Coccidia and Pneumocystis

Nimit Morakote, Ph.D.

2016

1

Learning objectives

• After class, students will be able to: • Describe morphology, life cycle, signs and symptoms, prevention and

control, laboratory diagnosis and treatment of coccidian of man and Pneumocystis

• Differentiate oocysts of coccidian causing human infection

2

Coccidia

• Collectively intracellular organisms in suborder Eimeriorina in Phylum Apicomplexa

• 10 families, at least 42 genera, and over 2,000 named species

• Life history has both asexual and sexual phase of development

3

Asexual reproduction

• From one cell to 2 or many cells

• Multiple fission = one cell → many cells • Termed “Merogony” or “schizogony”

• Internal budding = one cell → 2 or many cells • Termed “Endodyogeny” and “Endopolygeny”

4

Replication by the Apicomplexa.

Morrissette N S , and Sibley L D Microbiol. Mol. Biol. Rev. 2002;66:21-38

Endodyogeny

Schizogony or merogony

Meront or schizont

Merozoites

Sexual reproduction

• Sex cell production termed “Gametogony” Merozoite

Macrogamont

(macrogametocyte)

Many

microgametes

Microgamont

(microgametocyte)

Microgamete

(macrogamete)

fertilization Zygote

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• Sporogony: production of sporozoites

Zygote

Oocyst (immature or unsporulated)

Oocyst (mature or sporulated, infective) sporozoite

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Taxonomy of coccidia

• Based on number of sporocysts and sporozoites in sporulated oocyst

Unsporulated oocyst

Sporulated oocyst

sporozoites

sporocysts

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Taxonomy- coccidia of medical importance

0+4 Cryptosporidium Naked sporozoites

2+4 Cyclospora

2+8 Cystoisospora Toxoplasma Sarcocystis

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Coccidia of medical importance Life cycle Opportunist Affected organs/

Disease in man

Toxoplasma gondii Complex

Cat=DH

+ Brain-Toxoplasmic

encephalitis

Developing organs-

Congenital

toxoplasmosis

Sarcocystis bovihominis,

S. hominis

Complex

Cattle, pig=IH

- Small intestine-

Eosinophilic enteritis

S. nesbitti or other spp. Cobra=DH - Muscle

Cystoisospora belli Simple + Small intestine-Diarrhea

Cryptospridium Simple + Small intestine-Diarrhea

Cyclospora

cayetanensis

Simple + Small intestine-Diarrhea

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Toxoplasma gondii

• Disease: toxoplasmosis • Congenital toxoplasmosis

• Toxoplasmic encephalitis in AIDS

• Stages in life cycle • Tachyzoites, 6 x 2 µm: during acute stage of

infection

• Bradyzoites, during chronic stage of infection

• Oocyst, 10 x 12 µm

tachyzoite

Sporulated oocyst

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Life cycle

rowdysites.msudenver.edu

PP=3-10 d

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Enteroepithelial cycle • Merogony • Gametogony • Fertilization

Sporulation

Asexual phase

tachyzoites

Bradyzoites In tissue cysts

sporozoites

Human infection

• Man acquires infection from • Consumption of improperly cooked

meat (tissue cysts)

• Drinking unfiltered water (oocysts)

• Contaminated hand (oocysts)

• Organ transplant, blood transfusion (tachyzoites)

Medical-labs.net

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Pathogenesis, Signs, Symptoms

• Acute phase- tachyzoites invade and destroy host cells

• Lymphadenopathy, flu-like symptoms

• Chronic phase • Immune pressure: Tachyzoites bradyzoites

(tissue cysts) in brain, muscle, liver

• Symptomless

• Reactivate in AIDS toxoplasmic encephalitis

• Congenital toxoplasmosis: chorioretinitis, hydrocephalus, intracerebral calcification

Medical-labs.net

14

Diagnosis, prevention & treatment

• Isolation of parasite impractical

• Primarily diagnosed by serology (antibody detection)

• Serological survey shows worldwide distribution including Thailand

• Prevention by • Properly cook meat,

• Proper handling of cat’s faeces

• Treatment: pyrimethamine and sulfadiazine, plus folinic acid.

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Sarcocystis spp.

• Affect intestine

• Human as definitive host • S. hominis: bovine = IH

• S. suihominis: porcrine = IH

• Intestinal sarcocystosis

• Usually no signs and symptoms, a few cases of segmental eosinophilic enteritis

• Not opportunistic parasite

• Affect muscle

• Man as accidental host • S. nesbitti of snake (cobra)

• Muscular sarcocystosis

• Fever, and/or myalgia, arthralgia, headache, fatigue

• Later myositis: pain and swelling. Eosinophilia, high CPK

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S. hominis and S. suihominis

• Oocysts: thin-walled, sporulated when come out in faeces; “8”-like

• Sporocyst size: • 15 x 9 m (S. hominis); 13 x 9 m (S. suihominis)

• Sarcocysts with septa • Bradyzoites (banana shape)

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Humans as definitive (final) hosts for Sarcocystis species.

Ronald Fayer et al. Clin. Microbiol. Rev. 2015;28:295-311

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Humans as aberrant intermediate hosts for Sarcocystis species.

Ronald Fayer et al. Clin. Microbiol. Rev. 2015;28:295-311

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Diagnosis

• Intestinal sarcocystosis • Microscopic observation of

oocysts or sporocysts in fecal smear

• Wet fecal smear- sporulated oocysts

• Acid fast stain- irregular staining (some stained, some don’t)

• Muscular sarcocystosis • Tissue biopsy, section and

stained.

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From: Parasite.czu.cz

From: jcm.asm.org

Cystoisospora belli

• Only in human and primate

• Asexual and sexual reproduction in epithelial cell of the small intestine

• Oocyst sporulation outside host: 1-5 days

• Acute infection: diarrhea, self-limited

• Immunodeficient person: severe diarrhea

• Diagnosis: unsporulated oocyst, 20-23 x 10-19 m

• Treatment: trimethoprim and sulfamethoxazole

Fresh faecal smear

Acid fast stained smear

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Cryptosporidium

• Parasite of mammals, birds, reptiles, fish, amphibians: rather host-nonspecific

• Human: mostly C. parvum, C. hominis

• Oocyst 5 µm in diameter, smallest of all human coccidian

• 4 naked sporozoites

Acid-fast stained smear (getfor.4t.com)

Unstained faecal smear (marvistavet.com)

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• Life cycle similar to Cystoisospora belli (development occurs in GI epithelium) except:

• Organism is intracellular, extracytoplasmic

• Sporulation in host cells- • thick-wall oocysts

• thin-wall oocysts (autoinfective)

• PP app. 2 days, IP app. 7-10 days

Electron micrograph (phoenixwaterfilter.com.au)

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• Emerging infectious disease

• Impaired intestinal absorption + enhanced secretion

• Watery diarrhea, abdominal cramp, fever

• In immunocompetent persons, self-limited in 2 wk.

• In immunocompromised persons, severe diarrhea and malabsorption syndrome

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• An important opportunist in AIDS patients

• 4 Clinical patterns: • < 4 stool/day

• diarrhea < 2 mo.

• Diarrhea > 2 mo.

• Fulminant infection, 2L watery stool daily (CD4 < 50/microliter)

• Extraintestinal dissemination can occur, most common= biliary tract

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• Infection worldwide including Thailand • Account for 5% of patient diarrhea

• Contaminated drinking water, food, direct contact

• Clam

• Outbreak involving 403,000 persons in Milwaukee associated with drinking water

• No effective, specific chemotherapy

• Diagnosis by stool exam for oocysts

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Cyclospora cayetanensis

• Man is the only host

• Infect the small intestine, similar life cycle with C. belli diarrhea

• Unsporulated when come out with faeces

• Sporulation requires 7-15 days in external environment

• 2 sporocysts, each with 2 sporozoites

• IP app. 7 days

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• Diarrhea (5-15 times/day)

• Self-limited (19-57 days), recurrent,

• More severe in AIDS patients

• Traveler's diarrhea • Implicated in Europeans returning

from Asian/South American countries

• Indonesia, Nepal, Thailand, Guatemala, Mexico

• Imported vegetables, salad & fruits = most frequent source of infection

• Oocysts survive a week at 4 C

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• Diagnosis • Stool exam for oocysts

• Acid fast stain- must differentiate from Cryptoporidium

• Oocyst slightly bigger than Cryptosporidium oocyst, i.e., 8.6 m

• Staining not uniform: dark red, unstained

• Prevention & control: avoid exotic salad & vegetable or wash well

• Treatment: Trimethoprim, sulfamethoxazole

Cyclospora oocyst

Unsporulated: cdc.gov

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Pneumocystis jirovecii

• First identified in 1909 in rat lung, named Pneumocystis carinii of uncertained taxonomy

• Cause infantile pneumonia

• Recently classified as atypical fungus Renamed Pneumocystis jirovecii to be distinctive from rat’s species

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Morphology

• Extracellular, obligate, host-specific, yeast-like parasitic fungi

• Live in alveoli

• Trophic forms (1-4 µm) adhere to alveolar epithelium

• Precyst stages (early, intermediate, late)

• Mature cyst or ascus (8-10 µm) with 8 intracystic bodies (spores)

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Putative life cycle of Pneumocystis.

Beck J M , and Cushion M T Eukaryotic Cell 2009;8:446-460

Disease and treatment

• Pneumocystis pneumonia, interstitial plasma cell pneumonia

• Premature infants • AIDS • Organ transplant subjects • Malignancies • Steroid treatment, long term

• Fever, cough, dyspnea

• Radiograph: bilateral, diffuse, reticular, or granular opacities

• Trimethoprimsulfamethoxazole (TMP-SMX) • Chemoprophylaxis when CD4 < 200

cells/microliter

Histogical picture:

Alveolar spaces filled with

eosinophilic, vacuolated or

foamy exudate containing 4-

5um cysts

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Epidemiology

• Niches uncertain, airborne transmission

• Human acquires infection during infancy, asymptomatic, latent infection

• Reactivated when immunocompromised or primary infection is still a debate

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Diagnosis

• Specimen from lungs • Induced sputum

• Bronchoalveolar lavage (BAL)

• Stain for cysts • Methenamine silver nitrate

• Toluidine Blue O

• Stain for trophics forms and intracystic bodies

• Giemsa stain

Beck J M , and Cushion M T Eukaryotic Cell 2009;8:446-460

Finish