In this article we will discuss about Rubella (German Measles):- 1. Subject-Matter of Rubella (German Measles) 2. Virology of Rubella Virus 3. Pathogenesis and Clinical Features 4. Epidemiology 5. Immunity 6. Control.
Contents:
- Subject-Matter of Rubella (German Measles)
- Virology of Rubella Virus
- Pathogenesis and Clinical Features of Rubella
- Epidemiology of Rubella
- Immunity of Rubella
- Control of Rubella
1. Subject-Matter of Rubella (German Measles):
Rubella or German measles virus is a sole member of the Rubi virus genus under to gaviridae family. It is discussed with Paramyxo virus as it forms rash of German measles similar to measly rash. Rubella is a mild childhood fever characterised by transient macular rash and posterior circular and sub-occipital lymphadenopathy.
Exposure of the foetus in early (first trimester) pregnancy to rubella infection may result into congenital malformation. Rubella may be acquired congenitally or postnatally.
2. Virology of Rubella Virus:
Rubella virus is pleomorphic, 50-70 nm, enveloped, RNA virus.
It agglutinates goose, pigeon, day-old chick & human RBC at 4°C.
It grows in rabbit kidney cell line-RK 13 and in embryonated duck egg.
3. Pathogenesis and Clinical Features of Rubella:
A. Post-natal rubella:
Infection is acquired through mucosa of upper respiratory tract. The virus replicates locally, followed by multiplication in the cervical lymph nodes, after an incubation period of 2 to 3 weeks. Viraemia occurs with fever. These viruses are disseminated in the target organs with the formation of rash suggesting an immunological reaction.
Macular rash appears on the face, then trunk and legs and lasts for less than 3 days. Infection in children is asymptomatic and common in children than in adults. Transient arthralgia and arthritis occur in about 60% women but uncommon in children. Post-infectious encephalomyelitis, thrombocytopenic purpura are rare complications.
B. Congenital rubella:
During viraemia, rubella virus crosses the placental barrier and replicates in the differentiating cells of the embryo and infects a limited number of cells in affected organs. The foetal cells are not destroyed by the virus. In the first trimester of pregnancy, the risk is common (50-70%), followed by second trimester (20%), and only 4% in 7th month of pregnancy.
Abnormalities of eyes (cataract); ears and heart are the classical rubella syndrome.
Diagnosis:
A. Post-natal rubella:
1. Isolation:
Virus in blood or throat swabs can be grown in various tissue culture cell lines of monkey or rabbit kidney. CPE is not inconspicuous.
2. Serology:
ELISA is the method of choice to detect rubella specific Ig G or Ig M.
B. Congenital Rubella:
1. Isolation of virus can be done from the pharyngeal secretion or urine for first 4 months of life.
2. Serology:
Demonstration of rubella-specific Ig M is diagnostic of intra-uterine infection.
4. Epidemiology of Rubella:
Rubella is worldwide in distribution and is endemic in all countries when the vaccination is not successful. Epidemics occur every 5-6 years in spring and are transmitted by respiratory route. In-apparent maternal infection can cause foetal anomalies. Congenitally infected infants can transmit the infection to others.
5. Immunity of Rubella:
One attack of rubella confers life-long immunity; immune mother can transmit antibodies to breast fed infants for 4-6 months.
6. Control of Rubella:
Since 1989, a combined measles-mumps-rubella (MMR) vaccine has been advocated. This vaccine is given in two doses. Pregnant women are not vaccinated.