Nigerian Journal of Paediatrics 2011;38(4):170 - 174
Bugaje MA
Yusuf H
Seroprevalence of Varicella Zoster Virus
Abdulkadir I
Infection among Primary school Children
Ahmed AA
In Northern Nigeria
Received:8th September 2011
Abstract Background:
immunoglobulin G (IgG) using the
Accepted: 13th October 2011
Zoster infection occurs exclusively
Automation ELISA IgG Kit
in man and commonly affects
manufactured by Automation INC.
Bugaje MA ( )
children with predilection for
U S A .
D a t a
o b t a i n e d
w e r e
Abdulkadir I
school age children. Following
summarized using percentages and
Department of Peadiatrics
infection the course of the disease
frequency tables. Results were
Ahmadu Bello University
in immunocompetent children is
analyzed using Epi- info version
Teaching Hospital Zaria
often mild and self limited but in
Kaduna State, Nigeria
older age groups infection may be
Results: Three hundred and fifty
severe with poor outcomes ranging
three pupils were recruited for the
Yusuf H, Ahmed AA
from complicating bacterial
study. The overall prevalence rate
Department of Biotechnology
morbidities to death. In Kaduna
for VZV infection was 66.3% with
Federal University of Technology
State, Northern Nigeria the
the value in males being 68.5% and
Yola, Nigeria
seroprevalence of Varicella - zoster
in females 63.9%. The prevalence of
virus (VZV) infection is unknown .
VZV infection increased with age in
The current cross - sectional study
both sexes. A high percentage of
was conducted to assess the
children (60%) were seropositive at
seroprevalence of VZV infection
4-6 years.
among nursery and primary school
Conclusion: The study shows a
pupils in Kaduna State.
66.3% prevalence of VZV infection
Nursery and primary
among children in Kaduna State.
school pupils between the ages 4
and 15 years were randomly
necessitates further studies to
selected from the three geopolitical
establish the burden of the problem
z o n e s
o f
K a d u n a
S t a t e .
in Nigeria and rationalize the
Demographic data on each subject
institution of preventive measures
were obtained by administration of
against the infection, particularly
a questionnaire and blood samples
were collected for serum analysis
of Varicella - zoster virus
populations, primary infection tends to occur at a
younger age. Varicella zoster infection generally
Varicella otherwise referred to as chickenpox is
follows a benign course particularly in children with a
caused by the DNA virus Varicella zoster virus and
normally functioning immune system but can
belongs to the Herpesviridae family. This virus is
sometimes be accompanied with complications
exclusively found in man.
1, 2
Infection is highly
ranging from pneumonia to other more serious ones
contagious with a clinical attack rate of 65% to 85%
like varicella encephalitis, hepatitis purpura
fulminans to cerebella ataxia. Rarely it may mimic
following exposure and it usually spreads from an
acute abdomen. In the immunocompromised child
infected individual to a susceptible host via droplet
infection and or contact.
1 - 3
Children are most
such as the child with HIV infection, malignancy and
susceptible to infection. In non vaccinated
those on immunosuppressive therapy, varicella
infection may be severe and fatal. Children who have
Informed written and verbal consent was obtained
leukaemia have a 30% rate of disseminated varicella,
from parents/guardians of all subjects.
with a 7% mortality rate.
The Center for Disease
Control estimates that 60 to 100 individuals die
A total of 353 pupils were selected by multistage
annually from complications of varicella. Following
random sampling. One LGA was selected from each
resolution of varicella infection, Varicella - zoster
of the three geopolitical zones. The three LGAs
virus becomes latent in the peripheral ganglia and
randomly selected were Makarfi (north), Kagarko
persists throughout life and may be reactivated later.
(south) and Igabi (central) with each having 10, 11 and
Vaccination is about 80-85% effective in prevention
11 districts respectively. Using
a sample frame of
of all varicella disease and more than 95% effective in
public primary schools in the three selected LGAs, 32
prevention of severe disease. All over the world,
primary schools were randomly selected. One
because majority of cases of varicella are self limiting
primary school was selected from each of the district
and uncomplicated, there tends to be a dearth of
areas constituting the three selected LGAs. The study
information on the epidemiology of Varicella. In a
subjects were then randomly selected across classes
seroepidemiology survey of 160 children in Brazil, a
from primary 1
6 from the sampled schools. An
prevalence of 58.1% was documented several other
average of 11 subjects was selected per school,
researchers have documented varying prevalence
making a total of 91, 110 and 152 subjects in Makarfi,
rates from various part of the world.
8- 16
Kagarko and Igabi respectively. Only subjects whose
parents or guardians consented to the study were
With the current HIV pandemic world over and the
absence of routine varicella virus vaccine in Nigeria,
varicella virus infection may pose a threat to children
Questionnaires were administered to all subjects to
particularly the immunocompromised with a risk of
document their demographic data which include age
developing more severe disease, complications and
and sex of subjects, vaccinations received and history
mortality. There is therefore the need to study the
of recent contact with a case of chickenpox. Venous
epidemiology of the disease. This study was thus
blood sample was then collected from each subject,
designed to look at the prevalence of VZV infection in
centrifuged for two minutes and the separated sera
was stored at -20 C until tested for IgG. The analysis
primary school children in Kaduna State Northern
for VZV IgG antibodies was conducted using a
commercialized IgG enzyme-linked immunosorbent
assay (ELISA) kit manufactured by Diagnostic
Automation INC USA which uses cell- culture-
derived VZV antigens for the detection of anti -VZV
Materials and Methods
IgG antibodies in the serum. The serum assay was
conducted according to the manufacturer's instruction
The study was conducted in Kaduna State from
in the department of microbiology, Ahmadu Bello
January 1 to September 30 2008. Kaduna State is
University Zaria. Data were analyzed using EPI-info
located at the centre of northern Nigeria. It has a
version 3.0. Chi-square test was performed to
political significance as the former administrative
analyzed association between qualitative variables,
headquarters of the north during the colonial era. The
and statistical significance was established at p- value
State shares boundaries with Niger State to the west,
of < 0.05.
Zamfara, Katsina and Kano States to the north,
Bauchi and Plateau States to the east and Federal
Capital Territory Abuja and Nasarawa State to the
south. It occupies approximately 48,473.2 square
kilometers and has 23 local government areas
(LGAs). It is divided into three geopolitical zones
A total of 353 pupils were studied. I84 were males
namely north, central and south zones, with each
while the remaining 169 were females with a M: F
having eight, seven and eight local government areas
ratio of 1.1: 1. Of the 353 pupils studied, 234 were
respectively. The State has a total of 1510 primary
found to be seropositive for VZV IgG antibody,
giving an overall seroprevalence of 66.3%.
Corresponding figures for males and females were
Prevalence of Varicella Zoster Virus was studied
126 (68.4%) and 108 (63.9%) respectively. There
was therefore no significant gender predilection (x
among primary school children between the ages of 4
15 years in Kaduna state. Ethical clearance was
= 0.48, p>0.05).
obtained from the State Ministry of Education, the
Zonal Inspectorate Division of each local government
area and the school management of selected schools.
Table 1 shows the seroprevalence of VZV according
to age group in male subjects. The seroprevalence
was highest in the oldest age-group (13 to 15 years)
The study found a prevalence of 66.3% for varicella
having increased progressively from 60% among
zoster infection among primary school children in
the youngest children aged four to six years. A
Kaduna State. To the best of our knowledge there has
similar trend was observed among female subjects
not been any previous study investigating the
with the highest seropositivity rate among the 13 to
prevalence of VZV infection among children in this
15 year old age group. Comparing the percentage
locality and thus, it is difficult to compare our study to
seropositivity between the age groups the youngest
any other local finding. This dearth of local data could
and the oldest showed significant variability. Chi-
be attributed to the general perception that varicella
square = 9.02, p= 0.000 in boys while in girls X =
zoster virus infection particularly in children is benign
7.43, p= 0.000. (Tables 1 and 2 respectively)
and self limiting without serious outcomes or fatality.
Our finding however shows a high prevalence and is
Table 1: Distribution of VZV IgG by Age among
comparable to findings from other international
studies. Semenovitch and Lupi in Brazil found a
Primary School Boys in Kaduna State, Nigeria.
No of
prevalence of 58.1% among a population of 160
children in the State of Rio de Janeiro.
Our finding was however much lower than those of
Perez-Farinos et al in Madrid, Spain and Heininger
39.0 – 78.0
et al
4 – 6
in Switzerland where they documented
prevalence of 90.2% and 96.5% respectively. The
7 - 9
47.3 – 87.0
difference in study design could have accounted for
this observed difference in prevalence. While in both
our study and that of Semenovitch and Lupi in Brazil
10 -
47.5 – 88.4
the population was limited to children 15 years and
below, the study by Perez-Farinos et al included both
adults and children with age range two to 40 years.
13 –
50.2 – 92.5
This difference in age range of study subjects may
have accounted for the high prevalence they
documented. Heininger et al
studied only
adolescents aged 13 to 15 years, the age established by
*χ = 9.02, p = 0.000 (Chi-square analysis showed
various studies to be the peak age for VZV infection
association between age and % VZV IgG antibody
could explain the high variability. Also routine
vaccination against VZV infection in developed
countries may account for the apparent high
Table 2: Distribution of VZV IgG by Age among
prevalence rate observed compared to our study.
Primary School Girls in Kaduna State, Nigeria.
An earlier study from Western Nigeria in the 80s
No of
documented a low prevalence rate of 30% among 188
blood samples. Comparison with that study however
has to be done with caution as the age range in the
earlier study was not specified.
4 – 6
26.5 – 48.4
7 - 9
40.5 – 76.2
The age group specific prevalence from our study
showed that seroprevalence of VZV infection rose
10 - 12
47.0 – 84.3
with age among the study population steadily. This is
in consonance with findings from other studies. In
Turkey Savas et al in their study of 885 children
13 –
48.6 – 88.0
found that seropositivity rate for VZV infection
among children 0 15 years rose with increasing age.
Semenovitch and Lupi also documented a similar
finding. The age group 13 to 15 years had the highest
*χ = 7.43, p= 0.000 (Chi-square analysis showed
prevalence in our study which is similar with findings
association between age and % VZV IgG antibody
from other studies.
7, 12-14
The high infection rate in older
children could be due to increased VZV transmission
as the child gets older, as a result of increased
exposure. Also emergence of new VZV strains,
spreading among susceptible individuals has been
attributed to difference in geographical conditions
advocated by Lee.
between temperate and tropical countries.
The finding of similar prevalence rate of VZV IgG
The study has shown that VZV infection is prevalent
among the sexes in the present study is not surprising,
among children in Kaduna State. There is a need to
as other available reports have consistently found
carry out more extensive studies involving other parts
similar prevalence rates. This indicates that both sexes
of the country to provide evidence based arguments to
have equal risk of infection. Other Studies have
substantiate the need for support and provision of
shown variable results of prevalence rate of varicella
preventive measures in the form of vaccination to
zoster virus infection among males and female
children, particularly those at risk of developing
7, 11, 12
The variations observed were higher
severe infection, complications and increased risk of
prevalence in males in some studies, while others
found higher prevalence in females.
7, 11, 12
Our study found 60% of children under the age of six
years to be seropositive. This finding suggests that
children in the north are exposed to infection in early
life similar to the findings in most temperate
2, 8, 17
The present observation contrasts with
We wish to thank Professor HAAikhionbare for going
previous reports of high seropositivity in later life in
through the script and Professor S Olonitola for his
tropical countries. These differences have been
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