The problem – Shigella and ETEC Diarrhoea
According to the WHO, diarrhoeal diseases are the most common illnesses in the world today. It has an enormous incidence of 1.7 Billion cases annually.
The number of international travellers is increasing annually; with an estimated 600 million people travelling from industrialized countries to developing countries in 2017.
600 million people
travelled from industrialized countries to developing countries in 2017 *
* UNWTO 2019 World Tourism Barometer Vol 17, Issue 2
Travelers: 180-300 million diarrhoea cases per year based on 30%-50% attack rate and number of travellers to endemic regions
Military: 1.1 million lost duty days per year in the US military due to diarrhoea
up to 50% due to ETEC and Shigella combined
Although typically considered a non-life-threatening inconvenience for travellers to endemic regions, Shigella and Enterotoxigenic Escherichia coli (ETEC) infections affect 30-50% of those travellers visiting resource-poor countries per year. In addition, an estimated 1.1 million service days are lost by US military personnel stationed in endemic countries.
While vaccine development against other enteric diseases, such as cholera and rotavirus infections have been successful, current technologies applied to Shigella and ETEC infections have been proven inefficient or not safe enough, and currently no vaccines against Shigella and ETEC diarrhoea are available to address this high medical need.
Diarrhoea in endemic populations
Diarrhoea, while also affecting adults, is the second leading cause of death among children under the age of five (18% of all causes), causing an estimated 2000 deaths daily and hospitalizing millions more, mostly in developing countries. In addition to such a high death toll, many more children suffer from diarrhoeal disease-associated malnutrition and its adverse consequences on physical and cognitive development (stunting). Enteric diseases like these often perpetuate the cycle of poverty in low-resource countries. The cost of the disease burden world-wide is in the range of multi-billion dollars.
Bacterial diarrhoea is treated with antibiotics; however, there is an increasing rate of resistance among Shigella strains that makes the management of the disease increasingly difficult.
In addition to the use of proven measures, a comprehensive approach to address diarrhoea is urgently required, including the development of innovative tools to fill current gaps in effective prevention strategies. Vaccines are a major tool for the prevention of diarrhoeal diseases but currently the only enteric diseases for which licensed vaccines exist are rotavirus, cholera (which provides partial ETEC protection), and typhoid. With a crowded vaccine schedule, there are significant advantages of combination oral vaccines, in terms of cost, ease of delivery and ultimate protection.
Furthermore, recent impact studies indicate that combination vaccines - especially ETEC and Shigella vaccines if combined or with another enteric vaccine - would have the greatest impact on saving lives and promoting the health of infants and children in the developing world and consequently would be commended from the perspective of cost-effectiveness. In addition, adding protection against these pathogens through an oral vaccine regimen would avoid the expanding complexity of and parental concerns about multiple injections in the already crowded EPI schedule.
Many attempts to develop vaccines for shigellosis and ETEC infections have failed and a number of current approaches are too complex and costly to provide an adequate solution for Low- and Middle-Income Countries (LMICs).
Despite improvements over the last decades of drinking-water quality, sanitation, and the implementation of current prevention and treatment interventions, diarrhoeal diseases remain a major cause of illness, death, and developmental disabilities such as stunting and mental and endocrine delays especially among children in LMICs under five years of age.
of children from diarrhoea every day
Shigella and ETEC
other enteric disease
UNWTO 2019 World Tourism Barometer Vol 17, Issue 2