Determination of threshold concentrations of allergens and evaluation of two different histamine concentrations in canine intradermal testing

The purpose of this study was to determine the optimal histamine concentration and allergen threshold concentrations for canine intradermal testing. Thirty healthy dogs were tested using two different concentrations of histamine and four different concentrations of each allergen. The optimal histamine concentration was determined to be 1:10 000 w/v. The threshold concentration was at least 1750 PNU/mL for all tested grasses, weeds, trees, moulds and insects, except for fleas which was as least 1:500 w/v. For Dermatophagoides pteronyssinus, the optimal threshold concentration was 250 PNU/mL, whereas for Dermatophagoides farinae and Tyrophagus putrescentiae, it was 100 PNU/mL. Threshold concentration for all epidermals except human dander was at least 1250 PNU/mL. The optimal threshold concentration for human dander was 300 PNU/mL. Our results suggest that the currently used 1:100 000 w/v concentration of histamine and the 1000 PNU/mL concentration for most grasses, weeds, trees, moulds, epidermals and insects may not be appropriate for canine intradermal testing.     

Determination of threshold concentrations of multiple allergenic extracts for equine intradermal testing using normal horses in three seasons

Forty-one normal horses were evaluated for reactivity to intradermally injected aqueous allergens to determine allergen threshold concentrations (TC), with potential relevance to equine intradermal testing (IDT). Horses were tested three times over 1 year to assess seasonal variation in reactivity, using three to five serial dilutions of 27 allergens each time. Injection sites were evaluated after 15 min, 1 h, 4 h and 24 h. The highest allergen concentration at which < 10% of horses demonstrated positive reactivity (subjective score of > or = 2, scale of 0 to 4) at 15 min was considered the TC. The TC was determined for nine pollens (2000 to > 6000 PNU mL(-1)), four moulds (4000 to > 6000 PNU mL(-1)), seven insects (ant, horse fly 125 PNU mL(-1); house fly, cockroach 250 PNU mL(-1); moth 60 PNU mL(-1); mosquito 1000 PNU mL(-1); Culicoides nebeculosis 1 : 5000 w v(-1)) and three of four storage mites (1 : 10,000 w v(-1)). The TC was not determined due to excessive reactivity at the lowest concentrations tested for dust mites (Dermatophagoides farinae [< 1 : 12,000 w v(-1)], D. pteronyssinus [< 1 : 30,000 w v(-1)]), and Acarus siro (< 1 : 10,000 w v(-1)). Minor variation in the TC for specific allergens occurred in different seasons. Progressive sensitization with repeat testing occurred for grain mill dust mix. Positive reactivity at 1 h and 4 h occurred in > 10% of horses for nine of 19 allergens (pollens, mosquito, storage mites) at their determined TC. Positive reactivity was rare at 24 h. This study in normal horses suggests that appropriate testing concentrations of allergens for equine IDT in atopic horses may be > or = 1000 PNU mL(-1) for pollens and moulds, 60 to 250 PNU mL(-1) for most insects and < 1 : 12,000 w v(-1) for dust mites; and that reactions at 1-4 h may be insignificant.     

Determination of irritant threshold concentrations to weeds,trees and grasses through serial dilutions in intradermal testing on healthy clinically nonallergic dogs

Irritant threshold concentration (ITC) for intradermal testing (IDT) was determined in 31 healthy, clinically nonallergic dogs. Twenty‐three allergens were tested at five variable concentrations ranging from 1000 to 8000 PNU/mL. To distinguish irritant reactions from subclinical IgE‐mediated hypersensitivities, serum allergy testing was performed. ITCs were determined by evaluating the lowest concentration to which no dogs (0% cut‐off) and to which at least 10% of dogs (≥10% cut‐off) reacted. ITCs at the 0% cut‐off were: 1000 PNU/mL (Johnson grass), 2000 PNU/mL (Ash, Lamb’s Quarter and Bermuda), 3000 PNU/mL (Bahia, Rye, Pig Weed and Virginia Oak), 4000 PNU/mL (Marsh Elder and Maple), 5000 PNU/mL (Sorrel sheep) and 7000 PNU/mL (Cocklebur and Black Willow). ITC for Dog Fennel, Box Elder and Red Cedar was <1000 PNU/mL. ITCs at the ≥10% cut‐off were: 2500 PNU/mL (Johnson), 3000 PNU/mL (Box Elder), 5000 PNU/mL (Bahia), 6000 PNU/mL (Pigweed and Marsh Elder) and 8000 PNU/mL (Virginia Oak and Black Willow). For all other allergens, the ITC was >8000 PNU/mL and could not be determined. No significant agreement between positive values was found for the same allergen on IDT and serum allergy testing for each dog suggesting reactions caused by the determined ITCs are less likely subclinical IgE‐mediated reactions. These results suggest that ITCs may vary, also they may be very high for the allergens tested and that higher test concentrations may be used for IDT for the tested allergens without inducing an irritant reaction. Further studies are needed to evaluate the benefit of higher IDT concentrations in atopic dogs.     

Intradermal and serological testing for mites in healthy beagle dogs

Background – Intradermal testing (IDT) is widely used in veterinary medicine to select allergens for immunotherapy. The recommended concentration for mites is 250 protein nitrogen units (PNU)/mL. It is not known whether healthy dogs responding to this concentration have asymptomatic sensitization or irritation. Furthermore, interbatch and intersupplier variability of allergens has not been fully addressed. Hypothesis/Objectives – The incidence of positive IDTs in healthy beagles was recorded and the value of combining these results with serology to differentiate between asymptomatic sensitization and irritancy evaluated. Additionally, the interbatch and intersupplier variability of allergens was assessed. Animals – Seventeen healthy laboratory beagles with no history or clinical signs of canine atopic dermatitis were used. Methods – Intradermal tests were performed with four mite allergens from two suppliers (varying batches). An initial IDT at 250 PNU/mL was used to determine whether decreasing or increasing test concentrations were used in the subsequent titration IDTs. Additionally, two IgE ELISA tests from different manufacturers were performed. Results – Seven of 17 dogs showed IDT reactions at 250 PNU/mL. There were highly significant allergen interbatch and significant intersupplier correlations and agreement. The associations between the IDT reactions and the IgE serologies statistically identified two groups of dogs: one with positive serology and IDT reactions at 250 PNU/mL; and another with negative serology and IDT reactions. Conclusions and clinical importance – Our results suggest that dogs that have IDT reactions and positive serology are asymptomatically sensitized, while dogs that react at higher allergen concentrations, but have negative serology, do so as a result of irritant reactions.     

Determination of 'irritant' threshold concentrations for intradermal testing with allergenic insect extracts in normal horses

Abstract Sixteen healthy horses with no history of skin or respiratory disease were used for an intradermal testing (IDT) threshold study, in order to determine the concentrations of 13 commercial allergenic insect extracts most appropriate for IDT. Five dilutions of each extract were used, which included the manufacturer's recommended concentrations for equine IDT, plus one dilution higher and three lower than these standard concentrations. Allergens tested included caddisfly ( Trichoptera spp.), mayfly ( Ephemeroptera spp.), horsefly ( Tabanus spp.), deerfly ( Chrysops spp.), fire ant ( Solenopsis invicta ), black ant ( Camponotus pennsylvanicus ), cockroach mix ( Periplaneta americana and Blattella germanica ), mosquito ( Aedes aegypti ), house fly ( Musca domestica ), moth ( Heterocera spp.), flea ( Ctenocephalides canis / C. felis ), Culicoides variipennis and Culicoides nubeculosis. Two separate methods were used to calculate the allergen concentration for each insect extract where the normal horses, as a group, ceased to show false-positive ('irritant') reactions. 'Irritant' threshold concentrations were determined for 9/13 of these allergens, whereas the other 4 were undetermined due to either insufficient reactivity (flea, C. variipennis ) or excessive reactivity (black ant, moth) to the concentrations tested. Recommended concentrations for future use in equine patients with suspected insect hypersensitivity include: 125 pnu mL⁻¹ (mayfly); 250 pnu mL⁻¹ (caddisfly, horsefly, deerfly, fire ant, house fly); 500 pnu mL⁻¹ (cockroach); 1000 pnu mL⁻¹ (mosquito); and 1:10 000 w/v ( C. nubeculosis ).     

FC‐51 Comparison of intradermal test and antigen‐specific IgE test in 22 cases of feline allergic dermatitis

The usefulness of the intradermal test (IDT) and the serological allergy test (SAT) for detecting antigen‐specific IgE in allergic cats has not yet been established. In this study, we compared the results of IDT with those of SAT and evaluated the clinical usefulness of the two tests for detecting possible allergens in allergic cats. IDT and SAT using eight antigens were performed on 22 cats with intense pruritus after excluding ectoparasites and performing diet elimination tests. Approximately 50% of the cats reacted to at least one allergen by either IDT or SAT, and 36.4% of the cats reacted on both IDT and SAT. In contrast, seven healthy cats did not show any reactions on IDT or SAT. The most commonly detected allergen in both tests was house dust mites (IDT, 36.4%; SAT, 40.9%). Five cats reacted to one allergen and the others reacted to more than one allergen with IDT. Three cats reacted to one allergen with SAT. The following percentage agreement between the results of the two tests was calculated: house dust mites (86.4%), cat fleas (63.6%), grass mix (86.4%), common mugwort (81.8%), cat epithelia (90.9%), ragweed (86.4%), Japanese cedar (90.9%), and plantain (81.8%). The overall mean percentage agreement was 83.5%. In summary, the present study showed good agreement between IDT and SAT for cats, and SAT may be more sensitive than IDT, but less specific for detecting sensitized allergens. Funding: Self‐funded.     

FC-53 Serologic allergy testing in horses with insect hypersensitivity

The usefulness of the intradermal test (IDT) and the serological allergy test (SAT) for detecting antigen-specific IgE in allergic cats has not yet been established. In this study, we compared the results of IDT with those of SAT and evaluated the clinical usefulness of the two tests for detecting possible allergens in allergic cats. IDT and SAT using eight antigens were performed on 22 cats with intense pruritus after excluding ectoparasites and performing diet elimination tests. Approximately 50% of the cats reacted to at least one allergen by either IDT or SAT, and 36.4% of the cats reacted on both IDT and SAT. In contrast, seven healthy cats did not show any reactions on IDT or SAT. The most commonly detected allergen in both tests was house dust mites (IDT, 36.4%; SAT, 40.9%). Five cats reacted to one allergen and the others reacted to more than one allergen with IDT. Three cats reacted to one allergen with SAT. The following percentage agreement between the results of the two tests was calculated: house dust mites (86.4%), cat fleas (63.6%), grass mix (86.4%), common mugwort (81.8%), cat epithelia (90.9%), ragweed (86.4%), Japanese cedar (90.9%), and plantain (81.8%). The overall mean percentage agreement was 83.5%. In summary, the present study showed good agreement between IDT and SAT for cats, and SAT may be more sensitive than IDT, but less specific for detecting sensitized allergens.
Funding: Self-funded.     

Comparison of intradermal and serum testing for allergen-specific IgE using a Fcepsilon RIalpha-based assay in atopic dogs in the UK

Atopic dermatitis in dogs is a common allergic skin disease that affects substantial numbers of dogs in the UK. The purpose of this study was to compare the results of an intradermal test (IDT) and an in vitro test in a large cohort of dogs. Dogs were intradermal tested with Greer allergens (Greer Labs Inc, Lenoir, NC, USA) using standard techniques. At the same time blood samples were drawn and submitted for evaluation by ELISA using the ALLERCEPT Definitive Allergen Panels for allergen-specific IgE, a commercial assay that uses a biotinylated recombinant extracellular domain of the high affinity Fc-epsilon receptor alpha chain protein (Fcepsilon RIalpha). The allergens used in the two tests included grass, tree and weed pollens, moulds, flea saliva/whole flea extract and house dust mite species. The optical density readings from the ELISA for each allergen were compared with the results of the IDT for 265 dogs. The prevalence of positive reactions in the ELISA was equal to or greater than the results of the IDT in the case of almost all of the allergens, but two notable exceptions were the house dust mites Dermatophagoides farinae and Dermatophagoides pteronyssinus. These two allergens were the most common positive reactions by IDT (prevalence D. farinae 78.9%, D. pteronyssinus 66.4%). The results of the two tests were significantly different (McNemar's test, P<0.05) for 16 of the 22 allergens. The sensitivities of the ELISA compared to the IDT (where there were more than 3 dogs with positive reactions in both tests) varied between 19.3 and 77.1% (D. pteronyssinus 19.3% and D. farinae 67.9%) and the specificities varied between 64.2 and 96.6% (D. pteronyssinus 96.6% and D. farinae 89.3%).     

Serum alhpa 1-acid glycoprotein concentrations in healthy and tumor-bearing cats

The purpose of this study was to evaluate alpha 1-acid glycoprotein (AGP) concentrations in tumor-bearing and healthy cats. The hypothesis of the present study was that AGP concentrations would be significantly increased in tumor-bearing cats. Serum from 51 healthy and 97 tumor-bearing, client-owned cats was harvested at the time of presentation and stored at -80 degrees C until assayed. Cats with measurable, histologically confirmed malignancies, and healthy cats of similar ages were included. Serum was assayed for AGP concentration by using a radial immunodiffusion method. AGP concentrations were significantly (P = .0051) higher in tumor-bearing (763 +/- 595 microg/mL; mean +/- SD) when compared to healthy cats (501 +/- 377 microg/mL; mean +/- SD). Of the tumor-bearing cats, 35 had carcinomas, 33 had sarcomas, and 26 had discrete, round cell tumors. AGP concentrations were 645 +/- 62 microg/mL, 660 +/- 540 microg/mL, and 967 +/- 860 microg/mL, respectively, and there were no significant differences among the groups.     

Pilot study: prevalence of positive aeroallergen reactions in 10 cats with small-airway disease without concurrent skin disease

The purpose of this study was to determine the prevalence of positive allergen reactions in cats with small-airway disease (i.e. 'feline asthma', 'feline allergic bronchitis', 'feline bronchial disease'). Intradermal skin tests (IDT) and serum immunoglobulin E (IgE) tests were performed in 10 cats with idiopathic small-airway disease and in 10 normal cats without a history of respiratory disease. None of the cats had a history of skin disease or clinical signs of skin disease at the time of testing. Significantly more individual positive allergen reactions were found on serum IgE tests than on IDT in both groups of cats. Affected cats had significantly more individual positive allergen reactions on both tests than unaffected cats. Both IDT and serum IgE tests resulted in more individual positive allergen reactions to weeds, trees, grasses, and/or moulds in affected cats than in normal cats. Significantly more positive allergen reactions to house dust mites were found in affected compared to non-affected cats by IDT but not by serum IgE testing. One unexpected obstacle to inclusion of more affected cats in the study was the concurrent presence or history of suspect or known allergic skin disease. Concurrent allergic skin disease has not been reported in association with small-airway disease in cats. The increased prevalence of individual positive allergen reactions in affected cats may be due to increased immunological reactivity in these cats. Further studies are needed to answer this question and to determine what role, if any, aeroallergens have in the pathogenesis of this complex feline disease.     

Effects of intravenous administration of lidocaine on the thermal threshold in cats

OBJECTIVE: To determine the effects of IV administration of lidocaine on thermal antinociception in conscious cats. ANIMALS: 6 cats. PROCEDURE: 2 experiments were performed in each cat (interval of at least 2 months). In experiment 1, lidocaine pharmacokinetics were determined for each conscious cat following IV administration of a bolus of lidocaine (2 mg/kg). In experiment 2, data from experiment 1 were used to calculate appropriate doses of lidocaine that would achieve predetermined plasma lidocaine concentrations in the cats; lidocaine (or an equivalent volume of saline [0.9% NaCl] solution as the control treatment) was administered IV to target pseudo-steady-state plasma concentrations of 0, 0.5, 1, 2, 5, and 8 microg/mL. Skin temperature and thermal threshold were determined at the start of the experiment (baseline) and at each concentration. Samples of venous blood were obtained at each target concentration for plasma lidocaine concentration determination. RESULTS: In experiment 2, actual plasma lidocaine concentrations were 0.00 +/- 0.00 microg/mL, 0.25 +/- 0.18 microg/mL, 0.57 +/- 0.20 microg/mL, 1.39 +/- 0.13 microg/mL, 2.33 +/- 0.45 microg/mL, and 4.32 +/- 0.66 microg/mL for target plasma concentrations of 0, 0.5, 1, 2, 5, and 8 microg/mL, respectively. Compared with baseline values, no significant change in skin temperature or thermal threshold was detected at any lidocaine plasma concentration (or saline solution equivalent). Skin temperature or thermal threshold values did not differ between lidocaine or control treatments. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that these moderate plasma concentrations of lidocaine did not affect thermal antinociception in cats.     

Relationship between plasma concentrations and analgesia after intravenous fentanyl and disposition after other routes of administration in cats

Data allowing rational use of analgesics in cats are limited. Pharmacokinetics and pharmacodynamics of fentanyl were studied in cats. Plasma fentanyl concentrations were measured using radioimmunoassay in a crossover study in six cats after 10 microg/kg (i.v.) or by application of fentanyl in pluronic lecithin organogel (PLO) to the inner ear pinna. On a separate occasion thermal thresholds were measured after i.v. fentanyl (10 microg/kg) or saline. Plasma fentanyl concentrations reached 4.7-8.31 ng/mL 2 min after i.v. administration and were undetectable after 95 min. Fentanyl was not detected in plasma at any time after PLO use. Thermal thresholds did not change following saline administration but were increased above baseline from 5 to 110 min after i.v. fentanyl. In this model a plasma concentration of >1.07 ng/mL was required to provide analgesia. Plasma concentrations were measured in additional cats after intranasal or oral dosing (2 microg/kg) and after 30 microg/kg in PLO gel. After oral and nasal dosing, Cmax values were 0.96 and 1.48 ng/mL at 5 and 2 min, respectively. Plasma fentanyl was not detected after application of the higher dose of fentanyl in PLO.     

Plasma homocysteine, B vitamins, and amino acid concentrations in cats with cardiomyopathy and arterial thromboembolism

Arterial thromboembolism (ATE) is a common complication of cats with cardiomyopathy (CM), but little is known about the pathophysiology of ATE. In people, high plasma concentrations of homocysteine and low B vitamin concentrations are risk factors for peripheral vascular disease. In addition, low plasma arginine concentrations have been linked to endothelial dysfunction. The purpose of this study was to compare concentrations of homocysteine, B vitamins, and amino acids in plasma of normal cats to those of cats with CM and ATE. Plasma concentrations of homocysteine, vitamin B6, vitamin B12, folate, and amino acids were measured in 29 healthy cats, 27 cats with CM alone, and 28 cats with both CM and ATE. No differences were found between groups in homocysteine or folate. Mean vitamin B12 concentration (mean +/- standard deviation) was lower in cats with ATE (866 +/- 367 pg/mL) and cats with CM (939 +/- 389 pg/mL) compared with healthy controls (1,650 +/- 700 pg/mL; P < .001). Mean vitamin B6 concentration was lower in cats with ATE (3,247 +/- 1.215 pmol/mL) and cats with CM (3,200 +/- 906 pmol/mL) compared with healthy control animals (4,380 +/- 1,302 pmol/mL; P = .005). Plasma arginine concentrations were lower in cats with ATE (75 +/- 33 nmol/mL) compared with cats with CM (106 +/- 25 nmol/mL) and healthy control animals (96 +/- 25 nmol/ mL; P < .001). Vitamin B12 concentration was significantly correlated with left atrial size. We interpret the results of this study to suggest that vitamin B12 and arginine may play a role in CM and ATE of cats.     

Use of an amplified ELISA technique for detection of a house dust mite allergen (Der f 1) in skin and coat dust samples from dogs

OBJECTIVE: To use an amplified ELISA technique to document the presence and quantify the concentration of the house dust mite allergen, Der f 1, in skin and coat dust samples collected from dogs. ANIMALS: 29 pet dogs of various breeds. PROCEDURE: Dogs were weighed, and body surface area in square meters was determined. Skin and coat dust samples were obtained by vacuuming dogs. Collected dust was analyzed by use of standard and amplified ELISA techniques. RESULTS: By use of the standard ELISA technique, Der f 1 was detected in skin and coat dust samples from 6 of 29 (21%) dogs. Mean concentration of Der f 1 in the 6 samples with positive assay results was 16.16 ng/mL (range, 5.61 to 31.24 ng/mL). Samples with negative assay results were retested for dust mite allergen by use of an amplified ELISA technique; an additional 14 dogs had positive assay results. Mean concentration of allergen was 0.36 ng/mL (range, 0.19 to 2.20 ng/mL). Combining both techniques, 20 of 29 (69%) dogs had positive assay results for Der f 1. CONCLUSIONS AND CLINICAL RELEVANCE: Results of our study indicate that house dust mite allergens are present on the skin and in the coat of dogs, and this source of allergen may act as a reservoir for allergen exposure in hypersensitive dogs. Use of an amplified ELISA technique to determine environmental concentrations of house dust mite allergens in homes and on dogs will help to identify the relationship between immunologic findings and environmental exposures in dogs with atopic dermatitis.     

Evaluation of the precision of intradermal injection of control substances for intradermal testing in clinically normal horses

OBJECTIVE: To evaluate the precision of intradermal testing (IDT) in horses. ANIMALS: 12 healthy adult horses. PROCEDURE: IDT was performed on the neck of each horse by use of 2 positive control substances (histamine and phytohemagglutinin [PHA]) and a negative control substance. An equal volume (0.1 mL) for each injection was prepared to yield a total of 20 syringes ([4 concentrations of each positive control substance plus 1 negative control substance] times 2 positive control substances times 2 duplicative tests) for each side of the neck. Both sides of the neck were used for IDT; therefore, 40 syringes were prepared for each horse. Hair was clipped on both sides of the neck, and ID injections were performed. Diameter of the skin wheals was recorded 0.5, 4, and 24 hours after ID injection. RESULTS: Intra- and interhorse skin reactions to ID injection of histamine and PHA resulted in wheals of uniform size at 0.5 and 4 hours, respectively. Significant intra- and interhorse variation was detected in wheals caused by PHA at 24 hours. CONCLUSIONS AND CLINICAL RELEVANCE: ID injection of histamine and PHA caused repeatable and precise results at 0.5 and 4 hours, respectively. Concentrations of 0.005 mg of histamine/mL and 0.1 mg of PHA/mL are recommended for use as positive control substances for IDT in horses. This information suggests that consistent wheal size is evident for ID injection of control substances, and variation in wheals in response to ID injection of test antigens results from a horse's immune response to specific antigens.     

Immunophenotyping of the cutaneous cellular infiltrate after atopy patch testing in cats with atopic dermatitis

Cats with spontaneously occurring atopic dermatitis have clinical and immunocytochemical characteristics compatible with these in humans with atopic dermatitis (AD). The atopy patch test (APT) has proven to be a valuable tool in elucidating the disease process in humans. Additionally, the APT is very specific and bypasses the problem of conflicting results due to differences in chronicity of lesions of AD patients. We adapted the APT for use in cats to explore the suitability of the APT as a tool to study the onset of allergic inflammation in cats with atopic dermatitis. APT were performed in AD cats (n = 6) and healthy cats (n = 10). All cats were patch tested with two allergens in three different dilutions and a diluent control. The allergens for the APT were selected from positive intradermal test and /or prick test results and consisted of: Dermatophagoides farinae, D. pteronyssinus, Tyrophagus putrescentiae, and a grass pollen mixture. APT were read after 10, 24 and 48 h, and punch biopsies for immunohistochemical evaluation were collected at these time points. Macroscopically positive APT reactions were observed in three out of six cats at 24 and/or 48 h with allergen concentrations of 25,000 and 100,000 NU/ml. Reactions were not observed at negative control sites and neither in control animals. A significantly increased number of IL-4+, CD4+, CD3+, MHC class II+ and CD1a+ cells was found in one AD cat with positive APT reactions. Five out of six AD cats had significantly increased IL-4+ T cell numbers at 24 and/or 48 h. Our data indicate that in cats, macroscopically positive patch test reactions can be induced, which have a cellular infiltrate similar to that in lesional skin. We found a high specificity and a macroscopically positive APT reaction in half of the cats, which is similar to what is seen in humans. Hence, the APT in cats might be a useful tool in studying the immunopathogenesis of feline atopic dermatitis.     

Pharmacokinetics and endometrial tissue concentrations of enrofloxacin and the metabolite ciprofloxacin after i.v. administration of enrofloxacin to mares

Enrofloxacin was administered i.v. to five adult mares at a dose of 5 mg/kg. After administration, blood and endometrial biopsy samples were collected at regular intervals for 24 h. The plasma and tissue samples were analyzed for enrofloxacin and the metabolite ciprofloxacin by high-pressure liquid chromatography. In plasma, enrofloxacin had a terminal half-life (t(1/2)), volume of distribution (area method), and systemic clearance of 6.7 +/- 2.9 h, 1.9 +/- 0.4 L/kg, and 3.7 +/- 1.4 mL/kg/min, respectively. Ciprofloxacin had a maximum plasma concentration (Cmax) of 0.28 +/- 0.09 microg/mL. In endometrial tissue, the enrofloxacin Cmax was 1.7 +/- 0.5 microg/g, and the t(1/2) was 7.8 +/- 3.7 h. Ciprofloxacin Cmax in tissues was 0.15 +/- 0.04 microg/g and the t(1/2) was 5.2 +/- 2.0 h. The tissue:plasma enrofloxacin concentration ratios (w/w:w/v) were 0.175 +/- 0.08 and 0.47 +/- 0.06 for Cmax and AUC, respectively. For ciprofloxacin, these values were 0.55 +/- 0.13 and 0.58 +/- 0.31, respectively. We concluded that plasma concentrations achieved after 5 mg/kg i.v. are high enough to meet surrogate markers for antibacterial activity (Cmax:MIC ratio, and AUC:MIC ratio) considered effective for most susceptible gram-negative bacteria. Endometrial tissue concentrations taken from the mares after dosing showed that enrofloxacin and ciprofloxacin both penetrate this tissue adequately after systemic administration and would attain concentrations high enough in the tissue fluids to treat infections of the endometrium caused by susceptible bacteria.     

Susceptibility of bacteria from feline and canine urinary tract infections to doxycycline and tetracycline concentrations attained in urine four hours after oral dosage

OBJECTIVES: To measure urinary concentrations of doxycycline in cats and dogs and tetracycline in dogs 4 h after conventional oral dosing and determine whether these antibiotics were present in sufficient concentrations to be effective against common feline and canine urinary tract pathogens as assessed in vitro by Epsilometer and disc diffusion antimicrobial susceptibility methods. DESIGN: A prospective study involving oral administration to clinically normal cats and dogs of doxycycline or tetracycline (dogs only) and culture of bacteria from dogs and cats with urinary tract infections to determine their susceptibility to both doxycycline and tetracycline in vitro. PROCEDURE: In the first study, nine cats and eight dogs were administered doxycycline monohydrate (5 mg/kg every 12 h) and a further eight dogs were administered tetracycline hydrochloride (20 mg/kg every 8 h) for 72 h. Blood was collected at 2 and 4 h, and urine at 4 h, after the last dose. The concentration of each agent in serum and urine was determined by modified agar diffusion. In the second study, 45 urine samples from cats and dogs with urinary tract infections were cultured. Every bacterial isolate was tested in vitro using both Epsilometer (doxycycline and tetracycline) and disc diffusion (doxycycline, tetracycline or amoxycillin-clavulanate) tests. RESULTS: Serum doxycycline concentrations in sera of cats and dogs at 2 h were 4.2 +/- 1.0 mg/mL and 3.4 +/- 1.1 mg/mL, respectively. The corresponding concentrations at 4 h were 3.5 +/- 0.7 mg/mL and 2.8 +/- 0.6 mg/mL. Urinary doxycycline concentrations at 4 h (53.8 +/- 24.4 mg/mL for cats and 52.4 +/- 24.1 mg/mL for dogs) were substantially higher than corresponding serum values. Serum tetracycline concentrations in dogs at 2 and 4 h, and in urine at 4 h, were 6.8 +/- 2.8, 5.4 +/- 0.8, 144.8 +/- 39.4 mg/mL, respectively. Most of the urinary tract pathogens (35/45) were susceptible to urinary concentrations of doxycycline and 38/45 were susceptible to tetracycline. In contrast 41/45 of all isolates were susceptible to amoxycillin-clavulanate. CONCLUSION: This is the first report of urinary concentrations of doxycycline after conventional oral administration. Concentrations attained in the urine of normal cats and dogs were sufficient to inhibit the growth of a significant number of urinary tract pathogens and thus doxycycline may be a useful antimicrobial agent for some urinary tract infections.     

Beneficial cross-protection of allergen-specific immunotherapy on airway eosinophilia using unrelated or a partial repertoire of allergen(s) implicated in experimental feline asthma

The study hypothesis was that in experimentally asthmatic cats rush immunotherapy (RIT) using allergens not completely matched with sensitizing allergen(s) would at least partially attenuate the asthmatic phenotype and modulate the aberrant immune response. In phase I, cats sensitized to Bermuda grass allergen (BGA), house dust mite allergen (HDMA) or placebo received BGA RIT. In phase II, cats dually sensitized to BGA and HDMA received RIT using BGA, HDMA or placebo. Efficacy of RIT was assessed using percentage bronchoalveolar lavage fluid (BALF) eosinophils. Additionally, a variety of immunologic assays were performed. Eosinophilic airway inflammation significantly decreased over time in asthmatic cats given RIT using sensitizing allergen or unrelated allergen (P<0.001). In dually sensitized cats, single allergen RIT but not placebo reduced airway eosinophilia (P=0.038). Differences in allergen-specific lymphocyte proliferation, in the number of IL-10 producing cells and in the percentage T regulatory cells were detected between asthmatic cats getting RIT and controls. Cross-protection manifested by reduced airway eosinophilia was noted in cats treated with RIT allergens which did not completely match allergen used in asthma induction. However, the mechanism of immunologic tolerance may differ when improperly matched allergens to the sensitizing allergens are used in RIT.     

Results of intradermal tests in horses without atopy and horses with atopic dermatitis or recurrent urticaria.

OBJECTIVE: To compare results of intradermal tests (IDT) for environmental allergens at 30 minutes and 4, 6, and 24 hours after injection in horses without atopy and horses with atopic dermatitis (AD) or recurrent urticaria (RU). ANIMALS: 22 horses without atopy, 10 horses with RU, and 7 horses with AD. PROCEDURE: In all horses, medical history was obtained, and results of physical examination, hematologic examination, serum biochemical analyses, examination of bronchoalveolar lavage fluid, and IDT with 73 allergens were examined. RESULTS: Horses with AD or RU had a significantly greater mean number of positive reactions for IDT, compared with horses without atopy. Horses with AD had a significantly greater number of positive reactions than horses without atopy in every allergen group at all time periods, except for molds at 4 and 24 hours. Horses with RU had a significantly greater number of positive reactions than horses without atopy in every allergen group, except for molds at 30 minutes and 4 and 6 hours, trees at 4 and 6 hours, and grasses at 4 hours. CONCLUSIONS AND CLINICAL RELEVANCE: A significantly greater number of positive reactions for IDT in horses with AD or RU, compared with horses without atopy, provides evidence of type-I IgE-mediated hypersensitivity for these diseases. Evaluation of results of IDT performed in horses with AD or RU is useful in determining specific allergens for the formulation of immunotherapy along with providing identification of allergens that could be useful when creating avoidance strategies.