Lungworm Infection in Ox: Coughing, Breathing Trouble, and Pasture Risk

Lungworm infection in oxen is a parasitic disease of the lower airways and lungs, most often caused by Dictyocaulus viviparus. You may also hear it called parasitic bronchitis, verminous bronchitis, or verminous pneumonia. The worms live in the bronchi and trigger inflammation that makes breathing less efficient.

Affected animals often start with a cough and reduced stamina, then may develop faster breathing, open-mouth breathing, or obvious respiratory distress as the disease progresses. Secondary bacterial or viral respiratory infections can make signs more severe and recovery slower.

Lungworm is closely tied to pasture exposure. Infective larvae develop outside the animal and are picked up while grazing, so outbreaks are most common during grazing season and in areas with moisture, rainfall, or irrigation. Young, nonimmune cattle are often hit hardest, but older cattle can also become sick if immunity has waned or if they were not exposed enough to build protection earlier in life.

The usual cause is infection with the bovine lungworm Dictyocaulus viviparus. Adult worms in the airways produce larvae that are coughed up, swallowed, and passed in manure. On pasture, those larvae develop into the infective stage and are then eaten during grazing.

Warm, moist conditions help the parasite develop and spread. Risk tends to rise on wet pasture, in temperate climates with regular rainfall, and on irrigated ground. Heavy stocking density, repeated grazing of the same pasture, and mixing naive animals with carriers can also increase exposure.

First-season grazers are often most vulnerable because they have little or no immunity. Still, adults are not fully exempt. Older cattle may become ill if they have not had enough prior exposure to maintain immunity, or if they encounter a very heavy larval challenge. Carrier animals can quietly contaminate pasture and set the stage for herd-level problems.

Your vet will usually start with the history: coughing cattle on pasture, recent turnout, wet grazing conditions, and age or exposure status of the group. A physical exam may show increased breathing effort, abnormal lung sounds, and reduced tolerance for handling or exercise.

A Baermann fecal test is commonly used to look for first-stage lungworm larvae in fresh manure. This can be very helpful, but timing matters. Early infections may test negative before larvae are being shed, and some animals with severe lung inflammation later in the course may also have low larval output.

Because coughing and breathing trouble can also come from bacterial pneumonia, viral respiratory disease, aspiration, allergic airway disease, or other parasites, your vet may recommend additional diagnostics. Depending on the case, that can include herd-level assessment, bloodwork, ultrasound, necropsy of a deceased animal, or response-to-treatment monitoring.

Prevention focuses on lowering pasture exposure and building a practical herd parasite plan with your vet. Young grazing animals and newly introduced stock deserve extra attention, especially in wet seasons or on irrigated pasture. Rotational grazing, avoiding repeated heavy contamination of the same fields, and reducing overcrowding can all help lower risk.

Strategic deworming may be part of prevention, but it works best when paired with pasture management and herd history. Overusing dewormers can create other parasite-control problems, so treatment timing should be tailored to your farm rather than done automatically without a plan.

Watch for early warning signs during grazing season. A few animals coughing after exercise can be the first clue that a larger pasture problem is developing. Prompt veterinary review of coughing cattle, plus targeted testing and follow-up, can help prevent a mild outbreak from becoming a herd-wide respiratory event.