P. Ossent

Suspensory structures and supporting tissues of the third phalanx of cows and their relevance to the development of typical sole ulcers (Rusterholz ulcers)

The mural suspensory apparatus of third phalanx and its supportive heel cushion were examined in 19 cows with an ulcer at the ‘typical’ site (Rusterholz ulcer) to gain information on the pathogenesis of sole and heel ulcers. The claws of 17 healthy controls were used for comparison. The left hind claws, frozen at −20°C, were sectioned in one longitudinal and four transverse planes with a band saw. The thickness of the subcutaneous tissue, the corium and the extent of displacement of the third phalanx were measured at defined sites on these sections. In addition, the suspensory apparatus, the tissue layer connecting the third phalanx to the dorsal wall of the horn capsule, was examined histologically. There was a direct relationship between the displacement of the third phalanx and ulceration of the sole or heel; in all the ulcerated claws the third phalanx had dropped and the corium and the subcutis under the bone were thinner than in the controls. The supportive cushions of the cows with ulcers contained less fat tissue. There was no histological evidence of damage to the epidermis or the corioepidermal junction in the ulcerated claws nor were the lamellae elongated. Similarly, there were no morphological changes in the connective tissue layer, the submural dermis.

Larvicidal effect of imidacloprid/moxidectin spot-on solution in dogs experimentally inoculated with Angiostrongylus vasorum

A controlled, randomized, blinded dose confirmation study was conducted to evaluate the larvicidal efficacy and safety of imidacloprid 10 mg/kg/moxidectin 2.5 mg/kg body weight spot-on solution in dogs experimentally inoculated with 200 infective third stage larvae (L3) of Angiostrongylus vasorum. Twenty-four adult dogs were randomly allocated to three study groups of 8 dogs each. Animals in group 1 were treated 4 days post-inoculation (dpi), those in group 2 at 32 dpi, and the dogs in group 3 were left untreated. All dogs were euthanized and necropsied 56-59 dpi. In order to determine the worm burdens in the arterial lung vessels a method of reverse lung perfusion with phosphate buffered solution after inhibition of coagulation with heparin was applied. In the control group, excretion of first stage larvae (L1) of A. vasorum started 47-55 dpi and all dogs excreted L1 at least on one sample day before euthanasia (0.1-32.5 larvae per gram of faeces). A mean of 99 (SD 42.8) adult parasites were recovered in the post-mortem examinations in these eight control dogs. In contrast, no L1 at all were found in the faeces of dogs of groups 1 and 2, nor were any adult parasites detected at necropsy. Respiratory symptoms were observed in dogs of groups 2 and 3. Pathological findings in the lungs correlated with the treatment groups: in the animals of group 1, no or minimal lesions were found, while in all those of group 2 dispersed patterns of pale pink, slightly raised and consolidated foci were present in all lung lobes. In contrast, the lungs of the dogs from group 3 were severely affected: large confluent areas were hardened, raised and discoloured, with frequent haemorrhagic patches. Pneumonia, thrombi and parasites were histologically confirmed. The lung lymph nodes were regularly enlarged. Hence, imidacloprid/moxidectin spot-on effectively eliminated fourth stage larvae (L4) and immature adult A. vasorum in experimentally infected dogs and prevented patent infections. The earlier an infected dog was treated, the less severe were the pathological lesions observed in the lungs.

Bovine lamninitis: the lesions and their pathogenesis

CAREFUL postmortem examination and interpretation of findings, assisted by good clinical records, does much to throw light on the pathogenesis and nature of hoof disorders in farm animals and horses. Although there is much speculation surrounding the pathogenesis of laminitis in cattle, the principal mechanisms have largely been determined. These mechanisms and their associated lesions are described in this article.

Quantitative TaqMan ® real-time PCR assays for gene expression normalisation in feline tissues

BackgroundGene expression analysis is an important tool in contemporary research, with real-time PCR as the method of choice for quantifying transcription levels. Co-analysis of suitable reference genes is crucial for accurate expression normalisation. Reference gene expression may vary, e.g., among species or tissues; thus, candidate genes must be tested prior to use in expression studies. The domestic cat is an important study subject in both medical research and veterinary medicine. The aim of the present study was to develop TaqMan® real-time PCR assays for eight potential reference genes and to test their applicability for feline samples, including blood, lymphoid, endocrine, and gastrointestinal tissues from healthy cats, and neoplastic tissues from FeLV-infected cats.ResultsRNA extraction from tissues was optimised for minimal genomic DNA (gDNA) contamination without use of a DNase treatment. Real-time PCR assays were established and optimised for v-abl Abelson murine leukaemia viral oncogene homolog (ABL), β-actin (ACTB), β-2-microglobulin (B2M), β-glucuronidase (GUSB), hydroxymethyl-bilane synthase (HMBS), hypoxanthine phosphoribosyltransferase (HPRT), ribosomal protein S7 (RPS7), and tryptophan 5-monooxygenase activation protein, zeta polypeptide (YWHAZ). The presence of pseudogenes was confirmed for four of the eight investigated genes (ACTB, HPRT, RPS7, and YWHAZ). The assays were tested together with previously developed TaqMan® assays for feline glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and the universal 18S rRNA gene. Significant differences were found among the expression levels of the ten candidate reference genes, with a ~106-fold expression difference between the most abundant (18S rRNA) and the least abundant genes (ABL, GUSB, and HMBS). The expression stability determined by the geNorm and NormFinder programs differed significantly. Using the ANOVA-based NormFinder program, RPS7 was the most stable gene in the tissues studied, followed by ACTB and ABL; B2M, HPRT, and the 18S rRNA genes were the least stable ones.ConclusionThe reference gene expression stability varied considerably among the feline tissues investigated. No tested gene was optimal for normalisation in all tissues. For the majority of the tissues, two to three reference genes were necessary for accurate normalisation. The present study yields essential information on the correct choice of feline reference genes depending on the tissues analysed.

Recombinant FeLV vaccine: long-term protection and effect on course and outcome of FIV infection

Abstract The efficacy and the long-term protection of a recombinant feline leukemia virus (FeLV) vaccine were determined in 30 specified pathogen free cats for over 3 years. At the same time, in order to specify the effects of feline immunodeficiency virus (FIV) on the immune system, one half of the cats (n = 15) were previously infected with the Swiss isolate FIV Zurich 2. The second half of the animals (n = 15) served as non-infected controls. Eighteen (nine FIV-negative, nine FIV-positive) vaccinated and 12 (six FIV-negative, six FIV-positive) non-vaccinated cats were intraperitoneally challenged with FeLV A. Seventeen of 18 vaccinated cats were protected against persistent viremia, while ten of 12 non-vaccinated controls became infected. An increase of antibodies against FeLV SU was found in all protected cats after the challenge exposure. No difference in vaccine efficacy was found between FIV-negative and FIV-positive animals. The whole group of cats was observed for over 3 years. There were no further vaccinations during this period. CD4+ and CD8+ cell subsets, clinical outcome and time of survival of the cats were recorded. FIV-negative and FIV-positive animals were kept in two different rooms. However, FeLV-negative and FeLV viremic cats were housed together in both rooms in order to imitate a natural FeLV exposure situation. Anti-recombinant FeLV SU antibodies were measured by enzyme-linked immunosorbent assay. Although a continuous decline of antibodies was found in FeLV vaccinated cats, they remained protected against constant FeLV challenge for over 3 years. FIV infection had a stronger effect on the depression of the CD4+:CD8+ ratio than FeLV infection. Within the group of FIV-positive cats, the FeLV-vaccinated animals had significantly better survival rates as well as better clinical and laboratory parameters. FIV- and FeLV-coinfected cats showed the lowest CD4+:CD8+ ratio, mainly caused by decreased CD4+ lymphocyte counts. CD8+ lymphocytes with strong fluorescence (CD8high) disappeared and cells with weak fluorescence (CD8low) appeared instead. Prevention of coinfection by immunizing FIV-positive cats against FeLV infection improved the clinical outcome and prolonged the cats life expectancy.

Exposure of cats to low doses of FeLV: seroconversion as the sole parameter of infection

In felids, feline leukemia virus (FeLV) infection results in a variety of outcomes that range from abortive (virus readily eliminated and never detectable) to progressive infection (persistent viremia and viral shedding). Recently, a novel outcome was postulated for low FeLV infectious doses. Naïve cats exposed to faeces of persistently infected cats seroconverted, indicating infection, but remained negative for provirus and p27 antigen in blood. FeLV provirus was found in some tissues but not in the bone marrow, infection of which is usually considered a necessary stage for disease progression. To investigate the impact of low FeLV doses on young cats and to test the hypothesis that low dose exposure may lead to an unknown pathogenesis of infection without involvement of the bone marrow, 21 cats were infected oronasally with variable viral doses. Blood p27, proviral and viral loads were followed until week 20 post-infection. Tissue proviral loads were determined as well. The immune response was monitored by measuring FeLV whole virus and p45 antibodies; and feline oncornavirus-associated cell membrane antigen (FOCMA) assay. One cat showed regressive infection (transient antigenemia, persistent provirus-positivity, and seroconversion) with provirus only found in some organs at sacrifice. In 7 of the 20 remaining cats FOCMA assay positivity was the only sign of infection, while all other tests were negative. Overall, the results show that FeLV low dose exposure can result in seroconversion during a presumed abortive infection. Therefore, commonly used detection methods do not detect all FeLV-infected animals, possibly leading to an underestimation of the prevalence of infection.

A cross sectional study of prevalence, risk factors, population attributable fractions and pathology for foot and limb lesions in preweaning piglets on commercial farms in England

BackgroundIn a cross sectional study of 88 indoor and outdoor English pig farms, the prevalence of foot and limb lesions in 2843 preweaning piglets aged 1–4 weeks from 304 litters was recorded. The environmental risks for the prevalence of lesions and population attributable fractions were calculated. The risks for lesions in piglets were compared with those for limb and body lesions in their mothers. A small number of piglets with each type of lesion were examined post mortem to elucidate the pathology of the clinical lesions observed.ResultsThe prevalence of sole bruising, sole erosion, skin abrasion and swollen joints or claws in 2843 piglets was 49.4% (1404), 15.5% (441), 43.6% (1240) and 4.7% (143) respectively. The prevalence of all foot and limb lesions was higher in indoor housed piglets than in outdoor housed piglets. The prevalence of sole bruising (OR 0.3) and skin abrasion (OR 0.6) decreased with each week of age from 1–4 weeks, but there was no significant association between piglet age and the prevalence of sole erosion or swollen joints and claws. There was an increased prevalence of sole bruising (OR 3.0) and swollen joints or claws (OR 3.0) and a decreased prevalence of skin abrasion (OR 0.3, piglets ≤ 1-week old), in piglets housed on slatted floors, compared with those on solid concrete floors with bedding. There was an increased risk of sole erosion associated with piglets housed on partly slatted floors with no bedding (OR 2.4) and partly slatted floors with small amounts of bedding (OR 2.9) compared with piglets housed on solid concrete floors with bedding in all areas of the pen. Post mortem examination of feet with lesions indicated that internal pathological changes were frequently more severe than the degree of external damage suggested.ConclusionPiglets housed outdoors had a very low prevalence of foot and limb injuries. Indoors, no one floor type was ideal to minimise all piglet foot and limb injuries and the flooring requirements of sows differed from those of piglets.

Impact of flooring on the health and welfare of pigs

HOUSING for pigs reared for meat has been revolutionised over the past 50 years, and modifications in flooring have been a key component of this change. While the introduction of slatted floors that do not require manual removal of soiled bedding and dung has reduced labour requirements and production costs, solid floors are still in use on some commercial farms in Britain, particularly in older or converted buildings, and are more common in Britain than in other European pig-producing countries. Floors in pig housing can impact on the health and welfare of pigs by affecting an animals opportunity to engage in normal behaviour and increasing the risk of infectious disease and physical damage due to contact with the floor. This article highlights the impact of floor types on the prevalence of foot, limb and body lesions, and lameness in pigs, and provides typical examples of the pathology of some lesions.

Pulmonary Artery Thrombosis in Experimental Angiostrongylus vasorum Infection Does Not Result in Pulmonary Hypertension and Echocardiographic Right Ventricular Changes

BACKGROUND Dogs experimentally inoculated with Angiostrongylus vasorum develop severe pulmonary parenchymal lesions and arterial thrombosis at the time of patency. HYPOTHESIS A. vasorum-induced thrombosis results in arterial hypoxemia, pulmonary hypertension (PH), and altered cardiac morphology and function. ANIMALS Six healthy Beagles experimentally inoculated with A. vasorum. METHODS Thoracic radiographs and arterial blood gas analyses were performed 8 and 13 weeks postinoculation (wpi) and 9 weeks posttherapy (wpt). Echocardiography was done before and 2, 5, 8, 13 wpi and 9 wpt. Invasive pulmonary artery pressure (PAP) measurements were obtained 8 wpi. Two untreated dogs were necropsied 13 wpi and 4 treated dogs 9 wpt. RESULTS All dogs had patent infections at 7 wpi and clinical respiratory signs at 8 wpi. Moderate hypoxemia (median PaO2 of 73 and 74 mmHg) present at 8 and 13 wpi had resolved by 9 wpt. Echocardiographically, no evidence of PH and no abnormalities in cardiac size and function were discernible at any time point. PAP invasively measured at 8 wpi was not different from that of control dogs. Severe radiographic pulmonary parenchymal and suspected thrombotic lesions at 13 wpi were corroborated by necropsy. Most histopathologic changes had resolved at 9 wpt, but focal inflammatory, thrombotic, and fibrotic changes still were present in all dogs. CONCLUSION In experimentally infected Beagles, pulmonary and vascular changes induced by A. vasorum are reflected by marked radiographic changes and arterial hypoxemia. These did not result in PH and echocardiographic changes in cardiac size and function.

THORACIC COMPUTED TOMOGRAPHY FINDINGS IN DOGS EXPERIMENTALLY INFECTED WITH ANGIOSTRONGYLUS VASORUM

To characterize the computed tomography (CT) features of thoracic lesions caused by infection with Angiostrongylus vasorum, pre- and postcontrast CT was performed in six experimentally infected Beagles 13 weeks postinoculation and in four of these 9 weeks postchemotherapy. Findings were compared with survey radiographs and necropsy findings. A multicentric bronchoalveolar pattern more pronounced at the lung periphery was present radiographically. On CT, the predominant abnormality underlying this alveolar pattern was multiple large nodules merging to areas of consolidation, and containing air bronchograms of varying extent. These nodular changes corresponded to histopathologic granulomata, consisting mainly of macrophages, multinucleated giant cells, and lymphocytes that had accumulated around larvae and eggs. Morphologically, no bronchial changes were observed on CT or histologically. Quantitatively, however, on CT there was evidence of bronchial thickening at 13 weeks postinoculation and mild very peripheral bronchiectasia 9 weeks postchemotherapy. Regional lymph nodes were enlarged after infection, and smaller after treatment. On postcontrast CT, several suspicious intraluminal filling defects suggestive of thrombosis were found; however, the tortuosity of some pulmonary arteries seen radiographically was not present in CT images. After treatment, the consolidations and large nodules had almost completely disappeared. A remaining radiographic interstitial pattern was characterized on CT as ground-glass opacifications, subpleural interstitial thickening, subpleural lines, and interface signs. These interstitial changes reflected fibrosis as documented histopathologically. CT allowed very detailed and accurate characterization of pulmonary parenchymal lesions, bronchi, and lymphnodes and closely reflected histopathological changes.