Prevention of rotavirus diarrhoea in Gambian children

Hanlon, Philip William (1987) Prevention of rotavirus diarrhoea in Gambian children. MD thesis, University of Glasgow.

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Between June 1984 and June 1986 a variety of studies on rotavirus diarrhoea and its prevention were conducted in Bakau, a peri-urban Gambian community. This thesis reports the results of these studies and places them in the context of current knowledge concerning the epidemiology and immunology of rotavirus infection. Short, well-demarcated epidemics of rotavirus diarrhoea were observed in this study during two consecutive cool dry seasons in The Gambia. This very clear seasonal pattern has now been documented for four consecutive years. During the 1985/86 epidemic transmission was intense with an attack rate for infants of 36%. It was estimated that asymptomatic virus shedding in stools was two thirds as common as symptomatic infection. Rotavirus diarrhoea was more severe than diarrhoea due to all other causes and clinical rotavirus infection was associated with weight loss in the post-infection period. Non-epidemic periods were characterised by very occasional mild cases and asymptomatic virus shedding in neonates. There was a change in R.N.A. electropherotypes from a predominantly long pattern in 1983/84 and 1984/85 to short patterns in 1985/86. A case-control study was conducted on 92 cases and 92 age and vaccine status matched controls to determine social and environmental risk factors for rotavirus infection. No risk factors were found but there was an association between rotavirus cases and the presence of a dog in the child's compound. A randomised, double blind, placebo controlled trial of the bovine rotavirus vaccine KIT 4237 was undertaken in young Gambian children. Three doses of rotavirus vaccine were administered, commencing at the age of ten weeks, concurrently with oral or killed poliomyelitis vaccine. Prevaccination rotavirus neutralising antibody levels were high. 84/185 infants (45%) showed an increase in neutralising antibody titre after receiving rotavirus vaccination, compared with 20/91 (22%) of unvaccinated infants. During 14 months of observation, clinical rotavirus infection was detected in 24/78 (31%) children in the rotavirus/oral polio group, in 34/83 (41%) children in the placebo/oral polio group, and in 23/92 (25%) children in the rotavirus/killed polio group, giving an overall vaccine efficacy of 33% (95% C.I. 4% to 53%). KIT 4237 did not reduce the severity of clinical infections. No effect from the concurrent administration of oral polio vaccine on the immune response to rotavirus vaccine was observed. Lower type 1 and type 3 polio antibody levels were found in children who received oral polio and rotavirus vaccines than those who received oral polio vaccine and placebo but differences between the two groups were not statistically significant. A number of possible explanations for the poor efficacy of KIT 4237 are considered. High maternal antibody levels to rotavirus at the time of vaccination may have reduced the immune response to vaccination. Another possibility is that Gambian breast milk contains anti-rotavirus antibody or nonantibody factors which inhibited the vaccine response. In addition, naturally circulating enteroviruses may have interfered with the immune response to the rotavirus vaccine. In anticipation of the development of a successful rotavirus vaccine, factors leading to poor vaccination compliance were investigated. The vaccination status of 251 children aged 12 - 18 months living in Bakau was determined from their health cards. Two subgroups were identified: children who were fully vaccinated, and those who had received less than half their vaccinations. The social and environmental circumstances of these children were investigated. In the poorly vaccinated group both parents were less well educated and there was a trend towards poorer literacy. Mothers of poorly vaccinated children had a poorer knowledge of the diseases their children should be vaccinated against and had a more superstitious view of disease causation. Those children who showed poor compliance came from larger families. Mothers of well vaccinated children were more inclined to bring them for non-curative services. The implications of the above findings for further research into rotavirus and diarrhoeal disease in general are also considered.

Item Type: Thesis (MD)
Qualification Level: Doctoral
Keywords: Medicine, Epidemiology, Public health
Date of Award: 1987
Depositing User: Enlighten Team
Unique ID: glathesis:1987-76700
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Nov 2019 13:52
Last Modified: 19 Nov 2019 13:52

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