomic Classification of Parasites 5