Blood Fluke: Schistosome

By Chuah Candy, PhD Department of Medical Microbiology and Parasitology School of Medical Sciences Universiti Sains Malaysia Schistosomes We lead

• Commonly known as blood flukes.

• Parasitic - trematodes.

• Disease: .

• Affecting 200 million people across 74 countries.

• Human schistosomiasis is caused by 5 major types of schistosomes:  mansoni   Schistosoma haematobium  Schistosoma mekongi  Schistosoma intercalatum Global Distribution We lead

S. mansoni – Africa, Middle East & South America S. japonicum – China, Phillipines, Indonesia & Thailand S. haematobium – Africa, Middle East & India S. mekongi – Laos & Cambodia S. Intercalatum – Africa Gryseels et al., (2006) Lancet 368: 1106–18 Schistosomiasis in Malaysia We lead

S. japonicum infection

- 3.9% prevalence. - Areas of risk: Kapor river, Pahang. Orang Asli villages, Pos Iskandar and Bukit Lanjan, KL.

S. malayensis infection

- Infections in humans are unlikely and are considered rare. - Appears to be a zoonotic infection – infects rodents.

World Schistosomiasis Risk Chart 2012 Modes of Transmission We lead

• No direct person-to-person transmission.

• Transmission occurs when people suffering from schistosomiasis contaminate freshwater sources with their excreta (feces/urine) containing parasite eggs which hatch in water.

• People become infected when larval forms of the parasite penetrate the skin during contact with infested water. Life Cycle We lead Adult worms We lead

• Dioecious – Separate male and female. • Male worm is characteristically boat-shaped, with a central canal (gynaecophoric canal) in which the female worm lives. • Males have two suckers and a number of testes at the anterior end. • Females are longer but thinner compared to the males. • Females often have long uterus, with the ovary and vitelline tissues located at the middle or the posterior part of the body.

Female Female Adult worms We lead

MALE WORM FEMALE WORM Adult worms We lead

Esophageal gland Ventral sucker Oral FEMALE WORM sucker

Gut

Testis

Vitelline gland Ovary Gut

MALE WORM Adult worms We lead

Worm pair Adult worms We lead

Male worm Female worms Schistosome Eggs We lead

S. mansoni S. japonicum S. haematobium

. 114 to 180 µm long . 70 to 100 µm long . 110 to 170 µm long . 45-70 µm wide . 55-64 µm wide . 40-70 µm wide . Oval in shape . Round in shape . Oval in shape . Prominent lateral spine . Spine is smaller and . Spine at the terminal near posterior end less prominent end . 300 eggs per day . 3000 eggs per day . 30 eggs per day S. japonicum Egg & Miracidia We lead

Miracidia

Hatched egg

Miracidia Unhatched egg

Spine Intermediate Snail Host We lead

The intermediate snail host of schistosomes.

Left: Bulinus truncatus truncatus (S. haematobium) Middle: Biomphalaria glabrata (S. mansoni) Right: Oncomelania hupensis hupensis (S. japonicum) Cercariae We lead Cercariae Infection We lead Schistosomulae We lead

Day 1 Day 21 Clinical Presentation We lead

Acute Schistosomiasis Cercarial Dermatitis Katayama Fever • Hypersensitivity reaction on skin • Hypersensitivity reaction directed due to penetrating cercariae. against migrating schistosomulae. • Itchy urticarial rash on skin. • Developed symptoms between 14 • Developed within several hours of to 84 days post infection. exposure to cercariae- • Fever, cough, diarrhea, abdominal contaminated water. pain, hepatosplenomegaly etc. Clinical Presentation We lead

Chronic Schistosomiasis • Eggs deposited by female worms trapped in host organs (e.g. liver, intestine, lung & urinary bladder). • Symptoms may develop months or years after infection.

A) Hepatic schistosomiasis • Hepatic granulomas, fibrosis, portal hypertension, enlarged liver & spleen, bleeding of esophageal varices. • Commonly seen in S. mansoni, S. japonicum, S. mekongi & S. intercalatum infection.

Normal liver Acute liver Chronic liver Clinical Presentation We lead

Normal liver

lnfected liver Clinical Presentation We lead

Granuloma • A small area of inflammation in tissue produced in response to an infection, or the presence of a foreign substance. • Usually composed of multinucleated giant cells, lymphocytes, neutrophils, eosinophils, macrophages, fibroblasts and collagen.

S. japonicum granuloma S. mansoni granuloma Clinical Presentation We lead

B) Intestinal schistosomiasis • Intestinal granulomas, ulcerative colitis, abdominal pain, bloody diarrhea, blood in feces. • Commonly seen in S. mansoni, S. japonicum, S. mekongi & S. intercalatum infection.

C) Urinary schistosomiasis • Only in S. haematobium infection. • Accumulation of eggs in the wall of ureters, calcification of urinary bladder, blood in urine, bladder cancer, renal failure. Diagnosis We lead

 Microscopic identification of eggs in stool or urine - Simple to perform, low cost and fast - Increase sensitivity by the use off concentration techniques.

 Serologic assay – ELISA - Identification of parasite specific antigen-antibody complexes in the serum of infected individuals. - Able to detect low intensity infections.

 Tissue biopsy - Rectal biopsy for all schistosome species. - Bladder biopsy for S. haematobium. - Important when stool/urine examinations are negative. Classes of Intensity We lead

Light-intensity Moderate-intensity Heavy-intensity infections (epg) infections (epg) infections (epg) 1 – 99 epg 100 – 399 epg ≥ 400 epg

* epg – total number of eggs per gram of faeces

World Health Organization; 2002. Treatment We lead

• – most effective drug used to treat schistosomiasis.

• Effective against adult worms but ineffective against schistosomulae.

• Follow up examination at 1 to 2 months post-treatment is suggested to help confirm successful cure.

Schistosoma species infection Praziquantel dose and Duration , S. haematobium, 40 mg/kg per day orally in two divided S. intercalatum doses for one day 60 mg/kg per day orally in three divided S. japonicum, S. mekongi doses for one day Prevention We lead

• No vaccine is available.

• Avoid swimming in freshwater when you are in countries in which schistosomiasis occurs.

• Drink safe water.

• Water used for bathing should be brought to a rolling boil for 1 minute to kill any cercariae.

• Those who have had contact with potentially contaminated water overseas should see their health care provider after returning from travel to discuss testing. Control We lead

• Mass drug treatment of entire communities and targeted treatment of school-age children

• Eliminate the snails that are required to maintain the parasite’s life cycle.

• Improved sanitation could reduce or eliminate transmission of this disease.

• Health education – young schoolschildren. Thank you