Chagas disease, a protozoal infection mainly affecting people and dogs in Mexico, South America and Central America, has been detected in a horse in Texas. Although canine cases of Chagas disease had previously been reported in southern Texas, this is the first known case of clinical infection in an American horse.
Caused by the organism Trypanosoma cruzi and spread by the feces of insects commonly called “kissing bugs,” Chagas disease may initially produce an array of vague signs, including headache, fatigue and swollen lymph nodes. After the acute stage of infection, the disease enters a chronic phase. Months, years or even decades after the initial infection, about 20 percent of humans and dogs with chronic Chagas disease develop digestive problems, neurological impairment or heart failure.
In the Texas Chagas case, the 10-year-old Quarter Horse had weakness and lameness in his hind limbs for six months. He had been treated for equine0 protozoal myeloencephalitis (EPM) before being referred to the Texas A&M University Large Animal Hospital. When his condition deteriorated, he was euthanatized and a necropsy revealed evidence of T. cruzi in his spinal cord. Genetic testing confirmed the identification, while other tissue tests ruled out other possible causes of neurological deficits, including EPM. No evidence of the parasite was found in the horse’s heart.
The researchers concluded that the horse had contracted Chagas disease, making this the first equine case of the condition to have been confirmed with pathological evidence. They say that Chagas disease “should be considered as a differential diagnosis in horses with neurologic clinical signs and histologic evidence of meningomyelitis that originate in areas where Chagas disease is present.” They also call for further study of the prevalence and life cycle of T. cruzi in horses.
Reference: “Chagas disease in a Texan horse with neurologic deficits,” VeterinaryParasitology, January 2016
This article first appeared in EQUUS issue #463, April 2016.