Patterns of diarrhoeal disease among under-five children in Plateau State, Nigeria, 2013–2017

Diarrhoea is the second commonest cause of childhood mortality among children under 5 years of age [1]. In developing countries, children under 3 years of age experience on average three episodes of diarrhoea every year. And each episode contributes to a significant nutritional deprivation which negatively affects child growth [2].

Diarrhoea disease is the leading cause of infant and child mortality in developing countries, and about 1.8 million children die per annum from this disease. These numbers of diarrhoeal deaths are still high despite a fall in childhood diarrhoeal disease from 4.6 million to 0.8 million over the last three decades [3‐5]. Young children are especially vulnerable to diarrhoeal disease, and most deaths related to diarrhoea took place in Africa and South Asia [6]. The World Health Organization (WHO) estimates that 525,000 under-five children die globally because of diarrhoeal diseases each year, with 1.7 billion cases of diarrhoeal disease diagnosed annually [1].

The mortality of diarrhoea remains high in Africa despite being easily treated with oral rehydration therapy [7]. According to WHO, in Southeast Asia and Africa, diarrhoea accounts for as much as 8.5 and 7.7% of all deaths respectively [8].There has been a decline in mortality rates from diarrhoea in the past three decades, however there is no improvement in sub-Saharan Africa and South Asia where 90% of diarrhoeal deaths occured [9].

In Africa, they estimated every child has five episodes of diarrhoea per year and that 800,000 children die each year from diarrhoea and dehydration. Diarrhoea is the second biggest killer of children in Nigeria, responsible for about 16% of child’s death every year. An estimated 151,700 children die in Nigeria every year from diarrhoea disease [8]. A high death rate because of diarrhoea can undermine the accomplishment of the Sustainable Development Goals (SDGs) in Plateau State and Nigeria if left unchecked.

To reduce diarrhoea mortality and morbidity, studies have helped inform intervention programs especially before the rainy season in regions with majority of cases [10, 11], allocation of limited resources and securing commodity supply chain to avoid stock outs [5], training and deployment of staff to remote and hard to reach communities [12].

In Nigeria, there is regional variation in the distribution of diarrhoea. A national study conducted in Nigeria showed a higher prevalence of the diarrhoeal disease among infants in the northern (37.7%) part of Nigeria of which Plateau State is located compared to the southern part (21.1%) [6]. The diarrhoea prevalence rate among under-five children in Nigeria is 10% [13]. There are a lot of vulnerable children at risk of death from diarrhoea in Nigeria [3]. The increasing disease burden and limited research in Plateau State suggests the need for our study in order to help inform health policies that will promote the control of diarrhoeal disease among under-fives.

Diarrhoea disease is associated with high under-five mortality rate (U5MR) in Nigeria, a country with U5MR of 128 per 1000 [13]. We conducted this study in Plateau State which is known to have high risk of diarrhoeal disease in Nigeria [13]. Studies have shown an association between poor housing, crowded conditions, low income and a higher rate of diarrhoea [14]. Others include poor storage of drinking water, use of unsafe water sources, improper disposal of children’s faeces and household garbage. Also implicated are poor hand hygiene practices among nursing mothers, partially breastfed children, bottle-feeding, malnutrition and immunodeficiency [14].

The aims of this study are to determine the; trend, case fatality rate, seasonal pattern and employ a time series model to predict expected cases of diarrhoeal disease among under-five children in Plateau State for 2018–2020. Time series forecasting is an important aspect of descriptive analysis and presentation of disease like diarrhoea, which is often neglected in Nigeria. This analytical approach is crucial because predicting diarrhoeal disease involves a time component because of the seasonal nature of the disease. The expected quarterly projection of children under the age of 5 years who will have diarrhoea in the study area in years ahead is necessary for monitoring and assessment of disease situation to inform policy. It will also enhance the level of preparedness towards plans to mitigate the spread of the disease.

The IDSR reported 60,932 cases of diarrhoea in Plateau State between 2013 and 2017 (Table 1). The age group of 12–59 months had the highest reported cases, 30,053 (49.3%). Age-specific case fatality rate was highest (0.53%) in children < 1 month and lowest (0.16%) in children 12–59 months (Table 2).

There is high positive variation in the third quarterly period during each year, except in 2016, when only a negative variation of − 256.67 reported cases of diarrhoea occurred (Table 3). Frequency distribution of observed and 3 months moving average of cases of diarrhoea in Plateau State across the year showed an upward trend with a trend line slope of 0.02162 (Fig. 1). The pattern of this variation follows the time series additive model.

The seasonal variation of diarrhoea by a quarter in Plateau State between 2013 and 2017 was de-seasonalised and thereafter adjusted to find out what the exact variation should be for the quarterly periods (January–March, April–June, July–September and October–December) of any year. The data show that higher seasonal variation for quarterly periods 1 (Q1 = 222.1319) and 3 (Q3 = 500.2431), than quarterly periods 2 (Q2 = -399.507) and 4 (Q4 = -322.868). Increase in trend line per quarter is (3760–2284)/ (18-1) = 86.82353 (Table 4)

In a three-year projection of cases of diarrhoea among under-fives in Plateau State, the first and third quarter predicts a rise in cases compared to the second and fourth quarters (Table 5). Available and projected data of diarrhoeal disease in Plateau State 2013–2020 shows an upward trend (Fig. 2).

The 3Qtr Moving average Trend (T_L) = Most recent trend less- opening trend illustrated in Table 3 is calculated thus:

Add up data from 2013 Q1, Q2, and Q3 and divide by 3. List the answer next to Q2. Repeat the process excluding 2013 Q1, now add Q2, Q3 and Q4 of 2013 divide by 3 and list answer next to Q3 2013. Repeat for all the Quarters till 2017 Q4. Note that there was no moving average for 2013 Q1 and 2017 Q4 due to insufficient data to calculate them.

This study found that diarrhoeal disease among under-five children occurs throughout the year. The most affected age group was 12–59 months. This contrast with an earlier work that reported the highest burden among the 0–11 months age group [10]. Findings from the Nigeria demographic and health survey (NDHS) show diarrhoea was most common among children age 12–23 months and least common among those aged 48–59 months [18]. Kenya Demographic and Health Survey (KDHS) shows that the prevalence of diarrhoea is highest in children aged between 6 and 11 months, followed closely by children between the ages of 12 and 23 months [19]. The higher rate in the older age group might be because of malnutrition, improper hygiene and inadequate care as compared with the younger age group who receive more care and attention by their mothers.

The highest annual cases of diarrhoea in this study was 24% in 2017, and the lowest was 13% in 2013. We may attribute the increasing trend of diarrhoea in this study to better capturing. NDHS national prevalence of diarrhoea among under-five was 10% while Plateau State was 5.6% [18]. Higher prevalence has been reported. Ucheh et al. reported an incidence of 51.8% [20], and Houatthongkham et al. (74.8% in children 0–24 months) [21].

The age-specific case fatality rate is highest in children < 1 month and lowest in the older age group 12–59 months. These findings are consistent with earlier studies in which mortality was highest in children below 1 year [22]. The high mortality in the younger age group in this study could be due to low immunity, poor caregiver hygiene practices and malnutrition. In Nigeria, only 17% of children under 6 months had exclusive breastfeeding [18]. Most infants are on complementary feeds and have lost maternal antibodies. They are active, crawl around, pick up and ingest contaminated objects. Malnutrition, open faecal disposal, poor hygiene, inadequate immunization coverage, lack of access to safe drinking water, insecurity and natural disasters are some predictors of mortality in children under 5 years of age.

This study depicted seasonal variation of diarrheal disease in this age group with most cases reported in the first and third quarters of the year having peaked in the dry and rainy seasons. This corroborates a study in Ghana that reported bimodal seasonality of diarrhoea. The second peak occurred between December and February before the rainy season (May to August) [10]. In a similar study in Bangladesh, the first peak occurs prior to the high rainfall period and the second peak occurs towards the end of the high rainfall [23]. Diarrhoea cases in China showed a bimodal distribution: diarrhoea in children less than 5 years was more likely to peak in fall-winter seasons, while diarrhoea in persons greater than 5 years peaked in summer [24]. Another study reported seasonal distribution of infectious diarrhoea in Shanghai with peaks in winter and summer.

Winter peaks were mainly caused by norovirus and rotavirus, while summer peaks were caused by bacterial infections [24]. Our study has the first peak between January to March prior to the rainy season and the second peak between July to September towards the end of the rainy season. The rainy season is usually characterised by heavy rainfall leading to flood, poor sanitation and contamination of water bodies from open or broken sewer. In Botswana, a study on climate change suggests that a drier, hotter climate might exhibit a positive influence on the dry seasonal diarrhoeal case incidence [4].

Based on our time series modelling, there was an increasing trend in the cases of diarrhoea among children under the age of 5 years during 2013–2017, and our projection showed that this trend will continue up until year 2020, all things being equal. Time-series data are useful for accurately monitoring of disease pattern over a period, and therefore, forecast trends. The assumption that the quality of current intervention to mitigate the disease would remain the same between 2018 and 2020 may not be true. This is because government and some international agencies put efforts in place to meet the goal of a reduction in the cases of diarrhoea in Nigeria. This increasing trend of diarrhoeal disease in Plateau State found in this study may be because of the likelihood that diarrhoea cases reporting mechanisms might just be getting better as clinics are improving and learning more about reporting strategies. The three-year projection of cases of diarrhoea among under-fives in Plateau State from 2018 to 2020 shows a rise in cases in an undulating pattern. The first and third quarter predict peaks in cases with a slight decline in the second and fourth quarters.

The most affected age group in this study are children 12–59 months and highest mortality in children < 1 month. Diarrhoea depicts bimodal seasonality with the highest peak in the rainy season. There is a need to implement prevention and control strategy at the State and improve data reporting. Additional studies at community level would be useful in reporting the number of episodes of diarrhoea and identify LGAs differences for intervention.