Acute diarrhea in children

The differential diagnosis for acute diarrhea includes 

• bacterial

• parasitic

• viral 

Invasive diarrhea:  fecal leukocytes present

• Salmonella

• Shigella 

• Campylobacter spp. 

• Entamoeba histolytica are less likely, although certainly possible. 

The leading parasitic possibilities include 

• Giardia

• Cryptosporidium spp., especially if this child was in a day-care center. 

The viruses that can cause gastroenteritis include

• Rotavirus (most frequent)

• Enteric coronaviruses 

• Unclassified small round viruses

• Norwalk and Norwalk-like viruses. Norwalk virus infections can result in community outbreaks of diarrheal illness primarily in adults.

• Enteric adenovirus

• Calicivirus

• Astrovirus

Rotavirus 

 Etiology

• Rotavirus is a member of the family Reoviridae (double strand RNA viruses with segmented genomes).

  • Group A rotavirus is the most common diarrheal pathogen seen in children less than 5-years-old in the United States. 

    • Illness occurs sporadically and not in widespread outbreaks. 

  • Group B rotavirus has caused a large outbreak of diarrheal disease in Chinese adults, but is very uncommon in the United States.

Life cycle of the virus

Clinical Manifestations:

• The clinical spectrum varies from asymptomatic infection to severe disease.

• It generally is self-limited, lasting approximately 1 week in most cases. 

• Infection can result in diarrhea, usually preceded or accompanied by emesis and fever.

• Immunocompromised children, including those with human immunodeficiency virus infection, persistent infection can develop.

• This disease is often referred to as "winter vomiting disease". 

• It may be responsible for as many as 50% of pediatric hospitalizations during the winter.

Pathogenesis

• Rotary virus causes a malabsorptive diarrhea (diarrhea can be reduced by stopping oral feedings)

• The virus causes blunting of and atrophy of small intestininal villi (2-4 days), which results in reduced absorptive capacity.

• Rotavirus also encodes a viral enterotoxin (NSP4). The viral enterotoxin is responsible for the acute initial diarrhea.

Epidemiology:

• Prevalence

  • Most common cause of nosocomially acquired diarrhea in children and is an important cause of acute gastroenteritis in children attending child care. 

  • Worldwide, Rvs are the single most common agent of severe diarrhea in children younger than 2 years of age and, in developing countries, are a major cause of dehydration and death.

  • In North America, the annual epidemic peak characteristically starts in the autumn in Mexico and the southwest United States, moving sequentially to reach the northeast United States and maritime Canada by spring. 

  • Specific seasonal patterns in tropical climates are less pronounced.

• Transmission

  • Most human infections result from contact with infected persons. Spread within families and institutions is common. 

  • Infections due to Rv occur in many animal species, but transmission from animals to humans has not been documented. 

    • Rotavirus is present in stool before the onset of diarrhea and can persist for 10 to 12 days after the onset of symptoms in normal hosts. Rotavirus is present in high titer in stools of patients with diarrhea, which is the only body specimen consistently positive for the virus. Transmission is presumed to be by the fecal-oral route. 

    • Rotavirus can be found on toys and hard surfaces in child care centers, indicating that fomites may serve as a mechanism of transmission.

    • Respiratory transmission also may have a role in disease transmission. 

  • Following exposure to Rv, the incubation period usually is from 1 to 3 days.

  • Virtually all children are infected by 3 years of age. 

• Reinfection

  • Reinfections are common and tend to be milder than first infections. 

  • From 30% to 50% of adult contacts of infected infants have reinfections, although only a minority manifest symptoms.

  • Type specific immunity is generated in response to roravirus infection, which provides partial protection from another infection. However , at least 4 serotypes of rotavirus exist, hence a patient can get re-infection.

Diagnostic Tests:

• Enzyme immunoassay (EIA) and latex agglutination assays for group A Rv antigen detection in stool are available commercially and are rapid tests. 

  • However, EIAs are more sensitive for the detection of antigen late in the course of illness. 

  • Both assays have high specificity, but false-positive and nonspecific reactions can occur in neonates and in persons with underlying intestinal disease. 

  • These nonspecific reactions can be distinguished from true positive ones by the performance of confirmatory assays.

• Virus also can be identified in stool by electron microscopy and by specific nucleic acid amplification techniques

  • It was named for its characteristic wheel-like ("rota") morphological appearance on EM.

  • Viral isolation is not routinely performed in a clinical laboratory because it is inefficient, and too time consuming

Treatment:

• No specific antiviral therapy is available.

• Oral or parenteral fluids are given to prevent and correct dehydration. 

• Orally administered human immunoglobulins given as an investigational therapy in immunocompromised patients with prolonged infections have reduced viral shedding and shortened the duration of diarrhea.

• Enteric isolation of the Hospitalized Patient:

  • Strict hand-washing and use of gloves for health care workers.

  • In view of the prolonged fecal shedding of low concentration of virus after recovery, continuation of contact precautions for the duration of hospitalization can be justified, particularly if transmission can occur to immunocompromised and premature infants.

• Child Care.

  • General measures for interrupting enteric transmission in child care centers are recommended

  • Children with Rv diarrhea in whom stool cannot be contained by diapers or toilet use should be excluded from child care centers until diarrhea ceases. 

  • Surfaces should be washed with soap and water. 

  • A 70% ethanol solution will inactivate Rv and may help prevent disease transmission resulting from contact with environmental surfaces.

• Vaccines.

  • A vaccine to prevent Rv infection and disease is not available. 

  • Previous successful vaccine was withdrawn because of adverse incidence of intussusceptions. A modified vaccine is in trial use for premature infants.