Pathogenesis and Clinical Findings of Rotaviral Diseases and Laboratory Diagnosis
Pathogenesis and Clinical Findings of Rotaviral Diseases
Rotaviruses are the leading causative agents of gastroenteritis that predominantly affects infants and children before 5 years. Acute rotaviral gastroenteritis with diarrhea is a most common disease that creates the significant burden on public health worldwide but especially in developing countries. According to WHO data, it accounts for at least 500,000 children lethal cases annually.
Rotaviruses are ubiquitous. By age of 3 years, 90% of children have serum antibodies to one or more types of rotaviruses.
The source of infection is sick human.
Rotaviral infection is transmitted via fecal-oral mechanism with contact, foodborne and waterborne routs. The infant becomes infected predominantly by the direct contact with virus-contaminated fomites.
Infectious dose of virus is very low – about 100 viral particles.
Incubation period is short (1-2 days).
Rotaviruses pass through the stomach being resistant to acidic gastric juice. They infect duodenal and intestinal epithelium by binding to intestinal villi. The viruses multiply in the cytoplasm of enterocytes and impair electrolyte trans-membrane transport. One of the rotavirus-encoded proteins, NSP4, is a viral enterotoxin, which triggers diarrhea activating intestinal chloride secretion. Also it causes direct damage of enterocytes and stimulates intestinal inflammation. Damaged cells may slough into the lumen of the intestine and release large quantities of virus, which sheds with feces.
Typical symptoms of rotaviral infection include fever, abdominal pain, diarrhea and vomiting, resulting in severe dehydration.
In infants and children, severe loss of electrolytes and fluids may be fatal without compensatory infusion therapy. Patients with milder cases have symptoms for 3-8 days and then recover completely.
Viral excretion usually lasts 2-12 days. Normal function of intestine is restored only in 3-8 weeks after the disease.
Local immunity factors, such as secretory IgAs, may be important in protection against rotavirus infection.
Laboratory Diagnosis of Rotaviral Infection
As all acute viral diarrheas are similar in clinical manifestations, the diagnosis of rotaviral infection rests on laboratory testing of infection origin.
Rotaviruses are fastidious for culture; hence, laboratory diagnosis is based on virus detection in stool specimens taken early in the disease course. Molecular genetic tests (e.g., RT-PCR) play a pivotal role in rapid and precise identification of rotaviral nucleic acids in clinical specimen.
Virus in stool can be detected also by immune electron microscopy, or by ELISA.
Serological diagnosis evaluates fourfold growth of antibodies by ELISA or latex-agglutination tests.
Principles of Treatment and Prophylaxis of Rotavirus Infections
Treatment of gastroenteritis is supportive, directed to correction of water and electrolyte loss. It includes fluids resuscitation and restoration of electrolyte balance either intravenously or orally.
For specific prophylaxis of rotavirus infection two efficient live attenuated vaccines are applied (RV1 and RV5). They are successfully used in more than 80 countries. Mass vaccination of children substantially improves epidemiological situation with rotavirus infection worldwide.