Xeroradiographic evaluation of the equine larynx

The normal radiographic anatomy of the equine larynx was determine by use of xeroradiography and dissection. The body and laminae of the thyroid cartilage, the muscular process of the arytenoid cartilages, and the dorsal lamina and arch of the cricoid cartilage had radiographic evidence of mineralization (calcification) and/or ossification in clinically normal horses. There was a significant (P less than 0.01) increase in the degree of mineralization of the thyroid and arytenoid cartilages with advancing age. Horses with diagnosis of arytenoid chondrosis (arytenoid chondral dysplasia, arytenoid chondropathy) by use of endoscopy had radiographic changes that included: enlargement with increased density of the arytenoid cartilage region, abnormal patterns of mineralization (dystrophic mineralization or osseous metaplasia), abnormal contour of the corniculate process(es) and laryngeal masses, sometimes obliterating part or all of the lateral laryngeal ventricles.     

Effect of body size on gastric emptying using the 13C-octanoic acid breath test

The 13C-octanoic acid breath test (OABT) may be a useful non-invasive method for assessing the rate of gastric emptying in dogs. The aim of this study was to determine whether an association exists between body size and rate of gastric emptying in dogs. Fifty-five dogs ranging from 6 to 39 kg were recruited and rate of gastric emptying was assessed using the OABT. The time to peak 13CO2 excretion (tmax) and half-dose recovery time (t1/2) were calculated. The OABT was simple to perform and well tolerated by the dogs. Mean (sd) tmax was 2.67 hours (0.6) and mean t1/2 was 3.38 hours (0.79). Inter-individual variation in the rate of gastric emptying was 23.3 per cent for t1/2 and 22.5 per cent for tmax. No association was detected between the rate of gastric emptying and body surface area, mass, age, sex or test operator. The OABT may be a useful non-invasive and non-radioactive test for assessment of the rate of gastric emptying in dogs in clinical practice.     

Putative role of pith cell wall phenylpropanoids in Sesamia nonagrioides (Lepidoptera: Noctuidae) resistance

The stem borer Sesamia nonagrioides (Lefèbvre) is the most important insect pest that attacks maize, Zea mays L., in northwestern Spain. Host plant resistance to this borer was investigated in relation to the cell wall phenylpropanoids content in the pith. Eight inbred lines that differ in resistance were analyzed. Three major simple phenolic acids, p-coumaric, trans-ferulic, and cis-ferulic acids, and three isomers of diferulic acid, 8-5', 8-O-4', and 8-5'b (benzofuran form), were identified. The amount of all these compounds was correlated with the resistance level in the genotypes, with the resistant inbreds having the highest concentrations. The role of these compounds in cell wall fortification and lignification is well-documented, suggesting their possible intervention in S. nonagrioides resistance. Future studies that focus on these compounds could be useful to enhance S. nonagroides resistance.     

Foot-and-mouth disease virus: a first inter-laboratory comparison trial to evaluate virus isolation and RT-PCR detection methods

Five European reference laboratories participated in an exercise to evaluate the sensitivity and specificity of their routinely employed RT-PCR tests and cell cultures for the detection and isolation of foot-and-mouth disease (FMD) virus. Five identical sets of 20 coded samples were prepared from 10 vesicular epithelia, which were derived from submissions from suspect cases of FMD or swine vesicular disease (SVD). Sixteen samples were derived from six FMD virus positive epithelia representing four different serotypes (two each of types O and A and one each of types Asia 1 and SAT 2), two from samples which had been found to be negative by antigen ELISA and virus isolation (VI) in cell culture and two from SVD virus positive epithelia. Some of the FMD virus positive samples were prepared from 10-fold serial dilutions of three of the initial suspensions. Each laboratory tested the samples by one or more of its available RT-PCR procedures and inoculated cell cultures that it routinely uses for FMD diagnosis in attempts to isolate virus, the specificity of which was confirmed by antigen ELISA. The best of the RT-PCR assays used in each laboratory gave comparable results while the sensitivity of cell cultures was variable from high in one laboratory, moderate in two and low in two others. This prototype panel of samples would appear suitable for external quality assurance of these tests but would benefit from the inclusion of more negative samples and an extension in the serial dilution range of one or more of the FMD positive sample titration series.     

Pharmacokinetics and pharmacodynamics of enrofloxacin and a low dose of amikacin administered via regional intravenous limb perfusion in standing horses

OBJECTIVE: To evaluate the pharmacokinetic-pharmacodynamic parameters of enrofloxacin and a low dose of amikacin administered via regional IV limb perfusion (RILP) in standing horses. ANIMALS: 14 adult horses. PROCEDURES: Standing horses (7 horses/group) received either enrofloxacin (1.5 mg/kg) or amikacin (250 mg) via RILP (involving tourniquet application) in 1 forelimb. Samples of interstitial fluid (collected via implanted capillary ultrafiltration devices) from the bone marrow (BMIF) of the third metacarpal bone and overlying subcutaneous tissues (STIF), blood, and synovial fluid of the radiocarpal joint were collected prior to (time 0) and at intervals after tourniquet release for determination of drug concentrations. For pharmacokinetic-pharmacodynamic analyses, minimum inhibitory concentrations (MICs) of 16 microg/mL (amikacin) and 0.5 microg/mL (enrofloxacin) were applied. RESULTS: After RILP with enrofloxacin, 3 horses developed vasculitis. The highest synovial fluid concentrations of enrofloxacin and amikacin were detected at time 0; median values (range) were 13.22 microg/mL (0.254 to 167.9 microg/mL) and 26.2 microg/mL (5.78 to 50.0 microg/mL), respectively. Enrofloxacin concentrations exceeded MIC for approximately 24 hours in STIF and synovial fluid and for 36 hours in BMIF. After perfusion of amikacin, concentrations greater than the MIC were not detected in any samples. Effective therapeutic concentrations of enrofloxacin were attained in all samples. CONCLUSIONS AND CLINICAL RELEVANCE: In horses with orthopedic infections, RILP of enrofloxacin (1.5 mg/kg) should be considered as a treatment option. However, care must be taken during administration. A dose of amikacin > 250 mg is recommended to attain effective tissue concentrations via RILP in standing horses.     

Gasterophilosis: a major cause of rectal prolapse in working donkeys in Ethiopia

A retrospective study was conducted to investigate the cause of rectal prolapse in working donkeys in Ethiopia. Analysis of data on rectal prolapse cases obtained from the Donkey Health and Welfare Project clinic at the School of Veterinary Medicine, Addis Ababa University, from 1995 to 2004 revealed that 83.6% (n = 177) of the cases were associated with Gasterophilus nasalis. The rest 10.7% and 5.7% were associated with work-related (overloading) cause and diarrhoea, respectively. The mean and median numbers of G. nasalis recovered from the rectum of infected donkeys were 66 and 64, respectively, with a range of 2–195. Over 100 G. nasalis larvae were recovered from the rectum of 22% of the donkeys. Circular demarcated ulcer-like and deep circumferential pits or ring-like mucosal lesions were found at the larval attachment sites. G. nasalis infection and the associated rectal prolapse were observed year round. However, the intensity of rectal larval infection and incidence of rectal prolapse were significantly higher during the rainy season (P < 0.01). Age and sex of the donkeys had no significant effect on the intensity of rectal larval infection and incidence of rectal prolapse (P > 0.05).     

Preserving new anthelmintics: a simple method for estimating faecal egg count reduction test (FECRT) confidence limits when efficacy and/or nematode aggregation is high

As it has been 30 years since a new anthelmintic class was released, it is appropriate to review management practices aimed at slowing the development of anthelmintic resistance to all drug classes. Recommendations to delay anthelmintic resistance, provide refugia and the use of a simulation model were reviewed to find optimum treatment strategies that maintain nematode control. Simulated Australian conditions indicated that a common successful low-risk treatment program was a rapid rotation between a "triple-combination" product (benzimidazole+levamisole+abamectin) and a new high-efficacy drug (monepantel). Where Haemonchus contortus was a threat, moxidectin was required at critical times because of its persistent activity against this parasite. Leaving up to 4% of adult sheep untreated provided sufficient "refugia" for non-selected worms to reduce the risk of selecting for anthelmintic resistance without compromising nematode control. For a new anthelmintic, efficacy estimated by faecal egg count reduction (FECR) is likely to be at or close to 100%, however using current methods the 95% confidence limits (CL) for 100% are incorrectly determined as 100%. The fewer eggs counted pre-treatment, the more likely an estimate of 100% will occur, particularly if the true efficacy is >90%. A novel way to determine the lower-CL (LCL) for 100% efficacy is to reframe FECR as a binomial proportion, i.e. define: n and x as the total number of eggs counted (rather than eggs per gram of faeces) for all pre-treatment and post-treatment animals, respectively; p the proportion of resistant eggs is p = x/n and percent efficacy is 100 ×(1-p) (assuming equal treatment group sizes and detection levels, pre- and post-treatment). The LCL is approximated from the cumulative inverse beta distribution by: 95%LCL=100 ×(1-(BETAINV(0.975, x+1, n-x+1))). This method is simpler than the current method, independent of the number of animals tested, and demonstrates that for 100% efficacy at least 37 eggs (not eggs per gram) need to be counted pre-treatment before the LCL can exceed 90%. When nematode aggregation is high, this method can be usefully applied to efficacy estimates lower than 100%, and in this case the 95% upper-CL (UCL) can be estimated by: 95% UCL = 100 ×(1((BETAINV(0.025, x+1, n-x+1))), with the LCL approximated as described above. A simulation study to estimate the precision and accuracy of this method found that the more conservative 99%CL was optimum; in this case 0.975 and 0.025 are replaced by 0.995 and 0.005 to estimate the LCL and UCL, respectively.     

The efficacy of oxfendazole administered as a bolus compared with a drench formulation

Summary

In a flock of 40 ewe lambs of the Texel breed the anthelmintic oxfendazole was tested in two different formulations, a 2.265 per cent suspension and a 4 gram bolus containing 151 mg active ingredient. All treatments were based on a dose rate of 5 mg / kg body weight. Faecal examinations and larval differentiations were carried out on the day of treatment and two and seven days later. No differences in efficacy were apparent between the two treated groups.

Oxfendazole in either formulation was 100 per cent effective in removing the major strongylids and trichostrongylids.

A lower activity was seen against Strongyloides papillosus.