Introduction

Infections are the major cause of severe morbidity and mortality among children worldwide [₁]. Diarrhoeal illness stands, as an important cause of infectious morbidity in children, exceeded only by respiratory tract infections and mortality is currently associated with cases that evolve without proper feeding or rehydration care, invasive diarrhoeas with extraintestinal or systemic involvement, or persistent diarrhoeas that occur especially in infants from low-level socioeconomic groups, who suffer previous deficiencies and develop severe nutritional consequences of enteric infection [₂]. Diarrhoea defined as excessive and frequent evacuation of watery faeces, usually indicating gastrointestinal distress or disorder of 3-7 days duration, is a frequent illness in developing countries and contributes to the deaths of 4.6 million to 6 million children annually in Asia, Africa, and South America and it has been estimated that in the very poor countries of these regions each child suffers up to 15 to 19 episodes of diarrhoea per year [₂,₃].

Despite much progress in the understanding of pathogenesis and of management, diarrhoeal illness still remains one of the most important causes of global childhood mortality and morbidity largely because the aetiology and pathogenesis of persistent diarrhoea are usually multifactorial and sometimes can not be identified [₄]. Reports from different parts of the world have implicated various pathogens such as parasites, bacteria and viruses with outbreak of infant diarrhoea disease in children [₅,₆,₇,₈,₉,₁₀]. However in the developing countries including Nigeria, infantile diarrhoea disease is grossly under-reported and the incidence under-estimated, this is attributed to poverty and ignorance among affected group who usually constitute up to 80% of the population of the area [₁₁].

In Nigeria, available reports indicate that more than 315,000 deaths of preschool age children are recorded annually as a result of diarrhoea disease [₁₂,₁₃]. Nevertheless, despite the public health implications and enormous burden imposed on the primary health care delivery system by infantile diarrhoea illness in the country, there is still paucity of information on the epidemiology and aetiology of infantile diarrhoea in many regions including the South-eastern Nigeria. Since the pathogens responsible for diarrhoea infections employ ingenious mechanisms to establish disease, regional variation in the microbiological profile may exist even in the same country [₃,₁₁]. The persistent seasonal outbreak of diarrhoeal disease among children in the South-eastern Nigeria, particularly in Abakaliki and its environs, and the rising trend of resistance to antimicrobial agents used for treating diarrhoeal infections in the area, necessitated this investigation. In Ebonyi State south-eastern Nigeria where this study was conducted, diarrhoea episode represents more than 80% of hospitalized paediatrics cases from December to April each year and about 10% during the other months, with mortality rate estimated to be 7.5% (Ogbu et al. 2006: unpublished observation). This study was the first systematic attempt to assess the microbiological spectrum and antibiotic sensitivity profile of the aetiology of infantile diarrhoea disease in the South-eastern Nigeria with the view to providing scientific information required for effective public health interventional efforts and adequate management of the disease. The public health implications of findings are discussed as they affect the primary health care delivery system in Nigeria and other developing countries with similar setting.

Materials and Methods

Study Area

Ethical consideration

Study population/sampling technique

Laboratory Analysis

Treatment Strategies

Results

Of the 150 children diagnosed with diarrhoea (cases), at least one enteropathogen was detected in 122(81.3%) of them, while among the 50 children without diarrhoea (controls), only 4(8.0%) had enteropathogen (Odd Ratio=50.1, 95% CI.,45.7-54.5; Relative Risk=10.2, 95% CI.,7.5-12.9). Among all samples tested, Rotavirus was the single most predominant pathogen and was detected in 35(23.3%) cases but non in the controls. The pathogens of bacterial origin occurring with the highest frequency among the cases included Escherichia coli (15.3%), Salmonella species (11.3%), Klebsiella species (7.3%) and Enterobacter species (6.0%), while among the controls, E. coli (4.0%) recorded the highest prevalence (Table 1).

Figure 1

Table 1: Prevalence of enteropathogens among children with diarrhoea (cases) and Children without diarrhoea in Abakaliki south-eastern Nigeria

Entamoeba histolytica an enteric parasite was detected in 5(3.3%) of the cases but non in the controls. Other enteric parasites namely, Giardia lamblia and Trichuris trichiura were isolated from both the cases and the controls (Table 1).

The frequency of occurrence of the enteropathogen generally decreased with increase in the age of the infants with diarrhoea. Infants aged 0-12 months old recorded the highest frequency of enteropathogens followed by those aged 13-24 months old. Among these two age categories, Rotavirus (38.1% vs. 28.3%), E. coli (21.4% vs. 18.9%), Salmonella species (19.0% vs. 11.3%), Klebsiella species (14.3% vs. 9.4%) and Enterobacter species (11.9% vs. 7.5%) were the most predominant aetiological agents detected (Table 2).

Figure 2

Table 2: Age-related prevalence of enteropathogens among children with diarrhoea in Abakaliki south-eastern Nigeria

The antibiotic susceptibility patterns of the bacterial isolates are shown in Table 3. Results indicated that Enterobacter species, Shigella species and Campylobacter species exhibited a 100% susceptibility to oflaxacin, gentamycin and ciprofloxacin. All the bacterial isolates showed a 100% resistance to septrin, while E. coli, Salmonella species, Campylobacter species and Yersinia enterocolitica exhibited a 100% resistance to augmentin. Oflaxacin, gentamycin and ciprofloxacin appeared the more effective antibiotics as all the bacterial isolates showed a 75-100% susceptibility to them.

Figure 3

Table 3: Antibiotic Sensitivity Pattern of Bacterial Isolates from Children with Diarrhoea in Abakaliki South-Eastern Nigeria

Discussion

Infantile acute gastroenteritis of microbial origin is said to still constitute a frequent problem, with high mortality rate in developing countries and high impact on health costs in industrialized countries [₁₇]. In this present study, it was established that as high as 83.1% of cases of acute infantile diarrhoea in Abakaliki, south-eastern Nigeria was associated with enteropathogenic microooganismsms and was considerably higher than the frequency of the pathogens in the controls (8.0%). This was comparable to the outcome of studies in Calcutta, India [₅], Sao Paulo, Brazil [₁₈], and Santiago, Chile [₁₉], were intestinal pathogens were respectively detected in 81.5%, 72.8% and 73.7% of children with acute diarrhoea and the frequency was significantly higher than in the controls. Our result suggests that other causes or pathogens beyond the scope of this investigation may have been responsible for the outstanding 16.9% diarrhoeic cases. Earlier similar studies conducted in Boston, USA; Copenhagen, Denmark; and Bahia, Brazil, indicated that possible aetiologies for infantile diarrhoea cases include currently unknown gastrointestinal infections, nongastrointestinal illnesses and dietary/environmental or other non-infectious factors [₈,₁₀,₂₀].

Rotavirus was found to be the most common pathogenic agent detected in this investigation. A number of earlier studies in both developed and developing countries, have shown viruses, especially rotavirus to be a leading cause of gastroenteritis in children [₉₂₀₂₁]. And the recent estimates of diarrhoea-related childhood deaths gave an estimated 611,000 (range 454,000-705,000) rotavirus-related deaths [₇]. However, other viruses that have been implicated in childhood diarrhoea include adenovirus, norovirus, sapovirus and calcivirus [₉,₂₀,₂₁]. Although these other viruses were not investigated in this present study, the possibility that any of them might have also contributed to the diarrhoea in this study may not be completely ruled out. This finding underscores the importance of the integration of viral diagnosis in the assessment of the microbiological profile of aetiological agents of infantile diarrhoea especially in the developing countries. It was suggested that a combination of microscopic examination of stool samples with specific enzyme immuno-assays (EIA) to detect virus antigen in stool specimens may be suitable for routine diagnostics [₂₂].

Although the spectrum of bacterial isolate implicated in acute childhood diarrhoea varies from one region to the other, E. coli and Salmonella species were the commonest bacteria pathogens isolated in this investigation and this was in conformity with findings from Sao Paulo Brazil [₂₀] and Bissau, Guinea Bissau [₂₃]. Both E. coli and Salmonella species are reported to be very commonly associated with enteric diseases in developing countries and are more important to the epidemiology of diarrhoea in poorer areas [₂₄,₂₅,₂₆]. In this study, a number of the cases with the acute diarrhoea were from families of higher socioeconomic class, however, the great majority of them were from socioeconomically deprived group inhabiting low income areas and the suburbs where little basic amenities are available. Furthermore, in this latter group, malnutrition is a predominant feature and is known to play significant role in the severity of enteric infection [₃]. These factors may have influenced the outcome of this investigation.

The occurrence of enteric infections of parasitic origin in the present study was relatively low, though E. histolytica and G. lamblia were isolated from 3.3% and 2.7% of the cases respectively. Similar studies in various parts of the world have consistently indicated that enteric parasites were less frequently associated with acute infant diarrhoea compared to pathogens of viral and bacterial origin [₂,₅,₁₈].

Our result showed that the majority of the enteric pathogens were detected among the cases who were 24 months of age and less, which may be said to corresponds to the period when children's contact with environmental pathogens increases dramatically. This is in agreement with findings from previous studies in Brazil, Denmark and Turkey [₉,₁₀,₂₇].

Because specific antimicrobial treatment may be required to supplement supportive anti-dehydration treatment which is the cornerstone of therapy of acute infant diarrhoea, selective use of antimicrobial agents therefore, cannot be overemphasized. This is vital especially in the developing countries, where inadequate health services, inadequate drug supplies, non-adherence to treatment strategies and dubious drug quality all favour the emergence of microbial resistance [₂₈]. Therefore, it is worth noting that one outcome of the increased availability and usage of antimicrobial agents for symptomatic treatment of illness has been the emergence of antimicrobial resistance. This was clearly evident from this study where up to 100% resistance was observed in two to three antibiotics (septrin, augmentin and ampicillin) by E. coli, Salmonella species, Campylobacter jejuni, and Yersina enterocolitica. This is of particular concern in the developing world including Nigeria because fewer affordable, appropriate, and effective treatment options such as ciprofloxacin and oflaxacin are readily available in most rural communities. It has become increasingly important to monitor patterns of resistance as the antimicrobial susceptibility of bacterial pathogens which contribute significantly to the burden of infant diarrhoea is declining.

In conclusion, it is important to state that our inability to screen for other potential enteric pathogens particularly viruses (e.g., adenovirus, norovirus, sapovirus and calcivirus), the rather low population size of cases and the limited number of antibiotics used in the sensitivity test were among the limitations of this study. Also the investigation was conducted during the epidemic season and there is a need to perform similar study in the non epidemic season for the purpose of comparison. Nevertheless, the present study has provided insight into the burden of infantile diarrhoea in Nigeria. As a public health measure to reduce the disease burden, an integrated package of immunization services and other childcare programmes need to be implemented in addition to well-focused health-education messages to improve treatment-seeking behaviour for childhood diarrhoea as well as improved personal and environmental hygiene.

Acknowledgement

Correspondence to

C.J. Uneke Department of Medical Microbiology, Faculty of Clinical Medicine, Ebonyi State University, P.M.B. 053 Abakaliki- Nigeria Tel: 234-08038928597; E-mail: unekecj@ yahoo.com