Paramyxoviruses ( mumps , measles , rubella) Flashcards
What familiy & genus is mumps in
genus: orthorubulavirus
Family: paramyxovirinae
what is the portal of entry for mumps
nasal & upper respiratory tract epithelial cells
whats the inucbattion period for mumps
2-4 weeks
What is the pathogenesis for mumps
• primary infections occurs in(portal of entry) nasal & upper respiratory tract epithelial cells
• Viremia disseminates virus to salivary glands + major systems epithelial cells ( i.e kidneys - can be detected in urine)
• Virus is shed in saliva from 3 days before & 9 days after onset of salivary gland swelling
• virsus may persist for 12 days after onset of symptoms
which salivary gland does mumps commonly infect
parotid gland
give some distinguishable characteristics of mumps
- has hemagluttinin glycoprotien & fusion protein & neuroaminidase
- single serotype
- acute self limited viral infection
- humans are only host
- no cross immunity w other paramyxoviruses
epidemiology of mumps ? - how is mumps transmitted
- airborne droplets /direct contact (very close )
- fomites(e.gclothing,utensil) contamited w saliva / urine
epidemiology of mumps? - who are likely to be infected with mumps
- children 5-9 years
- can also occur in adolescents & adults
why is it difficult to control transmission of mumps
- variable incubation periods
- large number of asymptomatic cases
- presence of virus in saliva before clinical symptoms develop
which organ does mumps frequently infect & how can it be detected
- kidney
- virus is present in urine
What are the clinical presentations of mumps
1.Parotitis(unilateral/bilateral) - swelling of parotid gland + pain
what are complications of mumps
- aseptic meningitis- MC in male than female
-
Meningoencephalitis = occurs 5-7days after inflammation of salivary gland - most dont present w parotitis
*these 2 usually resolve w/o sequelae**
3.Orchitis(unilateral) - in 20-50% of youngmales who develop mumps
4.oophoritis
5.Pancreatitis
6.myocarditis
7.arthritis
8.uveitis
9.deafness - guillain-barre syndrome
Immunity to mumps
- one attack (clinical/subclinical) induces life long immunity
- one antigenic type ( one serotype) w no variation
- antibodies to NP (nucleocapsid) protein appear earliest(3-7daysafter onset of clinical symptoms) - usually gone within 6months
- antibodies to HN develop more slowly (4wks after onset) - persist for years
- cell mediated immune response
- interferon induced early on in infection
- IgA antibodies secreted in nasopharynx exhibit neutralizing activity
- passive immunity from mother to offspring (rare to see mumps in children younger than 6months)
How mumps be diagnosed in lab ?
1.PCR - sensitive
2Culture : .saliva , CSF , urine (virus can be recovered for up to 2 wks) collected within few days after onset
nB : after collection inoculation done immediate since mump virus is thermoliable
- cytopathic effect: cell rounding & giant cell formation*
- hemadsoprtion test used to show presence of hemadsorbing agent 1 & 2 , weks after incoulation
-monkey kidney cells are preferred for viral isolation
- immunofluorescence via specific serum used for rapid diagnosis - as early as 2-3days after inoculation
3. serology
- fourfold or greater rise in antibody titer is evidence of mumps infection
- ELISA - detect IgM antibodies or IgG antibodies / HI test MC used
(IgM indicates recent infection - persist not longer than 60days)
Epidemiology of mumps
- children 5-9years
- outbreaks can occur = especially during crowding
- Children younger than 5 = Respitatory tract infection w/o parotitis
- highly contagious
which gene of mumps of variable
SH gene : allowing for classification of known virus strains into 12 genotypes
Treatment
live attenuated virus mumps vaccine
Control of mumps virus
difficult due to high incidence of asymptomatic cases
children acquire mumps in school & work - should not go in until 5days after onset of parotitis
MMR vaccine
- mumps , measles , rubella vaccine -
2 doses are recommended for school entry
2 doses of vaccine given to health care worker born before 1957 w/o evidence of mumps immuntiy
What causes rubella (disease)
Rubivirus rubellae
Which virus (genus) is rubella (disease ) caused by ? and which familiy is it in
family: matonaviridae (was previously in togaviridae family )
genus: rubivirus
structure of rubivirus
- spherical 940-80nm)
- (+)ssRNA
- enveloped
- has glycoproteins spikes E1 &E2
what are the two types of rubella
- Postnatal rubells - causes mild disease
- Congenital rubella syndrome - quite severe
Pathogenesis of postnatal rubells
Entry : respiratory epithelium
- invades the respiratory mucosa
- initial replication in RT
- then multiplication in cervical lymph nodes
- Viremia develops after 7-9 days - last till antibody appearance on day 13-15
(antibody appearance = coincides w rash appearance)
- secondary viremia (occurs 1-3wks after infection )
- dissemination to other organs (liver/spleen) , skin & mucosa
Epidemiology
- transmitted by respiratory route
- not a contagious
- occurs in neonates , childhood , adult
what is the incubation period of postnatal rubella
12-21 days
how is it spread
airdroplets /direct contact
clinical findings postnatal rubella
- Non-specific signs : malaise & lowgrade fever
- Morbilliform rash - starts on face, then trunk , extremeties (lasts not more than 3 days)
- maculopapular rash
- centrifugal
- disappears affter 3-5 days
- Forchheimer sign (20% of patients) - pinpoint lesions/petechiae in soft palate
4.suboccipital lymphadenopahty
complications of postnatal rubella
- arthralgia(joint pain)
- arthritis (fingers, wrist /knees) - common in women
- thrombocytopenic purpura
- encephalitis
Immunity of postnatal rubella
- antibodies appear in serum as rash fades - & rises rapidly over next 1-2 wks
- intitial antibody = IgM - not beyond 6wks after illness - indicate recent rubella infection
- IgG antibodies persist for life
- one attack incurs life long immuniy
- only one antigenic type of virus exists
- immune mothers transfer antibodies to their offsrping who are then protected for 4-6months
Lab Diagnosis of rubella
- PCR /culture - by acquring nasopharyngeal/ throat swabs taken 6 days before & after onset of rash
other sources of sample virus : urine , CSF , blood , cord blood
for culture = cell lines of monkeys & rabbits can be used
2.Serology
- HI test - requires pretreament for emoval of nonspecific inhibitors
- ELISA test - no pretreatment & can detect IgM
NB detection of IgG is evidence of immunity cos there is only one serotype of rubivirus
How to accurately confirm recent rubella infection esp in pregnant women ?
- rise in antibody titer(HI antibody) must be seen btwn 2 serum samples taken 10 days apart
- rubella specific IgM detected in single specimen
Treatment of rubivirus + control
- no speciific treatment - since its mild & self limited
- live attenuated rubella vaccine (single antigen / combine w measles & mumps vaccine)
(induces lifelong immunity for at least 95% of ppl)
role of vaccine : prevent congenital rubella infections
Pathogenesis of congenital rubella
- maternal viremia associated w rubella in pregnancy can cause infection of placents & fetus
- Destroys fetal cells & inhibits mitosis(growth rate reduced)
lead to hypoplastic organ devt = structural anomalies in newborn - time of infection determines teratogenic effect
( early in pregnancy = greater damage to fetus - esp 1st trimester = 85%cases of abnormalities)
(birth defect uncommon if maternal infection occurs after 20th wk of gestation)
what are the 3 categories used to group congenital rubella ?
- transient effects in infants
- permanent manifestations that may be apparent at birth / are recognised during the 1st year
- developmental abnormalities that appear & progress during childhood & adolescence
what is the classic triad of congenital rubella
cataract
cardiac abnormalities(patent ductus arteriosus)
deafness
other clinical findinds in congenital rubella
- transient symptoms of ;
- growth retardation
- rash
- hepatosplenomegaly
- jaundice
- meniningoencephalitis - progressive rubella panencephalitis - develops in second decade of life in child w congenital rubella
diagnosis of congenital rubella
- isolation of virus in cell culture of throat sample , urine & other secretions
- detection of IgM in single serum sample shortly after birth(IgM des not cross placenta ,theri presence indicates that they must be synthesized by the infant in utero)
- persistance of rubella IgG antibodies in serum beyond 1 year or rising anitbody titre anytime during infancy in an unvaccinated child
-biopsy of tirrue/blood /CSF for viral antigen by monoclonal antibodies - detection of rubella RNA by insitu hybridization & PCR
Treatment & prevention of congenital rubella
no specific treatment
prevention: childhood immunization w rubella vaccine to ensure that women of childbearing age are immune
