Pathologic Protozoa.

Pathologic Protozoa

CHARACTERISTICS OF PROTOZOA
1. Unicellular 2. Chemoheterotrophs (get their energy by breaking down organic matter). 3. Most ingest their food; thus, they have special structures for this.

4. The vegetative form is the TROPHOZOA (tropho = movement; zoite = animal; they move like an animal). Trophozoa have special organelles for movement. 5. Capable of reproduction A. Asexual: fission, budding, or schizogony (produces a large number of trophozoites) B. Sexual: conjugation

6. Some produce cysts. These are not tissue cysts like a human gets under their skin; protozoa cysts are cellular. They have a thick cell wall that allows for survival in harsh environments better than the trophozoite form.

PROTOZOA CYSTS Cysts are not as resistant as a bacterial endospore.
You can kill cysts by boiling them. They can live in the soil or water for months. A cyst is no motile, so it is not trophozoic. A cyst does not procure its nutrients or ingest food, but it can absorb nutrients. It has no organelles to ingest food.

Classification Domain: Eukaryotes Kingdom: Protista

Classification Traditional classification of protozoa phylae was based on mode of locomotion. MASTIGOPHORA (flagella) CILIOPHORA (cilia) SARCODINA (amoebas) SPOROZOA (spore-formers) Apicomplexa (attachment organ)

Modern Classification
Modern classification of protozoa is based on how they evolved and how closely related they are (phylogenetic taxonomy), as determined by their ribosomal RNA. The human pathogenic protozoa may be classified as follows: METAMONADA (multiple flagella with feeding grooves) AMOEBOZOA (amoebas) APICOMPLEXA (attachment organ) CILIOPHORA (cilia) EUGLENOZOA (flagella and disc-shaped cristae in mitochondria)

METAMONADA Organisms Giardia lamblia Disease: Ghiardosis
Characteristics: no mitochondria, multiple flagella Organisms Giardia lamblia Disease: Ghiardosis Trichomonas vaginalis Disease: Trichomoniasis

AMOEBOZOA (amoebas) Organisms Entamoeba histolytica Naegleria fowleri
Characteristics: move by pseudopods to get food; consume red blood cells. In a fresh diarrheal specimen, you can see RBCs in the cytoplasm. Organisms Entamoeba histolytica Naegleria fowleri Disease: AMEBIASIS

APICOMPLEXA Organisms
Characteristics: has an organelle called an apical complex which allows the organism to attach to the host. Organisms Plasmodium Disease: Malaria Toxoplasma Disease: toxoplasmosis Cryptosporidium Disease: Cryptosporidiosis

CILIOPHORA CILIOPHORA: has cilia Organism Balantidium coli
Disease: Balantidiosis

EUGLENOZOA EUGLENOZOA (older classification = Mastigophora): has flagella and its mitochondria have disc-shaped cristae Organisms Trypanosoma Disease: Trypanosomiasis Leishmania donovani Disease: Leishmaniasis

TERMS Mastigote = flagella Promastigote: has single flagella
Amastigote: has no flagella Kinetoplast: round mass of circular DNA

Leishmania donovani Domain: Eukaryota Kingdom: Protista
Phylum: Euglenozoa Class: Kinetoplastida Order: Trypanosomatida Genus: Leishmania Species: donovani

Protozoa to study Giardia lambia (Giardosis)
Trichomonas vaginalis (Trichomoniasis) Entamoeba histolytica (amoebiasis) Naegleria fowleri (amoebiasis) Plasmodium vivax (malaria; most common) Plasmodium falciparum (malaria; most deadly) Cryptosporidium (Cryptosporidiosis) Toxplasmosis gondii (toxoplasmosis) Balantidium coli (Balantidiosis) Trypanosoma brucei gambiense (African Trypanosomiasis “African Sleeping Sickness”) Trypanosoma brucei rhodesiense (African Trypanosomiasis “African Sleeping Sickness”) Trypanosoma cruzi (American Trypanosomiasis “Chaga’s Disease”) Leishmania donovani (Leishmaniasis)

TERMS: Host Types The definitive host is the one in which the parasite completes its sexual life cycle. For instance, in Plasmodium, the definitive host is the tropical mosquito anopheles. The intermediate host is the human.

TERMS: Host Types Its sexual life cycle also starts in the human, so that can be confusing. What happens is the sporozoite form enters the bloodstream when the mosquito bites the human. First it begins its asexual reproduction, but if two mosquitoes inject one male and one female gametocyte into the human, there can be a sexual life cycle in the human as well.

TERMS Trophozoite: any stage in a protozoa’s life cycle which can ingest food. In practice it refers to the motile form (pseudopods, cilia, flagella). Cyst: Non-motile form, protected by a membrane. *infective stage* Excystation: process of emergence of the trophozoite from the cyst. Pseudopod: “false foot” temporary cytoplasmic process at the surface of the trophozoite.

ARCHAEZOA DISEASES Ghiardosis Trichomoniasis

Ghiardosis Organism: Ghiardia lamblia
Cysts are resistant forms and are responsible for transmission of giardiasis. Both cysts and trophozoites can be found in the feces. Infection occurs by the ingestion of cysts in contaminated water, food (includes undercooked meat), or by the fecal-oral route.

Ghiardia lamblia In the small intestine, excystation releases trophozoites (each cyst produces two trophozoites). Trophozoites multiply, remaining in the lumen where they can be free or attached to the mucosa by a ventral sucking disk. Encystation occurs as the parasites transit toward the colon. The cyst is the stage found most commonly in nondiarrheal feces. Because the cysts are infectious when passed in the stool or shortly afterward, person-to-person transmission is possible.

Ghiardia lamblia Trophozoite form: piroform (pear or teardrop shape), looks like a happy face. Discovered by Anton Van Leuwenhoek when he examined his own feces when he had this infection. You won’t see the flagella in lab because you need a special stain for that. Cyst form: oval shaped. Nuclei looks like two eyes. Geographic Distribution: Worldwide, more prevalent in warm climates, and in children.

Life Cycle of Giardia lamblia

Ghiardia lamblia Trophozoite

Ghiardia lamblia Trophozoites

Giardia lamblia trophozoite

Ghiardia lamblia Cysts

Trichomoniasis Organism:Trichomonas vaginalis
Trichomonas vaginalis resides in the female lower genital tract and the male urethra and prostate. The parasite is a trophozoite only; it does not have a cyst form, and does not survive well in the external environment. Trichomonas vaginalis is transmitted among humans, its only known host, primarily by sexual intercourse.

Trichomonas vaginalis

Trophozoite Undulating membrane

RHIZOPODA DISEASE Amebiasis Entamoeba histolytica Naegleria fowleri

Entamoeba histolytica
Disease: Amebiasis This is a global disease that any traveler can get. As soon as you cross the border into Mexico, you are exposed to it. Several protozoan species in the genus Entamoeba infect humans, but not all of them are associated with disease. Entamoeba histolytica is associated with intestinal and extraintestinal infections. The other species are important because they may be confused with E. histolytica in diagnostic investigations.

Geographic Distribution
Worldwide, with higher incidence of amebiasis in developing countries. In industrialized countries, risk groups include male homosexuals, travelers and recent immigrants, and institutionalized populations.

Entamoeba histolytica Life Cycle
Cysts and trophozoites are passed in feces. Infection occurs by ingestion fecally contaminated food (including undercooked meat), water, or hands. Excystation occurs in the small intestine and trophozoites are released, which migrate to the large intestine. The trophozoites multiply by binary fission and produce cysts, and both stages are passed in the feces.

Cysts can survive days to weeks in the external environment and are responsible for transmission. Trophozoites passed in the stool are rapidly destroyed once outside the body, and if ingested would not survive exposure to the gastric environment.

In many cases, the trophozoites remain confined to the intestinal lumen (noninvasive infection) of individuals who are asymptomatic carriers, passing cysts in their stool. In some patients the trophozoites invade the intestinal mucosa (intestinal disease), with resultant pathologic manifestations. E. histolytica can be observed with ingested red blood cells.

Diverse mammals such as dogs and cats can become infected but usually do not shed cysts with their feces, thus do not contribute significantly to transmission. The active (trophozoite) stage exists only in the host and in fresh feces; cysts survive outside the host in water and soils and on foods, especially under moist conditions on the latter. It is NOT caused by undercooked meat.

Entamoeba histolytica, as its name suggests, can actually bore through the enteric walls (histolysis = destroying tissue) and reach the blood stream. From there, it can reach different vital organs of the human body, like the liver, lungs, brain, eyes etc. A typical effect is a liver abscess caused by such migrating Entamoeba histolytica, which can be fatal.

Entamoeba histolytica infection can lead to amebiasis or amebic dysentery. Symptoms include dysentery, diarrhea, weight loss, fatigue, and abdominal pain. It can be diagnosed by stool samples. Trophozoites should be seen in a fresh fecal smear and cysts in an ordinary stool sample.

Treatment Metronidazole Diagnostic Features Ingested RBC Bull’s eye Karyosome

Entamoeba histolytica Trophozoites

Trophozoites of Entamoeba histolytica with ingested erythrocytes

Cysts

Naegleria fowleri Disease: Amebiasis; meningitis form
Acute, usually lethal, central nervous system (CNS) disease. Three stages: Cysts Trophozoites Flagellated forms

Naegleria fowleri Naegleria fowleri is found in fresh water, soil, heated swimming pools, hydrotherapy pools, aquariums, and sewage. Trophozoites infect humans or animals by entering the olfactory epithelium and reaching the brain.

Naegleria fowleri Trophozoites

APICOMPLEXA All members of this phylum have an organelle called an apical complex (located at the apex of the cell) which allows the organism to attach to the host. This is a type of adhesion complex. They all require a biological vector for transmission (to get into the blood of the host). They have at least two hosts: the animal vector and the human host. That makes it a complex life cycle. Because it uses an animal host, there is an animal reservoir. Definitive Host: where the parasite completes its sexual life cycle. Intermediate Host: where the parasite goes through its asexual cycle.

APICOMPLEXA DISEASES Malaria Toxoplasmosis Cryptosporidiosis

Malaria Causal Agents: Plasmodium vivax (most common)
Plasmodium falciparum (most deadly) P. ovale P. malariae.

Plasmodium

Malaria 200-300 million infections a year 2-3 million deaths a year
Affects mostly young people and teenagers 2/3 of the cases are in Africa

Plasmodium The malaria parasite life cycle involves two hosts.
Sporogenic Stage During a blood meal, a malaria-infected female Anopheles mosquito inoculates sporozoites into the human host. Hepatic Stage Sporozoites infect liver cells and mature into schizonts , which rupture and release merozoites into the bloodstream. Blood Stage Merozoites infect red blood cells The parasites undergo asexual multiplication in the erythrocytes. The ring stage trophozoites mature into schizonts, which rupture releasing merozoites. Some parasites differentiate into male and female gametocytes. Blood stage parasites are responsible for the clinical manifestations of the disease.

Plasmodium The male and female gametocytes are ingested by another Anopheles mosquito. The parasites’ multiplication in the mosquito is known as the sporogonic cycle, generating zygotes. The zygotes 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.

Malaria Symptoms Fever, chills, sweating, headaches, muscle pains
Severe complications (cerebral malaria, anemia, kidney failure) can result in death.

Anopheles Mosquitoes Female mosquitoes need blood meals to nourish their eggs.

Schizont: Hepatic Stage

Blood Phase: Rings

Malaria Merozoites being released from lysed RBC.

Gametocyte: Blood Stage

Toxoplasmosis Organism: Toxplasmosis gondii
Infects most species of warm blooded animals, including humans.

Toxplasmosis gondii

Toxplasmosis Cats are the only known definitive hosts for the sexual stages of T. gondii and thus are the main reservoirs of infection. Cats become infected by eating infected wild animals (e.g. birds) Tissue cysts or oocysts are excreted in the feces. Oocysts can survive in the environment for several months and are remarkably resistant to disinfectants.

Toxplasmosis Human infection may be acquired in several ways:
A) ingestion of undercooked infected meat B) ingestion of the oocyst from fecally contaminated hands or food C) organ transplantation or blood transfusion D) transplacental transmission

Toxplasmosis Geographic Distribution: Serologic prevalence data indicate that toxoplasmosis is one of the most common of humans infections throughout the world. Infection is more common in warm climates and at lower altitudes than in cold climates and mountainous regions. High prevalence of infection in France has been related to a preference for eating raw or undercooked meat High prevalence in Central America has been related to the frequency of stray cats.

Toxplasmosis Cyst Cyst in brain tissue

Toxplasmosis Tachyzoites

Toxoplasmosis Trophozoites

Toxplasmosis Oocyst

Toxoplasma tachizoites

Toxplasmosis Ocular toxoplasmosis

Cryptosporidiosis Organism: Cryptosporidium
Spread through the fecal-oral route, often through contaminated water Causes self-limiting diarrhea in people with intact immune systems. In immunocompromised individuals (such as AIDS patients), symptoms are severe and often fatal.

Cryptosporidium

CILIOPHORA DISEASE Disease: Balantidiosis Organism: Balentidium coli (The name tells you it lives in the colon) The animal reservoir is the pig. Its geographical distribution is world-wide, wherever humans and pigs live nearby each other. This is the only ciliated protozoan that causes disease in humans.

Balantidiosis Causal Agent: Balantidium coli
This is almost identical to Enamoeba histolytica. The cyst form is infective. It has a thick wall to protect it from stomach acid. It enters the human (and dogs) by ingestion of fecal contaminants on food, water, and hands.

Balantidiosis Once in the colon, it undergoes excystment (cyst transforms into trophozoite). In the trophozoite form, they reproduce in the large intestine, invade the colon wall, and cause ulcerations in the colon. Like Entamoeba, it leaves a flask-shaped ulcer. Symptoms include diarrhea and GI discomfort.

Balantidiosis Cysts are the parasite stage responsible for transmission. The host acquires the cyst through ingestion of contaminated food or water (NOT in undercooked meat). Common in pigs

Balantidium coli Following ingestion, excystation occurs in the small intestine, and the trophozoites colonize the large intestine. The trophozoites reside in the lumen of the large intestine of humans and animals, where they replicate by binary fission, during which conjugation may occur. Trophozoites undergo encystation to produce infective cysts. Mature cysts are passed with feces.

Balantidium coli

Balantidium coli Trophozoites characterized by:
Large size (40 µm to more than 70 µm). Presence of cilia on the cell surface A cytostome. A bean shaped macronucleus which is often visible and a smaller, less conspicuous micronucleus.

Balantidium coli Trophozoites Cytostome Cytostome

Balantidium coli Trophozoites

Balantidium coli Trophozoite

Balantidium coli Cyst

Balantidium coli Cysts

MASTIGOPHORA DISEASES
Trypanosomiasis Leishmaniasis

Trypanosomiasis African Trypanosomiasis American Trypanosomiasis
(African Sleeping Sickness) American Trypanosomiasis (Chaga’s Disease)

“African Sleeping Sickness”
Disease: African Tryptanosomiasis Causal Agents: Trypanosoma brucei gambiense Trypanosoma brucei rhodesiense

Geographic Distribution
T. b. gambiense is found in foci in large areas of West and Central Africa. Humans are the main reservoir for Trypanosoma brucei gambiense, but this species can also be found in animals. T. b. rhodesiense is found in East and Southeast Africa. Wild game animals are the main reservoir of T. b. rhodesiense.

Trypanosomiasis Trypanosomiasis has a biological vector, the tsetse (pronounced “set-see”) fly. Wild animals may also be a reservoir (Zooinotic is when a disease is transmitted to animals as well as humans.)

Trypanosomiasis The tsetse fly bites a human and injects the trypanomastigotes into the skin. This causes a chanchre (pronounced “shanker”), which is an ulcer on the skin. Then it enters the lymphatic system.

Trypanosomiasis It is characterized by Winterbottom’s Sign: swelling of the cervical lymph nodes in the head and neck area. CNS symptoms include a shuffling gait (like a stroke victim), slurred speech, and malaise (needing to sleep longer and longer each day). They are also restless at night.

Trypanosomiasis CNS symptoms Shuffling gait Slurred speech
Malaise (sleeping all day) Treatment Melarsoprol: which has dangerous side-effects like chemostherapy. This drug requires administration with a substance called ethylene glycol, which will break down regular plastic tubing, so the drug must be administered with special plastic iv tubing.

Trypanosoma brucei Trypomastigote stages are the only form found in patients. Posterior kinetoplast Centrally located nucleus Undulating membrane Anterior flagellum

Trypanosoma brucei

Trypanosoma brucei gambiense
trypomastigote

Trypanosoma

Trypanosoma brucei rhodesiense

Trypanosoma brucei UM

Tsetse Fly

“Chaga’s Disease” Disease: American Tryptanosomiasis
A zoonotic disease (can infect animals) that can be transmitted to humans by blood-sucking bugs. Causal Agent: Trypanosoma cruzi This organism is a little smaller than T. bruceii and has a pronounced gametoplast.

“Chaga’s Disease” This disease is NOT found in Africa.
This disease is also zoonotic; it can infect animals as well as humans. The vector is a large bug called the “Kissing Bug”. It is found in warm regions and crowded areas, especially in the cracks of adobe huts. It comes out at night and crawls on a human while they sleep.

“Chaga’s Disease” It prefers the lips because the blood supply is close to the surface. It sucks the blood there, but they don’t transmit the organism this way. When they suck the blood, they also defecate, and the organism is in the feces. When the human wakes up to scratch the itch, feces get into the tiny wound. This is a fecal blood route.

“Chaga’s Disease” Symptoms include fever, anorexia, swollen lymph nodes, hepatosplenomegally (enlarged liver and spleen), and myocarditis (inflammation of the heart), which usually causes death. They also have megacolon (large colon) and megaesophagus (large esophagus).

Trypanosoma cruzi Insect vector is the “kissing” bug. It takes a blood meal and releases trypomastigotes in its feces near the site of the bite wound. Trypomastigotes enter the host through the wound or through intact mucosal membranes, such as the conjunctiva. Trypanosoma cruzi can also be transmitted through blood transfusions, organ transplantation, transplacentally, and in laboratory accidents.

Trypanosoma cruzi Geographic Distribution: The Americas from the southern United States to southern Argentina. Mostly in poor, rural areas of Central and South America. Chronic Chagas disease is a major health problem in many Latin American countries. With increased population movements, the possibility of transmission by blood transfusion has become more substantial in the United States.

Trypanosoma cruzi

Trypanosoma cruzi large kinetoplast

Trypanosoma cruzi Triatomine bug, Trypanosoma cruzi vector, defecating on the wound after taking a blood meal.

Kissing Bug

Romana’s sign Swollen eye, seen in Chagra’s disease.

TERMS Promastigote: has single flagella Amastigote: has no flagella
Kinetoplast: round mass of circular DNA

Leishmania donovani Domain: Eukaryota Kingdom: Protista
Phylum: Mastigophora Class: Kinetoplastida Order: Trypanosomatida Genus: Leishmania Species: donovani

Leishmania donovani Disease: Leishmaniasis
Vector-borne disease transmitted by sandflies.

Leishmania Life Cycle It starts out as a spindle-shaped, single flagellated cell called a promastigote (mastigote means flagella). You can also see the nucleus and a kinetoplast (mass of circular DNA). Kinetoplast

Leishmania rosette In prepared slides you can see promastigotes align their nose in a circle, called a rosette.

Leishmaniasis rosette

Leishmania Life Cycle It reproduces in the gut of a female sandfly, and migrates to her proboscis (mouth part). It is introduced into the human by her bite. It then enters a macrophage and becomes intracellular. Here, it loses its flagella and is now known as an amastigote.

Leishmaniasis These amastigotes multiply in various organs including the spleen, liver, and lymph nodes. Symptoms include hepatosplenomegaly, lymph adenopathy, fever, weight loss, and a decrease in all blood cells: WBC, RBC, and platelets. The treatment is almost as bad as the disease because of the side effects. It is best to catch it early.

Leishmania Life Cycle The female sandflies inject the infective stage, promastigotes, during blood meals. Macrophages phagocytize them and they transform into amastigotes. Other sandflies become infected during blood meals when they ingest infected macrophages. In the sandfly's midgut, the parasites differentiate into promastigotes, which multiply and migrate to the proboscis.

Leishmaniasis Life Cycle

Leishmania donovani (Promastigote)
Single flagellum found in sand flies

Leishmaniasis Macrophage rupturing Amastogotes
Amastogotes with nucleus and kinetoplast

Leishmania Amastigotes

Sandfly This looks like a mosquito, except its body is hairy and the wings are feathery.

Leishmaniasis Geographic Distribution: More than 90 percent of the world's cases of visceral leishmaniasis are in India, Bangladesh, Nepal, Sudan, and Brazil. Leishmaniasis is also found in Mexico, Central America, and South America, southern Europe, Asia, the Middle East, and Africa.

Leishmaniasis Cutaneous Mucocutaneus Visceral
There are three forms of Leishmaniasis: Cutaneous Mucocutaneus Visceral

Cutaneous Leishmaniasis
The disease is only at the site of the bite. This form is seen in Texas, Mexico, Asia, and the Middle East (our Iraq troops are coming down with this form). It manifests as a large, wet sore with raised edges. It looks like a volcano with weepy serum coming out of the center. The wound is not contagious, just the sandfly bite. Dogs can get this disease, too.

Leishmaniasis (cutaneous)

Leishmaniasis (mucocunateous)
This is when the disease located in the mucous membranes of the nose and mouth. The most gruesome photos are of this form.

Leishmaniasis (mucocunateous)

Leishmaniasis (visceral)
This is the most serious form. It occurs especially in immunocompromised people, especially HIV patients. The amastagotes reproduce inside macrophages. Only T-cells can kill infected macrophages, but HIV is a disease that infects T-cells. This form is known as Kala Azar.

Kala Azar Hepatosplenomegaly

Kala Azar (duodenum)

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