BackgroundMyocarditis and myocardial injury associated with feline infectious peritonitis (FIP) recently are being recognized.Hypothesis/ObjectivesProspectively document the frequency of cardiac changes in cats with FIP using echocardiography and cardiac troponin I (cTnI) concentrations.AnimalsTwenty cats with naturally occurring FIP without previous history of heart disease.MethodsCats diagnosed with FIP were tested for common concurrent infections associated with myocarditis by testing serum for feline immunodeficiency virus (FIV) antibodies, feline leukemia virus antigen (FeLV), Dirofilaria immitis antigen, Bartonella spp. immunoglobulin G (IgG), and Toxoplasma gondii IgG and immunoglobulin M (IgM) as well as by testing blood for nucleic acids of Bartonella spp. and coronavirus (SARS-COV-2). Each cat also was tested for serum cTn1 concentration and underwent an echocardiographic examination. After 12 weeks of treatment with antiviral drugs, serum cTnI concentrations were reassessed.ResultsAll echocardiographic measurements were normalized to patient body weight. The left ventricular posterior wall from right parasternal long axis and short axis was thickened in 55% (11/20) and 25% (5/20) of cats, respectively. Pleural effusion was present in 40% (8/20) of cats and pericardial effusion in 25% (5/20) of cats, but a cardiac cause was not identified for these effusions. Median cTnI at initial evaluation was 0.37 ng/ml (interquartile range [IQR], 0.20-0.83; upper reference interval, 0.20 ng/ml). Repeat cTnI was performed after 12 weeks of antiviral treatment in 6 cats that initially had increased cTnI (median initial cTnI, 0.75 ng/mL) and, in all 6 cats, cTnI normalized to < 0.20 ng/mL.Conclusions and clinical importanceCats with FIP can present with increases in cTnI and ventricular wall thickening, findings suggestive of myocarditis or myocardial injury.

Domestic cat hepatitis B virus (DCHBV) is a member of the Hepadnaviridae family and has been associated with hepatocellular carcinoma (HCC) in cats. This study aimed to determine the prevalence of DCHBV and associations with feline immunodeficiency virus (FIV), feline leukaemia virus (FeLV) and feline coronavirus (FCoV) infections in cats in Serbia, and to characterise the detected DCHBV genomes. Whole blood, serum and liver samples from 308 animals were screened by real-time (RT-)PCR for DCHBV, FIV, FeLV, and FCoV. The prevalence of DCHBV was 2.60%, with no significant associations observed between DCHBV infection and age, sex, or coinfection status. Three whole genome sequences were obtained, and phylogenetic analysis demonstrated that the Serbian strains belong to genotype A. Molecular analysis revealed three unique nonsynonymous substitutions in the S ORF. Within the C ORF, a 28-amino acid N-terminal precore region with conserved cysteine residues critical for protein maturation was identified, along with the C-terminal arginine-rich domain. A putative core promoter region was detected, containing two motifs analogous to the pgRNA and pcRNA initiator elements described in hepatitis B virus (HBV). DCHBV sequences contained two 11-bp direct repeats with DR2 located in X ORF and DR1 positioned in the C ORF. This study represents the first report of DCHBV in Serbia, providing new insights into its epidemiology and genomic features. The findings expand current knowledge of its molecular diversity and underscore the importance of genomic characterisation for understanding its role in liver disease development.

Hemotropic mycoplasmas are Gram-negative bacteria and are recognized as primary causative agents of feline infectious anemia, with a worldwide distribution and variable pathogenicity. This case report describes an unusual clinical presentation of hemoplasmosis in a seventeen-year-old spayed female cat that presented with severe flea infestation accompanied by marked weakness and lethargy. It was febrile, tachycardic, and tachypnoic, with prominent pallor of the mucous membranes. Laboratory analysis revealed severe, non-regenerative, microcytic and (falsely) hyperchromic anemia, with mild lymphopenia and slightly increased plateletcrit. The cat also tested positive for feline immunodeficiency virus (FIV). Blood smear examination raised suspicion of hemoplasmosis, which was later confirmed and identified by polymerase chain reaction (PCR) as Candidatus Mycoplasma haematominutum. Following the treatment of ectoparasites, the cat was successfully treated with enrofloxacin and erythropoiesis-stimulating agents (ESAs), avoiding blood transfusion, and afterwards made a full clinical recovery. Although immunocompromised due to FIV, the cat lived for an additional five years without further relapses. To the best of the authors’ knowledge, this is the first documented and PCR-confirmed case of feline hemoplasmosis in Bosnia and Herzegovina. It also highlights the need for conducting a larger study in this region to evaluate hemoplasma prevalence in this species.

Field evaluation of two commercial feline immunodeficiency virus antibody detection point-of-care kits in domestic cats.

Feline immunodeficiency virus (FIV) is a lentivirus that exhibits significant structural and pathological similarities to human immunodeficiency virus (HIV), establishing it as a valuable model for HIV vaccine development. In this study, artificial intelligence (AI) and immunoinformatics were employed to design a novel multi-epitope DNA vaccine targeting conserved regions of the FIV gag, pol, and env genes. Predicted B-cell and T-cell epitopes were evaluated for their capacity to induce strong immune responses while minimizing allergenic or toxic effects and were linked to the immune adjuvant PADRE. Structural analysis indicated that the vaccine construct is stable, soluble, and biocompatible, with a well-folded tertiary structure that binds Toll-like receptor 9 (TLR9) and elicits robust humoral and cellular immune responses. These findings identify a promising FIV vaccine candidate and provide insights for the development of next-generation HIV vaccines.

There is limited information about treatment success and outcomes in retrovirus-positive cats diagnosed with feline infectious peritonitis (FIP). A survey was distributed to caretakers of cats with feline leukemia virus (FeLV) and/or feline immunodeficiency virus (FIV) that were treated with GS-441524 for presumptive effusive FIP based on survey responses. Cats with FIV developed FIP at an older age and longer after retrovirus infection than cats with FeLV. The average starting dosage (7 mg/kg/d) was increased in 65% of cats, and treatment was extended in 35%. Three cats relapsed (18%). There was a 94% (16/17) twelve-week survival rate and 82% (14/17) one-year survival rate. Seven cats were alive at follow-up, a median of 1306 days (range 983-2069) after FIP diagnosis, but many cats succumbed to neoplasia. Treatment success for retrovirus-positive cats with presumptive FIP was similar to previously reported outcomes for FIP alone. This could support current evidence of successful antiviral therapy for similar populations, if noncurrent, unstandardized protocols and unlicensed product use are considered. Additional studies are needed to determine ideal protocols for rapid resolution of FIP, good long-term survival, and limited relapse in retrovirus-positive cats, and the impact of the FeLV proviral load.

Introduction: The feline immunodeficiency virus (FIV) is a retrovirus that infects domestic cats. The genetic variability of FIV, particularly in the V4–V5 region of the envelope (env) gene, may lead to specific amino acid changes that influence viral pathogenicity and the emergence of seven distinct subtypes. Consequently, this study aimed to determine the circulating genotype and identify nonsynonymous mutations by analyzing a fragment of the env gene in a sample of domestic cats from Colombia. Methods: Blood samples were collected from 151 domestic cats. Total DNA was extracted, and an 859 bp fragment of the env gene was amplified. The evolutionary history of the sequences was reconstructed using both Maximum Likelihood and Bayesian phylogenetic methods. Furthermore, nonsynonymous mutations in the translated amino acid fragment of the env gene were analyzed using a predictive tool. Results: A molecular prevalence of 5.29% (8/151) was observed in the sampled population. Genotype A was identified as the circulating genotype; however, the sequences clustered into distinct clades within this genotype. Twelve nonsynonymous amino acid substitutions were identified, among which H86R (p&lt;0.857), N88K (p&lt;0.777), E41V (p&lt;0.773), and K91D (p&lt;0.743) showed a high probability of being deleterious. Conclusions: These findings highlight the genetic diversity within FIV genotype A and underscore the potential impact of specific nonsynonymous mutations on viral pathogenicity.

Background: To date, no effective therapeutic interventions for viral infectious diseases have yet been established. A recently reported herbal medicine-based therapeutic known as “Marecipe AV” has demonstrated potent efficacy in managing viral infectious diseases. Aim: This review aimed to introduces an herbal therapy with demonstrated potent and clinically satisfactory efficacy against viral infections, and presents its therapeutic and preventive outcomes across multiple species under real-world conditions. Methods: This review summarizes the therapeutic outcomes of the Marecipe AV herbal remedy for various viral infectious diseases. Results: The findings indicate that Marecipe AV exhibits significant clinical benefits in treating a range of viral diseases, including COVID-19, African swine fever, porcine reproductive and respiratory syndrome, Newcastle disease, avian influenza, canine distemper, canine parvovirus infection, feline panleukopenia, koi herpesvirus disease, herpesviral hematopoietic necrosis disease, grass carp hemorrhagic disease, and largemouth bass ranavirus. The application of Marecipe AV herbal therapy has reduced the mortality rate associated with these lethal viral diseases from nearly 100% to close to 0%. Additionally, Marecipe AV herbal therapy has shown promising therapeutic efficacy in managing certain chronic viral infections, as well as some acute but non-fatal viral diseases, including Herpes Zoster, postherpetic neuralgia, chronic hepatitis B, feline acquired immunodeficiency syndrome, feline infectious peritonitis, feline chronic gingivostomatitis, and ulceration and erosion lesions in largemouth bass. However, the Marecipe AV herbal therapy appears to only inhibit the virus but cannot completely eliminate it. The long-term effectiveness of Marecipe AV herbal therapy in managing certain chronic viral diseases requires further investigation for validation. Conclusion: Marecipe AV herbal therapy shows potential as a groundbreaking approach to treating and managing a broad spectrum of viral infectious diseases.

The development of non-invasive diagnostic methods for zoonotic viral infections is important for animal welfare and public health. Sebum-based diagnostic methods using commercial oil-blotting films have been used for SARS-CoV-2 detection in humans, but similar strategies for veterinary use remain unexplored. Severe fever with thrombocytopenia syndrome (SFTS), caused by the SFTS virus (SFTSV), presents a major health threat in Asia-especially in Japan, where multiple cases of cat-to-veterinarian transmission have been reported. To address this need for safer diagnostics, we sought to establish a sebum-based RNA virus detection method for cats. We designed primers that efficiently detected RNA from feline sebum while distinguishing it from human and feline DNA/RNA. Using this platform, we deemed the ear to be the optimal sebum collection site and confirmed that feline immunodeficiency virus RNA can be reliably identified from ear sebum with sensitivity comparable to conventional blood-based testing. Additionally, we detected SFTSV RNA from sebum samples of infected cat. Our findings introduce a minimally invasive, safe diagnostic platform for feline viral infections, reducing animal distress while safeguarding veterinarians and pet owners from zoonotic risks. This strategy is an important step toward realizing the One Health framework by advancing the well-being of animals and humans.

Case series summaryFatal feline infectious peritonitis (FIP), caused by feline coronavirus (FCoV), can now be cured with GS-441524. Only a few unexpected clinical and laboratory observations have been reported with treatment, including lymphocytosis, eosinophilia and long-term persistence of abdominal lymphadenomegaly. Yet immune overstimulation associated with FIP might have negative long-term consequences. This report describes four cases of large-cell lymphoma (LCL) arising within 2 years of FIP diagnosis and successful treatment with legally sourced oral GS-441524 (15 mg/kg q24h), representing an incidence of 2.0% (n = 4/202) in a large treatment cohort. At LCL diagnosis, two cats were aged under 2 years, one was aged 8 years and one was aged 13 years. All cats showed weight loss, three had hyporexia and two had chronic vomiting; all tested negative for feline leukaemia virus and feline immunodeficiency virus. LCL was diagnosed by histology (n = 3) or cytology (n = 1) at 81, 365 (n = 2) and 595 days after FIP diagnosis/treatment start. The cats died a median of 15.5 days after LCL diagnosis. Neither a high FCoV viral load nor FCoV antigen, as determined by semi-quantitative RT-PCR and immunohistochemistry, respectively, was detected in any of the available samples. PCR for antigen receptor rearrangements revealed a monoclonal B-cell population in two cats, supporting a diagnosis of large B-cell lymphoma.Relevance and novel informationThe incidence of LCL reported here among cats in remission from FIP after legally sourced oral GS-441524 treatment is remarkably high compared with the general feline population. LCL should be considered a potential 'long-FIP syndrome' and/or a long-term complication after GS-441524 treatment. The pathogenesis of LCL in this context requires further clarification.

Feline immunodeficiency virus (FIV) induces immunosuppression in affected cats, increasing susceptibility to chronic and secondary infections. Rapid and accurate detection of FIV-specific antibodies is essential for effective clinical management and epidemiological monitoring. This study conducted a comparative evaluation of nine commercially available lateral flow assays (LFAs) for detecting FIV antibodies in whole blood, serum, or plasma, using a newly developed in-house enzyme-linked immunosorbent assay (ELISA) as a reference method. All tested LFAs demonstrated 100% specificity. While Vet Expert new and VetFor achieved 100% across all metrics indicating the best performance, formal statistical comparison did not reveal significant differences between the evaluated kits. Overall, the results confirm that all tested LFAs offer comparable reliability. Importantly, our in-house ELISA exhibited 100% concordance for positive samples with the commercial ELISA treated as the reference standard, confirming its reliability as a comparator. These findings emphasize the importance of selecting high-performing diagnostic tools to ensure reliable FIV detection and effective disease control strategies.

Gangrenous oesophageal necrosis (black oesophagus) is a rare condition in domestic and wild animals, but has been widely investigated and documented in humans. There are no reports of this condition in the African lion (Panthera leo). This case report describes a fatal occurrence of the condition in a 9-year-old male captive African lion with a history of severe dental caries that caused recurrent sepsis and post-prandial emesis. At first presentation, the haematology showed marked thrombocytopaenia and moderate neutropaenia and lymphopaenia suggestive of waning immunity associated with a systemic viral disease most likely Feline Immunodeficiency Virus (FIV). The condition persisted for about three years during which there were clinical interventions which included dental debridement and flushing, antibiotics, and analgesics. In spite of these interventions, the animal eventually presented with persistent vomiting and inappetence. Further therapeutic intervention, including antimicrobial therapy based on microbial culture and sensitivity did not offer any relief. The lion died 35 days after it was presented with postprandial emesis and inappetence. Postmortem examination revealed cachexia, severe dental wear, and diffuse greenish-black gangrenous necrosis of the entire oesophageal mucosa, with impaction of the distal oesophagus by approximately half a kilogram of rotting meat and 450ml of brownish fluid. Histopathology showed necrosis and inflammation of the oesophageal mucosa and submucosa as well as aspiration pneumonia. This case highlights that severe dental disease and immunosuppression can be associated with oesophageal impaction, ischaemia, and gangrenous oesophageal necrosis in the African lion. It also underscores the critical importance of proactive dental care and dietary management of captive lions to prevent this fatal condition.

Molecular detection and genotyping of feline immunodeficiency virus (FIV) in domestic cats from Tehran, Iran.

Domestic cat hepatitis B virus (DCHBV), shares similarities with human hepatitis B virus (HBV) which is associated with liver disease. We report the first case of cholangiocarcinoma in a 17-year-old spayed female cat infected with DCHBV and positive for feline immunodeficiency virus. The patient presented with vomiting, anorexia, and an elevated globulin level. Ultrasonography revealed multiple hypoechoic hepatic lesions, and histopathology confirmed cholangiocarcinoma. The tumor exhibited CK7 positivity and HepPar-1 negativity, confirming biliary origin. Quantitative PCR detected DCHBV in the spleen and ascitic fluid, while immunohistochemistry and RNA in situ hybridization revealed viral antigen and mRNA in both tumor and non-tumor liver. The presence of a viral antigen and mRNA in neoplastic tissue suggests a potential role for DCHBV in hepatobiliary carcinogenesis.

Feline immunodeficiency virus (FIV) is a retrovirus that causes lifelong infections in cats and may lead to immune dysfunction. Despite its importance for feline health, there is limited FIV data from France. This study investigated samples collected from stray and owned cats with outdoor access across France between December 2023 and January 2025 to estimate FIV seroprevalence, identify seropositivity predictors and analyse the genetic diversity of circulating strains. Serological screening was performed using a commercial ELISA. Polymerase chain reaction (PCR) was conducted on ELISA-positive sera, with selected samples analysed by Sanger sequencing for phylogenetic inference. One sample underwent metagenomic shotgun sequencing using Oxford Nanopore technology. The national seroprevalence, estimated using a Bayesian hierarchical model, was 16% (95% credible interval: 8.4–20%) overall, then 31% (21–42%) among intact male cats, 18% (CrI: 10.6–25.2%) among neutered male cats and 8.4% (CrI: 1.8–14%) among female cats. Outdoor exposure, sex and neuter status were strong predictors of seropositivity. Among strays, predicted probability of seropositivity exceeded 50% by 5 years of age. All sequenced viruses were classified as subtype A. However, the phylogenetic analysis revealed notable genetic variability, indicating at least two independent introductions of FIV into France. While related to other European strains, several isolates appeared to share distinct ancestral lineages. The metagenomic dataset yielded approximately 100,000 FIV reads among 2 million total reads, enabling full genome recovery. These findings highlight the ongoing circulation of FIV in France and provide valuable data for veterinary practitioners and future surveillance efforts in Europe.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13567-025-01672-z.

Background: The minimized pan-coronavirus (CoV) vaccine-1 developed by our laboratory contained pDNA sequences of feline coronavirus serotype-1 (FCoV1) and SARS-CoV2 (SCoV2) spike B-cell epitopes plus FCoV/SCoV2-conserved, CoV-specific polymerase cytotoxic T-lymphocyte (CTL) epitopes formulated in lipid nanoparticle (LNP). Only FCoV2 infects feline cell lines needed for developing native challenge inoculum that causes feline infectious peritonitis (FIP). Hence, Pilot Study 1 evaluated the therapeutic efficacy and safety of the pan-CoV vaccine-1 in feline immunodeficiency virus (FIV)-infected cats, with or without FCoV1 coinfection. Pilot Study 2 evaluated the cross-protective effect of pan-CoV vaccines in specific-pathogen-free (SPF) cats against intranasal challenge with FIP virus serotype 2 (FIPV2). Methods: In Study 1, we vaccinated two FIV-infected cats (one negative and another positive for FCoV1 coinfection) intramuscularly twice with CTL epitopes-LNP vaccine and later twice with pan-CoV vaccine-1. Controls included two unvaccinated FIV-infected cats with or without FCoV1 coinfection. Study 2 assessed the sequential vaccinations of three pan-CoV vaccines in four SPF cats. The first two vaccinations were with pan-CoV vaccine-2, followed by pan-CoV vaccine-3 (twice), and lastly with pan-CoV vaccine-1 (once). Three SPF controls included two cats immunized with LNP and one lacking any immunization. Pan-CoV vaccine-2 contained pDNAs with modified FCoV1/SCoV2 B-cell epitopes plus CTL epitopes in LNP. Pan-CoV vaccine-3 contained only pDNAs with FCoV1 B-cell epitopes plus CTL epitopes in LNP. Results: Study 1 demonstrated no adverse effect with 25 μg and 50 μg CTL epitopes-LNP vaccine and 50 μg pan-CoV vaccine-1. However, 100 μg pan-CoV vaccine-1 caused fever 24 h later, which was resolved by a single Meloxicam treatment. Both vaccinees developed cross-FCoV2 neutralizing antibodies (XNAbs), immunoblot binding antibodies (bAbs) to FCoV1 receptor-binding domain (RBD), and T-cell responses to FCoV1 RBD, whereas one vaccinee also developed bAbs to SCoV2 RBD. Study 2 demonstrated no adverse effects after each vaccination. Three vaccinees developed low-titer XNAbs and bAbs to FCoV2 spike-2 by the fourth vaccination. Upon challenge, all cats developed FCoV2 NAbs and bAbs to FCoV2 nucleocapsid and RBD. High vaccine-induced T-cell responses to FCoV1 RBD and T-cell mitogen responses declined with an increase in responses to FCoV2 RBD at three weeks post-challenge. Two of the three controls died from FIP, whereas one vaccinee, with the lowest vaccine-induced immunity, died from skin vasculitis lesions and detection of FIPV2 infection by semi-nested RT-snPCR in feces. Conclusions: In Pilot Study 1, the pan-CoV vaccine-LNP dose of 50 μg had no adverse effects, but adverse effects were observed at 100 μg dose. In Pilot Study 2, the FCoV1-based B-cell vaccine(s) induced low levels of XNAbs against FIPV2 and delayed challenge infection against high-dose FIPV2. The high-dose FIPV2 infections in the vaccinated and control cats started to clear, by single housing at 23–26 weeks post-challenge, whereas two cats in Pilot Study 1 cleared natural FCoV1 transmission by 26 weeks post-infection.

Feline infectious peritonitis (FIP) is a fatal but now treatable disease in cats caused by feline coronavirus (FCoV). This study prospectively investigated viral coinfections in 100 cats diagnosed with FIP and subsequently treated with oral GS-441524 (Bova UK) and their influence on outcome, focusing on viruses potentially associated with feline chronic gingivostomatitis (FCGS). Cats were tested for feline leukemia virus (FeLV), feline immunodeficiency virus (FIV), feline calicivirus (FCV), feline herpesvirus (FHV), feline foamy virus (FFV), and feline gammaherpesvirus (FcaGHV1). Coinfections were identified at the following frequencies: FCV (27), FFV (22), FHV (6), FIV (4), FcaGHV1 (2), and FeLV (2, both progressive infections). FFV infection was significantly associated with FIV (pF = 0.0021) and FHV (pF = 0.0226) infection. FCGS was present in 25/97 cats with FCV infection being associated with FCGS (pF = 0.0032); no significant associa-tions were found for the other viruses and FCGS. The 42-day oral GS-441524 treatment’s success rate was 94% (five cats died, one relapsed). Coinfections did not significantly influence disease severity or treatment outcome, although the low number of cases for some pathogens warrants further investigation. However, advanced age was associated with treatment failure, potentially due to delayed diagnosis as FIP is considered to be less common in older individuals, or to age-related changes in immune function. In summary, viral coinfections, particularly with FCV, were common and should be considered in the clinical and hygienic management of cats with FIP.

Many diseases commonly found in domestic cats may represent potential threats to wild cats. This study investigates the prevalence of selected viral pathogens in the Eurasian lynx (Lynx lynx) and European wildcat (Felis silvestris) in Poland, both being strictly-protected species vulnerable to environmental pressures. A total of 20 Eurasian lynx and five wildcats were subjected to serological and molecular analyses (ELISA and real-time PCR) aimed at confirming the presence of antibodies and genetic material for feline leukemia virus (FeLV), feline immunodeficiency virus (FIV), feline coronavirus (FCoV), feline calicivirus (FCV), feline herpesvirus (FHV), and feline panleukopenia virus (FPV). Antibodies were most frequently detected against FCV (32%), and FHV (32%), FCoV (23.1%), and FeLV (16%). No FIV and FPV antibodies were detected. Viral genetic material was confirmed in four animals, with FCV being most prevalent (9.1%), followed by FeLV and FHV (each 4.5%). Statistically significant associations were observed between the presence of FCV and FHV. These results suggest that viral infections may play a role in limiting wild felid populations in Central Europe. Continued surveillance is crucial to inform conservation efforts and assess long-term health risks.

Feline herpesvirus and calicivirus: Occurrence and pathology in cats with respiratory disease.

Multiple cats in an overcrowded colony died of acute kidney injury with renal amyloidosis. To investigate the etiology of these deaths, we performed histological analysis of the kidneys of 27 colony cats and 29 noncolony cats (8 with acute kidney injury, 9 with chronic kidney disease, and 12 nonazotemic). Congo red-positive amyloid deposition was observed prominently in the glomeruli and cortical and medullary interstitium and was identified as AA amyloid using permanence. The prevalence and severity of renal amyloidosis were significantly higher in colony cats than in noncolony cats. Feline immunodeficiency virus showed no association with feline leukemia virus infection. Based on our results, adverse environmental conditions may accelerate the incidence of feline renal amyloidosis.