MEASLES VIRUS – MORPHOLOGY, RESISTANCE, PATHOGENESIS, CLINICAL FEATURES, LABORATORY DIAGNOSIS & PROPHYLAXIS

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.

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The virus multiplies locally & in the adjoining

lymph nodes.

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Then spreads through the bloodstream to

Reticuloendothelial system.

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After multiplication, secondary viremia transports the

Virus to the epithelial surfaces.

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Koplik’s spots, small bluish-white ulceration, may be seen

on the Buccal mucosa.

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The Koplik’s spots contain Giant cells, inclusion bodies,

and virus antigen.

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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.

SAHIL BATRA

Hi, I’m the Founder and Developer of Paramedics World, a blog truly devoted to Paramedics. I am a Medical Lab Tech, a Web Developer and Bibliophiliac. My greatest hobby is to teach and motivate other peoples to do whatever they wanna do in life.