Protozoa - Intestinal And Urogenital Protozoa 151d6y

OUTLINE

PROTOZOA  General Introduction to protozoa  Definition  Diversity and Medical importance of protozoa  General morphology protozoa  Size, Shape etc  Cellular structure and organization  Basic properties  Locomotion  Reproduction  Feeding, Metabolism, Excretion and Encystment  Classification  General characteristics of the five main groups

What are Protozoa ?

What are Protozoa? proto = first zoa = animals =single-celled eukaryotic organisms =kingdom Protista =Vary in size (3-2000 mm).

What….? =Unknown until the invention of the microscope in 1675 =First recognized by antony van leewenhoek in 1676 = He describe it as little animal or animacula

Protozoan diversity = protozoa are extremely diverse organisms and found in a variety of niches =>200,000 named species = Most species are free-living in = Freshwater = marine environments = decaying organic matter and soil =Some are beneficial to mankind by: = being part of the food chain = serving as experimental subjects.

Protozoan Diversity = Few are adapted to a parasitic life but all plant and animal species have at least one protozoan parasite

= ~10,000 are parasites in a wide range of hosts = Vertebrate = invertebrate = Plants = ~20 human pathogens = Adapted to life in a wide range of sites within the host

Ecological Niches in the Human Body: – Skin: Leishmania – Eye: Acanthamoeba – Mouth: Amoebae and flagellates (usually non-

pathogenic) – Gut: Giardia, Entamoeba (and invasion to liver), Cryptosporidium, Isospora, Balantidium – G.U. tract: Trichomonas

Ecological…. – Bloodstream: Plasmodium, Trypanosoma – Spleen: Leishmania – Liver: Leishmania, Entamoeba

– Muscle: Trypanosoma cruzi – CNS: Trypanosoma, Naegleria, Toxoplasma, Plasmodium

Importance of protozoa • Medical importance

– Cause of more sickness and death, than any other disease-causing organisms – reduced working capacity – Loss of productivity

• Veterinary importance – Loss of productivity – Death – reduced meat and milk production, – reduced reproductive potential – reduced working capacity – Potential losses

Protozoa ..“eukaryote”..has genetic material encased in a nuclear membrane (unlike bacteria and Viruses) ..Classified traditionally by: morphology(eg. organelles of locomotion) life cycle mechanisms of reproduction etc.

Taxonomy of Protozoan • Subkingdom

Protozoa

– Phylum Sarcomastigophora • Subphylum

Sarcodina • Ex. Entamoeba

• Subphylum

Mastigophora • Ex. Giardia • Leishmania • Trypanosoma

– Phylum Apicomplexa • Ex Plasmodia (malaria) • Toxoplasma gondii

– Phylum Ciliophora • Balantidium

• Mastigophora: movement with flagella - e.g. Trichomonas, Giardia

• Sarcodina: pseudopodia – e.g. Entamoeba histolytica

• Apicomplexa: apical complex, no locomotor apparatus – e.g. cryptosporidium, malaria, toxoplasma

• Ciliophora: movement with cilia – e.g. Balantidium.

in protozoans • Trophozoite: any stage in a protozoan’s life cycle which can ingest food. In practice also refers to the motile form. • Cyst: the non motile form which is protected by a distinct membrane or cyst wall. This is an infective stage of the parasite. • Excystation: the process of emergence of the trophozoite from the cyst (vs. encystation) • Pseudopod: literally means false foot; temporary cytoplasmic processes at the surface of the trophozoite

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Unlike their friend they do not lyse host tissue! Feed on bacteria, protozoa, yeasts and occasionally blood cells if available VERY important to diagnose infection correctly or patient will undergo unnecessary drug treatment Further reading 24

Symptoms/Pathogenesis: Virulence factors: amoebaphore

lectin,

cysteine

protease

&

The 1st stage invasive starts when adhesion to colonic mucins via parasite surface Gal/GalNAc lictin The hallmark of amoebiais include: degradation extracellular matrix by amebic protease production of toxic factors activation of host cells from host immune system killing & phogocytosis human cells

E. histolytica induces apoptosis and phagocytosis of the

human target cells

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Persisting fever Rarely diarrhea

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MECHANISMS OF CYTOTOXICITY At least 5 mechanisms have been advanced to explain the pathogenicity of virulent strains of Entamoeba. Hallmarks of amoebiasis include: degradation of the extracellular matrix (ECM) by amoebic proteases, production of toxic factors, activation of cells from the host immune system, killing and phagocytosis of human cells, 1. Direct s with the host tissues. Example: adherence to the host cell by the release of adhesin molecules. 2. Release of soluble toxic metabolites. Example: amoebapore are capable of forming a hole in a target cell. 3. High enzymatic activities of the amoebas Example: enzymes released by the parasite damaging the host cell. . 4. Interfering with the immune response of the host. Example: Antigens released by the amoeba cell can lead to:      

inflammatory reaction allergies Immunodepression over stimulation of cytokines formation of immune complexes formation of autoantibodies

5. E. histolytica induces apoptosis of the host cells during tissue invasion

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E. histolytica vs E. dispar Brumpt 1949, proposed to establish a new species of Entamoeba amoebae that are not pathogenic. In 1993, it was decided that the invasion form will be called called E. histolytica. The non-invasive invasive form will be called E. dispar. The 2 amoebae can’t be distinguished by microscopic observation.

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Phylum: Sarcomastigophora Flagellates Amebas Giardia, Trichomonas Entamoeba • Early-diverging Eukaryotes • Facultative Anaerobes Carbohydrate metabolism is anaerobic • Lack mitochondria • Extracellular parasites Do not invade host cells Adhere to plasma membrane of host cells -dependent cytotoxicity Mechanical damage to host tissues • Replicate and divide within the host by binary fission • All are killed by treatment with Metronidazole, a drug that selectively kills anaerobic cells

GIARDIASIS Infection with the protozoan parasite Giardia lamblia Giardia duodenalis most common name used. G. intestinales and G. lamblia are also used. Giardia spp. can parasitize the intestinal tract of a wide range of vertebrates, including humans. Disease is prevalent in children attending day care centers. In addition the domestic dog and certain wild animals serve as hosts. Most common protozoan disease in the United States. The distribution is cosmopolitan. Transmission of Giardia is predominantly by ingestion of food or water contaminated with cyst

EPIDEMIOLOGY • Worldwide distribution • Common in areas with poor sanitary conditions Seasonal with peak during late summer in UK, USA and Mexico • Prevalence: 2-5% in industrialized countries 20-30% in developing countries •Travelers, hikers, campers are at risk. Swallowing water while swimming, drinking tap water, eating lettuce. • Risk groups in the US: travelers, children in day cares and homosexual men

TRANSMISSION • Reservoir-human and possibly other mammals (zoonotic?) •Infective cysts in feces: 10-25 cysts sufficient • Fecal contamination of water • Feces for fertilizer • Defective piping • Flies • Soiled hands

CLINICAL FEATURES •Incubation period : 1-2 weeks •Majority of infected individual are asymptomatic SYMPTOMS:

•Diarrhea with loose, foul-smelling stools •Flatulence •Abdominal cramps and bloating •Nausea •Anorexia •Malaise •Weight loss •Prolonged symptoms •Malabsorption

DIAGNOSIS • Identification of cysts or trophozoites in fecal specimens • May need to be repeated • Detection of Giardia antigens in feces. • Serodiagnosis is not useful TREATMENT •Metronidazole: •Quinacrine•Tinidazole•Furazolidone- approved by the FDA for giardiasis •Paranomycin- used for pregnant women •Nitazoxanide: recently approved for giardiasis and cryptosporidosis in children

Trichomoniasis

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Trichomonas

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Life cycle of T. vaginalis

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Morphology of T. vaginalis

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Epidemiology T. vaginalis

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Clinical symptoms T. vaginalis

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Yellow vaginal discharge due to T. vaginalis

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Treatment of Trichomoniasis

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Intestinal coccidian Cryptosporidium ,Isospora ,Cyclospora General characteristics

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Considered as opportunistic parasite in immunocompromissed person

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Complete entire life cycle in single host

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Within the intestinal epithelial cells of the host

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Characterized by a thick walled oocyst excreted in feces

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Are transmitted by the fecal-oral route

Cryptosporidium Species: C. parvum  A coccidean parasite implicated in intestinal  Disease primarily among immune-compromised patient  1985 first reported case in philippines associated with intractable diarrhea in immune-compromised (AIDS) patient  Self-limiting diarrhea in immuno-competent persons  Profuse, watery diarrhea associated with AIDS (life threatening)

• 1976 considered as natural parasite of animal especially calves causing diarrheal diseases • Infect wide range of animal hosts (fish-humans) – C. hominis & C. parvum are species mostly causing disease in humans

– C. hominis infects only humans but C. parvum also infects many other mammals – C. felis, C. meleagridis, C. canis, and C. muris infections have also been reported

• Geog. Dist.: = Worldwide distribution • Morphology: = oocyst round or slightly oval-shaped,

Transmission • Mainly through the ingestion and possibly inhalation of sporulated oocysts • mainly through contaminated water & • Occasionally food sources, such as chicken salad • fecal-oral transmission (monoxenous) – anthroponotic transmission – autoinfection – zoonotic transmission

Waterborne Cryptosporidiosis • human infection usually waterborne and acquired by fecal-oral route • highest prevalence of disease in areas with unreliable

water and food sanitation

Factors Favoring Waterborne Cryptosporidiosis • Small size of oocysts (4-5 mm) • Reduced host specificity and monoxenous development • Close associations between human and animal hosts • Large number of oocysts excreted (up to 100 billion per calf per day) • Low infective dose (<30) • Robust oocysts; resistant to chlorine

Disease: Cryptosporidiosis = human infection usually waterborne and acquired by fecal-oral route = highest prevalence of disease in areas with unreliable water and food sanitation = extraintestinal infection of the respiratory tract, biliary tract and pancreas may occur.

Clinical Features • Varry from asymptomatic to severe, life-threatening illness; • infection usually self-limiting diarrhea of 1-2 weeks duration charactrized by copious watery diarrhea, vomiting, intense abdominal pain, anorexia and

weakness • among immunocompromised patient (AIDS)  develops severe chronic diarrhea which may last for months  malabsorption

Cyclospora Specie: C. cayetanensis = was established to cause human diarrhea in 1990 =1986 cases of prolonged watery diarrhea among

immunocompromised (AIDS) patient has been reported worldwide =Species Name C.Cayetanensis was given in 1993 =Initially called ‘cyano-bacteria like body’ (CLB) or large cryptosporidium

Epidemiology: = More common in tropical and sub-tropical areas = case of cyclospora infection was reported in papua, new guinea

= Subsequent cases has been reported from most part of the world

Epidemology… = Infection caused by cyclospora can be acquired by drinking contaminated water (fecal-oral) = More associated with food-borne outbreaks ( social

events, weddings, etc) = Parasite infect vertebrates including reptiles, insect & rodents

Clinical Features Disease: Cyclosporiasis = disease is clinically indistinguishable from cryptosporidiosis and Isosporiasis = self-limiting, characterized by persistent watery diarrhea that ends to recur in a relapsing pattern and last for

3-4 wks, = associated with abdominal cramps, nausea, vomiting, low grade fever, weight loss and anorexia

Isospora Specie: Isospora belli Epidemiology • wide geographical distribution (higher prevalence in warmer climates) • the least common of the three intestinal coccidia that infect

humans • transmitted through intake of fecally contaminated food and drink with oocyst

Clinical feature • Disease: Isosporosis/Intestinal coccidiosis • often asymptomatic (seldom reported)

• symptoms range from mild gastro-intestinal distress to severe dysentery • mild self-limiting infection charac. by fever, colicky abdominal pain, severe diarrhea, steatorrhea (fatty stool) and weight loss. • often self-limiting, but can become chronic (wasting, anorexia) • symptoms more severe in AIDS patients

Pathology • intracellular development occurs in the intestinal mucosa  mucosal atrophy • chronic diarrhea (months to years) abdominal discomfort, low grade fever

Intestinal Coccidia Treatment • paromomycin for Cryptosporidium • modest benefit • lowers parasitemia in AIDS • trimethoprim-sulfamethoxazole for Cyclospora and Isospora

Intestinal coccidian •

Summary – – – – – –

are opportunistic parasite in immunocompromissed person Have both sexual and asexual reproduction Require single host to comlete their entire life cycle characterized by a thick walled oocyst excreted in faeces Are transmitted by the fecal-oral route Laboratory diagnosis is by finding the oocyst in faeces

Intestinal Coccidia- Summary • Got medical attention after the emergence of HIV/AIDS • Fecal-oral or contaminated food and water are means of transmission • Simple lifecycle and reproduce Sexually and asexually infection leads to acute, watery diarrhea; self limiting in immunocompetent individuals but significant, chronic illness in the immunosuppressed may occur

• characterized by a thick walled oocyst excreted in faeces • oocyst stage :Infective and diagnostic stage • Laboratory dx; finding oocyct in stool specimen