Altamash parasitology


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  • Symbiosis: Any two organisms living in close association, commonly one living in or on the the body of the other, are symbiotic, as contrasted with free living. De Bary 1879
  • Symbiosis: Any two organisms living in close association, commonly one living in or on the the body of the other, are symbiotic, as contrasted with free living. De Bary 1879
  • Ergot, Claviceps purpurea, ergotism
  • Altamash parasitology

    1. 1. PARASITOLOGY Medical parasitology: “the study and medical implications of parasites that infect humans”
    2. 2. Parasitism - a way of life <ul><li>Parasite and Parasitism are terms that define a way of life rather than a coherent and evolutionary related group of organisms </li></ul><ul><li>Symbiosis, Commensalism, Mutualism, Parsitism </li></ul><ul><li>PARASITE – A living organism dependent on another living organism for its survival in the form of nutrition as well as shelter. Parasites may be simple unicellular protozoa or complex multicellular metazoa </li></ul>
    3. 3. Parasitism - a way of life <ul><li>Symbiosis : “Any two organisms living in close association, commonly one living in or on the the body of the other, are symbiotic, as contrasted with free living.” De Bary 1879 </li></ul><ul><li>Commensalism : Sharing the table. One partner benefits but the other is not hurt. </li></ul><ul><li>Mutualism : Both partners benefit. </li></ul><ul><li>Parasitism: One partner (the parasite) harms or lives on the expense of the other (host). </li></ul>
    4. 4. Who is a parasite? <ul><li>Parasites are usually much smaller than their hosts, they also do no kill before eating. </li></ul>
    5. 5. Parasites are found in all groups of organisms
    6. 6. Parasites can be <ul><li>ECTOPARASITE: live on, but not in their hosts (they can nevertheless cause severe illness). Eg lice </li></ul><ul><li>ENDOPARASITE: live within the body and tissues of their hosts. Trypanosomes (which cause sleeping sickness) within the blood of an infected animal . </li></ul><ul><li>TEMPORARY PARASITE </li></ul><ul><li>PERMANENT PARASITE </li></ul><ul><li>FACULTATIVE PARASITE </li></ul><ul><li>OBLIGATORY PARASITE </li></ul>
    7. 8. Infection & infestation <ul><li>Infectious diseases are caused by transmittable parasitic agents including bacteria, viruses, fungi, protozoa and a variety of metazoans commonly referred to as helminths or worms </li></ul><ul><li>Infection usually implies replication of the agent resulting in a growing number of pathogens </li></ul><ul><li>Infestation are characterized by a constant number of pathogens. Severity of disease often depends on infection dose. </li></ul>
    8. 9. Hosts and life cycles Host: “the organism in, or on, which the parasite lives and causes harm <ul><li>The definitive host is by definition the one in which the parasite reproduces sexually </li></ul><ul><li>intermediate hosts the organism in which the parasite lives during a period of its development only” </li></ul><ul><li>Host which actively transmit parasites to humans are often called vectors </li></ul><ul><li>In paratenic or transport hosts no parasite development occurs </li></ul><ul><li>Reservoir host are alternate animal host from which the parasite can be transmitted to humans (zoonosis) or domestic animals </li></ul><ul><li>Accidental host , not suitable for parasite development, but can cause disease </li></ul>
    9. 10. Disease terminology <ul><li>Prepatency : infected but parasite presence can not be detected yet </li></ul><ul><li>Patency : established infection, parasite stages can be detected (malaria parasites in blood smears, worm eggs in feces etc.) </li></ul><ul><li>Incubation period : time between infection and the development of symptoms </li></ul><ul><li>Acute disease can lead to crisis which can resolve in spontaneous healing, chronic infection or death </li></ul><ul><li>Convalescence: Period after healing, absence of infectious agents, no symptoms, in certain case immunity to reinfection </li></ul>
    10. 11. Epidemiology <ul><li>Although parasitic infections occur globally, the majority occur in tropical regions, where there is poverty, poor sanitation and personal hygiene </li></ul><ul><li>Often entire communities may be infected with multiple, different organisms which remain untreated because treatment is neither accessible nor affordable </li></ul><ul><li>Effective prevention and control requires &quot;mass intervention strategies” and intense community education. Examples include: </li></ul><ul><ul><li>General improved sanitation : pit latrines, fresh water wells, piped water </li></ul></ul><ul><ul><li>Vector control : insecticide impregnated bed nets, spraying of houses with residual insecticides, drainage, landfill </li></ul></ul><ul><ul><li>Mass screening and drug administration programmes which may need to be repeated at regular intervals </li></ul></ul>
    11. 12. CLASSIFICATION <ul><li>Parasites --- two main groups: </li></ul><ul><li>Protozoa </li></ul><ul><li>Metazoa (Helminthes) </li></ul><ul><li>Protozoa are further divided into: </li></ul><ul><li>Sarcodina (amebas) </li></ul><ul><li>Sporozoa (sporozoans) </li></ul><ul><li>Mastigophora (flagellates) </li></ul><ul><li>Ciliata (ciliates) </li></ul>
    12. 13. <ul><li>Metazoa (helminthes ) are further divided into: </li></ul><ul><li>Platyhelminthes (flatworms) </li></ul><ul><li>Trematodes (flukes) </li></ul><ul><li>Cestodes (tapeworms) </li></ul><ul><li>Nemathelminthes (roundworms) </li></ul>
    13. 14. PROTOZOA <ul><li>Single-celled Eukaryotes </li></ul><ul><li>Free-living or parasitic </li></ul><ul><li>2 forms: </li></ul><ul><li>Cyst form (infective for humans) & </li></ul><ul><li>Trophozoite form </li></ul><ul><li>Protozoa are grouped as : </li></ul><ul><li>Intestinal protozoa </li></ul><ul><li>Urogenital protozoa </li></ul><ul><li>Blood and tissue protozoa </li></ul>
    14. 15. <ul><li>Intestinal protozoa </li></ul><ul><li>Entamoeba histolytica (ameba) </li></ul><ul><li>Giardia lamblia (flagellate) </li></ul><ul><li>Cryptosporidium parvum (sporozoan) </li></ul><ul><li>2. Urogenital Protozoa: </li></ul><ul><li>Trichomonas vaginalis (flagellate) </li></ul>
    15. 16. <ul><li>Blood & Tissue Protozoa: </li></ul><ul><li>Leishmania species (flagellate) </li></ul><ul><li>Trypanosoma species (flagellate) </li></ul><ul><li>Toxoplasma gondii (sporozoa) </li></ul><ul><li>Plasmodium species (sporozoa) </li></ul><ul><li>Pneumocystis carinii </li></ul>
    16. 17. ENTAMOEBA HISTOLYTICA <ul><li>Occurs worldwide, </li></ul><ul><li>endemic in tropics & subtropics </li></ul><ul><li>ROUTE OF TRANSMISSION: </li></ul><ul><li>– fecal-oral route </li></ul><ul><li> BY contaminated food & water </li></ul>
    17. 18. <ul><li>Sources of infection – carriers (asymptomatic & convalescent), houseflies, cockroaches </li></ul><ul><li>Risks – poverty, lack of hygiene, poor sanitation, mental retardation, male homosexuals </li></ul>
    18. 19. <ul><li>MORPHOLOGY </li></ul><ul><li>E. histolytica has 2 stages: </li></ul><ul><li>Trophozoite </li></ul><ul><li>Non-infective stage </li></ul><ul><li>Found in intestinal & extra-intestinal lesions </li></ul><ul><li>diarrhoeal stools </li></ul><ul><li>Motile (amoeboid movement) & ingest RBCs. </li></ul><ul><li>Mature trophozoite has a single nucleus, even lining of peripheral chromatin & prominent nucleolus (karyosome) </li></ul>
    19. 20. <ul><li>Cyst: </li></ul><ul><li>Infective form for humans </li></ul><ul><li>Mature cyst has 4 nuclei (diagnostic feature) </li></ul><ul><li>Found in non-diarrheal stools </li></ul><ul><li>Not killed by chlorination </li></ul><ul><li>Readily killed by boiling or filtration of water </li></ul>
    20. 22. <ul><li>DISEASES: </li></ul><ul><li>E. histolytica causes: </li></ul><ul><li>Asymptomatic infection (90%) </li></ul><ul><li>Acute intestinal amebiasis (Amebic Dysentery) </li></ul><ul><li>Chronic amebiasis </li></ul><ul><li>Amebic liver abscess </li></ul><ul><li>Infrequently abscess in brain, lungs & other organs </li></ul>
    21. 23. LIFE CYCLE <ul><li>Cysts (infective stage) in contaminated food or water – excystation in intestinal tract – trophozoite (ileum) --- each divides to form 8 trophozoites – colonize cecum & colon – invasion of epithelium– till muscularis layer (flask shaped ulcers) – reaches sub mucosa- --- portal blood– liver abscess. </li></ul><ul><li>Some trophozoites in intestine encyst – passed in stools – contaminate food & water. </li></ul>
    22. 27. Clinical presentation <ul><li>1. Acute intestinal amebiasis: dysentry, lower abdominal discomfort, tenesmus, & flatulence. </li></ul><ul><li>2. Chronic amebiasis </li></ul><ul><li>3. Amebic abscess: if in liver, cause right upper quadrant pain, weight loss, fever & a tender, enlarged liver. </li></ul>
    23. 28. <ul><li>LABORATORY DIAGNOSIS: </li></ul><ul><li>Stool Examination: </li></ul><ul><li>(Formed stools contain cysts & diarrheal stools contain trophozoites) </li></ul><ul><li>Wet mount in saline, Iodine-stained, or fixed trichrome stained preparation </li></ul><ul><li>For motile trophozoites, stools should be examined within 1 hour.Trophozoite of E. histolytica is differentiated from other amoeba (E.coli) by: </li></ul><ul><li>Nucleus of trophozoite </li></ul><ul><li>For cysts, at least 3 samples should be collected. </li></ul><ul><li>Size of cyst & number of its nuclei. (Newly formed cyst has 2 nuclei, glycogen mass & chromidial bars) </li></ul>
    24. 32. <ul><li>Other tests </li></ul><ul><li>Detection of E. histolytica antigen in stool </li></ul><ul><li>PCR assay. </li></ul><ul><li>Serology to diagnose invasive amebiasis – (IHA – indirect hemagglutination test) </li></ul>
    25. 33. <ul><li>PREVENTION </li></ul><ul><li>Purification of water supplies </li></ul><ul><li>Good personal hygiene (esp. hand washing) </li></ul><ul><li>Prohibit use of ‘night soil’ </li></ul><ul><li>Cook vegetables </li></ul>
    26. 34. <ul><li> AMOEBIC </li></ul><ul><li> DYSENTERY </li></ul><ul><li>Gradual onset </li></ul><ul><li>Copious amount </li></ul><ul><li>of stools </li></ul><ul><li>Offensive odor </li></ul><ul><li>Dark red </li></ul><ul><li>Few pus cells </li></ul><ul><li>Trophozoites of </li></ul><ul><li>E. histolytica </li></ul><ul><li>seen </li></ul><ul><li>BACILLARY DYSENTERY </li></ul><ul><li>Acute onset </li></ul><ul><li>Small amount of stools </li></ul><ul><li>Odorless </li></ul><ul><li>Bright red </li></ul><ul><li>Many pus cells </li></ul><ul><li>Not seen </li></ul>
    27. 35. <ul><li> AMOEBIC </li></ul><ul><li> LIVER ABSCESS </li></ul><ul><li>Gradual onset </li></ul><ul><li>Organism responsible is E. histolytica </li></ul><ul><li>trophozoites of </li></ul><ul><li>E. histolytica sticking to wall of abscess. </li></ul><ul><li>Anchovy sauce </li></ul><ul><li>PYOGENIC LIVER ABSCESS </li></ul><ul><li>Malaise to acute presentation </li></ul><ul><li>Organism may be E.coli, anaerobes eg Bacteroides </li></ul><ul><li>Many pus cells </li></ul><ul><li>No trophozoites </li></ul>