GASTROINTESTINAL INFECTIONS









Bacterial diarrhea

Definition

  • Acute diarrhea < 7 days
  • Prolonged diarrhea 7 - 13 days
  • Persistent diarrhea 14 - 29 days
  • Chronic diarrhea ≥ 30 days

Etiology

Causes of diarrhea in the U.S. (annual cases / 100,000 people)
  • Noroviruses - most common cause of diarrhea in adults and children
  • Salmonella - 16.4
  • Campylobacter - 14.3
  • Shigella - 2.3
  • Shiga toxin–producing Escherichia coli - 1.1
  • Enterotoxigenic E. coli
  • Vibrio - 0.4
  • Yersinia - 0.3

Symptoms

  • Noroviruses - sudden onset of vomiting and nonbloody diarrhea; outbreaks may occur in nursing homes, hospitals and cruise ships; most common cause of foodborne infections; incubation period 10 - 51 hours; duration of illness is 1 - 4 days
  • Salmonella (nontyphoidal) - acute onset of watery diarrhea and fever; bloody diarrhea may occur; 95% of cases are foodborne (e.g. poultry or hen's eggs); nontyphoidal Salmonella is common in the U.S.; Salmonella Typhi causes a severe systemic infection (Typhoid fever) marked by fever and abdominal pain. It is uncommon in the U.S. but may be seen in travelers returning from endemic areas (Asia).
  • Campylobacter jejuni - sudden onset of watery diarrhea; fever and bloody diarrhea are common; foodborne transmission in 80% of cases; many infections occur during international travel (traveler's diarrhea)
  • Shigella - severe diarrhea; fever and bloody diarrhea are common; only a small inoculum is required for infection, so spreads easily; may be foodborne or waterborne
  • Shiga toxin–producing E. coli (enterohemorrhagic E. coli, E. coli O157:H7) - watery diarrhea progressing to bloody diarrhea; most commonly acquired from food (ground beef or produce); may also spread person-to-person and in water; can cause a hemolytic-uremic syndrome that may be worsened by antibiotic treatment
  • Enterotoxigenic E. coli - acute watery diarrhea; causes nearly half of cases of traveler's diarrhea; often foodborne
  • Vibrio vulnificus - associated with raw shellfish and seafood ingestion; watery diarrhea that may become bloody; Vibrio cholerae is associated with cholera outbreaks in areas with unclean water
  • Yersinia enterocolitica - acute watery diarrhea; may cause fever and bloody diarrhea; associated with a pseudo-appendicitis syndrome; seen most often in Canada and Scandinavia
  • Clostridium difficile (C. diff) - diarrhea that may be bloody; typically seen in patients with recent exposure to antibiotics (within 3 months); most common cause of diarrhea in healthcare settings (e.g. hospital); elderly patients are most affected
  • Traveler's diarrhea - abrupt onset of diarrhea while traveling; typically caused by Campylobacter jejuni or Enterotoxigenic E. coli
  • Diarrhea accompanied with significant vomiting - typically caused by a viral gastroenteritis [1,2,3,4,5]

Stool testing

Overview
  • Stool leukocyte testing is not recommended because it does not help establish the etiology of infectious diarrhea
  • Stool cultures have low yield and are not recommended in mild-to-moderate diarrhea
  • In symptomatic patients, stool cultures identify a pathogen in less than 50% of patients in most studies
  • One stool sample is typically sufficient when looking for a bacterial pathogen. Sample should be processed within 4 hours after passage when performing microscopy, and within 12 hours for cultures.
  • Yersinia and Vibrio are not included in a standard stool culture and must be ordered separately
  • For cases of bloody diarrhea, it is important to test for the presence of Shiga toxin to help identify Shiga toxin–producing E. coli
  • Follow-up testing is not recommended in most people [1,2,3,4,5,30]
Indications for stool cultures in outpatients
  • Acute, severe diarrhea with fever (≥ 38.5°C, 101.3°F) lasting greater than 48 hours
  • Bloody diarrhea
  • Recent antibiotic exposure (check for C. difficile)
  • Persistent diarrhea (≥ 14 days) - also check for parasites
Routine stool cultures and bacterial stool pathogen panels typically test for:
  • Salmonella
  • Shigella
  • Campylobacter
  • Enterohemorrhagic E coli (detects Shiga toxin)
C. difficile testing
  • For patients with recent antibiotic exposure / hospitalization, testing for C difficile should be performed
  • C difficile testing is usually done in steps and includes the following:
    • Glutamate dehydrogenase (GDH) EIA - GDH is an enzyme secreted by Clostridium species. This test is typically performed first. It has a high sensitivity, but cannot differentiate between toxin-producing and non toxin-producing strains of Clostridium.
    • NAAT toxin gene test (PCR) - Nucleic acid amplification test that detects the genes that encode for C. difficile toxins. This test is more sensitive than the toxin EIA test. It may be performed alone or after a positive GDH test. It may also be performed if GDH is positive and toxin EIA is negative because it is more sensitive than toxin EIA.
    • Toxin EIA test - Enzyme immunoassay (EIA) that detects the presence of C. difficile toxins A and B. This test is not as sensitive (42 - 84% depending on the test) as NAAT testing. This test is usually performed if the GDH test is positive. If GDH and toxin EIA are positive, then C. difficile infection is likely. If GDH is positive and toxin EIA is negative then NAAT gene testing may be indicated. [30,32]

Treatment overview

Watery diarrhea
  • In most people with acute watery diarrhea and without recent international travel, empirical antimicrobial therapy is not recommended
  • Empirical treatment should be avoided in people with persistent watery diarrhea lasting 14 days or more
Bloody diarrhea
  • See stool testing above
  • In immunocompetent children and adults, empiric antimicrobial therapy for bloody diarrhea while waiting for results of testing is not recommended
  • If empiric treatment is used, therapy in adults should be either a fluoroquinolone or azithromycin, depending on risk factors. Empiric therapy for children includes a third-generation cephalosporin (infants < 3 months of age) or azithromycin, depending on risk factors.
Antimotility agents (e.g. loperamide)
  • May be used in adults
  • Do not give to children < 18 years old [28]

Treatment regimens

Campylobacter species
  • Pediatric
    • Azithromycin 10 mg/kg/day (max 500 mg/day) given once daily for 3 - 5 days [CTE] ($)
    • Erythromycin base 30 mg/kg/day (max 2000 mg/day) given in 2 - 4 divided doses for 3 - 5 days [CTE] ($$$-$$$$)
  • Adults
Clostridium difficile (C. difficile) (See C. difficile testing for more)
  • Pediatric
    • Initial episode, non-severe
      • Metronidazole 7.5 mg/kg/dose (max 500 mg/dose) 3 - 4 times a day for 10 days [IDSA] ($)
      • Vancomycin 10 mg/kg/dose (max 125 mg/dose) by mouth 4 times a day for 10 days [IDSA] ($$$$)
    • First recurrence, non-severe
      • Metronidazole 7.5 mg/kg/dose (max 500 mg/dose) 3 - 4 times a day for 10 days [IDSA] ($)
      • Vancomycin 10 mg/kg/dose (max 125 mg/dose) by mouth 4 times a day for 10 days [IDSA] ($$$$)
  • Adults
    • Initial episode, non-severe (WBC ≤ 15,000; SCr < 1.5 mg/dl)
      • Vancomycin 125 mg by mouth 4 times a day for 10 days [IDSA] ($$$$)
      • Fidaxomicin (Dificid®) 200 mg two times a day for 10 days [IDSA,PI] ($$$$)
      • Alternative (less preferred): Metronidazole 500 mg 3 times a day for 10 days [IDSA] ($)
    • Initial episode, severe (WBC > 15,000; Scr > 1.5 mg/dl)
      • Vancomycin 125 mg by mouth 4 times a day for 10 days [IDSA] ($$$$)
      • Fidaxomicin (Dificid®) 200 mg two times a day for 10 days [IDSA,PI] ($$$$)
    • First recurrence
      • Vancomycin 125 mg by mouth 4 times a day for 10 days if metronidazole was used for first episode
      • Fidaxomicin (Dificid®) 200 mg two times a day for 10 days if vancomycin was used for first episode
      • Also consider prolonged/tapered vancomycin regimen - 125 mg 4 times per day for 10 – 14 days, 2 times per day for a week, once per day for a week, and then every 2 or 3 days for 2 – 8 weeks
E. Coli enterotoxigenic species
  • Pediatric
    • Azithromycin 10 mg/kg/day (max 500 mg/day) given once daily for 3 days [CTE] ($)
    • Ceftriaxone 50 mg/kg/day IM/IV given once daily for 3 days [CTE] ($)
    • Rifaximin 200 mg three times a day for 3 days. Approved for ≥ 12 years old. [PI] ($$$$)
  • Adults
E. Coli hemorrhagic species (Shiga toxin-producing, E. coli O157:H7)
  • Antibiotics are contraindicated
Salmonella species (nontyphoidal)
  • Pediatric
    • Mild-Moderate disease - treatment is not routinely recommended
    • Severe disease or high-risk patients (see below)
      • Azithromycin 20 mg/kg/day given once daily for 7 days [CTE] ($)
      • Ceftriaxone 100 mg/kg/day IV given in 2 divided doses for 7 - 10 days [CTE] ($)
      • Sulfamethoxazole-trimethoprim 10 mg/kg/day (trimethoprim component) given in 2 divided doses for 5 - 7 days [IDSA] ($)
  • Adults
    • Mild-to-moderate disease - treatment is not routinely recommended
    • Severe disease or high-risk patients (see below)
    • High-risk defined as having one of the following:
      • Age < 6 months or > 50 years
      • Heart valve disease including prosthetic heart valve
      • Severe coronary artery disease
      • Cancer
      • Kidney failure
      • Immunosuppression
      • Significant joint disease
Shigella species
Vibrio vulnificus
  • Pediatric
    • Azithromycin 10 mg/kg/day (max 500 mg/day) given once daily for 3 days [CTE] ($)
    • Ceftriaxone 50 mg/kg/day IM/IV given once daily for 3 days [CTE] ($)
  • Adults
Yersinia enterocolitica

Diverticulitis

Pathology

  • Diverticulosis is a condition where outpockets form along the surface of the colon (typically the sigmoid colon). The outpocketings have a narrow neck that may become obstructed by fecal material. When obstruction occurs, inflammation of the outpocketing may develop (diverticulitis).
  • If only inflammation of the colon wall is present, diverticulitis is considered uncomplicated. About 75% of diverticulitis cases are uncomplicated. If abscess, stricture, perforation, obstruction, or fistula is present, diverticulitis is considered complicated.

Epidemiology

  • The presence of diverticulosis increases with age with a prevalence of 10% in people < 40 years old, and 50 - 70% among people ≥ 80 years old
  • It is estimated that 20% of people with diverticulosis will develop diverticulitis over the course of their lifetime
  • 80% of diverticulitis cases occur in patients who are ≥ 50 years old

Risk factors

  • Increasing age
  • Low dietary fiber
  • Family history
  • Lack of exercise
  • Obesity
  • NSAIDs
  • smoking
  • Constipation
  • Red meat consumption

Symptoms

  • Left lower quadrant pain
  • Constipation
  • Fever
  • Elevated white count (leukocytosis) present in 55% of cases

Diagnosis

  • In mild cases, clinical diagnosis is often made
  • For more severe cases or when there is concern for complications, CT scan has a sensitivity of 93 - 97%, and a specificity close to 100%
  • CT findings consistent with diverticulitis include thickening of the colonic wall, pericolonic fat stranding (indicating edema or inflammation), abscesses, localized air bubbles, and free air or fluid

Recurrence

  • Recurrence rates after first episode of uncomplicated diverticulitis are between 10 - 30% over ten years
  • Recurrent attacks of uncomplicated diverticulitis are no longer an indication for elective colectomy as diverticulitis does not appear to be a progressive disease

Colonoscopy

  • Complicated diverticulitis - colonoscopy is recommended 6 - 8 weeks after resolution
  • Uncomplicated diverticulitis - colonoscopy after uncomplicated diverticulitis does not appear to be necessary in most patients

Prevention of recurrent diverticulitis

  • No preventative treatment has been proven effective in a large randomized controlled trial
  • Possible beneficial strategies include the following:
    • High-fiber diet
    • Smoking cessation
    • Weight loss
    • Exercise
    • Avoidance of nuts, corn, and popcorn (found to have no benefit in a large prospective study) [22,23,24,25,26,31]

Treatment

Uncomplicated diverticulitis
  • Observation - several randomized controlled trials have found that observation without antibiotics is equally effective as antibiotics in uncomplicated diverticulitis [PMID 22290281, PMID 27686365]
Common antibiotic regimens (duration 7 - 14 days)

Helicobacter pylori (H. pylori)

Overview

  • H. pylori is a gram negative bacteria that resides in the stomach lining
  • It is usually acquired during the first few years of life and persists thereafter unless treated
  • At least 50% of the world's population is infected with H. pylori. In the U.S., the estimated prevalence of H. pylori infection is around 30%. It is more common in Asians and people from Central and South America.
  • H. pylori causes no symptoms in the majority of infected individuals, but it is associated with an increased risk of a number of GI conditions

Associated conditions

  • Duodenal and gastric ulcers - ulcers occur in 1 - 10% of patients infected with H. pylori. H. pylori eradication reduces the risk of recurrent duodenal ulcers by about 33% and the risk of recurrent gastric ulcers by around 25%.
  • Gastric cancer - gastric cancer occurs in 0.1 - 3% of patients infected with H. pylori. It is unclear if treating H. pylori infection is effective in the primary prevention of gastric cancer. A study among patients with gastric cancer who were infected with H. pylori found that H. pylori treatment decreased the risk of recurrent gastric cancer [PMID 29562147].
  • Gastric MALT lymphoma - MALT lymphoma occurs in < 0.01% of patients infected with H. pylori. Treating H. pylori achieves tumor regression in 60 - 90% of patients with localized MALT lymphoma.
  • GERD and dyspepsia - there is no conclusive evidence that treating H. pylori infection improves GERD or dyspepsia symptoms
  • Iron deficiency anemia - some studies have suggested an association between iron deficiency anemia and H. pylori infection while others have not. The ACG recommends testing adults with unexplained iron deficiency anemia for H. pylori.

Whom to test (ACG 2017)

Testing recommended
  • Active PUD or history of PUD
  • Early gastric cancer
  • MALT lymphoma
  • Patients initiating chronic treatment with NSAIDs
  • Patients with unexplained iron deficiency anemia
  • Adults with immune thrombocytopenia
Consider testing
  • Patients < 60 years old with dyspepsia
  • Patients taking long-term daily aspirin therapy
Routine testing not recommended
  • Patients with typical GERD symptoms
  • Asymptomatic patients with family history of gastric cancer
  • Patients with hyperplastic gastric polyps

Diagnostic tests

Overview
  • The three main noninvasive tests for H. pylori are the serologic H. pylori antibody (IgG) test, the urea breath test, and the fecal antigen test. When endoscopy is performed, testing can be performed on biopsies from the procedure.
  • For noninvasive testing, the ACG recommmends the urea breath test or the fecal antigen test over the serologic antibody test, because the antibody test will remain positive for years after exposure and is therefore not specific for active infection
  • When testing for cure after treatment, only the urea breath test and the fecal antigen test should be performed
Test preparation
  • Patients who are going to have the urea breath test or the fecal antigen test should stop PPIs and bismuth preparations 2 weeks before the test (some guidelines recommend 30 days). Not stopping these therapies may lead to false-negative tests.
  • H2 antagonists (e.g. Pepcid) may be taken during this period but they should be stopped 24 hours before the test
Testing for cure
  • Testing for cure is recommended in all patients. Testing should be performed ≥ 30 days after the completion of treatment and test preparation as described above should be followed.
Tests
  • H. pylori antibody (IgG) - tests for IgG antibodies to H. pylori | sensitivity 85% and specificity 79% in some studies | cannot be used to confirm treatment success
  • Urea breath test - test involves drinking C-labeled urea which is converted to CO2 by H. pylori urease. Labeled CO2 is then measured in a breath sample. | sensitivity and specificity reported as 95%
  • Fecal antigen test - detects H. pylori antigen in the stool | sensitivity and specificity reported as 95% for monoclonal antibody test | test is much cheaper than urea breath test
  • Endoscopic testing - tests are performed on biopsies taken during endoscopy; tests include urease-based testing, histological assessment, and culture

Treatment success rates


Treatment Treatment success in clinical trials
PPI + clarithromycin + amoxil or metronidazole 70 - 85%
Bismuth + metronidazole + tetracycline + PPI 75 - 90%
Levaquin + amoxil + PPI 87%
Sequential therapy 84 - 93%


Recurrence

  • In studies, H. pylori recurrence has been observed at an annual rate of 4.3% in treated individuals
  • Recurrence is more common in developing countries and in areas with a higher prevalence of infection. [29]
  • Retreatment is appropriate in patients with peptic ulcer disease, MALT lymphoma, and gastric cancer. The benefit of retreatment in other patients is unclear. [19,20,21,27,33]

Treatment regimens

Pediatric
  • PPI + Amoxicillin 50 mg/kg/day (max 2000 mg/day) given in 2 divided doses + Clarithromycin 20 mg/kg/day (max 1000 mg/day) given in 2 divided doses. Treat for 10 - 14 days. [CTE] ($$-$$$)
  • PPI + Amoxicillin 50 mg/kg/day (max 2000 mg/day) given in 2 divided doses + Metronidazole 20 mg/kg/day (max 1000 mg/day) given in 2 divided doses. Treat for 10 - 14 days [CTE] ($$-$$$)
  • Sequential therapy
    • Days 1 - 5: PPI + Amoxicillin 50 mg/kg/day (max 2000 mg/day) given in 2 divided doses
    • Days 6 - 10: PPI + Clarithromycin 20 mg/kg/day (max 1000 mg/day) given in 2 divided doses + Metronidazole 20 mg/kg/day (max 1000 mg/day) given in 2 divided doses. [CTE] ($$-$$$)
Adults (ACG 2017)
PPI dosing for H. pylori treatment
  • Omeprazole (Prilosec®)
    • Children ≥ 1 year: 1 - 1.2 mg/kg/d given in 2 divided doses [PMID 9200377, 16285942]
    • Adults: 20 mg twice daily
    • How supplied: 2.5, 10 mg powder for suspension | 10, 20, 40 mg capsule
  • Lansoprazole (Prevacid®)
    • 13 - 22 kg: 15 mg once daily
    • 23 - 45 kg: 15 mg twice daily [PMID 19166421]
    • Adults: 30 mg twice daily
    • How supplied: 15, 30 mg capsule | 15, 30 mg disintegrating tablet
    • Capsules and tablets can be mixed or dissolved in food. See Prevacid® PI sec 2.3 for instructions.
  • Esomeprazole (Nexium®)
    • Children (> 15 kg): 1.5 mg/kg/day (max 40 mg/day) given once daily [PMID 21407111]
    • Adults: 40 mg once daily
    • How supplied: 20, 40 mg capsule | 2.5, 5, 10, 20, 40 mg powder for suspension
  • Pantoprazole (Protonix®)
    • Adults: 40 mg twice daily
    • How supplied: 20, 40 mg tablet | 40 mg granules for suspension
  • Rabeprazole (Aciphex®)
    • Adults: 20 mg twice daily
    • How supplied: 20 mg tablet | 5, 10 mg sprinkle capsule
Prepackaged treatments
  • Prevpac®: lansoprazole (Prevacid®) 30 mg twice a day + amoxicillin 1000 mg twice a day + clarithromycin 500 mg twice a day for 14 days ($$$$)
  • Pylera®: omeprazole (Prilosec®) 20 mg twice a day + Pylera® capsule (bismuth 140 mg / metronidazole 125 mg / tetracycline 125 mg) 3 capsules 4 times a day for 10 days ($$$$)

Cryptosporidium parvum

Overview

  • Epidemiology - Cryptosporidium is a protozoan parasite that is passed through person-to-person contact, waterborne outbreaks (drinking water and swimming pools), and infected animals (newborn calves and lambs); an estimated 748,000 cases occur annually in the United States
  • Symptoms - average incubation period is about 7 days; watery diarrhea is the most prominent symptom; mild fever, abdominal cramps, nausea and vomiting may occur; duration of symptoms is typically 7 - 14 days; infection is usually self-limited in immunocompetent patients; recurrent episodes of diarrhea can occur for up to 30 days
  • Diagnosis
    • Stool studies for ova and parasites (O&P) - organism is viewed under a microscope; identifying Cryptosporidium requires special preparation techniques that may not be performed on a standard stool study and may not be available; sensitivity is improved with 3 serial stool samples
    • Cryptosporidium enzyme immunoassay (EIA) - test performed on stool; higher sensitivity and specificity than stool studies [6,9,12]

Treatment

Pediatric
  • Mild-to-moderate disease - treatment is not routinely recommended
  • Severe disease
    • Nitazoxanide (Alinia®)
      • 1 - 3 years: 5 ml (100 mg) twice a day with food for 3 days [CDC/PI] ($$$)
      • 4 - 11 years: 10 ml (200 mg) twice a day with food for 3 days [CDC/PI] ($$$)
Adults
  • Mild-to-moderate disease - treatment is not routinely recommended
  • Severe disease
    • Nitazoxanide (Alinia®) 500 mg twice a day for 3 days [CDC/PI] ($$$$)

Cyclospora cayetanensis

Overview

  • Epidemiology - Cyclospora is a coccidian parasite that is passed through food and water contaminated with feces; In the U.S., the most common source of infection is imported fresh produce (raspberries, basil, snow peas, and mesclun lettuce)
  • Symptoms - incubation period is 2 - 11 days (average 7 days); symptoms include watery diarrhea, loss of appetite, abdominal cramping and bloating, nausea and vomiting; symptoms may last for weeks; infection is self-limited in most patients
  • Diagnosis
    • Stool studies for ova and parasites (O&P) - organism is viewed under a microscope; identifying Cyclospora requires special preparation techniques that may not be performed on a standard stool study and may not be available; sensitivity is improved with 3 serial stool samples
    • Cyclospora PCR - test performed on stool; detects parasite DNA in stool; not widely available; higher sensitivity and specificity than stool studies [6,9]

Treatment

Pediatric
Adults

Entamoeba histolytica (Amebiasis)

Overview

  • Epidemiology - Entamoeba histolytica is a protozoan parasite that is passed through food and water contaminated with feces; Entamoeba dispar is a similar parasite that does not cause disease and is far more common than E. histolytica; an estimated 500 million people worldwide are infected with Entamoeba, and most of these cases are E. dispar; under microscopic exam, both organisms look the same
  • Symptoms 80 - 90% of infections are asymptomatic and self-limited; incubation period is typically 2 - 4 weeks; symptoms include diarrhea, abdominal pain, and cramping. In more severe cases, colitis with bloody diarrhea and fever may develop; liver abscess may occur in disseminated disease, but this is rare (1% of cases)
  • Diagnosis
    • Stool studies for ova and parasites (O&P) - organism is viewed under a microscope; sensitivity is improved with 3 serial stool samples; E. histolytica and E. dispar are indistinguishable under a microscope
    • E. histolytica enzyme immunoassay (EIA) - test performed on stool; test can distinguish between E. histolytica and E. dispar; higher sensitivity and specificity than stool studies
    • E. histolytica (Amebiasis) antibody titer - test performed on serum; typically ordered to identify etiology of liver abscess; has low sensitivity for intestinal amebiasis [6,7,8]

Treatment

Pediatric
  • Treatment includes systemic agent followed by luminal agent
    • Systemic agents
    • Luminal agents
      • Paromomycin 25 - 35 mg/kg/day (max 1500 mg/day) given in 3 divided doses for 5 - 10 days [PI] ($-$$)
Adults
  • Treatment includes systemic agent followed by luminal agent. Asymptomatic intestinal colonization may be treated with a luminal agent only.
    • Systemic agents
      • Metronidazole 750 mg 3 times a day for 5 - 10 days [IDSA/CTE] ($)
      • Tinidazole 2000 mg once daily for 3 days [PI] ($-$$)
    • Luminal agents
      • Paromomycin 500 mg 3 times a day for 7 days [IDSA] ($-$$)

Giardia intestinalis | G. duodenalis | G. lamblia

Overview

  • Epidemiology - Giardia is a flagellated protozoan that is primarily passed through water that has been contaminated with fecal material from animals or humans; an estimated 2.5 million cases of giardiasis occur annually in the U.S.
  • Symptoms - symptoms typically appear between 6 - 15 days after infection; symptoms include fatty, yellowish diarrhea, weight loss, and abdominal pain; in most cases, the infection is self-limited with a duration of 2 - 4 weeks; a significant portion of people (30 - 50%) will develop chronic infection with intermittent diarrhea
  • Diagnosis
    • Stool studies for ova and parasites (O&P) - organism is viewed under a microscope; organism sheds intermittently therefore sensitivity is improved with 3 serial stool samples (85 - 90%)
    • Giardia lamblia enzyme immunoassay (EIA) - test performed on stool; test has high sensitivity (> 90%) and specificity (95 - 100%) [6,9,10,11]

Treatment

Pediatric
  • Metronidazole 5 mg/kg/dose (max 250 mg/dose) 3 times a day for 7 - 10 days [CTE] ($)
  • Nitazoxanide (Alinia®)
    • 1 - 3 years: 5 ml (100 mg) twice a day with food for 3 days [PI] ($$$)
    • 4 - 11 years: 10 ml (200 mg) twice a day with food for 3 days [PI] ($$$)
  • Tinidazole (3 years and older) 50 mg/kg (max 2000 mg) given as a one time dose [PI] ($)

Adults
  • Metronidazole
    • 250 mg - 750 mg 3 times a day for 7 - 10 days [IDSA] ($)
    • 500 mg twice a day for 5 - 7 days [CTE] ($)
  • Nitazoxanide (Alinia®) 500 mg twice a day for 3 days [CTE/PI] ($$$$)
  • Tinidazole 2000 mg given as a one time dose [CTE/PI] ($)

Ancylostoma braziliense | Ancylostoma caninum | Uncinaria stenocephala | Zoonotic hookworms

Overview

  • Epidemiology and pathology - Zoonotic hookworms are spread from dogs and cats to humans. Infected dogs and cats shed eggs in their feces. Under proper conditions (moisture, warmth, shade), eggs can form larvae in the soil. When humans come in contact with the larvae, the larvae penetrate the skin. In most cases, zoonotic hookworms cannot mature further in humans, and they migrate aimlessly in the epidermis. This migration causes a red, raised eruption to develop in the skin (cutaneous larva migrans). The eruption may move in the skin as the larvae migrates. The larvae will die after 5 - 6 weeks. In the U.S., zoonotic hookworm infections are most commonly seen in people returning from tropical climates.
  • Symptoms
    • Skin invasion - intense itching at the site of infection. Cutaneous larva migrans - skin eruption with snake-like form that may migrate over days.
    • Other - in rare cases, larvae may migrate to the intestine and lungs and cause eosinophilic enteritis and eosinophilic pneumonitis, respectively
  • Diagnosis - zoonotic hookworm infection is a clinical diagnosis based on history (travel to tropical region), symptoms (intense itching), and characteristic rash (cutaneous larva migrans). There are no serological tests to aid in the diagnosis.
  • Treatment - larvae in the skin typically die in 5 - 6 weeks, therefore the infection is usually self-limited. Treatment with ivermectin and albendazole may be indicated to control symptoms. [6]

Treatment

Pediatric
Adult
  • Albendazole 400 mg once daily for 3 - 7 days [CDC] ($$$$)
  • Ivermectin 200 mcg/kg as a single dose [CDC] ($)

Ancylostoma duodenale and Necator americanus (Hookworms)

Overview

  • Epidemiology and pathology - hookworm is a helminth that is spread through contaminated soil. Hookworm infections affect an estimated 740 million people worldwide. Humans infected with hookworm shed eggs in their feces. Soil contaminated with feces serves as a medium for eggs to mature into larvae. Larvae then attach to and invade the skin of bare-footed humans (or other skin surfaces that come in contact) who walk on the soil. The larvae migrate to the lungs through the bloodstream where they penetrate the alveoli and ascend the bronchial tree to the pharynx. The larvae are swallowed and end up in the small intestine where they mature into adults and attach to the intestinal lining.
  • Symptoms
    • Skin invasion - may cause itching of feet or hands
    • Lung symptoms - occur within 10 days after skin invasion; cough and sore throat; eosinophilia of lungs
    • Intestinal symptoms - typically asymptomatic; microcytic, hypochromic anemia develops over time because worms suck blood from the intestinal wall; hypoproteinemia may develop; eosinophilia may be present on blood tests; heavy worm burden may produce gastrointestinal symptoms (e.g. abdominal tenderness, nausea)
  • Diagnosis
    • Stool studies for ova and parasites - eggs may be visualized under a microscope; examination of the eggs cannot distinguish between N. americanus and A. duodenale [6,15]

Treatment

Pediatric
  • Albendazole (≥ 6 years old) 400 mg given as a one time dose [CDC] ($$$$)
  • Mebendazole 100 mg twice daily for 3 days or 500 mg given as a one time dose [CDC] ($$$$)
  • Pyrantel pamoate (available over-the-counter) 11 mg/kg/day (max 1000 mg/day) given once daily for 3 days [CDC] ($)
Adults
  • Albendazole 400 mg given as a one time dose [CDC] ($$$$)
  • Mebendazole 100 mg twice daily for 3 days or 500 mg given as a one time dose [CDC] ($$$$)
  • Pyrantel pamoate (available over-the-counter) 11 mg/kg/day (max 1000 mg/day) given once daily for 3 days [CDC] ($)

Ascaris lumbricoides | Ascariasis | Roundworm

Overview

  • Epidemiology and pathology - Ascaris lumbricoides is a roundworm that is spread through contaminated soil. Ascaris lumbricoides infection affects an estimated 30 - 100 million people worldwide. Humans infected with Ascaris shed eggs in their feces. The infection is spread when food sources contaminated with feces are consumed. The eggs turn into larvae in the intestine. They then invade the wall of the intestine and are carried to the lungs via the bloodstream. In the lungs, larvae penetrate the alveoli, ascend the bronchial tree, and are swallowed in the pharynx. In the small intestine, they mature into adult worms and produce eggs. The process takes between 2 - 3 months from egg ingestion to mature worm. Adult worms may live for 1 - 2 years and can reach lengths of up to 35cm
  • Symptoms - typically asymptomatic; lung migration may cause cough, shortness of breath, and other nonspecific respiratory symptoms; intestinal symptoms are usually mild abdominal discomfort; heavy infections may lead to malabsorption syndromes and intestinal blockage
  • Diagnosis
    • Stool studies for ova and parasites - eggs may be visualized under a microscope; stool concentration techniques may improve sensitivity
    • Worms in stool - adult worms are occasionally passed in the stool and are easily visualized [6, 17]

Treatment

Pediatric
Adults
  • Albendazole 400 mg given as a one time dose [CDC] ($$$$)
  • Ivermectin 150 - 200 mcg/kg given as a one time dose [CDC] ($)
  • Mebendazole 100 mg twice daily for 3 days or 500 mg given as a one time dose [CDC] ($$$$)

Pinworms | Enterobius vermicularis | Enterobiasis

Overview

  • Epidemiology - Enterobius vermicularis is a helminth (worm). Eggs from the worm are deposited around the anus of infected individuals. The eggs may then be carried to common surfaces like hands, toys, bedding, etc. through direct contact. Individuals who come into contact with these surfaces may ingest the eggs and become infected; pinworm eggs can survive in the indoor environment for 2 - 3 weeks; pinworm infections typically affect children and their caregivers; pinworms are the most common type of helminth infection in the U.S.; enterobiasis is a term meaning pinworm infection
  • Pathology - once ingested, eggs hatch in the stomach and upper intestine; the female worm then matures and migrates to the colon; at night, the female migrates outside the anus and deposits her eggs on the perianal skin; the time from egg ingestion to female deposition of eggs around the anus is about 1 month
  • Symptoms - most common symptom is itching around the anus; many infections are asymptomatic; severe cases may cause abdominal pain
  • Diagnosis
    • Direct observation - worms may be seen in anal region 2 - 3 hours after the infected person goes to sleep
    • Cellophane tape test - in the morning, prior to patient going to the bathroom or washing, the skin around the anus is patted with the sticky side of a piece of transparent (no frost) tape. The tape is then affixed to a glass slide. The slide is then observed under a microscope to look for eggs and/or parts of female worms. Test should be performed on three consecutive mornings to increase sensitivity.
    • Fingernail samples - if patient has scratched bare anus, samples from under the fingernails may be evaluated under a microscope to look for eggs and/or parts of female worms
    • Stool studies - eggs and worms are not typically found in stool. Stool exams are not recommended. [6,11,12,13]

Treatment

Pediatric
  • Albendazole 10 - 14 mg/kg (max 400 mg) given as a one time dose. May repeat in 2 weeks. [CTE] ($$$)
  • Ivermectin 200 mcg/kg given as a one time dose and repeated in 10 days [PMID 15344847, 18452885, 2929853] ($)
  • Mebendazole 100 mg one time dose. May repeat in 2 weeks. [PI] ($$$$)
  • Pyrantel pamoate (Pin-X®, Reese's Pinworm medicine®, etc.) - available over-the-counter in numerous products. Treat according to product labeling. ($)
Adult
  • Albendazole 400 mg given as a one time dose. May repeat in 2 weeks. [CTE] ($$$$)
  • Ivermectin 200 mcg/kg given as a one time dose and repeated in 10 days [PMID 15344847, 18452885, 2929853] ($)
  • Mebendazole 100 mg one time dose. May repeat in 2 weeks. [PI] ($$$$)
  • Pyrantel pamoate (Pin-X®, Reese's Pinworm medicine®, etc.) - available over-the-counter in numerous products. Treat according to product labeling. ($)

Schistosoma species | S. mansoni | Schistosomiasis | Bilharzia | Flatworm

Overview

  • Epidemiology and pathology - Schistosomiasis is caused by a flatworm. An estimated 230 million people are infected worldwide. Infected individuals shed eggs in their feces and urine. Eggs that reach freshwater will hatch releasing ciliated miracidia that can infect snails. In the snail, the parasite replicates and sheds cercariae (infective larvae) into the water. Cercariae that come in contact with humans penetrate the skin. In humans, cercariae migrate through several tissues eventually reaching the portal blood in the liver where they mature into worms. Worms migrate to the mesenteric veins where they produce eggs. Schistosoma mansoni and S. japonicum typically reside in the mesenteric veins of the intestines while S. haematobium most often resides in the venous plexus of the bladder. The incubation period for an infection can range from 14 - 84 days. Worms live an average of 3 - 10 years.
  • Symptoms
    • Acute infection - may be asymptomatic; fever, malaise, myalgia, headache, eosinophilia, fatigue and abdominal pain lasting 2–10 weeks may occur (Katayama syndrome)
    • Chronic infection - symptoms are caused by immune reactions to the eggs; eggs lodged in the blood vessels of the liver or intestine can cause diarrhea, constipation, and blood in the stool. Chronic inflammation can lead to bowel wall ulceration, liver fibrosis, and portal hypertension; S. haematobium eggs tend to lodge in the urinary tract causing dysuria, hematuria, obstructive uropathy, and bladder cancer.
  • Diagnosis
    • Stool studies for ova and parasites - S. mansoni and S. japonicum eggs may be visualized under a microscope; three samples should be collected to increase sensitivity
    • Urine studies for ova and parasites - S. haematobium eggs may be visualized under a microscope; three samples should be collected to increase sensitivity; peak egg excretion occurs between noon and 3PM
    • Schistosoma antibody, IgG - performed on blood; should not be drawn until 6 - 8 weeks after likely infection; cannot distinguish between active infection and past infection [6,12,18]

Treatment

General
  • Treatment should be initiated at least 6 - 8 weeks after exposure
  • Repeat treatment may be needed in 2 - 4 weeks
  • Follow-up urine or stool exam should be performed 1 - 2 months post-treatment
Pediatric (≥ 4 years old)
  • S. mansoni, S. haematobium, S. intercalatum
    • Praziquantel 40 mg/kg/day given in 2 divided doses for 1 day [CDC] ($$$)
  • S. japonicum, S. mekongi
    • Praziquantel 60 mg/kg/day given in 3 divided doses for 1 day [CDC] ($$$)
Adults
  • S. mansoni, S. haematobium, S. intercalatum
    • Praziquantel 40 mg/kg/day given in 2 divided doses for 1 day [CDC] ($$$$)
  • S. japonicum, S. mekongi
    • Praziquantel 60 mg/kg/day given in 3 divided doses for 1 day [CDC] ($$$$)

Strongyloides | Strongyloidiasis | Roundworm

Overview

  • Epidemiology and pathology - Strongyloides stercoralis is a roundworm that is spread through contaminated soil. Strongyloides infection affects an estimated 30 - 100 million people worldwide. In the U.S., 0 - 6.1% of persons sampled are infected, and up to 46% of immigrant populations are infected; humans infected with strongyloides shed larvae in their feces. When soil contaminated with feces comes in contact with human skin, the larvae attach and invade the skin. The larvae migrate to the lungs through the bloodstream where they penetrate the alveoli and ascend the bronchial tree to the pharynx. The larvae are swallowed and end up in the small intestine where they mature into adults. In the intestine, they become threaded within the intestinal lining and produce eggs which turn into larvae. These larvae may "autoinfect" the host through the intestinal mucosa or perianal skin. The cycle of autoinfection may persist for many years.
  • Symptoms
    • Skin invasion - may cause itching at site of skin invasion; autoinfection may produce a rash called larva currens - a recurrent, snake-like, red, raised eruption that occurs along the buttocks, perineum, and thighs
    • Lung symptoms - typically asymptomatic; tracheal irritation, cough, shortness of breath, transient lung infiltrates may be seen
    • Intestinal symptoms - typically asymptomatic; stomach pain, heartburn, bloating, intermittent diarrhea, nausea, loss of appetite may be seen
    • Hyperinfection - a disseminated infection may occur in immunocompromised patients that leads to multi-organ infection and has a high mortality rate
  • Diagnosis
    • Stool studies for ova and parasites - larvae may be visualized under a microscope; serial stool exams are often required to increase sensitivity (≥ 3); specialized stool exams may increase sensitivity
    • Duodenal aspirate and biopsy - has a high sensitivity
    • Bronchoalveolar lavage - larvae may be seen on wet mount
    • Serum antibody tests (IgG) - high sensitivity; antibodies cross-react with other parasites (schistosomes, Ascaris lumbricoides) therefore have low specificity; does not necessarily indicate acute infection [6,16]

Treatment

General
  • Repeat stool exam should be performed 2 - 4 weeks after treatment to confirm clearance of infection
Pediatric
Adults
  • First-line
    • Ivermectin 200 mcg/kg given once daily for 1 - 2 days [CDC] ($)
  • Alternative
    • Albendazole 400 mg twice a day for 7 days [CDC] ($$$$)

Taenia saginata (Tapeworms)

Overview

  • Epidemiology - Taenia saginata, T. solium, and T. asiatica are tapeworms that infect humans through the consumption of undercooked beef (T. saginata) or pork (T. solium, T. asiatica); the worm attaches to the wall of the small intestine and can live there for years; eggs and proglottids from the worm are shed in the stool; Taeniasis is a term for intestinal tapeworm infection; T. solium may also cause an infection called cysticercosis (see below) which is different than taeniasis
  • Cysticercosis - Cysticercosis is an infection caused by T. solium. It occurs when larval cysts infect brain (neurocysticercosis), muscle, and other tissues. Cysticercosis infection occurs when humans consume food contaminated with the feces of individuals with intestinal T. solium infections. Cysticercosis infection does not occur from eating raw or undercooked pork; cysticercosis can lead to seizures, muscle damage, and eye damage
  • Symptoms - Taeniasis typically has no symptoms or very mild symptoms (abdominal pain, distension, diarrhea); T. solium tapeworm segments often go unnoticed in stools where T. saginata segments are typically seen because they are much larger
  • Diagnosis
    • Worms in stools - worm and worm segments can be examined if they are found in the stool
    • Stool studies for ova and parasites - Taenia eggs may be visualized under a microscope; 3 consecutive specimens should be obtained; eggs can be difficult to visualize, therefore this test has a low sensitivity
    • Coproantigen detection assays - tests that detect Taenia antigens in stools; have high sensitivity and specificity; not widely available
    • Cysticercosis antibody testing (IgG) - test is performed on serum; detects antibodies to Taenia solium; supports diagnosis of cysticercosis [6,14]

Treatment

General
  • Treatment recommendations are for taeniasis infections, not cysticercosis
  • After treatment, stools should be collected for 3 days to search for tapeworm proglottids for species identification
  • Stools should be re-examined for Taenia eggs 1 and 3 months after treatment to be sure the infection is cleared
Pediatric
  • Praziquantel 5 - 10 mg/kg given as a one time dose [CDC] ($$$)
  • Niclosamide 50 mg/kg given as a one time dose [CDC] (currently not available in U.S.)
Adults
  • Praziquantel 5 - 10 mg/kg given as a one time dose [CDC] ($$$)
  • Niclosamide 2000 mg given as a one time dose [CDC] (currently not available in U.S.)

Trichuris trichiura | Trichuriasis | Whipworm

Overview

  • Epidemiology and pathology - Trichuris trichiura is a whipworm that is spread through the fecal-oral route. An estimated 600 - 800 million people are infected worldwide. Infected persons shed eggs in their stools. Eggs mature in the soil and become infective in 15 - 30 days. Infection occurs when food or other sources contaminated with feces are consumed. After consumption, eggs hatch in the small intestine and release larvae that mature in the colon. Adult worms are about 4cm in length, and they live in the cecum and ascending colon. Females begin producing eggs about 60 - 70 days after infection. The worms live for about 1 year. The swine whipworm Trichuris suis does not mature in humans, although the larvae can briefly colonize the colon. Trichuris suis larvae are believed to have anti-inflammatory properties and has been studied in the treatment of Crohn's disease.
  • Symptoms - light infections typically have no symptoms; heavy infections are marked by colitis causing passage of painful, frequent stools that contain mucus, water, and blood. Rectal prolapse may occur.
  • Diagnosis
    • Stool studies for ova and parasites - eggs may be visualized under a microscope; stool concentration techniques may improve sensitivity [6,17]

Treatment

Pediatric
Adults
  • Albendazole 400 mg given once daily for 3 days [CDC] ($$$$)
  • Ivermectin 200 mcg/kg given once daily for 3 days [CDC] ($$)
  • Mebendazole 100 mg twice daily for 3 days [CDC] ($$$$)



Pricing legend
  • $ = 0 - $50
  • $$ = $51 - $100
  • $$$ = $101 - $150
  • $$$$ = > $150
  • Pricing based on one month of therapy at standard dosing in an adult
  • Pricing based on information from GoodRX.com®
  • Pricing may vary by region and availability