IMMUNITY
Antibody is generated after the viremia, and its appearance correlates with the appearance of the rash. The antibody limits viremic spread, but cell mediated immunity plays an important role in resolving the infection. Natural infection produces lifelong protective immunity. Serum antibody in pregnant woman prevents spread of the virus to the fetus.
CONGENITAL RUBELLA SYNDROME (CRS)
Rubella can cause congenital rubella syndrome in the newly born. The syndrome (CRS) follows intrauterine infection by Rubella virus and comprises cardiac, cerebral, ophthalmic and auditory defects. It may also cause prematurity, low birth weight, and neonatal thrombocytopenia, anaemia and hepatitis. The risk of major defects or organogenesis is highest for infection in the first trimester. CRS is the main reason a vaccine for rubella was developed. Many mothers who contract rubella within the first critical trimester either have a miscarriage or a still born baby. If the baby survives the infection, it can be born with severe heart disorders (PDA being the most common), blindness, deafness, or other life threatening organ disorders. The skin manifestations are called "blueberry muffin lesions."
CRS can result in serious birth defects such as:
malformations of the heart (especially patent ductus arteriosus), eyes or brain
deafness
spleen, liver or bone marrow problems (some of which may disappear shortly after birth)
Mental retardation
small head size (microcephaly)
eye defects (especially cataract and microphthalmia
low birth weight
thrombocytopenic purpura (presents as a characteristic "blueberry muffin" rash)
hepatomegaly
micrognathia
Children who have been exposed to rubella in the womb should also be watched closely as they age for any indication of the following:
Develpomental delay
schizophrenia
Growth retardation
Learning disabilities
Diabetes
glaucoma
LABORATORY DIAGNOSIS
Serological method – used for detection of anti-rubella-specific IgM.
A fourfold increase on specific IgG antibody titer between acute & convalescent sera is also used to indicate a recent infection.
Antibodies to rubella are assayed early in pregnancy to determine the immune status of the woman.
Virological method is used rarely.
Virus is obtained from urine and is detected by the interference with ECHO 11 virus replication in primary African green monkey kidney cell cultures.
PREVENTION
Rubella infections are prevented by active immunisation programs using live, disabled virus vaccines. Two live attenuated virus vaccines, RA 27/3 and Cendehill strains, were effective in the prevention of adult disease. However their use in prepubertile females did not produce a significant fall in the overall incidence rate of CRS in the UK. Reductions were only achieved by immunisation of all children.
The vaccine is now given as part of the MMR vaccine. The WHO recommends the first dose is given at 12 to 18 months of age with a second dose at 36 months. Pregnant women are usually tested for immunity to rubella early on. Women found to be susceptible are not vaccinated until after the baby is born because the vaccine contains live virus.
The immunization program has been quite successful with Cuba declaring the disease eliminated in the 1990s. In 2004 the Centres for Disease Control & Prevention announced that both the congenital and acquired forms of rubella had been eliminated from the United States.
TREATMENT & PROPHYLAXIS
Symptoms are usually treated with paracetamol until the disease has run its course. Treatment of newly born babies is focused on management of the complications. Congenital heart defects and cataracts can be corrected by surgery. Management for ocular CRS is similar to that for age-related macular degeneration, including counseling, regular monitoring, and the provision of low vision devices, if required.
The life rubella vaccine is usually administered with the measles and mumps vaccines (MMR vaccine). The triple vaccine is included routinely in well-baby care. Vaccination promotes both humoral and cellular immunity.
