Colon
Infectious colitis
Sapovirus
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PubMed Search: Sapovirus pathology
Table of Contents
Definition / general | Essential features | Terminology | ICD coding | Epidemiology | Pathophysiology | Clinical features | Diagnosis | Laboratory | Radiology description | Prognostic factors | Case reports | Treatment | Microscopic (histologic) description | Microscopic (histologic) images | Electron microscopy description | Electron microscopy images | Molecular / cytogenetics description | Sample pathology report | Differential diagnosis | Board review style question #1 | Board review style answer #1 | Board review style question #2 | Board review style answer #2Cite this page: Fernández-Aceñero MJ. Sapovirus. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/colonsapovirus.html. Accessed September 21st, 2023.
Definition / general
- Acute gastroenteritis is one of the leading causes of death worldwide, mainly in children of developing countries
- Sapovirus can cause acute gastroenteritis in animals and humans
- Prevalence can reach 7.5% of pediatric acute gastroenteritis cases
- No reports on histological features of disease
Essential features
- Virus belonging to the Caliciviridae family, together with norovirus
- Emerging cause of acute gastroenteritis, mainly in children, even in developed countries
- Can sometimes explain both sporadic cases and outbreaks of norovirus negative acute gastroenteritis
Terminology
- Formerly called Sapporo-like virus
- The term typical human caliciviruses was discouraged by the 2002 International Committee on the Taxonomy of Viruses
ICD coding
- ICD-10: A08.31 - calicivirus enteritis
Epidemiology
- Has been detected in shellfish and environmental water (Food Environ Virol 2013;5:119)
- Can infect animals and humans of any age (Clin Microbiol Rev 2015;28:32)
- Can be a cause of sporadic cases and outbreaks, mainly in semiclosed settings (nurseries, schools)
- Prevalence has increased after the introduction of vaccination against norovirus (PLoS One 2021;16:e0255436)
- Highest prevalence in children is found in Africa followed by America and Europe but can be found anywhere
- Highest prevalence is in children < 2 years and in elderly, mainly living in care homes (J Med Virol 2016;88:1187, BMC Infect Dis 2019;20:2)
- More frequent in men (Rev Med Virol 2022;32:e2302)
- More frequent in outpatients, in contrast to norovirus (Rev Med Virol 2022;32:e2302)
- Unlike norovirus, transmission does not seem to be related to ethnicity or blood antigens (Infect Genet Evol 2015;32:396)
Pathophysiology
- Has a single stranded RNA genome with 2 open reading frames (ORF), coding viral structural proteins (VP1 in the ORF1 and VP2 in the ORF2) (Curr Opin Infect Dis 2020;33:388)
- 5 genogroups according to the sequence of VP1 and all but GIII can infect humans
- 19 genotypes: GI, 8 genotypes; GII, 8 genotypes; GIV, 1 genotype; GV, 2 genotypes
- Sapovirus particles bind to cell surface receptors then enter cells through complex, partially unknown processes and incite pathology (J Virol 2017;91:e00202)
- Can disrupt epithelial tight junctions through the RhoA-ROCK-MLC signaling pathway and by using occludin as a coreceptor (J Virol 2021;95:e00051, J Virol 2019;93:e01773)
Clinical features
- Infection can be asymptomatic (Curr Opin Infect Dis 2020;33:388)
- Most frequent clinical manifestation is acute gastroenteritis (with diarrhea and vomiting associated with constitutional symptoms) but usually not with fever (Arch Virol 2005;150:2061)
- Incubation period lasts < 1 day and disease usually resolves in 1 week (BMC Infect Dis 2013;13:446)
- Some reports link infection by enteral virus, including sapovirus, with inflammatory bowel disease (Viruses 2021;13:104)
Diagnosis
- Sapovirus was initially discovered in human diarrheic stool samples using electron microscopy in 1976 (Lancet 1976;1:199)
- No animal model is available, which makes it difficult to obtain antibodies for immune assays (PLoS One 2018;13:e0178157)
- Despite attempts to grow human sapovirus in cell culture systems, results are not reproducible yet (J Gen Virol 1984;65:1123)
- Antigen detection methods using ELISA have been developed but lack sensitivity and are not commercially available (Arch Virol 2006;151:551)
- Real time reverse transcription PCR has become the most widely used method for sapovirus detection (J Clin Virol 2006;35:321)
- Multiplex studies that can detect several enteral virus are also available (Pathology 2021;53:290)
Laboratory
- No specific abnormalities
Radiology description
- Most often appear normal
- CT scan can reveal unspecific mild colonic wall thickening (StatPearls: Viral Gastroenteritis [Accessed 30 January 2023])
Prognostic factors
- One study has found association between sapovirus in early childhood and lower cognitive scores (Clin Infect Dis 2021;73:e683)
- Acute gastroenteritis symptoms are usually milder than those caused by norovirus and other pathogens (Clin Microbiol Rev 2015;28:32)
- Immune suppression can lead to chronic diarrhea (J Clin Virol 2019;113:1)
- Mortality is very low; mainly occurs in elderly patients
Case reports
- Healthy infant male and female siblings with nearly constant viral shedding (J Clin Microbiol 2012;50:3427)
- 20 year old woman with septic shock due to severe gastroenteritis by sapovirus (Cureus 2022;14:e24010)
- 47 year old man with chronic diarrhea with kidney - pancreas transplant (Am J Kidney Dis 2021;78:A13)
Treatment
- No specific therapy is necessary, other than supportive measures for acute gastroenteritis
- Usually self limited
- Some cases require hospital admission (Infect Genet Evol 2005;5:281)
- In transplanted patients with severe diarrhea due to sapovirus, nitazoxanide has been employed with good outcome (Case Rep Infect Dis 2018;2018:6846873)
Microscopic (histologic) description
- No report of specific histologic changes in sapovirus infection
- Biopsy is not indicated
Microscopic (histologic) images
Contributed by M.J. Fernández-Aceñero, M.D., Ph.D.
Slight mucosal changes in sapovirus infection
Electron microscopy description
- Sapovirus was discovered in diarrheic human stool by electron microscopy
- Morphology is similar to other caliciviruses
- Small icosahedral particles (30 - 38 nm) with cup shaped depression on the surface
- Typical Star of David morphology (Clin Microbiol Rev 2015;28:32)
- Partially replaced by molecular techniques, although some outbreaks caused by previously unreported genotypes have been resolved with electron microscopy (Euro Surveill 2017;22:30543)
Electron microscopy images
Images hosted on other servers:
Typical morphology of sapovirus
Molecular / cytogenetics description
- There are many tools that can help identify the pathogens that lead to acute diarrhea
- The performance of multiplex PCR testing is better than isolated tests
- Assays that employ the FilmArrayTM technology can detect 22 of the most frequent gastrointestinal pathogens through rapid PCR multiplexing (BMC Microbiol 2017;17:111)
Sample pathology report
- Colon, endoscopic biopsy:
- Active colitis (see comment)
- Comment: Colonic mucosa with inflammatory expansion of the lamina propria by lymphocytes and plasma cells, associated with slight crypt architectural distortion and few neutrophils. No granulomas or viral inclusions. No dysplasia. The histopathological image is nonspecific and can be associated with drugs, inflammatory bowel disease and bacterial, viral or parasitic infections. Diagnosis should be based on the synthesis of clinical, microbiological and endoscopic data.
Differential diagnosis
- Inflammatory bowel disease (IBD):
- Typical clinical and endoscopic features of IBD
- Biopsy should show continuous crypt distortion, cryptitis and intraluminal microabscesses limited to the mucosa in ulcerative colitis
- Typical skip lesions, with deep fibrosing ulcers associated or not associated with granulomas or pyloric metaplasia in Crohn's disease
- Microscopic colitis:
- Chronic watery diarrhea with no endoscopic lesions
- Lymphocytic colitis should show intraepithelial CD8+ lymphocytes
- Collagenous colitis should be associated with a thickened basement membrane
- Irritable bowel disease, diarrhea associated variant:
- Largely a diagnosis of exclusion
- No biopsy is indicated except to rule out other disorders
- Drug adverse effects:
- Clinical features are important
- Apoptosis of epithelial cells and intraepithelial lymphocytes are more prominent (Am J Surg Pathol 2015;39:1653)
- Other viral causes of diarrhea:
- Adenovirus:
- Usually immune depression
- Typical viral inclusions
- Can be confirmed with immunohistochemistry (Gastroenterology 1991;100:976)
- Cytomegalovirus:
- Typical viral inclusions
- Many other causes can only be diagnosed with a molecular analysis of stool samples
- Adenovirus:
- Parasites:
- Can usually be identified in the biopsy samples
- Bacterial causes of diarrhea:
- Usually, active colitis with edema and hemorrhage
- Clinical features and microbiological studies can help diagnosis
Board review style question #1
A 4 year old girl attending a daycare center is brought to hospital by her parents with diarrhea and abdominal pain lasting 2 days, without fever. She was vaccinated against norovirus. Her vital signs are normal. Which of the following is true regarding this patient?
- Biopsy is needed to confirm diagnosis
- Electron microscopy of a stool sample is mandatory for diagnosis
- She must be hospitalized immediately
- The symptoms will disappear in a few days with no therapy
Board review style answer #1
D. The symptoms will disappear in a few days with no therapy. Most viral infections disappear spontaneously with no further therapy. Answer A is incorrect because biopsy is not indicated in acute diarrheal diseases. Answer B is incorrect because while it was once the gold standard for diagnosis, electron microscopy has largely been replaced by molecular techniques that are more reliable. Answer C is incorrect because hospitalization need is guided by the clinical situation of the patient. In this case, vital signs were within normal limits.
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Board review style question #2
Which of the following techniques is most useful for diagnosis of sapovirus infection?
- Biopsy
- Complete blood count
- Molecular techniques
- Serology
Board review style answer #2
C. Molecular techniques. Answers A, B and D are incorrect because in the diagnosis of sapovirus infection, there are no serological assays, no specific analytical abnormalities and no indication for biopsy.
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