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Abstract: It is well established that the infectious agent of scrapie can replicate in the lymphoreticular system (LRS). However, the effects of removal of LRS target tissues on the pathogenesis of the infection and the accumulation of disease-associated prion protein (PrPd) in LRS tissues on specific immune cell subsets are poorly understood aspects. To address these questions 16 ARQ/ARQ sheep were subcutaneously inoculated in the drainage area of the prefemoral lymph node with brain homogenate derived from Suffolk sheep naturally infected with scrapie. Fourteen sheep were then subjected to either early (14–17 days post-inoculation [dpi]) or late (175–201 dpi) lymphadenectomy and culled at preclinical or clinical stages of infection. Neither late nor even early lymphadenectomy prevented infection or had any effect on the accumulation of PrPd in the LRS or CNS suggesting a rapid organic dissemination of the infectious agent after inoculation. Lymph nodes from eight scrapie inoculated sheep selected on the basis of the amount of PrPd in their LRS tissues (negative, low or high) were examined for six different immune cell markers. The PrPd negative lymph nodes from two sheep with no evidence of scrapie infection showed lower numbers of cluster of determination (CD) 21 positive cells than PrPd positive nodes, irrespective of their location (hind leg or head). However, quantitative differences in the expression of this marker were not detected when comparing lymph nodes with low and high levels of PrPd accumulation, suggesting that proliferation of CD21 positive cells is related to scrapie infection, but not directly linked to the magnitude of PrPd accumulation. An additional observation of the study was that sheep that were methionin–threonine at codon 112 of the prion protein gene showed lower attack rates than methionine homozygotes (67% and 100%, respectively) and also generally lower levels of PrPd accumulation in the LRS and brain and increased survival times, suggesting an influence of such polymorphism in the susceptibility to scrapie. [Copyright &y& Elsevier]

The lymphoid, renal, pulmonary, and hepatic lesions of naturally occurring postweaning multisystemic wasting syndrome (PMWS) affected pigs have been studied by means of immunohistology. Ten conventionally reared pigs showing acute clinical signs of PMWS were selected from a farm on which animal were seronegative to porcine reproductive and respiratory virus and to Aujeszky’s disease virus. All pigs were positive in tests for porcine circovirus type 2 by ISH and IHC. Monoclonal and polyclonal antibodies to CD3, CD79α, CD45RA (3C3/9), lysozyme, SLA-II-DQ (BL2H5), and MAC387 were used to characterise cells in PMWS lesions. The most relevant changes were reduction or loss of B and T lymphocytes, increased numbers of macrophages, and partial loss and redistribution of antigen presenting cells throughout lymphoid tissues compared to uninfected controls. The characteristics of lymphoid lesions in the present study strongly suggest an immunosuppressive effect of PMWS in affected pigs. [Copyright &y& Elsevier]

Studies neuropathological changes in ovine fetuses caused by tickborne fever. Disease overview; Histopathological examination.

Describes cases of Aujeszky's disease virus (ADV) infection in fattening pigs with primary neurological disorders in Great Britain. Age of pigs; Mortality rate; Physical condition of animal; Detection of ADV antigen by routine immunohistochemistry technique; Incidence of severe meningoencephalitis; Localization of the ADV antigen.

Abstract: Immunohistochemistry (IHC) is a highly specific and sensitive technique which is now available to aid in the confirmation of diagnosis of many diseases of sheep. When available for use on formalin fixed, paraffin wax-embedded tissue samples, it can be used widely for prospective cases as well as on retrospective studies on archive material. However, for each disease it is vital to select the most appropriate tissue organ samples, to fix them correctly and to be aware of potential limitations of each individual immunohistochemical methodology. In this paper we present a review of many of the diseases of sheep for which specific IHC has been reported including the sources of the reagents and technical aspects of the methodologies. [ABSTRACT FROM AUTHOR]

Abstract: The identification of Louping ill virus (LIV) in clinical specimens has been routinely achieved by virus isolation using susceptible pig kidney cells and subsequent serological analysis. While this method is sensitive and detects infectious virus, it is relatively labour intensive and time-consuming. In view of the veterinary and potential medical importance of LIV, a rapid and precise detection method for routine use that employs the TaqMan reverse transcription polymerase chain reaction (RT-PCR) has been developed to detect LIV RNA extracted from field samples. The TaqMan assay was evaluated against virus isolation using 22 cell culture grown LIV isolates, which had previously been partially characterised by sequencing, and material from 63 suspect field cases. Histopathological and/or serological reports were available for 39 of the suspect cases, providing additional diagnostic information to evaluate the results obtained from the TaqMan RT-PCR assay. The TaqMan assay was as sensitive as the cell culture infectious virus assay currently used and had the advantage that it was able to detect LIV in clinical specimens from which infectious virus could not be isolated possibly due to the presence of high levels of LIV antibody. [Copyright &y& Elsevier]

The aim of the present study was to investigate and correlate the cell-mediated immune response and pathological changes at the maternal-fetal interface of Neospora- challenged pregnant cattle previously immunized with live and inactivated experimental vaccines. Pregnant heifers naïve to Neospora caninum were divided in 5 groups of 4 animals, each one immunized before mating: Group A heifers were intravenously (iv) immunized with 6.25 × 10 7 live tachyzoites of the NC-6 strain; group B heifers were immunized twice subcutaneously (sc) 3 weeks apart with native antigen extract of the NC-6 strain formulated with ISCOMs; group C heifers were sc immunized twice 3 weeks apart with three recombinant proteins (rNcSAG1, rNcHSP20, rNcGRA7) of the NC-1 strain formulated with ISCOMs; group D heifers were sc injected with sterile phosphate-buffered saline (PBS) and group E heifers received sc ISCOM-matrix (ISCOMs without antigen). All groups were iv-challenged with 4.7 × 10 7 NC-1 tachyzoites at 70 days of gestation. Heifers were culled at day 104 of gestation and placentomes were examined to evaluate lesions and local cellular immune responses using histopathology, immunohistochemistry and real time-PCR. Immunohistochemistry was performed using bovine leucocyte specific antibodies. Cytokine expression and levels (IFN-γ, IL-4, IL-10, IL-12 and TNF-α) were measured using real-time reverse transcription-PCR and ELISA, respectively. Minimal inflammation was observed in group A placentomes; while placentomes from group B, C, D and E had moderate to severe infiltration with CD3 + , CD4 + , γδ-T cells, CD8 + cells and macrophages being more numerous in groups B and E placentomes, when compared with groups C and D ( P < 0.001). Cytokine levels were significantly increased in the caruncles of animals of groups B and C in comparison with the other animal groups ( P < 0.001). The results from this study showed that the strongest cellular immune responses were observed in the placentomes of animals that were immunized with inactivated vaccines (groups B and C) and in the placentomes of animals that were sc-sham-inoculated (groups D and E). On the other hand, animals that were immunized with live tachyzoites showed a milder immune cell infiltration to the placenta possibly due to the existence of a protective systemic maternal immune response that helped to minimize N. caninum infection at the maternal-fetal interface. [ABSTRACT FROM AUTHOR]

The article discusses the respiratory infection caused by acute Sarcocystis (S) tenella infection in sheep. It states that the infection of S tenella is clinically silent and results cysts formation in skeletal and cardiac muscle. It features a clinical case involving a fatal ovine protozoal pneumonia with S tenella which is confirmed as the main cause of pulmonary lesions found in the group of 150 five- to seven-month-old sheep that has been directly purchased in October 2011 from a farm.

Aim: Neuropathological changes classically associated with sheep scrapie do not always correlate with clinical disease. We aimed to determine if selected neuromodulatory responses were altered during the course of the infection as it has been described in Creutzfeldt-Jakob disease and experimental bovine spongiform encephalopathy. Methods: Hemi-brains from healthy sheep and natural scrapie cases at two stages of infection were examined for biochemical alterations related to the expression of type I metabotropic glutamatergic receptors (mGluR1) and type I adenosine receptors I (A1R), and of selected downstream intermediate signalling targets. Immunohistochemistry for different scrapierelated neuropathological changes was performed in the contralateral hemi-brains. Results: PrPd deposition, spongiform change, astrocytosis and parvalbumin expression were significantly altered in brains from clinically affected sheep compared with preclinical cases and negative controls; the latter also showed significantly higher immunoreactivity for synaptophysin than clinical cases. Between clinically affected and healthy sheep, no differences were found in the protein levels of mGluR1, while phospholipase Cb1 expression in terminally ill sheep was increased in some brain areas but decreased in others. Adenyl cyclase 1 and A1R levels were significantly lower in various brain areas of affected sheep. No abnormal biochemical expression levels of these markers were found in preclinically infected sheep. Conclusions: These findings point towards an involvement of mGluR1 and A1R downstream pathways in natural scrapie. While classical prion disease lesions and neuromodulatory responses converge in some affected regions, they do not do so in others suggesting that there are independent regulatory factors for distinct degenerative and neuroprotective responses. [ABSTRACT FROM AUTHOR]

Abstract: The host–pathogen interaction is as a key feature during the formation of tissue cysts of Toxoplasma gondii within intermediate hosts. In this study, we investigated whether oral infection of lambs with T. gondii oocysts may be used as an experimental model in sheep to study this interaction, with the main objective being to detect the presence and distribution of lesions and parasite within different organs at different time points after oral infection. Lambs were infected with 5×103 and 5×105 sporulated T. gondii oocysts and culled at 2, 3, 5 and 6 weeks post-infection (WPI). During the infection, rectal temperature of the animals and serological antibodies against T. gondii were monitored. The presence of inflammatory lesions and parasite were evaluated through histological and immunohistochemical methods at different organs (brain, liver, lung, heart and lymph nodes). The lambs showed no clinical signs other than fever, and lesions appeared mainly in the brain, characterized by glial foci and perivascular cuffs, and in the heart, denoted by foci of interstitial myositis. Tissue cysts and tachyzoite-like structures were observed at all time points studied in the brain, where together with the glial foci they appeared mainly in the cerebral cortex of the forebrain and in the midbrain, but also in the heart, lung and lymph nodes. This study shows that oral infection with sporulated oocysts in lambs may provide a model for investigating the host–parasite interaction in situ during the development of tissue cysts. [Copyright &y& Elsevier]

The frequency and the distribution of apoptotic cells were investigated in formalin-fixed paraffin-embedded lymphoid tissues from healthy conventional pigs at four different ages (6 days, 2 months, 3.5 months and 5 months). Samples of tonsil, mesenteric lymph node, spleen, thymus and Peyer’s patches were histologically processed and apoptosis evaluated with the TUNEL reaction and cleaved caspase-3 immunohistochemistry. In each technique, quantification of positive labelling was done for each particular lymphoid tissue area. The labelling pattern and distribution were similar for TUNEL and cleaved caspase-3. TUNEL stained mainly apoptotic bodies inside macrophages, but signal was also seen in free apoptotic bodies and in the nuclei of lymphocyte-like cells. The anti-cleaved caspase-3 antibody labelled mainly nuclei of lymphocyte-like cells. All tissues presented a similar distribution pattern of apoptosis, except for the 6-day-old group. In this group, a scattered distribution of positive cells was detected in tonsil, lymph node and spleen. In the tonsil and mesenteric lymph nodes from the older pigs, follicular areas presented higher amounts of positive cells than interfollicular areas. Moreover, the splenic white pulp showed more positive reaction than the red pulp, especially when they included germinal centres. In all groups, the follicular areas of ileal Peyer’s patches presented more labelled cells than the dome and the lamina propria. In the thymus, the higher apoptotic rates were found in the cortex. In general, TUNEL yielded higher rates of positive cells than cleaved caspase-3 immunolabelling. A good correlation between the two techniques was found for thymus, tonsil and mesenteric lymph node, but not for Peyer’s patches and spleen. This study describes a detailed histochemical characterization of apoptosis in pig lymphoid tissues using TUNEL and a cleaved caspase-3 immunolabelling at different ages. Moreover, our results indicate that TUNEL and cleaved caspase-3 techniques can be equivalent only when tissues have a high or low levels of apoptosis, since a considerable discrepancy was found in intermediate situations. Data from this study should be useful for future comparative studies under disease conditions. [Copyright &y& Elsevier]

The article details the first description of a case of atypical scrapie in a sheep from a flock in Scotland. A four-year-old Cheviot ewe that had lambed one week previously was seen to be ataxic and anorexic for two days before dying. The article describes the cerebellum of a sheep with atypical scrapie.