This article provides a clinical overview and expert analysis of a severe Feline Panleukopenia Virus (FPV) outbreak at an animal shelter in October 2024. It details the diagnostic process, the role of co-infections, and the critical importance of biosecurity in high-density populations.
A shelter faced a significant mortality event, ultimately resulting in the death of approximately 60 felines. The attending veterinarian noted a peracute clinical presentation that was atypical for "classic" parvovirus infections, with death often occurring within 24 hours of minimal signs, such as a single vomiting episode. The high mortality rate, which included vaccinated adult cats, prompted an in-depth investigation in collaboration with Professor Hans Nauwynck of Ghent University and PathoSense to determine the cause.
A post-mortem intestinal swab from a deceased cat was submitted for PathoSense Diagnostics analysis. The report identified a strong viral and bacterial enteric disease complex, as shown in the figure below.
The primary finding was a High level of Feline panleukopenia virus, also know as feline parvovirus. However, the outbreak also involved heavy co-infections with other relevant viral infections such as Feline calicivirus, Feline coronavirus, and Kobuvirus. Feline calicivirus can contribute to systemic clinical signs, whereas feline coronavirus and kobuvirus has a tropism for the intestine. Moreover, bacterial infections also contributed to the complex. Findings included moderate levels of Collinsella intestinalis, Escherichia sp., Helicobacter sp., and Mycoplasmopsis arginini.
Following the initial diagnosis, a complete genomic sequence of the FPV strain was generated. The analysis revealed that this was not a new or novel strain, but a known FPV lineage already in circulation within Belgium and Europe. As such, this strain should be covered by the current vaccines. The investigation concluded that the extreme virulence observed was not due to an unusually pathogenic FPV strain, but rather a multifactorial problem typical of a high-density shelter environment.
Shelter-Specific Issue: The outbreak was defined as a "shelter-related problem". The lack of similar reports from private practitioners indicated that this was not a widespread problem in the field.
High Infection Pressure: The primary driver was identified as escalating infection pressure within the shelter.
The Role of Co-Infections: The complex of viral and bacterial co-pathogens, as identified by the PathoSense report, was critical. Co-infections can induce blastogenesis, a state of lymphocyte activation and proliferation, which enhances FPV replication. This is because the virus requires mitotic active cells for its replication. As such, co-infections exacerbate clinical disease severity.
The "Immunity Gap": Vaccination at high viral exposure is often ineffective. If an animal is exposed to the wild-type virus within a week of vaccination, before robust immunity has developed, the wild-type virus is likely to cause a breakthrough infection.
Biosecurity and Foster Homes: The deaths occurring in foster homes were attributed to kittens being exposed to pathogens within the shelter's contaminated zones before or during their transfer. This highlights a breakdown in biosecurity protocols, with potential for transmission via personnel or fomites.
Recommendations focused on interrupting the infection cycle through stringent management protocols, as the existing FPV strain is covered by current vaccines under normal exposure conditions.
Decontamination: Implementing rigorous cleaning and disinfection protocols. Highly effective are alkaline detergents followed by a potent disinfectant like a glutaraldehyde-based product or bleach, depending on the surface type.
Quarantine and Biosecurity: Effective control is only possible if newly admitted animals are placed in strict quarantine. There must be no crossover of personnel or materials between quarantine/sick zones and the general population. Animals should ideally move directly to foster homes without passing through contaminated shelter areas.
Supportive and Targeted Therapeutics: For affected animals, supportive care is crucial. The presence of bacterial co-infections, such as Mycoplasma, suggests that targeted antibiotic therapy (e.g., doxycycline) could be beneficial, as these bacteria do not respond to cephalosporins.
This case is a crucial reminder that severe FPV outbreaks in shelter settings are often driven by a "perfect storm" of high infection pressure and pathogenic co-infections, rather than the emergence of novel "super-strains." For companion animal veterinarians, particularly those working with shelters, the key takeaways are:
The clinical severity of FPV is significantly amplified by viral and bacterial co-pathogens.
Comprehensive diagnostics that identify the complete disease complex are invaluable for understanding the full picture of an outbreak.
Vaccination alone cannot control FPV in the face of overwhelming infection pressure and biosecurity failures.
Uncompromising implementation of quarantine, cohort management, and decontamination protocols is non-negotiable in high-density animal environments.
In our miniguide for veterinarians, we address the challenges in traditional diagnostics, introduce the PathoSense Dx method using nanopore sequencing in more detail, and outline the importance of high-quality sample collection. The guide further describes several interesting uses cases collected by veterinarians active in different animal species (pigs, cattle, poultry, cats, exotics...). Looking forward to get inspired? Don't hesitate.