TORCH group of infections - Cytomegalovirus

-          Causative organism: Cytomegalovirus, a ubiquitous DNA herpes virus.

-          Most common cause of perinatal infection.

-          Incidence: fetal infection found in 0.2 to 2% of all newborn infants.

Transmission:

-Horizontal transmission by droplet infection via saliva and urine.

- Vertical transmission by mother to fetus – infant.

- Sexual transmission.

- After primary infection the virus becomes latent. Periodic reactivation with viral shedding is possible despite of the presence of serum antibody.

Immunosuppressed states increase the propensity of serious cytomegalovirus infections.

Features of maternal infection:

-          No evidence that pregnancy increases the risk or severity of maternal CMV infection.

-          Most of the infections will remain asymptomatic. About 15% of the adults will have mononucleosis like syndrome.

With features like :

-          Fever

-          Pharyngitis

-          Lymphadenopathy

-          Polyarthritis.

-          The risk of sero-conversion among susceptible women during pregnancy is 1 to 4%.

-          In around 40% cases primary infection to the fetus is associated with severe morbidity.

-          Transmission is more common in first half of the pregnancy.

-          Maternal immunity to CMV does not prevent recurrence or reactivation or congenital infection.

-          Usually recurrent infections are more common cause of congenitally infected newborn.

-          Fortunately clinically apparent sequelae are less common with recurrent infections than primary infections.

Congenital infection:

-          Results in cytomegalic inclusion disease.

-          This syndrome presents with features like low birth weight, microcephaly, intracranial calcifications, chorioretinitis, mental and motor retardation, sensorineural deafness, hepatosplenomegaly, jaundice, hemolytic anemia and thrombocytopenic purpura.

-          Usually these findings are seen in 5 to 6% of infected neonates only.

Daignosis:

Infection is diagnosed by measuring IgG and IgM antibodies.

If patient results show :

-          IgG and IgM negative  - indicates Cytomegalovirus uninfected and no further evaluation is needed.

-          If abnormal Cytomegalovirus screening with IgG and IgM positives occur, following steps are needed, estimation of:

-          CMV specific IgG and IgM by EIA.

-          CMV specific IgG avidity by EIA.

-          CMV specific IgM by immunoblot.

Then if the results show:

-          CMV IgG positive, high IgG avidity index and IgM negative- latent CMV infection. And no further evaluation is needed.

-          CMV IgG positive or serocenversion, low IgG avidity index and IgM positive – primary CMV infection. Needs invasive follow-up.

-          Uncertain serologic results – undefined CMV infection. Needs invasive follow-up.

-          CMV IgG positive, high IgG avidity index and IgM positive – recurrent CMV infection. Needs non-invasive follow-up.

-Ultrasound to know the effects on the fetus. Sometimes defects like microcephaly, ventriculomegaly, cerebral calcifications, hyperechoic bowel, ascites, hepatosplenomegaly and hydrops etc. can be seen.

-Amniotic fluid analysis using viral culture and polymerase chain reaction.

-Fetal blood sampling- to detect anemia, thrombocytopenia, hepatic dysfunction etc.

-The fetal outcome depends on the stage of gestation during which primary infection documented.

-Usually the majority of infants develop normally even with being affected with primary infections in the first half of the pregnancy.

Treatment:

-No effective therapy for maternal infections. So routine serological screening is not recommended.

-Not possible to predict which fetuses are infected.

-Maternal reinfection with a different CMV strain can occur.

-No vaccine.

-Attempts to identify and isolate infants excreting  CMV are expensive and impractical.

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