出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/09/04 17:00:48」(JST)[Wiki en表示]
|Classification and external resources|
Ascariasis is a disease caused by the parasitic roundworm Ascaris lumbricoides. Infections have no symptoms in more than 85% of cases, especially if the number of worms is small. Symptoms increase with the number of worms present and may include shortness of breath and fever in the beginning of the disease. These may be followed by symptoms of abdominal swelling, abdominal pain and diarrhea. Children are most commonly affected, and in this age group the infection may also cause poor weight gain, malnutrition and learning problems.
Infection occurs by eating food or drink contaminated with Ascaris eggs from feces. The eggs hatch in the intestines, burrow through the gut wall, and migrate to the lungs via the blood. There they break into the alveoli and pass up the trachea, where they are coughed up and swallowed. The larvae then pass through the stomach for a second time into the intestine where they become adult worms.
Prevention is by improved sanitation, which includes improving access to toilets and proper disposal of feces. Handwashing with soap appears protective. In areas where more than 20% of the population is affected, treating everyone at regular intervals is recommended. Reoccurring infections are, however, common. There is no vaccine. Treatments recommended by the World Health Organization are the medications albendazole, mebendazole, levamisole or pyrantel pamoate. Other effective agents include tribendimidine and nitazoxanide.
About 0.8 to 1.2 billion people globally have ascariasis with the most heavily affected populations being in sub-Saharan Africa, Latin America, and Asia. This makes ascariasis the most common form of soil-transmitted helminthiasis. As of 2010 it caused about 2,700 deaths down from 3,400 in 1990. Another type of Ascaris infects pigs.
- 1 Signs and symptoms
- 2 Cause
- 2.1 Transmission
- 2.2 Life cycle
- 3 Diagnosis
- 4 Prevention
- 5 Treatment
- 6 Prognosis
- 7 Epidemiology
- 8 Society and culture
- 9 Research
- 10 Other animals
- 11 References
- 12 External links
Signs and symptoms
Most infected people have no symptoms. It is common to find that most people are infected by a small number of worms, while a small number of people are heavily infected, something that is characteristic of many worm infections. Clinical features depend on the affected body site. As larval stages travel through the body, they may cause visceral damage, peritonitis and inflammation, enlargement of the liver or spleen, and an inflammation of the lungs. Pulmonary manifestations take place during larval migration and may present as Loeffler's syndrome a transient respiratory illness associated with blood eosinophilia and pulmonary infiltrates with radiographic shadowing. The worms in the intestine may cause malabsorption and anorexia which contribute to malnutrition. The malabsorption may be due to a loss of brush border enzymes, erosion and flattening of the villi, and inflammation of the lamina propria. The worms can occasionally cause intestinal blockage when large numbers get tangled into a bolus or they may migrate from the small intestine, which may require surgery. More than 796 Ascaris lumbricoides worms weighing up to 550 g [19 ounces] were recovered at autopsy from a 2-year-old South African girl. The worms had caused torsion and gangrene of the ileum, which was interpreted as the cause of death. Bowel obstruction may occur in up to 0.2 per 1000 per year. Sometimes the worm blocks the Ampulla of Vater or goes into the main pancreatic duct resulting in acute pancreatitis with raised serum levels of Amylase and Lipase. Occasionally they can travel through the billiary tree and even into the gallbladder causing acute cholangitis or acute cholecystitis.
Ascaris takes most of its nutrients from the partially digested host food in the intestine. There is some evidence that it can secrete anti-enzymes, presumably to protect itself from digestion by the hosts' enzymes. Children are often more severely affected.
Ascariasis may result in allergies to shrimp and dustmites due to the shared antigen, tropomyosin, though this has not been confirmed in the laboratory. Ascaris have an aversion to some general anesthetics and may exit the body, sometimes through the mouth.
The source of infection is from objects which fecal matter containing eggs have contaminated. Ingestion of infective eggs from soil contaminated with human feces or contaminated vegetables and water is the primary route of infection. Infectious eggs may also occur on other objects such as hands, money and furniture. Transmission from human to human by direct contact is impossible.
Transmission also comes through municipal recycling of wastewater into crop fields. This is quite common in emerging industrial economies, and poses serious risks for not only local crop sales but also exports of contaminated vegetables. A 1986 outbreak of ascariasis in Italy was traced to irresponsible wastewater recycling used to grow Balkan vegetable exports.
Deposition of ova (eggs) in sewage hints at the degree of ascariasis incidence. A 1978 study showed about 75% of all sewage sludge samples sampled in United States urban catchments contained Ascaris ova, with rates as high as 5 to 100 eggs per litre. In Frankfort, Indiana, 87.5% of the sludge samples were positive withAscaris, Toxocara, Trichuris, and hookworm. In Macon, Georgia, one of the 13 soil samples tested positive for Ascaris. Municipal wastewater in Riyadh, Saudi Arabia detected over 100 eggs per litre of wastewater and in Czechoslovakia was as high as 240–1050 eggs per litre.
Ascariasis can often be measured by examining food for ova. In one field study in Marrakech, Morocco, where raw sewage is used to fertilize crop fields, Ascariseggs were detected at the rate of 0.18 eggs/kg in potatoes, 0.27 eggs/kg in turnip, 4.63 eggs/kg in mint, 0.7 eggs/kg in carrots, and 1.64 eggs/kg in radish. A similar study in the same area showed that 73% of children working on these farms were infected with helminths, particularly Ascaris, probably as a result of exposure to the raw sewage.
First appearance of eggs in stools is 60–70 days. In larval ascariasis, symptoms occur 4–16 days after infection. The final symptoms are gastrointestinal discomfort, colic and vomiting, fever, and observation of live worms in stools. Some patients may have pulmonary symptoms or neurological disorders during migration of the larvae. However there are generally few or no symptoms. A bolus of worms may obstruct the intestine; migrating larvae may cause pneumonitis and eosinophilia. Adult worms have a life-span of 1–2 years which means that individuals may be infected all their lives as worms die and new worms are acquired.
Eggs can survive potentially for 15 years and a single worm may produce 200 thousand eggs a day. They maintain their position by swimming against the intestinal flow.
The diagnosis is usually incidental when the host passes a worm in the stool or vomit. The eggs can be seen in smear of fresh feces examined on a glass slide under a microscope and there are various techniques to concentrate them first or increase their visibility, such as the ether sedimentation method or the Kato technique. The eggs have a characteristic shape: they are oval with a thick, mamillated shell (covered with rounded mounds or lumps), measuring 35-50 micrometer in diameter and 40-70 in length. During pulmonary disease larvae may be found in fluids aspirated from the lungs. White blood cells counts may demonstrate peripheral eosinophilia, but this is common in many parasitic infections and is not specific to ascariasis. On X-ray, 15–35 cm long filling defects, sometimes with whirled appearance (bolus of worms).
Prevention is by improved sanitation which includes improving access to toilets. Handwashing with soap may be protective but there is no evidence it affects the severity of disease.
In areas where more than 20% of the population is affected treating everyone is recommended. This has a cost of about 2 to 3 cents per person per treatment.
Medications that are used to kill roundworms are called ascaricides. Those recommended by the World Health Organization for ascariasis are: albendazole, mebendazole, levamisole and pyrantel pamoate. Other effective agents include tribendimidine and nitazoxanide.
- Piperazine A flaccid paralyzing agent that causes a blocking response of ascaris muscle to acetylcholine. The narcotizing effect immobilizes the worm, which prevents migration when treatment is accomplished with weak drugs such as thiabendazole. If used by itself it causes the worm to be passed out in the feces.
- Pyrantel pamoate may induce intestinal obstruction in a heavy worm load. Albendazole is contraindicated during pregnancy and children under 2 years.
- Thiabendazole. This may cause migration of the worm into the esophagus, so it is usually combined with piperazine.
- Hexylresorcinol effective in single dose
- Santonin, more toxic than hexylresorcinol
- Oil of chenopodium, more toxic than hexylresorcinol
Also, corticosteroids can treat some of the symptoms, such as inflammation. In some cases with severe infestation, the sudden death of the worms may cause bowel obstruction, requiring surgical intervention.
It is rare for the infections to be life-threatening.
Roughly 0.8-1.3 billion individuals are infected with this worm, primarily in Africa and Asia. About 120 to 220 million of these cases are symptomatic. As of 2010 it caused about 2,700 deaths down from 3,400 in 1990.
Ascariasis is endemic in the United States including Gulf Coast; in Nigeria and in Southeast Asia. One study indicated that the prevalence of ascariasis in the United States at about 4 million (2%).
Society and culture
In Canada in 1970, a postgraduate student tainted his roommates' food with Ascaris suum. Four of the people became seriously ill; two of these had acute respiratory failure.
There are two animal models for studying Ascaris infection.
Infections in pigs leads to poor weight gain and thus financial losses for the farmer. In pigs the infection is due to Ascaris suum.
- Dold, C; Holland, CV (Jul 2011). "Ascaris and ascariasis.". Microbes and infection / Institut Pasteur 13 (7): 632–7. doi:10.1016/j.micinf.2010.09.012. PMID 20934531.
- Hagel, I; Giusti, T (Oct 2010). "Ascaris lumbricoides: an overview of therapeutic targets.". Infectious disorders drug targets 10 (5): 349–67. doi:10.2174/187152610793180876. PMID 20701574.
- "Soil-transmitted helminth infections Fact sheet N°366". World Health Organization. June 2013.
- Ziegelbauer, K; Speich, B; Mäusezahl, D; Bos, R; Keiser, J; Utzinger, J (Jan 2012). "Effect of sanitation on soil-transmitted helminth infection: systematic review and meta-analysis.". PLoS medicine 9 (1): e1001162. doi:10.1371/journal.pmed.1001162. PMID 22291577.
- Fung, IC; Cairncross, S (Mar 2009). "Ascariasis and handwashing.". Transactions of the Royal Society of Tropical Medicine and Hygiene 103 (3): 215–22. doi:10.1016/j.trstmh.2008.08.003. PMID 18789465.
- Jia, TW; Melville, S; Utzinger, J; King, CH; Zhou, XN (2012). "Soil-transmitted helminth reinfection after drug treatment: a systematic review and meta-analysis.". PLoS neglected tropical diseases 6 (5): e1621. doi:10.1371/journal.pntd.0001621. PMID 22590656.
- Keiser, J; Utzinger, J (2010). "The drugs we have and the drugs we need against major helminth infections.". Advances in parasitology 73: 197–230. doi:10.1016/s0065-308x(10)73008-6. PMID 20627144.
- Fenwick, A (Mar 2012). "The global burden of neglected tropical diseases.". Public health 126 (3): 233–6. doi:10.1016/j.puhe.2011.11.015. PMID 22325616.
- Lozano, R (Dec 15, 2012). "Global and regional mortality from 235 causes of death for 20 age groups in 1990 and 2010: a systematic analysis for the Global Burden of Disease Study 2010.". Lancet 380 (9859): 2095–128. doi:10.1016/S0140-6736(12)61728-0. PMID 23245604.
- Anderson, R.M. & May, R.M. (1991). Infectious diseases of humans. Dynamics and control. Oxford: Oxford Scientific Publications
- Torok E. Oxford Handbook Infect Dis and Microbiol, 2009
- Hall A., Hewitt G., Tuffrey V. (2008). "A review and meta-analysis of the impact of intestinal worms on child growth and nutrition". Maternal and Child Nutrition 4 (Suppl 1): 118–236. doi:10.1111/j.1740-8709.2007.00127.x.
- Stephenson, L.S. (1987). The Impact of Helminth Infections on Human Nutrition. London: Taylor & Francis.
- Baird JK, Mistrey M, Pimsler M, Connor DH (March 1986). "Fatal human ascariasis following secondary massive infection". Am. J. Trop. Med. Hyg. 35 (2): 314–8. PMID 3953945.
- Berman, Jules J. (2012), Taxonomic Guide to Infectious Diseases: Understanding the Biologic Classes of Pathogenic Organisms, Academic Press, p. 151, ISBN 9780124158955
- Rollinson, D.; Hay, S.I. (2011), Advances in Parasitology, Volume 66, Academic Press, p. 165, ISBN 9780080879000
- Wu ML, Jones VA (January 2000). "Ascaris lumbricoides". Arch. Pathol. Lab. Med. 124 (1): 174–5. doi:10.1043/0003-9985(2000)124<0174:AL>2.0.CO;2. PMID 10629158.
- "AscarisInfection Fact Sheet".
- Pawlowski, ZS; Schultzberg K (1986). "Ascariasis and sewage in Europe". In Block JC. Epidemiological Studies of Risks Associated With the Agricultural Use of Sewage Sludge: Knowledge and Needs (EUR). Elsevier Science Pub Co. pp. 83–93. ISBN 1-85166-035-6.
- Bolbol AS (1992). "Risk of contamination of human and agricultural environment with parasites through reuse of treated municipal wastewater in Riyadh, Saudi Arabia". J Hyg Epidemiol Microbiol Immunol 36 (4): 330–7. PMID 1300348.
- Horák P (1992). "Helminth eggs in the sludge from three sewage treatment plants in Czechoslovakia". Folia Parasitol. 39 (2): 153–7. PMID 1644362.
- Habbari K, Tifnouti A, Bitton G, Mandil A (September 1999). "Helminthic infections associated with the use of raw wastewater for agricultural purposes in Beni Mellal, Morocco". East. Mediterr. Health J. 5 (5): 912–21. PMID 10983530.
- Crompton, D.W. and Pawlowski, Z. (1985). Life history and development of Ascaris lumbricoides and the persistence of human ascariasis. In: Ascariasis and its public health significance. Eds Crompton, D.W. Nesheim, M.C. and Pawlowski, Z.S. London: Taylor & Francis
- Holt, Jr Emmett L, McIntosh Rustin: Holt's Diseases of Infancy and Childhood: A Textbook for the Use of Students and Practitioners. Appleton and Co, New York,11th edition
- Phills JA, Harrold AJ, Whiteman GV, Perelmutter L (May 1972). "Pulmonary infiltrates, asthma and eosinophilia due to Ascaris suum infestation in man". N. Engl. J. Med. 286 (18): 965–70. doi:10.1056/NEJM197205042861802. PMID 5062734.
- Howes HL (June 1971). "Anthelmintic studies with pyrantel. II. Prophylactic activity in a mouse-ascaris suum test model". J. Parasitol. (The Journal of Parasitology, Vol. 57, No. 3) 57 (3): 487–93. doi:10.2307/3277899. JSTOR 3277899. PMID 5090955.
- Lichtensteiger CA, DiPietro JA, Paul AJ, Neumann EJ, Thompson L (April 1999). "Persistent activity of doramectin and ivermectin against Ascaris suum in experimentally infected pigs". Vet. Parasitol. 82 (3): 235–41. doi:10.1016/S0304-4017(99)00018-7. PMID 10348103.
- Video of removal of Ascari lumbricoides with an endoscope
- Images (warning, very graphic):Image 1, Human Impact
- CDC DPDx Parasitology Diagnostic Web Site
- Ascariasis: Radiology and color pathology pictures from MedPix
- Discussion of Ascaris on the "This week in Parasitism" Podcast
全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.
- 1. 回虫症 ascariasis
- 2. 回虫症の肺症状 pulmonary manifestations of ascariasis
- 3. 駆虫薬療法 anthelminthic therapies
- 4. 胆道寄生虫症の内視鏡診断および管理 endoscopic diagnosis and management of biliary parasitosis
- 5. 蟯虫症および鞭虫症 enterobiasis and trichuriasis
- Ascariasis in humans and pigs on small-scale farms, maine, USA, 2010-2013.
- Miller LA, Colby K, Manning SE, Hoenig D, McEvoy E, Montgomery S, Mathison B, de Almeida M, Bishop H, Dasilva A, Sears S.
- Emerging infectious diseases.Emerg Infect Dis.2015 Feb;21(2):332-4. doi: 10.3201/eid2102.140048.
- Ascaris is a genus of parasitic nematodes that can cause infections in humans and pigs. During 2010-2013, we identified 14 cases of ascariasis in persons who had contact with pigs in Maine, USA. Ascaris spp. are important zoonotic pathogens, and prevention measures are needed, including health educa
- PMID 25626125
- [Intestinal occlusion due to ascariasis].
- Moscatelli G1, Orbe G1, Etchepareborda N1, Altcheh J1.
- Archivos argentinos de pediatría.Arch Argent Pediatr.2015 Jan 1;113(1):88-9. doi: 10.1590/S0325-00752015000100024.
- PMID 25622166
- Host genetics and parasitic infections.
- Mangano VD1, Modiano D.
- Clinical microbiology and infection : the official publication of the European Society of Clinical Microbiology and Infectious Diseases.Clin Microbiol Infect.2014 Dec;20(12):1265-75. doi: 10.1111/1469-0691.12793. Epub 2014 Dec 14.
- Parasites still impose a high death and disability burden on human populations, and are therefore likely to act as selective factors for genetic adaptations. Genetic epidemiological investigation of parasitic diseases is aimed at disentangling the mechanisms underlying immunity and pathogenesis by l
- PMID 25273270
- 馬の用語事典 - 回虫症 (ascariasis)の用語解説 - 馬回虫が寄生することによって起こる病気。馬回虫は15〜30cmと虫体が非常に大きい。主に小腸に寄生する。抵抗力の低い幼駒に寄生することが多く、寄生率は高い。幼虫は円虫と同様に体内 ...
- Education and information about ascariasis, including fact sheets and information on prevention and control, epidemiology, diagnosis and treatment. ... An estimated 807-1,221 million people in the world are infected with Ascaris lumbricoides ...