Diarrhoea also proved to be seasonal, with the pre-monsoon months having double the risk compared to the rest of the year. When we later matched this with local data, it was also true for Nepali children. Although the exact reason for this seasonal increase is not known, it does coincide with the main housefly season in Nepal.
Flies lay their eggs in human stool, are attracted to food in the kitchens, so faecal bacteria on their feet contaminate the food. One of the biggest breakthroughs in Nepal is the program to eliminate stool from the open environment where it can attract flies. Dubbed Open Defecation-free Zones, the installation of water-trap toilets in these areas has greatly reduced the risk of diarrhoea to both tourists and locals.
Foreign travelers and expatriates are like Nepali children in one key respect: they are both equally susceptible to bugs that cause diarrhea. We studied expatriates who moved to Kathmandu and found out that they each had an average of 3.2 episodes of diarrhea per person in the first year. This turned out to be the exact same number of episodes that an average Nepali village child would have.
We were also able to show that long-term expatriates gradually developed immunity to the diarrhea bugs, just as Nepali children do. Over a period of 2-5 years, the risk of getting diarrhoea, and the severity of the illness, goes way down. This is why diarrhoea is not a major problem among adult Nepalis.
Although antibiotics have greatly decreased the suffering of travelers and have helped support the tourist industry by giving visitors more confidence in traveling to Nepal, the wider availability and use of antibiotics by the general public in Nepal has resulted in more resistant bacteria. The antibiotics that treat diarrhoea have changed several times in the last 35 years.
The long-term solution to travelers’diarrhea is to improve the hygiene in the host country, which improves the health of both locals and foreigners. Restaurant hygiene has already improved a great deal, and there is far less stool in the open. Nepal pioneered the diagnosis and treatment of travelers’ diarrhoea in the world and has also demonstrated that decreasing the risk of diarrhoea among locals can also reduce the risk for foreigners.
We look forward to a time when the level of hygiene in Nepal is such that children can grow up without the constant risk of illness, and the concept of travelers’ diarrhoea no longer needs to be discussed with travelers.
David R Shlim MD is the former Medical Director of the CIWEC Clinic Travel Medicine Centre, and a past president of the International Society of Travel Medicine.