The toxic exposure to asbestos is well known in humans, with many people diagnosed after workplace exposure, but the prevalence of the disease in animals is generally considered low. However, a quarter horse in Italy has been found to have had mesothelioma
The horse was brought to a veterinary clinic for what was suspected to be colic. The animal was emaciated and had a distended abdomen, as well as showing signs of respiratory congestion.
Despite extensive testing and treatment, the animal was euthanised after several days of failing to respond to treatment, and the subsequent autopsy revealed masses in the thoracic cavity. Through histopathology and immunohistochemistry, veterinarians made a diagnosis of epitheloid mesothelioma – the most common type of mesothelioma diagnosed in humans.
The results of the laboratory work, alongside the treatments provided to the animal, were published in Animals, a peer-reviewed veterinary sciences journal. The authors of the study speculated that the horse’s exposure to asbestos was likely by way of environmental contamination.
The article and its findings are particularly poignant because although mesothelioma is uncommon in humans, it is rarer in animals and particularly in horses, who spend most of their time outdoors.
“Mesothelioma can affect different species, including dogs, cats, cattle, sheep, goats and horses. The onset in horses is very rare,” the authors wrote. “Ours is a rare case of mesothelioma in the abdominal and thoracic cavities.”
Mesothelioma is incredibly rare in horses, with only 11 reported cases of the disease in horses since 1976.
“In most cases of equine mesothelioma, the diagnosis is made post-mortem at the slaughterhouse or during a clinical necropsy,” the authors wrote.
As mentioned previously, mesothelioma in humans is often due to legacy occupational exposure to asbestos, or it can be traced to the use of asbestos in aging residential and commercial buildings – neither of which was the case for this animal.
The authors noted that the area in which the horse lived also had a very high incidence rate of mesothelioma in humans and noted that other horses should be monitored for the potential presence of the disease and its biological indicators.
“Our study has led us to hypothesise that horses, in the geographical area, could be considered excellent sentinel animals,” the authors wrote, including for air pollutants and asbestos.