Molecular characterization of indigenous measles virus clades in Tamilnadu, identification of transmission pathways and its implications on measles control programme.

Raja, D (2009) Molecular characterization of indigenous measles virus clades in Tamilnadu, identification of transmission pathways and its implications on measles control programme. Doctoral thesis, King Institute of Preventive Medicine, Chennai.

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Abstract

Measles is an acute, highly contagious, respiratory viral infection caused by measles virus that belongs to Morbilli genus of the family Paramyxoviridae. Measles is uniquely a human disease, although primates can contract it. However, neither primates nor any other animal reservoir has been identified as capable of maintaining the disease or permitting its spread or reintroduction into human population. Measles is an airborne virus spread by direct contact with droplet from respiratory secretions of infected persons. Patients with measles are most infectious during the late prodromal phase of the illness, when cough and coryza are at their peak. However, the disease is probably contagious from several days before until several days after the onset of rash. In Tamil Nadu state, though high level of immunization coverage is being maintained for the past several years, suspected measles outbreaks are reported from almost all the districts. However laboratory confirmation was very limited. Before this study was planned, only few studies are reported on laboratory confirmation of suspected measles outbreaks and evaluation of immune response against measles containing vaccine. But, these studies were based on hospital settings and/or limited to confined area mainly from one city in North Arcot district of Tamilnadu state.130,303 Therefore, the true prevalence of the measles in the state of Tamil Nadu is not known. Most importantly, no reports are available on circulating genotypes of measles virus. This study was undertaken to investigate and confirm reported outbreaks of suspected measles, establish evidence of circulating measles virus genotypes, and assess the impact of introduction of second dose of measles vaccine in a selected population. The study was conducted during 2002 – 2007 at the Department of virology, King Institute of Preventive Medicine, Chennai, India. In the present study (2002 – 2007), 153 suspected measles outbreaks reported from 28 districts were investigated. No outbreak was reported from 2 districts (Nagapattinam and Theni). It is observed from the study that for confirmation of measles and rubella by serology timing of sample collection is critical. In the present study, the blood samples were collected between 0 and 41 days after the onset of rash. Approximately 80% of those samples collected within 3 days after the onset of rash were positive. A higher percentage of positivity 86.5% was observed from the samples that were collected between 4 and 10 days after the onset of rash and it decreased to 73.3% if collected between 21 – 41 days. The difference was statistically significant (χ2 – 17.086; P= 0.009). The same was observed for Rubella confirmation: 26% (14 out of 52) of samples were positive if collected during 4 to 10 days after the rash onset. Only 15% of the samples were positive if collected between 21 – 34 days after the rash onset. The difference was not significant (χ2 – 7.470; P= .280). Virus was isolated from 49 specimens representing 29 outbreaks. Though virus isolation was not useful for case confirmation, this is useful for molecular epidemiological studies. In Tamil Nadu, measles outbreaks were reported from almost all the districts of the state, despite the maintenance of high level immunization coverage in the last decade.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: Indigenous measles virus clades; transmission pathways; measles control programme
Subjects: MEDICAL > Community Medicine
Depositing User: Devi S
Date Deposited: 20 Jun 2017 09:59
Last Modified: 21 Jun 2017 06:14
URI: http://repository-tnmgrmu.ac.in/id/eprint/134

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