PROTOZOAFirst Animal

Parasite

• Lives at expense of host

• Ectoparasites– Ticks & lice

• Endoparasites– Protozoan & worms

Characteristics of Protozoa

• Unicellular eukaryotes

• Key part of food chain

• Most free living, decomposers especially sewage

Characteristics of Protozoa

• Some commensals- no harm– Guts of termites, roaches, ruminants

• Some parasites

• Most motile by cilia, flagella or pseudopodia

Morphology

• Diverse• Lack rigid cellulose cell wall

– Pellicle or membrane

• Trophozoite

Morphology

• Many have resting stage-cyst

– Not reproductive structure

– Intestinal bugs pass host to host

Reproduction• Asexual

– Fission, budding– Schizogony

• Sexual– Gametes

– Oocyst-Apicomplexa

Nutrition

• Aerobic, mostly chemoheterotrophic (engulf food)

• One group is photoautotrophic

• Some anaerobic growth; live in intestine

• Some transport food across membrane

Nutrition

• Some ingest food

• Ciliates have cytostome

•

• Amoebae engulf food via pseudopods

• Digestion takes place in vacuoles- (lysosomes), waste through PM or anal pore

Virulence factors

• Waste products (toxins) produce disease-malaria

• Hide from immune system

• Some grow inside phagocytes

• Some change antigens

Archaezoa

• Lack mitochondria

• Evolved before endosymbiotic event or lost ability to produce mitochondria

Archaezoa

• Many live as symbionts

• Trophozoite– Spindle shaped with 2 or more flagella

Trichomonas vaginalis

• Vagina and male urinary tract( asymptomatic)

• No cyst form – needs to be transferred before drying

• Transmitted via sex , toilet facilities or towels(moist)

Trichomonas vaginalis

• Environmental changes DT abxs, DM, or IUD-infection

• S&S increase in WBCs

• Prevention-abstinence, monogomy, condoms

Giardia lamblia

• Tophozoite– Excreted in feces as cysts

• Survives in environment long time

• Ingested by host or transferred during anal intercourse

• Cyst resistant to chlorine & stomach acid

Giardia

• Metronidazole, flagyl used for anaerobes damages DNA

• Diapers in day care

• Enterotest capsule-gelatin with string

Amoebozoa

• Amoebas– Pseudopodia for phagocytosis

• Entamoeba histolytica ( tissue lysing)- amoebic dysentery (Blood in stools)

• Trophozoites in small intestine -food is RBCs

• Cysts excreted in feces of infected person-MSM

Entamoeba histolytica

• Forms ulcers by digesting wall of large intestine

• Can enter blood stream

• Infect other organs of body

Apicomplexa

• Nonmotile in mature forms

• All are parasitic– obligate intracellular parasite

• Presence of a complex of special organelles at tips of cells

• Oocysts are reproductive

Plasmodium

• Causes malaria• Characterized by shaking chills,feve &

sweats

• Symptoms occur at regular intervals-2 to 3 days– ID species

• Vector is Anopheles mosquito

Plasmodium

• P vivax, one of 4 species- most prevalent species but benign

•  Sexual reproduction in gut

  Infective sporozoites in saliva

    Life Cycle

Transmit to humans (bite) and 100s go to liver where schizogony occurs –merozoites

  Enter RBCs where develop into ring stage

Life Cycle

  Multiply, forms merozoites and burst

  Some merozoites develop into gametes

• Enter gut of mosquito

• Forms oocyst in wall of intestine– Cell division forms sporozoites and migrate to

salivary glands

Life Cycle

• Definitive host is mosquito-sexual cycle• Intermediate host -human- asexual cycle• Diagnosis by blood smear and interval of

symptoms– .

• Regulated by host’s body temperature

P. falciparum

• Most dangerous; “malignant malaria– Black water fever

• Untreated malignant kills 50% of infected persons• Suppressed immune system and caused severe

anemia• RBCs stick to capillaries causing blockage

– tissue death -liver ,kidney and brain

Treatment

• Treatment is chloroquine for early stages

• Primaquine for late stages

• Resistance has developed

Immunity

• If survive malaria , have limited immunity

• Sickle cell trait persons are relatively resistant to malaria– RBCs sickle under low oxygen tension– Microbe can’t survive

Control Program

• Need an effective program • Increase in world population• Increase in warming• Increase in resistant Plasmodium strains• Increase in mosquito resistance to

insecticides• Different stages of life cycle require

different medications

Toxoplasmosis

• Agent Toxoplasma gondii

• Definitive host -cat,

• Oocyst shed in feces

• Form trophozoites-tachyzoites(fast)

• Multiply in host tissues-all cells except RBCs

• Intracellular parasite ruptures cells

Signs & Symptoms

• Fever, malaise, sore throat, swelling of lymph nodes

• Immune system contains disease-chronic infection

• Tissue cyst forms containing bradyzoites • Reactivate later when immune system

breaks down• Can form lesions on eyes or any other organ

Life Cycle

• Humans ingest undercooked meat or contact with cat feces- contain oocysts

• Trophozoites released and feed on bacteria and fecal material

• Most have mild symptoms unless immunocompromised

Infection

• Congenital infections result in brain damage or vision problems in fetus

  AIDS -severe eye damage from reactivation of cysts

Euglenozoa

• 2 groups – Hemoflagellates-blood parasites

• Transmitted by bites of insects and found in circulatory system

• Trypanosomiasis- 2 species of Trypanosoma– One causes a wasting disease: other acute, rapid

progression to coma & death

  African Sleeping Sickness

• Affects nervous system, encephalitis• Multiples by fission inside of insect• Vector tsetse fly (salivary glands), reservoir is game

animals• Infects human when defecates during biting

– Forms painful chancre (syphilis)

• Pathogen in blood then goes to liver, lymph nodes & CSF

• Decrease in mental acuity and physical activity; untreated coma and death

Virulence Factor

• Evades immune system-changes antigens• Coincides with increase in parasites in

blood• Continues till death or effective treatment• > 1000 genes coding for different antigens

on surface• Few antiprotozoan drugs for treatment

– Toxic

Ciliophora

• Ciliates, most are free living• Arranged in precise rows on cell• Move in unison to propel organism and to push

food toward mouth• Balantidium coli-only human pathogen in this

group– causes rare dysentery– reservoir is usually pigs

• Cause ulcer to form in colon when trophozoites burrow into colon