Periodontal disease is a significant problem in companion animals such as dogs and cats. However, there is little information available about fimbriae association of periodontal disease in companion animals. In this study, we have purified and characterized a fimbriae from Porphyromonas salivosa ATCC 49407. The molecular mass of this protein was approximately 60-kDa, as estimated by SDS-PAGE. Immunogold electron microscopy revealed that anti-60-kDa fimbrial serum bound to fimbria on the cell surface of P. salivosa ATCC 49407. However, fimbriae of P. gingivalis and P. gulae were not labeled with the same antibody. Immunoelectron-microscopic studies and immunoblot analysis revealed that antigenicity and molecular weight were distinct from previously reported Porphyromonas fimbrial proteins. The amino acid sequence of the N-terminal 15 residues of the 60-kDa fimbrillin protein revealed only 3 of 15 residues identical to other Porphyromonas species fimbrillin proteins. Thus, the N-terminal amino acid sequence of the 60-kDa fimbrillin protein of P. salivosa clearly differed from previously reported fimbrillin proteins. The level of adherence of the P. salivosa was 1.81%. It was confirmed that P. salivosa can adheres to human cells. These results suggest that the 60-kDa fimbriae of P. salivosa ATCC 49407 is a new type of fimbria and may have an important factor in the adherence host cells. We suggest that the surface structure of P. salivosa may have a role in the colonization of this organism in periodontal pockets in companion animals.

Hemotropic mycoplasma (hemoplasma), a neglected vector-borne pathogen in goats, causes extensive economic damage to farmers due to production losses. In this study, 107/295 (36.27%) goats sampled from 4 farms (Barili, Danao City, Dumanjug and Minglanilla) in Cebu, Philippines tested positive for PCR targeting the 16S rRNA gene of Mycoplasma. All hemoplasma-positive goats were from Barili and no clinical sign was observed. Sex (P=0.0005) and age (P=0.03) were found associated with hemoplasma infection. Mycoplasma ovis, Candidatus Mycoplasma haemobos, Candidatus Mycoplasma haemominutum and 3 Uncultured Mycoplasma sp. sequences were identified by sequencing analysis. This is the first report of molecular detection and genetic characterization of hemoplasmas in goats in the Philippines.

The emergence and spread of aminoglycoside-resistant bacteria are a public health concern. The acquisition of the genes encoding 16S rRNA methylases, such as armA, rmtA, and rmtB, confers high-level resistance to aminoglycosides. However, the prevalence has not been well investigated in Japanese veterinary fields. To determine the prevalence of 16S rRNA methylases in animals, we detected 16S rRNA methylases genes in Gram-negative bacteria from animals. Here, we report the isolation of rmtB amd armA from two of the 446 Escherichia coli (0.5%) and one of the 103 Klebsiella spp. isolates (1.0%) from companion animals, respectively. However, none of the isolations were observed from 2445 E. coli isolates derived from livestock in Japan. The prevalence of 16S rRNA methylases in animals, especially in companion animals, should be carefully monitored in Japanese veterinary fields to avoid the spreading of the genes.

Strangles is a commonly diagnosed and important infectious disease of equids worldwide, caused by Streptococcus equi subsp. equi. We determined the SeM genotypes of S. equi isolated from imported horses at the Japanese border within the past 8 years, which allowed us to classify 12 strains isolated from these horses from each exporter into four allelic groups. These alleles were different from the alleles of past isolates found in Japan. Furthermore, four strains classified into the same allele were isolated from horses from one exporter over several years. In this study, S. equi isolates from different exporters had different SeM alleles. Attention to the hygiene status of farms will be necessary to prevent the incursion of strangles.

Brown adipocytes, which exist in brown adipose tissue (BAT), are activated by adrenergic stimulation, depending on the activity of uncoupling protein 1 (UCP1). Beige adipocytes emerge from white adipose tissue (WAT) in response to chronic adrenergic stimulation. We investigated obesity-related changes in responses of both types of adipocytes to adrenergic stimulation in mice. Feeding of mice with high-fat diets (HFD: 45%-kcal fat) for 14 weeks resulted in significantly higher body and WAT weight compared to feeding with normal diets (ND: 10%-kcal fat). Injection with β3-adrenergic receptor agonist CL316,243 (CL; 0.1 mg/kg, once a day) for one week elevated the mRNA and protein expression levels of UCP1 in BAT, irrespective of diet. In WAT, CL-induced UCP1 expression in ND mice; however, the responses to CL treatment were attenuated in HFD mice, indicating that CL-induced browning of WAT was impaired in obese mice. Flow cytometric analysis revealed a significant decrease in platelet-derived growth factor receptor (PDGFR) α-expressing beige adipocyte progenitors in WAT of HFD mice compared with those of ND mice. Expression of PDGF-B, a PDGFRα ligand, increased in WAT following CL-injection in ND mice, but not in HFD mice. Treatment of mice with a PDGFR inhibitor significantly decreased CL-dependent UCP1 protein induction in WAT. Our study demonstrates that β3-adrenergic stimulation-dependent beige adipocyte induction in WAT is impaired by obesity in mice, potentially due to obesity-dependent reduction in the number of PDGFRα-expressing progenitors and decreased PDGF-B expression.

We investigated the relationships between ruminal pH, gene expression in the rumen epithelium (RE), peripheral blood mononuclear cell subpopulations, and blood metabolites in Holstein calves during weaning transition. Calves (Weaning group, n=7) were assigned to one of two groups, and fed calf starter with forage (Forage group, n=3) or without forage (Starter group, n=4). Ruminal pH was measured continuously. Samples were collected at −1, 0, 1, and 3 weeks (blood and rumen fluid) or 3 weeks (rumen epithelium) after weaning. In the Weaning group, ruminal pH increased, and several blood metabolites increased (blood urea nitrogen [BUN], beta-hydroxybutyrate [BHB], and gamma-glutamyl transferase [GGT]) or decreased (total cholesterol [T-CHO] and phospholipid) after weaning. Ruminal pH was positively correlated with CD8⁺CD45R⁻ cell populations and blood metabolites (BUN, glucose, and BHB) and negatively correlated with GGT activity. The 24 hr mean ruminal pH was higher in the Forage group during weaning transition, and toll-like receptor 4 mediated signaling pathway was activated in the Starter group at 3 weeks post-weaning. The number of CD8⁺CD45R⁻ cells tended to be higher, and several blood metabolites (glucose, triglycerides, T-CHO, and phospholipid) were higher in the Forage group after weaning. Calves with higher ruminal pH also showed a greater energy metabolism status simultaneously with lesser hepatic disturbance enzymes in the peripheral blood. The results of our study indicate that serum GGT activity may be a plausible biomarker for predicting ruminal acidosis in Holstein calves during weaning transition.

Many of the reports summarizing neurological disorders in cats considered only a limited disease group(s). There is only one large-scale survey on neurological disorders in cats based on the histopathological viewpoint. We described the localizations and frequencies of neurological diseases in a large population of cats that were referred to the Kyoto Animal Referral Medical Center between 2009 and 2016. We attempted to determine the localization of lesions at the time of the examination in each case and to classify the disease etiologies of these 276 cats with neurological disorders retrospectively. There were 174 cases with lesions in the brain region, 14 cases with lesions in the cervical cord region, 34 cases with lesions in the thoracolumbar cord region, and 54 cases with lesions in the peripheral neuromuscular region. High morbidity rates were observed in cases of idiopathic epilepsy and intracranial tumor in the brain region, spinal cord infarction in the cervical cord region, spinal cord infarction and spinal cord tumor in the thoracolumbar cord region, and peripheral vestibular dysfunction arising from otitis media/interna in the peripheral neuromuscular region. It was suggested that there is a higher number of brain diseases than spinal cord and peripheral neuromuscular diseases in cats. Idiopathic and neoplastic diseases were common in the brain region, vascular diseases were common in the spinal cord region, and infectious diseases were common in the peripheral neuromuscular region.

The purpose of this study is to compare the assessment of pre- and postpartum oxidative stress-related causal indicators and other metabolites in cows with postpartum subclinical ketosis (SCK). The prepartum serum malondialdehyde concentration and body condition score (BCS) were elevated in the SCK cows (n=17) compared to healthy controls (n=12), while the insulin sensitivity check index was lower in the SCK cows than in the controls. Oxidative stress is enhanced in cows with prepartum higher BCS, causing decreased insulin sensitivity, and may be associated with onset of postpartum SCK. However, paraoxonase alone might be insufficient to assess the antioxidant state because of no difference in pre- and postpartum activities between the two groups.

A 12-year-old, male miniature dachshund has an ulcer on the footpad of the right hind limb. Despite treatment for longer than 6 months, the ulcer did not heal. Biopsy of the lesion was done to make a definitive diagnosis. Histologically, there were lumens containing weakly eosinophilic fluid surrounded by tumor cells with a similar circular pale nucleus and distinct nucleoli that showed some variation in size. Immunohistochemically, the tumor cells were positive for cytokeratin (AE1/AE3) and vimentin, were negative for S100 and p63. A poorly differentiated eccrine adenocarcinoma was diagnosed. Treatment was started with toceranib, an anti-angiogenic agent, and enlargement of the lesion was not observed during the administration period.

A neutered male Golden Retriever was referred with a 2-week history of dry mouth. Multiple and bilateral enlargement of the lacrimal and salivary glands showing heterogeneous internal enhancement was identified on contrast-enhanced computed tomography (CT). Ultrasonographic examination detected multifocal hypoechoic areas within the swollen submandibular salivary glands, which were histopathologically diagnosed as lymphoplasmacytic sialoadenitis. As both imaging and histopathological findings were in accordance with those in human Sjögren’s syndrome, a provisional diagnosis of Sjögren’s-like syndrome was made. Immunosuppressive drugs promptly improved clinical signs concurrently with the abnormal sonographic findings, indicating the feasibility of ultrasonography in monitoring therapeutic outcomes. Herein, we discuss a proposed criteria set for diagnosis of Sjögren’s-like syndrome in veterinary medicine.

In an 8-year-old Labrador Retriever with progressive anorexia, constipation, and depression, CT revealed intussusception of the cecum into the ascending colon and a small cecal mass showing strong enhancement on arterial phase. The ileocecocolic junction was surgically resected and histologically diagnosed as cecocolic intussusception with carcinoid tumor. The carcinoid tumor worked as a lead point of intussusception in this case. Dual phasic CT is useful to assess the presence of gastrointestinal tumors as lead points in old dogs with intussusception.

Persistent papillomatosis on footpads related to canine papillomavirus type 2 (CPV-2) infection has been described in dogs with immunocompromised condition. A 9-year-old, male French bulldog was presented with cauliflower-like nodules on the footpads of his left front leg. Histopathological examination revealed multiple finger-like projections of squamous epithelium with intranuclear inclusion bodies. Immunohistochemistry using an anti-bovine papillomavirus antibody demonstrated immunostaining in the keratinocytes. Partial genome DNA of CPV-2 was amplified from the lesion. Full genome sequence of CPV-2 in the subject showed 99.95% nucleotide identity with that of CPV-2 from the reference data. Two weeks after a biopsy, the skin lesion spontaneously regressed without any specific treatment. In non-immunocompromised dogs, CPV-2-related footpad papillomatosis could spontaneously resolve after a biopsy.

The anesthetic effects of alfaxalone combined with medetomidine and butorphanol were investigated for ICR, BALB/c, and C57BL/6 mice. Mice were administered a combination of 0.5 or 0.75 mg/kg medetomidine and 5 mg/kg butorphanol with 30 or 40 mg/kg alfaxalone (0.5MBA30, 0.75MBA30 and 0.75MBA40, respectively). The drug combinations were administered subcutaneously and were compared with a widely used combination of 0.3 mg/kg medetomidine, 4 mg/kg midazolam, and 5 mg/kg butorphanol (MMB). All three MBA combinations achieved surgical anesthesia, although the recovery time was longer with 0.75MBA30 and 0.75MBA40 compared with 0.5MBA30. Furthermore, several mice exhibited a considerable jumping reaction immediately after injection with 0.75MBA30 and 0.75MBA40. Therefore, 0.5MBA30 may be suitable for inducing surgical anesthesia in the mouse strains tested. The anesthetic scores for 0.5MBA30 were improved compared with those of MMB in all three mouse strains; however, the body temperature drop in C57BL/6 mice was greater with 0.5MBA30. Our results show that the alfaxalone combination, 0.5MBA30, should allow surgical operations that are more stable in more strains of mice than MMB, although the combination may cause hypothermia, especially in C57BL/6 mice.

The cat is a reported reservoir for several zoonotic pathogens, including Cryptosporidium spp., Giardia duodenalis, and Blastocystis sp. These parasites represent a significant, but often neglected, threat to humans and animals. Furthermore, Tritrichomonas foetus has been described inhabiting the digestive tract of cats, and may be causative agents of gastrointestinal symptoms. However, scant data are available concerning the molecular epidemiology of these parasites in domestic cats in China. This study examined fecal samples from domestic cats in Eastern China to unravel the molecular epidemiology of four protozoans. Of the 346 samples examined, 47 (13.6%) were positive for the detected pathogens, including 8 (2.3%), 5 (1.4%), 2 (0.6%), and 35 (10.1%) samples positive for Cryptosporidium spp., G. duodenalis, Blastocystis sp., and T. foetus, respectively. Co-infection with Cryptosporidium spp. and T. foetus was detected in three cats, no other mixed infections were observed. No age, sex or fecal condition predisposition was observed with any of the four pathogens. The species/assemblages/subtypes/genotypes were C. felis, Assemblage A and F, ST1, and cat genotype for Cryptosporidium spp., G. duodenalis, Blastocystis sp., and T. foetus detected in this study, respectively. The presence of zoonotic species/assemblages/subtypes/genotypes poses a threat to public health. These findings provide useful information for the design of prevention and control strategies to reduce the burden of protozoal infections in cats.

An 11-month-old female Japanese Black calf had showed chronic intestinal symptoms. A large mass surrounding the colon wall that was continuous with the colon submucosa was surgically removed. After recurrence and euthanasia, a large mass in the colon region and metastatic masses in the omentum, liver, and lung were revealed at necropsy. Pleomorphic small cells proliferated in the mass and muscular layer of the colon. The cells were positively stained with anti-doublecortin (DCX), PGP9.5, nestin, and neuron specific enolase (NSE). Thus, the diagnosis of peripheral neuroblastoma was made. This is the first report of enteric peripheral neuroblastoma in animals. Also, clear DCX staining signal suggested usefulness of DCX immunohistochemistry to differentiate the neuroblastoma from other small cell tumors in cattle.

Systemic amyloidosis is rarely reported among cetaceans, and a surveillance dedicated for its occurrence across a certain geographic location has not been reported. Between 2013 and 2018, comprehensive gross and histopathologic examinations were conducted on 54 animals comprising 11 species of stranded and bycaught cetaceans in Hokkaido, Japan. Systemic amyloidosis was diagnosed in 2 out of 3 Stejneger’s beaked whales (Mesoplodon stejnegeri), through Congo red staining and immunohistochemistry for amyloid A. The kidney and gastrointestinal tract had the largest amounts of amyloid deposits, representing a previously undescribed organ distribution in the species. The current study demonstrates the possibility of Stejneger’s beaked whales being prone to the development of systemic amyloidosis, and highlights the need for further investigations.

Mercury (Hg) and cadmium (Cd) are the major toxic heavy metals and are known to induce neurotoxicity. Although many studies have shown that several heavy metals have neurotoxic effects, the cellular and molecular mechanisms thereof are still not clear. Oxidative stress is reported to be a common and important mechanism in cytotoxicity induced by heavy metals. However, the assays for identifying toxic mechanisms were not performed under the same experimental conditions, making it difficult to compare toxic properties of the heavy metals. In this study, we investigated the mechanisms underlying neurotoxicity induced by heavy metals and H₂O₂, focusing on cell death, cell proliferation, and oxidative stress under the same experimental condition. Our results showed that MeHg caused lactate dehydrogenase (LDH) release, caspase activation and cell-cycle alteration, and ROS generation in accordance with decreased cell viability. HgCl₂ caused LDH release and cell-cycle alteration, but not caspase activation. CdCl₂ had a remarkable effect on the cell cycle profiles without induction of LDH release, caspase activation, or ROS generation. Pretreatment with N-acetyl-l-cysteine (NAC) prevented the decrease in cell viability induced by MeHg and HgCl₂, but not CdCl₂. Our results demonstrate a clear difference in neurotoxic mechanisms induced by MeHg, HgCl₂, CdCl₂ or H₂O₂ in SH-SY5Y cells. Elucidating the characteristics and mechanisms of each heavy metal under the same experimental conditions will be helpful to understand the effect of heavy metals on health and to develop a more effective therapy for heavy metal poisoning.

Wistar Kyoto (WKY) rats, an animal depression model, display abnormal behaviors such as hypoactivity and depression-like behavior compared with Wistar (WIS) rats as a control. A previous study confirmed a dysfunction of amino acid metabolism in the brain of WKY rats compared with that of WIS rats. At the neonatal stage, free amino acids in milk are important nutrients because they act as immediate nutrients for offspring and may affect later health and behavior of the offspring. Therefore, the present study aimed to investigate free amino acid concentrations in milk and the relationships between free amino acid concentrations in milk and plasma in WIS and WKY rats. The concentrations of ten of the determined free amino acids in milk were significantly higher, but only L-methionine was significantly lower, in WKY rats. Six free amino acids had significantly higher concentrations in colostrum and two free amino acids had higher concentrations in matured milk. Free amino acid concentrations in plasma changed by both genetic background and lactation stage; however, the patterns of change in most free amino acid concentrations except for taurine in plasma were similar between WIS and WKY rats. The transport ratio of free amino acids from plasma to milk was not similar among the free amino acids tested, and each free amino acid was influenced by the genetic background and/or the type of milk.

Atypical bovine spongiform encephalopathy (BSE), first identified in 2004, poses a threat due to the potential to spread the disease to cattle and other animals, including humans. Here, we estimated prion titers in various tissues of cattle infected with atypical BSE using a real-time quaking-induced conversion assay that detects amyloid seeding activity of a disease-specific prion protein, PrP^Sc, a major component of prions. PrP^Sc was detected both in and outside of nerve tissues, and some of the peripheral nerve tissues contained relatively high prion titers. Low titers of prions were also observed in masseter, jejunum, and adrenal glands. Quantitative data on prion infectivity in tissues of atypical BSE-affected cattle is useful to assess the risk of atypical BSE.

Thirty-seven specimens of wild boar sera were collected from August 2016 to March 2018 in Ishikawa prefecture, Japan. Thirty-two specimens (86.5%) were positive for neutralizing antibodies against Japanese encephalitis virus (JEV). Eight specimens (21.6%) were positive for IgM antibodies against JEV. One sample was obtained from a wild boar captured in February during the winter season. Four other serum specimens obtained during the winter season were positive using a JEV gene-specific PCR assay. Based on IgM and PCR assays, wild boars were infected with JEV during the winter season, suggesting that the prevalence of JEV antibodies in wild boars in Ishikawa is high and JEV activity is possible during winter in this region. In addition, wild boars may play an important role in the infection cycle of JEV.

To evaluate sedative and physiological effects of low dose intramuscular (IM) alfaxalone, six healthy rabbits were administered single IM doses of alfaxalone at 1mg/kg (IM1), 2.5 mg/kg (IM2.5), or 5 mg/kg (IM5) with a minimum of 7-day washout period. Sedative effects were subjectively evaluated using a composite measure scoring system (maximum sedation score of 16) and pulse rate, respiratory rate, non-invasive blood pressure, and percutaneous oxygen-hemoglobin saturation were measured before and after IM alfaxalone. Loss of righting reflex (LRR) was achieved in all rabbits after IM2.5 and IM5 treatments but in only three rabbits after IM1 treatment. Median (interquartile range) times to LRR were 16 min (15–17), 6 min (6–6), and 4 min (4–4), and median durations of LRR were 0.5 min (0–7), 22.5 min (19–27), and 53 min (48–58) after IM1, IM2.5, and IM5 treatments, respectively. The duration of LRR after IM5 treatment was significantly longer than those after IM1and IM2.5 treatments (P<0.01). Median value of total sedation scores peaked at 10 min [score 3.5 (3–4)], from 10 min [score 13.5 (12–14)] to 15 min [score 13.5 (12–14)], and from 10 min [score 15 (12–15)] to 15 min [score 15 (14–15)] after IM1, IM2.5, and IM5 treatments, respectively. No rabbit showed circulatory depression and apnea although respiratory rate decreased after IM 2.5 and IM5 treatments. In conclusion, alfaxalone produced a dose-dependent sedative effect and a deep sedation was achieved by alfaxalone at 2.5 mg/kg IM in rabbits.

Thoracolumbar intervertebral disk herniation (TL-IVDH) with caudal articular process anomalies has been reported in Pugs. It currently remains unclear whether congenital caudal articular process aplasia/hypoplasia predisposes to the development of TL-IVDH. However, there are difficulties in proving the causal relationship between caudal articular process anomalies and TL-IVDH. The aim of this study was to describe the prevalence of TL-IVDH at the vertebral space containing anomalous and normal caudal articular processes in Pugs. Fifty-seven pugs were eligible to be included in this study. Caudal articular process aplasia/hypoplasia affected 52/57 (91.2%) dogs. The caudal articular process anomalies were most frequently located between T10 and T13. Colocalization of caudal articular process aplasia/hypoplasia and TL-IVDH was detected in 11 dogs (19.3%). The prevalence of TL-IVDH at vertebral spaces containing abnormal caudal articular processes was 12.3%, whereas the prevalence of TL-IVDH at vertebral spaces containing normal articular processes was 2.4%. With the increase in the number of vertebrae with caudal articular process anomalies, the prevalence of TL-IVDH also increased. The results of this study suggested the prevalence of caudal articular process anomalies was high in Pugs. The caudal articular process anomalies could be associated with TL-IVDH. A large cohort is needed to prove the causal relationship between caudal articular process anomalies and TL-IVDH.

The aim of this study was to examine the treatment outcomes of tibial fracture using different configurations of transfixation pinning and casting (TPC) in eight cattle. After pins were inserted to stabilize the fracture site, cast material was placed from the level of the stifle to the hoof (full TPC) in six cases and from the stifle to the proximal metatarsus (partial TPC) in two cases. Five cattle (three full TPC and two partial TPC cases) underwent TPC removal 36–86 days after surgery and resumed productivity. The other three cattle which underwent full TPC suffered from irreversible orthopedic complications within 5 weeks of surgery, while a prolonged healing process was observed in the partial TPC cases. Although TPC is an effective method for treating bovine tibial fracture, full TPC may result in a guarded prognosis in some cattle. However, partial TPC can delay healing. Surgeons should choose the optimal TPC configuration while considering the various factors that affect the healing process.

Mesothelioma is a very aggressive malignant tumor with low survival rates that is often diagnosed belatedly. Pericardial effusion is a common consequence in cases of mesothelioma, with pericardiocentesis and pericardiectomy indicated; therefor thoracocentesis is necessary to drain the contents no longer retained in the pericardium. The present report describes a mesothelioma–carrying dog with a history of cardiac tamponade that underwent thoracoscopic pericardiectomy and, later, thoracoscopic implantation of a fully implantable catheter to function as a thoracic drain. In the consulted literature, there is no use of a fully implantable catheter for this purpose. The authors consider that there was an improvement in the quality of life.

The purpose of this study was to clarify the therapeutic effects of oxytetracycline (OTC) as a first-line antibiotic in cattle with acute Escherichia coli mastitis and systemic signs. Drug susceptibility was determined by the minimum inhibitory concentration (MIC) of E. coli isolated from cows with acute E. coli mastitis (n=38). Cattle were divided into OTC-susceptible (S, n=30) and OTC-resistant (R, n=8) groups. They were further subdivided according to susceptibility to the antibiotic used as a second treatment, into susceptible-susceptible (SS, n=30), resistant-susceptible (RS, n=5), and resistant-resistant (RR, n=3) groups. Clinical signs on the day after initial treatment were compared between S and R groups as short-term indicators of treatment effects. The 28-day survival rate of cattle was then compared among SS, RS, and RR groups as a long-term indicator of treatment effects. There were no differences in clinical signs between S and R groups on the day after the first dose, but the 28-day survival rate was significantly greater in the SS group than in the RR group (P=0.04). The results demonstrated that an effective drug is essential for first-line treatment of acute coliform mastitis. However, anticipating the effectiveness of a first-line antibiotic based on clinical symptoms at the second day of treatment is impossible. It is important to build a picture of drug resistance trends in cattle herds for empirical selection of antibiotics to be administered.

Feline infectious peritonitis virus (FIPV) causes a severe, immune-mediated disease called FIP in domestic and wild cats. It is unclear whether FIP transmits from cat to cat through the oral route of FIPV infection, and the reason for this includes that FIP is caused by oral inoculation with some FIPV strains (e.g., type II FIPV WSU 79-1146), but is not caused by other FIPV (e.g., type I FIPV KU-2 strain: FIPV-I KU-2). In this study, when cats passively immunized with anti-FIPV-I KU-2 antibodies were orally inoculated with FIPV-I KU-2, FIP was caused at a 50% probability, i.e., FIPV not causing FIP through oral infection caused FIP by inducing antibody-dependent enhancement. Many strains of type I FIPV do not cause FIP by inoculation through the oral route in cats. Based on the findings of this study, type I FIPV which orally infected cats may cause FIP depending on the condition.