International Disease Detectives Discover Cause of Disease in EthiopiaPosted on by
Mystery Illness in Ethiopia
A strange new illness was spreading throughout Tigray, the northern region of Ethiopia. People living in remote homes and villages developed swollen, painful abdomens and then lost weight. Some of them had trouble breathing as the fluid in their abdomens crowded their lungs.
Three or four family members in one household might become ill, while others living in the same household did not. In some families, everyone died from the disease. Even children as young as 5 years old became too weak to move, their abdomens swollen with up to four liters of fluid. People were sick, even dying, from an illness that demonstrated symptoms commonly seen in liver disease. But what was causing it?
The Investigation Begins
In 2005 a multidisciplinary team began an investigation into the disease and its causes under the principle of the “One Health Approach.” The team included physicians, veterinarians, epidemiologists, anthropologists, and environmental and plant scientists. They came from the Ethiopia Ministry of Health and Ethiopia Health and Nutrition Research Institute (EHNRI), the Ethiopian Ministry of Agriculture, WHO-Ethiopia, Addis Ababa and Mekele Universities, Tigray Regional Health Bureau and Tigray Agricultural and Rural Development Bureau. Despite their efforts, the mystery remained unsolved. In 2007, the ministry of health and EHNRI asked CDC and other partners to join the team and help them investigate the outbreak of “unidentified liver disease (ULD).” Since 2005, more than 1,200 people had been diagnosed, and many had died.
The 2007 investigation ruled out infectious diseases as the cause and suggested that the disease may be related to something in people’s diets. A year later, CDC staff from the Health Studies Branch and Division of Viral Hepatitis travelled to Ethiopia to join another investigation. Teams walked to remote villages or homes, some as far as four hours away, to gather information from households with and without ULD.
Although they did not find a definite cause for ULD, epidemiologists narrowed the list of possibilities. They found that grain samples gathered from household farms contained low levels of two types of plant-based liver toxins known as pyrrolizidine alkaloids (PAs). The PAs were found in a common weed that was harvested along with the grain. Scientists believed that the cause of the outbreak might be exposure to a toxic PA from eating contaminated grain or animal products.
The Plot Thickens
CDC epidemiologists knew they needed more information to come to solid conclusions, so they recommended collecting more grain and other food samples for testing, establishing a surveillance system, and collecting physical evidence from ULD patients.
In 2009, EHNRI established a surveillance system, and in 2011, once again requested CDC assistance to develop tools to gather the needed evidence. Investigators collected medical histories, conducted physical exams, and gathered blood and urine specimens and environmental samples for PA testing.
Test results showed that 50% of the ULD patients had been exposed to PAs. Results also showed that ULD patients, their family members, and even other members of the community who were not sick had been exposed to PAs. However, ULD patients had higher PA levels than village members who had no ULD symptoms.
The study also found that households with cases of ULD and those without ate the same foods and drank the same beverages. However, investigators discovered a very important difference in ULD and non-ULD households. People in households without ULD were more likely to separate the weeds from their crops both before and after harvest than people in households with the disease.
Even though researchers can now more accurately pinpoint the cause of this deadly disease, there is still no cure. So to eradicate the disease in Tigray, eliminating the source of the toxin is essential.
To do that, the health ministry, EHNRI and extension health workers are educating the community about the importance of separating weeds during the growing season and during the harvest. Health workers also are encouraging farmers to monitor the health of livestock that can contract the disease by eating toxic weeds. Not only can the animals become ill or die, but also consuming milk or meat from contaminated animals can expose people to toxic PAs.
ULD Investigation Crosses Finish Line
Thanks to the skilled work of the “One Health” team and collaboration of local and overseas institutes, the cause of liver disease in Tigray is no longer unidentified. The disease is now called “pyrrolizidine alkaloid-induced liver disease (PAILD)” for the toxic PAs that cause the illness. More important, grain farmers in Ethiopia now have the information they need to protect themselves and their families from a once mysterious and sometimes fatal disease.
To learn more about this investigation, go to http://www.cdc.gov/nceh/stories/Ethiopia.html