This document summarizes various unicellular and multicellular parasites that can infect humans. It discusses the life cycles, transmission, clinical presentations, and treatments of intestinal protozoa like Entamoeba histolytica, Giardia lamblia, and Cryptosporidium parvum. It also covers trematodes, cestodes, and nematodes including Ascaris lumbricoides, Strongyloides stercoralis, and hookworms. Major topics include the clinical effects of these parasites, methods of diagnosis, and recommended drug treatments.
3. Entamoeba histolytica Amoebiasis
World wide distribution – 3rd after malaria and
schistosomiasis
Hand-mouth; fecal-oral; sexual transmission
Increasing in homosexuals
Resistant to chlorine
Major complications: amoebic abscesses in
liver, brain, lung
Amoebic pericarditis (rare) is most dangerous
complication of amoebic liver abscess
8. Life Cycle of Giardia
Ingestion of cysts trophozoites attach to duodenal
brush border causing irritation and obstruction of
absorption cysts in colon; passed in feces
See them moving in stool
9. Clinical Presentation of Giardia
Watery diarrhea, abdominal cramps
Weight loss
No blood, no pus, no fever
Steatorrhea – fatty and foul-smelling
Lactose intolerance
Antibody deficiency
Dx: fecal cysts/trophozoites; enterotest; ELISA;
duodenal aspiration
10. Comparison of Clinical
Presentations
Amoebiasis
Giardiasis
Asymptomatic
Non-inflammatory watery
Mild GI discomfort
Inflammatory
Diarrhea, pain, blood, mucu
s
Weight loss, fever
Organ specific symptoms
Dx:
history, cysts/trophozoites, E
LISA/PCR
History: international travel
diarrhea, abdominal cramps
Steatorrhea – fatty and foulsmelling
No blood, no pus, no fever
Weight loss
Lactose intolerance
Antibody deficiency
Dx: fecal cysts/trophozoites;
enterotest; ELISA; duodenal
aspiration
History: Camping in Northern US
wilderness; drink mountain water
12. Intestinal Ciliate
Balantidum coli – Balantidiasis
The only ciliated protozoa!
Common parasite of animals
No extraintestinal spread
Easily treated, not very common
Seen in ppl who are around animals all the time
Farmers, zoo workers
Tx: tetracycline
13. Intestinal Sporozoa
Isospora belli
Cyclospora cayetanesis water or produce
Cryptosporidium parvum/hominis water and food
Non-inflammatory diarrhea
Infection by ingestion of oocyst infection of
intestinal epithelium
Sexual & asexual stages – sporogony/schizogony
Self-limiting in immunocompetent; Severe in AIDS or
other immunocompromised individuals
Dx: acid-fast oocysts in stool & history
20. Leishmaniasis sand fly
Vector – Phlebotomine
3 forms
Leishmania tropica: dermal/cutaneous form
Leishmania brasiliensis: mucocutaneous form
Leishmania donovanii: visceral form
Most severe form (KALA AZAR) – 100% fatality if untreated
Hypoalbuminemia; hypergammaglobulinemia
Irregular fever, marked weight
loss, anemia, hepatosplenomegaly
Amastigotes in deep tissue – liver, spleen, bone marrow
Drug: Sodium stibogluconate
21. Visceral leishmaniasis
Patho: Parasite localization in macro of RES
PANCYTOPENIA high output heart failure
myocarditis/pericarditis
Leishmania – HIV coinfection on the rise
22. Tissue Sporozoa
Plasmodium (blood & tissue)
Malaria; Vector: female anopheles mosquito
Babesia (blood)
Babesiosis; Vector: Ixodes scapularis
Ixodes also carries lyme disease and human granulocytic
anaplasmosis
Toxoplasma gondii (tissue)
Toxoplasmosis; Vector: cat
Most commonly reported parasitic disease following heart
transplantation
Two life cycles, two hosts: sexual (sporogony) – definitive
host; Asexual (schizogony) – intermediate host
29. Malaria hypnozoites
P. vivax & P. Ovale
Use primaquin against hypnozoites
Chloroquine against severe malaria
Quinine in severe parasitemia and resistant malaria
Metronidazole for amoebic liver abscesses
Also for giardiasis, trichomoniasis, dracunculis
medinensis
35. Clinical Classification
Lung fluke
Paragonimus westermanii CRAB
Liver fluke
Clonorchis sinensis FISH
Fasciola hepatica PLANT/VEGETABLE
Intestinal fluke
Heterophyes heterophyes FISH
Fasciolopsis buski PLANT/VEGETBALE
Tx: Praziquantel for all trematodes
36. Schistosomiasis (blood fluke)
Direct skin penetration by cecariae
S. Mansoni – intestinal (side spine)
S. Japonicum – intestinal (no spine)
S. Hematobium – urinary (terminal spine)
Tx: Praziquantel
Picture:
Left, S. mansoni
Middle, S. Haematobium
Right, S. japonicum
37. Diphylobothrium Latum
Broad or fish tapeworm
Very big
From ingestion of larvae in RAW fish
Clinical:
Low serum B12, eosinophilia
Atrophic gastritis
Megaloblastic anemia
Dx: history, presentation, eggs in stool
Tx: Praziquantel, Niclosamide
38. Taeniasis
Beef tapeworm – T. Saginata
Ingestion of larvae in undercooked/raw beef
Pork tapeworm – T. Solium
Ingestion of eggs in undercooked/raw pork
Associated w/ heart problems
Dx – eggs/proglottids in human feces; adult in
intestines
Tx: Praziquantel, Niclosamide
39. Nemathelminthes
Intestinal nematodes
Ascaris lumbricoides – Roundworm
Strongyloides stercoralis – Threadworm
Ancylostoma duodenale – Hookworm
Necator americanus – Hookworm
Enterobius vermicularis – Pinworm
Trichuris trichiura – Whipworm
Trichinella spiralis – Porkworm
Infections characterized by eosinophilia and high IgE
levels; hygiene and lifestyle is important
40. Ascaris lumbricoides - Roundworm
One of the most common human infections worldwide
Patho:
Stage 1: “infective” eggs ingested larval migration
cough, hemoptysis (bloody sputum), dyspnea, hemorrhagic
pneumonia, asthma attacks, pulmonary infiltration, urticaria
Stage 2: adult in intestine dependent on worm load
pain, distension, nausea, anorexia, malnutrition (growth
stunting in children), intestinal obstruction
Stage 3: adult migration acute pancreatitis or obstruction,
biliary obstruction, jaundice, appendicitis, peritonitis
Dx: larvae in sputum; ova & parasites in stool
Tx: Mebendazole
41. Strongyloides stercoralis Threadworm
Direct skin penetration
2 distinct adult forms
Filariform (infective form): larvae penetrate intact skin
initiating infection enter circulatory system lungs
penetrate alveolar spaces reach small intestine
mature to adult female (not male) produce
uninfective larvae autoinfection
Uninfective infective in intestine and stool
Uninfective adults in soil or become infective
Rhabditiform (uninfective form)
43. Enterobius Vermicularis - Pinworm
Common in US; children
Eggs on perianal folds perianal itching
Pricking anal pain, restlessness, sleeplessness
Dx: see them around anus, eggs on scotch tape
Tx: pyrantel pamoate or mebendazole
Enterobius vermicularis
44. Necator Americanus &
Ancylostoma Duodenale –
Hookworms
Worldwide distribution; Enter thru FEET
Clinical stages:
Cutaneous Stage: ground itch
Pulmonary Stage: pulmonary hemorrhage
Cough, wheezing, pneumonitis
Intestinal Stage: GI discomfort, blood loss
45. Hookworm Infection Complications
Protein losing enteropathy
Fe deficiency anemia
Tachycardia
Stillbirth
Poor physical development
Dx: history and eggs in stool
Tx: mebendazole + dietary supplements
Wear shoes!!
47. Trichinella Spiralis - Porkworm
No eggs
No external phase
Dead end transmission! – ingestion of undercooked
meat larvae turn to adults in intestinal cells
migrate to muscle encyst
48. Clinical Presentation of Trichinella
Spiralis
Diarrhea, constipation
Fever, myalgia, fatigue
Macular or petechial rash
Periorbital edema, conjunctivitis/retinal
hemmorrhage
Splinter hemmorhage; heart problems
Dx: muscle biopsy, positive serology, presentation
symptoms
Tx: Thiabendazole – before tissue invasion
Rest + analgesics for after invasion
49. Tissue Nematodes = Filaria
Adults in tissue
Eggs not produced; microfilaria produced
Wuchereria bancrofti – mosquito
Brugia malayi/timori – mosquito
Loa loa – deer fly
Onchocerca volvulus – simulium black fly
Dracunculus medinensis – Cyclops (water flea)
50. Elephantiasis/Lymphatic filariasis
Wuchereria bancrofti
Brugia malayi & Brugia timori
Patho: microfilaria adult worms in lymphatics
more microfilariae lymphoedema inflammatory
reaction elephantiasis
Early: acute inflammation, hypereosinophilia, massive
lymphatic dilatation, bacterial and fungal infections,
infection by wolbachia bacteria (tx: tetracycline)
Late: lymphoedema/elephantiasis; chyluria (lymph in
urine)
Tx: DEC + Albendazole or Albendazole + Ivermectin
51. Elephantiasis
Dx: presentation, very high increase in eosinophils, IgE, IgG4, and
specific antifilarial Ab; microfilariae in blood (nocturnal periodicity)
Sheath = pathogenic; no sheath = nonpathogenic
52. Onchocerca Volvulus
River blindness/onchocerciasis
Vector: Simulium Black Fly
Larvae in subcutaneous tissue
Patho: adult in onchocercoma millions of migrating
microfilariae death due to immune response
onchodermatitis/keratitis
Dx: Skin biopsy nodules tons of little worms
Tx: DEC or Ivermection (single dose)
53.
54. Dracunculiasis
Dog, horse, cow, monkey
Vector: Cyclops (Water Flea)
Debilitatin skin eruptions worms come out of
them!!
Tx: metronidazole/thiabendazole
Dracunculus medinensis
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