Protozoan & Helminth diseases

• Parasitic infections• Medically and

economically important

• Changing world climate may alter transmission patterns

Protozoan parasites

• Unicellular parasites• Via ingestion• Trophozoite: feeding

and reproducing stage• Cyst: dormant stage• Excystment• Encystment

Amoebae• Use pseudopodia• Entamoeba histolytica• World wide mortality of

100,000• Water contaminated with feces• Three types:• amebic dysentary• Extraintestinal• Use stool samples• Paromomycin: protein synthesis

MalariaPlasmodium species - non-motile protozoa

Pathogenesis - Acute or ChronicTropical Anopheles mosquitoes, bite-acquired1-2 weeks - red blood and liver cells, anemia1-2 years - cyclic fever, headache, anemiaPossible lung, brain, and/or liver complications

Prevention and Control90% cases in Africa - 4 million deaths/yearUS (1000-2000 per year) airport-associatedAntimalarial drugs - quinine, doxycyclineDrug-resistance emerging throughout the worldSigns of early vaccine 2004 - VERY premature

American TrypanosomiasisTrypanosoma cruzi - Chagas -

Pathogenesis - Acute or ChronicReduviid assassin bugs, blood transfusionsHealthy - mild (fever or asymptomatic)Unhealthy– GI tract, cardiac damage

Prevention and ControlEndemic - North, South, and Central AmericaMexico - 16-18 million infected, 40,000 die/yearAnti-protozoal drugs - NO US blood screened

Trypanosoma brucei• Tsetse fly (Glossina)• Reservoir: cattle and

sheep• Untreated: dead tissue at

bite• Presence in blood triggers

fever• Invade CNS• Months to years to

develop• Changes surface

glycoproteins

ToxoplasmosisToxoplasma gondii - a non-motile protozoa

Pathogenesis - AcuteCarried in cats, birds, rodents, passed in fecesInhaled, eaten, transfusion/transplant, scratchesHealthy - flu-like, but FATAL to fetusUnhealthy - potential fatal CNS

Prevention and ControlAvoid carriers; anti-protozoal drugs

Trichomoniasis VaginitisTrichomonas vaginilis - flagellate protozoa

Pathogenesis - AcuteFemales - yellow and stinky dischargeCan pass to males and cause urethritis33% vaginitis is “trich” (others bacterial, fungal)

Helminthic parasites

• Multicellular eukaryotic worms• Usually need an intermediate host for the larval

stage

Cestodes

• Tapeworm• Proglottid (1000-

2000) contain 100,000 eggs

• Abdominal pain, weight loss

Schistosoma

• Blood flukes• 200 million people

worldwide infected• 20,000 die annually• Burrow through the

skin

Wucheria

• Nematode• Lymphatic system• Can be asymptomatic• Swim at night in blood stream• Elephantiasis

Arthropod vectors --Lyme DiseaseBorrelia burgdorferi - Spirochete bacteria

Pathogenesis - Acute then Chronic4-7 days - bulls-eye lesion after deer tick biteWeeks to months - fever, chills, head/joint acheUntreated - cardiac, neurological complications

Prevention and ControlLyme, CT in 1975; now 15,000 US cases/yearEffective vaccine and antibiotics EARLY