PCR amplification of a multi-copy mitochondrial gene (cox3) improves detection of Cytauxzoon felis infection as compared to a ribosomal gene (18S)

Cytauxzoon felis is a tick-transmitted protozoan parasite that infects felids. Clinical disease caused by acute C. felis infection rapidly progresses in domestic cats, leading to high morbidity and mortality. Accurately diagnosing cytauxzoonosis as soon as possible during acute infection would allow for earlier initiation of antiprotozoal therapy which could lead to higher survival rates. Molecular detection of parasite rRNA genes (18S) by PCR has previously been shown to be a sensitive method of diagnosing C. felis infections. Based on evidence from related apicomplexan species, we hypothesized that C. felis mitochondrial genes would exist at higher copy numbers than 18S and would be a more sensitive diagnostic target. In this study we have designed a PCR assay targeting the C. felis mitochondrial gene cytochrome c oxidase subunit III (cox3). Herein we demonstrate that (1) the cox3 PCR can detect as low as 1 copy of DNA target and can detect C. felis in samples with known mitochondrial sequence heterogeneity, (2) cox3 copy number is increased relative to 18S in blood and tissue samples from acutely infected cats, and (3) the cox3 PCR is more sensitive than 18S PCR for detection of C. felis during early infections.

Cytauxzoonosis: Diagnosis and treatment of an emerging disease

PRACTICAL RELEVANCE

Cytauxzoonosis is a life-threatening hematoprotozoal disease with a rapidly progressive clinical course. Once considered a rare disease only relevant to a small geographic area, it is now recognized in more than about a third of the United States. The geographic range seems likely to increase with expansion of the range of the vector tick.

CLINICAL CHALLENGES

Both disease diagnosis and treatment offer challenges. The acute illness is often recognized by characteristic parasitic cellular inclusions, but illness may occur before parasites can be identified, and parasitic inclusions may persist long after illness has resolved. Also, while infection was once considered nearly uniformly fatal, subclinical infections are now recognized. Disease prognosis has improved for many cats through implementation of new therapies, but some pathogens are resistant to these therapies and death from disease is still common. Currently, prevention strategies are limited to ectoparasite control.

GLOBAL IMPORTANCE

Cytauxzoonosis caused by Cytauxzoon felis is limited to the Americas, and is especially problematic in southeastern and south central USA. However, other Cytauxzoon species have been recognized in Europe and Asia.

AUDIENCE

This review is aimed at veterinary practitioners and focuses on the diagnosis and treatment of cytauxzoonosis. Disease management is of crucial importance in endemic regions. Furthermore, the expanding geographic range of infection, and the possibility of parasite identification in chronically infected cats with a travel history, make understanding cytauxzoonosis relevant in non-endemic regions as well.

EVIDENCE BASE

The authors draw on evidence from prospective clinical trials, experimental infections, retrospective clinical studies and case reports, as well as their own personal experience with the diagnosis and treatment of cytauxzoonosis.

Long-term evaluation of mesenchymal stem cell therapy in a feline model of chronic allergic asthma

BACKGROUND

Mesenchymal stem cells (MSCs) decrease airway eosinophilia, airway hyperresponsiveness (AHR), and remodelling in murine models of acutely induced asthma. We hypothesized that MSCs would diminish these hallmark features in a chronic feline asthma model.

OBJECTIVE

To document effects of allogeneic, adipose-derived MSCs on airway inflammation, AHR, and remodelling over time and investigate mechanisms by which MSCs alter local and systemic immunologic responses in chronic experimental feline allergic asthma.

METHODS

Cats with chronic, experimentally induced asthma received six intravenous infusions of MSCs (0.36-2.5 × 10E7 MSCs/infusion) or placebo bimonthly at the time of study enrollment. Cats were evaluated at baseline and longitudinally for 1 year. Outcome measures included: bronchoalveolar lavage fluid cytology to assess airway eosinophilia, pulmonary mechanics and clinical scoring to assess AHR, and thoracic computed tomographic (CT) scans to assess structural changes (airway remodelling). CT scans were evaluated using a scoring system for lung attenuation (LA) and bronchial wall thickening (BWT). To assess mechanisms of MSC action, immunologic assays including allergen-specific IgE, cellular IL-10 production, and allergen-specific lymphocyte proliferation were performed.

RESULTS

There were no differences between treatment groups or over time with respect to airway eosinophilia or AHR. However, significantly lower LA and BWT scores were noted in CT images of MSC-treated animals compared to placebo-treated cats at month 8 of the study (LA P = 0.0311; BWT P = 0.0489). No differences were noted between groups in the immunologic assays.

CONCLUSIONS AND CLINICAL RELEVANCE

When administered after development of chronic allergic feline asthma, MSCs failed to reduce airway inflammation and AHR. However, repeated administration of MSCs at the start of study did reduce computed tomographic measures of airway remodelling by month 8, although the effect was not sustained at month 12. Further study of MSC therapy including repeated MSC administration is warranted to assess impact on remodelling in chronic asthma.

COMPARISON OF LUNG ATTENUATION AND HETEROGENEITY BETWEEN CATS WITH EXPERIMENTALLY INDUCED ALLERGIC ASTHMA, NATURALLY OCCURRING ASTHMA AND NORMAL CATS

Airway remodeling is a prominent feature of feline allergic asthma but requires biopsy for characterization. Computed tomography (CT) has appeal as a minimally invasive diagnostic test. The purpose of this prospective case-control study was to compare indices of airway remodeling between cats with experimentally induced, spontaneous asthma and healthy unaffected cats using CT. We hypothesized that experimental and spontaneous feline asthma would have similar CT airway remodeling characteristics and that these would be significantly different in healthy cats. Experimentally induced asthmatic research cats (n = 5), spontaneously asthmatic pet cats (n = 6), and healthy research cats (n = 5) were scanned unrestrained using a 64-detector row CT scanner. Inspiratory breath-hold CT scans were also performed in experimentally induced asthmatic and healthy cats. Mean ± extent variation of lung attenuation for each cat was determined using an airway inspector software program and CT images were scored for lung heterogeneity by a board-certified veterinary radiologist who was unaware of cat group status. Groups were compared using one-way ANOVA (unrestrained scans) and the Student's t-test (anesthetized scans) with significance defined as P < 0.10. Experimentally asthmatic and spontaneously asthmatic cats had significantly (P = 0.028 and P = 0.073, respectively) increased lung attenuation compared to healthy cats. Heterogeneity scores were higher in experimentally induced asthmatic cat than in healthy cats. Objective quantification of lung heterogeneity and lung volume did not differ among the three groups (P = 0.311, P = 0.181, respectively). Findings supported our hypothesis. Inspiratory breath-hold anesthetized CT scans facilitated discrimination between asthmatic and healthy cats in comparison to unrestrained CT scans.

Pharmacokinetics of minocycline in domestic cats

OBJECTIVES

Recently, the increased cost and decreased availability of doxycycline has sparked an interest in using minocycline as an alternative. The purpose of this study was to determine the pharmacokinetics of minocycline in domestic cats in order to facilitate dosage decisions.

METHODS

Purpose-bred, young adult cats were administered a single dose of either intravenous (IV; n = 4; 5 mg/kg) or oral (n = 6; 50 mg/cat) minocycline. Blood was collected from each at intervals up to 24 h afterwards. Minocycline was measured using high performance liquid chromatography with ultraviolet detection. A one-compartment pharmacokinetic model was fit to the oral data and a two-compartment model to the IV data via a computer program. Plasma protein binding was measured by fortifying blank plasma from untreated healthy cats with minocycline at two concentrations and applying an ultracentrifugation method.

RESULTS

Two cats became transiently lethargic and tachypneic during IV drug infusion. One cat vomited 6.0 h after infusion, and two cats vomited either 1.5 h or ~5.0 h after oral drug administration. The mean oral dose administered was 13.9 ± 0.47 mg/kg. Oral bioavailability was approximately 62%. Plasma protein binding was 60% at 5 µg/ml and 46% at 1 μg/ml. After IV administration, elimination half-life (t(½)), apparent volume of distribution at steady-state, and systemic clearance were 6.7 h (coefficient of variation [CV] 14.4%), 1.5 l/kg (CV 34.5%) and 2.9 ml/kg/min (CV 40.8%), respectively. After oral administration the terminal t(½) and peak concentration (Cmax) were 6.3 h (CV 9%) and 4.77 µg/ml (CV 36%), respectively.

CONCLUSIONS AND RELEVANCE

Because most bacteria will have a minimum inhibitory concentration of ⩽0.5 μg/ml, an oral dose of 8.8 mg/kg q24h would be adequate to meet pharmacokinetic-pharmacodynamic targets after adjusting for protein binding. Although some gastrointestinal upset may occur, one 50 mg capsule orally q24h would provide appropriate dosing for most cats.

Prevalence of Cytauxzoon felis infection in healthy cats from enzootic areas in Arkansas, Missouri, and Oklahoma

Background

Infection with Cytauxzoon felis in domestic cats can cause fever, lethargy, depression, inappetence, icterus, and often death. With a high mortality rate, cytauxzoonosis was historically considered a fatal disease. Within the last 15 years, cats with or without treatment have been recognized as chronically infected survivors of C. felis infection. Our objective was to determine the prevalence of C. felis in healthy domestic cats from Arkansas, Missouri, and Oklahoma.

Methods

Infection with C. felis was determined using DNA extracted from anticoagulated whole blood and PCR amplification using C. felis-specific primers. Chi-square, Fisher’s exact tests, and odds ratios were used to compare proportions of cats infected with C. felis.

Results

Blood samples were collected from 902 healthy domestic cats between October 2008 and April 2012. DNA from Cytauxzoon felis was detected in 56 of 902 (6.2%; 95% confidence interval, 4.7–7.9) samples. The highest prevalence of C. felis infection (15.5%; 10.3–21.7) was observed in cats from Arkansas, followed by cats from Missouri (12.9%; 6.1–24.0), and cats from Oklahoma (3.4%; 2.2–5.1). Cats sampled in Arkansas and Missouri were 5.1 and 4.2, respectively, times more likely to be chronically infected with C. felis than cats from Oklahoma.

Conclusions

Infection with C. felis is common in domestic cats through Arkansas, Missouri, and Oklahoma. The high prevalence of C. felis reported herein suggests that infected domestic cats are likely reservoirs of infection for naive felines. The high prevalence of C. felis substantiates the importance for the use of approved acaricides on cats to prevent cytauxzoonosis.

Neonatal aerosol exposure to Bermuda grass allergen prevents subsequent induction of experimental allergic feline asthma: evidence for establishing early immunologic tolerance

Allergic asthma is increasing in industrialized countries, especially in children. Rodent and human studies suggest an opportunity to "prevent" asthma in the perinatal period. The aims of this study were to create a more "natural" model of feline asthma by exposing offspring of asthmatic queens to Bermuda grass allergen (BGA) by inhalation only, and to investigate maternal-fetal-infant interactions in the development of asthma. Kittens from asthmatic queens were divided into four groups: maternal exposure to aerosolized BGA during the third trimester, neonatal exposure to aerosolized BGA in the first three months of life, both maternal and neonatal exposure, or saline control. Kittens failing to achieve an asthmatic phenotype based on bronchoalveolar lavage fluid (BALF) analysis by 6 months underwent traditional sensitization: adjuvanted allergen injection, intranasal allergen, and aerosol challenges. BALF was collected at 3, 4 and 6 months, and after sensitization at 8 months, and analyzed for eosinophil counts and BGA-specific IgG and IgA. Intradermal testing (IDT) was performed at 6 and 7 months. At six months none of the kittens had airway eosinophilia, BGA-specific IgG or IgA, and were non-responsive to IDT. After sensitization, kittens receiving neonatal aerosolization failed to develop airway eosinophilia as seen in the controls. Kittens exposed to BGA aerosols, either in-utero or neonatally, continued to lack IDT response. Chronic exposure to BGA aerosols failed to induce asthma in kittens, and instead tolerized the kittens to BGA. This is the first evidence that neonatal intervention could potentially "prevent" allergic asthma in cats.

Failure of efficacy and adverse events associated with dose-intense diminazene diaceturate treatment of chronic Cytauxzoon felis infection in five cats

Cytauxzoon felis is a hemoprotozoan parasite of cats. While many infected cats die of acute illness, some enter a chronic carrier state. To date, no treatment has been documented to clear the chronic carrier state, leaving recovered cats to act as a potential indirect source of infection via a tick vector. Diminazene diaceturate is an anti-protozoal therapy that has been suggested for use in the treatment of acute cytauxzoonosis, but which failed to clear the carrier state at the dose used in acute illness. We hypothesized that a dose-intensified regimen of diminazene could reduce or eliminate parasitemia from five domestic cats naturally infected with C felis. Cats were administered 4 mg/kg of diminazene diaceturate intramuscularly for 5 consecutive days. Clearance of the organism was assessed via semi-quantitative polymerase chain reaction and light microscopy 1, 3, 6 and 10 weeks after starting treatment. Additionally, cats were monitored for adverse drug reactions by daily observation and examination. Complete blood count, biochemical profile and urinalysis were performed at 1, 3 and 10 weeks. Adverse events were common and included profuse salivation and nausea at the time of injection, monoparesis in the injected leg, proteinuria and potential hepatotoxicity. Severity of parasitemia was not reduced. Diminazene diaceturate cannot be recommended for elimination of the carrier state of C felis infection.

A novel candidate vaccine for cytauxzoonosis inferred from comparative apicomplexan genomics

Cytauxzoonosis is an emerging infectious disease of domestic cats (Felis catus) caused by the apicomplexan protozoan parasite Cytauxzoon felis. The growing epidemic, with its high morbidity and mortality points to the need for a protective vaccine against cytauxzoonosis. Unfortunately, the causative agent has yet to be cultured continuously in vitro, rendering traditional vaccine development approaches beyond reach. Here we report the use of comparative genomics to computationally and experimentally interpret the C. felis genome to identify a novel candidate vaccine antigen for cytauxzoonosis. As a starting point we sequenced, assembled, and annotated the C. felis genome and the proteins it encodes. Whole genome alignment revealed considerable conserved synteny with other apicomplexans. In particular, alignments with the bovine parasite Theileria parva revealed that a C. felis gene, cf76, is syntenic to p67 (the leading vaccine candidate for bovine theileriosis), despite a lack of significant sequence similarity. Recombinant subdomains of cf76 were challenged with survivor-cat antiserum and found to be highly seroreactive. Comparison of eleven geographically diverse samples from the south-central and southeastern USA demonstrated 91-100% amino acid sequence identity across cf76, including a high level of conservation in an immunogenic 226 amino acid (24 kDa) carboxyl terminal domain. Using in situ hybridization, transcription of cf76 was documented in the schizogenous stage of parasite replication, the life stage that is believed to be the most important for development of a protective immune response. Collectively, these data point to identification of the first potential vaccine candidate antigen for cytauxzoonosis. Further, our bioinformatic approach emphasizes the use of comparative genomics as an accelerated path to developing vaccines against experimentally intractable pathogens.

Comparison of direct and indirect bronchoprovocation testing using ventilator-acquired pulmonary mechanics in healthy cats and cats with experimental allergic asthma

Airway hyperresponsiveness (AHR) is a key feature of asthma and can be measured using bronchoprovocation. Direct (methacholine, MCh) or indirect (adenosine-5-monophosphate, AMP; or mannitol) bronchoprovocants are used in human patients, the latter inducing AHR only with pre-existing airway inflammation. The present study compared the responses to direct (MCh) and indirect (mannitol, AMP) bronchoprovocation in healthy and asthmatic cats (n=6/group). The order of bronchoprovocant was randomized using a published table of random numbers and there was a 1-month washout before crossover to the next treatment. Pulmonary mechanics were measured in anesthetized and mechanically ventilated cats using a critical care ventilator. Saline at baseline and increasing doses of each bronchoprovocant were aerosolized for 30 s, followed by 4 min of data collection between doses. The endpoint for each bronchoprovocant was reached when airway resistance exceeded 200% of baseline values (EC200Raw). There was a significant difference (P<0.001) in the airway response of asthmatic vs. healthy cats over the range of MCh concentrations, despite there being no significant difference in the EC200Raw between the groups. Response to MCh was significantly greater (P<0.05) in asthmatic than in healthy cats at MCh concentrations as low as 0.0625 mg/mL. For AMP, a small subset of asthmatics (n=2/6) responded at low concentrations; four asthmatic cats and all healthy cats failed to respond even to the highest concentrations of AMP. One asthmatic cat but no healthy cats responded to mannitol. In conclusion, MCh discriminated asthmatic from healthy cats but neither AMP nor mannitol was an effective bronchoprovocant in this model.

Evaluation of Cytauxzoon felis infection status in captive-born wild felids housed in an area endemic for the pathogen

OBJECTIVE

To determine whether apparently healthy captive-born wild felids that were not native to North America and were housed in an area endemic for Cytauxzoon felis harbored the pathogen.

DESIGN

Prospective observational case series.

ANIMALS

11 captive-born wild felids that were (1 bobcat [Lynx rufus] and 1 cougar [Puma concolor]) or were not (1 lion [Panthera leo] and 8 tigers [Panthera tigris]) native to North America and 6 domestic cats (5 pets and 1 feral).

PROCEDURES

Blood was collected, and a PCR assay for C felis was performed. The C felis 18S rRNA gene sequence was characterized in samples that tested positive. Blood smears were evaluated microscopically for intraerythrocytic organisms consistent with C felis. Blood smears from an additional 6 feral domestic cats found dead on the study premises were also evaluated.

RESULTS

4 tigers and 6 domestic cats without clinical signs of disease tested positive for C felis infection via PCR assay; intraerythrocytic organisms consistent with C felis were identified in smears from 1 C felis-infected tiger (which also had azotemia) and in smears from 11 of 12 domestic cats. Possible erythrocytic inclusions were identified in 1 tiger that tested negative for C felis. Sequences of C felis 18S rRNA amplicons from all infected tigers shared > 99.8% identity with reported C felis sequences from North American domestic cats and were identical to amplicons from domestic cats on the premises.

CONCLUSIONS AND CLINICAL RELEVANCE

Captive tigers without clinical signs of disease tested positive for C felis. The PCR assay for C felis appeared to be more reliable than cytologic detection of piroplasms in tigers.

Oral glucocorticoids diminish the efficacy of allergen-specific immunotherapy in experimental feline asthma

Allergen-specific rush immunotherapy (RIT) shows promise in treating asthma; however, pet cats will likely require at least initial concurrent glucocorticoids (GCs) to control serious clinical signs. How the immunosuppressive effects of GCs would impact RIT in cats is unknown. The hypothesis of this study was that oral, but not inhaled GCs will diminish the efficacy of RIT in experimental feline asthma. Cats (n=6/group) were sensitized using Bermuda grass allergen (BGA) and randomized to receive BGA-specific RIT for 9 months with an oral GC (prednisolone 10mg daily), inhaled GC (fluticasone 220 μg twice daily), or placebo administered for the first 6 months. Bronchoalveolar lavage fluid (BALF) percent eosinophils and other immunological assays were performed. Eosinophilic airway inflammation was suppressed in all groups at month 6 of RIT (group mean ± SD, 5 ± 2%, 13 ± 4%, and 7 ± 2% for oral GC, inhaled GC, and placebo, respectively; P=0.291). BALF percent eosinophils significantly increased over time only in oral GC/RIT cats between months 6 and 9 (P=0.031). Placebo/RIT cats had significant decreases over time in BGA-specific serum IgE (P=0.031). Concentration of interleukin (IL)-5 in BALF significantly increased over time in inhaled GC/RIT cats (P=0.031). No significant differences were found between groups at month 6 or over time in each group for BGA-specific lymphocyte blastogenesis, percent blood T regulatory cells, or number of IL-10-producing cells. Given the significant increase of airway eosinophilia over time in RIT cats initially treated with an oral GC, inhaled GCs might be better for dampening eosinophilic inflammation until RIT normalizes the dysregulated immune system.

Nebulized lidocaine blunts airway hyper-responsiveness in experimental feline asthma

Nebulized lidocaine may be a corticosteroid-sparing drug in human asthmatics, reducing airway resistance and peripheral blood eosinophilia. We hypothesized that inhaled lidocaine would be safe in healthy and experimentally asthmatic cats, diminishing airflow limitation and eosinophilic airway inflammation in the latter population. Healthy (n = 5) and experimentally asthmatic (n = 9) research cats were administered 2 weeks of nebulized lidocaine (2 mg/kg q8h) or placebo (saline) followed by a 2-week washout and crossover to the alternate treatment. Cats were anesthetized to measure the response to inhaled methacholine (MCh) after each treatment. Placebo and doubling doses of methacholine (0.0625-32.0000 mg/ml) were delivered and results were expressed as the concentration of MCh increasing baseline airway resistance by 200% (EC200Raw). Bronchoalveolar lavage was performed after each treatment and eosinophil numbers quantified. Bronchoalveolar lavage fluid (BALF) % eosinophils and EC200Raw within groups after each treatment were compared using a paired t-test (P <0.05 significant). No adverse effects were noted. In healthy cats, lidocaine did not significantly alter BALF eosinophilia or the EC200Raw. There was no difference in %BALF eosinophils in asthmatic cats treated with lidocaine (36±10%) or placebo (33 ± 6%). However, lidocaine increased the EC200Raw compared with placebo 10 ± 2 versus 5 ± 1 mg/ml; P = 0.043). Chronic nebulized lidocaine was well-tolerated in all cats, and lidocaine did not induce airway inflammation or airway hyper-responsiveness in healthy cats. Lidocaine decreased airway response to MCh in asthmatic cats without reducing airway eosinophilia, making it unsuitable for monotherapy. However, lidocaine may serve as a novel adjunctive therapy in feline asthmatics with beneficial effects on airflow obstruction.

Potential ecological distribution of Cytauxzoon felis in domestic cats in Oklahoma, Missouri, and Arkansas

The ecological distribution of Cytauxzoon felis, an often-fatal tick-borne apicomplexan that infects domestic cats, has not been evaluated or identified despite its continued emergence. Infection of C. felis is characterized by lethargy, icterus, fever, anorexia, anemia, and death. The natural vertebrate reservoir of C. felis is the bobcat (Lynx rufus). To determine the possible distribution of C. felis in three states where infection is common (Oklahoma, Missouri, and Arkansas), two separate approaches to ecological niche modeling were implemented. First, a model relating several different climatic layers to geographic locations where cases of C. felis infection were confirmed in domestic cats was developed to predict the possible distribution of the parasite. The second model incorporated occurrences of bobcats with environmental layers and land cover suitable for tick vectors to identify areas of overlap where C. felis transmission was likely. Results of both models indicated a high probability of C. felis from central Oklahoma to south-central Missouri. However, other predicted areas of C. felis occurrence varied between the two modeling approaches. Modeling the vertebrate reservoir and the tick vector predicted a broader possible distribution compared to modeling cases of C. felis infection in domestic cats. Our results suggest that C. felis is likely to extend beyond areas predicted by case modeling due to the presence of both the vector and reservoir.

The tyrosine kinase inhibitor masitinib blunts airway inflammation and improves associated lung mechanics in a feline model of chronic allergic asthma

BACKGROUND

Blockade of tyrosine kinase signaling by masitinib, a c-kit/PDGF receptor tyrosine kinase inhibitor, can modulate allergic airway inflammation, but effects on lung mechanics have not been well characterized. We hypothesized masitinib would decrease airway eosinophilia and consequently improve pulmonary mechanics in a feline allergic asthma model.

METHODS

Asthma was induced in 12 cats using Bermuda grass allergen (BGA). Cats received 50 mg/day oral masitinib or placebo. Bronchoalveolar lavage fluid (BALF) was analyzed for eosinophils, total protein (TP) and BGA-specific IgE. Ventilator-acquired mechanics after methacholine (MCh) challenge determined MCh concentration needed to increase baseline airway resistance by 200% (EC(200)R(aw)), positive end expiratory occlusion pressure (PEEP) and end inspiratory breath hold pressure (P(plat)). An inverse correlate of respiratory system compliance P(plat)-PEEP was also calculated. Data were analyzed using the Wilcoxon test, with one-tailed significance set at p < 0.1.

RESULTS

After 4 weeks, percent eosinophils in BALF was lower in masitinib-treated cats (7 ± 9%) versus controls (30 ± 27%, p = 0.023). BALF TP significantly differed (p = 0.047) between groups, decreasing with masitinib and increasing with placebo. BALF BGA-specific IgE was unaffected by masitinib. Both groups showed an improvement in EC(200)R(aw) (masitinib, p = 0.015; control, p = 0.078) but no significant change in PEEP after 4 weeks. Masitinib-treated cats demonstrated decreased P(plat) (p = 0.033) and P(plat)-PEEP (p = 0.075) at week 4, suggesting an improvement in respiratory compliance.

CONCLUSIONS

Masitinib reduced BALF eosinophilia and TP, indicating improved airway inflammation and edema, and improved P(plat) and P(plat)-PEEP, suggesting benefit to respiratory compliance influenced by airway inflammation/edema. Masitinib deserves further study in humans with chronic allergic asthma.

Seroprevalence of Ehrlichia canis, Ehrlichia chaffeensis and Ehrlichia ewingii in dogs in North America

BACKGROUND

This study evaluated the exposure of dogs to three different Ehrlichia spp. in the south and central regions of the United States where vector-borne disease prevalence has been previously difficult to ascertain, particularly beyond the metropolitan areas.

METHODS

Dog blood samples (n = 8,662) were submitted from 14 veterinary colleges, 6 private veterinary practices and 4 diagnostic laboratories across this region. Samples were tested for E. canis, E. chaffeensis and E. ewingii specific antibodies using peptide microtiter ELISAs.

RESULTS

Overall, E. canis, E. chaffeensis and E. ewingii seroprevalence was 0.8%, 2.8%, and 5.1%, respectively. The highest E. canis seroprevalence (2.3%) was found in a region encompassing Arkansas, Louisiana, Oklahoma, Tennessee and Texas. E. chaffeensis seroreactivity was 6.6% in the central region (Arkansas, Kansas, Missouri, and Oklahoma) and 4.6% in the southeast region (Georgia, Maryland, North Carolina, South Carolina, Tennessee and Virginia). Seroreactivity to E. ewingii was also highest in the central region (14.6%) followed by the southeast region (5.9%). The geospatial pattern derived from E. chaffeensis and E. ewingii seropositive samples was similar to previous reports based on E. chaffeensis seroreactivity in white-tailed deer and the distribution of human monocytic ehrlichiosis (HME) cases reported by the CDC.

CONCLUSIONS

The results of this study provide the first large scale regional documentation of exposure to E. canis, E. chaffeensis and E. ewingii in pet dogs, highlighting regional differences in seroprevalence and providing the basis for heightened awareness of these emerging vector-borne pathogens by veterinarians and public health agencies.

Successful treatment of acute respiratory distress syndrome in 2 dogs

Acute respiratory distress syndrome (ARDS) was diagnosed in 2 dogs with acute dyspnea. Short-term positive pressure ventilation and intense critical and nursing care were provided. Both dogs improved and were discharged. Few reports describe successful recovery from ARDS. Due to advances in positive pressure ventilation and improvement in the supportive care of critically ill veterinary patients, the prognosis for ARDS may improve.

Feline respiratory disease complex

Feline respiratory disease complex (FRDC) refers to the characteristic acute presentation of a contagious respiratory or ocular disease caused by one or multiple pathogens. Environmental and host factors impact the transmission, clinical presentation, preventive strategy, and treatment of affected cats. The FRDC is especially problematic in settings where large numbers of cats cohabit, including animal shelters, catteries, and semi-feral colonies. Although elimination of FRDC is an unrealistic goal, improved understanding can lead to strategies to minimize disease impact.

The impact of oral versus inhaled glucocorticoids on allergen specific IgE testing in experimentally asthmatic cats

Glucocorticoids (GCs) are palliative for allergic asthma, but allergen-specific immunotherapy (ASIT), which relies on identification of allergens, represents a potentially curative treatment. The purpose of this study was to determine if oral or inhaled GCs would interfere with identification of sensitizing allergens. The hypothesis was that oral but not inhaled GCs would interfere with accurate allergen-specific IgE identification determined by skin and serum testing in experimentally asthmatic cats. Asthma was induced in 18 cats using Bermuda grass allergen (BGA). Cats (n=6/group) were randomized to receive oral GCs (10mg prednisolone q 24 h), inhaled GCs (600 μg budesonide q 24 h) or placebo (q 24 h PO) for one month. Intradermal skin testing (IDST) and serum BGA-specific IgE were measured prior to, during and after treatment. A paired t test was used to compare groups pre- and post-treatment (P<0.05 significant). IDST reactivity was eliminated in 4/6, 3/6, and 1/6 cats receiving oral GCs, inhaled GCs, and placebo respectively. Two weeks after stopping treatment, IDST was again positive in all cats. Serum IgE reactivity to BGA was not significantly diminished by any treatment. In conclusion, a two-week withdrawal from GCs is adequate for IDST, but may not be necessary for serum IgE testing.

Endotracheal nebulization of N-acetylcysteine increases airway resistance in cats with experimental asthma

N-acetylcysteine (NAC), a mucolytic and antioxidant, is speculated to cause bronchoconstriction in cats when delivered via aerosol. We hypothesized that in cats with experimental asthma, aerosol delivery of NAC (400mg cumulative dose) via an endotracheal tube would increase airflow limitation as measured by ventilator-acquired mechanics. After endotracheal drug delivery, airway resistance and inspiratory plateau pressure (Pplat) measurements were obtained in six mechanically ventilated asthmatic cats. Results demonstrated significantly increased airway resistance (P=0.0007) compared with aerosolized saline control; Pplats were not significantly different (P=0.059). All cats exhibited at least one adverse effect: excessive airway secretions (n=3), spontaneous cough (n=2), unilateral strabismus (n=1) and post-anesthetic death (n=1). No adverse reactions were noted with saline aerosol; cough was noted in one cat with methacholine challenge. In conclusion, airway resistance and adverse reactions were documented in all cats after NAC aerosol delivery. Further studies must be performed to evaluate if it is an effective mucolytic and/or antioxidant in cats and to determine if bronchodilator pre-treatment will negate NAC-induced bronchoconstriction.

Erythrocyte survival time in Greyhounds as assessed by use of in vivo biotinylation

OBJECTIVE

To determine erythrocyte survival time in Greyhounds.

ANIMALS

6 Greyhounds used as blood donors and 3 privately owned non-Greyhound dogs.

PROCEDURES

In vivo biotinylation of erythrocytes was performed by infusion of biotin-N-hydroxysuccinimide into each dog via a jugular vein catheter. Blood samples were collected 12 hours later and then at weekly intervals and were used to determine the percentage of biotin-labeled erythrocytes at each time point. Erythrocytes were washed, incubated with avidin-fluorescein isothiocyanate, and washed again before the percentage of biotinylated erythrocytes was measured by use of flow cytometry. Survival curves for the percentage of biotinylated erythrocytes were generated, and erythrocyte survival time was defined as the x-intercept of a least squares best-fit line for the linear portion of each curve.

RESULTS

The R2 for survival curves ranged from 0.93 to 0.99 during the first 10 weeks after infusion of erythrocytes. Erythrocyte survival time for the 3 non-Greyhound dogs was 94, 98, and 116 days, respectively, which was consistent with previously reported values. Erythrocyte survival time for the 6 Greyhounds ranged from 83 to 110 days (mean, 93 days; median, 88 days). As determined by use of in vivo biotinylation, erythrocyte survival times in Greyhounds were similar to those determined for non-Greyhound dogs and did not differ significantly from erythrocyte survival times reported previously for non-Greyhound dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

Erythrocyte survival time was similar in Greyhounds and non-Greyhound dogs. Greyhounds can be used as erythrocyte donors without concerns about inherently shorter erythrocyte survival time.

Prevalence of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus carriage in three populations

BACKGROUND

A higher prevalence of methicillin-resistant Staphylococcus aureus (MRSA) colonization is reported in healthcare workers compared with nonhealthcare workers.

HYPOTHESIS

The prevalence of MRSA colonization differed in people and pets in households with healthcare workers as compared with households without healthcare workers.

SUBJECTS

A person and 1 dog or cat from 586 households defined as either a nonhealthcare (n = 213), veterinary healthcare (n = 211), or human healthcare (n = 162) worker household.

METHODS

Prospective cross-sectional study. Samples from humans and pets were cultured in vitro. Staphylococcus aureus was identified as methicillin sensitive (MSSA) or MRSA with mecA polymerase chain reaction. Pulsed-field gel electrophoresis and spa-typing were used to characterize relatedness of S. aureus and MRSA and assign USA types.

RESULTS

The prevalence of MSSA and MRSA in humans was 21.5% (126/586) and 5.63% (33/586), respectively, and 7.85% (46/586) and 3.41% (20/586), respectively, in pets. There were no differences in prevalences of either MSSA or MRSA between household types. The proportion of MRSA among all S. aureus isolates in humans and pets was 20.8% (33/159) and 30.3% (20/66), respectively. In < 1.0% (4/586) of households, the same strain of MRSA was found in both a person and a pet.

CONCLUSIONS AND CLINICAL IMPORTANCE

There were no differences in the prevalences of MSSA or MRSA between healthcare worker and nonhealthcare worker households. Pets and people colonized with S. aureus were as likely to be colonized with MRSA. Colonization of a person and their pet with the same strain of MRSA was rare.