Single Cat Research Articles

Minireview: Applications of NMR-based metabolomics for the detection and characterisation of toxoplasmosis in felids.

Toxoplasmosis is an infection caused by the intercellular protozoan parasite Toxoplasma gondii. The parasite has the three-stage life cycle: oocysts, tachyzoites, and bradyzoites. Felids are the only known hosts for the sexual reproduction of T. gondii and, therefore, play a crucial role in the transmission of toxoplasmosis. A single cat could spread the parasite to many hosts. Due to the intercellular nature of the parasite, T. gondii strongly depends on a host's metabolism in order to leverage carbon and nutrient sources. Therefore, the parasite could be detected in body fluids via observation and analysis of metabolic alterations. A range of analytical techniques such as nuclear magnetic resonance (NMR), mass spectrometry coupled with liquid chromatography, and Raman spectroscopy could be applied for the analysis of body fluids of infected animals. However, NMR consists of highly specific analytical techniques due to high reproducibility, availability of a variety of databases, and the ability to obtain the structures of unknown compounds. We present the current extent of NMR-based metabolomics on felid toxoplasmosis and suggest future considerations.

An artificial neural network-based model to predict chronic kidney disease in aged cats.

BackgroundChronic kidney disease (CKD) frequently causes death in older cats; its early detection is challenging.ObjectivesTo build a sensitive and specific model for early prediction of CKD in cats using artificial neural network (ANN) techniques applied to routine health screening data.AnimalsData from 218 healthy cats ≥7 years of age screened at the Royal Veterinary College (RVC) were used for model building. Performance was tested using data from 3546 cats in the Banfield Pet Hospital records and an additional 60 RCV cats—all initially without a CKD diagnosis.MethodsArtificial neural network (ANN) modeling used a multilayer feed‐forward neural network incorporating a back‐propagation algorithm. Clinical variables from single cat visits were selected using factorial discriminant analysis. Independent submodels were built for different prediction time frames. Two decision threshold strategies were investigated.ResultsInput variables retained were plasma creatinine and blood urea concentrations, and urine specific gravity. For prediction of CKD within 12 months, the model had accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 88%, 87%, 70%, 53%, and 92%, respectively. An alternative decision threshold increased specificity and PPV to 98% and 87%, but decreased sensitivity and NPV to 42% and 79%, respectively.Conclusions and Clinical ImportanceA model was generated that identified cats in the general population ≥7 years of age that are at risk of developing CKD within 12 months. These individuals can be recommended for further investigation and monitoring more frequently than annually. Predictions were based on single visits using common clinical variables.

Feline leukaemia virus infection: A practical approach to diagnosis.

Feline leukaemia virus (FeLV) is a retrovirus of domestic cats worldwide. Cats lacking strong FeLV-specific immunity and undergoing progressive infection commonly develop fatal FeLV-associated disease. Many aspects of FeLV infection pathogenesis have been elucidated, some during more recent years using molecular techniques. It is recommended that the FeLV status of every cat is known, since FeLV infection can influence the prognosis and clinical management of every sick cat. Moreover, knowledge of a cat's FeLV status is of epidemiological importance to prevent further spread of the infection. Diagnosing FeLV infection remains challenging due to different outcomes of infection, which can vary over time depending on the balance between the virus and the host's immune system. Furthermore, testing for FeLV infection has become more refined over the years and now includes diagnostic assays for different viral and immunological parameters. Knowledge of FeLV infection pathogenesis, as well as the particulars of FeLV detection methods, is an important prerequisite for correct interpretation of any test results and accurate determination of a cat's FeLV status. The current review presents recent knowledge on FeLV pathogenesis, key features to be determined in FeLV infection, and frequently used FeLV detection methods, and their characteristics and interpretation. An algorithm for the diagnosis of FeLV infection in a single cat, developed by the European Advisory Board on Cat Diseases, is included, and FeLV testing in specific situations is addressed. As well as increasing awareness of this deadly infection in domestic cats, the aim is to contribute diagnostic expertise to allow veterinarians in practice to improve their recognition, and further reduce the prevalence, of FeLV infection.

Werewolf, There Wolf: Variants in Hairless Associated with Hypotrichia and Roaning in the Lykoi Cat Breed.

A variety of cat breeds have been developed via novelty selection on aesthetic, dermatological traits, such as coat colors and fur types. A recently developed breed, the lykoi (a.k.a. werewolf cat), was bred from cats with a sparse hair coat with roaning, implying full color and all white hairs. The lykoi phenotype is a form of hypotrichia, presenting as a significant reduction in the average numbers of follicles per hair follicle group as compared to domestic shorthair cats, a mild to severe perifollicular to mural lymphocytic infiltration in 77% of observed hair follicle groups, and the follicles are often miniaturized, dilated, and dysplastic. Whole genome sequencing was conducted on a single lykoi cat that was a cross between two independently ascertained lineages. Comparison to the 99 Lives dataset of 194 non-lykoi cats suggested two variants in the cat homolog for Hairless (HR) (HR lysine demethylase and nuclear receptor corepressor) as candidate causal gene variants. The lykoi cat was a compound heterozygote for two loss of function variants in HR, an exon 3 c.1255_1256dupGT (chrB1:36040783), which should produce a stop codon at amino acid 420 (p.Gln420Serfs*100) and, an exon 18 c.3389insGACA (chrB1:36051555), which should produce a stop codon at amino acid position 1130 (p.Ser1130Argfs*29). Ascertainment of 14 additional cats from founder lineages from Canada, France and different areas of the USA identified four additional loss of function HR variants likely causing the highly similar phenotypic hair coat across the diverse cats. The novel variants in HR for cat hypotrichia can now be established between minor differences in the phenotypic presentations.

Reversal of Renal Insufficiency in an Aging Cat: A 5-year Multi-Crossover Case Study

Renal failure is a leading cause of suffering and death in domestic cats, with approximately 1 in 3 cats affected. Current standard-of-care treatment usually involves palliative care, diets restricted in protein and phosphorus, plenty of fluids, and sometimes vitamin D and Omega-3. But even with early detection, which is difficult, treatment options are limited and often are not very effective. Dietary restrictions and palliative care are often the best that can be offered, but the creatinine levels tend to inexorably creep upward toward eventual kidney failure and death. We report the effectiveness of the use of a low-frequency, low-intensity, non-invasive treatment using Pulsed Electro-Magnetic Fields, specifically tuned to inductively generate micro-electric currents in deep tissues (ICES®-PEMF). This report chronicles the return to normal and then reversion to renal insufficiency in a single cat, when ICES®-PEMF was applied, then withheld, then applied again, over three cycles of application and non-application, over a 5-year period. A return to normal creatinine levels, with a subsequent return to renal insufficiency as indicated by loss of control of creatinine, correlated precisely with the application and non-application of ICES®-PEMF. The pattern observed during each cycle was as follows: when applied 2 to 3 times weekly for 20-60 minutes each treatment, creatinine levels declined to normal range within 2-3 months. During periods when treatment was discontinued, creatinine levels began to climb to high levels again. We suggest the further study and potential use of ICES®-PEMF as an effective, inexpensive, safe, non-invasive treatment for feline kidney disease.

The efficacy of a topical formulation of selamectin plus sarolaner in preventing the development of a macrocyclic lactone-resistant strain of Dirofilaria immitis in cats

Revolution®/Stronghold® Plus, a topical endectocide incorporating 6 mg/kg selamectin plus 1 mg/kg sarolaner, is approved for use in cats to prevent heartworm disease. The efficacy of selamectin has not previously been evaluated against any macrocyclic lactone (ML)-resistant heartworm strains in cats for prevention of heartworm disease. In this study, an experimental combination formulation of selamectin (6 mg/kg) plus sarolaner (2 mg/kg) was assessed for preventing the development of a ML-resistant strain of Dirofilaria immitis in cats.Forty purpose-bred domestic shorted-haired cats (20 males; 20 females) from 7-9 months of age and negative for heartworm antigen prior to study inclusion were used. On Day -30, cats were inoculated with 100 D. immitis L3 (ZoeMO strain) subcutaneously in the inguinal area. Cats were randomly allocated to one of the following four treatments with associated dosing regimens: T01 (vehicle-treated control on Days 0, 28, and 56), T02 (single dose of selamectin plus sarolaner combination on Day 0 only), T03 (selamectin plus sarolaner combination on Days 0, 28, and 56) or T04 (single dose of selamectin on Day 0 only). All treatments were administered topically in an isopropyl alcohol-based formulation. Selamectin was administered at 6 mg/kg in both standalone and combination formulations. Sarolaner was administered at 2 mg/kg. Cats were necropsied on Day ∼145 (∼175 days post infection) and adult worms were counted.Nine of ten cats in the control group (T01) were infected with adult worms (range, 1-23; geometric mean, 3.5). In contrast, all cats in T03 had zero heartworms. Only two cats in T02 (0-3; 0.2) and a single cat in the T04 (0-1; 0.1) had heartworms. Compared to T01 (control cats), all treated cats had significantly (p < 0.0001) reduced worm burdens, with treatment efficacies of 100% (T03), 93.5% (T02) and 98% (T04).A topical combination of selamectin (6 mg/kg) plus sarolaner (2 mg/kg) was 100% efficacious in preventing the development of an ML-resistant strain of D. immitis (ZoeMO) in cats when administered as three consecutive monthly treatments. A single dose was highly (93.5%) but incompletely effective.

Feline sporotrichosis in Asia.

Sporothrix schenckii sensu lato is currently recognized as a species complex with only Sporothrix brasiliensis, Sporothrix schenckii sensu stricto, Sporothrix globosa and Sporothrix pallida identified to cause disease in the cat. Feline sporotrichosis in Asia is mainly reported from Malaysia where a single clonal strain of clinical clade D, Sporothrix schenckii sensu stricto manifesting low susceptibility to major antifungal classes, has been identified as the agent of the disease. Sporothrix globosa has been identified to cause disease from a single cat in Japan while the specific species of agent has not been identified yet for the disease in Thailand. Despite efforts to elucidate and describe the pathogenicity of the agent and the disease it causes, the paucity of data highlights the need for further molecular epidemiological studies to characterize this fungus and the disease it causes in Asia. Its prognosis remains guarded to poor due to issues pertaining to cost, protracted treatment course, zoonotic potential and low susceptibility of some strains to antifungals.

The genome of the marine rotifer Brachionus koreanus sheds light on the antioxidative defense system in response to 2-ethyl-phenanthrene and piperonyl butoxide

Brachionusspp. (Rotifera: Monogononta) have been introduced as ecotoxicological model-organisms that are widely distributed in aquatic environments. Among the Brachionus spp., the monogonont rotifer Brachionus koreanus has been widely used for ecology, ecotoxicology, and evolution, thus, providing the whole genome data of B. koreanus is important for further understandings of in-depth molecular mechanisms. In this study, the completed assembly and characterization of the B. koreanus genome resulted in a total length of 85.7 Mb with 14,975 annotated genes. The final number of scaffolds was 567 with an N50 value and a GC content of 1.86 Mb and 24.35 %, respectively. Based on the fully constructed genome database, a total of 24 CYPs, 23 GSTs, two SODs, and a single CAT genes were identified and analyzed antioxidant activities (CAT, SOD, and GST), and transcriptional regulation of the entire CYPs, GSTs, SODs, and CAT in response to 2-ethyl-phenanthrene (2-ethyl-PHE) and piperonyl butoxide (PBO), to demonstrate the usefulness of the whole genome library of B. koreanus in response xenobiotic-induced oxidative stress. The assembled B. koreanus genome will provide a better understanding on the molecular ecotoxicology in the view of molecular mechanisms underlying toxicological responses, particularly on xenobiotic detoxification processes in the rotifer B. koreanus.

Influence of living in a multicat household on health and behaviour in a cohort of cats from the United Kingdom

BackgroundLiving in a multicat household has been implicated as a risk factor for various feline issues, but evidence is often anecdotal or based on retrospective studies.MethodsData from the Bristol Cats...

Unviable feral cat population results in eradication success on Wedge Island, Tasmania

Wedge Island in southeast Tasmania is 43 ha in size and is habitat for Little Penguin (Eudyptula minor) and Short-tailed Shearwater (Ardenna tenuirostris) populations. The island was subject to a feral Cat (Felis catus) eradication attempt in 2003 when 13 cats were captured with the assistance of trained detection dogs. It was known at least one cat remained. No further cats were captured during two subsequent visits in 2003 and 2004 and a single dead cat was found in 2012. It appeared the cat population never recovered from the initial knockdown and this ultimately resulted in eradication success. Methods used and details of cats caught are provided and the program is discussed in terms of criteria required for a successful eradication.

A TAC3 Missense Variant in a Domestic Shorthair Cat with Testicular Hypoplasia and Persistent Primary Dentition

A single male domestic shorthair cat that did not complete puberty was reported. At four years of age, it still had primary dentition, testicular hypoplasia, and was relatively small for its age. We hypothesized that the phenotype might have been due to an inherited form of hypogonadotropic hypogonadism (HH). We sequenced the genome of the affected cat and compared the data to 38 genomes from control cats. A search for private variants in 40 candidate genes associated with human HH revealed a single protein-changing variant in the affected cat. It was located in the TAC3 gene encoding tachykinin 3, a precursor protein of the signaling molecule neurokinin B, which is known to play a role in sexual development. TAC3 variants have been reported in human patients with HH. The identified feline variant, TAC3:c.220G>A or p.(Val74Met), affects a moderately conserved region of the precursor protein, 11 residues away from the mature neurokinin B sequence. The affected cat was homozygous for the mutant allele. In a cohort of 171 randomly sampled cats, 169 were homozygous for the wildtype allele and 2 were heterozygous. These data tentatively suggest that the identified TAC3 variant might have caused the suppression of puberty in the affected cat.

Efficacy of three consecutive monthly doses of a topical formulation of selamectin and sarolaner (Revolution® Plus/Stronghold® Plus) compared with a single dose of fluralaner (Bravecto® for Cats) against induced infestations of Ctenocephalides felis on cats

In a controlled laboratory study, the efficacy against fleas, Ctenocephalides felis, of a single treatment of fluralaner topical solution (Bravecto® for Cats, Merck) was compared with that of three consecutive monthly topical treatments with selamectin and sarolaner (Revolution® Plus, Zoetis). Twenty-four domestic short hair cats were ranked based on host suitability flea counts to form groups of three and were randomly assigned within group to one of three treatments. The first group received a topical treatment with (a) placebo (vehicle control for Revolution® Plus) on Days 0, 30, and 60, (b) 6 mg/kg selamectin and 1 mg/kg sarolaner on Days 0, 30, and 60, or (c) 40 mg/kg fluralaner on Day 0 and placebo (vehicle control for Revolution® Plus) on Days 30 and 60. Because doses were rounded off, the selamectin plus sarolaner-treated cats received effective dosages of 5.25–6.60 mg/kg selamectin and 0.88–1.10 mg/kg sarolaner, while the fluralaner-treated cats received dosages of 34.71–43.08 mg/kg fluralaner. All cats were infested with 100 (±5) fleas on Day -1 and at biweekly intervals after that, from Day 13 to Day 89. Flea comb counts were conducted 24 hours after treatment or after re-infestation.There were no adverse events related to treatment during the study. Except for a single cat from which 20 fleas were recovered on Day 90, all other placebo-treated cats had at least 48 fleas at each count, indicating adequacy of infestation of the controls. Based on geometric mean live flea counts, three consecutive monthly treatments with Revolution® Plus resulted in consistent and high efficacy of ≥98.6% compared with placebo throughout the study. A single treatment with Bravecto® for Cats provided consistent and high efficacy of ≥94.6% on all count days during a period of 12 weeks, the approved duration of efficacy for the product. Based on the efficacy results of the study, both products were equivalent in their ability to control fleas on cats. Use of Bravecto® for Cats every 12 weeks or the consecutive monthly use of Revolution® Plus is expected to provide extended high residual kill over the respective labeled durations of efficacy of the two products.

Many, but one

The problem of the many threatens to show that, in general, there are far more ordinary objects than you might have thought. I present and motivate a solution to this problem using many-one identity. According to this solution, the many things that seem to have what it takes to be, say, a cat, are collectively identical to that single cat.

Differential responses of stressful elements to predatory exposure in behavior-lateralized mice

BackgroundPredatory stress as a psychological stressor can elicit the activation of the hypothalamic–pituitary–adrenal (HPA) axis, which is involved in the dialogue of the neuroimmunoendocrine network. The brain has been proven to regulate the activity of the HPA axis by way of lateralization. In the present study, we probed the pivotal elements of the HPA circuitry including CRH, GR and a multifunctional cytokine in behavior-lateralized mice to determine their changes when the animals were subjected to predator exposure.MethodsBehavior-lateralized mice were classified into left-pawed and right-pawed mice through a paw-preference test. Thereafter, mice in the acute stress group received a single 60-min cat exposure, and mice in the chronic group received daily 60-min cat exposure for 14 consecutive days. The plasma CS and TNF-α were determined by ELISA, the hypothalamic CRH mRNA and hippocampal GR mRNA were detected by real-time PCR, and the hippocampal GR protein was detected by western blot analysis.ResultsThe results revealed that the levels of plasma CS were significantly elevated after chronic predatory exposure in both right-pawed and left-pawed mice; the right-pawed mice exhibited a higher plasma CS level than the left-pawed mice. Similarly, the acute or chronic cat exposure could induce the release of plasma TNF-α, and the left-pawed mice tended to show a higher level after the acute stress. Chronic stress significantly upregulated the expression of hypothalamic CRH mRNA in both left-pawed and right-pawed mice. Normally, the left-pawed mice exhibited a higher GR expression in the hippocampus than the right-pawed mice. After the cat exposure, the expression of GR in both left-pawed and right-pawed mice was revealed to be greatly downregulated.ConclusionOur findings indicate that predatory stress can invoke a differential response of stressful elements in behavior-lateralized mice. Some of these responses shaped by behavioral lateralization might be helpful for facilitating adaption to various stimuli.

The Effect of Quality of Salts Solution on Adsorption and Release of Phosphorus from Soil

A lab experiment has been carried out using a low content of lime soil treated with saline solutions of chlorides of calcium, magnesium, and sodium, and different rates 100/0, 50/50, and 0/100 of calcium, magnesium, and sodium applied on one concentration of 50 meq.l-1. Phosphorus is added in five concentrations (0, 25, 50, 75, and 100) ppm. Treatments were lab incubated for 90 days, then desorption isotherms of phosphorus are studied through Langmuir equation applications. Released phosphorus is studied. Results show an increase in the average of bonding energy in the treatment of single cat ion where it is (1, 0.68, 0.75) ml.µgP-1 of Ca, Mg, and Na treatments respectively. Also, bonding energy average of mixed cat ions (0.34, 0.20, 0.55) ml.µgP-1 of Ca/Mg, Mg/Na, and Ca/Na treatments of 50/50 rate where the maximum adsorption average are (Xm) at (4000., 188.4, 3030 .) µgP.gm Soil-1 of single cat ions of calcium, magnesium, and sodium. While when there is a pair of cat ions, they are (322, 526, 1000) µgP.gSoil-1 of Ca/Mg, Mg/Na, and Ca/Na of 50/50 rates, where the average released phosphorus of Ca, Mg, and Na are (29.1, 54.7, and 51.8)µgP.gm Soil-1 respectively, while released phosphorus of pair cat ions are (62.90, 73.90, 57.03) µgP.gm Soil-1 of Ca/Mg, Mg/Na, and Ca/Na respectively.

The Effect of Quality of Salts Solution on Adsorption and Release of Phosphorus from Soil

A lab experiment has been carried out using a low content of lime soil treated with saline solutions of chlorides of calcium, magnesium, and sodium, and different rates 100/0, 50/50, and 0/100 of calcium, magnesium, and sodium applied on one concentration of 50 meq.l-1. Phosphorus is added in five concentrations (0, 25, 50, 75, and 100) ppm. Treatments were lab incubated for 90 days, then desorption isotherms of phosphorus are studied through Langmuir equation applications. Released phosphorus is studied. Results show an increase in the average of bonding energy in the treatment of single cat ion where it is (1, 0.68, 0.75) ml.µgP-1 of Ca, Mg, and Na treatments respectively. Also, bonding energy average of mixed cat ions (0.34, 0.20, 0.55) ml.µgP-1 of Ca/Mg, Mg/Na, and Ca/Na treatments of 50/50 rate where the maximum adsorption average are (Xm) at (4000., 188.4, 3030 .) µgP.gm Soil-1 of single cat ions of calcium, magnesium, and sodium. While when there is a pair of cat ions, they are (322, 526, 1000) µgP.gSoil-1 of Ca/Mg, Mg/Na, and Ca/Na of 50/50 rates, where the average released phosphorus of Ca, Mg, and Na are (29.1, 54.7, and 51.8)µgP.gm Soil-1 respectively, while released phosphorus of pair cat ions are (62.90, 73.90, 57.03) µgP.gm Soil-1 of Ca/Mg, Mg/Na, and Ca/Na respectively.

Enlargement of optical Schrödinger's cat states

Superpositions of macroscopically distinct quantum states, introduced in Schroedinger's famous Gedankenexperiment, are an epitome of quantum "strangeness" and a natural tool for determining the validity limits of quantum physics. The optical incarnation of Schroedinger's cat - the superposition of two opposite-amplitude coherent states - is also the backbone of quantum information processing in the continuous-variable domain. However, existing preparation methods limit the amplitudes of the component coherent states by about 2, which curtails the state's usefulness for fundamental and practical applications. Here we produce higher-amplitude optical Schroedinger's cats from two such states of lower amplitudes. The protocol consists in bringing the initial states into interference on a beamsplitter and a subsequent heralding quadrature measurement in one of the output channels. In the experiment, we convert a pair of negative squeezed Schroedinger's cat states of amplitude 1.25 to a single positive Schroedinger's cat of amplitude 2.15 with success probability of ~0.2. This amplitude is comparable to the highest values obtained for this state in any physical system. Our technique can be realized in an iterative manner, in principle allowing creation of Schroedinger's cat states of arbitrarily high amplitude.

Cross-sectional quantitative RT-PCR study of feline coronavirus viremia and replication in peripheral blood of healthy shelter cats in Southern California.

Objectives The objectives of this study were to determine the prevalence of feline coronavirus (FCoV) viremia, and its replication in peripheral blood using quantitative RT-PCR (qRT-PCR) methodology in a population of 205 healthy shelter cats in Southern California, as well as to assess any possible connection to longitudinal development of feline infectious peritonitis (FIP). Methods The study was performed on buffy-coat samples from EDTA-anticoagulated whole blood samples of 205 healthy shelter cats. From 50 of these cats, fecal samples were also examined. FCoV genomic and subgenomic RNA in the buffy coats was amplified by a total FCoV RNA qRT-PCR. Evidence for FCoV replication in peripheral blood and feces was obtained by M gene mRNA qRT-PCR. Results Nine of 205 cats (4.4%) were viremic by the total FCoV RNA qRT-PCR, and one of these cats had evidence of peripheral FCoV blood replication by an FCoV mRNA qRT-PCR. The single cat with peripheral blood replication had a unique partial M gene sequence distinct from positive controls and previously published FCoV sequences. Neither seven of the nine viremic cats with follow-up nor the single cat with replicating FCoV with positive qRT-PCR results developed signs compatible with FIP within 6 months of sample collection. Conclusions and relevance FCoV viremia and peripheral blood replication in healthy shelter cats have a low prevalence and do not correlate with later development of FIP in this study population, but larger case-control studies evaluating the prognostic accuracy of the qRT-PCR assays are needed.

Molecular detection of Bartonella henselae in 11 Ixodes ricinus ticks extracted from a single cat

BackgroundBartonella henselae is a highly prevalent, vector-borne pathogen. Transmission to humans and animals by ticks is discussed controversially. Here, we present a case report, where eleven Ixodes ricinus ticks all harbouring B. henselae DNA were removed from one single cat.ResultsThe first feeding tick was tested positive for B. henselae DNA. The cat was also found to be seropositive for anti-B. henselae IgG antibodies (titer 1:640). Bartonella henselae was not cultivatable from cat blood. Ten more feeding ticks removed 7 months later contained also B. henselae DNA. Sequence analysis of the 16SrDNA and the 16S-23S internal transcribed spacer (ITS) region revealed 100% sequence homology between all ticks. Bartonella adhesin A (badA) and VirB/VirD4 type IV secretion system (virB) DNA were also detected in all ticks.ConclusionsOur results indicate that cats may serve as a reservoir for adult ticks to acquire B. henselae. Whether this observation implies an increased threat for human and animal health needs to be resolved.

Type B Chloramphenicol Acetyltransferases Are Responsible for Chloramphenicol Resistance in Riemerella anatipestifer, China

Riemerella anatipestifer causes serositis and septicaemia in domestic ducks, geese, and turkeys. Traditionally, the antibiotics were used to treat this disease. Currently, our understanding of R. anatipestifer susceptibility to chloramphenicol and the underlying resistance mechanism is limited. In this study, the cat gene was identified in 69/192 (36%) R. anatipestifer isolated from different regions in China, including R. anatipestifer CH-2 that has been sequenced in previous study. Sequence analysis suggested that there are two copies of cat gene in this strain. Only both two copies of the cat mutant strain showed a significant decrease in resistance to chloramphenicol, exhibiting 4 μg/ml in the minimum inhibitory concentration for this antibiotic, but not for the single cat gene deletion strains. Functional analysis of the cat gene via expression in Escherichia coli BL21 (DE3) cells and in vitro site-directed mutagenesis indicated that His79 is the main catalytic residue of CAT in R. anatipestifer. These results suggested that chloramphenicol resistance of R. anatipestifer CH-2 is mediated by the cat genes. Finally, homology analysis of types A and B CATs indicate that R. anatipestifer comprises type B3 CATs.