Level 200 Parasitology parasites lecture.pptx

concepts of parasitology

1. Introduction to Parasitology and Parasitism MLAB 212 Parasitology Component DR. ISAAC ANIM-BAIDOO

2. Introduction Parasitic diseases form significant proportion of microbial infections Infections range from relatively innocuous to fatal Form 20% of all infectious diseases Poor sanitation & personal hygiene lead to spread of infections 30% of World’s population, infected with Ascaris lumbricoides Some parasitic infections have increased in importance with advent of AIDS Though common in the tropics, people in sub-tropical & temperate regions are affected due to trans continental travels and tourism. Need to study and understand nature of parasitic infections in order to control them

3. Objectives of study By end of lecture, students should be able to Describe animal associations Explain parasitism, and give examples of parasites Describe how parasites can influence their host Define important Parasitology terms Explain classification of parasites

4. Animal Associations Parasite An organism that lives on/in another organism ( host ) and derives nourishment without rapidly destroying it Homospecific / Homogenetic Association between animals of same species or genotype eg . Herds, colonies, flocks Heterospecific / Heterogenetic Association between animals of different species or genotype. This is complex and has been described by several terms

5. Symbiosis (Living together) Involves levels of intimacy between the animals / organisms Symbiosis Phoresis Commensalism Mutualism Parasitism Loose association Intimate association

6. Phoresis and Commensalism Loose associations , usually no metabolic dependence , are basically companionships (shelter, support, or transport) Mutualism and Parasitism Mostly intimate , in which metabolism or physiology of one species is dependant on the other. In mutualism , both symbiont and host benefit. Are virtually inseparable /No metabolic or physiological dependence Eg . Flagellates and termites

7. Parasitism Association between 2 different organisms which is intimate and continuous relationship Parasite lives at the expense of host Host provides nutrients, shelter, transport, etc Parasites usually do not kill the host Some parasites undergo part of their life-cycle in the host.

8. Parasite relationship with host Depending on host’s immune responses the host-parasite relationship may result in either overt or covert disease Could favour the host No disease Elimination of the parasite Could favour the parasite Cause disease Gradual elimination of host Favour both Co-existence/chronic/ asymptomatic relationship

9. Nature of influence of Parasites on host Complex and varies with each parasite or host Parasite Species – level of organization- Physiology /Morphology Capacity to cause disease in the host (virulence/invasiveness) Host Level of organization of host Host response or reaction to infection Site of infection

10. Examples of influences of Parasites on Host Mechanical (attachment/injuries/movements, etc) Injuries resulting from attachment of organs ( traumatic ) ; egg ( trematodes ), scoleces ( cestodes ), buccal cavity (hookworms) Movement of parasites within or on host (may be irritating) eg . CLM ( cutaneous larva migrans ) by Ancylostoma feline & A. caninum Penetration of skin by larval stages of Schistosoma sp., hookworm, S trongyloides

11. Partial and complete obstruction of certain parts of the host, e.g. Ascaris blocking alimentary canal, liver flukes blocking bile ducts, effects of filarial worms (elephantiasis) Pressure on tissues and organs (impairment of functions) e.g. worms found in the kidney and lungs, larval cestodes in tissues, eg hydatid disease- cyst formed by growth of immature forms of tapeworm Bites of ectoparasites

12. Destruction of substances necessary for normal development of the host metabolism Use of host food /blood by parasites. Eg . Human Taenia tapeworm absorb digested food from host Secretion of anti-coagulants leading to loss of blood Use of host food components, e.g. fish tapeworm ( Diphyllobothrium latum ) competes with host for Vitamin A & B2

13. Production of inhibitory substances for food uptake

14. Production of toxic substances that elicit local or general immune reactions Toxic substances which give general other than local pathogenic response Toxins may be antigens which elicit host response Toxins may be associated with changes in blood composition, e.g. rise in eosinophilia- hookworm infections, production haemolytic substances by hookworm lead to a drop in RBC count Toxins that are neurotoxic (nervous disorders) e.g. Diphyllobothrium latum , Ascaris , Trichuris trichiura

15. Activities of the parasite which may introduce other organisms (bacteria/viruses/arthropods) or substances into the host Bacterial inflammation of the appendix due to presence of Trichuris trichiura in appendix Entamoeba histolytica / Balantidium coli infection open way for other bacterial (secondary) infection Helminths that carry other organisms with them Ascaris migration in the host body carrying other substances with it

16. Types of Parasites Endoparasites Organisms which live inside or within their hosts (in the gut, blood, lungs, tissues, etc) Eg . G. lamblia , E. histolytica , T. solium Ectoparasites Organisms that live on the outside of their hosts, usually attached to the skin, hairs, etc. Eg . Fleas, Ticks, Lice, Midges, etc Facultative Parasites Can live either parasitic or non-parasitic existence

17. Obligate Parasites Obliged to live a parasitic existence and are incapable of surviving outside the host environment Opportunistic Parasites Parasites that take advantage of the host immune or physiological state to infect the host.

18. Other common terms of reference: What is……..? Pathogenic or non-pathogenic ( producing disease/not producing disease) Invasive or non-invasive ( ability of parasite to spread into tissues/organs) Virulent or non-virulent ( Virulence: degree of pathogenicity or disease producing ability of the parasite)

19. What is…..? Infection Process by which a disease is transmitted via micro-organisms from one person to the other Infestation A term applied to the occurrence of animal parasites in the intestine, hair, or clothing

20. Reservoir host An organism in which a parasite resides or in which a parasite which infects man (human) is maintained in the absence of the human host. They may be mammals, eg . Pigs, Cattle, etc or the environment ( eg . Contaminated soil/human) Zoonosis Parasitic infections in which the normal host is an animal but can produce disease in humans if they become accidentally infected. Eg . Leishmaniasis , Chagas , Trichinellosis / Echinococcus , Giardiasis

21. Classification of Parasites Two major groups of endoparasites Endoparasites Protozoa Metazoa

22. Protozoa General Comments/Characteristics…? Are single-celled/unicellular eukaryotes Most are less than 50µm in size Have a range of sizes and forms depending on class/group As in all eukaryotes, their nucleus is enclosed in a membrane Other than ciliates all protozoa have vesicular nucleus (bladder-like, bubble-like, pouch, usually fluid-filled) with scattered chromatin giving a diffuse appearance to the nucleus.

23. Protozoa structure/characteristics Continuation…..? Some vesicular nuclei contain a central body called the endosome or karyosome Endosome lacks DNA in parasitic amoeba and trypanosomes Ciliates have both micro and macro nuclei Have projecting locomotory structures like pseudopodia, cilia, and flagella Have various shapes (spherical, oval, bizarre, etc ) or could be shapeless

24. Protozoan characteristics………….? Their distinctive shapes, maintained by rigid outer surface layer (Pellicle) Cytoplasm, differentiated into ectoplasm & endoplasm Have organelles (compact nucleus, vesicles, Golgi apparatus, mitochondria, lysosomes , food vacuoles, etc )

25. Examples of Common Protozoan Parasites Balantidium coli Naegleria sp Endolinax nana Iodamoeba butschlii Acanthamoeba sp Giardia lamblia Trichomonas vaginalis T. hominis /T. tenax Entamoeba histolytica Plasmodium sp Isospora belli Cryptosporidium sp Toxoplasma gondii Trypanosoma sp Chilomastix mesnili Leishmania sp.

26. Classification of Protozoans Phylum Protozoa Subphylum Sarcomastigophora 3.Subphylum Ciliophora eg . Balantidium 4.Subphylum Apicomplexa Coccidia ( Microspora ) ( Sporozoa ) 1.Sarcodina Eg . Entamoeba histolytica Naegleria sp Plasmodium sp Isospora belli Cryptosporidium sp Toxoplasma gondii Sarcocystis 2 . Mastigophora Intestinal/other flagellates eg . Giardia Haemoflagellates eg . Trypanosoma

27. Basis of classification Originally, classification was based on morphological characteristics (microscopy) Biochemical methods (isoenzyme analysis) Molecular probes ( PCR -Polymerase chain reaction)

28. Sub-Phylum Sarcodina Shapeless Move by means of pseudopodia (cytoplasm protrusions) Body is divided into ectoplasm(clear) and endoplasm(granular) Reproduction is by simple binary fission Food taken in through food vacuoles Food digested into glycogen Infective stage is the cyst

29. Diagram of E. histolytica 1. Chromatoid bodies are bead-like 2. Karyosome is usually small and compact 3. Presence of RBCs (diagnostic) cyst trophozoite

30. Cyst:10-20 μ m Dormant/resistant stage Spherical 1-4 nuclei, (4 in mature cysts) Bluntly rounded chromatoidal bars

31. Sub-Phylum Mastigophora Move by means of flagella Reproduction by binary fission Forms like Leishmania contain additional characteristics i.e. kinetoplast In haemoflagellates most have single flagellum Infective stage is cyst

32. Diagram of Giardia lamblia Bilateral symmetry 4 pairs of flagella 2 nuclei and 2 axonemes

33. Diagram of Trichomonas vaginalis Have undulating membrane bounded by a flagellum Have 4-5 anterior flagella for movement Have axostyle which extends beyond the body

34. Sub-Phylum Ciliophora Move by means of cilia Have two dis-similar nuclei (micro and macro) Reproduce by binary fission Have contractile and food vacuoles Infective stage is the cyst Have cytostomes (cell mouth) and cytophage

35. Diagram of Balantidium coli Presence of cilia Presence of micro/macro nuclei Presence of cytostome/ cytopharynx

36. Wet preparation of Balantidium trophozoite

37. Sub-phylum Apicomplexa Are usually organ and tissue parasites Reproduction is by both schizogony and sporogony Transmission is by arthropods or ingestion of oocyst.

38. A. Plasmodium young trophozoites (ring forms) B. Plasmodium gametocyte

39. Cryptosporidium oocyst (acid fast stain)-

40. Forms of reproduction in Protozoa Binary & Multiple fission A. Binary fission (asexual) Organism divides into two (Duplication) Plane of division depends on the group/class Sarcodina : Plane of division is random Flagellates: Plane of division is longitudinal Ciliates: Plane of division is transverse

41. Endodyogeny (asexual) Common in Toxoplasma gondii and some related organisms 2 daughter cells form within the parent cell which then ruptures to release smaller progeny which grow to full size

42. Endodyogeny in Toxoplasma gondii 2 IMCs develop in middle of cell (from what appears to be a rudimentary conoid and microtubule-organizing center (polar ring). As the IMCs extend from these structures, the nucleus (N) and mitochondrion ( Mitoch .) divide into these membranous outlines. Nascent apical organelles (NO) develop within the anterior poles as the daughter cells grow.

43. Morphology of Toxoplasma - Eventually, the entire cytoplasm is divided between the daughters and the IMC of the mother dissociates. -A cleavage furrow divides the cells from the anterior pole. -This division continues down the length of the cells until it reaches the posterior end, where it can leave a residual body connecting the two daughters .

44. B. Multiple fission ( i ) Schizogony (asexual) Nucleus of organism divides repeatedly before the division of the cytoplasm (cytokinesis) Division leads to production of uni -nucleate daughter cells ( merozoites ) Cells in which the division occurs is referred to as the schizont

45. ii. Sporogony (sexual) After fusion of gametes (fertilization) Involves encystation of the zygote to form oocyst Formation of daughter cells referred to as sporozoites .

46. Life cycle of Plasmodium (illustration of schizogony) 1) Sporozoites, injected through the skin by female anopheline mosquito; 2) sporozoites infect hepatocytes; 3) some sporozoites develop into hypnozoites ( P. vivax and P. ovale ): 4) liver stage parasite develops; 5 – 6) tissue schizogony; 7) merozoites are released into the circulation; 8) ring stage trophozoites in red cells; 9) erythrocytic schizogony; 10) merozoites invade other red cells; 11) some parasites develop into female (macro-) or male (micro-) gametocytes, taken up by the mosquito; 12) mature macrogametocyte and exflagellating microgametocytes; 13) ookinete penetrates gut wall; 14) development of oocyst; 15) sporozoites penetrate salivary glands.

47. Conclusion 1. Parasitology has been explained 2. Some common terminologies in Parasitology have been discussed 3. Common examples of parasites have been mentioned 4. Classification of parasites has been described 5. Morphological features of Protozoans have been discussed