Roy D. Berghaus

An Experimental Model of Allergic Asthma in Cats Sensitized to House Dust Mite or Bermuda Grass Allergen

Background: Animal models are used to mimic human asthma, however, not all models replicate the major characteristics of the human disease. Spontaneous development of asthma with hallmark features similar to humans has been documented to occur with relative frequency in only one animal species, the cat. We hypothesized that we could develop an experimental model of feline asthma using clinically relevant aeroallergens identified from cases of naturally developing feline asthma, and characterize immunologic, physiologic, and pathologic changes over 1 year. Methods: House dust mite (HDMA) and Bermuda grass (BGA) allergen were selected by screening 10 privately owned pet cats with spontaneous asthma using a serum allergen-specific IgE ELISA. Parenteral sensitization and aerosol challenges were used to replicate the naturally developing disease in research cats. The asthmatic phenotype was characterized using intradermal skin testing, serum allergen-specific IgE ELISA, serum and bronchoalveolar lavage fluid (BALF) IgG and IgA ELISAs, airway hyperresponsiveness testing, BALF cytology, cytokine profiles using TaqMan PCR, and histopathologic evaluation. Results: Sensitization with HDMA or BGA in cats led to allergen-specific IgE production, allergen-specific serum and BALF IgG and IgA production, airway hyperreactivity, airway eosinophilia, an acute T helper 2 cytokine profile in peripheral blood mononuclear cells and BALF cells, and histologic evidence of airway remodeling. Conclusions: Using clinically relevant aeroallergens to sensitize and challenge the cat provides an additional animal model to study the immunopathophysiologic mechanisms of allergic asthma. Chronic exposure to allergen in the cat leads to a variety of immunologic, physiologic, and pathologic changes that mimic the features seen in human asthma.

Infectious and Lethal Doses of H5N1 Highly Pathogenic Avian Influenza Virus for House Sparrows (Passer Domesticus) and Rock Pigeons (Columbia Livia)

Terrestrial wild birds commonly associated with poultry farms have the potential to contribute to the spread of H5N1 highly pathogenic avian influenza (HPAI) virus within or between poultry facilities or between domesticated and wild bird populations. This potential, however, varies between species and is dependent on several virus and host factors, including habitat utilization, susceptibility, and viral shedding patterns. To provide data on susceptibility and shedding patterns of house sparrows (Passer domesticus) and rock pigeons (Columba livia), 20 birds from each species were inoculated with decreasing concentrations of A/whooper swan/Mongolia/244/05 (H5N1) HPAI virus, and the birds were evaluated for morbidity, mortality, viral shedding, and seroconversion over a 14-day trial. The house sparrows were highly susceptible to the H5N1 HPAI virus as evidenced by low infectious and lethal viral doses. In addition, house sparrows excreted virus via the oropharynx and cloaca for several days prior to the onset of clinical signs. Based on these results, house sparrows could play a role in the dissemination of H5N1 HPAI virus in poultry. In contrast, pigeons were resistant to the HPAI virus, requiring a high concentration of virus to produce infection or death. When infection did occur, the duration of viral shedding was brief, and viral titers were low. The data suggests that pigeons would contribute little to the transmission and spread of H5N1 HPAI virus in poultry.

Evaluation of Chlamydophila psittaci infection and other risk factors for atherosclerosis in pet psittacine birds

OBJECTIVEnTo determine whether the presence of Chlamydophila psittaci antigen, plasma cholesterol concentration, diet, sex, species, and age are risk factors for the development of atherosclerosis in pet psittacine birds.nnnDESIGNnRetrospective case-control study.nnnANIMALSn31 psittacine birds with atherosclerosis (study birds) and 31 psittacine birds without atherosclerosis (control birds).nnnPROCEDURESnNecropsy reports were reviewed, birds with a histopathologic diagnosis of atherosclerosis were identified, and available medical records were reviewed. Signalment, history, clinicopathologic findings, and other relevant data were recorded and evaluated. Control birds did not have atherosclerosis and were chosen by both convenience sampling and population demographics. Histologic sections of great vessels from all birds (study and control birds) were reviewed and then submitted for immunohistochemical staining for the presence of C psittaci antigen.nnnRESULTSnResult of immunohistochemical staining for C psittaci antigen in blood vessels was significantly associated with atherosclerosis. After adjusting for age, species origin, and type of illness, the odds of atherosclerosis was 7 times as high for birds with positive immunohistochemical staining for C psittaci antigen, compared with that of birds with negative immunohistochemical staining. Study birds and control birds differed significantly only with respect to plasma cholesterol concentrations. The median plasma cholesterol concentration of study birds (421 mg/dL) was significantly higher than that of control birds (223 mg/dL).nnnCONCLUSIONS AND CLINICAL RELEVANCEnInfection with C psittaci and a high plasma cholesterol concentration may be risk factors for developing atherosclerosis in pet psittacine birds.

Genetic Variability of Cytauxzoon Felis from 88 Infected Domestic Cats in Arkansas and Georgia

Although cytauxzoonosis has historically been nearly 100% fatal in domestic cats, increasing number of reports of infected cats that demonstrate less-severe disease suggest the existence of different strains of Cytauxzoon felis. To test this hypothesis, the genetic variability of C. felis was examined in blood samples from naturally infected domestic cats from Arkansas and Georgia by using the first and second ribosomal internal transcribed spacer regions (ITS1, ITS2) as markers to assess genotypic variability. In addition, the clinical outcome of infection (survival vs. fatal disease) was analyzed. Within the C. felis ITS1 region, there were a total of 8 single nucleotide polymorphisms (SNP) and a single nucleotide insertion. Within the ITS2 region, there were a total of 4 SNPs and a single 40 base pair insertion. When taken together, the ITS1 and ITS2 sequence data defined a total of 11 different sequences and 3 unique genotypes. One unique ITS1-ITS2 genotype was detected in samples submitted exclusively from Arkansas, and a second unique genotype was submitted exclusively from Georgia. There was a significant association between infection with C. felis that contained particular ITS genotypes and survival of the infected domestic cat. The identification of unique C. felis genotypes obtained from different geographic areas and the association of particular ITS genotypes with the outcome of infection suggest the existence of parasite strains that may vary in pathogenicity to the domestic cat and offer an explanation for the survival of some infected cats in more recent case studies.

Intestinal excretion of a wild bird-origin H3N8 low pathogenic avian influenza virus in mallards (Anas Platyrhynchos).

Mallards (Anas platyrhynchos) and other dabbling ducks in the genus Anas are an important component of the wild bird reservoir for avian influenza (AI) virus; these viruses are maintained in migratory duck populations through a fecal-oral transmission route. We provide a detailed characterization of intestinal viral shedding in Mallards infected with a wild bird-origin low pathogenic (LP) AI virus. Five of eight, 1-mo-old Mallards inoculated with a high dose of an H3N8 LP AI virus became infected as determined by reisolation and seroconversion. Infected birds excreted high concentrations of virus for up to 14 days postinoculation (DPI) without exhibiting overt clinical signs of disease. The pattern of viral shedding was relatively consistent between individual birds, with peak shedding on 2–3 DPI and a progressive decline over the remainder of infection. Detection of viral shedding varied depending on sample type (excrement sample or cloacal swab) and diagnostic test (virus isolation or real-time quantitative reverse transcription polymerase chain reaction). Our data provide detailed insights into the intestinal excretion of an H3N8 LP AI virus in Mallards and the performance of diagnostic assays commonly used in wild bird surveillance. Such information is valuable for estimating potential risks for spillover of LP AI viruses from Mallards to domestic animals, developing accurate transmission models for Mallard populations and facilitating the interpretation and comparison of surveillance results from different studies.

Inhaled Flunisolide Suppresses the Hypothalamic‐Pituitary‐Adrenocortical Axis, but Has Minimal Systemic Immune Effects in Healthy Cats

Feline bronchial disease is commonly treated with oral glucocorticoids (OGC), which might be contraindicated in cats with certain infectious, endocrine, renal, or cardiac diseases. Inhalant GC (IGC) maximize local efficacy and minimize systemic bioavailability. We evaluated systemic endocrine and immune effects of IGC (flunisolide, 250 microg/puff q12h) versus OGC (prednisone, 10 mg/d PO) and placebo. Six healthy cats received each drug for 2 weeks followed by a 1-month washout. Testing included determination of single early morning cortisol concentration, results of ACTH stimulation, the urine cortisol-to-creatinine ratio (UC: Cr), lymphocyte phenotype, lymphocyte blastogenesis, serum total IgA and IgM concentrations, and cytokine profiles. Significant differences between treatments were not apparent for serum immunoglobulin concentrations, or expression (mRNA) for the cytokines, interleukin (IL-) 2, IL-4, and IL-10, or gamma interferon. Single early morning cortisol concentration was lower for IGC (0.68 - 0.74 microg/dL), compared with that associated with placebo (2.82 +/- 1.94 microg/dL; P = .033). The ACTH-stimulated peak cortisol concentrations were lower after treatment in cats receiving IGC (before, 8.5 +/- 50.2 microg/dL; after, 2.9 +/- 3.3 microg/dL, P = .0004), but not OGC (before, 8.0 +/- 6.1 microg/dL; after, 6.0 +/- 4.5 microg/dL, P = .07). Similarly, UC: Cr (0.8 +/- 0.8) before IGC was lower than the value (5.02 +/- 3.62; P = .019) after IGC. Compared with placebo, cats given OGC, but not IGC, had significantly lower total percentages of T and B cells. Lymphocyte proliferation was decreased in cats receiving OGC, but not IGC, in comparison with placebo (6.9 +/- 3.3; 24.0 +/- 6.5; 18.8 +/- 14.0, respectively). Significantly more IL-10 mRNA transcription was detected in cats administered OGC or IGC, compared with placebo. Although IGC suppress the hypothalamic-pituitary-adrenocortical axis, IGC had minimal effects on the systemic adaptive immune system.

Allergen-specific IgG and IgA in serum and bronchoalveolar lavage fluid in a model of experimental feline asthma

Allergic asthma, a Th2 cell driven response to inhaled allergens, has classically been thought of as predominantly mediated by IgE antibodies. To investigate the role of other immunoglobulin classes (e.g., IgG and IgA) in the immunopathogenesis of allergic asthma, levels of these allergen-specific immunoglobulins were measured in serum and mucosal fluids. Bermuda grass allergen (BGA)-specific IgG and IgA ELISAs in serum and bronchoalveolar lavage fluid (BALF) were developed and optimized in an experimental model of BGA-induced feline asthma. Levels of BGA-specific IgG and IgA significantly increased over time in serum and BALF after allergen sensitization. Additionally, these elevated levels of BGA-specific IgG and IgA were seen in conjunction with the development of an asthmatic phenotype indicated by positive intradermal skin tests, enhanced airways hyperreactivity, and increased eosinophil percentages in the BALF.

Risk factors for colic in equids hospitalized for ocular disease

OBJECTIVEnTo evaluate the incidence of colic and risk factors for colic in equids hospitalized for ocular disease.nnnDESIGNnRetrospective observational study. Animals-337 equids (317 horses, 19 ponies, and 1 donkey) hospitalized for ocular disease.nnnPROCEDURESnMedical records of equids hospitalized for > 24 hours for treatment of ocular disease between January 1997 and December 2008 were reviewed. Information from only the first hospitalization was used for equids that were hospitalized for ocular disease on more than 1 occasion. Information gathered included the signalment, the type of ocular lesion and the treatment administered, and any colic signs recorded during hospitalization as well as the severity, presumptive diagnosis, and treatment of the colic. Statistical analysis was used to identify any risk factors for colic in equids hospitalized for ocular disease.nnnRESULTSn72 of 337 (21.4%) equids hospitalized for ocular disease had signs of colic during hospitalization. Most equids (59.7% [43/72]) had mild signs of colic, and most (87.5% [63/72]) were treated medically. Ten of 72 (13.9%) equids with colic had a cecal impaction. Risk factors for colic in equids hospitalized for ocular disease were age (0 to 1 year and ≥ 21 years) and an increased duration of hospitalization (≥ 8 days).nnnCONCLUSIONS AND CLINICAL RELEVANCEnThere was a high incidence of colic in equids hospitalized with ocular disease in this study. Findings from this study may help identify equids at risk for development of colic and thereby help direct implementation of prophylactic measures.

Production of polyclonal antisera against feline immunoglobulin E and its use in an ELISA in cats with experimentally induced asthma

Serum samples from six cats with experimentally induced asthma were used to purify feline IgE using gel filtration and affinity chromatography. The resultant IgE, evaluated for purity by immunoelectrophoresis (IEP) and reactivity by Prausnitz-Kustner (PK) testing, was used to develop polyclonal rabbit anti-feline IgE antisera. Using reverse cutaneous anaphylaxis (RCA), the antisera were determined to be specific for feline IgE. The polyclonal rabbit anti-feline IgE antiserum was then validated in an allergen-specific ELISA. Serum samples from an additional five asthmatic cats sensitized with Bermuda grass allergen (BGA) were evaluated prior to sensitization, after parenteral sensitization, and after aerosol sensitization and challenge. A significant increase in serum BGA-specific IgE was noted over time.

Effect of calf age and administration route of initial multivalent modified-live virus vaccine on humoral and cell-mediated immune responses following subsequent administration of a booster vaccination at weaning in beef calves

OBJECTIVEnTo compare immune responses following modified-live virus (MLV) vaccination at weaning after intranasal or SC administration of an MLV vaccine to beef calves at 2 or 70 days of age.nnnANIMALSn184 calves.nnnPROCEDURESnCalves were allocated to 1 of 5 groups. The IN2 (n = 37) and IN70 (37) groups received an MLV vaccine containing bovine herpesvirus 1 (BHV1), bovine viral diarrhea virus (BVDV) types 1 and 2, bovine respiratory syncytial virus (BRSV), and parainfluenza 3 virus intranasally and a Mannheimia haemolytica and Pasteurella multocida bacterin SC at median ages of 2 and 70 days, respectively. The SC2 (n = 36) and SC70 (37) groups received a 7-way MLV vaccine containing BHV1, BVDV1, BVDV2, BRSV, parainfluenza 3 virus, M haemolytica, and P multocida SC at median ages of 2 and 70 days, respectively; the control group (37) remained unvaccinated until weaning. All calves received the 7-way MLV vaccine SC at median ages of 217 (weaning) and 231 days. Serum neutralizing antibody (SNA) titers against BHV1, BVDV1, and BRSV and intranasal IgA concentrations were determined at median ages of 2, 70, 140, 217, and 262 days. Cell-mediated immunity (CMI) against BHV1, BRSV, BVDV1, and P multocida was determined for 16 calves/group.nnnRESULTSnAt median ages of 140 and 217 days, BVDV1 SNA titers were significantly higher for the SC70 group than those for the other groups. Intranasal IgA concentrations and CMI increased over time for all groups. Vaccination at weaning increased SNA titers and CMI in all groups.nnnCONCLUSIONS AND CLINICAL RELEVANCEnSC administration of an MLV vaccine to 70-day-old calves significantly increased BVDV1 antibody titers before weaning.