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Positive clinical outcome… 2024 JVIM article

Title: Positive clinical outcome using a modified dosing regimen of benznidazole in dogs at high risk for infection or acutely infected with Trypanosoma cruzi

Authors: Sukjung Lim, Stephanie Collins, Sarah A. Hamer, Rick L. Tarleton, and Ashley B. Saunders

Journal/Date of Publication: Journal of Veterinary Internal Medicine, 2024

DOI: 10.1111/jvim.17028

Objective: The study focuses on the prevention and management of Trypanosoma cruzi (Chagas disease) infection in dogs, particularly the effects of a modified benznidazole regimen.

Type of Study: Prospective

Conclusions:

  1. Prophylactic benznidazole prevented T. cruzi infection and cardiac disease in two dogs monitored over a 2-year period.
  2. One dog without prophylaxis died from acute Chagas-related myocarditis, while another developed severe arrhythmias but showed improvement with higher-dose benznidazole treatment.
  3. Though the sample size was small, these findings suggest potential clinical benefits from prophylactic and early benznidazole use, reducing morbidity from cardiac damage.

Clinical application:

  1. Prophylactic BNZ: Modified dosing of benznidazole may prevent T. cruzi infection in some high-risk dogs.
  2. Early treatment benefit: Higher benznidazole doses (17.5 mg/kg, twice weekly) in acutely infected dogs reduced cardiac biomarker (cardiac troponin I) concentrations and arrhythmias, even without total parasitological cure.
  3. Cardiac troponin I as a marker: Monitoring levels can help track cardiac damage and recovery during treatment.
  4. Prevention in endemic areas: Some dogs in areas with high vector exposure may benefit from prophylactic treatment during peak transmission seasons.
  5. Potential for reduced mortality: Early intervention with benznidazole could reduce sudden death risk from Chagas disease in dogs.
  6. No major adverse effects: Modified benznidazole dosing was well-tolerated in these dogs, with no reported adverse effects.
scatter plot of results from study as described in caption
Figure 1.
Serum cardiac troponin I results for the 4 dogs. Dogs 1 and 2 were in the prophylaxis group, dog 3 was in the nonprophylaxis group with death after visit 2 and dog 4 was in the nonprophylaxis group and subsequently started on a modified treatment dose regimen of benznidazole. The upper limit of the reference range (0.128 ng/mL) is represented by the dotted line.

Antiparasitic treatment… 2022 JVIM article

Title: Antiparasitic treatment with itraconazole and amiodarone in 2 dogs with severe, symptomatic Chagas cardiomyopathy

Authors: Elizabeth L. Malcolm, Ashley B. Saunders, Jordan P. Vitt, Bruno G. Boutet, and Sarah A. Hamer

Journal/Date of Publication: Journal of Veterinary Internal Medicine, 2022

DOI: 10.1111/jvim.16422

Objective: To describe 2 dogs with severe, symptomatic Chagas cardiomyopathy characterized by myocardial dysfunction and electrocardiographic abnormalities that were managed with a combination of cardiac medications and antiparasitic treatment with itraconazole and amiodarone.

Type of Study: Case Report

Conclusions:

  1. The combination of itraconazole and amiodarone was used to manage symptoms of Chagas cardiomyopathy.
  2. Both dogs died suddenly within six months, highlighting the challenges in treating advanced Chagas disease and the need for more effective antiparasitic protocols.

Clinical Application

  1. Combination therapy with itraconazole and amiodarone can be considered for managing symptomatic Chagas cardiomyopathy, though close monitoring is essential due to potential adverse effects.
  2. Early detection and treatment of T. cruzi infection are critical as advanced cases have poor prognosis.
  3. Awareness of antiparasitic treatment limitations emphasizes the importance of preventive measures against Chagas disease in endemic areas.
four-panel figure of transthoracic echocardiographic images of the 2 dogs in the study as described in the caption
Figure 1. Transthoracic echocardiographic images documenting dilatation of the right ventricle (RV) in both dogs with chronic Chagas cardiomyopathy. Case 1 includes images obtained in right parasternal short axis (A) and long axis (B) views to show very severe right atrial and ventricular enlargement compared to the left heart. Case 2 includes images obtained from right parasternal short axis (C) and left apical long axis (D) views to show moderate to severe right ventricular enlargement. LA, left atrium; LV, left ventricle; RA, right atrium

Cardiac diagnostic… 2021 JVIM article

Title: Cardiac diagnostic test results and outcomes in 44 dogs naturally infected with Trypanosoma cruzi

Authors: Derek J. Matthews, Ashley B. Saunders, Alyssa C. Meyers, Sonya G. Gordon, and Sarah A. Hamer

Journal/Date of Publication: Journal of Veterinary Internal Medicine, 2021

DOI: 10.1111/jvim.16166 

Objective: To describe the cardiac diagnostic test results and outcomes of dogs naturally infected with T. cruzi.

Type of Study: Retrospective

Conclusions:

  1. ECG abnormalities were detected in 95% of the dogs, with ventricular arrhythmias (65%) and atrioventricular block (AVB, 33%) being common.
  2. Echocardiographic findings included right ventricular (RV) enlargement in 35% of dogs and left atrial enlargement in 29-49% depending on how measurements were obtained.
  3. Elevated cardiac troponin I (cTnI) concentrations were observed in 56% of dogs, indicating myocardial damage.
  4. Risk factors for cardiac-related death: RV enlargement, AVB, and high ventricular arrhythmia scores (modified Lown score ≥2) were associated with shorter survival times.

Clinical Application:

  1. ECG monitoring is critical for identifying arrhythmias and conduction abnormalities in T. cruzi-positive dogs.
  2. Ventricular arrhythmias (modified Lown score ≥2) and RV enlargement are strong indicators of poorer prognosis.
  3. Ambulatory ECG (Holter) can detect more severe arrhythmias missed by standard ECG.
  4. cTnI measurement can help assess myocardial damage, with high concentrations associated with heart damage.
  5. Echocardiography, particularly focusing on RV enlargement, provides prognostic information.
  6. Early identification of conduction abnormalities, such as AV blocks, provides evidence of infection.
  7. Close follow-up and comprehensive cardiac diagnostics (including ECG, echocardiography, cTnI) are useful tests when managing dogs with Chagas disease.
three-panel figure showing survival probability of dogs in study as described in caption
Figure 1. Kaplan-Meier survival curves for dogs seropositive for Trypanosoma cruzi. Each cross represents when a dog was censored and days are measured from first exam at a veterinary medical teaching hospital. Variables measured include, A, presence or absence of AV block, B, ventricular arrhythmias with modified Lown score (MLS) categorized as <2 or ≥2, and C, presence or absence of right ventricular (RV) enlargement. Only significant variables are shown.

Risk factors… 2019 JVIM article

Title: Risk factors and select cardiac characteristics in dogs naturally infected with Trypanosoma cruzi presenting to a teaching hospital in Texas

Authors: Alyssa C. Meyers, Sarah A. Hamer, Derek Matthews, Sonya G. Gordon, and Ashley B. Saunders

Journal/Date of Publication: Journal of Veterinary Internal Medicine, 2019

DOI: 10.1111/jvim.15516

Objective: To report epidemiologic and select cardiac characteristics associated with T. cruzi infection in dogs presenting to a teaching hospital in Texas.

Type of Study: Retrospective

Conclusions:

  1. Infected dogs were generally younger and more likely to have ventricular arrhythmias and ECG abnormalities.
  2. Dogs with infected housemates had a significantly higher risk of infection.
  3. Increased awareness and consideration of T. cruzi testing are needed for dogs presenting with cardiac issues in endemic areas.

Clinical Application:

  1. Awareness: Clinicians in endemic areas should consider Chagas disease when diagnosing cardiac conditions in dogs.
  2. Testing: Testing is crucial for dogs with unexplained ventricular arrhythmias or those with infected littermates.
  3. Risk factors: Younger dogs and those with infected housemates are at higher risk and should be tested proactively.
  4. Management: While treatment remains challenging, identifying Chagas disease can aid in managing cardiac symptoms and providing a prognosis.
  5. Further Evaluation: Dogs with multiple ECG abnormalities, particularly including ventricular arrhythmias, should be assessed for Chagas disease especially when there are other historical or clinical findings consistent with T. cruzi infection.
  6. Differential Diagnosis: T. cruzi infection can mimic other cardiac diseases, underscoring the need for differential diagnosis in breeds predisposed to arrhythmogenic right ventricular cardiomyopathy (example: boxers, bulldogs), dilated cardiomyopathy (example: doberman pinscher), and tricuspid valve dysplasia (example: retrievers).
map of Texas showing T. cruzi infection prevalence of dogs in study in each of the state's ecoregions as described in the caption
Figure 1. Distribution of Trypanosoma cruzi infection across Texas ecoregions in 375 dogs presenting to Texas A&M University’s Small Animal Veterinary Medical Teaching Hospital between 2010 and 2016 that received T. cruzi serology testing or had T. cruzi histological findings. Twelve dogs resided outside Texas, and percent positive are depicted by a pie chart. Circles are proportional to the number of dogs sampled per ecoregion. Map was created using ArcGIS and the base layer is from Gould Ecological Regions created by Texas Parks and Wildlife Department GIS laboratory, downloaded from http://aampo-mpo.opendata.arcgis.com/.