Parasitology
Sporozoons
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 Mexico
Central America,
South America
southern 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 through
blood 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 initial
infection.
 cardiomyopathy (the most serious manifestation);
 megaesophagus
 megacolon;
 weight loss.
Chronic Chagas disease and its complications can be fatal.

Diagnosis
Microscopic 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.
Diagnosis
Naegleria 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
 Plasmodium
 Plasmodium
 Plasmodium

vivax
malariae
ovale
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 .

Symptoms
The 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
Immature schizont in a thin blood smear.
Mature schizont.
trophozoites
Treatment
Quinine ( 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 days
Chloroquine 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
Symptoms
probably asymptomatic
fever
chills
sweating
myalgias
fatigue
hepatosplenomegaly
hemolytic anemia
Diagnosis
detection 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 fecalcontaminated 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)