Aspergillosis in Ox: Fungal Infection, Respiratory Signs, and Reproductive Loss

Aspergillosis is a fungal infection caused by Aspergillus species, most commonly Aspergillus fumigatus. These fungi are common in the environment, especially in moldy feed, spoiled hay, damp bedding, and dusty housing. In cattle, the disease is usually sporadic rather than highly contagious from animal to animal.

In oxen and other cattle, aspergillosis is best known for causing mycotic abortion. The fungus is thought to enter through the respiratory or digestive tract, then spread through the bloodstream to the placenta. Severe placentitis can lead to pregnancy loss, usually in mid- to late gestation.

Some animals may also develop respiratory disease, especially if they inhale large numbers of spores or already have stressed airways. Signs can include cough, nasal discharge, faster breathing, poor appetite, and reduced performance. In severe cases, fungal infection may extend deeper into the lungs or become more generalized.

Because Aspergillus is everywhere in the environment, finding the organism on a swab alone does not prove disease. Your vet usually needs tissue evidence showing that fungal hyphae are actually invading the placenta, lungs, or other affected tissues.

Aspergillosis is caused by exposure to Aspergillus spores in the environment. These spores thrive in moldy organic material, including poor-quality hay, spoiled silage, damp grain, old bedding, and dusty barns with weak ventilation. Cattle are exposed regularly, but disease usually develops only when spore load is high or when normal defenses are overwhelmed.

In reproductive cases, the fungus is believed to enter through the oral or respiratory tract and then spread through the bloodstream to the placenta. This leads to severe placentitis, which reduces oxygen and nutrient delivery to the fetus. The result may be abortion, stillbirth, or delivery of a weak calf.

Respiratory disease can happen when spores are inhaled deeply into the airways. Animals under stress, those housed in dusty conditions, or those with concurrent illness may be more vulnerable. Long-standing mold exposure can also increase the chance that multiple animals in a group are challenged at the same time.

This is not usually considered a straightforward contagious disease passed directly from one ox to another. In most herds, the bigger issue is the shared environment. That is why feed quality, bedding management, moisture control, and ventilation matter so much.

Diagnosis starts with the history. Your vet will ask about pregnancy stage, recent abortions, respiratory signs, feed changes, silage quality, hay storage, bedding moisture, and whether other animals are affected. That context helps separate fungal disease from more common bacterial, viral, toxic, or nutritional problems.

For abortion cases, the most useful samples are usually the placenta and fetus. Your vet may submit placenta, fetal stomach contents, lung, skin lesions, and other tissues to a veterinary diagnostic laboratory. Histopathology is especially important because Aspergillus can contaminate samples after abortion. A strong diagnosis usually requires fungal hyphae to be seen invading damaged tissue, not just a positive culture.

For respiratory disease, your vet may recommend a physical exam, temperature check, bloodwork, ultrasound, endoscopy in selected cases, or sampling of airway secretions. Fungal culture, cytology, and tissue biopsy may be considered if pneumonia is not responding as expected or if lesions suggest a fungal process.

Because many causes of abortion and pneumonia can look similar, your vet may also test for other infectious diseases at the same time. That broader workup is often the most practical path, especially when herd health decisions depend on getting the diagnosis right.

Prevention centers on reducing mold exposure. Check hay, silage, grain, and bedding regularly for heating, spoilage, visible mold, musty odor, or water damage. Discard suspect feed rather than blending it into the ration for pregnant animals. Good storage, dry handling areas, and prompt cleanup of wet organic material all help lower fungal burden.

Ventilation matters too. Dusty, damp, poorly ventilated housing allows spores to build up and irritate the respiratory tract. Improve airflow where possible, reduce overcrowding, and keep bedding dry. These steps support lung health even when aspergillosis is not the final diagnosis.

For abortion prevention, work closely with your vet on a herd plan. Promptly remove aborted fetuses and placentas, use gloves and good hygiene during cleanup, and submit samples for diagnosis instead of assuming the cause. Knowing whether the problem is fungal, bacterial, viral, or toxic changes the next steps.

If your farm has had a recent case, review feed sourcing, storage practices, and pregnancy-group management. A practical prevention plan does not have to be all-or-nothing. Small improvements in moisture control, forage turnover, and sample submission can meaningfully reduce future losses.