Evaluation of tests for anthelmintic resistance in cyathostomes

Resistance, especially to the anthelmintic benzimidazoles (BZ), has been reported in horse cyathostomes world-wide. Diagnosis of resistance has traditionally been made by faecal egg count reduction (FECR) trials, however, this technique has limitations. Some of the shortcomings may be resolved by refining the test or by using an in vitro test. FECR tests and the larval development assay (LDA) were performed on adult horses held on 15 different horse properties across a wide geographical area of NSW, Australia. FECR were measured before and 10-14 after days treatment with oxibendazole (OBZ), morantel (MOR) or ivermectin (IVM) at recommended dose rates. Eight properties were rejected following low pre-treatment egg counts, leaving seven in the study. On these, the majority of larvae recovered from faecal cultures were cyathostomes. Using a definition of resistance as a FECR of <90%, resistance to OBZ was present on six properties and to MOR on two properties. Resistance to IVM was not detected. An alternative method of calculating FECR based on individual horse egg counts pre- and post-treatment was developed and results from the same properties compared with the results of the LDA. For example, for the BZ, correlation coefficients of values of lethal concentration to kill 50% of population (LC50) on LDA and FECR percentages were -0.536 before and -0.704 after OBZ treatment. We conclude that the LDA has the potential to be a single visit test for detection of anthelmintic resistance in horse cyathostomes but requires further investigation and standardisation.     

Monoclonal antibodies specific for Campylobacter fetus lipopolysaccharides

Four monoclonal antibodies (mAbs) (M1357, M1360, M1823 and M1825) which reacted with Campylobacter fetus lipopolysaccharide (LPS) core region epitopes were produced and characterized. Reactivity of these mAbs with C. fetus core LPS epitopes was determined by enzyme-linked immunosorbent assay (ELISA) with whole cell proteinase K digests and phenol-water extracted LPS, and by immunoblotting with proteinase K digests. The specificities of the four mAbs were evaluated using an indirect ELISA. One of the mAbs reacted with 42 and three of the mAbs reacted with 41 of the 42 C. fetus strains examined. No reaction was observed between the four mAbs and 32 non-C. fetus bacteria tested, with the exception of one mAb with one organism. The four mAbs reacted with serotype A and B strains indicating the presence of shared epitopes in C. fetus LPS core oligosaccharides. The specificities of three mAbs previously produced to C. fetus LPS O-antigens (M1177, M1183 and M1194) were also evaluated and no reaction was observed with these mAbs and the 32 non-C. fetus bacteria tested. Strong immunofluorescence reactions were observed with the anti-O chain mAbs and selected C. fetus strains of the homologous serotype. These anti-LPS core oligosaccharide and anti-LPS O chain mAbs are highly specific for C. fetus and are potentially useful as immunodiagnostic reagents for detection, identification and characterization of C. fetus.     

Serological responses against the pathogenic dimorphic fungus Mucor amphibiorum in populations of platypus (Ornithorhynchus anatinus) with and without ulcerative mycotic dermatitis

Mucor amphibiorum, a dimorphic fungus, causes ulcerative dermatitis and systemic infections in the platypus Ornithorhynchus anatinus in some river systems in Tasmania but apparently not in other regions of Australia. As yet there are no suitable tests for population surveys, nor for detection of internal lesions in live animals. Consequently, immunoglobulins were purified from the serum of platypuses and anti-immunoglobulin antisera were prepared in rabbits in order to develop an enzyme-linked immunosorbent assay (ELISA) for anti-M. amphibiorum antibodies. Antigens from plate-grown cultures resulted in greater signal-to-noise ratios in indirect ELISA than those from broth-grown cultures. Platypuses with clinical ulcerative dermatitis had elevated anti-Mucor antibody levels compared to apparently unaffected individuals. Seroconversion was observed in one animal coincident with the development of cutaneous ulcers. The results suggested that platypuses in affected rivers were exposed to M. amphibiorum at a higher frequency than the occurrence of clinical disease. Some platypuses from New South Wales had elevated antibody levels but these increased significantly with age suggesting exposure to cross-reactive antigens, although exposure to M. amphibiorum cannot be excluded. Further studies are warranted to determine factors that result in progression from infection to disease, the occurrence of the fungus in areas where disease has not been observed and the specificity of antigen used in ELISA.     

A novel nonsuppurative meningoencephalitis in young greyhounds in Ireland

Fourteen 4- to 18-month-old vaccinated Greyhounds (10 males, 4 females) from three kennels in southern Ireland presented over a 2-year period with acute or insidious onset neurological signs. Head tilting, ataxia, recumbency, circling, and blindness were commonly observed, and animals were dull, dehydrated, and had lost weight. Hematologic and biochemical parameters reflected dehydration but were otherwise unremarkable. Microscopic examination revealed severe diffuse and focal gliosis and gemistocytosis accompanied by mononuclear cell perivascular cuffing in caudate nucleus and cortical gray matter of the cerebrum and in the periventricular gray matter of the anterior brainstem. Milder lesions were noted in the caudal brainstem, cranial spinal cord, and in the molecular layer of the cerebellum. This was accompanied by a lymphocyte and plasma cell infiltration of the cerebral and cerebellar meninges. Demyelination, neuropil necrosis, neuronophagia, and vasculitis were not observed. No inclusion bodies, fungi, or protozoal cysts were seen. Additional serologic and molecular pathology tests also failed to determine a cause, suggesting that these cases may represent a previously undiagnosed condition in the dog.     

An immunohistochemical study of the organization of ganglia and nerve fibres in the mucosa of the porcine intestine

In order to elucidate the organization of the enteric nervous system in the mucous plexus, wholemounts from six intestinal regions in six pigs were studied by vasoactive intestinal peptide, substance P, nitric oxide synthase and neurofilament proteins immunohistochemistry. The mucous plexus of both large and small intestine contained ganglia and isolated neurons. They were many and comparably larger in the caecum and colon, few in the ileum, and fewer and smaller in the jejunum. The mucous plexus was subdivided into the lamina muscularis mucosae and lamina proprial subplexuses, and based on location the latter was subdivided further in order to clarify their variations with respect to the amount, sizes and shapes of ganglia and neurons, sizes and orientation of nerve strands and immunoreactivities. Ganglia were situated at different topographical levels in the lamina muscularis mucosae subplexus, outer proprial and interglandular proprial meshworks in the lamina proprial subplexus with the majority of ganglia occurring in the outer proprial meshwork. The mucous plexus in the intestine of the pig is thus a ganglionated plexus showing marked segmental variation in the amount of intramucosal ganglia and isolated nerve cells. These new observations, calls for a re-examination of the mucous plexus to elucidate the regulatory mechanisms of importance in mucosal functions and consideration of the mucous plexus in the intestine of the pig to be one of the major ganglionated plexuses.     

Disposition kinetics of tylosin administered intravenously and intramuscularly to pigs

The distribution of tylosin was studied using a crossover design, in six pigs following i.v. and i.m. administration of 10 mgkg(-1) b.w. Plasma samples were analysed by HPLC and UV absorbance detection. After i.v. administration, t(1/2beta) was 271.3 min, V(d) 14.6 Lkg(-1), V(ss) 9.7 Lkg(-1) and CL 26.8 mLmin(-1)kg(-1). After i.m. administration, a C(max) of 1 microgmL(-1) was reached at 90 min. Mean absorption time was 1988.7 min and bioavailability was 95%.     

Heparinised blood ionised calcium concentrations in horses with colic or diarrhoea compared to normal subjects

Our objectives were to 1) establish ionised calcium (ICa), C-terminal PTH and biologically active PTH (intact molecule) concentrations in blood from normal horses, 2) examine the stability of ionised calcium and acid-base values in stored equine heparinised blood and serum and 3) check the applicability of the formulas based on these parameters in certain disease states. Mean +/- s.d. % ionised calcium in heparinised blood of normal Warmbloods was 51 +/- 2.7 (n = 20) of total calcium, range 1.45-1.75 mmol/l (n = 15) at Michigan State University and 1.43-1.69 mmol/l (n = 20) at Utrecht University. Mean +/- s.d. EDTA plasma concentration for intact +/PTH in normal horses measured 0.6 +/- 0.3 pmol/l (n = 11). Both mean serum and the heparinised blood ionised calcium concentrations changed (not significantly) after 102 h storage at room temperature. Six cycles of freezing and thawing did not affect serum ionised calcium concentration significantly. Ionised calcium concentration and pH in heparinised blood of 20 normal Warmbloods were used to calculate the regression equation for the prediction of the adjusted ionised calcium concentration to a pH of 7.4. The linear regression equation found was: adjusted plasma ICa at pH 7.4 mmol/l = -6.4570 + 0.8739 x (measured pH) + 0.9944 x (measured ICa mmol/l). By means of this formula, mean adjusted ionised calcium concentration in heparinised blood calculated was 100% of the actual value given by the analyser in the normal horses. When using this formula in horses with colic or diarrhoea, mean adjusted ionised calcium concentration was underestimated by 0.2 and 0.3%, respectively. Furthermore, to adjust the measured ionised calcium concentration in heparinised blood to a pH of 7.4 in healthy as well as in 2 groups of diseased horses 2 formulas with a good prediction are now available.     

Relationship between semi-quantitative thyroid palpation and total thyroxine concentration in cats with and without hyperthyroidism

In 155 cats, both with and without clinical signs of hyperthyroidism, total thyroxine (TT4) concentrations were compared to a sensitive, semi-quantitative thyroid palpation technique. On the basis of TT4 concentrations, 23 of the 155 cats were classified as hyperthyroid. The size of individual thyroid glands was scored between '0' (non-palpable) and a maximum of '6'. One or more enlarged thyroid glands (score >0) were palpated in 22 of the 23 hyperthyroid cats and in 78 of the 132 euthyroid cats. However, none of the 132 euthyroid cats had a thyroid lobe score of greater than '3' whereas 18 of the 23 hyperthyroid cats had a thyroid lobe score of '4' or greater, and in two of the five that had scores below '4' there was evidence of intrathoracic functional thyroid tissue on scintigraphy.     

Degree of amino acid restrictions during the grower phase and compensatory growth in pigs selected for lean growth efficiency

A total of 32 select line (SL) and 32 control line (CL) Duroc pigs were used in two trials to determine the effect of dietary amino acid contents during the grower (G) phase and selection for lean growth efficiency on growth performance, carcass traits, and meat quality. In each trial, pigs weighing 20 kg were assigned to 16 pens with two gilts or two castrated males per pen, and pens were randomly assigned within the genetic line to corn-soybean meal G diets formulated to contain 5.0, 7.0, 9.0, or 11.0 g lysine/kg. After 50 kg, all pigs were fed common finisher 1 (F1) and finisher 2 (F2) diets. Pigs were allowed ad libitum access to feed and water. After the initial statistical analyses, the data sets from the two trials were combined. During the G phase, pigs consumed less feed [linear (Ln), P < 0.001] and more lysine (Ln, P < 0.001), grew faster (Ln, P < 0.05) but utilized feed more and lysine less efficiently (Ln, P < 0.001) for weight gain as the amino acid content of G diets increased. Increasing dietary amino acids resulted in less ultrasound backfat (Ln, P < 0.001) and more serum urea nitrogen [Ln, P < 0.001; quadratic (Qd), P < 0.01] at the end of the G phase. Pigs grew more slowly during the F1 (Ln, P < 0.01 and Qd, P = 0.05) and F2 (Ln, P = 0.07) phases and utilized feed and lysine less efficiently (Ln, P < 0.05) for weight gain during the F1 phase as the amino acid content of G diets increased. The grower diet had no effect on overall weight gain and feed efficiency, carcass traits, or meat quality scores. The efficiency of lysine utilization for overall weight gain (Ln, P < 0.001) and lean accretion (Ln, P < 0.05) improved as the amino acid content of G diets decreased. The SL pigs grew faster (P < 0.05) and had less (P < 0.001) ultrasound backfat throughout the study compared with the CL pigs. The SL pigs had less 10th rib backfat (P < 0.001) and tended to have larger longissimus muscle area (P = 0.09) than the CL pigs, which were reflected in greater rate (P < 0.001) and efficiency (P < 0.05) of lean accretion. Marbling (P < 0.05) and meat color (P = 0.07) scores were lower in the SL pigs. No grower diet x genotype interactions were observed in response criteria of interest. The results indicate that pigs subjected to dietary amino acid restrictions during the G phase (as low as 5.0 g lysine/kg) compensated completely in terms of growth rate and body composition regardless of the genotype. Compensatory growth can have a positive impact not only on the overall efficiency of pig production but also on the environment by reducing excretion of unused nutrients.