Prevalence of different types of arrhythmias in canine babesiosis and ehrlichiosis

Introduction

Tick-borne haemoparasitic diseases (TBDs) such as babesiosis and ehrlichiosis are widely prevalent among dogs in India and are frequently associated with multisystemic complications including anaemia, thrombocytopenia and systemic inflammation. Cardiac involvement is an important but often underestimated consequence of these infections, with arrhythmias being a common manifestation of myocardial hypoxia, inflammatory injury and electrolyte disturbances. Limited information exists on arrhythmias associated with naturally occurring TBDs in the Himalayan region. Thus, the present investigation was undertaken to determine the prevalence and pattern of arrhythmias in dogs infected with Babesia gibsoni and Ehrlichia canis.

Materials and Methods

A total of 2,755 dogs presented to the Department of Veterinary Medicine, COVAS, Palampur, from April 2024 to August 2025 were screened. Giemsa-stained blood smears were examined for haemoparasites. Positive animals underwent haematobiochemical evaluation and electrocardiography. Standard six-lead ECGs were recorded in right lateral recumbency. Data were analysed based on age, sex, month-wise occurrence and type of arrhythmia. Prevalence percentages were calculated following standard procedures.

Results and Discussion

Of the 2,755 dogs examined, 465 (16.87%) were positive for haemoparasites (Table 1). Babesia gibsoni (68.81%) was the most prevalent organism, followed by Ehrlichia canis (27.09%), while Babesia canis, Hepatozoon canis and mixed infections were less frequent (Table 2). These observations concur with earlier findings indicating the predominance of B. gibsoni in northern India (Chaudhuri et al., 2017) [2] . 3). Similar demographic trends have been reported previously (Chisu et al., 2024) [3] . 4). Babesiosis accounted for 53.70% of these cardiac cases, followed by ehrlichiosis (32.40%) and mixed infections (12.03%).

Comparable myocardial involvement in TBDs has been reported by Chaudhuri et al., (2017) [2] and Diniz et al., (2008) [4] . Breed distribution indicated the highest involvement in Mongrels, followed by Labradors and German Shepherds (Table 5). This likely reflects greater exposure to outdoor environments. Twenty-nine arrhythmic patterns were identified (Table 6).

The most common abnormalities included tachycardia (44.4%), sinus arrhythmia (23.1%), low-voltage QRS complexes (20.3%), QRS notching (19.4%), atrial standstill (16.6%) and ST-segment deviations (14.8%-17.6%). These changes may be attributed to anaemia-induced hypoxia, metabolic derangements and inflammatory myocardial injury (Lobetti, 2005) [7] . [5,1] . Atrial standstill, a severe conduction disturbance, suggests significant electrolyte imbalance or myocardial degeneration, which aligns with earlier findings (Diniz et al., 2008) [4] . Overall, the arrhythmias recorded in this study reflect the multifactorial cardiac pathogenesis of TBDs, involving hypoxia, oxidative stress and myocarditis, as supported by Lobetti et al., (2002) [6] .

Conclusion

The present study conclusively demonstrates that tick-borne haemoparasitic infections, particularly babesiosis and ehrlichiosis, are associated with a substantial burden of cardiac involvement in dogs. Babesia gibsoni emerged as the predominant pathogen, reflecting its endemic significance in the study region, with infections showing clear seasonal, age-and sex-related trends. Nearly onefourth of haemoparasite-positive dogs exhibited electrocardiographic abnormalities, confirming that myocardial dysfunction is a frequent and clinically relevant complication of these diseases. A wide spectrum of arrhythmias was documented, with tachycardia, sinus arrhythmia, low-voltage QRS complexes, QRS notching and ST-segment deviations being the most prevalent. These electrocardiographic alterations indicate underlying myocardial hypoxia, inflammatory injury, oxidative stress and conduction disturbances secondary to anaemia and systemic illness. The occurrence of severe abnormalities such as atrial standstill, atrial fibrillation and ventricular arrhythmias further emphasizes the potential for life-threatening cardiac complications in affected dogs. Overall, the findings highlight the importance of incorporating routine electrocardiographic evaluation into the diagnostic and monitoring protocols for dogs with tickborne diseases. Early recognition of cardiac involvement can facilitate timely therapeutic interventions, improve clinical management and potentially reduce morbidity and mortality. This study adds valuable regional data to the existing literature and underscores the need for heightened clinical vigilance regarding cardiovascular complications in canine tick-borne haemoparasitic infections.

Acknowledgement

AcknowledgementThe authors thank the Department of Veterinary Medicine, COVAS, CSKHPKV, Palampur, for providing necessary facilities.

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