Chabertiosis in Sheep

Chabertiosis is a parasitic disease caused by Chabertia ovina, a nematode often called the large-mouth bowel worm. In sheep, the adult worms live in the colon, where heavy infections can damage the lining of the large intestine and trigger inflammation, congestion, ulceration, and small areas of bleeding.

This parasite is considered a large-intestine worm of small ruminants. Clinical disease is usually most noticeable when worm burdens are high. Affected sheep may become unthrifty, pass soft feces with mucus, and sometimes have blood-streaked manure. Young animals and sheep under significant stress are more likely to show obvious illness.

For many flocks, chabertiosis is part of a broader internal parasite picture rather than a stand-alone problem. That matters because treatment and prevention often work best when your vet looks at the whole parasite-control plan, not only one worm species.

Chabertiosis develops when sheep ingest infective parasite stages while grazing or eating feed contaminated with manure. The parasite has a direct life cycle, so eggs passed in feces develop on pasture and are then picked up by other sheep. That means pasture contamination, stocking density, weather, and grazing pressure all influence risk.

Disease is more likely when sheep are exposed to a high worm burden or when the flock is under stress. Merck notes that outbreaks are seen mainly in young animals or under severe stress, because immunity tends to develop relatively quickly. Even so, chronic low-grade infection can still reduce thrift and growth.

In real-world flock medicine, chabertiosis often overlaps with other gastrointestinal parasites. Mixed infections can make signs more noticeable and can complicate treatment decisions. Your vet may recommend looking beyond one parasite and building a broader parasite-control strategy that includes fecal monitoring and pasture management.

Diagnosis usually starts with a history and flock-level exam. Your vet will look at age group affected, body condition, manure quality, pasture exposure, recent deworming history, and whether multiple sheep are showing poor growth or diarrhea. Because many internal parasites cause overlapping signs, diagnosis is often based on a combination of findings rather than one clue.

A fecal flotation or fecal egg count may help detect strongyle-type eggs, but these tests have limits. Parasite eggs may be missed when burdens are low or when worms are not yet shedding eggs. That is one reason your vet may repeat testing, interpret results at the flock level, or combine fecal results with clinical signs and treatment response.

In some cases, especially when losses occur, diagnosis is confirmed through postmortem examination. Necropsy can identify adult worms in the colon and help rule in or out other important causes of diarrhea, weight loss, and poor thrift. This can be especially helpful when a flock has mixed parasite problems or suspected dewormer resistance.

Prevention focuses on lowering pasture contamination and avoiding unnecessary deworming. Work with your vet on a flock health plan that includes parasite control, body-condition monitoring, and clear steps for sick or thin sheep. Sheep that isolate, lose weight, or act abnormally should be evaluated promptly so problems do not spread through the flock.

Good prevention usually includes rotational grazing, avoiding overstocking, keeping feed and water areas cleaner, and reducing manure contamination where sheep eat. Quarantining and evaluating new arrivals can also help prevent bringing resistant parasites onto the farm.

Fecal monitoring is important because internal parasite control in sheep is no longer one-size-fits-all. Antiparasitic resistance is a recognized veterinary concern, so your vet may recommend targeted selective treatment and follow-up fecal egg counts instead of routine blanket deworming on a fixed schedule. This approach can help preserve drug effectiveness while still protecting flock health.