When sheep walk in circles, it usually signals a neurological problem. The most common cause is a bacterial brain infection called listeriosis, sometimes known as “circling disease.” Less often, parasitic cysts, vitamin deficiencies, or prolonged confinement in small spaces can trigger the same behavior. A viral video from Inner Mongolia in 2022 brought widespread attention to this phenomenon, but most cases have a straightforward medical explanation.
Listeriosis: The Most Common Cause
Listeriosis is caused by a bacterium called Listeria monocytogenes, which lives in soil, mud, and rotting plant material. Sheep pick it up while grazing, and the bacteria can travel along a nerve in the face directly into the brainstem. Once there, it creates infectious lesions in the parts of the brain responsible for balance, coordination, and spatial orientation. The damage is typically one-sided, which is why affected sheep tilt their heads and drift into circles rather than walking straight.
The condition was first described in 1933 in New Zealand and has been recognized in ruminants worldwide ever since. Because the infection damages specific cranial nerves on one side of the face, a sheep with listeriosis often shows a drooping ear, a slack lip, or a tilted head alongside the circling. Depression, loss of coordination, and eventually collapse and inability to stand can follow. The circling itself is not deliberate. It’s the result of the brain sending lopsided signals to the muscles.
Treatment with antibiotics is possible but outcomes vary widely. Studies in cattle (where more data exists) show survival rates ranging from under 25% to around 80%, depending on how early treatment starts and which antibiotic is used. The overall takeaway from veterinary research is that mortality remains high despite treatment, particularly once neurological signs are advanced. Sheep that are still eating and drinking when treatment begins have a better chance.
Brain Parasites and “Gid”
A tapeworm called Taenia multiceps can also cause circling in sheep. Dogs, foxes, and jackals carry the adult tapeworm in their intestines and shed eggs in their feces. Sheep swallow the eggs while grazing, and the larvae migrate through the bloodstream to the brain, where they develop into fluid-filled cysts called Coenurus cerebralis. These cysts can grow to 5 or 6 centimeters across, roughly the size of a golf ball, and press against brain tissue.
The resulting condition goes by several old farming names: gid, sturdy, or staggers. Symptoms include stumbling, blindness, head tilting to one side, and circling. Unlike listeriosis, which tends to progress over days, gid can develop more slowly as the cyst gradually enlarges. The pressure on surrounding brain tissue determines the symptoms, so two sheep with cysts in different locations may behave quite differently. Surgical removal of the cyst is sometimes attempted in valuable animals, but prevention through deworming farm dogs is far more practical.
Vitamin B1 Deficiency
Thiamine (vitamin B1) deficiency causes a condition called polioencephalomalacia, which literally means softening of the brain’s outer layer. The brain depends heavily on thiamine to produce energy from glucose. Without enough of it, neurons in the outer brain begin to die, and the sheep develops neurological signs: a characteristic “stargazing” posture with the head pushed upward, pressing the head against walls or fences, blindness, wobbling, and sometimes circling. Without treatment, the condition progresses to seizures and death. Unlike listeriosis, thiamine deficiency tends to affect both sides of the brain more evenly, so the circling is less pronounced and other symptoms like stargazing and head pressing are more prominent.
How Circling Diseases Differ From Scrapie
Scrapie is a fatal brain disease in sheep caused by misfolded proteins called prions, and it occasionally causes circling too, which can create confusion in diagnosis. The key differences are timing and accompanying signs. Scrapie develops slowly over months, and its hallmark symptom is intense itching. Affected sheep scrape themselves against fences and posts obsessively, creating bald patches. They also show exaggerated responses to noise or touch, grinding their teeth, and a wide-based stance. Listeriosis, by contrast, comes on within days, produces obvious one-sided facial drooping, and does not cause itching. A veterinarian looking at a circling sheep will check for facial asymmetry, because one-sided paralysis strongly points toward listeriosis rather than scrapie or other causes.
The Viral Video From Inner Mongolia
In November 2022, footage from a farm in Inner Mongolia showed dozens of sheep walking in a tight, nearly perfect circle. Chinese state media reported the behavior had continued for 12 days, and the video spread rapidly online. Experts were skeptical from the start.
Andrew Fisher, a professor of cattle and sheep production medicine at the University of Melbourne, pointed out several problems with the listeriosis explanation that many outlets suggested. In a real outbreak, only 1 to 10 percent of a flock would be affected, not half of it. Sick sheep don’t walk in neat concentric circles. They loll in irregular, individual patterns and quickly become too ill to keep walking. They’d also show a range of other neurological symptoms, and some would die.
A veterinary researcher quoted by ABC News, Dr. Doyle, was more blunt, calling the video “a little hoax-y.” Sheep cannot go 12 days without food and water, which means they were leaving the circle regularly, making the “nonstop” claim misleading. The near-perfect circular shape also suggested something had been placed in the center to guide them.
Fisher offered one plausible non-disease explanation: stereotypical pacing. When animals are confined in small, barren spaces with little stimulation, as sometimes seen in poorly designed zoo enclosures, they can develop repetitive movement patterns. The sheep in the video appeared to be in a small pen. Once a few sheep begin pacing a fixed path, the strong flocking instinct of the species means others will fall in line. Sheep are followers by nature, and in a confined space with nothing else to do, a circular rut can become self-reinforcing.
What Healthy Circling Looks Like
Not all circling is cause for alarm. Sheep are intensely social animals with a powerful instinct to follow the animal in front of them. When startled or herded, they naturally bunch together and move as a group, sometimes curving into circular paths. Shepherds have long exploited this tendency, using food or positioning to guide flocks into circular movement for counting, sorting, or penning. The difference between normal flock behavior and a medical problem is straightforward: healthy sheep stop circling when the stimulus is removed, they respond to food and water, and they don’t show neurological signs like head tilting, facial drooping, or blindness.
If a single sheep circles persistently, especially with a head tilt, drooling, or drooping on one side of the face, a brain infection or parasite is the most likely explanation. If multiple sheep in a flock begin circling at the same time with no other symptoms, confinement stress or a behavioral trigger is more probable than disease.