Transcript Rubella( German measles )

Rubella( German
measles )
Etiology
• Togaviridae family --- genus Rubivirus
• single-stranded RNA enveloped virus , Its core
protein is surrounded by a single-layer
lipoprotein envelope with spike-like projections
containing two glycoproteins, E1 and E2.
• only one antigenic type
• humans are its only known reservoir
Pathogenesis and Pathology
• Transmission: respiratory droplets.
• Primary implantation and replication in the
nasopharynx are followed by spread to the lymph
nodes. Subsequent viremia occurs, which in pregnant
women often results in infection of the placenta.
Placental virus replication may lead to infection of fetal
organs.
• Individuals with acquired rubella may shed virus from 7
days before rash onset to 5–7 days
• Infants with CRS may shed large quantities of virus
from bodily secretions, particularly from the throat and
in the urine, up to 1 year of age. Outbreaks of rubella,
including some in nosocomial settings, have originated
with index cases of CRS. Thus only individuals immune
to rubella should have contact with infants who have
CRS
Clinical Features: Acquired Rubella
• Up to 50% subclinical or inapparent.
• Young chid: generalized maculopapular rash that usually lasts for up
to 3 days . The rash is usually mild and may be difficult to detect in
persons with darker skin
• older children and adults: The incubation period is 14 days (range,
12–23 days), 1- to 5-day prodrome often precedes the rash and may
include low-grade fever, malaise, and upper respiratory symptoms.
• Lymphadenopathy, particularly occipital and postauricular, may be
noted during the second week after exposure.
• arthralgia and arthritis are common in infected adults, particularly
women
•
Thrombocytopenia and encephalitis are less common complications.
• Congenital Rubella Syndrome
• infected during pregnancy(first trimester): miscarriage, fetal death,
premature delivery, or live birth with congenital defects.
• commonly relate to the eyes, ears, and heart
• Transient Manifestation: Hepatosplenomegaly , Interstitial pneumonitis,
Thrombocytopenia with purpura/petechiae (e.g., dermal erythropoiesis, or
"blueberry muffin syndrome"), Hemolytic anemia, Bony radiolucencies,
Intrauterine growth retardation, Adenopathy , Meningoencephalitis
• Permanent Manifestations: Hearing impairment/deafness,
Congenital
heart defects (patent ductus arteriosus, pulmonary arterial stenosis), Eye
defects (cataracts, cloudy cornea, microphthalmos, pigmentary
retinopathy, congenital glaucoma), Microcephaly,
Central nervous
system sequelae (mental and motor delay, autism)
Diagnosis: acquired
•
scarle fever, roseola, toxoplasmosis, fifth disease, measles, and illnesses with
suboccipital and postauricular lymphadenopathy
•
Laboratory :
•
Serology: acute: 1- IgM antibodies
2- fourfold rise in IgG antibody titer between acute- and
convalescent-phase specimens.
3- IgG avidity testing is used in conjunction with IgG testing. Lowavidity antibodies indicate recent infection. Mature (high-avidity) IgG antibodies most
likely indicate an infection occurring at least 2 months previously.
•
Rubella virus can be isolated from the blood and nasopharynx during the prodromal
period and for as long as 2 weeks after rash onset. However, as the secretion of
virus in individuals with acquired rubella is maximal just before or up to 4 days after
rash onset, this is the optimal time frame for collecting specimens for viral cultures.
•
Rubella RNA detection by reverse-transcriptase polymerase chain reaction (RTPCR) is a more recently developed technique for rubella diagnosis.
Congenital Rubella Syndrome
• infant presents with a combination of cataracts, hearing impairment, and
heart defects
• serologic assays: serum IgM antibodies may be present for up to 1 year
after birth. In some instances, IgM may not be detectable until 1 month of
age
•
rubella serum IgG titer persisting beyond the time expected after passive
transfer of maternal IgG antibody (i.e., a rubella titer that does not decline
at the expected rate of a twofold dilution per month)
• virus isolated: throat swabs and less commonly from urine and
cerebrospinal fluid. Infants with congenital rubella may excrete virus for
up to 1 year, but specimens for virus isolation are most likely to be
positive if obtained within the first 6 months after birth. Rubella virus in
infants with CRS can also be detected by RT-PCR.
Pregnant women
• screening for rubella IgG antibodies in prenatal care
• positive IgG antibody serologic test are considered immune.
• Susceptible pregnant women should be vaccinated
postpartum
• A susceptible pregnant woman exposed to rubella virus
should be tested for IgM antibodies and a fourfold rise in IgG
antibody titer between acute- and convalescent-phase serum
specimens : during the first 11 weeks of gestation, up to 90%
deliver an infant with CRS; for maternal infection during the
first 20 weeks of pregnancy, the CRS rate is 20%.
Treatment
• No specific therapy
• Symptom-based treatment
• Immunoglobulin does not prevent rubella
virus infection only in pregnant woman who
has been exposed to rubella will not consider
termination of pregnancy under any
circumstances( IM administration of 20 mL of
immunoglobulin within 72 h of rubella
exposure)
Prevention
• Rubella vaccine contains live attenuated rubella virus grown in human
diploid cells (RA 27/3). combined with measles and rubella (MR) or
measles, mumps, and rubella (MMR) formulations, tetravalent
measles, mumps, rubella, and varicella (MMRV) vaccine.
• One dose induces seroconversion in 95% of persons >1 year of age.
rubella vaccination in the United States is a first dose of MMR vaccine
at 12–15 months of age and a second dose at 4–6 years.
• Indication: children >1 year of age, adolescents and adults without
documented evidence of immunity, individuals in congregate settings
(e.g., college students, military personnel, child care and health care
workers), and susceptible women before and after pregnancy.
• women known to be pregnant should not receive an RCV. In addition,
pregnancy should be avoided for 28 days after receipt of an RCV. In
follow-up studies of 680 unknowingly pregnant women who received
rubella vaccine, no infant was born with CRS. Receipt of an RCV
during pregnancy is not ordinarily a reason to consider termination of
the pregnancy.