Ascariasis final
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Ascariasis
October 6, 2009Presented by Melissa Torres
Photo extracted from: http://emedicine.medscape.com/article/212510
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Soil transmitted helminths
• Parasite nematodes– Infection from contact with eggs/ larvae in soil
– Human to human direct transmission is impossible*
• Nematodes include– Roundworms, whipworms, and hookworms
– Common to be infected with all three worms
• One of the world’s most important causes of physical and intellectual growth retardation.
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What is Ascariasis?
• Most common helminthic disease– Estimated worldwide prevalence of 25%
– 0.8-1.22 billion people
• Usually asymptomatic
• Most prevalent in children– Highest prevalence = 2 to 10 year olds
– Highest intensity = 5 to 15 year olds
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Symptomatic Ascariasis
• May manifest into–Growth retardation– Pneumonitis/ verminous pneumonia– Intestinal obstruction–Hepatobiliary and pancreatic injury– Eosinophilia*
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Climate is an important factor
• Warm and moist climates– Latin America and Caribbean
– Sub-Saharan Africa
–Middle East and north Africa
– India
– South Asia
– East Asia and Pacific Islands
– China
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A. lumbricoides
Extracted from Soil-transmitted helminth infections: ascariasis, trichuriasis, and hookwormFigure 1: Adult male and female soil-transmitted helminths
Extracted from http://en.wikipedia.org/wiki/Ascaris_lumbricoides
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Ascaris lumbricoides• Largest of nematodes infecting humans• Highest daily egg output• Shortest lifespan
Extracted from Soil-transmitted helminth infections: ascariasis, trichuriasis, and hookwormTable 2: Characteristics of the soil-transmitted helminths: adult worms of greatest public-health significance
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Ascaris lumbricoides
Extracted from Soil-transmitted helminth infections: ascariasis, trichuriasis, and hookwormFigure 2: Soil transmitted helminth eggs
Fertilized eggs•Contain a zygote•And a thick eggshell consisting of four layers
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Egg shed facts:
• Humans with ascariasis can shed in their faeces– Fertilized eggs only• 45% of infected persons
– Unfertilized eggs only• 20% of infected persons
– Or fertilized and unfertilized eggs• 40% of infected persons
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Ascaris suum
• Swine nematode– Difficult to distinguish from A. lumbricoides
• Possibility of zoonotic infection– In well developed countries
– Little evidence shown on transmission of porcine ascariasis to humans
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Life Cycle
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Diagnosis
• Stool examination– Kato-Katz fecal smear– McMaster method
• Ultrasonography and endoscopy– ECRP
Photo extracted from http://www.lnrcancernetwork.nhs.uk/images/ERCP.jpg
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Treatment
• Drug therapy– Adult worms only!
• Benzimidazole anthelminthic drugs– Albendazole = DOC– Mebendazole
• During pregnancy– Pyrantel pamoate
Albendazole
http://commons.wikimedia.org/wiki/File:Albendazole_structure.png
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Treatment
• Paralyzing vermifuges– pyrantel pamoate– Piperazine– ivermectine
• Nitazoxanide– Primariliy for protozoal
infection
• Vitamin A supplements
Pyrantel pamoate
http://commons.wikimedia.org/wiki/File:Pyrantel_pamoate.png
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Surgery
• Deworming – Should be done first
• Intestinal or Bilial surgery– ECRP– Cholecystectomy
Photo extracted from http://www.medscape.com/viewarticle/451597_3
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Prevention
• Community control– Difficult to achieve
• Health education– Along with sanitation programs
• Mass treatments– They do not seem to decrease transmission rates
• Vaccine in progress– Nasally administered 16-kd secretory protein
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References
1. Bethony, S.B., et al. (2006). Soil transmitted helminth infections: ascariaisis, trichuriasis, and hookworm. The lancet 2006; 367, 1521-1532.
2. Fincham, J.E., et al. (2007). Ascaris, co-infection and allergy: the importance of analysis based on immunological variables rather than egg excretion. Transactions of the Royal Society of Tropical Medicine and Hygiene; 101, 680-682.
3. Haburchak, D.R.. (2008, September 12). Ascariasis. Emedicine. Retrieved September 18, 2009 from http://emedicine.medscape.com/article/212510
4. Peng, W., Zhou, X., & Gasser, R.B.. (2003). Ascaris egg profiles in human faeces: biological and epidemiological implications. Parasitology; 127, 283-290.
5. Sherman, S.C., & Weber, J.M.. (2005). Visual Diagnosis in Emergency Medicine: The CT diagnosis of ascariasis. The Journal of Emergency Medicine; 28, 4, 471-472.
6. Shultz, M.G.. (1982). Ascariasis: nutritional Implications. Review of Infectious Diseases; 4, 815-820.
7. Williams, D., Burke, G., & Hendley, O.J.. (1974) Brief Clinical and Laboratory Observations: Ascariasis: A family disease. The Journal of pediatrics; 853-854
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The hygiene hypothesis
• Enhanced TH2 response– Susceptibility versus protection
• “Soil transmitted helminths are though to survive within the host not just by warding off the immune attack, but instead by aggressively subverting the host immune response…” (2006, Bethony et al)