A rare case of mesothelioma, a form of cancer linked to asbestos exposure in humans and dogs, has been reported in an older horse in Italy.
The case of a 22-year-old Quarter Horse from the Lazio region is described in the September issue of the magazine. animated.
Mesothelioma develops in the mesothelium, the thin layer of tissue that covers many internal organs. The most common area affected is the lining of the lungs and chest wall. It can also affect the lining of the abdomen and, rarely, the sac around the heart.
In humans, more than 80% of cases are caused by exposure to asbestos, with higher levels of exposure creating a greater risk.
Mesotheliomas can affect different species, including dogs, cats, cattle, sheep, goats and horses.
Onset in horses is very rare, noted Giuseppe Passantino and his fellow researchers in their case report.
Since 1976, there have been approximately 11 reports of mesothelioma in horses, usually located in the pericardium, pleural cavity, or peritoneal cavity.
Most reported cases involved mares between 2 and 27 years of age, with a higher incidence in adults and older horses. There is no obvious race predisposition. In most cases of equine mesothelioma, the diagnosis is made after death, either at the slaughterhouse or during a necropsy.
The chestnut tree at the center of the case report was kept in a paddock and used in equestrian tourism activities. The owner said the horse had not suffered any major illness during its life.
The debilitated horse was taken to a veterinary clinic in Rome because of colic-like pain and sensory depression. His pulse was fast and his breathing increased. His mucous membranes were congested and his hematocrit was elevated. Bowel sounds were muted.
An abdominal ultrasound revealed excessive fluid accumulation and rounded abdominal masses adherent to the peritoneum.
Despite treatment for over five days, the horse’s condition worsened and the decision was made to euthanize him. A post-mortem examination two hours later revealed a large amount of fluid around the abdomen and chest.
Examination revealed numerous nodular masses on the peritoneum, omentum, lungs, heart, and mediastinum. They were up to 4 cm in size, diffuse, whitish and red, greasy in appearance and arranged in clusters.
A diagnosis of epithelioid mesothelioma was made by microscopic examination and confirmed by immunohistochemistry.
The authors hypothesized that the primary tumor most likely originated in the peritoneum and spread to local lymph nodes and the chest cavity. However, a multicentric origin of the tumor cannot be completely ruled out, they said.
The cause of mesothelioma in horses is unknown, they noted, while exposure to asbestos dust has been reported to induce its onset in humans and dogs. The cause of the cancer in the case report was most likely environmental in nature, they said.
In fact, the horse lived in an area with a very high incidence rate of human mesothelioma, the authors said. “Another case came from the same area, where both the horse and the owner were suffering from lymphoma.”
Because of the environmental origin of this form of cancer, it would be prudent to monitor other horses in the same area to assess for the presence of mesothelioma, they said. It would also be interesting to provide useful tools for an early diagnosis of the disease using diagnostic methods similar to those used in humans and to propose a cause of this cancer in horses which, to date, is still unknown.
The case reporting team was composed of Passantino, Antonella Tinelli and Nicola Zizzo, from the University of Bari Aldo Moro; Emilio Sassi and Ilaria Filippi, who are both independent researchers; and Valerio Serata, with Equine Practice SRL from Campagnano di Roma.
Passantino, G.; Sassi, E.; Filippi, I.; Serata, V.; Tinelli, A.; Zizzo, N. Thoracic and abdominal mesothelioma in an older horse from the Lazio region. Animals 2022, 12, 2560. https://doi.org/10.3390/ani12192560
The study, published under a Creative Commons licensecan be read Here.