Schistosomiasis Miracidia produces enzymes and secretions while in the egg.Miracidia produces enzymes and secretions while in the egg. Ag/Ab reaction to.

SchistosomiasisSchistosomiasis

• Miracidia produces Miracidia produces enzymes and enzymes and secretions while in the secretions while in the egg.egg.

• Ag/Ab reaction to Ag/Ab reaction to miracidial secretions miracidial secretions through egg, resulting through egg, resulting in egg granuloma the in egg granuloma the Hoeppli phenomenon!Hoeppli phenomenon!

Ag/Ab

How many eggs make it to the lumen?How many eggs make it to the lumen?

• 2/3 of those that enter tissue do not leave.2/3 of those that enter tissue do not leave.

• Many eggs do not enter tissueMany eggs do not enter tissue– Swept away in blood streamSwept away in blood stream– Liver and spleen are first organsLiver and spleen are first organs– Then LungsThen Lungs– Other organsOther organs– Eggs look like Eggs look like

PsuedotuberclesPsuedotubercles

100, 000 eggs/gram! 100, 000 eggs/gram!

1.1. Migratory PhaseMigratory Phase• Penetration to Egg productionPenetration to Egg production• SymptomlessSymptomless• Dermal rash Dermal rash

Pathology and SymptomsPathology and Symptoms

2. Acute Phase2. Acute Phase• Egg Production Egg Production • Chills, fever, fatigue, Chills, fever, fatigue,

headache, malaise headache, malaise • Much exposure to antigensMuch exposure to antigens• Granulomas surround eggsGranulomas surround eggs• Eosinophils, neutrophils, Eosinophils, neutrophils,

macrophagesmacrophages

• 1-2 weeks fibroblasts enter 1-2 weeks fibroblasts enter granulomagranuloma

• Psuedotubercles-fibrous Psuedotubercles-fibrous granulomasgranulomas

Pathology and SymptomsPathology and Symptoms

Pathology and SymptomsPathology and Symptoms3. Chronic Phase3. Chronic Phase

• Asymptomatic Asymptomatic

• S. haematobiumS. haematobium– Blood in the urineBlood in the urine– Pain with urinationPain with urination– Loss of bladder functionLoss of bladder function– Bladder cancer?Bladder cancer?– Eggs don’t metastasize?Eggs don’t metastasize?

Pathology and SymptomsPathology and Symptoms3. Chronic Phase3. Chronic Phase

• S. japonicum, S. mansoniS. japonicum, S. mansoni– Mild, chronic dysenteryMild, chronic dysentery– Abdominal painAbdominal pain– 8% infections develop liver fibrosis that 8% infections develop liver fibrosis that

impedes blood flowimpedes blood flow– Cirrhosis of liverCirrhosis of liver• Long term problemsLong term problems

– HepatosplenomeaglyHepatosplenomeagly

• Long term: loss of tissue functionLong term: loss of tissue function

AscitesAscites

Schistosoma japonicumSchistosoma japonicum

• Anterior mesenteric veinsAnterior mesenteric veins

• Small intestineSmall intestine

• Interfere with absorptionInterfere with absorption– StuntingStunting

• Eggs can go to brainEggs can go to brain– SmallerSmaller– Brain lesionsBrain lesions

25 year old

PathologyPathology

• Adults cause no Adults cause no pathologypathology– ““hide” from hide” from

immune systemimmune system– Absorb host Absorb host

antigens antigens

• Pathology due to Pathology due to eggseggs

DiagnosisDiagnosis

• Schistosoma mansoniSchistosoma mansoni and and S. japonicumS. japonicum??

• Schistosoma haematobiumSchistosoma haematobium??

• Small number of eggsSmall number of eggs

• SerodiagnosisSerodiagnosis

TreatmentTreatment

• PraziquantelPraziquantel

• PrognosisPrognosis

– EffectiveEffective

–Much of fibrosis can be reversedMuch of fibrosis can be reversed

– Severe damage irreversibleSevere damage irreversible

EpidemiologyEpidemiology

• How do you get infected with a species of How do you get infected with a species of SchistosomaSchistosoma??

EpidemiologyEpidemiology

• What causes people to come into contact What causes people to come into contact with water?with water?

Work: Work: Fisherman, agricultural workers, houseworkFisherman, agricultural workers, housework

Bathing and PlayBathing and Play

TraditionsTraditions

• AblutionAblution

How do eggs get into water supply?How do eggs get into water supply?

What else do you need?What else do you need?

SnailsSnails

• Schistosoma mansoniSchistosoma mansoni– Biomphilaria glabrataBiomphilaria glabrata

• Schistosoma japonicumSchistosoma japonicum– OncomelaniaOncomelania

• Schistosoma heamatobiumSchistosoma heamatobium– BulinusBulinus

Snail HabitatSnail Habitat

• Any freshwaterAny freshwater

• Eutrophic bodies of waterEutrophic bodies of water

• Shallow areas near shoreShallow areas near shore

• Associated withAssociated with– Aquatic plantsAquatic plants– Decaying organic debrisDecaying organic debris

• Transmission can occur only during certain Transmission can occur only during certain seasonsseasons

• Snail abundanceSnail abundance

• Dry seasonDry season– Some species burrow into mudSome species burrow into mud

Seasonal TransmissionSeasonal Transmission

Human ManipulationsHuman Manipulations

• Agricultural projectsAgricultural projects– Improve agricultureImprove agriculture

• Unintended consequencesUnintended consequences– Increase snail habitatIncrease snail habitat– Zimbabwe: $10 million irrigation project Zimbabwe: $10 million irrigation project

abandonedabandoned– Aswan High Dam in EgyptAswan High Dam in Egypt

Aswan High DamAswan High Dam• Increased snail habitatIncreased snail habitat

• Increased SchistosomiasisIncreased Schistosomiasis – Below damBelow dam

• Varied by significant increasesVaried by significant increases

• From 5%-35%From 5%-35%

– Above damAbove dam• From 5% in 1968 to 77% in 1993From 5% in 1968 to 77% in 1993

Reservoir HostsReservoir Hosts

• Schistosoma haematobiumSchistosoma haematobium– None knownNone known

• Schistosoma mansoniSchistosoma mansoni– Many mammals: monkeys and Many mammals: monkeys and

rodentsrodents

• Schistosoma japonicumSchistosoma japonicum– Least host specificLeast host specific– Many mammals Many mammals

ControlControl

Infected People

Uninfected People

contact contact

Season

Habitat Behavior

Sewage

Occupation

Behavior

Bathing

# 1 Control# 1 Control• How do you get rid of snails?How do you get rid of snails?• Remove by handRemove by hand• MolluscicideMolluscicide• Biological controlBiological control• Eliminate habitatEliminate habitat• Do these work?Do these work?• Too many snailsToo many snails• Molluscicides ineffectiveMolluscicides ineffective– OncomelaniaOncomelania

• Biological control sometimes effectiveBiological control sometimes effective• People need water, tooPeople need water, too

ControlControl

Infected People

Uninfected People

contact contact

Season

Habitat Behavior

Sewage

Occupation

Behavior

Bathing

#2 Control#2 Control

• How do you prevent eggs from How do you prevent eggs from contaminating water supplies?contaminating water supplies?

• Sewage treatmentSewage treatment

• Eliminate night soilEliminate night soil

• EducationEducation

• Why doesn’t this work?Why doesn’t this work?

• ExpensiveExpensive

• Reservoir hostsReservoir hosts

ControlControl

Infected People

Uninfected People

contact contact

Season

Habitat Behavior

Sewage

Occupation

Behavior

Bathing

# 3 Control# 3 Control• How do you prevent people from How do you prevent people from

contacting cercariae?contacting cercariae?• EducationEducation• Protective gear (waders, boots)Protective gear (waders, boots)• Provide non-contaminated waterProvide non-contaminated water• VaccinesVaccines• Why don’t these methods work?Why don’t these methods work?• People need waterPeople need water• Fishermen, Agricultural workers can’t Fishermen, Agricultural workers can’t

avoidavoid– 60% world calories from rice60% world calories from rice

• Protective gear hot and cumbersomeProtective gear hot and cumbersome• AblutionAblution• Cost of clean waterCost of clean water• Vaccines unsuccessfulVaccines unsuccessful

ControlControl

Infected People

Uninfected People

contact contact

Season

Habitat Behavior

Sewage

Occupation

Behavior

Bathing

# 4 Control# 4 Control

• How can you eliminate the parasite?How can you eliminate the parasite?

• Drug treatmentDrug treatment

• Genetically modified snailsGenetically modified snails

• Do these work?Do these work?

• Cost Cost – Dose of praziquantel = $0.20Dose of praziquantel = $0.20

• No genetically modified snails yetNo genetically modified snails yet

Cercarial Dermatitis/ Swimmer’s ItchCercarial Dermatitis/ Swimmer’s Itch

• 10 species (U.S.)10 species (U.S.)

Trichobilharzia sp.

Matt’s leg with cercarial dermatitis or “swimmers’s itch” caused by cercariae of avian blood flukes.

Furcocercous cercariae diagnostic for Schistosomes.

Cercarial Dermatitis/ Swimmer’s ItchCercarial Dermatitis/ Swimmer’s Itch

• Inflammatory Inflammatory responseresponse

• Pus-filled pimplesPus-filled pimples

• Itching and painItching and pain

• 4 days4 days

DendritobilharziaDendritobilharzia spp. spp.

• Live in the dorsal aorta of ducks!Live in the dorsal aorta of ducks!

Ducks can infect snails that can infect Ducks can infect snails that can infect swans! swans!

Eggs can enter CNS via arterial Eggs can enter CNS via arterial circulation causing CNS disease!circulation causing CNS disease!