SUBKINGDOM: PROTOZOA (“first animal”) KINGDOM: PROTISTA SUBKINGDOM: PROTOZOA (“first animal”)

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. Trophozoites: any stage in a protozoa’s life cycle which can ingest food. In practice it refers to the motile form (pseudopods, cilia, flagella). 5. Cyst: Non-motile form, protected by a membrane. This is usually the infective stage. Cysts have a thick cell wall that allows for survival in harsh environments better than the trophozoite form. Excystation: process of emergence of the trophozoite from the cyst. 7. Capable of reproduction A. Asexual: fission, budding, or schizogony (produces a large number of trophozoites) B. Sexual: conjugation

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 not motile, so it is not trophozoic. A cyst does not go and seek its nutrients or ingest food, but it can absorb nutrients. It has no organelles to ingest food.

Classification Domain: Eukaryotes Kingdom: Protista

Kingdom Protista Subkingdom: Protozoa Phylum: Sarcomastigophora Subphylum: Sarcodina (amoebas) Amoeba spp. Entamoeba histolytica Subphylum: Mastigophora (flagellates) Giardia lamblia Trichomonas vaginalis Trypanosoma spp. Phylum: Ciliata (ciliates) Paramecium spp Balandtidium coli Phylum: Apicomplexia (Sporozoa; non-motile obligate parasites) Plasmodium spp Toxoplasma gondii Cryptosporidium

Phylum: Sarcomastigophora (amoebas and flagellates) Amoebas (move by pseudopods) Flagellates (move by flagella)

Subphylum: Sarcodina (amoebas) Amoeba spp (free living; not parasitic) Nucleus Pseudopods (false foot) Entamoeba histolytica Food vacuoles Do you see a cyst (4 nuclei) or trophozoite (1 nucleus)?

Amoeba Pseudopods Nucleus Food vacuole

Amoeba Pseudopods Nucleus Food vacuole p

Amoeba Pseudopods Nucleus Food vacuole

Entamoeba histolytica Disease: Amoebiasis This is a global disease that any traveler can get. As soon as you cross the border into Mexico, you are exposed to it. Entamoeba histolytica consume red blood cells. In a fresh diarrheal specimen, you can see RBCs in the cytoplasm of the amoebas.

Entamoeba histolytica 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 Entamoeba histolytica infection can lead to amoebiasis or amoebic 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.

Entamoeba histolytica Treatment Metronidazole Diagnostic Features Ingested RBC Bull’s eye Karyosome

Entamoeba histolytica Trophozoites

Entamoeba histolytica Trophozoites of Entamoeba histolytica with ingested erythrocytes

Entamoeba histolytica Cysts

Subphylum: Mastigophora (Flagellates) Giardia lamblia (intestinal parasite) Nuclei Flagella Do you see a cyst (4 nuclei) or trophozoite (1 nuclei)? Trichomonas vaginalis (urogenital parasite) Nucleus No cyst stage Trypanosoma spp (blood parasite) Flagella (for movement) Undulating membrane (for movement) Kinetoplast (circular mass of DNA)

Mastigophora: Flagellates Giardia lamblia Disease: Giardosis Trichomonas vaginalis Disease: Trichomoniasis (an STD) Trypanosoma brucei Disease: African Trypanosomiasis Sleeping sickness Trypanosoma cruzi Disease: American Trypanosomiasis Chaga’s disease

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

Giardia lamblia Disease: Giardosis 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. 

Giardia 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.

Giardia lamblia Trophozoite

Giardia lamblia Trophozoites

Giardia lamblia Trophozoites

Giardia lamblia trophozoite

Giardia lamblia Cysts

Giardosis Abdominal pain Diarrhea Gas or bloating Headache Loss of appetite Low-grade fever Nausea Swollen or distended abdomen Vomiting

Trichomonas vaginalis Disease: Trichomoniasis 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

Trichomonas vaginalis

Trichomoniasis Usually asymptomatic in men, or mild itching In women, vagina is extremely pruritic, with vaginal odor and discharge.

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

Trypanosoma brucei Disease: African Trypanosomiasis “African Sleeping Sickness” Trypanosomiasis has a biological vector, the tsetse (pronounced “set-see”) fly. Wild animals may also be a reservoir (Zoonotic is when a disease is transmitted to animals as well as humans.) The tsetse fly bites a human and injects the trypanomastigotes into the skin. This causes a chancre (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.

Winterbottom’s Sign

Trypanosomiasis CNS symptoms Shuffling gait Slurred speech Malaise (sleeping all day) Treatment Melarsoprol: which has dangerous side-effects like chemotherapy. 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 Trypomastigote

Trypanosoma

Tsetse Fly

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

“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, hepatosplenomegaly (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

Trypanosoma brucei and cruzi Smaller posterior kinetoplast Trypanosoma cruzi Larger posterior kinetoplast American Trypanosomiasis “Chaga’s Disease” African Trypanosomiasis “Sleeping sickness”

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 Chaga's disease.

Phylum: Ciliata (ciliates) Paramecium spp (free living; non-parasitic) Oral groove Macronucleus Food vacuole Cilia Balantidium coli (intestinal parasite) Cytostome Contractile vacuoles

Phylum: Ciliata (Ciliates) Ciliates (move by cilia)

Paramecium

Balantidium coli Disease: Balantidiosis 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 This is almost identical to Entamoeba 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. 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.

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

Balantidium coli Trophozoites Cytostome

Balantidium coli Trophozoites

Balantidium coli Trophozoite

Balantidium coli Cyst

Balantidium coli Cysts

APICOMPLEXA Characteristics: has an organelle called an apical complex which allows the organism to attach to the host. They all require a biological vector for transmission (to get into the blood of the host). Organisms Plasmodium Disease: Malaria Toxoplasma gondii Disease: toxoplasmosis Cryptosporidium parvum Disease: Cryptosporidiosis

Phylum: Apicomplexia (Non-motile obligate parasites) Plasmodium spp (blood and liver parasite) Erythrocyte Leukocyte Parasite Identify the stage: Hepatic stage: Merozoites Blood stage: Ring stage trophozoites

Plasmodium spp Disease: 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

Malaria The term “malaria” comes from “mal air”, which means “bad air”. They used to think malaria was cause from the bad air of a foul-smelling swamp. Later it was discovered that the disease was caused by the protozoa inside the mosquito.  Sporozoites migrate into the salivary gland of the mosquito, and they are injected into the blood of the human. They immediately go to the liver. This is the only way to get malaria; you can’t get it from a blood transfusion because the transmission form is the sporozoite. They go right to the liver quickly to begin their next cycle.

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 more 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. 

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.

Hepatic Stage: merozoites mature into schizonts

Schizonts: Hepatic Stage

Blood Phase: Rings 0f trophozoites in RBCs

Blood Phase: Rings

Malaria Merozoites being released from lysed RBC.

Gametocyte: Blood Stage

Gametocyte: Blood Stage

Toxoplasma gondii Disease: Toxoplasmosis Infects most species of warm blooded animals, including humans. 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. Pregnant women who clean the litter box can catch the mild disease, but the fetus has severe symptoms.

Toxplasmosis Most primary infections produce no symptoms. The time between exposure to the parasite and symptom development is 1 - 2 weeks. The disease can affect the brain, lung, heart, eyes, or liver. Symptoms are mild illness with fever, muscle pain, sore throat, headache, enlarged lymph nodes. This organism prefers nerve tissue, so it travels to the CNS. Pregnant women should avoid cleaning cat litter boxes, because the fetus can develop mental retardation, blindness and epilepsy, and stillbirths.

Toxplasmosis Cyst Cyst in brain tissue

Toxplasmosis Trophozoites

Toxoplasmosis Trophozoites

Toxoplasma Trophozoites sometimes form rosettes

Toxplasmosis Oocyst

Toxplasmosis Ocular toxoplasmosis

Cryptosporidium parvum Disease: Cryptosporidiosis 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. AIDS patients have been known to have 50 stools a day, with tremendous water and weight loss. In these patients, the disease may persist for years.