Lect 6 a measles, mumps and rubella
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Transcript of Lect 6 a measles, mumps and rubella
Measles, Mumps & Rubella (MMR)
• Infections with measles, mumps and rubella viruses are confined to man and occur worldwide.
• Spread primarily via the aerosol route. • Each of these viruses exists as a single serotype• MMR vaccine contains all three of these viruses• .Measles & Mumps belong to family
Paramyxovirus• RNA enveloped viruses
Measles & Mumps
MEASLES (RUBEOLA) PATHOGENESIS AND DISEASE
• The word measles is derived from German word for blister
• Respiratory droplet infection. • Virus replicates in the upper/lower respiratory tract and
lymphoid tissues leading to viremia and then growth in a variety of epithelial sites.
• The virus is very contagious: maximum contagiousness is 2 to 3 days before onset of the rash.
• The disease develops 1 - 2 weeks after infection.
Clinical Features• Measles is still a major killer in
underdeveloped countries • Fever of 101oF (38.3o C) or above• Running nose (coryza) and cough• Conjunctivitis• Koplik's spots on mucosal
membranes - small (1 - 3mm), irregular, bright red spots, with bluish-white speck at center.
• Maculopapular rash which extends from face to the extremities.
• The infection is prostrating but recovery is usually rapid
Clinical Features
Complications of Measles
• Secondary bacterial infections: otitis media and bacterial pneumonia.
• Pneumonia accounts for 60% of deaths from measles
• Encephalitis (1 in 1000 cases) a few days after the rash disappears.
Subacute Sclerosing Pan encephalitis• Very rare (7 in 1,000,000 cases) • Develops 1 to 10 years after the initial infection. • Behavioral changes. • Impaired speech, vision and swallowing • A progressive, usually fatal disease • SSPE is associated with defective forms of the
virus in the brain
Complications of Measles
• Measles can cause temporary defects in the immune response; e.g. tuberculin-positive individuals may temporarily give a negative response.
Complications of Measles
LAB DIAGNOSIS
• The clinical picture • Serodiagnosis
o IgM & IgG levels
• Virus isolation in cell cultureo The large syncytia, or multinucleated
giant cells, result from fusion of cell membranes
o Inclusion bodies, eosinophilic areas of altered staining in the cytoplasm
EPIDEMIOLOGY• Almost all infected individuals show signs
of disease. • Only one serotype of measles and a single
natural infection gives life-long protection.
MMR Vaccine • Is a live, attenuated combined vaccine to
prevent measles, mumps and rubella. • Two doses are given to pre-school
children: o The first dose at 12-15 months o The second booster dose at 3-5 years
PREVENTION
PREVENTION & TREATMENT
• Immune serum globulin: for at risk patients during an outbreak i.e. those <1 year with impaired cellular immunity
o No antiviral therapy available for primary disease. Complications should be treated appropriately
MUMPS
• The name comes from the British word "to mump", that is grimace
• Clinically, mumps is an acute unilateral or bilateral parotid gland swelling that lasts for more than two days with no other apparent cause.
Other agents can also cause parotitis
Mumps Pathogenesis
Mumps Epidemiology
Reservoir Human
Transmission Respiratory droplet infection
Communicability 7 days before to 9 days after
onset of active disease
• Worldwide distribution
•Many (30%) infections are sub-clinical
•No 'carrier state'.
Clinical Aspects of Mumps
• Fever• Parotitis• Meningitis & encephalitis• Orchitis• Pancreatitis • Myocarditis• Nephritis• Arthritis
Mumps Complications
CNS involvement 15% of clinical cases
Orchitis 20-50% in
post-pubertal males
Pancreatitis 2-5%
Deafness 1/20,000
Death 1-3/10,000
MMR Vaccine • Is a live, attenuated combined vaccine to
prevent measles, mumps and rubella. • Two doses are given to pre-school
children: o The first dose at 12-15 months o The second booster dose at 3-5 years
PREVENTION & TREATMENT
Rubella (German Measles)
History
1881Rubella accepted as a distinct disease 1941Associated with congenital disease
Rubella virus first isolated 1961 1967Serological tests available
1969Rubella vaccines available
Rubella Virus
RNA enveloped virusMember of the togavirus family
Spreads by respiratory droplets In the pre-vaccination era, 80% of women were already infected by childbearing age
Clinical Features
Rubella: Latin “little red”Maculopapular rash
Lymphadenopathy
Fever
Arthropathy (up to 60% of cases)
Rash of Rubella
Risks of Rubella Infection During Pregnancy
Preconception :Minimal risk
0-12 weeks: 100% risk of fetus being congenitally infected
resulting in major congenital abnormalities. Spontaneous abortion occurs in 20% of cases .
13-16 weeks: Deafness and retinopathy 15% After 16 weeks: Normal development, slight risk of
deafness and retinopathy
Congenital Rubella Syndrome
Classical triad consists of:
CataractsHeart defects Sensorineural deafness .
TransientLow birth weight, hepatosplenomegaly, thrombocytopenic purpura, meningoencephalitis, hepatitis, haemolytic anemia, pneumonia, lymphadenopathy
PermanentSensorineural deafness, Heart defects, Eye defects (retinopathy, cataract, microopthalmia, glaucoma), diabetes mellitis
DevelopmentalSensorineural deafness, Mental retardation
Congenital Rubella Syndrome
Outcome
1/3 rd will lead normal independent lives
1/3 rd will live with parents
1/3rd will be institutionalised
The only effective way to prevent CRS is to terminate the pregnancy
Laboratory Diagnosis
Diagnosis of acute infectionPresence of rubella-specific IgM
Rising titres of antibody (mainly IgG)
Typical Serological Events following acute rubella infection
Note that in reinfection, IgM is usually absent or only present transiently at a low level
Prevention
Antenatal screening
Screening of all pregnant women attending antenatal clinics for immune status against rubella.
Non-immune women are vaccinated in the immediate post partum period.
Prevention
Since 1968, a highly effective live attenuated vaccine has been available with 95% efficacy
Universal vaccination is now offered to all infants as part of the MMR regimen in the USA, UK and a number of other countries.
Vaccination of schoolgirls before they reach childbearing age.