Myocarditis in naturally infected pets with the British variant of COVID-19

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Myocarditis in naturally infected pets with the British variant of COVID-19

Ferasin, L. et al. (2021) Infection with SARS-CoV-2 variant B.1.1.7 detected in a group of dogs and cats with suspected myocarditisVeterinary Record, 189 (9), p. e944

This paper reports on a series of dogs and cats presenting with myocarditis at a single referral centre, on the outskirts of London, between December 2020 and February 2021. The authors reported the incidence of myocarditis at their practice of 12.8% (8.5% in cats and 4.3% in dogs) compared with an expected incidence of 1.4%.

The animals presented with acute onset of lethargy, inappetence, tachypnoea /dyspnoea (secondary to congestive heart failure) and in some cases syncope. None of these patients had a previous history of heart disease and none developed symptoms of respiratory tract infection.

Diagnostic investigations revealed the presence of elevated cardiac troponin-I (median 6.8; range 0.68 to 61.1 ng/mL [normal reference range 0.0-0.2 ng/mL]) accompanied by echocardiographic evidence of myocardial remodeling and/or signs of pleural effusion and/or pulmonary edema, often confirmed on thoracic radiographs and/or severe ventricular arrhythmias on electrocardiography.

All affected animals were reported to have made a remarkable improvement with cage rest, oxygen therapy, acute diuresis and, in some cases, anti-arrhythmic therapy with sotalol and fish oil supplementation before being discharged on oral medications after a few days of intensive care. However, one cat represented one week after discharge with a relapse of her clinical signs, characterised by profound lethargy and uncontrolled ventricular tachycardia, prompting her owners to elect for euthanasia.

As these cases coincided with an outbreak of the B1.1.17 variant of SARS-CoV-2 in the UK, and many of the owners had tested PCR positive for SARS-CoV-2 infection in the 3-6 weeks before their animals became ill, the authors decided to investigate SARS-CoV-2 infection in these animals.

Serum samples as well as oro/nasopharyngeal and rectal swabs were collected from seven animals (six cats and one dog) at initial presentation and blood samples from four other pets (two cats and two dogs) during their recovery, 2-6 weeks after they developed signs of myocarditis.

Samples were frozen and sent to France for serological and virological investigation. All oro/nasopharyngeal swabs were negative for SARS-CoV-2 on PCR. However, the authors report low viral loads were detected from the rectal swabs from three of seven animals (two cats and one dog), and analysis of regions of the spike protein gene indicated the B.1.1.7 variant. One animal sampled during the acute phase of the disease (which tested PCR negative) and two of four animals sampled during the recovery period, were found to have SARS-CoV-2 antibodies.

While these results indicate that 6 of the 11 animals tested had some evidence of exposure to SARS-CoV-2 further research will be needed to investigate whether there is a causal link to myocarditis in pets and whether new variants of SARS-CoV-2 have a higher transmissibility or pathogenicity in animals.

This study is a pre-print, made available by bioRxiv, as such it is only a preliminary report and has not yet been peer-reviewed.


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