First nationwide survey of the health of schoolchildren in Chad

First nationwide survey of the health of schoolchildren in Chad

Michael Beasley1, Simon Brooker1, Montanan Ndinaromtan2, Ester M. Madjiouroum2, Marie Baboguel3,

Elie Djenguinabe4 and Don A. P. Bundy5

1 Department of Infectious Disease Epidemiology, Imperial College School of Medicine, London, UK2 Hopital General de Reference, N’Djamena, Chad3 School Health Commission, Ministere de la Sante, N’Djamena, Chad4 School Health Commission, Ministere de l’Education, N’Djamena, Chad5 International School Health Initiative, Human Development Division, The World Bank, Washington DC, USA

Summary Survey data are presented from a nationwide survey of the health of schoolchildren in Chad. The

country was stratified into distinct ecological zones based on satellite sensor environmental data.

Twenty schools were visited and 1024 children aged between 6 and 15 years were included in the

study. The overall prevalence of stunting, underweight, anaemia and goitre was 18.7, 16.5, 25.1 and

23.3%, respectively. Schistosoma haematobium, Schistosoma mansoni and hookworm were the only

helminth species found with prevalences of 13.2, 1 and 32.7%, respectively. A greater proportion of

boys were stunted, underweight, anaemic and infected with S. haematobium and hookworm than

girls. Older children were more stunted, underweight and infected with S. haematobium and

hookworm than younger children, but less anaemic. The prevalence of infection showed marked

geographical heterogeneity, with hookworm prevalence being highest in the Sudanian and tropical

zone, and S. haematobium being most prevalent in the Sahelian zone and the Logone and Chari basins

in the west of the country. These data show that there is a high prevalence of helminth infection in

Chad, but that treatment for S. haematobium and hookworm should be targeted to different

geographical areas.

keywords hookworm, schistosomiasis, anaemia, goitre, stunting, underweight, schoolchildren, Chad

correspondence Simon Brooker, Department of Infectious Disease Epidemiology, Imperial College

School of Medicine, Norfolk Place, London W2 1PG, UK. E-mail: [email protected]

Introduction

As part of its recent education reform, the Government of

Chad has identified health and nutrition as major con-

straints on the quality of school learning and educational

achievement of children. Before health services can be

planned efficiently, data are required concerning the

prevalence and distribution of infection and malnutrition

in the country. Previous studies of these problems among

schoolchildren in Chad have for the most part been rare,

limited and extremely dated (Buck et al. 1970; Gigase et al.

1988; Massenet et al. 1995), with the recent exception of a

national survey of iodine deficiency (Wyss et al. 1996). For

this reason, it was deemed necessary to conduct the first

nationwide survey of the nutritional status and parasitic

infections of Chad’s schoolchildren. The present paper

reports the results of this survey.

Materials and methods

Sample design and study population

A nationwide survey was undertaken in Chad in November

2000. The country was divided into separate ecological

zones based on the mean annual summaries (1982–2000

inclusive) of multitemporal remotely sensed (RS) data from

the Advanced Very High Resolution Radiometer (AVHRR)

(see Brooker et al. 2002a for details) (Figure 1). Overlay-

ing this map with available data on population density

(Deichmann 1996) helped guide the sample protocol,

focusing on the populous south-west of the country. In this

area, there are three ecological zones (Sahelian, Sudanian

and Tropical) and an urban zone (the capital, N’Djamena).

Internal travel is extremely difficult in many areas of

Chad and finance and availability of staff for the survey

Tropical Medicine and International Health

volume 7 no 7 pp 625–630 july 2002

ª 2002 Blackwell Science Ltd 625

were limited. These factors constrained the sample to a

total of 20 schools all situated not more than 30 km from

the country’s main roads. The number of schools sampled

in each zone was then proportional to the national

population in each zone. For example, 10% of Chad’s

population lives in the Tropical zone, consequently two

schools were sampled here.

In each sampled school, a target of 25 boys and 25 girls

in Class 3 (9–10 year olds) were randomly selected. If there

were insufficient pupils in Class 3 additional pupils were

sampled from Classes 4–7. Many of the schools visited

were small, and this, compounded by low female enrol-

ment, meant that in many schools all girls were selected to

achieve the target sample size, and in some cases fewer

than 25 girls were present, and therefore examined.

Participation was voluntary and was approved by the

school committee and parents.

Investigations

The height and weight of each child was measured to the

nearest 0.1 cm and 0.1 kg, respectively, using a stadiom-

eter (‘Leicester’ Model, Child Growth Foundation, UK)

and electronic scales (Soehnle, CMS Weighing Equipment,

UK). Z-scores of height-for-age, weight-for-age and

weight-for-height were calculated using NCHS reference

values using Anthro software (CDC, Altanta, GA, USA).

Children with a Z-score of height-for-age, weight-for-age

or weight-for-height of £ 2 SD below the NCHS median

were defined as stunted, underweight or wasted, respect-

ively. Finger prick blood was used to estimate the haemo-

globin concentration using a portable photometer

(Hemocue Ltd, Sheffield, UK). Anaemia was defined as a

haemoglobin concentration < 110 g/l. Children underwent

a brief standardized clinical examination to assess presence

and size of goitre, which was graded: grade 0, no goitre;

grade 1, not visible but palpable; grade 2, thyroid visible.

No grade 2 was seen during the survey and therefore all

goitre is taken as not visible but palpable.

A faecal sample was collected from each child and

examined using the Kato–Katz method and the concen-

tration of helminth eggs was expressed as eggs per gram of

faeces (epg). Ten millilitres of a urine specimen collected

from each child was collected and filtered through a

13-mm diameter polycarbonate membrane with a 12-lm

pore size (Millipore Ltd, UK). The presence of Schistosoma

haematobium eggs was noted and the concentration

expressed as eggs/10 ml urine. Individual children found

infected with schistosomiasis were given a 40-mg/kg dose

of praziquantel and those infected with geohelminth

species were given 400 mg albendazole.

Data analysis

The aims of this study were to first describe the prevalence

and distribution of helminth infection and undernutrition

(a) (b)

Figure 1 (a) Ecological zones in Chad based on RS-derived variables; and (b) the population density of chad. Data source: Deichmann (1996).

Tropical Medicine and International Health volume 7 no 7 pp 625–630 july 2002

M. Beasley et al. Health of schoolchildren in Chad

626 ª 2002 Blackwell Science Ltd

in Chad, and secondly to examine the variations within

individuals. The relationship between undernutrition and

infection with age group and sex was assessed using logistic

regression. Models were constructed which controlled for

either age group or sex. Differences in means were

compared using either a Student’s t-test and Mann–

Whitney U-test. Analysis was undertaken using Stata

(version 6, College Station, TX, USA).

Results

Table 1 summarizes the prevalence of undernutrition and

micronutrient deficiency by ecological zone. Stunting, a

measure of chronic or long-term malnutrition was similar

throughout the Sahelian, Sudanian and Tropical zones

(approximately 20%) and was lower in N’Djamena

(10.7%). The prevalence of anaemia varied from 12 to

35.3%, being highest in the Sahelian zone and lowest in

N’Djamena. Goitre rates ranged from 7 to 18% in

the South and N’Djamena to 33–45% in the Sahel and the

Logone and Chari basins in the West of the country.

Table 2 summarizes the prevalence and intensity of

infection in Chad by ecological zone. Schistosoma

haematobium, S. mansoni and hookworm were the only

helminth species found with prevalences of 13.2, 1 and

32.7%, respectively. Mean egg counts were light for both

S. haematobium and hookworm. Few children (7.1%)

were infected with both species. The prevalence of

S. haematobium and hookworm was found to vary

considerably between zones, with S. haematobium being

most prevalent in the Sahelian and Sudanian zones and

lowest in the south near the Central African Republic and

in N’Djamena. In the Sudanian zone, S. haematobium

infection was most common in the Logone and Chari

basins. By contrast, hookworm was most prevalent in the

south of the country, in the Sudanian and Tropical zones.

Nowhere in the country did Ascaris lumbricoides and

Trichuris trichiura occur at detectable levels.

Stratification by age revealed considerable differences in

the prevalence of infection and undernutrition: older

children were more stunted and underweight, had higher

rates of goitre and were more infected; whilst younger

children were more anaemic (Table 3). There were also

significant differences between the sexes, with significantly

more boys than girls infected with S. haematobium and

hookworm (Table 4); and boys were more heavily infected

than girls with S. haematobium (15.6 vs. 9.4 eggs/10 ml,

P < 0.05) and hookworm (208 vs. 132 eggs/gram,

P < 0.02). Boys were also more stunted, underweight and

anaemic, while girls had more goitre (Table 4).

Table 2 Prevalence of infection and mean egg counts of helminths by ecological zone in Chadian schoolchildren

Schistosoma haematobium Hookworm Both*

Ecological zone N Per cent infected Mean epg N Per cent infected Mean epg Per cent infected

N’Djamena 152 2.6 4.9 142 9.2 72 0.7Sahelian� 258 39.1 27.5 258 3.1 4 1.6Sudan 511 23.2 10.9 506 47.8 256 12.2Tropical 99 6.1 0.3 97 67.0 408 5.3

Total 1020 22.5 13.2 1003 32.7 180 7.1

* Nine hundred and ninety-four children provided both a stool and urine sample.�Not including N’Djamena.

Table 1 Prevalence of undernutrition and anaemia by ecological zone in Chadian schoolchildren

Ecologicalzone N

Per cent anaemia(Hb < 110 g/l) Mean Hb Per cent goitre

Per cent stunted(HAZ ± 2 SD)

Per cent underweight(WAZ ± 2 SD)

Per cent wasted(WHZ ± 2 SD)*

N’Djamena 151 12.0 121 11.8 10.7 18.0 7.1Sahelian� 258 35.3 114 44.6 20.2 28.7 10.4Sudan 514 23.4 118 17.0 19.9 10.5 0.5Tropical 101 26.7 117 17.8 20.8 13.9 0.0

Total 1024 25.1 117 23.3 18.7 16.5 4.6

* Sample size ¼ 392. Only calculated for below age 10 years for girls and 11.5 years for boys.�Not including N’Djamena.




Discussion

Good health and nutrition are essential prerequisites for an

effective education. Some health conditions of the greatest

importance for education can be dealt with most cost

effectively by schools themselves. The FRESH partnership

(Focusing Resources on Effective School Health) of the

World Health Organization, UNICEF, UNESCO and the

World Bank, has identified school health and nutrition

programmes as an essential component of efforts to achieve

equitable access to Education for All in low-income

countries.

Table 3 Mean anthropometric, haemoglobin and parasitological measurements and indices in children in Chad by age group, and thepercentage of children classified as stunted, underweight and anaemic

Mean (SD)

Ten years and below >10 years Significant difference (t-test)

Body mass index 15.1 16.1 <0.001Height-for-age z-score )0.65 )1.41 <0.001Weight-for-age z-score )0.96 )1.48 <0.001Haemoglobin (g/l)* 114.3 121.1 <0.001

(%) (%) Adjusted OR� (95% CI)

Stunted 11.1 26.6 2.88 (2.02–4.00)Underweight 10.1 23.2 2.61 (1.83–3.71)Body mass index < 15 50.1 26.1 0.35 (0.27–0.46)Anaemic (Hb < 110 g/l) 31.7 18.3 0.45 (0.34–0.61)Goitre 20.7 26.0 1.39 (1.03–1.85)Hookworm 27.5 38.1 1.58 (1.21–2.07)Schistosoma haematobium 18.5 26.6 1.50 (1.11–2.03)Schistosoma haematobium and hookworm 3.8 10.6 2.82 (1.63–4.87)

* Males as referent, controlling for age group.�6–10 years as referent, controlling for sex.

Table 4 Mean anthropometric, haemoglobin and parasitological measurements and indices in boys and girls in Chad, and the percentageof children classified as stunted, underweight and anaemic

Mean (SD)

Male Female Significance difference (t-test)

Body mass index 15.6 (1.5) 15.5 (1.7) 0.562Height-for-age z-score )1.15 (1.11) )0.84 (1.20) <0.001Weight-for-age z-score )1.31 (0.82) )1.08 (0.82) <0.001Weight-for-height z-score* )0.71 (0.77) )0.81 (0.78) 0.228Haemoglobin (g/l)� 116 (15) 120 (14) <0.001

(%) (%) Adjusted OR� (95% CI)

Stunted 20.8 15.4 2.84 (2.02–4.00)Underweight 19.0 12.6 2.61 (1.83–3.72)Wasted* 4.6 4.5 0.97 (0.34–2.79)Body mass index < 15 36.6 40.9 1.11 (0.85–1.44)Anaemic (Hb < 110 g/l) 29.0 18.9 0.52 (0.38–0.72)Goitre 21.3 26.4 0.26 (0.13–0.51)Hookworm 35.3 28.5 1.58 (1.21–2.08)Schistosoma haematobium 28.8 12.7 1.50 (1.11–2.03)Schistosoma haematobium and hookworm 10.0 2.6 2.82 (1.63–4.87)

* Only calculated for below age 10 years for girls and 11.5 years for boys.�Males as referent, controlling for age group.




Each school health programme must be tailored to its

specific national context. Before a programme can be

designed, a clear understanding is needed of the prevalence

and distribution of the problems to be addressed. But in

many low-income countries, studies of malnutrition and

infection of school-aged children are rare, limited in scope

or out of date. The data from the present study describe the

health status of schoolchildren in Chad, which were

collected according to ecological rather than geographical

areas, where the number of samples needed is much less

than required by traditional methods of surveying, and so

costs are reduced dramatically. In the absence of other data

from Chad, it is not possible to detect whether our

sampling protocol incurred any particular bias. It is

possible that patterns of transmission and malnutrition

may have differed in more remote areas of the country but

this is purely speculative. The survey was completed during

a 4-week period in November 2000 at an approximate cost

of US $34 000. This sum included purchase of necessary

equipment, transport costs and all consultant and staff

costs. It is not clear that, had more children been sampled,

unit costs would have been reduced.

The survey results show that the prevalence of undernu-

trition in Chad was comparable with other African countries

and while a cause for concern is marginally better than in

some (Stoltzfus et al. 1997a; PCD 1998; Lwambo et al.

2000). Anaemia was also less prevalent than in other African

countries (Stoltzfus et al. 1997b; Lwambo et al. 2000; PCD

2001). Intensity of helminth infection is believed to be a

major determinant of morbidity because of helminth infec-

tion, such as anaemia (Stephenson 1987; Stoltzfus et al.

1997b; Lwambo et al. 2000); thus, a possible explanation

for the relatively low prevalence of anaemia are the light

infections harboured by children in Chad.

An extensive survey of iodine deficiency in Chad was

conducted in 1993, reporting goitre prevalences of

60–70% across the country, with the exception of

N’Djamena where the prevalence was 25% (Wyss et al.

1996). Although our sample and that of the 1993 survey

differed (7–12 vs. 10–20 year olds; school based vs.

community based), the results do indicate that the

situation has marginally improved, but that more regional

variation now exists than formerly. While goitre rates

have fallen considerably in the South and N’Djamena

(7–18%), rates remain elevated in the Sahel (45%) and

also in the Logone and Chari basins (33%). The results

underline the need for continuing public health education

concerning the consumption of iodized salt. In 1993, few

households were found to use iodized salt – only 30% in

the Sudan zone, 27% in the Sahel and 50% in

N’Djamena. Consistent with previous studies (Wolde-

Gebriel et al. 1993; Wyss et al. 1996), our study showed

girls to have more goitre than boys, partly because of

increased iodine needs during puberty and gender-related

disparities in iodine supply.

In accordance with previous surveys (Buck et al. 1970),

no cases of infection with A. lumbricoides or T. trichiura

were found in Chad, presumably because of thermal

exclusion (see Brooker et al. 2001a, b). The extreme

temperatures experienced in Chad are unfavourable to the

ova of A. lumbricoides or T. trichiura, but they are not

detrimental to hookworm larvae in certain parts of the

country. Our results suggest that hookworm infection

occurs only in the south of Chad, with little or no infection

occurring in areas where mean land surface temperature

(LST) exceeds 48 �C (Brooker et al. 2001a). This distri-

bution pattern probably defines the upper thermal limit of

hookworm infection, which is apparently greater than the

37 �C for A. lumbricoides and T. trichiura. The high

prevalence of S. haematobium in the Sahelian zone is

corroborated by previous studies in Chad (Buck et al.

1970; Gigase et al. 1988; Massenet et al. 1995) showing

that areas of significant transmission are the Sahelian zone

and the Logone and Chari river basins.

The national survey aimed to understand the distribution

of undernutrition and infection within the country in order

to enable targeting of control programmes. The results of

the nutrition survey showed that children living in the

Sahelian zone were comparatively disadvantaged with

respect to protein energy malnutrition, anaemia and iodine

deficiency. Iodine deficiency was also a problem in the

Logone and Chari basins. School-based nutrition education

to combat protein energy malnutrition and iodine defici-

ency is needed in all areas of the country. Weekly school-

based iron supplementation should also be introduced

countrywide. Especially, priority should be given to the

promotion of all these interventions in the Sahelian zone.

According to WHO guidelines, all children living in the

Tropical and Sudanian zones should received mass treat-

ment with albendazole for hookworm infection. A pro-

gramme for schistosomiasis control, which would require

targeting schools by a questionnaire (Red Urine Study

Group 1995; PCD 1999) and a calculation to determine

the praziquantel dose based on the height of the child (Hall

et al. 1999) is required in the Sahelian zone and in the

Logone and Chari basins. Treatment is not required

elsewhere in the Sudanian zone or in the Tropical zone. In

Chad as a whole, a combined albendazole/praziquantel

treatment strategy is required only in the Logone and Chari

basins.

This survey provides comprehensive data on the preval-

ence and distribution of undernutrition and helminth

infections among schoolchildren across Chad. The results

suggest that efforts to provide nutritional interventions and




deworming to children may benefit children and improve

their learning in school.

Acknowledgements

The fieldwork was supported by the World Bank, the

Partnership for Child Development and the Wellcome

Trust. The survey was conducted at the request of the

School Health Commission of Chad, and forms part of the

preparation of the School Health Component of the Chad

Quality Education for All project, supported by the World

Bank. We thank Mourad Ezzine, Alan Dock, Lesley Drake,

Simon Hay, Kaidanoum Lea, Seung-hee Lee, N’Gooyo

Madeleine, Celia Maier, Jean-Pierre Moulia-Pelat, David J.

Rogers and William Wint for their support on various steps

of this work. S.B. is supported by a Wellcome Trust Prize

Fellowship (#062692).

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First nationwide survey of the health of schoolchildren in Chad