Feline Bocavirus (FBoV): An Emerging Pathogen at the Intersection of Respiratory and Enteric Feline Disease
1.Introduction
The feline infectious disease spectrum has been widened by the identification of a number of newly identified parvoviruses, of which Feline Bocavirus (FBoV) is arguably the most important. After its first identification by metagenomic sequencing, it has been classified into three distinct genotypes, namely, FBoV-1, FBoV-2, and FBoV-3 [1, 2].Bocaviruses are recognized for their capacity for causing diseases in a variety of mammalian species, including humans and dogs. In cats, it has been recognized as a possible aetiological agent of the Feline Respiratory Disease Complex (FRDC) and gastrointestinal diseases. However, the tendency for it to co-exist with other well-established viruses has led to a continuing debate about its true impact on feline health [1, 3].
2. Viral Characterization and Genotypic Diversity
Feline Bocavirus is a small, non-enveloped, single-stranded DNA virus. The viral genome is unique among parvoviruses by containing a second open reading frame (ORF) coding for the NP1 protein, which is thought to be involved in viral replication and immune evasion [2, 4].The three genotypes of Feline Bocavirus vary in their prevalence and clinical associations as follows:
•FBoV-1:
The most commonly identified of the three, commonly associated with hemorrhagic enteritis and respiratory disease [1, 5].
•FBoV-2 and FBoV-3:
The recently identified genotypes, for which the full clinical and geographical associations are being characterized [2, 3].
3. Clinical Manifestations and Pathogenesis
FBoV infection is known to manifest in two forms:
•Gastrointestinal Disease:
FBoV-1 was found to be linked with outbreaks of severe hemorrhagic enteritis (bloody diarrhea) in shelter environments [1, 6].
•Respiratory Disease:
FBoV was found in the respiratory mucosa and regional lymph nodes in cats infected with upper respiratory infection [1, 4].
Interestingly enough, recent studies have also found FBoV in the brains of cats with neurological deficits, implying that FBoV may have a wider range of infectivity than previously thought [7].
4. The Role of Co-infections
A significant feature of FBoV infection is that it tends to co-infect its host alongside other pathogens. FBoV is known to co-infect with Feline Parvovirus (FPV), Feline Coronavirus (FCoV), and Feline Calicivirus in many cases [1, 5].
•Synergistic Effects:
There is enough evidence to show that co-infection with FPV increases the severity of gastrointestinal infection in cats, resulting in more severe bloody diarrhea and increased mortality rates [6, 8].
•Diagnostic Confusion:
The presence of multiple pathogens in an infected cat confounds veterinarians in determining the actual causative agent of infection, resulting in FBoV not being included in diagnostic procedures in many cases [1, 9].
5. Research Gaps and Future Directions
There are significant research gaps that need to be addressed to facilitate the effective management of FBoV. These research gaps are:
•Primary Pathogenicity:
There is limited information on the capability of FBoV to cause severe diseases on its own or if it is an opportunistic pathogen that exacerbates existing diseases [1, 3].
•Standardized Diagnostics:
FBoV is not included in the majority of the routine "feline panels." There is an urgent need to have standardized, commercially available PCR assays for the detection of FBoV [9].
•Shedding and Persistence:
Recent studies have attempted to investigate the duration for which an infected cat can shed the virus. More research is needed to understand the dynamics of FBoV shedding in domestic settings [4].
•Vaccine Development:
There is no existing vaccine for FBoV. More research is needed on cross-protection between different genotypes, which will play an integral role in future vaccine development.
6.Conclusion
FBoV is an intricate emerging pathogen in feline medicine. The high prevalence, combined with the severity of associated diseases, especially when it is co-infecting with other pathogens, makes it an important pathogen to consider. By incorporating FBoV into routine diagnostics, it is possible to better understand its unique pathogenesis, thereby protecting domestic cats from the elusive, devastating effects of FBoV.
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