Schistosomiasis Miracidia produces enzymes and secretions while in

Schistosomiasis • Miracidia produces enzymes and secretions while in the egg. • Ag/Ab reaction to miracidial secretions through egg, resulting in egg granuloma the Hoeppli phenomenon! Ag/Ab

How many eggs make it to the lumen? • 2/3 of those that enter tissue do not leave. • Many eggs do not enter tissue – Swept away in blood stream – Liver and spleen are first organs – Then Lungs – Other organs – Eggs look like Psuedotubercles 100, 000 eggs/gram!

Pathology and Symptoms 1. Migratory Phase • • • Penetration to Egg production Symptomless Dermal rash

Pathology and Symptoms 2. Acute Phase • • Egg Production Chills, fever, fatigue, headache, malaise Much exposure to antigens Granulomas surround eggs • • • Eosinophils, neutrophils, macrophages 1 -2 weeks fibroblasts enter granuloma Psuedotubercles-fibrous granulomas

Pathology and Symptoms 3. Chronic Phase • Asymptomatic • S. haematobium – Blood in the urine – Pain with urination – Loss of bladder function – Bladder cancer? – Eggs don’t metastasize?

Pathology and Symptoms 3. Chronic Phase • S. japonicum, S. mansoni – Mild, chronic dysentery – Abdominal pain – 8% infections develop liver fibrosis that impedes blood flow – Cirrhosis of liver • Long term problems – Hepatosplenomeagly • Long term: loss of tissue function

Ascites

Schistosoma japonicum • Anterior mesenteric veins • Small intestine • Interfere with absorption – Stunting • Eggs can go to brain – Smaller – Brain lesions 25 year old

Pathology • Adults cause no pathology – “hide” from immune system – Absorb host antigens • Pathology due to eggs

Diagnosis • Schistosoma mansoni and S. japonicum? • Schistosoma haematobium? • Small number of eggs • Serodiagnosis

Treatment • Praziquantel • Prognosis – Effective – Much of fibrosis can be reversed – Severe damage irreversible

Epidemiology • How do you get infected with a species of Schistosoma?

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

Work: Fisherman, agricultural workers, housework

Bathing and Play

Traditions • Ablution

How do eggs get into water supply?

What else do you need?

Snails • Schistosoma mansoni – Biomphilaria glabrata • Schistosoma japonicum – Oncomelania • Schistosoma heamatobium – Bulinus

Snail Habitat • • Any freshwater Eutrophic bodies of water Shallow areas near shore Associated with – Aquatic plants – Decaying organic debris

Seasonal Transmission • Transmission can occur only during certain seasons • Snail abundance • Dry season – Some species burrow into mud

Human Manipulations • Agricultural projects – Improve agriculture • Unintended consequences – Increase snail habitat – Zimbabwe: $10 million irrigation project abandoned – Aswan High Dam in Egypt

Aswan High Dam • Increased snail habitat • Increased Schistosomiasis – Below dam • Varied by significant increases • From 5%-35% – Above dam • From 5% in 1968 to 77% in 1993

Reservoir Hosts • Schistosoma haematobium – None known • Schistosoma mansoni – Many mammals: monkeys and rodents • Schistosoma japonicum – Least host specific – Many mammals

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

# 1 Control • • How do you get rid of snails? Remove by hand Molluscicide Biological control Eliminate habitat Do these work? Too many snails Molluscicides ineffective – Oncomelania • Biological control sometimes effective • People need water, too

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

#2 Control • How do you prevent eggs from contaminating water supplies? • Sewage treatment • Eliminate night soil • Education • Why doesn’t this work? • Expensive • Reservoir hosts

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

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

# 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!