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Jenny Loconsole

on 10 April 2013

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Transcript of Schistosomiasis

By Dominic Lucero, Julie Miller and Jenny Loconsole Schistosomiasis Agent: Schistosoma genus Parasitic blood fluke
Infection through water contact
Infects blood vessels of the digestive tract, bladder, liver and lungs
Intermediate host: snails
Reservoirs: dogs, cats, cattle, horses, pigs Symptoms Life Cycle Agent References Treatment Praziquantel
Antihelmintic - causes paralysis in worms
Multiple doses taken over one day
Treats infections caused by all Schistosoma
Effective, safe, low-cost
Dose based on estimation of worm-load
For S. Mansoni, S. haematobium, S. intercalatum: dose is 40 mg/kg twice
For S. japonicum, S. mekongi: dose is 60 mg/kg twice Diagnosis Control and Prevention Webber, R. (2009). Communicable disease epidemiology and control (Third ed.)


BIOS-41415-01 Parasitology Lecture


http://www.nhs.uk/Conditions/schistosomiasis/Pages/Symptoms.aspx Tests run on stool/urine samples to determine presence of microscopic eggs
Stool for S. mansoni or S. japonicum and urine for S. haematobium eggs
The production of more than 50 egg/ml of urine indicates a severe level of pathology for S. haematobium
Other tests a doctor may run include: antibody test, biopsy of tissue, complete blood count, eosinophil count, kidney/liver function tests
IFAT and ELISA -- immunological methods developed but only indicate recent or past infection, so eggs must be found for confirmation BIOS-41415-01 Parasitology Lecture Symptoms of schistosomiasis are caused by the eggs, not the worms themselves
Incubation period: 2 - 6 weeks
Period of communicability can last from 10-20 years
Individuals vary in response, some acquiring heavy infections and severe pathological changes, others having minor symptoms
Dependent on species/number of eggs produced: S. mansoni and S. japonicum lead to intestinal and liver damage, while S. haematobium causes bladder complications Infection - Contact with contaminated water
- Cercariae penetrate skin and enter body
- Normally starts in childhood 1 - 2 days pass - Most people show no symptoms upon first infection
- But, within one to two days of infection, initial invasion may cause a rash or itchy skin to develop - Within 1-2 months common symptoms may develop including:
> fever
> chills
> cough
> muscle aches
- Intestinal schistosomiasis:
> abdominal pain
> diarrhea
> blood in stool
> intestinal/liver damage
> liver fibrosis
> enlarged liver
- Urogenital schistosomiasis:
> blood in urine
> obstructive urinary problems
> bladder problems 2 - 6 weeks pass Chronic Schistosomiasis Can persist for years without treatment
Can lead to increased risk of bladder cancer
Can damage organs and cause failed immune system reactions
Symptoms depend on where in the body the parasites have travelled and can affect the digestive system, urinary system, heart and lungs, and central nervous system or brain Reduce transmission of the parasite
Eliminate snail as intermediate host
Increase sanitation
Reduce water contact
Reduce level of infection in an individual
Use of mass chemotherapy
In the future, vaccination ` Increase Sanitation Water sources remain unclean through human urination and defecation into bodies of water
Encourage use of latrines to eliminate water pollution
However, a few infected individuals can maintain the pollution and disease in water
Adult worms can live in water for a long time, prevalence in a community will not drop for a considerable period of time Life Cycle, cont. Adult worms live 20-30 years
Produce eggs for 3-8 years
Daily egg output:
S. haematobium: 20-250
S. mansoni: 100-300
S. japonicum: 1500-3500 Eliminate Snails as Host Introduce natural predators such as fish
Drain or fill small ponds that are infected
Line canals with concrete, increase flow rate, reduce vegetation in water
rarely effective on their own
Molluscicides to kill off snails
Also kill fish
Snail populations recover when use is stopped Reduce Water Contact http://www.cdc.gov/parasites/schistosomiasis/biology.html Acute Schistosomiasis Target groups for mass distribution of praziquantel to eliminate mild infection and prevent chronic disease
School children in endemic areas
adults in endemic areas - specifically people with occupations involving contact with infested water and women who perform domestic chores
entire communities in highly endemic areas
Treatment for individuals who are diagnosed to be infected Drug Therapy in Infected Areas Development of Vaccines Health Education
Provide separate location to wash with clean water
not cost effective
Treat drinking water by letting it stand for at least 1-2 days or bring to a boil for at least 1 minute
Boil water used for bathing or let stand for 1-2 days
Vigorously dry skin with a towel after accidental exposure and use 70% alcohol to kill parasite before it enters skin
Increase access to clean water Schistosomiasis in the World 200 Million people infected Worldwide
33.5 Million People Treated in 2010 Challenging as schistosome is able to absorb host antigen and mask its presence
Vaccine developed by Institut Pasteur de Lille from France showed good immunogenicity in Phase I and II trails in France, Niger, and Senegal
Schistosomiasis Vaccine Development Program
Based in Egypt, supported by USAID
Uses antigens shared between schistosomes and schistomules which seems promising
Candidate vaccine from FIOCRUZ in Brazil
In mice provided 67% protection against S. mansoni
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