Feline coronavirus-associated myocarditis in a domestic longhair cat

Ernandes, Maria A; Cantoni, Anna M; Armando, Federico; Corradi, Attilio; Ressel, Lorenzo; Tamborini, Alice

FCoV is found worldwide and is over-represented in multi-cat households; it replicates in enterocytes. FCoV infection is usually asymptomatic; however, it can cause transient mild or occasionally severe acute or chronic vomiting and/or diarrhoea with weight loss that is unresponsive to supportive treatment. [2] [3] [4] If the cat's macro phages fail to eliminate the virus, it replicates within their cytoplasm and FIP develops. 2,3 FIP is a fatal, immune-mediated disease and is a common infectious cause of death in cats. 2, 3, 5, 6 The non-effusive form is characterised by the development of granulomatous lesions within the kidneys, central nervous system, eyes and parenchymatous organs (including the intestine, where ileocolic junction masses are common). 3, 7, 8 The hallmark of the effusive form is the vasculitis-induced fluid accumulation in body cavities (pleural, peritoneal and pericardial). 3, 9, 10 The clinical presentation described in our case report was compatible with what reported in literature. However, the onset of CHF was unexpected and initially considered unrelated to FIP. It is worth mentioning that, in cats with FIP, some unusual manifestations have been described, such as a mediastinal cystlike mass in the thorax, skin fragility syndrome and other skin lesions, orchitis or priapism, while no FCoVassociated myocarditis has been described yet. [11] [12] [13] [14] [15] [16] A definitive diagnosis of FIP is often challenging. A score system based on history, clinical signs, laboratory abnormalities and level of antibody titres has been suggested in order to assess the likelihood of FIP. 2,3 However, necropsy with histology and IHC are still considered the gold standards for the diagnosis of FIP. 2, 3, [17] [18] [19] [20] In the present case, necropsy revealed pyogranulomatous infiltration of multiple organs, including the myocardium. Furthermore, the multifocal vasculocentric pattern of the intestinal wall lesions would favour a monocyte-triggered spreading of the coronavirus to other organs (including the myocardium), as previously reported. 1 IHC performed on the myocardial tissue confirmed the presence of FCoV-positive macrophages. Given the absence of morphological signs consistent with HCM, the thickening of the myocardium was explained by the presence of oedema and inflammatory infiltrates composed of lymphocytes, plasma cells and FCoV-positive macrophages; therefore, a post-mortem diagnosis of FCoV-induced myocarditis, leading to the unusual representing picture (CHF), was made. To the authors' knowledge, this has never been reported before in the veterinary literature. Myocarditis is a form of myocardial disease characterised by the presence of inflammation in response to physical, chemical and infectious agents. Reports of dogs and cats with infectious myocarditis caused by systemic diseases, such as protozoa (Trypanosoma cruzi, Hepatozoon species, Leishmania species, Neospora caninum, Toxoplasma gondii), viruses (FIV, parvovirus, West Nile virus), bacteria (Bartonella species, Bacillus piliformis, Citrobacter koseri), spirochetes (Borrelia burgdorferi) and, in some cases, opportunistic fungi (Blastomyces species) [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] have been described. To date, as far as the authors are aware, there have been no reports of FCoV as the cause of myocarditis. Therefore, this cat represents the first published report that viruses other than parvovirus and FIV can ca