Dr. R. E. Tan

Other tissue dwelling Protozoans

Toxoplasma PneumocystisMicrosporidiaBabesia

Genus Toxoplasma

Toxoplasma gondii one of the most common protozoan parasites in the world toxoplasma, form the Greek "toxon" meaning arc or crescent

shape The species name is derived from the rodent, Ctenodactylus

gondii from which the T. gondii was first isolated T. gondii is classified into:

phylum Apicomplexa class Sporozoa

subclass Coccidia It is related to the parasites Plasmodium (the agents of

malaria), Cryptosporidium, Isospora, Neospora and Sarcocystis

T. gondii is an obligate intracellular parasite which means that it is only able to reproduce inside cells Maybe found in many kinds of tissues including muscles and

intestinal epithelium

definitive hosts: domestic & wild cats and certain members of the Felidae family

intermediate hosts: humans, many mammals, rodents, pigs, herbivores and birds

cosmopolitan distribution able to infect a wide variety of vertebrate hosts (warm-

blooded animals) human infection common in many parts of the world Most common congenitally acquired parasitic infection most infection benign and asymptomatic

Morphology

Trophozoite motile size 4-6μm L X 2-3μm W cresent or banana-shaped with pointed anterior and rounded

posterior end nucleus single, spherical-shaped situated near the more

rounded end In human host, the asexual cycle produces:

Slender tachzoites which infect cells which is responsible for acute disease - toxoplasmosis

Shorter, broader, dormant, bradyzoites which form large tissue cysts

Cyst 5-50 µm in diameter Appears - spherical in the brain

- elongated in cardiac and skeletal muscles

Tissue Cysts - may be found in various sites throughout the body of the host, but are most common in the brain and skeletal and cardiac muscles

Oocyst ovoidal in shape 9-11μm (width) X 11-14μm (length) Mature oocyst contains 2 sporocyst with 4

sporozoite inside each sporocyst cyst develop into sporulated oocysts shed by

infected cats in the environment

sexual cycle occurs only among cats

begins in the GIT of the cat Bradyzoites are released in the

intestines where it infect cells; forms trophozoites and undergoes schizogony

Macrogametocytes and microgametocytes develop from ingested bradyzoites and fuse to form zygotes

zygotes then become encapsulated within a rigid wall and are shed as oocysts

The zygote sporulates and divides to form sporozoites within the oocyst

Sporozoites become infectious 24 hours or more after the cat sheds the oocyst. During a primary infection, the cat can excrete millions of oocysts daily for 1-3 weeks

asexual cycle involves mammals (including humans) and various strains of birds and other intermediate hosts

It consists of 2 forms: tachyzoites (the rapidly

dividing form observed in the acute phase of infection)

bradyzoites (the slowly growing form observed in tissue cysts)

Both the oocyst and tissue cysts transform into tachyzoites shortly after ingestion

Tachyzoites localize in the neural and muscle tissue and develop into tissue cyst bradyzoites

Life Cycle of T. Gondii

Modes of Transmission

cats acquires the infection by feeding on infected animals such as mice or eating infected uncooked household meat

Humans acquire the infection thru: Handling or ingestion of undercooked or raw meat

containing tissue cysts (bradyzoites) Infection can occur by ingestion of oocysts following the

handling of contaminated soil or cat litter or the consumption of contaminated water or food sources (eg, unwashed garden vegetables)

Fetus acquire infection thru: congenital transmission (Transmission of tachyzoites to

the fetus can occur via the placenta following primary maternal infection)

Disease: Toxoplasmosis

T. gondii infects a large proportion of the world's population but uncommonly causes clinically significant disease

high risk individuals for severe or life-threatening disease: Fetuses

Transplacental transmission rate: 45% 60% are subclinical; 30% may suffer severe damage; 9%

may die Stillbirths and spontaneous abortion may result

Newborns immunodeficient individuals

pts with defects of T-cell–mediated immunity, such as those with hematologic malignancies, bone marrow and solid organ transplants, or AIDS

Acute toxoplasmosis in immunocompetent host

Approximately 80-90% of patients are asymptomatic Lymphadenitis is the most common manifestation

Infected nodes are tender and discrete but not painful the infection resolves spontaneously in weeks or months Lymphadenopathy may be accompanied by fever,

malaise, fatigue, muscle pains, sore throat, and headache

Retroperitoneal and mesenteric lymphadenopathy with abdominal pain may occur

Chorioretinitis is reported

Acute toxoplasmosis in hosts who do not have AIDS but are immunodeficient

Disease may be newly acquired or may be a reactivation CNS disease occurs in 50% of patients Patients may have encephalitis, meningoencephalitis, or

mass lesions Encephalitis is an important and severe manifestation in

immunosuppressed patients including patients with AIDS Symptoms may include headache, disorientation,

drowsiness, hemiparesis, reflex changes, and convulsions

Coma and death may ensue Patients report visual changes They may have signs and symptoms similar to those

observed in immunocompetent hosts Myocarditis and pneumonitis are reported

Toxoplasmosis in AIDS patients

Brain involvement is the most common manifestation, with or without focal CNS lesions Clinical findings are altered mental state, seizures, weakness,

cranial nerve disturbances, sensory abnormalities, cerebellar signs, movement disorders, and neuropsychiatric manifestation

Pneumonitis - being increasingly recognized in AIDS patients who are not receiving appropriate anti-HIV drugs or primary prophylaxis for toxoplasmosis; primarily manifests as a prolonged febrile illness with cough and dyspnea

Toxoplasmic chorioretinitis - observed infrequently in AIDS patients; it commonly manifests with ocular pain and loss of visual acuity

Panhypopituitarism and diabetes insipidus are reported Multiple organs may be involved, and findings manifest as acute

respiratory failure and hemodynamic abnormalities similar to septic shock

GI involvement may result in abdominal pain, ascites or diarrhea

Congenital toxoplasmosis

This is most severe when maternal infection occurs early in pregnancy

Approximately 67% of patients have no signs or symptoms of infection

Mild disease may consist of slightly diminished vision severely diseased children may exhibit classic manifestations:

- chorioretinitis (15% ; most common sequela)- intracranial calcifications (10%) - microcephaly- convulsions- psychomotor disturbances- mental retardation- blindness and other visual defects- hydrocephalus (least common sequela but most severe)

Other sign of congenital toxoplasmosis present at birth includes:

maculo-papular rashes , generalized lymphadenopathy

hepatosplenomegaly , jaundice , thrombocytopenia, anemia

Laboratory Diagnosis

Clinical signs of toxoplasmosis are nonspecific and cannot be depended on for a definite diagnosis

Definitive diagnosis: demonstration of the parasite at autopsy or biopsy from lymph nodes and involved organ

Serology - demonstration of specific antibodies indirect hemagglutination test, latex agglutination test, ELISA indirect fluorescent antibody test Sabin-Feldman dye test

- gold standard for serological diagnosis of Toxoplasma

- Live virulent tachyzoites of T. gondii are used as antigen and are exposed to dilutions of the test serum and to a complement accessory factor resembling complement that is obtained from Toxoplasma-antibody free-human serum

Imaging studies ( CT scan, MRI)

Treatment

combination of: Pyrimethamine 20-25mg daily x 1 month Trisulfapyrimedine or Sulfonamides 2-6gms daily x 1 month

Spiramycin 300mg/kg x 3-4 weeks given to pregnant women to prevent transmission in utero

Prevention and Control

• raw meat • cook thoroughly• wear gloves when handling• wash hands after handling• wash cutting boards, counter tops, utensils, etc

• cat feces• clean litter box promptly (<24 hr)• wear gloves while gardening• wash hands after gardening or cleaning litter box• wash and peal fruits and vegetables• always keep cat away from the house• control strays• do not acquire new cats during pregnancy

Genus Pneumocystis

Pneumocystis jirovecii previously classified as Pneumocystis carinii was previously classified as a protozoa Currently, it is considered a fungus based on nucleic acid and

biochemical analysis Pneumocystis is a genus of unicellular fungi found in the

respiratory tracts of many mammals and humans The organism was first described in 1909 by Chagas then a few

years later by Delanöes who ultimately named the organism in honor of Dr. Carinii after isolating it from infected rats

Years later, Dr. Otto Jirovec and his group isolated the organism from humans, and it is after him that the organism responsible for PCP (pneumocystis carinii pneumonia) was renamed

Geog. Dist.: Worldwide

Trophozoites (trophic form) 1-5 µm, pleomorphic and contain a single

nucleus found in the lungs and many other

extrapulmonary specimens, especially in immunocompromised pts

Cysts thick-walled, cup-shaped, rounded, 5-8 µm in size contain up to eight “intracystic bodies” also

known as spores which are infective young trophozoites

Also found in the lungs and many other extrapulmonary specimens, especially in immunocompromised patients

Precysts (sporozoites) Oval to spherical, 4-7 µm in diameter and do not

contain intracystic bodies (but may contain one or more nuclei)

Morphology

Disease: Pneumocystis carinii pneumonia (PCP)Interstitial plasma cell pneumonitis

Mode of transmission: acquired by inhalation (aerosol droplets) Direct contact Congenital transmission is possible

human are reservoir host the most common opportunistic infection in HIV-infected patients disease more prevalent among patient who extensively use

immunosuppressive drugs, irradiation for cancer treatment and following organ transplant and in patients who have undergone bone marrow transplantation

incubation period 3-4 weeks occurs almost exclusively in immunocompromised host acute and fatal especially among infants and adults

The symptoms of PCP are very nonspecific The symptoms include dyspnea, nonproductive cough, and fever,

chest discomfort, weight loss, chills and rarely hemoptysis Extrapulmonary manifestations:

Hepatomegaly Skin lesions Bone marrow (may have necrosis with resultant pancytopenia) Lymphadenopathy Eyes (may have retinal cotton-wool spots) Thyroid (may present as a rapidly enlarging thyroid mass) GIT

It is relatively rare in people with normal immune systems but common among people with AIDS

In infected lungs, the epithelium becomes desquamated and alveoli filled with foamy exudate containing parasite The disease has a rapid onset associated with fever, cough,

rapid breathing, and cyanosis both lungs are inflamed and enlarged presence of macrophages with hyperplasia of the alveolar

epithelium with round cell infiltration lobes consolidated and septa appears gray surface and airless

Mortality rate: 100% in untreated pts

Pathogenesis

Laboratory Diagnosis

definitively confirmed by pathologic identification of the causative organism in induced sputum or bronchial washings obtained by: bronchoscopy with coloration by toluidine blue immunofluorescence assay

In situations where these two techniques cannot be used, transbronchial biopsy or open lung biopsy may prove necessary

Microscopic identification of P. jiroveci trophozoites and cysts is performed with stains that demonstrate either the nuclei of trophozoites and intracystic stages or the cyst walls

immunofluorescence microscopy using monoclonal antibodies can identify the organisms with higher sensitivity than

conventional microscopy

characteristic cysts

The most commonly employed cell wall stain is the silver stain. This stain, and its modifications, is considered the "gold standard" stain for P. carinii since it is more sensitive and specific than other stains

The cyst walls readily take up stain, but individual trophozoites do not stain

Chest radiographs should be obtained in any immunocompromised patient with fever and/or respiratory signs or symptoms

Findings include the following: Diffuse bilateral infiltrates extending from

the perihilar region Less common findings include patchy

asymmetric infiltrates and pneumatoceles Pleural effusions and intrathoracic

adenopathy The chest radiographic findings may be

normal in patients with early mild disease Pneumothorax may occur in patients using

aerosolized pentamidine The clinical diagnosis can be confirmed by

the characteristic appearance of the chest x-ray which shows widespread pulmonary infiltrates and an arterial oxygen level (pO2) strikingly lower than would be expected from symptoms

Treatment

Trimethoprim-sulfamethoxazole is the drug of choice Recommended alternatives

Pentamidine trimethoprim plus dapsone atovaquone primaquine plus clindamycin

Supportive

Genus Microsporidia

are obligate intracellular protozoan parasites belonging to the phylum Microspora 

are characterized by the production of resistant spores that vary in size, depending on the species

are ubiquitous organisms with an extensive host range, including honeybees, fish, mosquitoes, ticks, grasshoppers, rodents, rabbits, and other fur-bearing mammals

Currently, most cases are associated with HIV infection or other forms of immunosuppression, particularly in organ transplant recipients; however, cases have been reported in immunocompetent individuals

Cases of microsporidiosis have been reported in Argentina, Australia, Botswana, Brazil, Canada, Czech Republic, France, Germany, India, Italy, Japan, The Netherlands, New Zealand, Spain, Sri Lanka, Sweden, Switzerland, Thailand, Uganda, United Kingdom, United States of America, and Zambia

They possess a unique organelle, the polar tubule or polar filament, which is coiled inside the spore as demonstrated by its ultrastructure The presence of polar

tubes/filaments of the spores distinguishes Microsporidia from all other intracellular protozoans

Transmission

transmission of microsporidia is still unclear, but the most common way is thought to involved inhaling, ingesting or otherwise contracting spores

Spores of microsporidia may also be transmitted in water as species of Encephalitozoon, Enterocytozoon

Significant contact with infected animals may also transmit the disease (zoonoic infection) but cases are rare

Disease: Microsporidiosis - The phylum Microspora contains over 1000 species

Microsporidian species Clinical manifestation

Encephalitozoon intestinalis (formerly known as Septata intestinalis)

Infection of the GI tract causing diarrhea, and dissemination to ocular, genitourinary and respiratory tracts esp. among AIDS pts

Enterocytozoon bieneusiDiarrhea in AIDS pts, acalculous cholecystitis

Encephalitozoon cuniculi and Encephalitozoon hellem

Keratoconjunctivitis, infection of respiratory and genitourinary tract, disseminated infection

Microsporidium (M. ceylonensis and M. africanum)

Infection of the cornea

Nosema sp. (N. ocularum), Brachiola connori

Ocular infection

Pleistophora sp. Muscular infectionTrachipleistophora anthropophthera Disseminated infection

Trachipleistophora hominisMuscular infection, stromal keratitis, (probably disseminated infection)

Vittaforma corneae (syn. Nosema corneum)

Ocular infection, urinary tract infection

Brachiola algeraeKeratoconjunctivitis, skin and deep muscle infection

Intestinal maniifestations: Chronic diarrhea (loose, watery, nonbloody) weight loss, abdominal pain, nausea and vomiting

Disseminated infection Symptoms of cholecystitis, renal failure, and respiratory

infections Headache, nasal congestion or discharge, ocular pain, and

loss

of taste may indicate sinus involvement Patients with urinary tract involvement frequently are

asymptomatic Ocular disease

Foreign body sensation, eye pain, or both; light sensitivity, ocular redness, excessive tearing, blurred or decreased vision

Musculoskeletal: Myalgia, generalized muscle weakness, and fever are common in patients with myositis and severe

immunodeficiency states

Diagnosis

Light microscopic examination of the stained clinical smears, especially the fecal samples, is an inexpensive method of diagnosing microsporidial infections even though it does not allow identification of microsporidia to the species level The most widely used staining technique is the trichrome

stains (Chromotrope 2R method) or its modifications or Giemsa stain

This technique stains the spore and the spore wall a bright pinkish red

Transmission electron microscopy (TEM) - the gold standard and is necessary for the identification of the

microsporidian specie expensive, time consuming, and not feasible for routine

diagnosis

Treatment Drug Category

 Drug

 Treatment for

 Dose

 Precautions

Anthelmintics Albendazole

Gastro, muscle, disseminated and ocular infections.

400mg PO bid for 2-4 weeks

Avoid pregnancy

Antibiotics

Fumagillin – TopicalOral

Keratoconjunctivitis and ocular lesions (Encephalitozoon spp. B. algarae, E. hellum, E. cuniculi, V. corneae)E. bieneusi

3 mg/ml drops 1 week topical use + managementUnknown

Thrombocytopenia

AntiprotozoalsMetronidazole

E. bieneusi and others

500mg PO bid for 2 weeks.

Immunomodulatory

Thalidomide

Diarrhea when other drugs have failed

Unknown Toxic, only as last resort.Severe birth defects; avoid pregnancy.

   

Genus Babesia

are protozoan parasites of domestic and wild animals belong to the subclass Piroplamsia and are commonly referred

to as ‘piroplasms’ due to the pear-like shaped merozoites which live as small intra-erythrocytic parasites

characterized by its round, rod or abstract shape and lack of any mobility structures such as cilia or flagella

Species Host Vector Distribution

B. divergens

Man TicksYugoslavia, Russia, Ireland, Scotland

B. bigemina

Man Ticks Subtropics and Tropics

B. equi Man Ticks South America

B. microfti ManTicks(Ixodes dammini)

North America (Eastern US, Wisconsin), Asia, Russia, India, Africa

commonly infect mammals, particularly cattle, sheep, goats, horses, pigs, dogs and cats

only recently found to cause human infection severe cases seen among asplenic patient

the white-footed mouse appears to serve as the primary reservoir host for the infection

endemic in rodents along the eastern coast of U.S. MOT: bite of a tick (Ixodes dammini)

infected tick injects sporozoites (infective stage) into a mouse while taking a blood meal

In the RBC, these sporozoites mature to the trophozoite stage and then

rapidly undergo the process of merogany to produce merozoites

merozoites then burst out of the RBC and infect other cells and continue to multiply

However, some merozoites stay in the red blood cells and wait for the next host. This next host is usually a tick that is infected when biting the

animal

merozoites then differentiate into gametesThe gametes are once again ingested by the tick , where they join and

undergo the sporogony, producing sporozoites

When an infected tick bites a human for a blood meal, Babesia sporozoites are introduced into the human 

Just as in the mouse, sporozoites then go into erythrocytes , where they asexually reproduce by budding

As the parasites multiply within the blood, the disease begins to be manifested

Once within the human, the parasite cycle cannot continue, and is only transmitted human-to-human by blood transfusions

Life Cycle

Merozoites - pear-shaped and appear as small ringform within the rbc arranged parallel to each other

The organism frequently occur in: Ring-form Pairs Tetrads (“maltese cross” forms)

pathognomonic tetrads of

budding trophozoites may appear like P. falciparum

Can be differentiated from malarial parasite by the absence of hemozoin pigment in the infected erythrocyte

These different types may be found in red blood cells, lymphocytes, and histiocytes as well as other blood cells

Morphology

hemolytic disease characterized by destruction of erythrocyte Anemia due to loss of red blood cells becomes very severe because these red blood cells are being lysed (bursting)

jaundice (a yellowing of the skin and eyes) hemoglobinuria - massive destruction of the rbc allows

hemoglobin to escape together with urine Urine may appear red and internal organs may become

damaged Patients report a history of travel to an endemic area incubation period: 1-4 weeks Presents as fever which persists for weeks associated with chill,

malaise, arthalgia, myalgia, hepatosplenomegaly, fatigue and weakness

associated with severe anemia and jaundice signs and symptoms mimic malaria (P. falciparum)

Disease: Redwater fever / Babesiosis

Diagnosis

In individuals who are asymptomatic, laboratory studies may be unremarkable

Wright or Giemsa-stained peripheral blood smear shows microscopic demonstration of intra-erythrocytic parasite

Serological: indirect immunoflouresence test CBC may demonstrate mild-to-severe hemolytic anemia,

leukopenia thrombocytopenia and atypical lymphocytes Liver function test results often reveal mildly elevated hepatic

transaminase levels, erythrocyte sedimentation rate (ESR), lactic dehydrogenase (LDH) level, alkaline phosphatase level, and serum bilirubin level

Urinalysis may reveal hemoglobinuria, proteinuria, and a dark color may be present

clumped extracellular forms

intra-erythrocytic forms

intra-erythrocytic vacuolated forms

maltese cross forms

Plasmodium falciparumBabesia

combination of : Clindamycin 1.2gm IV 2x a day // 600mg orally 3x a day oral quinine 650mg 3x a day x 1wk

Pentamidine Chloroquine

Alternative: atovaquone plus azithromycin Exchange transfusions have been used in severely ill patients

with high parasitemia

Prevention and Control avoidance of animal contact which are susceptible to tick

attack avoid staying long in animal barns which are herded with cow,

horses and dogs

Treatment