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