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

Transcript

  • 1. PARASITOLOGY Medical parasitology: “the study and medical implications of parasites that infect humans”
  • 2. Parasitism - a way of life
    • Parasite and Parasitism are terms that define a way of life rather than a coherent and evolutionary related group of organisms
    • Symbiosis, Commensalism, Mutualism, Parsitism
    • 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
  • 3. Parasitism - a way of life
    • 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
    • Commensalism : Sharing the table. One partner benefits but the other is not hurt.
    • Mutualism : Both partners benefit.
    • Parasitism: One partner (the parasite) harms or lives on the expense of the other (host).
  • 4. Who is a parasite?
    • Parasites are usually much smaller than their hosts, they also do no kill before eating.
  • 5. Parasites are found in all groups of organisms
  • 6. Parasites can be
    • ECTOPARASITE: live on, but not in their hosts (they can nevertheless cause severe illness). Eg lice
    • ENDOPARASITE: live within the body and tissues of their hosts. Trypanosomes (which cause sleeping sickness) within the blood of an infected animal .
    • TEMPORARY PARASITE
    • PERMANENT PARASITE
    • FACULTATIVE PARASITE
    • OBLIGATORY PARASITE
  • 7.  
  • 8. Infection & infestation
    • 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
    • Infection usually implies replication of the agent resulting in a growing number of pathogens
    • Infestation are characterized by a constant number of pathogens. Severity of disease often depends on infection dose.
  • 9. Hosts and life cycles Host: “the organism in, or on, which the parasite lives and causes harm
    • The definitive host is by definition the one in which the parasite reproduces sexually
    • intermediate hosts the organism in which the parasite lives during a period of its development only”
    • Host which actively transmit parasites to humans are often called vectors
    • In paratenic or transport hosts no parasite development occurs
    • Reservoir host are alternate animal host from which the parasite can be transmitted to humans (zoonosis) or domestic animals
    • Accidental host , not suitable for parasite development, but can cause disease
  • 10. Disease terminology
    • Prepatency : infected but parasite presence can not be detected yet
    • Patency : established infection, parasite stages can be detected (malaria parasites in blood smears, worm eggs in feces etc.)
    • Incubation period : time between infection and the development of symptoms
    • Acute disease can lead to crisis which can resolve in spontaneous healing, chronic infection or death
    • Convalescence: Period after healing, absence of infectious agents, no symptoms, in certain case immunity to reinfection
  • 11. Epidemiology
    • Although parasitic infections occur globally, the majority occur in tropical regions, where there is poverty, poor sanitation and personal hygiene
    • Often entire communities may be infected with multiple, different organisms which remain untreated because treatment is neither accessible nor affordable
    • Effective prevention and control requires "mass intervention strategies” and intense community education. Examples include:
      • General improved sanitation : pit latrines, fresh water wells, piped water
      • Vector control : insecticide impregnated bed nets, spraying of houses with residual insecticides, drainage, landfill
      • Mass screening and drug administration programmes which may need to be repeated at regular intervals
  • 12. CLASSIFICATION
    • Parasites --- two main groups:
    • Protozoa
    • Metazoa (Helminthes)
    • Protozoa are further divided into:
    • Sarcodina (amebas)
    • Sporozoa (sporozoans)
    • Mastigophora (flagellates)
    • Ciliata (ciliates)
  • 13.
    • Metazoa (helminthes ) are further divided into:
    • Platyhelminthes (flatworms)
    • Trematodes (flukes)
    • Cestodes (tapeworms)
    • Nemathelminthes (roundworms)
  • 14. PROTOZOA
    • Single-celled Eukaryotes
    • Free-living or parasitic
    • 2 forms:
    • Cyst form (infective for humans) &
    • Trophozoite form
    • Protozoa are grouped as :
    • Intestinal protozoa
    • Urogenital protozoa
    • Blood and tissue protozoa
  • 15.
    • Intestinal protozoa
    • Entamoeba histolytica (ameba)
    • Giardia lamblia (flagellate)
    • Cryptosporidium parvum (sporozoan)
    • 2. Urogenital Protozoa:
    • Trichomonas vaginalis (flagellate)
  • 16.
    • Blood & Tissue Protozoa:
    • Leishmania species (flagellate)
    • Trypanosoma species (flagellate)
    • Toxoplasma gondii (sporozoa)
    • Plasmodium species (sporozoa)
    • Pneumocystis carinii
  • 17. ENTAMOEBA HISTOLYTICA
    • Occurs worldwide,
    • endemic in tropics & subtropics
    • ROUTE OF TRANSMISSION:
    • – fecal-oral route
    • BY contaminated food & water
  • 18.
    • Sources of infection – carriers (asymptomatic & convalescent), houseflies, cockroaches
    • Risks – poverty, lack of hygiene, poor sanitation, mental retardation, male homosexuals
  • 19.
    • MORPHOLOGY
    • E. histolytica has 2 stages:
    • Trophozoite
    • Non-infective stage
    • Found in intestinal & extra-intestinal lesions
    • diarrhoeal stools
    • Motile (amoeboid movement) & ingest RBCs.
    • Mature trophozoite has a single nucleus, even lining of peripheral chromatin & prominent nucleolus (karyosome)
  • 20.
    • Cyst:
    • Infective form for humans
    • Mature cyst has 4 nuclei (diagnostic feature)
    • Found in non-diarrheal stools
    • Not killed by chlorination
    • Readily killed by boiling or filtration of water
  • 21.  
  • 22.
    • DISEASES:
    • E. histolytica causes:
    • Asymptomatic infection (90%)
    • Acute intestinal amebiasis (Amebic Dysentery)
    • Chronic amebiasis
    • Amebic liver abscess
    • Infrequently abscess in brain, lungs & other organs
  • 23. LIFE CYCLE
    • 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.
    • Some trophozoites in intestine encyst – passed in stools – contaminate food & water.
  • 24.  
  • 25.  
  • 26.  
  • 27. Clinical presentation
    • 1. Acute intestinal amebiasis: dysentry, lower abdominal discomfort, tenesmus, & flatulence.
    • 2. Chronic amebiasis
    • 3. Amebic abscess: if in liver, cause right upper quadrant pain, weight loss, fever & a tender, enlarged liver.
  • 28.
    • LABORATORY DIAGNOSIS:
    • Stool Examination:
    • (Formed stools contain cysts & diarrheal stools contain trophozoites)
    • Wet mount in saline, Iodine-stained, or fixed trichrome stained preparation
    • For motile trophozoites, stools should be examined within 1 hour.Trophozoite of E. histolytica is differentiated from other amoeba (E.coli) by:
    • Nucleus of trophozoite
    • For cysts, at least 3 samples should be collected.
    • Size of cyst & number of its nuclei. (Newly formed cyst has 2 nuclei, glycogen mass & chromidial bars)
  • 29.  
  • 30.  
  • 31.  
  • 32.
    • Other tests
    • Detection of E. histolytica antigen in stool
    • PCR assay.
    • Serology to diagnose invasive amebiasis – (IHA – indirect hemagglutination test)
  • 33.
    • PREVENTION
    • Purification of water supplies
    • Good personal hygiene (esp. hand washing)
    • Prohibit use of ‘night soil’
    • Cook vegetables
  • 34.
    • AMOEBIC
    • DYSENTERY
    • Gradual onset
    • Copious amount
    • of stools
    • Offensive odor
    • Dark red
    • Few pus cells
    • Trophozoites of
    • E. histolytica
    • seen
    • BACILLARY DYSENTERY
    • Acute onset
    • Small amount of stools
    • Odorless
    • Bright red
    • Many pus cells
    • Not seen
  • 35.
    • AMOEBIC
    • LIVER ABSCESS
    • Gradual onset
    • Organism responsible is E. histolytica
    • trophozoites of
    • E. histolytica sticking to wall of abscess.
    • Anchovy sauce
    • PYOGENIC LIVER ABSCESS
    • Malaise to acute presentation
    • Organism may be E.coli, anaerobes eg Bacteroides
    • Many pus cells
    • No trophozoites