ParasitologyParasitology

ProtozoaProtozoa

Are single celled animalsAre single celled animalsTrophozoites are motileTrophozoites are motileCysts are involved in transmissionCysts are involved in transmission

GENERALITIES:

Parasites are organisms that obtain food Parasites are organisms that obtain food and shelter by living on or within another and shelter by living on or within another organism.organism.

The parasite derives all benefits from The parasite derives all benefits from association and the host may either not be association and the host may either not be harmed or may suffer the consequences of  harmed or may suffer the consequences of  this association, a parasite disease. this association, a parasite disease.

The parasite is termed obligate when it can The parasite is termed obligate when it can live only in association with a host or it is live only in association with a host or it is classified as facultative when it can live classified as facultative when it can live both in or on a host as well as in a free both in or on a host as well as in a free form. form.

Parasites which live inside the body Parasites which live inside the body are termed endoparasites whereas are termed endoparasites whereas those which exist on the body those which exist on the body surface are called ectoparasites. surface are called ectoparasites.

Parasites that cause harm to the host Parasites that cause harm to the host are pathogenic parasites while those are pathogenic parasites while those that benefit from the host without that benefit from the host without causing it any harm are known as causing it any harm are known as commensals commensals

What needs to be known?What needs to be known?

Organism name ( scientific & Organism name ( scientific & common)common)

Morphology (cyst, egg, larva, Morphology (cyst, egg, larva, tophozoite, adult – M & F )tophozoite, adult – M & F )

EtiologyEtiologyEpidemiologyEpidemiologyLife CycleLife CycleSymptoms, Pathology, ImmunologySymptoms, Pathology, ImmunologyDiagnosis, Treatment & PreventionDiagnosis, Treatment & Prevention

INTESTINAL AND LUMINAL INTESTINAL AND LUMINAL PROTOZOA   PROTOZOA  

Organism that harbors the parasite and suffers Organism that harbors the parasite and suffers a loss caused by the parasite is a a loss caused by the parasite is a hosthost. .

The host in which the parasite lives its adult The host in which the parasite lives its adult and sexual stage is the and sexual stage is the definitivedefinitive host host

The host in which a parasite lives as the larval The host in which a parasite lives as the larval and asexual stage is the and asexual stage is the intermediateintermediate host. host.

Other hosts that harbor the parasite and thus Other hosts that harbor the parasite and thus ensure continuity of the parasite's life cycle ensure continuity of the parasite's life cycle and act as additional sources of human and act as additional sources of human infection are known as infection are known as reservoirreservoir hosts. hosts.

An organism (usually an insect) that is An organism (usually an insect) that is responsible for transmitting the parasitic responsible for transmitting the parasitic infection is known as infection is known as the vectorthe vector..

Intestinal and luminal protozoa Intestinal and luminal protozoa significant to human health significant to human health

includeinclude  Entamoeba histolyticaEntamoeba histolytica (Amoebae) (Amoebae) Balantidium coliBalantidium coli (Ciliates) (Ciliates) Giardia lambliaGiardia lamblia and and Trichomonas Trichomonas

vaginalisvaginalis (Flagellates) (Flagellates) Cryptosporidium parvumCryptosporidium parvum and and

Isospora belliIsospora belli (Sporozoa) (Sporozoa)

Organism Transmission Symptoms Diagnosis Treatment

Entameba histolytica Oro-fecalDysentery with blood and necrotic tissue. Chronic: abscesses

Stool: cysts with 1-4 nuclei and/or trophs. Trophs in aspirate.

GI: Iodoquinol orMetronidazoleAbscess: Metronidazole

Giardia lamblia Oro-fecalFowl-smelling, bulky

diarrhea; blood or necrotic tissue rare.

Stool: typical old man giardia troph and/or

cyst.

Iodoquinol or Metronidazole.

Balantidium coli Oro-fecal; zoonotic

Dysentery with blood and necrotic tissue but no abscesses.

Stool: ciliated trophs and/or cysts.

Iodoquinol or Metronidazole.

Cryptosporidium parvum Oro-fecal Diarrhea Ooocysts in stool Paromycin

(investigational)

Isospora belli Oro-fecal Giardiasis-like Ooocysts in stool Sulpha drugs

Trichomonasvaginalis Sexual

Vaginitis; occasional urethritis/prostatitis.

Flagellate in vaginal (or urethral) smear.

Mebendazole; vingar douche; steroids

Entamoeba histolyticaEntamoeba histolytica

Causes disease of the large intestine Causes disease of the large intestine – amoebic dysentery – wherein – amoebic dysentery – wherein trophozoites feed on RBC causing trophozoites feed on RBC causing ulcers. Also the liver and lung ulcers. Also the liver and lung abscesses are possibleabscesses are possible

Naegleria – free-living amoeba in hot Naegleria – free-living amoeba in hot water sources. Causes primary water sources. Causes primary amoebic meningoencephalitis ( PAM)amoebic meningoencephalitis ( PAM)

Acanthamoeba – free living amoebasAcanthamoeba – free living amoebas

AMOEBIASIS (amoebic AMOEBIASIS (amoebic dysentery, amoebic hepatitis)dysentery, amoebic hepatitis)

Trophozoite: This form has an ameboid Trophozoite: This form has an ameboid appearance and  is usually 15-30 micrometers appearance and  is usually 15-30 micrometers in diameter, although more invasive strains in diameter, although more invasive strains tend to be larger. The organism has a single tend to be larger. The organism has a single nucleus with a distinctive small central nucleus with a distinctive small central karyosome. The fine granular endoplasm may karyosome. The fine granular endoplasm may contain ingested erythrocytes.  The nuclear contain ingested erythrocytes.  The nuclear chromatin is evenly distributed along the chromatin is evenly distributed along the periphery of the nucleus.periphery of the nucleus.

Cyst: Cyst: Entameba histolytica Entameba histolytica cysts are spherical, cysts are spherical, with a refractile wall; the cytoplasm contains with a refractile wall; the cytoplasm contains dark staining chromatoidal bodies  and 1 to 4 dark staining chromatoidal bodies  and 1 to 4 nuclei with a central karyosome and evenly nuclei with a central karyosome and evenly distributed peripheral chromatindistributed peripheral chromatin

FlagellatesFlagellatesGiardia lambliaGiardia lamblia

- a human parasite of the - a human parasite of the gastrointestinal tract. The gastrointestinal tract. The organism is spread by direct organism is spread by direct contact or through contact or through contaminated food and water. contaminated food and water.

GiardiaGiardia spp. are pear-shaped, spp. are pear-shaped, with hair-like flagella for with hair-like flagella for motility. motility.

They cause the disease They cause the disease giardiasis (or lambliasis), an giardiasis (or lambliasis), an infection of the small intestine infection of the small intestine most common in tropical most common in tropical areas. areas.

GiardiaGiardia spp. attaches by spp. attaches by means of sucking discs to means of sucking discs to microvilli in the human microvilli in the human intestine. Abdominal cramps, intestine. Abdominal cramps, swelling, diarrhea and nausea swelling, diarrhea and nausea may occur may occur

Balantidium coli Balantidium coli

This is a parasite primarily of This is a parasite primarily of cows, pigs and horses. The cows, pigs and horses. The organism is a large (100 x 60 organism is a large (100 x 60 micrometer) ciliate with a micrometer) ciliate with a macro-  and a micro-nucleus . macro-  and a micro-nucleus . The infection occurs mostly in The infection occurs mostly in farm workers and other rural farm workers and other rural dwellers by ingestion of cysts dwellers by ingestion of cysts in fecal material of farm in fecal material of farm animals. Man-to-man animals. Man-to-man transmission is rare but transmission is rare but possible. Metronidazole and possible. Metronidazole and iodoquinol are effective.iodoquinol are effective.

Trichomonas vaginalisTrichomonas vaginalis

Trophozoite with undulating Trophozoite with undulating membrane and polar flagellamembrane and polar flagella

Presents with fishy-smelling yellow Presents with fishy-smelling yellow discharge (guess where)discharge (guess where)

Males usually asymptomaticMales usually asymptomaticSexually transmittedSexually transmitted

Organism Transmission Symptoms Diagnosis Treatment

S. mansoni, S. japonicum

skin penetration by cercaria

Dermatitis, abdominal pain, bloody stool, peri-portal fibrosis, hepato-splenomegaly, ascites, CNS

Eggs in stool Praziquantel

Schistosoma hematobium

skin penetration by cercaria

Dermatitis, urogenital cystitis, urethritis and bladder carcinoma

Eggs in urine Praziquantel

Fasciolopsis buski

Metacercaria on water chestnut

Epigastric pain, nausea, diarrhea, edema, ascites

Eggs in stool Praziquantel,

C. sinensis,O. felinus, or O. viverini

Cysts in fish Inflammation and deformation of bile duct, hepatitis, anemia and edema

Eggs in stool Praziquantel

Paragonimus westermani

Cyst in crab meat

Cough (dry / rusty brown sputum), pulmonary pain, pleurisy, tuberculosis-like

Eggs in sputum Praziquantel

Trematodes ( Flukes )Trematodes ( Flukes )Schistosomes

Schistosoma japonicum, Schistosoma japonicum, mansonimansoni

Fasciolopsis buski ( Giant Fasciolopsis buski ( Giant intestinal fluke)intestinal fluke)

Paragonimus westermanii ( Lung Paragonimus westermanii ( Lung fluke )fluke )

Clonorchis sinensis ( Chinese Clonorchis sinensis ( Chinese liver fluke )liver fluke )

Echinococcus granulosus Echinococcus granulosus *(hydatid cyst)*(hydatid cyst)

Organism Transmission Disease/symptoms

Diagnosis Treatment

Trypanosoma brucei

Tsetse fly. Sleeping sickness; cardiac failure.

Hemoflagellate in blood or lymph node.

Blood stage: Suramin or petamidine isethionate;

T. cruzi Reduvid (kissing) bug.

Chagas disease: megacolon, cardiac failure.

Hemoflagellate in blood or tissue.

CNS: melarsoperolNifurtimox and Benzonidazole.

Leishmania donovani

Sand fly Visceral leish-maniasis, granulomatous skin lesions.

Intracellular (macrophages) leishmanial bodies.

Pentosam; Pentamidine isethionate.

L. tropica Sand fly. Cutaneous lesions.

As for L. donovani.

As for L. donovani.

L. braziliensis Sand fly Mucocutaneous lesions.

As for L. donovani.

As for L. donovani.

Trypanosoma – Trypanosoma – flagellate with Tsetse fly as vectorflagellate with Tsetse fly as vectorCauses African sleeping sicknessCauses African sleeping sickness

Trypanosoma cruzii – Trypanosoma cruzii – Chaga’s diseaseChaga’s diseasekissing bug as vectorkissing bug as vector

Leishmania –Leishmania –Sandfly as vectorsSandfly as vectorsVisceral, cutaneous & mucocutaneous lesionsVisceral, cutaneous & mucocutaneous lesions

Blood & Tissue ProtozoansBlood & Tissue Protozoans

Organism Transmission Disease/symptoms

Diagnosis Treatment

Plasmodium falciparum P. ovale, P. malariae and P. vivax

Female anopheline mosquito.

Malarial paroxysm: chills, fever, headache, nausea cycles.

Plasmodia in rbc, typical of the species involved.

Quinine derivatives ProguanilLariam

Babesia microti Tick Hemolytic anemia, Jaundice and fever

Typical organism (Maltese cross) in rbc.

None; self resolving.

Toxoplasma gondii

Oral from cat fecal material;or meat

Adult: flu like;congenital: abortion, neonatal blindness and neuropathies.

Intracellular (in macrophages) tachyzoites.

Sulphonamides, pyemethamine, possibly spiramycin (non-FDA).

Pneumocystis jiroveci Cough droplets Pneumonia Pneumocystis in

sputum.

Trimethoprim and sulphamethoxazole.

SporozoansSporozoansCryptosporidium parvum – found in Cryptosporidium parvum – found in

waters, a self limited diarrheawaters, a self limited diarrheaPlasmodium species cause malariaPlasmodium species cause malaria

Anopheles mosquito as vectorsAnopheles mosquito as vectorsComplicated life cycle.Complicated life cycle.P. vivax, P. ovale, P. malariae, P. falciparumP. vivax, P. ovale, P. malariae, P. falciparum

Toxoplasma gondii – reservoir in catsToxoplasma gondii – reservoir in catsHuman ingest cyst from cats feces or Human ingest cyst from cats feces or

undercooked meat. Danger in fetus undercooked meat. Danger in fetus developmentdevelopment

MalariaMalaria

Nematodes (Roundworms)Nematodes (Roundworms)

Organism Transmission Symptoms Diagnosis Treatment

Ascaris lumbricoides

Oro-fecalAbdominal pain, weight loss, distended abdomen

Stool: corticoid oval egg (40-70x35-50 μm) Mebendazole

Trichinella spiralis

Poorly cooked pork

Depends on worm location and burden: gastroenteritis; edema, muscle pain, spasm; eosinophilia, tachycardia, fever, chill headache, vertigo, delirium, coma, etc.

Medical history, eosinophilia, muscle biopsy, serology

corticosteroid and Mebendazole

Trichuris trichiura

Oro-fecalAbdominal pain, bloody diarrhea, prolapsed rectum

Stool: lemon-shaped egg (50-55 x 20-25μm)

Mebendazole

Enterobius vermicularis

Oro-fecalPeri-anal pruritus, rare abdominal pain, nausea vomiting

Stool: embryonated eggs (60x27 μm), flat on one side

Pyrental pamoate or Mebendazole

Trichinella spiralisTrichinella spiralis

Trichuris trichiuriaTrichuris trichiuria

Enterobius vermicularisEnterobius vermicularis

Strongyloides stercoralis Strongyloides stercoralis (threadworm)(threadworm)

Organism Transmission Symptoms Diagnosis Treatment

Strongyloides stercoralis

Soil-skin, autoinfection

Itching at infection site, rash due to larval migration, verminous pneumonia, mid-epigastric pain, nausea, vomiting, bloody dysentery, weight loss and anemia

Stool: rhabditiform larvae (250x 20-25μm)

Ivermectin or Thiabendazole

Necator americanes; Ancylostoma duodenale

Oro-fecal (egg); skin penetration (larvae)

Maculopapular erythema (ground itch), broncho-pneumonitis, epigastric pain, GI hemorrhage, anemia, edema

Stool: oval segmented eggs (60 x 30 20-25μm)

Mebendazole

Necator americanus Necator americanus (hookworm)(hookworm)

Dracunculus medinensis (Guinea Dracunculus medinensis (Guinea worm)worm)

Organism Transmission Symptoms Diagnosis Treatment

Dracunculus medinensis

Oral: cyclops in water

Blistering skin, irritation, inflammation

Physical examination Mebendazole

Wuchereria bancrofti; W. brugia malayi(elephantiasis)

Mosquito bite

Recurrent fever, lymph-adenitis, splenomegaly, lymphedema, elephantiasis

Medical history, physical examination, microfilaria in blood (night sample)

Mebendazole; Diethyl-carbamazine

Onchocerca volvulus

Black fly bite

Nodular and erythematous dermal lesions, eosinophilia, urticaria, blindness

Medical history, physical examination, microfilaria in nodular aspirate

Mebendazole; Diethyl-carbamazine

Loa loa Deer fly As in onchocerciasis

As in onchocerciasis As above

Toxocara canis & catii ( visceral Toxocara canis & catii ( visceral larval migrans)larval migrans)

Ancylostoma braziliensis Ancylostoma braziliensis ( cutaneous larva migrans, ( cutaneous larva migrans,

creeping eruption)creeping eruption)

Organism Transmission Symptoms Diagnosis Treatment

Tenia saginata Cyst in beefEpigastric pain, vomiting, diarrhea

Proglottids or eggs in stool or perianal area

Praziquantel

Tenia solium Cyst in porkEpigastric pain, vomiting, diarrhea

Proglottids or eggs in stool or perianal area

Praziquantel

T. solium Cysticercosis

Oro-fecal

Muscle pain and weakness, ocular and neurologic problems

Roentgenography, anti-cysticercal antibody (EIA)

Praziquantel

Cestodes- (Tapesworms)Cestodes- (Tapesworms)

Taenia soliumTaenia solium

Diphylobotrium latumDiphylobotrium latum

Organism Transmission Symptoms Diagnosis Treatment

D. latum Cyst in fish

Abdominal pain, loss of weight, anorexia, malnutrition and B12 deficiency problems

Proglottids or eggs in stool or perianal area

Praziquantel

E. granulosus Oro-fecal

Large cysts produce various symptoms depending on the location of the organism.

Roentgenography, anti-hydatid fluid antibody (EIA), Casoni skin test

Surgery, formalin injection and drainage, Praziquantel

E. multiloculoris Oro-fecal As above As aboveSurgery, Albendazole

Hymenolepsis nana ( dwarf Hymenolepsis nana ( dwarf tapeworm)tapeworm)