Rubella or German measles is a mild eruptive fever characterized by temporary spot like rash and swelling of lymph nodes. In itself, the rubella infections are minor.But when it comes to pregnant women, it may lead to congenital deformities to the baby. Congenital cataract, deafness and cardiac defects in infants is seen in maternal rubella infection cases.Rubella virus is pleomorphic in nature, with an RNA genome. It is inactivated by ether, chloroform, formaldehyde and heating at 56oC. But when kept at -60oC, it survives for several years.
It can be artificially grown in rabbit kidney cells, baby hamster kidney, etc. Experimental infections can be produced in human volunteers and monkeys. The best animal model is pregnant rabbit, in which it can infect the fetus and bring about the congenital malformations.
The incubation period is about 2-3 weeks, after which a generalized rash develops. Face is the initial site slowly spreading towards the neck and trunk. The palm and the soles are usually spared. The rash is distinct and disappears by the third day.
The posterior cervical gland becomes enlarged. The disease mainly affects children, but may affect all ages. In women, and elderly arthritis may develop. Chromosomal breakage occurs and mitosis are inhibited in infected embryonic cells.Infection is usually acquired by inhalation. The virus may be recovered from the throat for about seven days before the rash. The virus may be detected in urine and feces. Infection of the fetus is through the bloodstream.
The rubella infection in the early stages of pregnancy, may result in the death of the fetus. Congenital deformities occur if the infection happens during the first trimester. These may lead to communication defects or developmental retardation and may not be evident till the child grows older.
The virus may persist in the cataract lenses for several years. The babies sheds the virus for more than a month after the infection. They act as a major source of infection to hospital personnels.
Diagnosis is established by virus isolation and serology. Blood and throat swabs are taken as samples during the early stages. ELISA, hemagglutination, complement fixation, immunofluorescence and neutralization tests are common serological tests.Demonstration of IgM antibody, especially in pregnant women is one of the important notices for rubella infections. These women can be advised for a therapeutic abortion.
Rubella infections confer lasting immunity, as there is only one antigenic type of the virus. Since the disease is so mild, it becomes relevant only to women who are in the child bearing age. An obvious method of protection is to acquire the infection before puberty.
Live attenuated vaccines have been developed by the serial passage of the virus in tissue culture. The vaccine in use includes, RA 27/3 strain grown in human cell culture and administered by subcutaneous injection.The vaccine may also be administered in combination with MMR. The vaccine seems to be well tolerated, with minor rash formation. Immunodeficient patients should not be administered with the vaccine.Pregnancy is another important contraindication. It should be avoided for three months after vaccination.accidental administration of the vaccine to pregnant women, may not therefore lead to congenital defects in the baby.
