INTRODUCTION TO MEASLES VIRUS
⇒ MEASLES VIRUS is the causative agent of disease Measles, a highly contagious viral infection of the respiratory system.
⇒ It had been described by Thomas Sydenham in 1690. Later, in 1954, it was first isolated in monkey and human kidney cells by Enders and Peebles.
⇒ Measles virus belongs to the Morbillivirus genus of Paramyxoviridae family.
MORPHOLOGY OF MEASLES VIRUS
⇒ Resembles orthomyxovirus in morphology – Spherical, Enveloped & Pleomorphic virus.
⇒ Size: 120-250 nm in diameter.
⇒ The envelope is covered by projections of H (Hemagglutinin) and F (Fusion protein).
⇒ Genetic Material:- Linear ssRNA
⇒ There is only one serotype of Measles virus.
RESISTANCE SHOWN BY MEASLES VIRUS
⇒ The measles virus is labile; readily inactivates by heat, ultraviolet light, ether, and formaldehyde; can be stabilized by MgSO4, so that it resists heating at 50°C for 1 hour.
PATHOGENESIS OF MEASLES VIRUS
⇒ The Mumps virus causes the disease mumps, an acute infectious disease characterized by non-suppurative enlargement of the parotid gland and Parotitis.
The virus enters through the Respiratory tract and
through the conjunctiva.
The virus multiplies locally & in the adjoining
Then spreads through the bloodstream to
After multiplication, secondary viremia transports the
Virus to the epithelial surfaces.
Koplik’s spots, small bluish-white ulceration, may be seen
on the Buccal mucosa.
The Koplik’s spots contain Giant cells, inclusion bodies,
and virus antigen.
2-4 days later, red maculopapular rashes appear.
CLINICAL FEATURES OF MEASLES
⇒ The incubation period of Measles virus is 9-11 days.
⇒ The initial signs of the disease include Malaise, Fever, Cough and Nasal Discharge.
⇒ After 2-4 days, rashes appear, the 1-2 day before the appearance of rashes, Koplik’s spots develop on Buccal mucosa & occasionally on the conjunctiva.
⇒ The red maculopapular rash of measles typically appears on the forehead first & spreads downwards.
LABORATORY DIAGNOSIS OF MEASLES VIRUS
⇒ Specimen: Saliva, Throat secretions, CSF and Urine.
⇒ Direct Demonstration: Giemsa stained smears of nasal secretions can show multinucleated giant cells. Viral antigen can be detected in epithelial cells of respiratory secretions and in urine.
⇒ Isolation of the virus: Virus can be isolated from saliva, Throat swab, CSF or urine by inoculating into Primary monkey Kidney and Amnion cells.
⇒ Serology: Measles-specific IgM antibodies can be detected in serum by ELISA. Hemagglutination Inhibition Test and CFT can also be done.
⇒ PCR: Reverse transcriptase PCR is a sensitive and specific method of diagnosis.
PROPHYLAXIS OF MEASLES VIRUS INFECTION
⇒ A live attenuated vaccine is available that can be administered one dose by the subcutaneous route.
⇒ It can also be administered in combination as MMR vaccine as a single dose subcutaneously.
⇒ This vaccine is given to children aged 12-15 months.
⇒ It provides effective protection for more than 20 years.