In a recent development on the Mediterranean island of Cyprus, renowned for its substantial feline population, a mysterious spike in cat deaths has been linked to a novel strain of feline coronavirus. The crisis, which garnered international attention, involved thousands of cats displaying symptoms such as fevers, swollen bellies, and lethargy, all indicative of feline infectious peritonitis (FIP), commonly caused by a specific type of cat coronavirus.
Researchers faced challenges in explaining the sudden surge in FIP cases. However, a recent study, published as a preprint on bioRxiv, suggests a potential breakthrough. Scientists have identified a new strain of feline coronavirus, labeled FCoV-23, that has incorporated crucial RNA sequences from a highly virulent dog pathogen known as pantropic canine coronavirus (pCCoV). This discovery could shed light on the widespread transmission and severity of illness observed among cats in Cyprus.
Gary Whittaker, a virologist at Cornell University College of Veterinary Medicine not involved in the study, praised the research, noting the significance of identifying a virus that presents both disease and high transmissibility.
The cat health crisis in Cyprus gained attention earlier this year, with reports of increased FIP cases. By July, media outlets reported nearly 300,000 cat deaths, a figure later revised by local veterinarians to around 8,000. To address the situation, the Cypriot government authorized the veterinary use of the human SARS-CoV-2 medication molnupiravir in August, showing promise in treating FIP.
Typically, feline coronaviruses infect the gut, causing mild infections that do not progress to FIP. However, FIPV, a more dangerous form of the virus that triggers serious disease, usually does not transmit between animals. The new strain, FCoV-23, appears to have arisen from the combination of a feline coronavirus encountering pCCoV in an unidentified host animal, coopting key RNA sequences and spike proteins.
Christine Tait-Burkard, a virologist at the University of Edinburgh’s Roslin Institute and study co-author, explained that FCoV-23’s unique genetic makeup might enable it to cause severe FIP while still infecting the intestines and spreading through feces. The spike protein changes could enhance stability outside an animal host, increasing the likelihood of transmission through contaminated feces.
Although FCoV-23 has been identified in one case in the United Kingdom, imported from Cyprus, the overall risk to cats outside the island is considered low. Researchers are collaborating with Cypriot counterparts to assess the prevalence and fatality rate of FCoV-23, improve diagnostic tools, and investigate its unique features, including a higher rate of neurological symptoms compared to typical FIP cases.
The discovery of this mixed cat-dog coronavirus underscores the importance of a comprehensive, cross-species approach to understanding viral evolution, emphasizing its potential contribution to broader coronavirus virology research.
