A Texas A&M research team identified Brucella abortus as the bacteria driving the spread of brucellosis in Cameroon’s livestock; the discovery overturns decades of assumptions and gives public health officials in the region a concrete target for controlling the disease.
The principal investigator, Dr. Angela Arenas-Gamboa, associate professor in the Department of Veterinary Medicine & Biomedical Sciences, led the team throughout the four-year study. A board-certified clinical pathologist by training, Arenas-Gamboa built her research career around zoonotic diseases, or illnesses transmitted from animals to people. The field is defined by protecting animal and human health in tandem and understanding the importance of the human-animal connection in diseases.
“If we can prevent the diseases in animals, we could prevent them in humans, making a very big impact,” Arenas-Gamboa said.
Brucellosis, a zoonotic bacterial infection, can affect livestock and be transmitted to humans through the consumption of raw milk and dairy products. Because of its potential to cause severe and chronic illness in humans, it continues to pose a notable public health concern in many regions worldwide. In the United States, the disease has been nearly eradicated, with fewer than 200 cases reported each year. That near-absence, while a public health success, makes it difficult to study domestically.
“The best place to study it and come up with new knowledge and interventions is in countries where the disease is endemic. That’s why we ended up in Cameroon,” Arenas-Gamboa said.
However, targeting an endemic region brought its own set of immediate challenges.
“Even though Cameroon is in Africa, and Africa is known to be endemic with high prevalence, we didn’t know anything specific about Cameroon,” Arenas-Gamboa said. “There was no data. So we had to start the planning process from scratch.”
Building that foundation required a massive, nationwide surveillance effort. The team combined practical fieldwork with statistical modeling to map the disease from the ground up.
“In order to have an idea of what is happening in the country, you need this number of animals throughout this part of the country, and you need to collect samples,” Arenas-Gamboa said. “Then the veterinarian comes in and says what the appropriate samples are based on how the disease behaves.
With the methodology in place, the team had to figure out how to navigate the country’s cultural boundaries to reach the farmers and access the livestock.
“Because we don’t speak the language and don’t know the local context, we recruited three Ph.D. students who were from the region. They were in charge of not only collecting the samples, but most importantly engaging the farmers and explaining what we were doing,” Arenas-Gamboa said. “You’re not only collecting samples, but you’re training people and teaching them about the disease. They’re basically getting trained to be the next generation of scientists in the country.”
The students’ extensive fieldwork ultimately paid off, yielding the data needed to effectively combat the disease. The team discovered the brucellosis outbreak was being driven by Brucella abortus, a species of bacteria that causes reproductive failure in cattle and debilitating, wavelike fevers and joint pain in humans.
“If you don’t know what species is present and you go in and try to control Brucella suis, but you don’t have it in the country, are you accomplishing anything? No,” Arenas-Gamboa said. “A lot of countries do that. They assume they have Brucella melitensis and go in and do an intervention on that. That wastes money, time, effort and credibility, because people don’t see results and stop trusting the process.”
Armed with this information, local health and agricultural leaders can now begin developing policies focused on controlling the disease’s spread in cattle populations.
“By understanding that the main problem comes from the cows, not from the sheep or the dog or the pig, you can tailor interventions toward that specific animal population,” Arenas-Gamboa said. “You teach the farmer, you push vaccination, you teach the veterinarian, you teach the ministry of public health. Their focus should be on livestock.”
With the animal results of the study now published, the team is turning its attention to the human population. The next phase of research will attempt to measure how widely brucellosis is circulating among people in Cameroon and how often it is being contracted.
“What we are going to do next is look at the prevalence in humans, see if doctors are actually aware of the disease and whether it is being misdiagnosed,” Arenas-Gamboa said. “We actually published a paper showing that brucellosis is frequently misdiagnosed as malaria. If a patient is not getting better on malaria treatment, they might have brucellosis.We also need to start developing vaccines for animals and for humans and new diagnostic tests.”
