Stephanie Akinyi and Betty Anyango, aged 30 and 33 respectively, are close sisters who spend a lot of time together.
While they both enjoy travelling together on weekend getaways and holiday vacations, Akinyi notes that she is always careful about what she eats while on the road.
“Unlike my sister who can eat anything and not become sick, my stomach is very sensitive. I have to be sure of where the food has come from. Otherwise, I will have serious diarrhoea that ends up ruining all the vacation fun for me.”
The siblings share common interests as well as many personality traits. However, their blood types are different. Akinyi’s blood group is A while her sister’s is O. And this difference may be the cause of her stomach “troubles”.
A new study published in the Journal of Clinical Investigation shows that a type of bacterium known as Enterotoxigenic E-coli (ETEC) that is associated with diarrhoea among travellers and children in developing nations such as Kenya causes severe disease in people with blood type A.
Researchers from the Washington University School of Medicine in St. Louis who conducted the study stated that the bacterium releases a protein which latches onto intestinal cells in people with blood type A but not blood type O or B.
“We think this protein is responsible for this blood-group difference in disease severity. A vaccine targeting this protein would potentially protect the individuals at highest risk for severe disease,” said Dr James Fleckenstein, senior author of the study and associate professor of medicine at Washington University.
The ETEC bug is responsible for millions of diarrhoea cases worldwide as well as hundreds of thousands of deaths yearly, especially among children who are most vulnerable to the adverse effects of the disease.
Diarrhoea is a leading cause of Kenya’s high child mortality rate which currently stands at 52 deaths per 1,000 births according to the 2014 Kenya Demographic and Health Survey.
This implies that at least one in every 19 children born in Kenya dies before reaching their fifth birthday.
Aside from children, diarrhoea caused by ETEC also affects adults who consume food or drink water contaminated with it.
People react differently to the bacterium. Upon infection, some may develop severe, cholera-like and watery diarrhoea that can be lethal.
Others experience unpleasant symptoms but recover easily, while some people do not get sick at all.
Years ago, doctors noted that children naturally infected with ETEC in Bangladesh seemed to get sicker if they had blood type A but the reason for this was never tested.
This mystery prompted researchers from Washington University in collaboration with scientists at Johns Hopkins University, the National Institutes of Health as well as the Naval Medical Research Centre based in the US to look at the link between blood types and ETEC diarrhoea.
In controlled human infection clinical trials, researchers at Johns Hopkins University gave healthy volunteers a dose of ETEC strain originally isolated from a person in Bangladesh with severe, cholera-like diarrhoea. They then observed the volunteers for five days.
Those who developed moderate to severe diarrhoea were treated with antibiotics.
The disease manifests itself quickly. Therefore, anyone who was still healthy at the end of five days was considered unlikely to get sick later.
Nonetheless, any remaining healthy participants were also given antibiotics to clear the bacteria before going home.
Results of the research trial, which involved 106 people showed that people with blood type A got sick sooner and more seriously than those of other blood types.
More than 80 per cent of blood group A volunteers developed diarrhoea that required treatment compared with about 50 per cent of people with blood group B or O.
“The effect of blood group in people infected with this strain of ETEC bacteria was striking and significant. But it doesn’t mean that people should change their behaviour based on blood type,” the researchers said.
Dr Matthew Kuhlmann, a medical instructor and co-author of the study from Washington University says: “I don’t want anyone to think they’re safe because their blood group is not A.
“There are a lot of different species of bacteria and viruses that can cause diarrhoea. So, even though this blood-group association is strong, it doesn’t change your overall risk. You should continue taking the same precautions whatever your blood type.”
Basic hygiene — washing hands and purifying water —is the best protection against diarrhoeal diseases because it works against all kinds of organisms.
“But the people who suffer most from diarrhoea are small children. For them, and others who don’t have reliable access to basic sanitation or clean water, a vaccine could be lifesaving,” said Dr Kuhlmann.
Since the protein identified in this study is found in most ETEC strains, the researchers are hopeful that it would help in the development of vaccines that protect high-risk populations from the disease.