Nigerian Journal of
Paediatrics 2011;38(4):170 - 174
ORIGINAL
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:
Varicella
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
3.0.
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
Methods:
Nursery and
primary
among children in
Kaduna State.
school pupils between
the ages 4
This
high
prevalence
rate
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
immunocompromised
young
were collected for
serum analysis
children.
of Varicella - zoster
virus
Introduction
populations, primary
infection tends to occur at a
younger age. Varicella
zoster infection generally
4
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
4
following exposure and
it usually spreads from an
acute abdomen. In the
immunocompromised child
5
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
171
infection may be severe
and fatal. Children who have
4
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.
4
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
3
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,
6
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
7
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
included.
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
0
primary school children
in Kaduna State Northern
Nigeria.
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
st
th
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
Results
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,
schools.
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
2
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.
172
Table 1 shows the
seroprevalence of VZV according
Discussion
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 =
2
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
7
Primary School Boys in
Kaduna State, Nigeria.
Age
Number
No of
Prevalence
95%
prevalence of 58.1%
among a population of 160
group
of
positive
%*
confidence
children in the State
of Rio de Janeiro.
in
samples
samples
interval
(years)
Our finding was however
much lower than those of
Perez-Farinos et al in
Madrid, Spain and Heininger
10
20
12
60.0
39.0 – 78.0
et al
11
4 – 6
in
Switzerland where they documented
prevalence of 90.2% and
96.5% respectively. The
7 - 9
46
31
67.4
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
7
10 -
59
41
69.5
47.5 – 88.4
the population was
limited to children 15 years and
12
below, the study by
Perez-Farinos et al included both
10
adults and children
with age range two to 40 years.
13 –
59
42
71.2
50.2 – 92.5
This difference in age
range of study subjects may
15
have accounted for the
high prevalence they
documented. Heininger
et al
11
studied only
Total
184
126
68.5
adolescents aged 13 to
15 years, the age established by
*χ
= 9.02, p = 0.000 (Chi-square analysis showed
2
various studies to be
the peak age for VZV infection
association between age
and % VZV IgG antibody
could explain the high
variability. Also routine
seroprevalence)
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
16
Age
Number
No of
Prevalence
95%
group
of
positive
%*
confidence
documented a low
prevalence rate of 30% among 188
in
samples
samples
interval
blood samples.
Comparison with that study however
(years)
has to be done with
caution as the age range in the
earlier study was not
specified.
16
4 – 6
17
7
41.2
26.5 – 48.4
7 - 9
39
24
61.5
40.5 – 76.2
The age group specific
prevalence from our study
showed that
seroprevalence of VZV infection rose
10 - 12
55
37
67.3
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
12
13 –
58
40
69.0
48.6 – 88.0
15
found that
seropositivity rate for VZV infection
Total
169
108
63.9
among children 0 15
years rose with increasing age.
Semenovitch and Lupi
also documented a similar
7
finding. The age group
13 to 15 years had the highest
*χ
= 7.43, p= 0.000 (Chi-square analysis showed
2
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
seroprevalence)
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,
13
173
spreading among
susceptible individuals has been
attributed to
difference in geographical conditions
advocated by
Lee.
13
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
subjects.
7, 11, 12
The variations observed
were higher
severe infection,
complications and increased risk of
prevalence in males in
some studies, while others
mortality.
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
Acknowledgement
life similar to the
findings in most temperate
countries.
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
17
support.
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