Acute interstitial pneumonia (AIP) is a respiratory disease characterized by lung inflammation, edema and emphysema in cattle. According to Josh Szasz, DVM, with Five Rivers Cattle Feeding, it primarily used to describe a sporadic respiratory disease.

Recognized as a health issue for quite a long time in North America, AIP has been well documented in pasture-managed cattle, Szasz said. It results in high economic losses, it’s more common in heifers and it’s more commonly seen late in the feeding period and more often during summer months.

Szasz, along with Paige Schmidt, DVM, with Overton Vet Services, presented “Cattle Health Hotspots: Cracking the Code on AIP in Cattle” at the most recent CattleCon.

When describing disease, “acute” refers to conditions that develop suddenly and are typically short-lived. “Chronic” refers to conditions that develop slowly and persist for prolonged periods.

Schmidt said the cause of AIP remains unknown at this time. “It could have a multifactorial disease pathway,” she said, listing bovine respiratory syncytial virus (BRSV), the rapid intravenous injection of 3-methylindole (3-MI) and even dust as things vets are looking at. “The specific causal pathway is unclear.”

She added that treatment and prevention for AIP is not as successful as for other diseases – it has a very quick onset.

How do you know if a cow has AIP? Szasz said unfortunately, it has non-specific respiratory signs. Often seen are an acute onset of labored breathing; a wide-based stance; and acute death.

In that same vein, there are no defined treatments. He mentioned anti-inflammatories, antibiotics and supportive care. “We don’t know a cause so we don’t know what a proper treatment would be,” he admitted.

Why AIP is a Concern

Schmidt compared AIP to a similar affliction, bronchopneumonia (BP). In BP, the bottom lung sections are affected – the fluid build-up is heavy and it settles. With AIP, it affects the entire lung cavity (in a checkboard appearance).

Because of the fast onset of AIP, approximately 37% of animals are not treated, another 37% get one treatment, 19% get two treatments and 12% get three or more treatments.

A study is currently underway at a feedlot in Kansas looking at the lungs in all necropsies, specifically looking at lesions. What’s been found so far is that BP is the most common disease found in mortalities (36.6%), then a combination of BP and AIP (35.8%) and then AIP (10%) – the rest are undefined.

In the feedyard and necropsy diagnosis comparison, 357 animals were enrolled to compare necropsy diagnosis to feedyard diagnosis. It was found that sex played a large role – 252 heifers had AIP vs. 105 steers.

A silver lining: For those raising beef cattle, there isn’t a lot of AIP found in Holsteins or crossbreeds.

As for treatment pulls, it was roughly broken down into quarters. Some animals had no treatment (27.2%), one treatment (29.4%) or two treatments (24.5%); the remaining 18.9% were given three or more treatments, making this a costly disease to handle regardless of the plan of attack.

The economics of AIP mortalities are real. Szasz said that losing an animal to the disease can mean a loss of over $2,300.

Schmidt added that in a study of about 60,000 lots, about 20% of them saw at least one AIP mortality (two deaths per 1,000 animals). These mortalities had an average of 120 – 140 days on feed before death.

The time of year should also raise concern. Szasz noted the monthly death loss from AIP peaks from June through August. While it is more common in southern areas vs. northern areas, hotter, more humid summers farther north are becoming more common.

Beef cattle death loss from AIP has been measured since 2020, and so far, it saw a peak in 2022. It’s been on a slight decline since then.

Even though methods of prevention and treatment are still uncertain, “the current questions and research are headed in the right direction to crack the code for AIP in feedlot cattle,” Schmidt concluded.