Journal of Tropical Pediatrics Advance Access published online on March 15, 2008
Journal of Tropical Pediatrics, doi:10.1093/tropej/fmn021
© The Author [2008]. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org
Epidemiology of Rotavirus Infection in North-western Nigeria
M. Aminua,
A. A. Ahmada,
J. U. Umohb,
J. Dewarc,
M. D. Esonac and
A. D. Steelec
aFaculty of Science, Department of Microbiology, Ahmadu Bello University, Zaria, Nigeria
bFaculty of Veterinary Medicine, Department of Public Health and Preventive Medicine, Ahmadu Bello University, Zaria, Nigeria
cMRC/MEDUNSA Diarhoeal Pathogens Research Unit, University of Limpopo, Medunsa Campus, Pretoria, South Africa
Correspondence: Dr M. Aminu, Department of Microbiology, Faculty of Science, Ahmadu Bello University, Zaria, Nigeria. E-mail < maryamaminu{at}yahoo.com>.
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Abstract
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Rotaviruses (RV) are associated with
33 000 deaths in children
<5 years of age annually in Nigeria. However, limited data
exit on RV infection in north-western Nigeria. During July 2002
to July 2004, 1063 (869 diarrhoeic and 194 control) stool samples
were collected from children
<5 years of age presenting with
diarrhoea in north-western Nigeria. The stools were analysed
for RV antigen and further characterized by antigenic and genomic
methods. RV was detected in 18% of children with diarrhoea and
7.2% of the age-matched case controls. The highest RV burden
was detected in children
<6-months-old. Long electropherotypes
and VP6 subgroup I
+ II specificity predominated.
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Introduction
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Recent estimates [
1] attribute 527 000 deaths in children <5
years to rotavirus (RV) annually. Improvements in sanitation
and the availability of clean water have not decreased the rate
of RV diarrhoea and the development and implementation of an
effective vaccine into the routine EPI schedule is considered
the first strategy of prevention [
2].
Epidemiological studies of RV infection reveal the greatest degree of diversity of RV strains in West Africa [3]. There is little or no information on RV-associated diseases in north-western Nigeria where there is the likelihood of strain diversity.
While the introduction of the two new currently available oral, live attenuated RV vaccines may only occur in 4–6 years in these African settings, data on the epidemiology of RVs will be required to preamble vaccine implementation.
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Materials and Methods
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Faecal samples were obtained from 869 children <5-years-old
who were presented or admitted at clinics or hospitals for diarrhoeal
illness in north-western Nigeria. In addition, 194 control (non-diarrhoeic)
samples were collected. Stool samples were stored frozen at
–20°C and transported to the MRC/MEDUNSA Diarhoeal
Pathogens Research Unit, University of Limpopo, Medunsa Campus,
Pretoria, South Africa for further analysis. Upon delivery,
a 10% faecal suspension was prepared using balanced salt solution
and the suspension stored at 4°C.
RV detection
RV antigens were detected utilizing a commercially available Rotavirus IDEIATM Kit (DakoCytomation, UK) according to the manufacturers’ instructions.
Polyacrylamide gel electrophoresis (PAGE)
All RV-positive specimens were analysed by PAGE as previously described [4]. Briefly, RNA was extracted utilizing phenol–chloroform deproteinization and ethanol precipitation, electrophorezed overnight and visualized by silver staining according to the method described by Herring et al. [5].
Subgroup specificity (VP6)
All RV-positive specimens were analysed utilizing an ‘in-house’ VP6 ELISA as described by Steele and Alexander [6]. Group-specific [7] and subgroup-specific monoclonal antibodies [8] were a kind donation from H. B. Greenberg, Stanford University, USA.
Statistical analysis
Analysis of RV infection in children according to age and sex was done using statistical programme for social sciences (SPSS) version 11.0. Differences with p-values >0.05 were considered not significant at 95% CI.
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Results
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RV antigen was detected in 18% (156/869) of the diarrhoeic samples
and in 7.2% (14/194) of the control samples. Infection occurred
throughout the study period with slightly higher peaks in the
drier months (
Fig. 1). Highest prevalence of RV infection was
in children <6-months-old (
p < 0.01) (
Fig. 2). Viral shedding
was slightly higher in males (16.4%: 100/608) than females (15.4%:
70/455) (
p > 0.05). Electropherotypes could be obtained from
54% (92/170) of specimens analysed. Long RNA migration patterns
predominated (80.4%: 74/92) and 10 distinct long (L) electropherotypes
were noted (
Fig. 3). In addition, six distinct short electropherotypes
(
n = 18) and a small proportion of mixed patterns (2.2%) were
detected. Subgroup specificity (SG) could be assigned to 146/170
specimens, with 22 specimens not reacting to any of the antibodies
used and a further two specimens having insufficient stool for
testing. Subgroup II specificity was found in 41/170 specimens,
SGI in 37/170 specimens and SGnon-I/non-II in 16/170 specimens.
Surprisingly, SGI+II specificity was detected in 52/170 specimens,
by far the predominant subgroup in specimens from north-western
Nigeria. Three strains exhibited the unusual combination of
VP6 SGI specificity with a long electropherotype.
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Discussion
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Nigeria has recently been ranked second among six countries
with the greatest number of RV disease-associated deaths per
year in children <5-years-old [
9]. The peak of RV infection
in children <6-months-old implies greatest burden in the
youngest and most vulnerable unlike developed countries where
infections are more common in children 9- to 15-months-old [
2].
Detection of RVs throughout the study period is not unexpected
and similar seasonality trends have previously been reported
in Africa [
10].
Extensive genomic diversity was observed in this study as indicated by the 16 RNA electrophoretypic variants identified. Mixed patterns noted for the first time in Nigeria may represent possible means of emergence of genetic re-assortant RV strains. These strains might have originated from animals; because the study area is predominantly inhabited by nomadic pastoral farmers who live in close association with their animals and share common sources of drinking water.
Interestingly, 31% of samples were of SGI+II specificity indicating the possibility of mixed infections. This has been previously reported in very low level [11]. The unusual combination of a VP6 SGI/long electropherotype noted have been previously described [6, 12] and may be a consequence of re-assortment process.
This study showed RVs to be important cause of diarrhoea in children 0–5 years in north-western Nigeria. Therefore, there is the need for additional studies in this region to provide data required to expedite the introduction of RV vaccines to Nigerian children, who would clearly benefit from these interventions.
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Acknowledgements
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This study was conducted, thanks to the grant from UNESCO-L'ORÉAL
Fellowship for Women in Life Sciences awarded to Dr M. Aminu
The World Health Organization and the Medical Research Council
of South Africa also supported the research.
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References
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- Herring AJ, Inglis NF, Ojeh CK, et al. Rapid diagnosis of rotavirus infection by direct detection of viral nucleic acid in silver-stained polyacrylamide gels. J Clin Microbiol (1982) 16:473–7.[Abstract/Free Full Text]
- Steele AD, Alexander JJ. The relative frequency of subgroup I and II rotaviruses in black infants in South Africa. J Med Virol (1988) 24:321–7.[Web of Science][Medline]
- Beards GM, Campbell AD, Cottrell R, et al. Enzyme-linked immunosorbent assay based on polyclonal and monoclonal antibodies for rotavirus detection. J Clin Microbiol (1984) 19:248–54.[Abstract/Free Full Text]
- Greenberg HB, McAuliffe V, Valdesuso J, et al. Serological analysis of the subgroup protein of rotavirus, using monoclonal antibodies. Infect Immun (1983) 39:91–9.[Abstract/Free Full Text]
- Burton T. Global Immunization News 25 May 2007. (15 November 2007, date last accessed). http://www.who.int/immunization_monitoring/burden/rotavirus_estimates/en/index.html.
- Cunliffe NA, Kilgore PE, Bresee JS, et al. Epidemiology of rotavirus diarrhoea in Africa: a review of studies to anticipate rotavirus immunization. Bull World Health Organ (1998) 76:525–37.[Web of Science][Medline]
- Steele AD, Nimzing L, Peenze I, et al. Circulation of the novel G9 and G9 rotavirus strains in Nigeria in 1998/1999. J Med Virol (2002) 67:608–12.[CrossRef][Web of Science][Medline]
- Kobayashi N, Lintag IC, Urasawa T, et al. Unusual human rotavirus strains having subgroup I specificity and ‘long’ RNA electrropherotype. Arch Virol (1989) 109:11–23.[CrossRef][Web of Science][Medline]
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Abstract
Introduction
