Pathogenesis and Pathology of Mumps Virus
المؤلف:
Baijayantimala Mishra
المصدر:
Textbook of Medical Virology
الجزء والصفحة:
2nd Edition , p189-190
2025-10-26
41
Humans are the only natural host of MuV.
Mumps virus is transmitted by respiratory route or through direct contact of oral mucosa with the infected respiratory droplets, fomites or saliva. This mode of transmission is evident from (i) experimental transmission of disease by Henle and colleague to children through both oral and nasal inoculation, (ii) isolation of virus from various respiratory samples and saliva from both asymptomatic and children with parotitis and (iii) transmission among close contacts.
Mumps virus (MuV) enters the respiratory epithelial cells by binding to its receptor sialic acid. The entry of MuV to the epithelial cells occurs through both apical and basolateral sides as sialic acid is present on both these sides. This is presumed to facilitate the spreads of infection to the neighboring cells and also causes secondary viremia. The release of virus from the infected cells mostly occurs through apical side which is believed to restrict the infection to the respiratory mucosa. In case of MuV, apical release results in glandular involvement. Parotid gland is most commonly affected. Other salivary glands like sub mandibular and sublingual glands can also be affected.
After infecting the respiratory epithelial cells, virus spreads to the regional lymph nodes leading to viremia. This further spreads the virus to various extra-respiratory sites. Most of the organs of the body can be infected during viremia, though MuV has predilection for glandular organs. The organs that are commonly affected include testes, pancreas kidney, ovary, epididymis and central nervous system (CNS) (Fig.1).
Fig1. Pathogenesis of mumps
During the process of infection, MuV is present in the blood for 1–2 days. Isolation of MuV from blood has been reported but is extremely rare. The virus has been isolated from saliva and throat from 1 week prior to 1 week after the swelling of the gland and from urine till 14 days after disease onset.
Parotitis
Mumps virus infects the ductal epithelium of parotid gland. Replication of virus in parotid gland leads to perivascular and interstitial infiltration of lymphocytes, hemorrhage, edema and necrosis of acinar and periductal cells. The infected cells desquamate into the lumen of the duct. This along with lymphocytic infiltration and edema leads to blockage of salivary gland ducts and swelling of the gland.
Orchitis
Both direct infection by virus and indirect immune-mediated damage have been postulated for development of orchitis. Both Leydig and germ cells are involved. Blockage of the tubule occurs due to epithelial cell debris along with mononuclear cell infiltration and edema. This reduces the production level of testosterone. Atrophy of testicle can lead to oligospermia and reduced fertility.
CNS
MuV is a neurotropic virus. It can enter the CSF via choroid plexus or through infected mononuclear cells. This can finally lead to infection of the ependymal cells lining the ventricles and brain parenchyma. Lymphocytic infiltration of meninges occurs along with edema, gliosis, perivascular cuffing and neuronal degeneration.
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