Whipworm

Back

Background

Trichuris trichiura, also known as whipworm, acquired the name for the distinctive resemblance of the adult worm to the handle and lash of a whip.



View Image

Adult T trichiura worm removed during a colonoscopy. Courtesy of the CDC (http://phil.cdc.gov/phil/home.asp).

It is a roundworm of the phylum Nematoda. Along with hookworm and Ascaris, whipworm constitutes soil transmitted helminths (STH) and attributing to the major disease burden worldwide.[1]

Pathophysiology

Humans are the only known host of T trichiura and no animal reservoir is recognized.

The organism is spread via the fecal-oral route via ingestion of embyronated eggs with contaminated food or contact with contaminated hands. After ingestion the eggs hatch in the small intestine into the larval form, which penetrate the small intestinal mucosa.

After approximately one week, the immature worms move passively to the large intestine and proximal colon and penetrate the mucosal epithelial cells. The worm continues to expand intracellularly creating tunnels in the epithelium. The posterior end of the worm eventually ruptures the cell membrane and the worm protrudes partially into the lumen of the large intestine, while the anterior part still imbedded in the epithelium. Thus, the worm disrupts the normal colonic architecture; however, the host inflammatory response is the major contributor to the pathogenesis of the worm infection.

About 3 months after the ingestion, the fertilized female worm starts laying eggs. The female worm is capable of producing 3,000-20,000 eggs a day. The infected host passes unembryonated eggs in their feces and the maturation of eggs requires warm humid environment. Egg maturation occurs in approximately 2-6 weeks. T. trichura eggs are bile-stained and have a characteristic barrel-shape with the presence of polar plugs in the egg shell. The embryonated egg can maintain viability for several months under suitable conditions. Destruction occurs with exposure to direct sunlight for more than 12 hours and to temperatures of less than -8°C or higher than 40°C for one hour.

The adult worm usually reaches 3-5 cm in length and has a lifespan of 1-3 years.



View Image

Life cycle of whipworm. The unembryonated eggs are passed with the stool (1). In the soil, the eggs develop into a 2-cell stage (2), an advanced cleav....

Epidemiology

Frequency

United States

Prevalence of whipworm infestation is less than 0.1%, although adequate studies are quite outdated.[2] The most common areas of infection are the southern Appalachian range and Gulf coast states.[3]

International

CDC estimated 604-795 million people in the world are infected with whipworm.

The highest prevalence rates of soil-transmitted helminthes occur in sub-Saharan Africa and southern and eastern Asia.[1] As with other soil-transmitted helminthes, the prevalence is higher in tropical and subtropical regions of the world, which provide the moist, humid environment required for the eggs to mature. Due to the poor sanitation practices in the rural areas of these regions the disease is prevalent.



View Image

Distribution of soil transmitted helminths (STH) Trichuris trichiura infection prevalence in 2010 based on geostatistical models for sub-Saharan Afric....

Mortality/Morbidity

Most infections are asymptomatic. Symptoms are related to the worm load or number of worms involved in an infection. Heavy infections (hundreds to thousands of worms) can lead to death secondary to GI and hematologic complications.

Mortality can result from complications such as intestinal obstruction or rectal prolapse requiring surgical intervention.

Morbidity is directly related to worm burden. Soil-transmitted helminths impair the nutritional status of the host due to intestinal bleeding, diarrhea or dysentery and malabsorption of nutrients resulting in growth delay and failure to thrive. $4.98 million year lost due to disability (YLD) attributable to soil-transmitted helminth worldwide. 13% were attributable to T. trichiura in 2010.[4]

Age

Although infections are observed in all age groups, most heavy infections are observed in the pediatric population. This probably reflects the increased likelihood of children to have poor hygiene and to play in soil that carries the worms' mature eggs.

History

See the list below:

Physical

See the list below:

Causes

See the list below:

Laboratory Studies

Diagnosis is based on the microscopic detection of eggs or larvae in fresh or fixed stool samples.[6] The eggs are bile stained with characteristic barrel (American football) shape with translucent polar plugs.



View Image

Egg from the "human whipworm". Courtesy of the CDC (http://phil.cdc.gov/phil/home.asp).

The stool commonly contains RBCs and WBCs, including eosinophils.

No serological tests or PCR testing in stool have been validated to detect infection with Trichuris.

Other Tests

Other laboratory findings are non-specific. Peripheral CBC may reveal anemia (iron deficiency anemia) and ESR could be elevated due to ongoing inflammation.[7]

Procedures

Anoscopy may be useful. In heavy infections, worms can be directly visualized.

Histologic Findings

The pathologic changes are noted in the large intestine, confined primarily to the mucosal epithelium. This differentiates whipworm infection with IBD as there is little or no involvement of the submucosa and muscularis layer.

The anterior part of the worm is embedded in the mucosa and the posterior two-fifth floats in the lumen. On biopsy there is intense eosinophilic infiltrate noted around the worm.[8]

Medical Care

Treatment with broad-spectrum anthelminthic agents is key. Most infections can be treated successfully with mebendazole, albendazole, or ivermectin. These anthelminthic medications should be taken for 3 days. Dosage guidelines and important drug interactions are summarized in the medication section. Albendazole should be taken with food. Ivermectin should be taken with water on an empty stomach and the safety of ivermectin for children weighing less than 15 kg has not been established. Neither albendazole nor ivermectin is FDA-approved for treating whipworm.

A systematic review and network meta-analysis by Moser et al reported that T. trichiura cure rates with albendazole and mebendazole were 30.7% and 42.1%, respectively. The study also reported that between 1995 to 2015, albendazole cure rates decreased from 38.6% to 16.4% and egg-reduction rates decreased from 72.6% to 43.4% for albendazole and 91.4% to 54.7% for mebendazole.[9]

The combination of single dose of ivermectin and albendazole, or ivermectin and mebendazole, improves cure rates of 38% and 55% respectively.[10]

Consultations

Consultations with the following specialists may be appropriate:

Albendazole (Albenza)

Clinical Context:  A benzimidazole carbamate drug that inhibits tubulin polymerization, resulting in degeneration of cytoplasmic microtubules. Decreases ATP production in worms, causing energy depletion, immobilization, and, finally, death. Converted in the liver to its primary metabolite, albendazole sulfoxide. Less than 1% of the primary metabolite is excreted in the urine. Plasma level is noted to rise significantly (as much as 5-fold) when ingested after high-fat meal. Experience with patients < 6 y is limited.

To avoid inflammatory response in CNS, patient must also be started on anticonvulsants and high-dose glucocorticoids.

Well tolerated and does not appear to increase risk of worm obstruction. For pregnant women, pyrantel pamoate is the DOC.

Mebendazole (Vermox)

Clinical Context:  Well tolerated and does not appear to increase risk of worm obstruction. Causes worm death by selectively and irreversibly blocking uptake of glucose and other nutrients in susceptible adult intestine where helminths dwell. Available as a 100-mg chewable tablet that can be swallowed whole, chewed, or crushed and mixed with food.

Pyrantel pamoate (Pin Rid, Pin X)

Clinical Context:  Neuromuscular blocking agent used to slowly paralyze worm to be eliminated from GI tract. DOC during pregnancy.

Nitazoxanide (Alinia)

Clinical Context:  Inhibits growth of Cryptosporidium parvum sporozoites and oocysts and Giardia lamblia trophozoites. Elicits antiprotozoal activity by interfering with pyruvate-ferredoxin oxidoreductase (PFOR) enzyme-dependent electron transfer reaction, which is essential to anaerobic energy metabolism. Available as a 20-mg/mL oral susp. May have activity in trichuriasis.

Ivermectin (Stromectol)

Clinical Context:  Binds selectively with glutamate-gated chloride ion channels in invertebrate nerve and muscle cells, causing cell death. Half-life is 16 h; metabolized in liver. Off-label use for T trichiura in combination with albendazole or mebendazole.

Class Summary

Parasite biochemical pathways are sufficiently different from the human host to allow selective interference by chemotherapeutic agents in relatively small doses.

Further Outpatient Care

Reexamination of stool specimens 2 weeks after therapy to determine whether the worms have been eliminated is helpful for assessing therapy. Retreatment may be necessary if symptoms persist 2-3 weeks after initial therapy.

Deterrence/Prevention

Proper disposal of fecal material is indicated. Mass treatment of infected school-aged populations can reduce whipworm transmission in communities with endemic infection.

Some clinicians have suggested periodic deworming programs for children in endemic areas.[11]

Complications

Rectal prolapse, dysentery, anemia, malnutrition, and growth retardation all can complicate heavy infections.

Prognosis

With treatment, prognosis is typically excellent.

Patient Education

Emphasize good hygiene and avoidance of pica. Proper disposal of fecal material needs to be emphasized.

Author

Shipra Gupta, MD, Assistant Professor of Pediatrics, West Virginia University School of Medicine

Disclosure: Nothing to disclose.

Coauthor(s)

Jocelyn Y Ang, MD, FAAP, FIDSA, Associate Professor, Department of Pediatrics, Wayne State University School of Medicine; Consulting Staff, Division of Infectious Diseases, Children's Hospital of Michigan

Disclosure: Nothing to disclose.

Specialty Editors

Mary L Windle, PharmD, Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

Martin Weisse, MD, Program Director, Associate Professor, Department of Pediatrics, West Virginia University

Disclosure: Nothing to disclose.

Chief Editor

Russell W Steele, MD, Clinical Professor, Tulane University School of Medicine; Staff Physician, Ochsner Clinic Foundation

Disclosure: Nothing to disclose.

Additional Contributors

Ashir Kumar, MD, MBBS, FAAP, Professor Emeritus, Department of Pediatrics and Human Development, Michigan State University College of Human Medicine

Disclosure: Nothing to disclose.

Acknowledgements

Steven L Lanski, MD Department of Pediatrics, Division of Pediatric Emergency Medicine, Assistant Professor, Emory University and Children's Healthcare of Atlanta at Egleston

Steven L Lanski, MD is a member of the following medical societies: American Academy of Pediatrics

Disclosure: Nothing to disclose.

Tina Slusher, MD Assistant Professor, Department of Pediatrics, Section of Pediatric Critical Care, West Virginia University

Tina Slusher, MD is a member of the following medical societies: Society of Critical Care Medicine

Disclosure: Nothing to disclose.

References

  1. Knopp S, Steinmann P, Keiser J, Utzinger J. Nematode infections: soil-transmitted helminths and trichinella. Infect Dis Clin North Am. 2012 Jun. 26(2):341-58. [View Abstract]
  2. Starr MC, Montgomery SP. Soil-transmitted helminthiasis in the United States: a systematic review--1940-2010. Am J Trop Med Hyg. 2011 Oct. 85(4):680-4. [View Abstract]
  3. Kappus KK, Juranek DD, Roberts JM. Results of testing for intestinal parasites by state diagnostic laboratories, United States, 1987. MMWR CDC Surveill Summ. 1991 Dec. 40(4):25-45. [View Abstract]
  4. Pullan RL, Smith JL, Jasrasaria R, Brooker SJ. Global numbers of infection and disease burden of soil transmitted helminth infections in 2010. Parasit Vectors. 2014 Jan 21. 7:37. [View Abstract]
  5. Bethony J, Brooker S, Albonico M, Geiger SM, Loukas A, Diemert D. Soil-transmitted helminth infections: ascariasis, trichuriasis, and hookworm. Lancet. 2006 May 6. 367(9521):1521-32. [View Abstract]
  6. Glinz D, Silue KD, Knopp S, et al. Comparing diagnostic accuracy of Kato-Katz, Koga agar plate, ether-concentration, and FLOTAC for Schistosoma mansoni and soil-transmitted helminths. PLoS Negl Trop Dis. 2010 Jul 20. 4(7):e754. [View Abstract]
  7. Bundy DA, Cooper ES. Trichuris and trichuriasis in humans. Adv Parasitol. 1989. 28:107-73. [View Abstract]
  8. Lauwers G, Mino-Kenudson M, Kradin RL. Infections of the Gastrointestinal Tract. Kradin RL. Diagnostic Pathology of Infectious Disease. Philadlelphia, PA: Elsevier; 2010. 215-254.
  9. Moser W, Schindler C, Keiser J. Efficacy of recommended drugs against soil transmitted helminths: systematic review and network meta-analysis. BMJ. 2017 Sep 25. 358:j4307. [View Abstract]
  10. Knopp S, Mohammed KA, Speich B, Hattendorf J, Khamis IS, Khamis AN. Albendazole and mebendazole administered alone or in combination with ivermectin against Trichuris trichiura: a randomized controlled trial. Clin Infect Dis. 2010 Dec 15. 51(12):1420-8. [View Abstract]
  11. Linehan M, Hanson C, Weaver A, et al. Integrated Implementation of Programs Targeting Neglected Tropical Diseases through Preventive Chemotherapy: Proving the Feasibility at National Scale. Am J Trop Med Hyg. 2011 Jan. 84(1):5-14. [View Abstract]
  12. Nascimento-Carvalho CM, de Fatima Gesteira M, Azul-Neto LS, Andrade MQ. Prolonged treatment with albendazole for massive trichuriasis infection. Pediatr Infect Dis J. 2004 Nov. 23(11):1070. [View Abstract]
  13. Diaz E, Mondragon J, Ramirez E, Bernal R. Epidemiology and control of intestinal parasites with nitazoxanide in children in Mexico. Am J Trop Med Hyg. 2003 Apr. 68(4):384-5. [View Abstract]
  14. Gilles HM, Hoffman PS. Treatment of intestinal parasitic infections: a review of nitazoxanide. Trends Parasitol. 2002 Mar. 18(3):95-7. [View Abstract]
  15. Pearson RD. Nitazoxanide As Treatment of Intestinal Parasites in Children. Curr Infect Dis Rep. 2004 Feb. 6(1):25-26. [View Abstract]
  16. AAP. Trichuriasis (Whipworm Infection). Red Book: 2009 Report of the Committee on Infectious Diseases. 28th. Elk Grove Village, IL: American Academy of Pediatrics; 2009. 675-6.
  17. Arruda LK, Santos AB. Immunologic responses to common antigens in helminthic infections and allergic disease. Curr Opin Allergy Clin Immunol. 2005 Oct. 5(5):399-402. [View Abstract]
  18. Trichuriasis. Spector JM, Gibson TE. Atlas of Pediatrics in the Tropics and Resource-Limited Settings. Elk Grove Village, IL: American Academy of Pediatrics; 2009. 265-267.
  19. Conlan JV, Khamlome B, Vongxay K, et al. Soil-Transmitted Helminthiasis in Laos: A Community-Wide Cross-Sectional Study of Humans and Dogs in a Mass Drug Administration Environment. Am J Trop Med Hyg. 2012 Apr. 86(4):624-634. [View Abstract]
  20. Cooper PJ. Interactions between helminth parasites and allergy. Curr Opin Allergy Clin Immunol. 2009 Feb. 9(1):29-37. [View Abstract]
  21. da Costa e Silva EJ, de Albuquerque SC. Trichuris trichiura. Pediatr Radiol. 2007 Feb. 37(2):239. [View Abstract]
  22. Elliott DE, Summers RW, Weinstock JV. Helminths and the modulation of mucosal inflammation. Curr Opin Gastroenterol. 2005 Jan. 21(1):51-8. [View Abstract]
  23. Ezeamama AE, Friedman JF, Acosta LP, et al. Helminth infection and cognitive impairment among Filipino children. Am J Trop Med Hyg. 2005 May. 72(5):540-8. [View Abstract]
  24. Eziefula AC, Brown M. Intestinal nematodes: disease burden, deworming and the potential importance of co-infection. Curr Opin Infect Dis. 2008 Oct. 21(5):516-22. [View Abstract]
  25. Falcone FH, Pritchard DI. Parasite role reversal: worms on trial. Trends Parasitol. 2005 Apr. 21(4):157-60. [View Abstract]
  26. Flisser A, Valdespino JL, Garcia-Garcia L, et al. Using national health weeks to deliver deworming to children: lessons from Mexico. J Epidemiol Community Health. 2008 Apr. 62(4):314-7. [View Abstract]
  27. Fox LM, Furness BW, Haser JK, et al. Tolerance and efficacy of combined diethylcarbamazine and albendazole for treatment of Wuchereria bancrofti and intestinal helminth infections in Haitian children. Am J Trop Med Hyg. 2005 Jul. 73(1):115-21. [View Abstract]
  28. Geary TG. Are new anthelmintics needed to eliminate human helminthiases?. Curr Opin Infect Dis. 2012 Dec. 25(6):709-17. [View Abstract]
  29. Goodman D, Haji HJ, Bickle QD, et al. A comparison of methods for detecting the eggs of Ascaris, Trichuris, and hookworm in infant stool, and the epidemiology of infection in Zanzibari infants. Am J Trop Med Hyg. 2007 Apr. 76(4):725-31. [View Abstract]
  30. Grencis RK, Cooper ES. Enterobius, trichuris, capillaria, and hookworm including ancylostoma caninum. Gastroenterol Clin North Am. 1996 Sep. 25(3):579-97. [View Abstract]
  31. Gyorkos TW, Gilbert NL, Larocque R, Casapía M, Montresor A. Re-visiting Trichuris trichiura intensity thresholds based on anemia during pregnancy. PLoS Negl Trop Dis. 2012. 6(9):e1783. [View Abstract]
  32. Gyorkos TW, Maheu-Giroux M, Casapía M, Joseph SA, Creed-Kanashiro H. Stunting and helminth infection in early preschool-age children in a resource-poor community in the Amazon lowlands of Peru. Trans R Soc Trop Med Hyg. 2011 Apr. 105(4):204-8. [View Abstract]
  33. Hall A, Hewitt G, Tuffrey V, de Silva N. A review and meta-analysis of the impact of intestinal worms on child growth and nutrition. Matern Child Nutr. 2008 Apr. 4 Suppl 1:118-236. [View Abstract]
  34. Hamer D, Despommier D. Intestinal nematodes. Gorbach SL, Bartlett JG, Blacklow NR, eds. Infectious Diseases. 2nd ed. Philadelphia, Pa: WB Saunders Co; 1998. 2003-5.
  35. Harhay MO, Horton J, Olliaro PL. Epidemiology and control of human gastrointestinal parasites in children. Expert Rev Anti Infect Ther. 2010 Feb. 8(2):219-34. [View Abstract]
  36. Hotez PJ, Arora S, Bethony J, et al. Helminth infections of children: prospects for control. Adv Exp Med Biol. 2005. 568:135-44. [View Abstract]
  37. Hutchinson SE, Powell CA, Walker SP, et al. Nutrition, anaemia, geohelminth infection and school achievement in rural Jamaican primary school children. Eur J Clin Nutr. 1997 Nov. 51(11):729-35. [View Abstract]
  38. Keiser J, Utzinger J. Efficacy of current drugs against soil-transmitted helminth infections: systematic review and meta-analysis. JAMA. 2008 Apr 23. 299(16):1937-48. [View Abstract]
  39. Knopp S, Mohammed KA, Rollinson D, Stothard JR, Khamis IS, Utzinger J. Changing patterns of soil-transmitted helminthiases in Zanzibar in the context of national helminth control programs. Am J Trop Med Hyg. 2009 Dec. 81(6):1071-8. [View Abstract]
  40. Krishnamurthy S, Samanta D, Yadav S. Trichuris dysentery syndrome with eosinophilic leukemoid reaction mimicking inflammatory bowel disease. J Postgrad Med. 2009 Jan-Mar. 55(1):76-7. [View Abstract]
  41. Kung'u JK, Goodman D, Haji HJ, Ramsan M, Wright VJ, Bickle QD. Early helminth infections are inversely related to anemia, malnutrition, and malaria and are not associated with inflammation in 6- to 23-month-old Zanzibari children. Am J Trop Med Hyg. 2009 Dec. 81(6):1062-70. [View Abstract]
  42. Levecke B, Behnke JM, Ajjampur SS, Albonico M, Ame SM, Charlier J, et al. A comparison of the sensitivity and fecal egg counts of the McMaster egg counting and Kato-Katz thick smear methods for soil-transmitted helminths. PLoS Negl Trop Dis. 2011 Jun. 5(6):e1201. [View Abstract]
  43. Linehan M, Hanson C, Weaver A, Baker M, Kabore A, Zoerhoff KL, et al. Integrated implementation of programs targeting neglected tropical diseases through preventive chemotherapy: proving the feasibility at national scale. Am J Trop Med Hyg. 2011 Jan. 84(1):5-14. [View Abstract]
  44. Lorenzetti R, Campo SM, Stella F, et al. An unusual endoscopic finding: Trichuris trichiura. Case report and review of the literature. Dig Liver Dis. 2003 Nov. 35(11):811-3. [View Abstract]
  45. Markell EK. Intestinal nematode infections. Pediatr Clin North Am. 1985 Aug. 32(4):971-86. [View Abstract]
  46. Mascarini-Serra LM, Telles CA, Prado MS, et al. Reductions in the prevalence and incidence of geohelminth infections following a city-wide sanitation program in a Brazilian Urban Centre. PLoS Negl Trop Dis. 2010 Feb 2. 4(2):e588. [View Abstract]
  47. McSorley HJ, Maizels RM. Helminth infections and host immune regulation. Clin Microbiol Rev. 2012 Oct. 25(4):585-608. [View Abstract]
  48. Medical Economics Company. Physicians' Desk Reference. 53rd ed. Montvale, NJ: Medical Economics Co; 1999. 1442, 3018.
  49. Moncayo AL, Vaca M, Amorim L, Rodriguez A, Erazo S, Oviedo G. Impact of long-term treatment with ivermectin on the prevalence and intensity of soil-transmitted helminth infections. PLoS Negl Trop Dis. 2008. 2(9):e293. [View Abstract]
  50. Mukhopadhyay C, Wilson G, Chawla K, Vs B, Shivananda PG. A 6 year Geohelminth infection profile of children at high altitude in Western Nepal. BMC Public Health. 2008 Mar 27. 8:98. [View Abstract]
  51. Namwanje H, Kabatereine NB, Olsen A. Efficacy of single and double doses of albendazole and mebendazole alone and in combination in the treatment of Trichuris trichiura in school-age children in Uganda. Trans R Soc Trop Med Hyg. 2011 Oct. 105(10):586-90. [View Abstract]
  52. Quihui L, Valencia ME, Crompton DW, et al. Role of the employment status and education of mothers in the prevalence of intestinal parasitic infections in Mexican rural schoolchildren. BMC Public Health. 2006. 6:225. [View Abstract]
  53. Ravasi DF, O'Riain MJ, Davids F, Illing N. Phylogenetic evidence that two distinct Trichuris genotypes infect both humans and non-human primates. PLoS One. 2012. 7(8):e44187. [View Abstract]
  54. Rayan P, Verghese S, McDonnell PA. Geographical location and age affects the incidence of parasitic infestations in school children. Indian J Pathol Microbiol. 2010 Jul-Sep. 53(3):498-502. [View Abstract]
  55. Reddy M, Gill SS, Kalkar SR, et al. Oral drug therapy for multiple neglected tropical diseases: a systematic review. JAMA. 2007 Oct 24. 298(16):1911-24. [View Abstract]
  56. Reina Ortiz M, Schreiber F, Benitez S, Broncano N, Chico ME, Vaca M, et al. Effects of chronic ascariasis and trichuriasis on cytokine production and gene expression in human blood: a cross-sectional study. PLoS Negl Trop Dis. 2011 Jun. 5(6):e1157. [View Abstract]
  57. Sayasone S, Vonghajack Y, Vanmany M, Rasphone O, Tesana S, Utzinger J, et al. Diversity of human intestinal helminthiasis in Lao PDR. Trans R Soc Trop Med Hyg. 2009 Mar. 103(3):247-54. [View Abstract]
  58. Singh C, Zargar SA, Masoodi I, Shoukat A, Ahmad B. Predictors of intestinal parasitosis in school children of Kashmir: a prospective study. Trop Gastroenterol. 2010 Apr-Jun. 31(2):105-7. [View Abstract]
  59. Stoltzfus RJ, Albonico M, Tielsch JM, et al. School-based deworming program yields small improvement in growth of Zanzibari school children after one year. J Nutr. 1997 Nov. 127(11):2187-93. [View Abstract]
  60. Sturrock HJ, Gething PW, Clements AC, Brooker S. Optimal survey designs for targeting chemotherapy against soil-transmitted helminths: effect of spatial heterogeneity and cost-efficiency of sampling. Am J Trop Med Hyg. 2010 Jun. 82(6):1079-87. [View Abstract]
  61. Tang N, Luo NJ. Prevalence of parasites in kindergarten children. Int J Infect Dis. 2005 May. 9(3):178-9. [View Abstract]
  62. Tarafder MR, Carabin H, Joseph L, Balolong E Jr, Olveda R, McGarvey ST. Estimating the sensitivity and specificity of Kato-Katz stool examination technique for detection of hookworms, Ascaris lumbricoides and Trichuris trichiura infections in humans in the absence of a 'gold standard'. Int J Parasitol. 2010 Mar 15. 40(4):399-404. [View Abstract]
  63. Tinuade O, John O, Saheed O, et al. Parasitic etiology of childhood diarrhea. Indian J Pediatr. 2006 Dec. 73(12):1081-4. [View Abstract]
  64. Tokmak N, Koc Z, Ulusan S, Koltas IS, Bal N. Computed tomographic findings of trichuriasis. World J Gastroenterol. 2006 Jul 14. 12(26):4270-2. [View Abstract]
  65. Turner JD, Jackson JA, Faulkner H, et al. Intensity of intestinal infection with multiple worm species is related to regulatory cytokine output and immune hyporesponsiveness. J Infect Dis. 2008 Apr 15. 197(8):1204-12. [View Abstract]
  66. U.S. Food and Drug Administration (FDA). Teva Product Line Changes. Available at http://www.fda.gov/downloads/Drugs/DrugSafety/DrugShortages/UCM277319.pdf. Accessed: December 22, 2014.
  67. Utzinger J, Botero-Kleiven S, Castelli F, Chiodini PL, Edwards H, Köhler N, et al. Microscopic diagnosis of sodium acetate-acetic acid-formalin-fixed stool samples for helminths and intestinal protozoa: a comparison among European reference laboratories. Clin Microbiol Infect. 2009 May 18. [View Abstract]
  68. Vercruysse J, Behnke JM, Albonico M, Ame SM, Angebault C, Bethony JM, et al. Assessment of the anthelmintic efficacy of albendazole in school children in seven countries where soil-transmitted helminths are endemic. PLoS Negl Trop Dis. 2011 Mar 29. 5(3):e948. [View Abstract]
  69. Vercruysse J, Levecke B, Prichard R. Human soil-transmitted helminths: implications of mass drug administration. Curr Opin Infect Dis. 2012 Dec. 25(6):703-8. [View Abstract]
  70. Walden J. Parasitic diseases. Other roundworms. Trichuris, hookworm, and Strongyloides. Prim Care. 1991 Mar. 18(1):53-74. [View Abstract]
  71. Wang LJ, Cao Y, Shi HN. Helminth infections and intestinal inflammation. World J Gastroenterol. 2008 Sep 7. 14(33):5125-32. [View Abstract]
  72. Wang X, Zhang L, Luo R, Wang G, Chen Y, Medina A, et al. Soil-transmitted helminth infections and correlated risk factors in preschool and school-aged children in rural Southwest China. PLoS One. 2012. 7(9):e45939. [View Abstract]
  73. Wani SA, Ahmad F, Zargar SA, Dar PA, Dar ZA, Jan TR. Intestinal helminths in a population of children from the Kashmir valley, India. J Helminthol. 2008 Dec. 82(4):313-7. [View Abstract]
  74. Wani SA, Ahmad F, Zargar SA, Dar ZA, Dar PA, Tak H, et al. Soil-transmitted helminths in relation to hemoglobin status among school children of the Kashmir Valley. J Parasitol. 2008 Jun. 94(3):591-3. [View Abstract]
  75. Wen LY, Yan XL, Sun FH, Fang YY, Yang MJ, Lou LJ. A randomized, double-blind, multicenter clinical trial on the efficacy of ivermectin against intestinal nematode infections in China. Acta Trop. 2008 Jun. 106(3):190-4. [View Abstract]
  76. Xu LQ, Yu SH, Jiang ZX, et al. Soil-transmitted helminthiases: nationwide survey in China. Bull World Health Organ. 1995. 73(4):507-13. [View Abstract]
  77. Youn H. Review of zoonotic parasites in medical and veterinary fields in the Republic of Korea. Korean J Parasitol. 2009 Oct. 47 Suppl:S133-41. [View Abstract]

Adult T trichiura worm removed during a colonoscopy. Courtesy of the CDC (http://phil.cdc.gov/phil/home.asp).

Life cycle of whipworm. The unembryonated eggs are passed with the stool (1). In the soil, the eggs develop into a 2-cell stage (2), an advanced cleavage stage (3), and then they embryonate (4). Eggs become infective in 15 to 30 days. After ingestion in soil-contaminated hands or food, the eggs hatch in the small intestine, and release larvae (5) that mature and establish themselves as adults in the colon (6). The adult worms (approximately 4 cm in length) live in the cecum and ascending colon. The adult worms are fixed in that location, with the anterior portions threaded into the mucosa. The females begin to oviposit 60 to 70 days after infection. Female worms in the cecum shed between 3,000 and 20,000 eggs per day. The life span of the adults is about 1 year. Courtesy of the CDC (http://phil.cdc.gov/phil/home.asp).

Distribution of soil transmitted helminths (STH) Trichuris trichiura infection prevalence in 2010 based on geostatistical models for sub-Saharan Africa and available empirical information for all other regions. Courtesy of Parasites & Vectors (Pullan RL, Smith JL, Jasrasaria R, Brooker SJ. Global numbers of infection and disease burden of soil transmitted helminth infections in 2010. Parasit Vectors. 2014;7:37).

Egg from the "human whipworm". Courtesy of the CDC (http://phil.cdc.gov/phil/home.asp).

Adult T trichiura worm removed during a colonoscopy. Courtesy of the CDC (http://phil.cdc.gov/phil/home.asp).

Life cycle of whipworm. The unembryonated eggs are passed with the stool (1). In the soil, the eggs develop into a 2-cell stage (2), an advanced cleavage stage (3), and then they embryonate (4). Eggs become infective in 15 to 30 days. After ingestion in soil-contaminated hands or food, the eggs hatch in the small intestine, and release larvae (5) that mature and establish themselves as adults in the colon (6). The adult worms (approximately 4 cm in length) live in the cecum and ascending colon. The adult worms are fixed in that location, with the anterior portions threaded into the mucosa. The females begin to oviposit 60 to 70 days after infection. Female worms in the cecum shed between 3,000 and 20,000 eggs per day. The life span of the adults is about 1 year. Courtesy of the CDC (http://phil.cdc.gov/phil/home.asp).

Distribution of soil transmitted helminths (STH) Trichuris trichiura infection prevalence in 2010 based on geostatistical models for sub-Saharan Africa and available empirical information for all other regions. Courtesy of Parasites & Vectors (Pullan RL, Smith JL, Jasrasaria R, Brooker SJ. Global numbers of infection and disease burden of soil transmitted helminth infections in 2010. Parasit Vectors. 2014;7:37).

Rectal prolapse in a female child due to a parasitic Trichuris trichiura infestation. Courtesy of the CDC (http://phil.cdc.gov/phil/home.asp).

Egg from the "human whipworm". Courtesy of the CDC (http://phil.cdc.gov/phil/home.asp).