ParasitologySporozoons

Parasitology/Sporozoons (3 hours)

• 1. Defines “Sporozoon’’• 1.1 Lists the sporozoon classification.• 1.2. Defines the cell structure of sporozoons.• 1.3. Defines the life cyles of sporozoons; lists the cysts, trophozoits,

oocysts, promastigot, amastigot structures.

• 2. Lists the clinical tables related with sporozoons and defines pathogenetic mechanisms.

• 2.1. Defines the clinical importance of sporozoons.• 2.2. Defines the sample taking related with infections of sporozoons.• 2.3. Lists the laboratory diagnostic methods.

Flagellates

Intestinal flagellates Giardia intestinalis Trichomonas spp Dientamoeba fragilis

Trichomonas vaginalis

Hemoflagellates Leishmania donovani Trypanosoma cruzi

Giardia intestinalis (lamblia)

Cysts are resistant forms and are responsible for transmission of giardiasis. 

Both cysts and trophozoites can be found in the feces (diagnostic stages)

The cysts are hardy and can survive several months in cold water. 

Infection occurs by the ingestion of cysts in contaminated water, food, or by the fecal-oral route (hands or fomites)

Because the cysts are infectious when passed in the stool or shortly afterward, person-to-person transmission is possible

Symptoms

diarrhea, abdominal pain, bloating, nausea, vomiting. incubation period: 1 to 14 days (average of 7 days)

Diagnosis

cysts or trophozoites in the feces, using direct mounts(repeated samplings)

samples of duodenal fluid (e.g., Enterotest)

duodenal biopsy may demonstrate trophozoites

alternate methods antigen detection tests enzyme immunoassays, detection of parasites by immunofluorescence. 

Trichomonas vaginalis

resides in the female lower genital tract and the male urethra and prostate

transmitted among humans, its only known host, primarily by sexual intercourse

no cyst formation

Symptoms

vaginitis with a purulent discharge is the prominent symptom, vulvar and cervical lesions, abdominal pain, dysuria dyspareunia.  In men asymptomatic; urethritis, epididymitis, prostatitis the incubation period is 5 to 28 days.

Diagnosis

microscopic examination of wet mounts culture

Dientomoeba fragilis

not an ameba but a flagellate no cyst formation

Symptoms

diarrhea, abdominal pain, anorexia, nausea, vomiting, fatigue, weight loss.

Diagnosis detection of trophozoites in permanently stained fecal

smears (e.g., trichrome).  not detectable by stool concentration methods.  trophozoites can be easily overlooked ,they are pale-

staining and their nuclei may resemble those of Endolimax nana or Entamoeba hartmanni.

Leishmania donovani

a vector-borne disease transmitted by sandflies caused by obligate intracellular protozoa of the genus

Leishmania

Promastigotes amastigotes in the sandfly's midgut, the parasites differentiate into

promastigotes in MexicoCentral America, South Americasouthern Europe Asia (not Southeast Asia),the Middle East, and Africa  

Symptoms

Cutaneous leishmaniasis (L.tropica) one or more sores on their skin.  the sores can change in size and appearance over time.  they often end up looking somewhat like a volcano, with a

raised edge and central crater.  a scab covers some sores. 

the sores can be painless or painful.  some people have swollen glands near the sores (for

example, in the armpit if the sores are on the arm or hand).

Symptoms

Visceral leishmaniasis (kala-azar)(L.donovani)

fever, weight loss, enlarged spleen and liver (usually the spleen is bigger

than the liver).  Some patients have swollen glands.  Certain blood tests are abnormal.  low blood counts,

including a low red blood cell count (anemia), low white blood cell count, and low platelet count. 

Some patients develop post kala-azar dermal leishmaniasis.

Visceral leishmaniasis is becoming an important opportunistic infection in areas where it coexists with HIV. 

Diagnosis Giemsa-stained slides culture (using for example the diphasic NNN medium) Antibody detection

Trypanosoma cruzi Chagas disease, a zoonotic disease transmitted to humans by blood-sucking triatomine bugs  (kissing bug)

Chronic Chagas disease is a major health problem in many Latin American countries

trypomastigotes amastigotes trypomastigotes amastigotes Trypanosoma cruzi can also be transmitted throughblood transfusions, organ transplantation, transplacentally, in laboratory accidents.

Symptoms fever, anorexia, lymphadenopathy, mild hepatosplenomegaly, myocarditis.  Chronic stage may not occur for years or even decades after

initialinfection.  cardiomyopathy (the most serious manifestation); megaesophagus megacolon; weight loss. Chronic Chagas disease and its complications can be fatal.

DiagnosisMicroscopic examination: of fresh anticoagulated blood, or its buffy coat, for motile

parasites; of thin and thick blood smears stained with Giemsa, for

visualization of parasites.

Isolation of the agent by: inoculation into mice; culture in specialized media (e.g. NNN, LIT); xenodiagnosis, where uninfected reduviid bugs are fed on

the patient's blood, and their gut contents examined for parasites 4 weeks later.

Treatment benznidazole or nifurtimox In the chronic stage, e.g., pacemaker for heart block

Trypanosoma brucei T. b. gambiense -West African sleeping sickness T. b. rhodesiense - East African sleeping sickness. T. b. brucei - under normal conditions does not infect

humans

tsetse fly (genus Glossina)

Symptoms a trypanosomal chancre can develop on the site of

inoculation. a hemolymphatic stage (fever, lymphadenopathy, and

pruritus.) the meningoencephalitic stage ( headaches,

somnolence, abnormal behavior, loss of consciousness and coma)

the course of infection is much more acute with T. b. rhodesiense than T. b. gambiense.

Diagnosis microscopic examination of chancre fluid, lymph node

aspirates, blood, bone marrow, or, in the late stages of infection, cerebrospinal fluid. 

a wet preparation should be examined for the motile trypanosomes, and in addition a smear should be fixed, stained with Giemsa (or Field), and examined. 

the Card Agglutination Trypanosomiasis Test (CATT) test is of value for epidemiologic surveys or screening of T. b. gambiense

Amebas

Intestinal amebas Entamoeba histolytica Entamoeba coli Balantidium coli

Free-living amebas Naegleria fowleri Acanthamoeba castellani

Amebiasis

Entemoeba histolytica Entemoeba coli Entemoeba hartmanni

Symptoms asymptomatic infection ("luminal amebiasis"), invasive intestinal amebiasis

dysentery, colitis, appendicitis, toxic megacolon, amebomas,

invasive extraintestinal amebiasis liver abscess, peritonitis, pleuropulmonary abscess, cutaneous genital amebic lesions

Diagnosis Fresh stool: wet mounts and permanently stained

preparations (e.g., trichrome). Concentrates from fresh stool: wet mounts, with or

without iodine stain, and permanently stained preparations (e.g., trichrome).  Concentration procedures, however, are not useful for demonstrating trophozoites.

E. histolytica trophozoites can also be identified in aspirates or biopsy samples obtained during colonoscopy or surgery

Erythrophagocytosis is the only morphologic characteristic that can be used to differentiate E. histolytica from the nonpathogenic E. dispar

E.histolytica trophozoites

E.histolytica cysts

E.coli trophozoites

E.coli cysts

E.hartmanni

Balantidum coli a large ciliated protozoan parasite Most cases are asymptomatic. Clinical manifestations

persistent diarrhea, occasionally dysentery, abdominal pain, weight loss. 

Diagnosis trophozoites in stool specimens or in tissue collected

during endoscopy.  Cysts are less frequently encountered. 

Balantidium coli trophozoites their large size (40 µm to more than 70 µm). the presence of cilia on the cell surface, a bean shaped macronucleus which is often visible, a smaller, less conspicuous micronucleus.

Naegleria fowleri - Acanthomoeba spp

commonly found in lakes, swimming pools, tap water, and heating and air conditioning units.

only one species of Naegleria is known to infect humans, several species of Acanthamoeba are implicated

Symptoms Acute primary amebic meningoencephalitis (PAM) -

Naegleria fowleri.  severe headache and other meningeal signs, fever,

vomiting, and focal neurologic deficits, and progresses rapidly (<10 days) and frequently to coma and death.

Acanthamoeba spp. - subacute or chronic granulomatous amebic encephalitis (GAE), with a clinical picture of headaches, altered mental status, and focal neurologic deficit, which progresses over several weeks to death. 

granulomatous skin lesions more seriously, keratitis and corneal ulcers following

corneal trauma or in association with contact lenses.

DiagnosisNaegleria infections CSF a wet mount may detect motile trophozoites, Giemsa-stained smear trophozoites Acanthamoeba infections, biopsy specimens (brain tissue, skin, cornea) or of

corneal scrapings, which may detect trophozoites and cysts. 

cultivation direct immunofluorescent antibody

N.fowleri Acanthomoeba spp.

Treatment Eye and skin infections caused by Acanthamoeba spp.

are generally treatable.  Topical use of 0.1% propamidine isethionate (Brolene) plus neomycin-polymyxin B-gramicidin ophthalmic solution

keratoplasty is often necessary in severe infections Amphotericin B has been successfully used to treat PAM

caused by Naegleria fowleri

Sporozoans

Blood sporozoans Plasmodium vivax Plasmodium malariae Plasmodium ovale Plasmodium falciparum Babesia microti Other Isospora belli Sarcocystis bovihumanis Cryptosporidium parvum Toxoplasma gondii

Plasmodium spp.

Plasmodium vivax Plasmodium malariae Plasmodium ovale Plasmodium falciparum

A single species, P. reichenowi, which infects chimpanzees, is known to be a close sister lineage of P. falciparum.

This new species has been isolated in two chimpanzees (Pan troglodytes) kept as pets by villagers in Gabon (Africa).

The risk of transfer and emergence of this new species in humans must be now seriously considered given that it was found in two chimpanzees living in contact with humans and its close relatedness to the most virulent agent of malaria.

The malaria parasite life cycle involves two hosts.  a malaria-infected female Anopheles mosquito - sporozoites - the

human host sporozoites infect liver cells - into schizonts , which rupture and release merozoites . 

P. vivax and P. ovale a dormant stage [hypnozoites] can persist in the liver and cause relapses by invading the bloodstream weeks, or even years later.

initial replication in the liver (exo-erythrocytic schizogony )-asexual multiplication in the erythrocytes (erythrocytic schizogony ). 

merozoites infect red blood cells . the ring stage trophozoites mature into schizonts, which rupture

releasing merozoites .  some parasites - into sexual erythrocytic stages (gametocytes) . 

male (microgametocytes) and female (macrogametocytes), are ingested by an Anopheles mosquito during a blood meal . 

parasites’ multiplication in the mosquito - the sporogonic cycle .

in the mosquito's stomach, the microgametes penetrate the macrogametes generating zygotes  

the zygotes in turn become motile and elongated (ookinetes) which invade the midgut wall of the mosquito where they develop into oocysts .

the oocysts grow, rupture, and release sporozoites , which make their way to the mosquito's salivary glands. 

Inoculation of the sporozoites into a new human host perpetuates the malaria life cycle . 

SymptomsThe most frequent symptoms fever chills, headache, myalgias, arthralgias, weakness, vomiting, diarrhea. 

Other clinical features splenomegaly, anemia, thrombocytopenia, hypoglycemia, pulmonary or renal dysfunction, neurologic changes. 

P. falciparum (cerebral malaria), acute renal failure, severe anemia, adult respiratory distress syndrome. 

P. vivax - splenomegaly (with, rarely, splenic rupture), P. malariae -nephrotic syndrome. 

Ring: early developmental stage of the asexual erythrocytic parasite; Trophozoite: next developmental stage of the asexual erythrocytic

parasite; it has lost its "ring" appearance, and has begun to accumulate pigment

Schizont: late developmental stage of the asexual erythrocytic parasite; it has begun its division into merozoites, and thus is characterized by the presence of multiple contiguous chromatin dots

Gametocyte: sexual erythrocytic stage.

Ring with double chromatin dot

Schüffner's dots

Gametocytes of P. vivax Schüffner's dots

Mature schizonts. Ruptured schizonts

Large, amoeboid trophozoites of P. vivax

P. ovale rings

Gametocytes

Schizonts of P. ovale

Trophozoites of P. ovale

Ring forms

Gametocytes

Schizonts of P. malariae

Mature trophozoites

band forms  and "basket" form

Gametocytes

Immature schizont in a thin blood smear.Mature schizont.

trophozoites

TreatmentQuinine ( in chloroquine resistant P.falciparum)

Quinidine (IV form of quinine)

Chloroquine (acute attack) (prophylaxis)

Mefloquine (prophylaxis in chloroquine resistant cases)

Prymethamine-sulfadoxine (in chloroquine resistant P.falciparum)

Artemisinine (Qinghaosu) ( in chloroquine resistant P.falciparum)

Tetracycline and doxycycline

Halofantrine

Chloroguanide

Primaquine (eliminates exo erythrocytic forms in the liver)

Prophylaxis

Chloroquine 500 mgr per week starting 1-2 wks before travel, during travel and 4 wks post travel. Chloroquine resistant P.falciparum mefloquine 250 mgr.per week, 1week before,during travel and 4 wks post travel. Don’t use mefloquine during pregnancy.

Treatment

Chloroquine 1gr po,0.5 gr in 6 hrs, then 0.5gr.daily x 2d.Primaquine 26.3 mgr.po daily x14d. Check for severe G6PD deficiency.Chloroquine resistant P.vivax quinine sulphate 650 mgr +doxycycline 100 mgr.OR mefloquine 750 mgr.po, then 500 mgr. 12 hrs.later. for 7 daysChloroquine resistant P.falciparum quinine sulphate 325 mgr.+ doxycycline100mgr. for 7 days.

Babesiosis

hemoprotozoan parasites of the genus Babesia

Babesia microti and Babesia divergens

easily be misdiagnosed as Plasmodium

Symptomsprobably asymptomatic feverchillssweatingmyalgiasfatiguehepatosplenomegalyhemolytic anemia

Diagnosisdetection of parasites in patients' blood IFA PCR

Cystoisosporiasis

Cystoisospora belli (Isospora belli)

Symptoms Acute, nonbloody diarrhea with crampy

abdominal pain, which can last for weeks and result in malabsorption and weight loss.

In immunodepressed patients, and in infants and children, the diarrhea can be severe.

Eosinophilia may be present (differently from other protozoan infections).

Diagnosis Wet mount UV Modified acid-fast Safranin stain

Sarcocystosis

Sarcocystis bovihumanis

Symptoms often asymptomatic and clear spontaneously. mild fever, diarrhea, chills, vomiting respiratory problems

Cryptosporodiosis

Cryptosporidium parvum and Cryptosporidium hominis (formerly known as C. parvum anthroponotic genotype or genotype 1) are the most prevalent species causing disease in humans,

infections by C. felis, C. meleagridis, C. canis, and C. muris have also been reported.

Symptoms asymptomatic infections to severe, life-threatening illness; incubation period is an average of 7 days (but can range from 2 to 10 days). Watery diarrhea dehydration, weight loss, abdominal pain, fever, Nausea vomiting.

In immunocompetent persons, symptoms are usually short lived (1 to 2 weeks); they can be chronic and more severe in immunocompromised patients, especially those with CD4 counts <200/µl.

While the small intestine is the site most commonly affected, symptomatic Cryptosporidium infections have also been found in other organs including other digestive tract organs, the lungs, and possibly conjunctiva.

Oocysts in stool smears stained with modified acid-fast stain: A Cryptosporidium sp. B Cyclospora cayetanensis C Cystoisospora belli

Toxoplasmosis eating undercooked meat of animals harboring tissue

cysts . consuming food or water contaminated with cat feces

or by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat) .

blood transfusion or organ transplantation . transplacentally from mother to fetus .

Toxoplasma gondii

asymptomatic infection. cervical lymphadenopathy a flu-like illness. In rare cases ocular infection with visual loss can occur.

Immunodeficient patients ; central nervous system disease retinochoroiditis, pneumonitis, other systemic disease. In patients with AIDS, toxoplasmic encephalitis is the most common cause of intracerebral mass lesions .

Congenital toxoplasmosis results from an acute primary infection acquired by the mother during

pregnancy. The incidence and severity of congenital toxoplasmosis vary with the trimester

during which infection was acquired.

Ocular Toxoplasma infection, can be the result of congenital infection,

Observation of parasites in patient specimens, such as bronchoalveolar lavage material from immunocompromised patients, or lymph node biopsy.

Isolation of parasites from blood or other body fluids, by intraperitoneal inoculation into mice or tissue culture.

Detection of parasite genetic material by PCR, especially in detecting congenital infections in utero.

Serologic testing is the routine method of diagnosis. (T.gondii IgM and IgG)