Local pulmonary immune responses in domestic cats naturally infected with Cytauxzoon felis

Cytauxzoonosis is a hemoprotozoal disease of cats and wild felids in the South and Southeastern United States caused by Cytauxzoon felis. Although the causative agent has been recognized since the seventies, no study has examined the local immune response in affected organs, such as the lung, and compared them to the lungs of uninfected domestic cats. Previous studies have suggested that the histopathologic findings in the lungs of C. felis-infected cats are caused by the release of pro-inflammatory mediators, such as cytokines and increased production of inducible nitric oxide synthase (iNOS), by the infected macrophages. Our laboratory had previously found an upregulation of the adhesion molecule CD18, which can stimulate the release of these pro-inflammatory mediators. The objective of this study was to characterize local pulmonary immune responses in cats naturally infected with C. felis. Immunohistochemistry was performed to detect tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, iNOS, and major histocompatibility complex (MHC) II in 19 lungs from affected cats that died between 2005 and 2013. Results showed increased expression of all of these molecules when compared to lungs from uninfected, healthy cats. Furthermore, MHC II is expressed in the endothelium of C. felis naturally infected cats. These results support that there is a marked, local, pro-inflammatory immune response that can contribute to the pathogenesis of cytauxzoonosis in the lungs.     

Experimental transmission of Cytauxzoon felis from bobcats (Lynx rufus) to domestic cats (Felis domesticus)

Freshly collected blood and/or spleen homogenate from an experimentally infected Florida bobcat (Lynx rufus floridanus), which had died of feline cytauxzoonosis, was inoculated into domestic cats. All inoculated cats had clinical signs of feline cytauxzoonosis and died within 2 weeks after they were inoculated. Similar material collected from an eastern bobcat (Lynx rufus rufus) carrying an experimentally infected Cytauxzoon felis parasitemia was inoculated into domestic cats. All inoculated cats developed a parasitemia, but none developed clinical signs of disease and none died of the disease. Cats subinoculated with parasitemic cat blood also developed parasitemias and they too did not develop clinical signs of infection nor died. After carrying the blood phase of Cytauxzoon felis for various periods, the domestic cats were then challenge exposed with proven lethal Cytauxzoon inoculum of domestic cat origin. All cats died of cytauxzoonosis.     

Cytauxzoon felis infections are present in bobcats (Lynx rufus) in a region where cytauxzoonosis is not recognized in domestic cats

This study was performed to determine the prevalence of Cytauxzoon felis (C. felis) infections in bobcats (Lynx rufus) from a region where C. felis is recognized in domestic cats, North Carolina (NC), and a region where C. felis is not recognized in domestic cats, Pennsylvania (PA). Samples from NC (n=32) were obtained post-mortem via cardiac puncture from legally trapped bobcats. Samples from PA (n=70) were collected post-mortem onto Nobuto blood collecting strips by the PA Game Commission. Each sample was tested using a C. felis specific PCR assay as well as a PCR assay targeting host DNA to rule out the presence of PCR inhibitors. Three samples were excluded due to the presence of PCR inhibitors. Thirty-three percent (10/30) of the samples from NC and 7% (5/69) of the samples from PA tested positive for the presence of C. felis. The proportion of C. felis positive bobcats from NC was significantly different than that from PA (P<0.005). Despite the lower prevalence of C. felis infections in bobcats from PA this finding is unique and indicates the potential for C. felis infections in domestic cats in the northeastern USA if the appropriate tick vectors are present. Veterinary practitioners in PA should be on alert for cytauxzoonosis in domestic cats. Further studies about the epidemiology and transmission of C. felis infections among both domestic cats and bobcats are needed.     

Detection of persistent Cytauxzoon felis infection by polymerase chain reaction in three asymptomatic domestic cats

Repeated polymerase chain reaction (PCR) testing of 3 asymptomatic domestic cats were positive for Cytauxzoon felis DNA, suggesting persistent infection. Two cats initially presented with clinical signs consistent with acute cytauxzoonosis and, in both cases, signs of illness resolved after treatment. Parasitemia was detected in peripheral blood smears from these cats upon presentation with illness and, at subsequent follow-up appointments, in the absence of clinical illness. Polymerase chain reaction analysis was positive for C. felis from blood sampled at each time point. A third cat, a housemate of a cat fatally infected with C. felis, was preventatively treated for infection at the time of the housemate cat's death. This contact cat, having never shown signs of clinical illness consistent with cytauxzoonosis infection, had no detectable parasitemia but was positive for C. felis on repeated PCR testing. Detection of asymptomatically infected cats allows for the possibility of a yet unrecognized population of infected domestic cats that may have the capacity to serve as an additional reservoir host for C. felis, altering the currently accepted paradigm of C. felis transmission to domestic cats through bobcats as the reservoir host. In cases of very low parasitemia, more sensitive means of parasite detection, such as PCR testing, may be necessary to detect infected cats. Increased detection of asymptomatically infected cats will aid in understanding the epidemiology of C. felis infection and enhance the ability to prevent this highly fatal infectious disease of domestic cats.     

Experimental infection of domestic cats (Felis domesticus) with Cytauxzoon manul from Pallas' cats (Otocolobus manul)

In a random, blind study, six domestic cats were assigned to two treatment groups that received either sterile water or dexamethasone by subcutaneous injection prior to intravenous inoculation with Pallas' cat (Otocolobus manul) blood infected with Cytauxzoon manul. A seventh domestic cat served as a control and was inoculated only with sterile water. Cats were monitored for clinical signs consistent with cytauxzoonosis, and periodically screened for hemoparasitemia. All domestic cats (6/6) that received Pallas' cat blood infected with C. manul developed a low but detectible parasitemia by 9 days post-inoculation, yet remained clinically healthy. All domestic cats (7/7) were subsequently challenged with Cytauxzoon felis and developed clinical signs typical of cytauxzoonosis within 5 days post-challenge. Affected animals were euthanized and cytauxzoonosis was confirmed by histopathology. While inoculation of domestic cats with Pallas' cat blood infected with C. manul induced a parasitemia, it did not cause disease or provide protection against challenge with C. felis. Further studies are warranted to determine the potential for interspecies transmission and disease with C. manul.     

Detection of antibodies to Francisella tularensis in cats

Blood samples were obtained from privately owned cats in Connecticut and New York State, USA in 1985-1990, and analyzed for evidence of Francisella tularensis, the etiologic agent of tularemia. Of the 91 sera tested by microagglutination (MA) methods, 11 (12%) contained antibodies to F. tularensis. Analyses of the same sera by indirect fluorescent antibody (IFA) staining methods revealed 22 (24%) positives. There was good agreement in results of both tests (73% concordance). However, we measured higher titers (1:80 to 1:640) with IFA analysis than by MA methods (1:80 to 1:160). Both tests were suitable for general screening purposes. The DNA of F.tularensis was not detected in the 24 antibody-positive sera tested. Cats living in Connecticut and New York State were naturally exposed to F.tularensis or a closely related organism. With exposure to ticks, other biting arthropods, mice, and rabbits, cats are at risk for acquiring F.tularensis infections and can be an important source of information on the presence of this agent in nature.     

Detection of specific antibodies in dogs infected with Angiostrongylus vasorum

Canine angiostrongylosis, caused by the nematode Angiostrongylus vasorum, is an emerging cardiopulmonary disease in Europe which can be fatal if left untreated. We determined the diagnostic value of the specific detection of antibodies against A. vasorum adult somatic antigen, adult excretory/secretory (E/S) antigen and first stage larvae (L1) somatic antigen in ELISAs. Also, A. vasorum adult somatic antigen purified by monoclonal antibodies (mAb) was evaluated in a sandwich-ELISA. Among the crude antigens, the best sensitivities when testing 21 naturally infected dogs were obtained using adult E/S and somatic antigen (85.7% and 76.2%, respectively), which were comparable with the results of the sandwich-ELISA based on mAb-purified antigens (81%). The ELISA performed with L1 antigen had the lowest sensitivity (42.9%). In experimentally inoculated dogs, the sensitivities ranged from 97.7% to 100% with all test settings. The specificity was 98.8% (92.5-99.9%, 95% CI) with all ELISAs using sera of 82 randomly selected dogs. Cross-reactions using adult somatic, adult E/S and L1 somatic antigen were observed in sera of dogs infected with Crenosoma vulpis, Dirofilaria immitis, Dirofilaria repens, and Eucoleus aerophilus. In contrast, using the mAb-purified antigens, the cross-reactions were minimal. Depending on the antigens used, specific antibodies were detected starting between 13 and 21 days post experimental inoculation (dpi), and at latest between 35 and 48 dpi, thus before or around the onset of patency. The serological follow-up of four A. vasorum-infected dogs after anthelmintic treatment at 88 dpi showed a decrease of antibody levels after drug administration, and the animals became seronegative 2-9 weeks later. Two untreated dogs remained seropositive. In four dogs treated 4 dpi, virtually no antibody-reaction was detectable, with the exception of the ELISA performed with L1 antigen. The early detection of specific antibodies against A. vasorum by ELISA represents a valid alternative for a reliable diagnosis and for follow-up investigations after anthelmintic treatment.     

Lack of evidence for perinatal transmission of Cytauxzoon felis in domestic cats

Cytauxzoon felis is a hemoprotozoan parasite of cats capable of causing severe, often fatal disease during acute infection, but cats that survive the acute stage of disease become chronic carriers. These otherwise healthy carriers are capable of transmitting the infection to other cats via the bite of a vector tick. A variety of other hematoprotozoan parasites are capable of vertical transmission from mother to offspring. If this were possible for C. felis, it could be an important part of the explanation for the apparent emergence of this disease with an increased incidence in an expanding geographic area. We investigated the possibility of perinatal transmission of C. felis from chronically infected cats to their offspring. Two queens produced a total of 14 healthy kittens in three litters. All kittens tested negative for C. felis by microscopic slide review and PCR until they were adopted to private homes at approximately 12 weeks of age. While this does not rule out the possibility of perinatal transmission, it is unlikely to be a common phenomenon.     

Detection of feline herpesvirus-specific antibodies and DNA in aqueous humor from cats with or without uveitis.

OBJECTIVE: To determine whether uveitis in cats was associated with intraocular production of feline herpesvirus type 1 (FHV-1)-specific antibodies or with detection of FHV-1 DNA in aqueous humor (AH). ANIMALS: 44 cats with idiopathic uveitis, 29 cats with uveitis attributed to Toxoplasma gondii infection, 13 FHV-1 seropositive cats without uveitis, and 9 FHV-1 seronegative cats without uveitis. PROCEDURE: ELISA were used to detect FHV-1-specific antibodies and total IgG antibodies in serum and AH, and the Goldmann-Witmer coefficient (C-value) for intraocular antibody production was calculated. A polymerase chain reaction assay was used to detect FHV-1 DNA in AH. RESULTS: FHV-1 seroprevalence among cats with uveitis was not significantly different from seroprevalence among cats without uveitis. Intraocular FHV-1 antibodies were never detected in cats without uveitis. Significantly more cats with idiopathic uveitis (22/44) or with toxoplasmic uveitis (11/29) had evidence of intraocular antibody production (C-value > 1) than did cats without uveitis. Only cats with idiopathic uveitis had FHV-1 C-values > 8. Among cats with evidence of intraocular antibody production, cats with idiopathic uveitis had a significantly higher median FHV-1 C-value (9.61) than did cats with toxoplasmic uveitis (2.56). Overall, FHV-1 DNA was detected in AH from 12 cats, 11 of which had uveitis. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that FHV-1 can infect intraocular tissues of cats and that intraocular FHV-1 infection may be associated with uveal inflammation in some cats.     

Detection of feline calicivirus antigens in the joints of infected cats

Twelve specific pathogen free cats were used to investigate the role of calicivirus in causing lameness. These were divided into two groups each of six cats; one group of cats had previously been vaccinated, the other had not. Three cats in each group were given live vaccine virus (F9 related) by the subcutaneous route and two in each group were challenged intranasally with field virus (A4), either four or seven days before euthanasia. The other two cats were controls. Virus was isolated from the oropharynx of five cats and the conjunctiva of a single cat. Four of these cats had been given the field virus and two the vaccine strain; the latter two cats had been previously immunised and had high circulating neutralising antibodies to calicivirus. No virus was isolated from the joints of any cat but immunofluorescence examination revealed viral antigens within the synovial macrophages of 14 joints from five cats, three having been given the field virus and two the vaccine virus seven days before euthanasia. Immunofluorescence also demonstrated the presence of immunoglobulin and complement within synovial macrophages suggesting that the virus was in the form of an immune complex. No lameness was reported in any cat and the synovial histological changes were minimal.(ABSTRACT TRUNCATED AT 250 WORDS)     

Investigation of chlamydophilosis from naturally infected cats

Background Chlamydophila felis, formerly known as Chlamydia psittaci var. felis, is frequently associated with ocular, respiratory, and occasionally reproduction tract infections. Even though the infection is sometimes asymptomatic, it potentially results in a latent immunosuppressive infection.ObjectiveThis study aimed to identify occurrences of feline chlamydophilosis, rarely reported in cats in Indonesia.MethodsThe observation was conducted in three cats with clinical signs of Cp. felis infection, particularly relapsing conjunctivitis. The cats'' histories were recorded based on owners'' information. Conjunctival swabs were sampled for cytology examination and molecular assay detection. A phylogenetic tree was generated using MEGA-X software to reveal group clustering. A post-mortem examination was performed on the cat that died during an examination.ResultsCp. felis was detected in both cytological examination and polymerase chain reaction assay. The phylogenetic tree demonstrated that the Cp. felis isolated in this study clustered with several other isolates from the other countries. Cp. felis can be isolated from cats with different clinical manifestations and levels of severity. The chronic fatal infection demonstrated interstitial broncho-pneumonia under histopathological examination.ConclusionsMolecular assay of Cp. felis is always recommended to obtain a definitive diagnosis of feline chlamydophilosis since the disease can have various clinical manifestations. Even though it may be subclinical and is often not fatal, an infected cat may be a carrier that could spread the pathogen in the surrounding environment. Serious disease management is suggested to avoid high costs associated with regularly relapsing disease.     

The detection of Cytauxzoon felis in apparently healthy free-roaming cats in the USA

Cytauxzoon felis typically causes fatal disease in domestic cats. Survival after infection and persistent parasitemia without clinical illness has been documented in a few cases. To our knowledge there are no prevalence studies of C. felis in domestic cats. The purpose of this study was to estimate the prevalence of C. felis infected cats that were presented to trap-neuter-return programs in Florida, North Carolina and Tennessee. Cats that were presented to trap-neuter-return programs were tested using a C. felis-specific PCR assay. A total of 961 domestic cats were tested (494 from Florida; 392 from North Carolina; 75 from Tennessee). Prevalence of C. felis infection in this population was 0.3%. Two cats from Florida and one cat from Tennessee tested positive for the presence of C. felis DNA. These amplicons were sequenced and confirmed to be C. felis. The cat from Tennessee was alive without evidence of illness 2 months post-surgery. The other two cats were alive 24 h post-surgery, but were then lost to follow-up. This is the first report documenting C. felis infections in free-roaming cats. Despite the low prevalence rate, the presence of apparently healthy infected free-roaming cats suggests that they may have the capacity to serve as an additional reservoir host for C. felis. Further investigations should evaluate the potential vector competence of domestic cats as well as the role of chronically infected cats in areas in which cytauxzoonosis appears hyperendemic.     

Serum proteins in normal cats and cats infected with Aelurostrongylus abstrusus

Serum proteins were evaluated by cellulose acetate electrophoresis in cats prior to and every 2 weeks for 24 weeks after oral infection with third stage larvae of Aelurostrongylus abstrusus. Evaluation of electrophoretograms was standardized by determination of electrophoretic migration ratios. Six fractions of serum proteins were consistently identified: albumin and alpha 1, alpha 2, beta 1, beta 2, and gamma globulin. Relative and absolute concentrations of each serum protein fraction were determined. The only changes found were a decrease in concentration of alpha globulins and an increase in concentration of beta 1 globulins. These changes were mild, however, so that the the concentrations for infected cats were still within 1 SD of the control concentrations. Apparently serum electrophoresis is not a useful diagnostic test for aelurostrongylosis.     

Chronic abscesses in cats associated with an organism resembling Mycoplasma

Three cats were admitted to the Ontario Veterinary College with chronic nonhealing abscesses which had not responded to a variety of local and systemic treatments.

Smears made from the purulent exudate and stained with Wright's, Giemsa's and Gram's stains did not reveal the presence of any bacteria, yeast or fungal hyphae. Bacteria could not be cultured aerobically or anaerobically but organisms resembling mycoplasmas were cultured in two cases. All cats responded to tetracycline therapy.

     

Detection of Toxoplasma gondii in the milk of experimentally infected lactating cats.

Tachyzoites of Toxoplasma gondii have been found in the milk of sheep, goats, cows and mice and infection by ingestion of raw goat milk has been documented in humans. Lactational transmission from infected cats to their kittens is suspected but the organism has not been detected in the milk. The purpose of this study was to demonstrate the presence of T. gondii in the milk of experimentally infected cats. Pregnant specific pathogen free cats were inoculated orally with T. gondii at various times prior to parturition. Feces were examined for oocyst shedding after sugar solution centrifugation. Milk was collected for polymerase chain reaction (PCR) and bioassay in mice. T. gondii was detected in the milk of five of six cats by either bioassay or PCR.     

Distribution and prevalence of Cytauxzoon felis in bobcats (Lynx rufus), the natural reservoir, and other wild felids in thirteen states

Cytauxzoon felis, a protozoan parasite of wild and domestic felids, is the causative agent of cytauxzoonosis in domestic and some exotic felids in the United States. The bobcat (Lynx rufus) is the natural reservoir for this parasite, but other felids such as Florida panthers (Puma concolor coryii) and domestic cats may maintain long-term parasitemias and serve as reservoirs. Experimentally, two tick species, Dermacentor variabilis and Amblyomma americanum, have demonstrated the ability to transmit C. felis. These two tick species have overlapping distributions throughout much of the southeastern United States. The objective of the current study was to determine the distribution and prevalence of C. felis in free-ranging bobcat populations from 13 states including California, Colorado, Florida, Georgia, Kansas, Kentucky, Missouri, North Carolina, North Dakota, Ohio, Oklahoma, South Carolina, and West Virginia. These states were selected because of differential vector presence; D. variabilis is present in each of these states except for the region of Colorado sampled and A. americanum is currently known to be present only in a subset of these states. Blood or spleen samples from 696 bobcats were tested for C. felis infection by a polymerase chain reaction (PCR) assay which targeted the first ribosomal internal transcribed spacer region (ITS-1). Significantly higher prevalences of C. felis were detected from Missouri (79%, n=39), North Carolina (63%, n=8), Oklahoma (60%, n=20), South Carolina (57%, n=7), Kentucky (55%, n=74), Florida (44%, n=45), and Kansas (27%, n=41) compared with Georgia (9%, n=159), North Dakota (2.4%, n=124), Ohio (0%, n=19), West Virginia (0%, n=37), California (0%, n=26), and Colorado (0%, n=67). In addition to bobcats, seven cougars (Puma concolor) from Georgia, Louisiana, and North Dakota and one serval (Leptailurus serval) from Louisiana were tested for C. felis. Only one cougar from Louisiana was PCR positive, which represents the first report of an infected cougar outside of the Florida panther population. These data also indicate that C. felis is present in North Dakota where infection has not been reported in domestic cats. Based on a nonparametric analysis, prevalence rates were significantly higher in states where there are established populations of A. americanum, which supports recent data on the experimental transmission of C. felis by A. americanum and the fact that domestic cat clinical cases are temporally associated with A. americanum activity. Collectively, these data confirm that bobcats are a common reservoir for C. felis and that A. americanum is likely an epidemiologically important vector.