2Why is this important to us? Parasites in the U.S.Toxocariasis now a common parasitic infection among inner city childrenCysticercosis, caused by the tapeworm Taenia solium, is emerging as the leading cause of epilepsy among Hispanic populations in the USToxoplasmosis is an important cause of congenital birth defects"Poverty and Neglected Diseases in the Other America", Professor Peter Hotez (George Washington University and the Sabin Vaccine Institute)
3Why is this important to us? “The problem is that, due to a lack of education, most of the population doesn’t know that there’s a parasite wriggling within them,” says Patricia Wilkins, a scientist with the Center for Disease Control and Prevention (CDC)
4Parasites outside the U.S. Why is this important to us?Parasites outside the U.S.
7What are parasites?Symbiosis: close and often long-term interaction between two or more different biological speciesMutualism - both individuals benefitCommensalism - one benefits, the other is not significantly harmed or helpedParasitism - one benefits, the other is harmed
8Life cycles Many parasites discussed today are protozoa Some protozoa have life stages alternating between stagesTrophozoites – actively feedingCysts – can survive harsh conditions or long periods without access to nutrients, water or oxygen for extended period of timeEncystationExcystation
9Entameoba histolytica Anaerobic parasitic protozoanEstimated to infect 50 million people worldwide40,000 to 100,000 people worldwide die annually90% asymptomatic"Amebiasis". NEJM. United States NEJM: Massachusetts Medical Society Retrieved
10Entameoba histolytica Life cycleFecal/oral routeAnal/oral route
11Entameoba histolytica histo–lytic = tissue destroyingAmeobiasisSymptoms take from a few days to a few weeks to develop and manifest themselvesMild diarrhea to dysentery with blood and mucus (lining of intestine)About 10% of invasive cases the amoebae enter the bloodstreamMay travel to other organs in the body (liver)
12Entameoba histolytica Diagnosis: stool sampleTreatmentMetronidazole highly effective against trophozoitesParamoycin for cysts in lumenNeed both
13Entameoba histolytica What is most important about Entameoba histolytica?
14Giardia lamblia Flagellated protozoan parasite Anaeorobes From the CDC:“Giardiasis is a global disease. It infects nearly 2% of adults and 6% to 8% of children in developed countries worldwide. Nearly 33% of people in developing countries have had giardiasis. In the United States, Giardia infection is the most common intestinal parasitic disease affecting humans”
15Giardia lamblia Fecal-oral route Noninfective cyst excreted from feces of infectived individualOnce ingested by a host, trophozoite emerges to an active state of feeding and motilityAfter feeding, trophozoite undergoes binary fission
16Giardia lamblia Giardiasis Colonization of gut results in inflammation and atrophy, reducing gut’s absorptive capabilityDiarrhea, malaise, excessive gas, epigastric pain, bloating, nausea, diminished interest in food
17Giardia lambliaAccurate diagnosis requires an antigen test or, if that is unavailable, an ova and parasite examination of stool.Multiple stool examinations are recommended, since the cysts and trophozoites are not shed consistently.Given the difficult nature of testing to find the infection, including many false negatives, some patients should be treated based on symptoms.Treatment: Metronidazole
18Giardia lamblia Waterborne sources Day- care centers Untreated sewageCysts resistant to conventional water treatment methods including chlorinationDay- care centersGiardia is also one of the most common parasites infecting cats, dogs and birds. Mammalian hosts also include cattle, beavers, deer, and sheep
19Giardia lambliaWhat is most important about Giardia lamblia?
20MalariaRegion: Most Prevalent in Tropical Regions, but is present in the U.S.Caused by the plasmodium species of protozoaOf the 200 plasmodium varieties, 11 effect humans.4 of the plasmodium varieties induce MalariaPlasmodium is carried by the Anopheles species of mosquito.Over 216 million NEW infections are estimated to occur every yearOver 600,000 malaria related deaths occur annually.
21Malaria - Infection of the Mosquito Many Anopheles mosquitos in afflicted regions are born infected.Can become exposed by eating the blood of an infected organismPlasmodium travels through the blood stream to the stomachHost OrganismGametesTravels to the salivary glands until the mosquito’s next meal
22Malaria – Infection of Humans Starts with the Mosquito BiteEnters the blood through salivary secretionsSporozoite phase travels to the liverMaturation MerozoitesProliferationRupture the Infected Hepatocyte,reentering the blood streamEnter Erythrocytes (red blood cells)Feed on hemoglobin, releasing toxicheme byproductProliferation: hour cyclesRupture of the Erythrocyte
24Malaria - Symptoms Develop 10-28 Days After Infection Most Common Symptoms IncludeFeverChillsJaundiceEnlarged Liver and Spleen*Symptoms occur in hour cycles. Why?If left untreated…Renal, Liver, Respiratory FailureLiver and Spleen RuptureMeningitisCerebritis
25Malaria – Diagnosis and Treatment Physical Exam – Enlarged Liver and SpleenBlood Test (CBC) – AnemiaBlood Smear – Look for the parasiteTreatment: Chloroquine (antimalarial drug)Prevents plasmodium metabolismMust begin while liver is functionalChloroquine Resistant Strains Exist,Quinidine (antiarrhythmic)Doxycycline (antibiotic)Prognosis: Good
26Malaria – Sickle Cell Anemia Heterozygous-recessive traitHomozygous: Shortened life expectancyOffers the “heterozygous advantage”Leads to “sickling” of erythrocytesDue to inability to crystallize hemoglobinReduces O2 Binding CapacityReduces flexibility of erythrocyteClottingBlood Vessel OcclusionPrevents Plasmodium from enteringand/or proliferatingMechanism is not certainReduced O2 availabilityDestroys Plasmodium membranes
27Trichomonas Vaginalis Region:Present WorldwideMost common parasitic infection in U.S.Estimated 3.7 million new cases annuallySpecies:Trichomonas vaginalisHumans are the only known vectorsDo not have a cystic formMust be transmitted by direct contact
28Trichomonas Vaginalis - Infection Generally Sexually AcquiredToiletsOther Items that Contact Genitals“Stuck” in the trophozoite phaseGrow flagella during developmentProliferate via binary fissionInhabit genitaliaLive in urogenital epitheliumFeeds on:Bacteria PhagocytosisVaginal Secretions
29Trichomonas Vaginalis – Symptoms Only 30% of Infected persons show any symptomsMore common in females5-28 DaysMen:Itching/Irritation of PenisBurning SensationDischargeWomen:“Strawberry Cervix” (2%)Itching, Burning, Redness, Soreness of GenitalsDiscomfort during UrinationOdorous yellow-green discharge (12%)
30Trichomonas Vaginalis – Diagnosis and Treatment Physical Exam: Nearly ImpossibleLaboratory: Microscopic Observation of DischargeVery Low SensitivityTreatment:Metronidazole (antibiotic)One large (2 gram) dosePasses through mucous membrane into protozoaResistant Strains ExistTreatment is a ChallengePrognosis:Most commonly cured STI95%
31Ascariasis Ascariasis = Infection by parasitic nematode Ascaris lumbricoidesRegion: Present Worldwide, most common insub-tropical, developing nations Human Feces used as FertilizerEstimated: 1 billion infections worldwide,4 million infected AmericansAscariasis: “Long Intestinal Roundworm”Cylindrical2-6 mm in diameter,15-35 cm (7-15 inches) long
32Ascariasis - Infection In the soil – 18 days to become infectious, can survive for 10 years.Eggs pass to humans by direct contactEggs travel to the small intestine, hatch after 2 weeks.Enter blood circulation LungsMature in Lungs for ~1 week, then reenter the intestines.Fully develop in the intestines, differentiating into adult males and femalesSexually reproduce, up to 200,000 eggs/day2-3 Months Total
33Ascariasis - Symptoms Many People Show No Symptoms! Lung Phase: Ascaris PneumonitisCoughingWheezingShortness of BreathCannot be diagnosedIntestinal PhaseVague to Severe Abdominal PainNausea and VomitingWeight loss/malnutritionDiarrhea and Bloody StoolComplicationsGall bladder obstruction Gall stonesIntestinal Blockage and PerforationPancreatitis
34Ascariasis – Diagnosis and Treatment Diagnostic ToolsMicroscopic Study of the Stool40 daysCBC – Eosinophilia increaseNot specificAbdominal CT or X-RayEndoscopyTreatment OptionsUntreated Infections will often resolveTwo classes of medical treatment options: Antihelminthic drugsBoth lead to worm passage in fecesMebendazole (500mg): Kills wormsLevamisole (2.5mg/kg): Paralyzes worms
35Pinworms- Enterobius vermicularis in AmericaRegion :Worldwide, most common helminth infection in the U.S. and Western Europe.11.4% (~40 million) in the U.S. are infectedMost common in children50% in EnglandSpecies:1 of 3 types of parasitic pinworms, the only one that affects humansHumans are the only known hostSmall (13x0.5 mm), white, and delicateFemales have a sharp rear endEggs are microscopic
36Pinworms - Infection Eggs spread by touch Mouth (inhalation or ingestion)AnusInfected persons often carry eggs beneath fingernailsEggs are extremely hardyCan survive on inanimate surfaces for up to 3 weeksTowelsCurtainsToysFurniture
37Pinworms – Life Cycle Takes place in a single host After ingestion, eggs hatch in the duodenumLarvae grow and move towards colonDevelop into adultMating occurs in the cecumMales die after matingFemales attach to the ascending colon, feeding on colic contentsProduce eggsTravel through large intestineEmerges from anus to lay eggsSpread by contactRetroinfection
38Pinworms – Symptoms Causes enterobiasis -Often asymptomatic Itching in the anal regionEspecially at nightInsomniaAnorexiaWeight LossIrritabilitySecondary Issues:VulvovaginitisUrinary Tract InfectionBacterial Infections
39Pinworms – Diagnosis and Treatment Diagnostic Tools“Scotch Tape Test”90% SensitivityVisual ObservationAnal SwabsTreatmentBenzimidazole or Mebendazole (antiparasitic)Target adult wormsPrevents glycogen storage, leads to starvationHygiene!!Prevents reinfectionIvermectin for urogenital migrationBroad Spectrum antiparasitic
40Naegleria fowleri “The brain-eating amoeba” Region: Incredibly rare, but found most commonly in the U.SBetween , 32 casesFound in warm, fresh bodies of water, soil near such locations, and unchlorinated swimming pools2 Deaths from Neti Pot UseSpecies:Sensitive single-celled amoebaThermophileCannot survive in salty environmentsHas 3 stages to its life cycle:Cyst Stage: Present in unfavorable conditions, inactiveTrophozoite: The “active” phase, it proliferates by binary fission. They feed on bacteria.Flagellate: Can change rapidly back and forth to trophozoite phase, motile.
41Naegleria fowleri - Infection The trophozoite is the infectious formGets introduced through the noseEmbeds in the nasal epitheliumAttracted to the neurotransmitters of Olfactory nerve“Eat” the olfactory nerve and bulb, back to the cerebrum.Spread to the rest of the brain
42Naegleria fowleri - Symptoms Causes by Primary Amoebic Meningoencephalitis (PAM)Symptoms take ~5 days to present, at which time it is often too late for treatment.Death occurs 3-7 days after first symptomsSymptoms: Common with other encephalitic conditionsNauseaVomitingHeadacheStiff NeckDeliriumSeizuresComplications:ComaRespiratory Arrest
43Naegleria fowleri – Diagnosis and Treatment Diagnostic ToolsLumbar PunctureAnalysis of CSFIndicated for by Symptoms“Treatment”“Heroic” dose of Amphotericin B (systematic antifungal)Miltefosine and FluconazoleNot FDA ApprovedTesting on Phenothiazine Antipsychotic ChlorpromazinePrognosis: 2-3% survival rate