Protista / ProtozoaProtista / ProtozoaMicrobiology 2314

CharacteristicsCharacteristics

• Abundant / Simplest Animals / Few are Pathogenic

CharacteristicsCharacteristics

• Unicellular / Eukaryotic /• Chemoheterotrophic (Saprophytic)

CharacteristicsCharacteristics• Aquatic and Terrestrial• Diverse / Population Size Varies by

Location

CharacteristicsCharacteristics

• Water Quality• Prominent in Soil / 1000-100,000 org/g

GrowthGrowth

• Aerobic

• pH 3.5 to 9.0

• Mesophiles (High Temps are Detrimental)

• Water / Required for Ciliated Forms

• Flagellated Forms are More Drought Resistant

• Not All Cysts Can Resist Dessication

Life Cycle Life Cycle

• Active – Trophozoite Stage

• Inactive – Cyst Phase

Balantidium coli cyst

Balantidium coli trophozoite

FeedingFeeding

• Saprophytic / Phagocytic / Pinocytic

Selective FeedersSelective Feeders

• Ciliates / Bacteria / Yeasts / Protozoa / Rotifers• Amoeba / Bacteria / Protozoa / Yeasts / Spores /

Algae

FeedingFeeding

• Protozoa are Critical in the Digestion of Cellulose

• Protozoa live in the gut of termites and wood roaches and obtain food from the foraging activities of the insects. In return, the protozoa use their specialized enzymes to break down cellulose, a polymer of glucose, for the insects.

How does the toxic substance Sulflurimid work?

Protozoa Have An Effect On The Structure And Function Of

Microbial Communities

Predator Prey RelationshipPredator Prey Relationship

Increases in bacterial populations are followed by an increase in protozoa population

• Alleopathy (The harmful effect of one organism on another.

• Protozoa Can Keep A Microbial Group From Dominating A Given System

* Hudson Bay Trading Company

Why Don’t Protozoa Completely Why Don’t Protozoa Completely Eliminate Their Prey?Eliminate Their Prey?

• As one population declines they switch to eating another

• Prey are sometimes protected

• Predators often have predators of their own

ReproductionReproduction

• Asexual

1. Fission

2. Schizogony

3. Budding• Sexual

Amoeba

AmoebasAmoebas

• Subphylum Sarcodina

• Move by Psuedopodia

• Entamoeba histolytica / Amoebic Dysentery (Destruction of Red Blood Cells)

• Survival Structures / Cysts

• Acanthamoeba can enter the skin through a cut, wound, or through the nostrils. Once inside the body, amebas can travel to the lungs and through the bloodstream to other parts of the body, especially the central nervous system (brain and spinal cord).

• About 10 percent of the world's population is infected with E. Histolytica.

• It is the third most common cause of death (after Schistosomiasis and Malaria) from parasitic infections, and second protozoal cause (after malaria).

• Very common in South and Central America, West Africa and Southeast Asia. Rare in temperate climates.

• About 90% of infections are asymptomatic and the remaining 10% produce a spectrum of disease varying from dysentery to amoebic liver abscess.

Cyst of Entamoeba histolytica in a fecal smear

Obtained via Fecal/Oral Route

Cyst

After ingestion, the trophozoites penetrate the walls of the large intestine causing ulcerations and symptoms of dysentery.

May result in “Bloody Diarrhea”,

Histological preparation showing cross-section of ulcer. Note the high degree of necrosis in center of ulcer. The ameba are advancing laterally under the intact mucosa.

Smear showing several hematophagous trophozoites.

Trophozoite of Entamoeba histolytica.

E. histolytica is found primarily in the colon where it can live as a non-pathogenic commensal or invade the intestinal mucosa (green). The ameba can metastasize to other organs via a hematogenous route (purple); primarily involving the portal vein and liver. The ameba can also spread via a direct expansion (blue) causing a pulmonary infection, cutaneous lesions or perianal ulcers

The organism produces protective cysts, which pass out of the intestines with the feces

and are ingested via contaminated food and water by the next host. This is known as

the Fecal-Oral Route.

Acanthamoeba can infect the eye (resulting in blindness), blood,

spinal cord, and brain. It is transmitted by waterborne cysts picked up while swimming in

contaminated water.

Acanthamoeba results in lesions of the skin, eye, brain, etc.

Trophozoite of Acanthamoeba spp. within necrotic tissue at higher magnification

FlagellatesFlagellates

• Subphylum Mastigophora

• Flagella / Undulating Membrane

• Giardia lambia / Giardiasis

• Trichomonas vaginalis (Male and Female Infections)

• Trypanosoma bruicei gambiens

Trypanosoma gambiense in a blood smear

TrypanosomitesTrypanosomites

• T. gambiense and T. rhodesiense cause the disease African sleeping sickness or African trypanosomiasis. They are transmitted to humans by the bite of an infected tsetse fly (a vector) with east African wild bovine as the reservoir. The disease primarily involves the lymphatic and nervous systems of humans and is diagnosed by microscopically looking for Trypanosoma in the blood, in aspirated fluid from lymph nodes, or in spinal fluid. T. cruzi causes South American sleeping sickness or Chagas' disease and is transmitted by infected Triatomid bugs (kissing bugs) with the Spiny Anteater as the reservoir.

Giardia lamblia Cyst in a fecal smear

This tear-drop shaped flagellated protozoan lives in the small intestine and is transmitted primarily when the infective cysts are ingested in water. It is an example of what is known as a Zoonosis, a parasite found in wild animals which can be transmitted to humans. It gained notoriety some years ago when an outbreak occurred in Banff National Park and was termed by the Media as BEAVER FEVER because the local beavers were thought to be the source of contamination of the water supply.

GiardiasisGiardiasis

• Giardiasis is the most common protozoan intestinal disease in the U.S. and is transmitted by the fecal-oral route. Cysts of the organism are ingested through fecally-contaminated food, water, etc. Giardiasis is diagnosed by microscopically looking for cysts of G. lamblia in fecal smears. Results in uncontrollable “Greasy” Diarrhea.

Trichomonas vaginalis in vaginal discharge

Massive numbers of trophozoites can cover the epithelial surface resulting in a cobblestone road like appearance

Genital TrichomoniasisGenital Trichomoniasis

• There are an estimated 2.5 million cases per year in the U.S. In females, it usually appears as vaginitis with itching and a white discharge. In males it is often asymptomatic but may cause urethritis. It is transmitted mainly by sexual contact and is diagnosed by microscopically looking for T. vaginalis trophozoites in vaginal discharge and urine

LishmaniasisLishmaniasis

• A protozoan infection involving a number of species of the genus Leishmania. There are two distinct groups of clinical presentations.

• Visceral leishmaniasis:presenting with a systemic illness of fever, splenomegaly and lymphadenopathy (caused by Leishmania donovani) -- other names Kala azar, Dum Dum fever.

• Cutaneous leishmaniasis: presenting with a skin ulcer or ulcers. A varient can also involve mucous membranes of nose and throat.

• These are almost always zoonoses with a dog or rodent reservoir, and are transmitted to man by sandfly bite. They are distributed throughout the tropics.

Lishmania Protozoa in SmearLishmania Protozoa in Smear

Sandfly Vector

cutaneous leishmaniasis

• The most commonly used drug against kala-azar, pentavalent antimony (sodium stibogluconate), has been the cornerstone of therapy worldwide for more than 70 years. It has to be administered through a drip and is painful, toxic, with dangerous side effects, and can be fatal. In addition, this medicine is no longer effective against the disease in large parts of India.

CiliophoraCiliophora

CiliatesCiliates

• The only pathogen in this group is Balantidium coli, which causes a diarrhea-type infection called balantidiasis. The protozoan is transmitted to humans by the fecal-oral route and invades the large intestines causing ulceration. It is diagnosed by microscopically looking for B. coli in a fecal smear

Hosts

• Hosts include pigs, wild boars, rats, primates (including humans), horses, cattle and guinea pigs.

• Infection is transmitted within or between these species by fecal-oral transmission.

• Pigs are the most significant reservoir hosts, though they show few if any symptoms.

Balantidium coli in a fecal smear

Numerous trophozoitesin intestinal tissue

ApicomplexansApicomplexans

• Nonmotile

• Reproduce Asexually and Sexually

• Apical Complexes (Complex of Organelles)

Asexual Reproduction

Sexual Reproduction

ApicomplexansApicomplexans

Life CycleLife Cycle• Asexual reproduction (or schizogony) of the

Plasmodium occurs within liver cells and red blood cells of the infected human. With malaria caused by P. vivax and P. ovale, a dormant form or hypnozoite remains in the liver and may cause later relapses. The infected cells in which the organism is reproducing by schizogony are called schizonts. The sexual cycle (or sporogeny) occurs in the mosquito, the life cycle of Plasmodium). The typical recurring malarial fever is a result of the lysis of the infected red blood cells, causing release of merozoites and their metabolic by-products. Fever cycles of 24, 48, or 72 hours usually occur depending on the infecting species. Malaria is diagnosed by microscopically looking for the parasite within infected red blood cells (schizonts).

Plasmodium malariae infecting red blood cells. Four Plasmodium species, P. falciparum, P. malariae, P. ovale, and P. vivax cause malaria.

The vector involved in the transmission of the disease from human to human or from animal to human is an infected female Anopheles mosquito.

Plasmodium vivax infecting red blood cells

Malaria Kills More People Each Year than AIDS

Malaria affects 500 million people worldwide and kills at least 2 million per year. Over one million Africans die yearly (mostly children). 30,000 Europeans and North Americans are affected.

In fact, malaria, tuberculosis and Aids together killed more people in the last 50 years, than the combined death toll of all the wars during the

same time.

Young malaria patient nearAlem Kitmama North East of Addis-Ababa, Ethiopia, Africa

• Malaria is probably one of the oldest diseases known to mankind. Man and Malaria seem to have evolved together and it has been known to mankind for millennia. It was always part of the ups and downs of nations; of wars and of upheavals.

• Mentions of this disease can be found in the ancient Chinese, Indian and Egyptian manuscripts. The disease supposedly had its origins in the jungles of Africa, where it is still very much rampant. 

In 1880, Laveran, a French physician working in

Algeria, first identified the causative agent for human

malaria. He was awarded the Nobel

Prize in 1907.

On August 20th, 1897, Sir Ronald Ross, while working as a military physician in India, demonstrated

the malarial oocysts in the gut tissue of female Anopheles

mosquito, thus proving the fact that Anopheline mosquitoes were the vectors for malaria. That day is observed as Mosquito Day. He was awarded the Nobel Prize in

1902. (Ross never aspired to be a physician, he wanted to be a

writer. He only did so to please his father.

Toxoplasma gondiiToxoplasma gondii

• This protozoan causes the disease toxoplasmosis. In adults, the disease is usually mild and resembles infectious mononucleosis.

• However, new-born infants who contracted toxoplasmosis in utero commonly have severe central nervous system damage. It also causes severe disease in immunosuppressed individuals such as people with AIDS.

SymptomsSymptoms

• Fever • Sore throat • Sore muscles and tiredness • Swollen glands in the neck, armpits or groin • Temporary blurred vision or loss of vision • Most people who are infected do not show any

signs of the disease. • Persons who are pregnant or are experiencing a

suppressed immune system due to AIDS, cancer or following organ transplants are at higher risk for illness.

• Domestic cats, who pick up the organism from eating infected rodents, may act as carriers of T. gondii, and their feces may contain oocysts of the protozoan. However, the organism may be found in practically every mammal.

Toxoplasma gondii can also be contracted by eating raw or

undercooked meat. It infects 225,000 and kills 750, and is particularly dangerous to the unborn children of pregnant

women who become infected

Common ways for people to Common ways for people to become infected with toxoplasmosis become infected with toxoplasmosis

include:include:

• Eating raw or undercooked meats;

• Drinking unpasteurized milk;

• Cleaning cat litter boxes;

• Working in gardens or playing in sandboxes that contain cat feces.

                                     

                                     

Retinal Scar from Totoplasmosis

Brain Abscess

Sample Questionaire for Parents Sample Questionaire for Parents with Children with Toxoplamosiswith Children with Toxoplamosis

• http://www.ich.ucl.ac.uk/ich/html/academicunits/paed_epid/chad_3yrquestionnaire.pdf

CryptosporidiumCryptosporidium

Cryptosporidium is an intracellular parasite that causes diarrhea, although in people who are immunosuppressed it can also cause respiratory and gallbladder infections. It is transmitted by the fecal-oral route.

Cryptospordia oocyts in a stool sample.

The nation's largest outbreak -- classified as a water-borne outbreak -- struck 403,000 people in a five-county area around Milwaukee with cryptosporidiosis in 1993.

The disease is caused by the parasite cryptosporidium parvum.

Nearly a third of the residents became ill after public drinking water became contaminated.

Why Was There An Outbreak?

What Was the Solution?