G.B., 15 months old, had severe vomiting and diarrhea for 12 hours and no intake
ID: 3476503 • Letter: G
Question
G.B., 15 months old, had severe vomiting and diarrhea for 12 hours and no intake of fluid or food. She began vomiting blood and was quite dehydrated and lethargic. She was taken to the hospital, admitted, and treated with intravenous fluid, electrolytes, and glucose. A fecal specimen was submitted to the laboratory for diagnosis.
The report indicated an infection with rotavirus, an RNA virus and member of the reovirus class. This virus causes gastroenteritis. The incubation period is 1 to 2 days, and the virus is transmitted by the fecal-oral route, probably at G.B.'s nursery school, where several children have been ill. The virus replicates in the epithelial cells at the tip of villi in the small intestine. This cell damage results in lack of absorption of fluid and nutrients.
1. Explain, using the pathophysiology, how the virus could cause bleeding.
2. Using your knowledge of normal physiology, explain how the vomiting and diarrhea as well as the lack of intake could affect the child physiologically.
3. Describe several factors probably contributing to transmission in this case. How long before the vomiting began was the child probably exposed to the virus?
4. What does the classification “RNA virus” mean?
5. Why is it necessary to determine the specific cause of the vomiting and diarrhea? Is any other treatment for rotavirus infection indicated?
Explanation / Answer
1. Rotaviruses, belonging to the Reoviridae family are non-enveloped viruses containing double-stranded RNA.
The virus enters and replicate in the non-dividing mature enterocytes present in the tips of the villi of the small intestine. These villus enterocytes are mature, nonproliferating cells differentiated for digestive and absorptive functions. The enterocytes involved in absorption synthesize disaccharides, peptidases and other enzymes. Bothe electrochemical or osmotic gradients and active transport by the sodium-glucose cotransporter 1 (SGLT1) transport water along with solute.
Sialic acid-containing and nonsialylated receptor molecules on the virus are involved in binding to the enterocytes. The internalization of the virus leads to loss of the outer capsid, thereby activating synthesis of the virion-associated transcriptase and viral macromolecules. There is an increase in intracellular Ca2+ concentration ([Ca2+] due to activation of viral processes, that triggers cellular processes, such as disruption of the microvillar cytoskeletal network, lowered expression of disaccharidases and other enzymes at the apical surface, general inhibition of the Na+-solute cotransport systems, and necrosis. Reduced absorption of sodium, water, and mucosal disaccharidases results in osmotic diarrhea.
In case of severe infection, excessive severe dehydration caused by diarrhea may lead to bleeding from various parts of the small intestine.
2. Rotaviral diarrhea may be associated with fever, vomiting, and dehydration that may occur alone or in combination. The infected child may have to be hospitalized for treatment. Watery stools in the child may be result of diarrhea due to fluid imbalance and loss of water and electrolytes from the small intestine. Disturbed motor activity of stomach caused by delayed emptying of fluid content may result in vomiting. Combination and vomiting results in severe dehydration. Both vomiting and diarrhea may be life threatening to the child. Higher body temperature and vomiting at the initial stage of the disease, may precede observation of loose stools. The child will be weak and if diarrhea persists, may suffer from abdominal cramps and pain. Severe dehydration may cause hyponatremia or low sodium levels that can affect the brain.
3. Incubation period of the rotavirus is around 2 days. Vomiting occurs in the child within 24-28 hrs post infection.
4. RNA viruses are viruses that have ribonucleic acid as their genetic material. RNA is double stranded in rotaviruses but in other viruses, it can be single stranded. They do not have DNA intermediates in their life cycle. RNA viruses make up class III-VI of the virus classes. Host cells do not replicate viral RNA. Hence, these viruses have transcriptase enzymes to replicate their RNA. Transcriptase enzymes may also be present in the host cell.
5. Diarrhea and vomiting in children can be due to bacterial or viral infection. In viral infection, diarrhea and vomiting is of shorter duration while it is longer in bacterial infection. In viral infections, there is increased risk of diarrhea and vomiting causing dehydration. This may cause severe effects on the brain. Bacterial infections cause more bloody stools. Viral infection cannot be treated by antibiotics. Hence, it is important to identify the source of infection as misdiagnosis may lead to death. Isolation and treatment of diarrhea by fluid rehydration will help in treatment. The child must be kept in comfortable clothing to prevent diaper rash. Probiotics may be prescribed to help regain the microbial flora lost by fluid loss, In case the child is breastfed, this method will help the child in fighting the infection due to antibodies present in the mothers milk.
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