Blood Flukes (Schistosomes) Infect mammals, and birds. Live in the mesenteric veins (most species); some in urinary plexus veins, nasal veins, and dorsal aorta.

Blood Flukes Veins Mesenteric veins Anterior (superior) Small intestine Posterior (inferior) Large intestine Urinary bladder

Schistosoma Small elongate 1-2 cm Dioecious Gynecophoric canal Male helps female eat

Schistosomiasis Major Parasitic disease, with 200-300 million people infected. many are school age children

Schistosomiasis Schistosoma Bilharzia Egyptian papyri Egyptian mummies 1850 Theodor Bilharz Egyptian papyri Egyptian mummies Joshua’s curse on Jericho 1800 Napoleon’s army

Species that infect humans Schistosoma japonicum Anterior mesenteric veins Schistosoma mansoni Posterior mesenteric veins Schistosoma haematobium Veins draining the urinary bladder Schistosoma intercalatum Intestinal schistosomiasis in Africa Schistosoma mekongi Small intestine like S. japonicum (Vietnam)

} Species Schistosoma japonicum Schistosoma mansoni Big three! Anterior mesenteric veins Schistosoma mansoni Posterior mesenteric veins Schistosoma haematobium Veins draining the urinary bladder Schistosoma intercalatum Intestinal schistosomiasis in Africa Schistosoma mekongi Small intestine like S. japonicum (Vietnam) Big three!

Schistosomiasis Estimates 1947: 114,000,000 1968: 118,000,000 1972: 125,000,000 1979: 200,000,000 Current: More than 200,000,000

Why the Increase? Due to irrigation farming and building of dams to facilitate irrigation. Snail habitat has expanded and increases exposure to people.

Life Cycle Schistosomes live in blood vessels that drain tissues such as the bladder, S. intestine and L. intestine. They produce eggs within blood vessels!

Eggs have spines, no operculum, also have prominent secretory glands! S. mansoni S. japonicum S. haematobium

Eggs Eggs are shed to outside through excrement (feces or urine).

Chemical Signaling with arginine Life Cycle Chemical Signaling with arginine Adults can live 20-30 years 3 weeks Release Eggs in 5-8 Weeks

Distribution

Distribution

How do the eggs get out of the body?

How do the eggs get out of the body? Female worm leaves the male and migrates down to lay eggs.

How do the eggs get out of the body? Female worm leaves the male and migrates down to lay eggs. Egg spines help the eggs work their way into the tissue, but the miracidia also produces enzymes.

Granuloma can move with the eggs by peristaltic action. Immune response Granuloma (Eosinophils, macrophages, neutrophils) Granuloma can move with the eggs by peristaltic action.

Schistosomiasis Big picture the key to schisto pathology is the eggs not the adult worms!

# 3 Control How do you prevent people from contacting cercariae? Education Protective gear (waders, boots) Provide non-contaminated water Vaccines Why don’t these methods work? People need water Fishermen, Agricultural workers can’t avoid 60% world calories from rice Protective gear hot and cumbersome Ablution Cost of clean water Vaccines unsuccessful

Control Infected People Uninfected People Occupation Behavior Habitat Sewage Occupation Behavior Bathing Season Habitat Infected People contact Uninfected People contact

# 4 Control How can you eliminate the parasite? Drug treatment Genetically modified snails Do these work? Cost Dose of praziquantel = $0.20 No genetically modified snails yet

Cercarial Dermatitis/ Swimmer’s Itch 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 Itch Inflammatory response Pus-filled pimples Itching and pain 4 days

Dendritobilharzia spp. Live in the dorsal aorta of ducks!

Ducks can infect snails that can infect swans!

Eggs can enter CNS via arterial circulation causing CNS disease!