WEEK 4: PROTOZOAL DISEASES Flashcards
Define the following terms:
*Parasite
*Infection
*Infestation
*Definitive host
*Intermediate host
Parasite: An organism that spends a significant portion of its life in or on the living tissue of a host organism and causes harm to the host without immediately killing it.
Infection: invasion of endoparasites
Infestation: external parasitism of ectoparasites such as arthropods.
Definitive host: harbors the adult or sexual stage.
Intermediate host: part or all of the larval or asexual stage takes place
What are protozoa?
State physical characteristics of protozoa.
Means “first animal “.
They are esimplestandprimitiveof all animals.
- Unicellular eukaryotes:
*Lack cell wall,
*Contain membrane-bound organelles, including one or more nucleus. - Size ranges from 10–50um, some up to 1 mm, seen under a microscope.
- Body protoplasm is differentiated into an outerectoplasmand innerendoplasm.
- Locomotor organs are fingers likepseudopodia, whip-likeflagella, hair-likeciliaor none.
- Respiration occurs bydiffusionthrough the general body surface.
Protozoans exhibit mainly two forms of life.
State them.
Free-living(aquatic, freshwater, seawater)
Parasitic(ectoparasites or endoparasites)
List 3 ways in which protozoa obtain food.
How does excretion occur in protozoa?
What is encystment?
Why do protozoa do that?
Food obtained by:
*Absorption through the ectoplasm–diffusion /active transport
*Surround food and engulf it (phagocytosis)
openings or “cytostomes” into which they sweep food.
* Digest food intracellularly in stomach-like compartments - vacuoles
Excretion occurs through thegeneral body surface temporary opening in the ectoplasm or through a permanent pore call-CYTOPYGE.
Usually exists in the trophozoite or cystic stage.
Encystment- A process which goes on in protozoans, by which, the pseudopodia or other prolongations of the body being withdrawn, the animal assumes a spherical shape, and becomes coated with a comparatively tough resisting layer, which thus forms a cyst.
*To resist unfavorable conditions of food, temperature, moisture.
*Helps in dispersal.
*Non-feeding
*Non-motile
*Non-growing
What organism is described above?
Cyst
Protozoa reproduce asexually or sexually.
Describe the 2 ways of asexual reproduction.
Asexual reproduction by:
*Binary fission
*Schizogony
BINARY FISSION
-Nucleus divides into 2 parts
-Portions of cytoplasm then concentrate around each nucleus.
-Cell separates into 2 daughter cells.
SCHIZOGONY: multiple fission
-Nucleus undergoes multiple divisions
-Portions of cytoplasm then concentrate around each nucleus.
-Cell separates into multiple daughter cells.
State the sexual reproduction method of protozoa.
Sexual reproduction: Sporogony
Plasmodium
The life cycle is often complicated with alternation of asexual and sexual phases (alternation of generation).
Name the phylum in which plasmodium is found.
Phylum Apicomplexa
Give examples of the range of conditions resulting from protozoal infections, and the main types of organism responsible.
*Intestinal tract
*Urogenital tract
*Blood and tissue
- Entamoeba histolytica- Amoebiasis
Cryptosporidium spp.- Cryptosporidiosis
Cystoisospora belli- Isosporiasis
Cyclospora cayetanensis- Cyclosporiasis
Microsporidia- Microsporidiosis
Giardia intestinalis- Giardiasis
Balantidium coli- Balantidiasis - Trichomonas vaginalis- Trichomoniasis
3.
State 4 main types of protozoa that are the leading cause of death.
-Malaria
-Amoeba
-Toxoplasma
-Trypanosoma
Describe Entamoeba histolytica.
It exists in 2 forms. State them.
A pseudopod-forming nonflagellate amoebic protozoa
Move by means of flowing cytoplasm with the production of pseudopodia
Humans are the only host
Found in human colon
Exists in two forms-
*Cysts (formed stool) –infective form
*Trophozoites (diarrheal stools)
Both forms are passed in feces.
Cysts ingested from faecally contaminated food or water.
Sexual transmission through oral–anal sexual practices
State the Intestinal Amebiasis and its complications.
State Extraintestinal Amebiasis and its complications.
Asymptomatic Colonization
E. histolytica, E. dispar
Intestinal Amebiasis and Its Complications
-Amebic dysentery/ acute necrotizing colitis
-Ameboma
-Toxic megacolon
-Peritonitis
-Cutaneous amebiasis
-Rectovaginal fistulas
Extraintestinal Amebiasis
-Amebic liver abscess (hepatitis)
-Splenic abscess, Brain abscess, Empyema
-Pericarditis
State the lab diagnosis methods for Entamoeba Infection.
Lab diagnosis:
1.Microscopy
2.Antigen detection
3.Serologic tests
4.PCR
5.CT for abscess and granulomas
6.Colonoscopy
Treatment
*Luminal infection: iodoquinol, paromomycin, and diloxanide furoate
*Invasive amebiasis (colitis, liver abscess) *nitroimidazole -metronidazole and tinidazole
Describe the following free-living amoeba.
1. Acanthamoeba culbertsoni
2. Naegleria fowleri
3.Balamuthia mandrillaris
Acanthamoeba culbertsoni
Contaminated water
Keratitis, Uveitis in contact lens users.
Skin lesions – ulcers, hard nodules.
Granulomatous dissemination- lungs
Granulomatous necrotizing encephalitis.
Naegleria fowleri: Brain eating amoeba
Primary Amoebic Meningoencephalitis.
Fresh water
Balamuthia mandrillaris
Granulomatous amoebic encephalitis
From dust, soil
Transmission by inhalation, ingestion or skin injury
Give characteristics of Cryptosporidium.
Cryptosporidium parvum and Cryptosporidium hominis causes diarrheal disease - cryptosporidiosis.
Cryptosporidium oocysts in 87% of the raw water samples
Domesticated animals and birds - primary reservoir
AIDS patients and children excrete millions of oocysts a day, survive for months in sewage.
Spread by direct person-to-person contact.
The median infectious dose in healthy adult volunteers is 132 oocysts
Oocysts highly resistant to chlorination.
The hallmark of cryptosporidial infection is voluminous
watery diarrhea, explosive and foul smelling with abdominal cramps, fatigue, and anorexia.
Outline the diagnosis and treatment of cryptosporidium.
Diagnosis:
Stool Microscopy :Acid-fast staining
Direct fluorescent antibody [DFA]
Enzyme immunoassays for detection of Cryptosporidium sp. antigens.
Molecular methods (e.g., PCR)
Treatment
*Self-limiting
*Oral rehydration therapy
*Nitazoxanide: It works by interfering with the energy metabolism and other essential processes of these parasites, leading to their death.
*Cryptosporidiosis often not curable and symptoms return if the immune status worsens.
The infectious form - Cysts
Trophozoites and cyst forms on surfaces or in soil, food or water contaminated with feces.
Method of transmission: Water (drinking/recreational water) travelers, person-to-person (daycare centers), oral anal intercourse
Diarrhea with flatulence, Foul smelling, frothy, Greasy stools that tend to float, abdominal cramps nausea/vomiting, dehydration.
In children, delays physical and mental growth, slows development, and cause weight loss and malnutrition - failure to absorb fat, lactose, vitamin A and vitamin B12.
Treatment - Metronidazole, Tinidazole, and Nitazoxanide
Name the above-described flagellated intestinal protozoan and disease it causes.
Giardia (Giardia lambli or Giardia duodenalis)
Flagellated intestinal protozoan-diarrheal illness giardiasis.
A very common sexually transmitted disease
A flagellate protozoan parasite –no cystic form
70% of infected people do not have any signs or symptoms.
Complain of itching, burning, redness or soreness of the genitals, discomfort with urination, a frothy, yellowish, or greenish discharge with an offensive smell
Microscopy: Wet film preparation with KOH
Treatment a single dose of either
Metronidazole or Tinidazole
Name the protozoa described above.
Trichomonas vaginalis- Trichomoniasis
Live in blood and tissues of human and in gut of insect vectors
Require two hosts to complete lifecycle
Family- Trypanosomatidae
Genus –Trypanosoma and Leishmania
Exist in 2 or more of the 4 morphological stages:
Amastigote, Promastigote, Epimastigote, Trypomastigote
Trypanosoma brucei subspecies - African sleeping sickness
Trypanosoma brucei rhodesiense (East African sleeping sickness- eastern and southeastern Africa)
Trypanosoma brucei gambiense (West African sleeping sickness- central Africa and in West Africa)
Transmitted by the tsetse fly (Glossina species)
What is described above?
HEMOFLAGELLATES
T. b. rhodesiense infection (East African sleeping sickness)
Progresses rapidly
A large sore (chancre) at the site of the tsetse bite.
Fever, headache, muscle and joint aches, enlarged lymph nodes, HSM within 1-2 weeks of the infective bite.
After a few weeks, the parasite invades the central nervous system, causes mental deterioration and coma.
Death ensues within months.
Treatment: Pentamidine, Suramin, Melarsoprol
T. b. gambiense infection (West African sleeping sickness)
Progresses slowly
Itching of the skin, swollen lymph nodes, weight loss
Intermittent fevers, headaches, muscle and joint aches, and malaise.
After 1-2 years, evidence of central nervous system involvement, with personality changes, daytime sleepiness with nighttime sleep disturbance and progressive confusion.
Partial paralysis or problems with balance or walking may occur and hormonal imbalances noticed.
Untreated infection lasts 6-7 years, often kills in about 3 years.
What is described above?
African Trypanosomiasis
Trypanosoma cruzi transmitted by reduviid (“kissing”) bug
Chancres (“chagomas”) develop at the site of infection, with transient febrile illness, rarely lead to death by heart failure.
Extremely slow and chronic course.
The parasite invades host cells, macrophages and cardiac muscle cells.
The major cause of death is myocarditis, progressive weakening and dilation of the ventricles
Cardiac aneurysm and heart block are particularly serious features.
Dilatation of the intestinal tract -megaesophagus and megacolon are the two commonest manifestations.
What is described above?
South American Trypanosomiasis(Chagas disease)
Obligate intracellular flagellate protozoa
Transmitted by sandflies
Visceral leishmaniasis- Leishmania donovani
Cutaneous/mucocutaneous leishmaniasis –
Leishmania tropica,mexicana, and braziliensis,
Painless small nodules – large ulcers, or plaque
Heal with scarring.
Immune to reinfection
What is described above?
Leishmania- Leishmaniasis
Largest protozoan parasite of humans
Zoonosis: Principal reservoir –pig, monkey, rat
Trophozoite and cyst form
Habitat- Large intestine
Contaminated food and water
Diarrhea, dysentery, abdominal colic, tenesmus nausea, vomiting, mucosal ulcers, abscesses, perforation
Diagnosis: Microscopy
Treatment: Tetracycline, Metronidazole
What is described above?
Phylum Ciliophora (ciliate) Balantidium coli- Balantidiasis
Phylum Apicomplexa, coccidian parasite-apical polar complex
22.5% of the population 12 years and older have been infected with Toxoplasma.
Severe manifestation in immunosuppressed-HIV+
Not passed from person-to-person
Definitive hosts - members of family Felidae (domestic cats and their relatives)
Exists in three forms:
Trophozoite (tachyzoites)- acute phase-intracellularly in tissues, organs
Tissue cyst (bradyzoites)–chronic phase-brain, muscles
Oocyst (sporozoites)- definitive host
Congenital /Acquired Toxoplasmosis
What is described above?
Toxoplasma gondii-Toxoplasmosis
Phylum- Apicomplexa
Tick-borne malaria like illness - zoonosis
Babesia microti are obligate intraerythrocytic in vertebrates
Sporozoites replicate by budding
Do not produce hemozoin.
Definitive host -Ixodes tick also the vector
Hemolytic anemia, fever, jaundice, weakness, hepatosplenomegaly
Microscopy of blood smear:
intra erythrocyte sporozoites
Treatment: Quinine with Clindamycin
What is described above?
Babesia microti- Babesiosis
