Chagas disease confirmed in American horse by researchers


stock-eyeA horse was euthanized in Texas as a result of Chagas disease, researchers from Texas A&M University have reported.

Chagas disease is a protozoal infection found in people and dogs in Central and South America. It is caused by Trypanosoma cruzi.

The 10-year-old Quarter Horse gelding was taken to the Texas A&M University Veterinary Teaching Hospital with a six month-history of unsteadiness on its feet and hind-limb lameness.

Laura Bryan and her colleagues, in a short communication in the journal Veterinary Parasitology, said the horse was treated presumptively for equine protozoal myeloencephalitis – inflammation of the spinal cord and brain – based on clinical signs.

The horse was ultimately euthanized after its condition worsened. Microscopic examination revealed evidence of T. cruzi in the thoracic spinal cord. DNA testing of spinal cord tissue was subsequently positive for T. cruzi.

The researchers said while canine Chagas disease cases have been widely reported in dogs in southern Texas, this was the first report of clinical T. cruzi infection in an equid with demonstrable amastigotes – cells from a certain phase in the life-cycle of trypanosome protozoans – in the spinal cord.

“In contrast to previous instances of Chagas disease in the central nervous system of dogs and humans, no inflammation or T. cruzi amastigotes were detected in the heart of the horse.”

They reported that, based on clinical signs, there was a potential for misdiagnosis of Chagas disease with other infectious diseases that affected the equine central nervous system.

T. cruzi should be considered as a possible cause of neurologic problems in horses associated with brain and spinal cord inflammation in areas where Chagas disease was present, they said.

The prevalence of T. cruzi in horses and the role of equids in the parasite life cycle required further study, they said.

Chagas disease is spread mostly by insects known as Triatominae, or kissing bugs.

Early stage symptoms in people are usually either not present or mild, and may include fever, swollen lymph nodes, headaches, or local swelling around the bite.

After 8–12 weeks individuals enter the chronic phase and two-thirds of people never have further symptoms. The rest develop further symptoms 10 to 30 years later, which can include enlargement of the heart ventricles leading to heart failure, an enlarged esophagus or an enlarged colon.

Chagas disease in a Texan horse with neurologic deficits.
Bryan LK, Hamer SA, Shaw S, Curtis-Robles R, Auckland LD, Hodo CL, Chaffin K, Rech RR.
Vet Parasitol. 2016 Jan 30; 216:1 3-7. doi: 10.1016/j.vetpar.2015.11.016

The abstract can be read here


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