Terminology

The following is terminology often used in discussions of canine Chagas disease.

• Acute phase: The initial stage of an infection, often characterized by rapid onset of symptoms.
• Amastigote: The intracellular, non-motile, replicating stage of T. cruzi found within infected cells in the mammalian host. Amastigotes may commonly occur in the heart tissue cells of infected animals.
• American trypanosomiasis: Another name for Chagas disease (which differentiates it from African trypanosomiasis, caused by a related parasite).
• Amiodarone/Itraconazole protocol: This protocol is described in the literature and anecdotally as an antiprotozoal treatment administered over a one-year period. Potential benefits include amiodarone’s primary use as an antiarrhythmic. Potential challenges include the prolonged treatment period, lack of a reliable test for a cure, and medication side effects, which can include liver damage, vomiting, diarrhea, inappetence, and worsening arrhythmias. 
• Arrhythmia: When heartbeats are abnormal, occurring at an irregular pattern or at rates that are too fast or too slow.
• Arrhythmogenic right ventricular cardiomyopathy (ARVC): A form of heart disease characterized by fibrofatty replacement of the heart muscle, most often resulting in ventricular arrhythmias with a subset that also develops heart enlargement and ventricular myocardial dysfunction. The right side of the heart is generally affected more severely than the left side.
• Benznidazole: An antiparasitic drug used to treat Chagas disease in humans and animals. The newer, modified protocol in dogs utilizes a higher dose administered multiple times a week (2-3) over a 6-month period.
• Chronic phase: The long-term stage of an infection, which can last for months to years. It can be associated both without (indeterminate) and with symptoms. Many infected dogs may be in the chronic phase for many years.
• Cardiac biomarkers: A substance from the heart that is released into the bloodstream in response to stress or damage and can be detected with blood tests. An example is cardiac troponin I.
• Cardiac troponin I (cTnI): A cardiac biomarker released when there is damage to the heart cells. Elevated concentrations do not indicate a specific disease but can be associated with myocarditis and very high concentrations can be an indicator of a shorter survival time (poor prognostic indicator). The cTnI concentrations are sometimes (but not always) elevated in dogs infected with T. cruzi.
• Chagas cardiomyopathy: A serious heart condition that results from damage to the heart muscle that manifests as arrhythmias, a weak heart, heart failure and sudden death.
• Congestive heart failure: A condition that develops when the heart cannot efficiently pump blood through the body and it leaks into or around the lungs (pulmonary edema or pleural effusion, respectively), into the sac around the heart (pericardial effusion), or into the abdomen (ascites or peritoneal effusion). 
• DCM (dilated cardiomyopathy): A type of heart disease characterized by enlargement and weakening of the heart chambers. Causes of DCM include genetic (heritable in some breeds like Doberman Pinschers), nutritional deficiencies (diets high in peas/legumes/lentils or low taurine levels), drugs (doxorubicin toxicity), and infectious diseases (parvovirus).   
• Discordant results: When different diagnostic tests for the same condition produce conflicting results.
• Discrete typing units (DTUs): This describes the different genetic strains of a microbial pathogen (i.e., T. cruzi) to further characterize them by their genetic sequences.
• ECG (electrocardiogram): A test that records the electrical activity of the heart. Sometimes called EKG. Often run in clinics for a short time (30 seconds to 6 minutes)
• Echocardiogram: A test that uses ultrasound to evaluate heart size and function.
• ELISA (enzyme-linked immunosorbent assay): A widely used type of serological test that detects antibodies or antigens. The results are quantitative.
• Endpoint titer: The reciprocal of the highest level of serum dilution at which a positive serologic test result is obtained. The higher the endpoint titer, the stronger the antibody response. The clinical significance of the endpoint titer is not well known, and low endpoint titers may reflect background activity.
• Holter monitor: A wearable device that records heart rate and rhythm over an extended period of time (typically 24 or 48 hours).
• IFA test (indirect fluorescent antibody): A type of serological test that uses fluorescent dyes to detect antibodies. Results are reported as the endpoint titer.
• Lateral flow assay: A simple, rapid type of serological test, often used as a point-of-care test. While some lateral flow assays are validated for human use, no such tool is approved for veterinary use, although they may be useful for research purposes.
• Myocarditis: Inflammation of the heart muscle. 
• Parasitological diagnosis: Directly detecting the parasite in blood or tissue samples.
• PCR (polymerase chain reaction) Test: A laboratory technique used to amplify specific DNA sequences, including those of T. cruzi, to detect the parasite’s presence. Blood from infected animals may not always test PCR-positive, as there is variation in the level of circulating parasite in the blood and variation in the sensitivity of different PCR protocols; standard PCR of blood alone may not be an adequate test to show infection or cure of animals.
• Serological diagnosis: Detecting antibodies against the parasite in blood samples.
• Transplacental transmission: Spread of a disease from the mother to her babies while they are in the uterus. This is a form of vertical or congenital transmission.
• Transmammary transmission: Spread of a disease through the mother’s milk to her babies. This is a form of vertical transmission.
• Triatomine bug: A type of blood-sucking insect, also known as the “kissing bug,” that transmits T. cruzi.
• Tricuspid valve dysplasia: A congenital heart defect (present at birth) in which the valve leaflets are abnormal, resulting in leaking of the valve and secondary enlargement of the right atrium and ventricle. It can be mistaken for Chagas disease in severely affected young dogs.
• Trypanosoma cruzi (T. cruzi): The protozoan parasite that causes Chagas disease.
• Vector: An arthropod (insect or tick) that transmits a disease-causing agent from one animal to another.

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