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Fatal Chagas myocarditis… 2021 Veterinary Parasitology: Regional Studies and Reports article

Title: Fatal Chagas myocarditis in government working dogs in the southern United States: Cross-reactivity and differential diagnoses in five cases across six months

Authors: Alyssa C. Meyers, Erin E. Edwards, John P. Sanders, Ashley B. Saunders, and Sarah A. Hamer

Journal/Date of Publication: Veterinary Parasitology: Regional Studies and Reports, 2021

DOI: 10.1016/j.vprsr.2021.100545

Objective: A case series describing Chagas myocarditis in working dogs in the southern United States. 

Type of Study: Case series

Conclusions:

  1. Chagas myocarditis can be rapidly fatal in dogs, characterized by sudden death, elevated cardiac troponin I concentrations, and ECG abnormalities.
  2. Serological cross-reactivity with Leishmania spp. poses challenges in diagnosis, requiring multiple testing methods to confirm T. cruzi infection.
  3. Postmortem analysis showed severe myocarditis in all cases, though only one had histological evidence of amastigotes, while three tested positive for T. cruzi DNA with PCR.

Clinical Application:

  1. Diagnostic Approach: Use a combination of serology, PCR, and histopathology to increase diagnostic accuracy, particularly in endemic areas.
  2. Monitoring: Routine cTnI and ECG monitoring is recommended for seropositive dogs to detect early signs of myocarditis.
  3. Cross-Reactivity Considerations: In areas where both T. cruzi and Leishmania spp. are present, clinicians should be aware of cross-reactivity and confirm diagnoses with multiple testing modalities.
  4. Management of Infected Dogs: Despite infection, some dogs may continue to perform duties; however, sudden death highlights the need for heightened surveillance and potentially pre-emptive retirement in high-risk cases.
  5. Public Health Implications: Awareness of Chagas disease in working dog populations can be indicative of broader public health risks due to vector exposure.
AI generated rendering of T. cruzi parasite in blood
Trypanosoma cruzi parasite in blood (Generated with Adobe Stock AI)

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.