As interest and awareness continues to grow, the Texas A&M Veterinary Medical Diagnostic Laboratory, TVMDL, is reminding veterinary practitioners and animal owners about the available testing options for Chagas disease.
Chagas disease, spread by a family of insects known as “kissing bugs”, is a zoonotic disease caused by infection with the protozoan parasite Trypanosoma cruzi. A recent report from the Centers for Disease Control and Prevention, CDC, suggests Chagas disease is becoming endemic across the United States.
Kissing bugs are blood-feeding insects within the Reduviidae family. After feeding on an infected animal, kissing bugs harbor the T. cruzi parasite in their digestive tracts. Definitive hosts, such as humans and dogs, are infected through exposure to the kissing bug’s feces. After biting, the kissing bug will deposit feces into the wound, thus transmitting T. cruzi.
Clinical signs of Chagas disease
Once infected, dogs may remain asymptomatic for months or years before noticeable clinical signs appear, while some dogs never develop clinical signs. Of the dogs that do develop signs, there are acute and chronic phases of the disease.
Most clinical signs are similar to that of heart disease. Less severe signs include lethargy, depression, and a lack of appetite, whereas more severe signs include difficulty breathing and sudden death.
Antibody testing for Chagas disease
TVMDL tests for Chagas disease using a serologic assay called an indirect fluorescent antibody, IFA, test that detects T. cruzi antibodies.
The IFA test is performed on a glass microscope slide separated into multiple sections, or wells. Each well contains killed T. cruzi organisms. After a dog’s serum is diluted, it’s added to its own well and the entire slide is incubated. This process allows any antibodies against T. cruzi present in the serum to bind to the parasites on the slide. After the initial incubation period, a secondary fluorescent antibody is added, and the slide is incubated again. This second round of incubation “tags” any of the dog’s antibodies left on the slide.
Following the second round of incubation, the slide is viewed under a fluorescent microscope. Wells that contain antibodies against T. cruzi will have organisms that glow bright green. After evaluation, the positive samples are further diluted and tested to determine the levels of T. cruzi antibodies present (i.e. a titer).
TVMDL recommends dog owners interested in testing for Chagas disease first consult their veterinarian to rule out other potential diagnoses.
Scientists at Texas A&M University offer identification for suspected kissing bugs. Clients interested in identification services should visit kissingbug.tamu.edu or email kissingbug@cvm.tamu.edu.
For more information on serologic testing at TVMDL, visit tvmdl.tamu.edu or call the College Station laboratory at 979.845.3414.
