NIDIAG is an international collaboration on integrated diagnosis-treatment platforms, funded by the European Commission (EC). NIDIAG aims to develop an improved, patient-centred system for delivering primary health care in resource-constrained settings. NIDIAG will investigate three clinical syndromes, namely (i) persistent digestive disorders, (ii) persistent fever and (iii) neurological disorders, due to neglected tropical diseases (NTDs). The current study focuses on persistent digestive disorders, which are defined as diarrhoea or abdominal pain that last for at least 2 weeks.

While acute diarrhoea has been studied globally, few research activities have focused on the epidemiology, diagnosis and treatment of long-lasting diarrhoeal episodes (2 weeks and longer) in the tropics. The spectrum of possibly involved pathogens includes more than 30 bacterial, parasitic and viral infectious agents. This lack of data may be explained by the fact that people suffering from NTDs might only seek care at a late stage of the disease. Furthermore, health systems in affected regions are often weak and their primary health-care centres are often under-staffed and lack essential diagnostic equipment.

The hypothesis of this study is that development of an evidence-based syndromic approach can lead to better diagnosis and management of NTDs in patients with persistent digestive disorders. The study will be carried out in two West African countries (Côte d'Ivoire and Mali) and in two Asian countries (Indonesia and Nepal). The study will follow a "case-control" design and patients and controls will be prospectively enrolled. In order to address the knowledge gaps, three specific objectives will be pursued. First, the contribution of NTDs to the 'persistent digestive disorders syndrome' will be assessed. Second, the value of clinical features and rapid diagnostic tests (RDTs) for the diagnosis of target NTDs that give rise to persistent digestive disorders will be determined. Third, the clinical response to standard empiric and targeted treatment of several NTDs in patients with persistent digestive disorders will be evaluated. These objectives will provide a long-term benefit for the communities by improving the clinical decision-making process for the target NTDs and thus, better diagnostic work-up and patient management can be achieved in the study countries and other similar resource-constrained countries

Inclusion Criteria:

1. Individuals aged ≥1 year presenting with persistent diarrhoea (≥3 loose stools per days for ≥2 weeks; symptomatic group) and/or children (aged 1-18 years) with persistent abdominal pain (localized or diffuse abdominal pain lasting for ≥2 weeks, with possible intermittence/recurrence).
2. Individuals with written informed consent provided.

Exclusion Criteria:

1. Individuals in need of immediate intensive or surgical care.
2. Individuals who are unable or unwilling to give written informed consent.
3. Individuals who do not meet the inclusion criteria for being a case or control (e.g. people with acute diarrhoea).
4. Individuals with clinical jaundice (assessed by direct observation of the conjunctivae).
5. Individuals who are unable, in the study physician's opinion, to comply with the study requirements.
6. Individuals who are already participating in other ongoing diagnostic studies and/or clinical trials.

Individuals aged ≥1 year presenting with persistent diarrhoea (≥3 loose stools per days for ≥2 weeks; symptomatic group) and/or children (aged 1-18 years) with persistent abdominal pain (localized or diffuse abdominal pain lasting for ≥2 weeks, with possible intermittence/recurrence) will be recruited together with matched controls.