Something very strange is going on with the chimps and baboons in Uganda. For several years, researchers working in Kibale National Park in Western Uganda have noticed a growing number of primates suffering from bizarre deformities, such as missing limbs, patchy fur, cleft lips, concave faces, or flattened noses.
In a new study published in the journal Science of The Total Environment, researchers say they may have found the culprit: agricultural pesticides.
In Sebitoli, an area of the national park, the team found that at least 16 out of the 66 chimpanzees monitored (25 percent) showed physical abnormalities, including reduced nostrils, cleft lip, limb deformities, reproductive problems, or a loss of pigment to their skin and fur. At least six of 35 baboons (17 percent) were photographed with similar severe nasal deformities. None of these primates appeared to show any signs of an infectious lesion.
Elsewhere in the park, there’s been just two reports of a wild primate with some kind of deformity, one of which was likely to be congenital.
The researchers headed to Sebitoli to find out what was going on. They reported that farmers and workers from two major tea factories revealed the use of eight pesticides: glyphosate, cypermethrin, profenofos, mancozeb, metalaxyl, dimethoate, chlorpyrifos, and 2,4-D amine.
Further investigation into the level of pesticides found in the area’s land, waters, and plants showed that levels of total DDT and chlorpyrifos exceed recommended limits in fresh maize seeds and in fish. It’s worth considering that the primates of Sebitoli are often reported to raid the maize crops in nearby gardens and farms.
The pesticide DDT is the most notorious of all these mentioned. Although banned under the UN Stockholm Convention due to its well-established effect on the environment, it is permitted in African countries where malaria remains a major health problem, such as Uganda.
As the researchers themselves note, they did not find a causal relationship, meaning they didn’t find an explicit link between the pesticides and the facial abnormalities. After all, obtaining the urine of dozens of wild chimps is no small feat. Nevertheless, they argue there is ample evidence to back up their correlations.
“At least three pesticides (chlorpyrifos, mancozeb, DDT) used in this area affect thyroid hormone (TH) signalling," the authors write in the study. "TH is implicated in cranial facial organogenesis. Abnormal maternal or neonatal levels of TH have been associated with facial dysplasia, including cleft palate and lip in human new-borns."
However, they later note that they "cannot rule out the possibility that others factors could contribute to the dysplasia.”
“Although the causal nature of the relationship between pesticides and deformities remains to be verified, there is reason for concern.”
You can read more on the story and see images of the afflicted chimpanzees on The Verge.
Edited 29/08/17: The sentence "this is a causal relationship" was changed to " they did not find a causal relationship"