Introduction to Medical Parasitology.pptx

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1. Medical Parasitology

2. Parasitology branch of biology concerned with dependence of one living on another Study of parasites, their host and the relationship between them.

3. Fields of Parasitology Medical Parasitology Veterinary Parasitology Parasite Ecology Taxonomy and Phylogenetic

4. Key Definitions Medical parasitology: “the study and medical implications of parasites that infect humans” A parasite: “a living organism that acquires some of its basic nutritional requirements through its intimate contact with another living organism”. An organism that has sustained contact with another organism to the detriment of the host organism.

5. Types of Parasites Parasites may be simple unicellular protozoa, or complex multicellular metazoan Parasites can be classified into three main groups: protozoa, helminths, and ectoparasites .

6. Protozoa Protozoa are single-celled eukaryotic organisms. Examples include: Plasmodium (causes malaria) Giardia (causes giardiasis) Entamoeba (causes amoebiasis ) Trypanosoma (causes African sleeping sickness)

7. Helminths (Worms) Helminths are multicellular eukaryotic organisms. Examples include: Roundworms (nematodes) Tapeworms ( cestodes ) Flukes (trematodes) These parasites can cause a variety of diseases, such as ascariasis, taeniasis , and schistosomiasis.

8. Ectoparasites Ectoparasites are parasites that live on the outside of the host. Examples include: Lice ( Pediculus ) Ticks ( Ixodes ) Mites ( Sarcoptes ) Fleas ( Ctenocephalides ) Ectoparasites can transmit diseases and cause skin irritations.

9. Key Definitions An ectoparasite : “a parasite that lives on the external surface of another living organism” – e.g. lice, ticks Host : “the organism in, or on, which the parasite lives and causes harm” Definitive host: “the organism in which the adult or sexually mature stage of the parasite lives” Intermediate host: “the organism in which the parasite lives during a period of its development only” Zoonosis: “a parasitic disease in which an animal is normally the host - but which also infects man” Vector: “a living carrier (e.g.an arthropod) that transports a pathogenic organism from an infected to a non-infected host”. A typical example is the female Anopheles mosquito that transmits malaria

10. Host Host: Organism from which a parasite obtains its nutrition and/or shelter

11. Types of Host Definitive Host : The host in which the parasite goes through its sexual cycle (I.e., fertilization & meiosis) E.g., mosquitoes serve as definitive hosts of the malaria parasite ( Plasmodium spp.)

12. Intermediate Host : Host in which the parasite replicates but does not go through its sexual cycle and may multiply asexually E.g., mammals, including humans, serve as intermediate hosts of the malaria parasite ( Plasmodium spp.)

13. Reservoir host: Organism in which a parasite that is pathogenic for some other species, lives and multiplies usually without damaging its host e.g rats are known carriers of Trypanosoma cruzi , which causes Chagas disease.

14. Vectors Living organism that carries disease causing organism to a new host. Host that transmit parasite to man; Anopheles mosquito is a vector for the parasitic disease malaria (Plasmodium parasite)

15. Types of Vector Biological Vector Biological Vectors:  These are living organisms that transmit parasites from one host to another. Examples include : Mosquitoes :  Transmit diseases like malaria, dengue fever, and yellow fever.  Ticks :  Transmit diseases like Lyme disease, Rocky Mountain spotted fever, and babesiosis .  Fleas :  Transmit diseases like plague and typhus.  Tsetse flies:  Transmit diseases like African sleeping sickness.

16. Mechanical Vectors:   These are non-living objects that can passively carry parasites from one host to another. Examples include: Houseflies:  Can carry pathogens on their bodies and legs, potentially contaminating food and surfaces.  Cockroaches :  Can carry parasites like tapeworms and roundworms in their digestive tracts.  Dust mites:  Can trigger allergic reactions and asthma, potentially worsening symptoms in individuals with parasitic infections. 

17. Examples of Parasitic Vector-Borne Diseases: Malaria :  Transmitted by mosquitoes, causing high fever, chills, and flu-like symptoms.  Dengue fever:  Transmitted by mosquitoes, causing high fever, headache, muscle and joint pain, and a characteristic rash.  Lyme disease:  Transmitted by ticks, causing fever, headache, fatigue, and a characteristic bull's-eye rash.  African sleeping sickness:  Transmitted by tsetse flies, causing fever, headaches, and neurological problems.  Leishmaniasis :  Transmitted by sandflies, causing skin sores, fever, and weight loss. 

18. Introduction to Parasite Taxonomy Taxonomy is the science of classifying organisms based on their evolutionary relationships and shared characteristics. Parasites are classified using a hierarchical system that groups them into different taxonomic levels.

19. Taxonomic classification helps in: Identifying and differentiating between different parasites Understanding the evolutionary relationships and genetic diversity of parasites Developing targeted diagnostic tests and treatment strategies Studying the epidemiology and ecology of parasitic diseases

20. - Taxonomic Levels Domain Kingdom Phylum Class Order Family Genus Species

21. Domains of Parasites Parasites belong to two main domains: Archaea Eukarya

22. Kingdoms of Parasites   Parasites are found in the following kingdoms: Protista (protozoa) Animalia (helminths, ectoparasites )

23. Phyla of Parasitic Protozoa Protozoan parasites belong to the following phyla: Apicomplexa (e.g., Plasmodium, Toxoplasma) Amoebozoa (e.g., Entamoeba , Acanthamoeba ) Excavata (e.g., Giardia, Trypanosoma )

24. Phyla of Parasitic Helminths Helminth parasites belong to the following phyla: Platyhelminthes (flatworms: tapeworms, flukes) Nematoda (roundworms) Acanthocephala (thorny-headed worms)

25. Parasitic arthropods belong to the phylum Arthropoda , which includes: Arachnida (ticks, mites) Insecta (lice, fleas)

26. Classification of Protozoan Sub kingdom Phylum Sub-phylum Class Species- examples Protozoa Sarcomastig-ophora further divided into Sarcodina -- - move by pseudopodia Rhizopods E. histolytica Mastigophora move by flagella Flagellates G. lamblia Apicomplexa no organelle of locomotion Sporozoa P. falciparum, P. vivax, P. malariae, P. ovale Ciliophora move by cillia Ciliates B. coli

27. C lassification of H elminths Sub kingdom Phylum Class Genus – examples Metazoa Nematodes Round worms; appear round in cross section, they have body cavities, a straight alimentary canal and an anus Ascaris (roundworm) Trichuris (whipworm) Ancylostoma (hookworm) Necator (hookworm) Enterobius (pinworm or threadworm) Strongyloides Platyhelminthes Flat worms; dorsoventrally flattened, no body cavity and, if present, the alimentary canal is blind ending Cestodes Adult tapeworms are found in the intestine of their host They have a head ( scolex ) with sucking organs, a segmented body but no alimentary canal Each body segment is hermaphrodite Taenia (tapeworm) Trematodes Non-segmented, usually leaf-shaped, with two suckers but no distinct head They have an alimentary canal and are usually hermaphrodite and leaf shaped Schistosomes are the exception. They are thread-like, and have separate sexes Fasciolopsis (liver fluke) Schistosoma (not leaf shaped!)

28. Parasitic Life cycle A parasitic life cycle refers to the series of developmental stages and host organisms that a parasite goes through to complete its reproduction and propagation.

29. Types of parasitic life cycle Direct Life Cycle In a direct life cycle, the parasite requires only one host to complete its development. The parasite typically infects the host through ingestion or penetration, reproduces within the host, and then releases its offspring into the environment, where they can infect another host. Tapeworms ( Taenia spp.) - Tapeworms infect humans by ingesting undercooked meat containing tapeworm larvae. Roundworms ( Ascaris lumbricoides ) - Humans ingest Ascaris eggs from contaminated food, water, or soil, and the larvae mature within the human host.

30. Indirect Life Cycle In an indirect life cycle, the parasite requires multiple hosts to complete its development. The parasite typically infects an intermediate host, where it reproduces asexually, and then infects a definitive host, where it reproduces sexually. Malaria (Plasmodium spp.) - Require mosquitoes as an intermediate host to transmit the parasite to humans, the definitive host.

31. Complex Life Cycle Some parasites have even more complex life cycles, involving multiple intermediate hosts and/or different modes of transmission. Schistosomiasis ( Schistosoma spp.) - Require freshwater snails as an intermediate host, then infect humans through skin penetration of the larval stage. Toxoplasmosis (Toxoplasma gondii ) - Can infect humans through ingestion of undercooked meat containing cysts or by ingesting food/water contaminated with oocysts from the feces of infected cats.

32. Transmission Mouth/Food: This is the most common mode of transmission for parasites. It occurs when people ingest contaminated food or water that contains infective stages of the parasite. Examples include tapeworms, roundworms, and protozoa like Giardia and Cryptosporidium.

33. Skin Penetration: Some parasites can enter the body directly through the skin. This can happen when people come into contact with contaminated soil or water, or when they are bitten by infected insects. Examples include hookworms, schistosomes , and the larvae of certain roundworms.

34. Direct Contact: This mode of transmission involves direct contact with an infected person or animal. This can happen through sexual contact, close physical contact, or contact with contaminated feces or urine. Examples include pinworms, scabies, and some protozoa like Entamoeba histolytica .

35. 💉 Vector-borne: Certain parasites are transmitted by vectors, such as mosquitoes, ticks, or fleas. These vectors pick up the parasite from an infected animal or human and then transmit it to another host when they bite. Examples include malaria, Lyme disease, and Chagas disease.

36. pathogenesis of parasitic infections Pathogenicity refers to the ability of an organism to cause disease ( ie , harm the host ). The mechanisms of parasitic infection vary widely depending on the parasite species, its quantity, and the host's immune response. Parasite size is not always a reliable predictor of disease severity.

37. Direct Damage:  Some parasites cause direct damage to tissues and organs as they migrate or feed. This can lead to inflammation, tissue destruction, and organ dysfunction. 

38. Toxic Substances:  Certain parasites release toxins that can harm the host. These toxins can cause a variety of symptoms, including fever, fatigue, nausea, and vomiting. 

39. Tutorial Size, shape and arrangement of Bacterial cells and bacterial colonies; Applications on diagnostic microbiology bench Bacterial Staining - Gram Positive cell wall – Structure and Applications; immunological and Therapeutic Implications Gram negative cell wall- Structure and Applications; immunological and Therapeutic Implications Bacterial Capsules - Structure and Applications; immunological and Therapeutic Implications

40. Immune Response:   The human immune system plays a complex role in the pathogenesis of parasitic infections. While it can help to control and eliminate parasites, the immune response can also contribute to tissue damage and inflammation