Molecular Epidemiology Of Rotaviruses Astroviruses And Adenoviruses Associated With Gastroenteritis In Children In Northwestern Nigeria

ABSTRACTRotaviruses are associated with ~ 610,000 deaths worldwide and with 33,000 deaths inNigeria in children < 5 years of age annually. A study of the epidemiology of rotavirus,astrovirus and adenovirus infection in children 0-5 years old with gastroenteritis wastherefore undertaken in Northwestern Nigeria where there is little or no information. Atotal of 1063 (869 diarrhoeic and 194 non-diarrhoeic) stool specimens were collectedfrom children attending clinics in Kaduna, Kebbi, Sokoto and Zamfara States from July2002 to July 2004. Viral antigens were detected by enzyme immunoassay (EIA) and thedifferent patterns of rotavirus genomic RNA by polyacrylamide gel electrophoresis.Rotavirus VP7 (G) and VP4 (P) genotyping was carried out by reverse transcriptionpolymerasechain reaction (RT-PCR). Rotavirus group A antigen was detected in 18%of the diarrhoeic and in 7% of the non-diarrhoeic specimens. Rotavirus infectionoccurred throughout the study period with slightly higher peaks in the dry season.Children < 2 years old were more vulnerable to rotavirus infection (p < 0.01). Therewere statistically significant associations between vomiting (p<0.01), feeding regimen(p<0.05) and rotavirus infection. There were, however, no statistically significantassociations between sex of the child, type of stool, a child’s socio-economic status andparents’ level of education, type of drinking water and rotavirus infection.Sixteen electrophoretic patterns were detected with the ‘long’ predominating (78%).Three strains exhibited the unusual combination of a VP6 Subgroup I specificity with a‘long’ electropherotype. VP6 subgroup I + II strain predominated (36%) in this study.Only 54 (32%) of the 170 rotavirus strains could be assigned a single sero- andgenotype. Of these, the predominant strain was G1 P[8] (46.3%). Six (3%) other strainscould be assigned a single G or P type. Of the remaining 110 rotavirus strains, 47 (28%)could not be typed and 63 (37%) were mixed infections consisting of 37 different straincombinations. The most prevalent mixed combination was G1G8 P[6] (15.9%).Genotypes G9 and G4 occurred only as mixed infections. The most prevalent VP4genotype was P[6]. Genotypes P[10] and P[14], detected for the first time in Nigeria asmixed infections, were found in 8.8% and 2.4% of cases respectively.ixA further 282 specimens were randomly selected from the 1063 stool specimens andscreened for astroviruses and adenoviruses using EIA kits. Astroviruses andadenoviruses were detected in 19% and 22.3% of the specimens respectively. Furtheranalysis of the adenovirus EIA positive specimen detected Ad40/41 in 8% of thespecimens. Astrovirus infection was more frequent among children 0-24 months oldwhile adenovirus infection predominated in children 25-36 months old.The present study indicates that the diversity of strains in Nigeria is much greater thanwas previously recognized. The detection of novel unusual VP4 genotypes (P[10] andP[14]) and the presence of unusual genotypes and mixed infections in this studyunderscores the need for a surveillance system for the detection of new rotavirus strainsin Nigeria and in Northwestern region in particular. There is a further need to designprimers specifically for the rotaviruses in Nigeria.xTABLE OF CONTENTSPageTitle page iDeclaration iiCertification iiiDedication ivAcknowledgement vAbstract viiiTable of Contents xList of Tables xvList of Figures xixList of appendices xxiCHAPTER ONE1.0 INTRODUCTION 11.1 Background Information 11.2 Rotavirus: A Leading Agent of Infantile Diarrhoea

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