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Copper toxicity II.

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Animals↗

Copper toxicity. I.

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Animals↗

Cloning of a unique sequence specific to isolates of type B:2 Pasteurella multocida.

Two Carter type B Pasteurella multocida isolates, Izatnagar 52 and 25, isolated from cases of haemorrhagic septicaemia (HS), were used in a modified subtractive hybridisation technique with the specific aim of cloning unique DNA sequences related to the pathogenesis of HS. Biochemical and protein analyses have shown these isolates to be similar, but reports indicate that they have differences in pathogenicity. The subtracted inserts were screened against genomic DNA from a wide range of P multocida isolates, with two distinct fragments demonstrating specific hybridisation with Carter type B isolates that cause HS. No identity was observed with either Carter type E isolates or non-HS type B strains. The clones were sequenced and a search of the GenBank database revealed significant identity of the clone A3b (296 nt) to P haemolytica lipoprotein, whereas there was no significant identity with 6b (956 nt). Both these fragments had a high level of identity (72.8 to 76.9 per cent) to the H influenzae Rd genome.

Animals↗

In vitro isolation and cultivation of Cowdria ruminantium under serum-free culture conditions.

Three stocks of Cowdria ruminantium, the causative agent of heartwater in domestic ruminants, were propagated in bovine endothelial cells in a serum-free culture medium. The Vosloo, Welgevonden and Senegal stocks were propagated for a period of more than 203, 134, and 43 days, respectively. Two of the C ruminantium stocks (Vosloo and Senegal) were also successfully initiated under serum-free culture conditions. The serum-free medium consisted of a modified HL-1 medium. The Senegal stock was successfully propagated in Dulbecco's modified Eagle's medium nutrient mixture Ham F-12 containing 10 per cent fetal bovine serum.

Animals↗

Aspects of emergency vaccination against foot-and-mouth disease.

Emergency vaccination is one of several measures which may be deployed to control outbreaks of foot-and-mouth disease. It can be a valuable adjunct to the application of the essential zoosanitary controls which must include rapid diagnosis, tracing, movement control and disinfection and which may also include slaughter of infected and in-contact animals and their safe disposal. Criteria which determine the successful application of emergency vaccination include access to vaccine(s) that (i) contain virus strain(s) of sufficient antigenic relatedness to the outbreak strain(s) (ii) are of the required type of vaccine formulation (iii) have acceptable innocuity and potency (iv) have appropriate availability, including quantity and immediacy of supply and (v) meet considerations of cost. Contingency planning should include provision for emergency vaccination and must address the complex decisions of not only when, where, and how to apply vaccine but also its economic consequences. Computer modelling may be a useful aid to cost benefit and decision support systems in this context. Planning must be detailed and regularly reviewed and should ensure, (i) that the legal and financial aspects are catered for (ii) that any contractual supply agreements are in place (iii) that information is collected and its currency maintained on the species, numbers and whereabouts of susceptible livestock (iv) that vaccination teams are formed and trained (v) that the vaccine cold chain is established and maintained (vi) that supplies of vaccination equipment are held in readiness and (vii) that briefing materials are available to inform the various stakeholders on relevant aspects of emergency vaccination. Knowledge concerning the characteristics and performance of emergency vaccines is summarised and areas identified for further research.

Animals↗

Ring vaccination against foot-and-mouth disease.

The study of the available information, notably after the epizootic of foot-and-mouth disease (FMD) which raged in Western Europe in 2001, shows that, in the current conditions of the international sanitary rules relative to this disease, in a FMD-free country of Western Europe accidentally infected, ring vaccination is a solution which, with regard to preventive slaughter, contains more inconveniences (notably economic) than advantages. The appeal to ring vaccination would be interesting only as far as the international sanitary rules would be modified by taking into account the results expected from the coordinated use of highly purified vaccines and differential research kits (vaccine-linked versus infection-linked antibodies). Propositions are this way made.

Animals↗

Efficacy of DNA vaccination by different routes of immunisation in sheep.

DNA vaccination, delivered through various routes, has been used extensively in laboratory animals. Few studies have focused on veterinary species and while results obtained in laboratory animals can often be extrapolated to veterinary species this is not always the case. In this study we have compared the effect of the route of immunisation with DNA on the induction of immune responses and protection of sheep to challenge with live Corynebacterium pseudotuberculosis. Intramuscular injection of plasmid DNA encoding an inactivated form of the phospholipase D (PLD) antigen linked to CTLA4-Ig resulted in the induction of a strong memory response and sterile immunity following challenge in 45% of the animals. In contrast, gene gun delivery or subcutaneous (SC) injection of the DNA vaccine induced comparatively poor responses and insignificant levels of protection. Thus, DNA vaccine efficacy in sheep is strongly influenced by the route of vaccination. Amongst intramuscular vaccinates, protected sheep had significantly elevated IgG2 responses compared to unprotected animals, while both subgroups had equivalent IgG1 levels. This suggests that the presence of IgG2 antibodies and hence a Th1-like response, induced by the DNA vaccine gave rise to protective immunity against C. pseudotuberculosis.

Animals↗

Cutaneous hypersensitivity reactions to Psoroptes ovis and Der p 1 in sheep previously infested with P. ovis--the sheep scab mite.

We have previously shown that infestation with Psoroptes ovis induces an IgE response and intense tissue eosinophilia, typical of a Type I hypersensitivity response [Parasite Immunol. 22 (2000) 407]. Intradermal tests (IDSTs) suggest that there are also delayed and Arthus-type responses to this parasite. In order to study the nature of ovine cutaneous reactions to P. ovis, naïve controls and experimentally infested sheep (n = 5) were challenged intradermally with mite antigen. Challenge elicited immediate (P < 0.001) and delayed (P < 0.005) wheal reactions in sensitised sheep. At 6 (P < 0.02) and 30 h (P < 0.001) the predominant infiltrating cells were eosinophils. To explore the role of circulating antibodies, naïve sheep (n = 5) were subjected to Prausnitz-Kustner (PK) tests. These elicited immediate (P < 0.02) but not delayed wheal reactions. At 6 h eosinophils (P < 0.001) dominated the infiltrate. These results suggest that P. ovis allergens provoke an IgE-dependent immediate and late phase response and a cell-mediated eosinophil-rich delayed-type hypersensitivity response (ER-DTH).

Animals↗

Intestinal exposure to a parasite antigen in utero depresses cellular and cytokine responses of the mucosal immune system.

The response of the mucosal immune system of 4-6-week old lambs to viable Trichostrongylus colubriformis larvae was compared in two groups of animals, one exposed to T. colubriformis antigen and the other to saline while in utero. Exposure to larval antigen two-thirds of the way through gestation resulted in significant reduction in the frequency of jejunal goblet cells and of ileal eosinophils, CD 1b(+) antigen-presenting cells and CD4(+), CD5(+) and CD8(+) cells. However, it resulted in a significant increase in the jejunal CD8(+) response to postnatal challenge. The expression of the cytokines TNF-alpha and IL-1 beta in the ileum, and of jejunal NSE, was significantly reduced by in utero exposure, whereas those of jejunal TNF-alpha and ileal TGF-beta were increased. The observed changes in cellular and cytokine responses to challenge with viable larvae, in those lambs previously exposed in utero, indicated that the intestinal mucosal immune system remains susceptible to down-regulation until considerably later in foetal development than is the case for other components of the immune system.

Administration, Oral↗

Serum antibodies to Dicrocoelium dendriticum in sheep from Sardinia (Italy).

An indirect enzyme-linked immunosorbent assay (ELISA) with Dicrocoelium dendriticum excretory/secretory antigens was used to evaluate the presence of serum antibodies against the trematode in 738 sheep randomly chosen in Sardinia (Italy). Coprological sedimentation was used to discover egg-output. Seropositivity was detected in 86.2% tested sheep, whereas faecal prevalence was 6.7%; all that were faecal-positive also were ELISA-positive.

Animals↗

Efficacy of an ovine caseous lymphadenitis vaccine formulated using a genetically inactive form of the Corynebacterium pseudotuberculosis phospholipase D.

Caseous lymphadenitis (CLA) is an economically significant disease of sheep caused by the gram-positive bacterium Corynebacterium pseudotuberculosis. CLA vaccines are currently formulated using formalin inactivated culture supernatants that are rich in the C. pseudotuberculosis phospholipase D (PLD) exotoxin. One alternative to chemical detoxification is to inactivate the PLD genetically. This procedure not only provides a means to remove an onerous chemical treatment step but also the opportunity to increase gene expression, therefore improve protein yields. Using site-specific mutagenesis the C. pseudotuberculosis PLD was inactivated by substituting a serine residue at histidine 20 within the enzyme active site. CLA vaccine formulated using genetically inactivated PLD protected 44% of sheep against C. pseudotuberculosis challenge compared with 95% protection offered by the formalin inactivated preparation. Since there was no apparent difference in immune response mounted by vaccinated sheep the reason for this variation in vaccine efficacy remains unclear. Although genetic inactivation can be a convenient means to produce toxoid vaccines its use to develop a new CLA vaccine provided no net benefit over the conventional formulation.

Animals↗