Prevalence of cpb2, encoding beta2 toxin,in Clostridium perfringens field isolates: correlation of genotype with phenotype

Beta2 toxin, encoded by the cpb2 gene, has been implicated in the pathogenesis of porcine, equine and bovine enteritis by type A Clostridium perfringens. By incorporating primers to cpb2 into a multiplex genotyping PCR, we screened 3270 field isolates of C. perfringens. Of these, 37.2% were PCR positive for the cpb2 gene. The majority of isolates from cases of porcine enteritis were positive for cpb2 (>85%), and this was even more true for C. perfringens isolated from cases of porcine neonatal enteritis (91.8%). In contrast, isolates from normal pigs only contained cpb2 in 11.1% of cases. The correlation between enteritis in other animal species and the presence of cpb2 was not so strong. cpb2 was found in 21.4% of C. perfringens isolates from cattle with enteritis, and in 47.3% of isolates from calves with enteritis or abomastitis. The prevalence of cpb2 varied with genotype, with type A isolates being positive for this gene in 35.1% of cases. Furthermore, enterotoxigenic type D or type E strains almost always carried cpb2. We cloned a 6xHIS-tagged beta2 (HIS-beta2) and used this protein to raise antiserum against beta2. Culture supernatants from 68 cpb2-positive and 13 cpb2-negative strains were tested for the presence of beta2 by Western blotting. In cpb2-positive isolates of porcine origin, beta2 was almost always detected (96.9%). However, in cpb2-positive isolates from other animal species, only 50.0% expressed beta2 protein. The high rate of cpb2-positivity among strains from neonatal pigs with enteritis and the high correlation of genotype with phenotype, supports the contention that beta2 toxin plays a role in the pathogenesis of these infections. However, it may be important to consider the use of an additional method for the detection of beta2 toxin in non-porcine cpb2-positive isolates when making claims about the role of beta2 in enteritis in non-porcine species.     

Combined dorsolateral and intraoral approach for the resection of tumors of the maxilla in the dog

This paper describes in detail a combined dorsal and intraoral approach for maxillectomy for tumors involving tissues more caudal to the third premolar. The only intraoperative complication was that of blood loss, with six out of 20 dogs requiring a single unit of blood. Histopathologically clean margins were obtained in 14 of the 20 cases, with a recurrence rate of 50% in these dogs and a median time to recurrence of 24 months. This represents an improvement in outcome over previously reported studies, and the authors postulate this is due to the better exposure and access to the area afforded by the combined approach over the standard intraoral approach.     

Efficacy of extended pirlimycin hydrochloride therapy for treatment of environmental Streptococcus spp and Staphylococcus aureus intramammary infections in lactating dairy cows

Fifty-one chronically infected lactating dairy cows were used to evaluate the efficacy of extended pirlimycin therapy regimens for treatment of intramammary infections by environmental Streptococcus spp and Staphylococcus aureus. Cows (n = 47) with one or more infected mammary quarters were blocked by parity and randomly allocated to one of three groups for treatment with pirlimycin (50 mg/mammary quarter) as follows: one treatment per day for 2 days (n = 36 infected mammary quarters); one treatment per day for 5 days (n = 36 infected mammary quarters); and one treatment per day for 8 days (n = 20 infected mammary quarters). Four cows with nine infected mammary quarters were included as untreated controls. Milk samples from each mammary quarter were collected 7 days before treatment, immediately before treatment, and weekly for 4 weeks after the final treatment for microbiological evaluation. A bacteriologic cure was defined as a treated, infected quarter that was bacteriologically negative for the presence of previously identified bacteria at weekly intervals after treatment. Efficacy of pirlimycin therapy against intramammary infections caused by environmental Streptococcus spp and S. aureus was 44.4%, 61.1%, and 95.0% for the 2-, 5-, and 8-day treatment regimens, respectively. None of the infections in the untreated control quarters was cured. Significant differences in efficacy were detected between all pirlimycin groups and the untreated control group, between the 8- and 2-day treatment regimens, and between the 8-day and 5-day treatment regimens (P < or = .05). Results of this study indicate that extended pirlimycin therapy was effective in eliminating intramammary infections caused by environmental streptococci and S. aureus in lactating dairy cows.     

Antihistamines in the management of canine atopic dermatitis: a retrospective study of 171 dogs (1992-1998)

Antihistamines were prescribed for 178 of 271 dogs with a diagnosis of atopic dermatitis at the Veterinary Medical Teaching Hospital of the University of California, Davis from 1992 to 1998. Fifty-four percent of 166 dogs given antihistamines responded favorably to these treatments, with 27% of the responses rated as good and 27% rated as moderate. Diphenhydramine and hydroxyzine were the most commonly used antihistamines and were the most frequently effective. Chlorpheniramine and clemastine were administered less frequently and had much lower positive response rates. Responses to antihistamines as a group were significantly better in dogs having onset of clinical signs at younger ages (odds ratios for 1-year increase in age = 0.72, 95% confidence interval = 0.57 to 0.91, P =.005).     

Plasma adrenocorticotropin (ACTH) concentrations and clinical response in horses treated for equine Cushing's disease with cyproheptadine or pergolide

Plasma ACTH levels have been variable in horses with a positive clinical response for therapy for equine Cushing's Disease (ECD). Therefore, our purpose was to determine the value of monitoring plasma adrenocorticotropin (ACTH) levels during treatment of equine Cushing's disease (ECD) with either cyproheptadine (n = 32) or pergolide (n = 10). First, we validated the chemiluminescent ACTH assay (specificity, precision, accuracy, intra-assay and interassay variations) and tested methods of handling the whole blood from the time of collection to when the ACTH was assayed. The sensitivity and specificity of high plasma ACTH levels for detecting ECD was determined in a retrospective study on hospitalised horses (n = 68). Surveys were sent to veterinarians who submitted equine ACTH levels that were high initially and had at least 2 ACTH samples to determine the value of monitoring ACTH levels during therapy of ECD. The ACTH chemiluminescent assay was valid. The ACTH was stable when whole blood was collected and held in plastic tubes for 8 h before separating the plasma. The sensitivity and specificity of plasma ACTH levels for detecting ECD were 84% (n = 19,95% CI 60,97) and 78% (n = 49,95% CI 63,88), respectively. Treated horses generally showed a decrease in plasma ACTH. Plasma ACTH levels may be helpful when monitoring therapy of ECD, although improvement in clinical signs should be considered most important. There were no differences between cyproheptadine and pergolide in terms of improvements in any of the clinical signs.     

Prevalence and diversity of Arcobacter spp. isolated from the internal organs of spontaneous porcine abortions in Denmark

A study was conducted to determine the prevalence and possible significance of campylobacteria in pig abortions in Denmark. Surface-cauterised liver and kidney samples from 55 aborted pig fetuses submitted to the Danish Veterinary Laboratory were taken and a sensitive isolation procedure used to examine pooled tissue samples for Campylobacter, Arcobacter and Helicobacter spp. Routine microbiological, immunological, and histopathological examinations were also performed to identify concurrent infections or histopathological changes. The abortions tested negative for established abortifacient pathogens (Brucella, Leptospira, PPV, PRRSV), but Arcobacter spp. were recovered from 23/55 abortions. Co-infections with Streptococcus suis, Escherichia coli, and haemolytic streptococci were observed in 7/23 Arcobacter-positive fetuses, and in 4/32 Arcobacter-negative fetuses. Histopathological analyses identified placentitis, pneumonia, hepatitis and encephalitis among the study group. However, no obvious pathologic features were solely associated with Arcobacter-positive cases, nor were Arcobacter-like bacteria observed in tissue samples. Protein profile analyses of the 27 Arcobacter isolates identified 11 as A. cryaerophilus and 10 as A. skirrowii. Six strains could not be classified into any existing species and were phenotypically distinct, thus, potentially representing at least one new species. The identification results showed that multiple taxa could be found in a single fetus, and in distinct aborted fetuses from a single sow. The high prevalence of arcobacters in Danish pig abortions may account for at least some of the >90% of cases in which no established abortifacient agent is detected, but further studies are needed to define the role of each species, especially where co-infections with other bacteria are present.     

Canine atopic dermatitis: a retrospective study of 169 cases examined at the University of California, Davis, 1992-1998. Part II. Response to hyposensitization

One hundred and sixty-nine dogs were diagnosed with atopic dermatitis, and treated with hyposensitization for at least 1 year based on the results of either intradermal skin tests (IDST) or enzyme-linked immunosorbant serum assays (ELISA). Excellent (i.e. hyposensitization alone controlled clinical signs), good (> 50% improvement), moderate (< 50% improvement) and no (clinical signs were unchanged) responses were seen in 19.5, 32.5, 20.1 and 27.8%, respectively. Age of onset, age when treatment was initiated or the duration of clinical signs had no influence on response to hyposensitization. Dogs having concurrent flea allergy dermatitis were statistically more likely to respond better than dogs with concurrent food allergies. Although not statistically significant, there were trends for Golden Retriever and male dogs to respond better than other breeds and female dogs, respectively. Dogs having more than 21 positive reactions in allergy tests and treated with more than 21 allergens had lower response scores, and a longer time course before achieving beneficial response. Lower response scores were seen in dogs having positive reactions to cultivated plants, grasses, trees or insects. There was no difference in response to hyposensitization whether based on IDST or ELISA results.     

Temporal and spatial dynamics of insecticide resistance in Myzus persicae (Hemiptera: Aphididae)

Advances in understanding insecticide resistance in the peach-potato aphid, Myzus persicae (Sulzer), at the genotypic, biochemical and molecular levels have led to rapid and precise methods for the detection of several resistance mechanisms (elevated carboxylesterase, modified acetylcholinesterase or MACE, and knockdown resistance or kdr) in individual insects, and for monitoring their frequencies over space and time. This paper summarises the results of two long-term surveys of resistance dynamics in M persicae in England, based on samples collected directly from field and glasshouse crops or from four 12.2-m suction traps. The study showed marked fluctuations in resistance frequencies that probably reflect the counteracting forces of selection imposed by insecticides for aphids possessing more copies of esterase resistance genes, and selection against these forms when insecticide use is relaxed. There is growing evidence that several different resistance mechanisms in M persicae have associated fitness costs. In the case of esterase and MACE, these costs are apparently strong enough to effect a decline in resistance frequency over winter, and a more prolonged decline over successive cropping seasons when aphid numbers are insufficient to trigger intensive chemical applications. Changes in the overall frequency of resistance genotypes may also be influenced by the predominance of year-round parthenogenesis in M persicae in the UK, leading to non-random associations between mechanisms and selection operating on clonal lineages rather than individual genotypes.     

Hemorrhagic diathesis, mesenteric hematoma, and colic associated with ingestion of sweet vernal grass in a cow

A 4-year-old Holstein cow from a farm where 2 cows had recently died suddenly was referred for evaluation of acute severe colic. Right flank laparotomy revealed a large mesenteric hematoma. Within 14 layer chromatographic analyses of the moldy hay and blood from the necropsied cow and the hospitalized cow were positive for dicumarol. A diagnosis of sweet vernal poisoning was confirmed on the basis of clinical and toxicologic findings. The cow was treated with supportive therapy, blood transfusions, and vitamin K1 and recovered without complications. Because sweet vernal grass is becoming common in certain areas and the use of round bales is commonplace, practitioners should be aware of the potential for this toxicosis.