Heterologous challenge with porcine reproductive and respiratory syndrome (PRRS) vaccine virus: no evidence of reactivation of previous European-type PRRS virus infection.

In Denmark, a porcine reproductive and respiratory syndrome virus (PRRSV) control programme, comprising vaccination of seropositive herds with a live American type PRRSV vaccine, was started in 1996. In several of these herds, spread of vaccine virus from vaccinated 3-18 week old pigs to non-vaccinated sows was demonstrated by the isolation of vaccine virus from fetuses and stillborn piglets. Surprisingly, sows infected with the American type vaccine strain consistently exhibited significantly stronger serological responses towards European type PRRSV than American type PRRSV. In order to elucidate whether the unexpectedly strong serological reaction towards European-type PRRSV in American type PRRSV infected sows was due to a booster reaction, or reactivation of an unrecognized, latent infection in the sows with European type PRRSV, a challenge study with the vaccine was carried out. In this study, the stronger serological response towards European type PRRSV than towards American type PRRSV was reproduced, and reactivation of the previous natural infection with European PRRSV could neither be demonstrated by virus isolation nor by RT-PCR. So, the increase in antibody titers towards European PRRSV in previously European PRRSV infected pigs after challenge with the vaccine strain seems to be the result of a boosting effect on the immune system, induced by the heterologous vaccine PRRSV strain.     

Congress report on progress in pestivirus virology

Summary

This mini‐review highlights new information on various research aspects presented by specialists from all over the world at the 4th Pestivirus meeting held in Giessen (Germany) from March 15–19, 1999. Especial attention is paid towards differences in humeral and cellular immune response of naive and persistently infected calves with BVDV, and towards BVD eradication programmes m the Scandinavian countries.

The development of techniques for an early diagnosis of CSF in live pigs and the progress on both sub‐unit and MLV marker vaccines against this disease are reported.     

The hardness of horn in different segments of the bovine claw

Hardness of bovine hoof horn was tested as ball indentation hardness and as shore D hardness post mortem in different segments of the hoof wall, in the sole and the hard bulb of sound claws of 10 Austrian Holstein Friesian cows. Both methods of hardness determination showed corresponding results, with shore D hardness between 52.2 and 63.9 hardness units (hu) and ball indentation hardness between 11.2 N/mm2 and 24.3 N/mm2. Bovine hoof horn becomes significantly softer from the coronary band towards the weight bearing border (vertical decrease) and from the dorsal wall towards the heel (horizontal decrease). Decreasing hardness was associated with decreasing dry matter content. Measurements of the claw capsule showed thickness of the hoof wall increasing from the coronary border towards the sole. In dorsopalmar/-plantar direction, bovine hoof wall at the weight bearing border decreases towards the heel.     

The impact of quorum sensing on the virulence of Aeromonas hydrophila and Aeromonas salmonicida towards burbot (Lota lota L.) larvae

In this study, the link between quorum sensing in Aeromonas spp. and its virulence towards burbot (Lota lota) was investigated. High mortality occurred in burbot juveniles challenged with Aeromonas salmonicida HN-00, but not in juveniles challenged with Aeromonas hydrophila AH-1N. Meanwhile, both A. hydrophila AH-1N and A. salmonicida HN-00 were virulent towards larvae. The effect of quorum sensing on the virulence of A. hydrophila AH-1N towards burbot larvae was further investigated using quorum sensing mutants (N-(butyryl)-L-homoserine lactone production and receptor mutants). Challenge with these mutants resulted in higher survival of burbot larvae when compared to challenge with the wild type, and the addition of the signal molecule N-butyryl-L-homoserine lactone restored the virulence of the quorum sensing production mutant. Moreover, quorum sensing inhibitors protected the burbot larvae from both Aeromonas strains. Finally, the freshwater micro-algae Chlorella saccharophila and Chlamydomonas reinhardtii, which are able to interfere with quorum sensing, also protected burbot from the pathogens. However, QS interference was unlikely to be the only mechanism. This study revealed that the virulence of Aeromonas spp. towards burbot is regulated by quorum sensing and that quorum sensing inhibitors and micro-algae are promising biocontrol agents.     

Relationship between aggressive and avoidance behaviour by dogs and their experience in the first six months of life

The early experiences of dogs showing signs of avoidance behaviour or aggression were compared with those of dogs from the same clinical population that did not show such behaviour. The occurrence of each behavioural sign was tested for its association with the dog's maternal environment, the environment it experienced between three and six months of age, and the age at which it had been acquired. Non-domestic maternal environments, and a lack of experience of urban environments between three and six months of age, were both significantly associated with aggression towards unfamiliar people and avoidance behaviour. Aggression during a veterinary examination was more likely in dogs from non-domestic maternal environments. There was no significant association with either environment for aggression towards familiar people, or towards dogs.     

Airborne transmission of classical swine fever virus under experimental conditions

Sixty-one pigs were housed in an isolation unit with three compartments and five pens. Each compartment had its own ventilation system resulting in air currents flowing from compartment A (pens 1 to 3) towards compartment B (pen 4), but not towards compartment C (pen 5). Classical swine fever virus was introduced by the experimental inoculation of one pig in the middle pen (pen 2) of compartment A. The virus infected the pigs in pen 4, following the prevalent air currents, and the compartmentalisation had only a retarding effect on the transmission of the virus. The absence of infection in the pigs in pen 5, which was not different from pen 4 except for the ventilation system, indicates that the spread of virus was affected by the air currents.     

Differential reactivity of a monoclonal antibody directed to the membrane protein of porcine reproductive and respiratory syndrome virus.

A monoclonal antibody (2C12) against the 19 kDa membrane (M) protein of a Canadian isolate of porcine reproductive and respiratory syndrome (PRRS) virus was produced. By indirect immunofluorescence (IIF) cytoplasmic fluorescence was observed in infected cells, but the pattern of fluorescence was generally different and intensity was weaker than that observed using the nucleocapsid protein-directed monoclonal antibody SDOW17. When tested by IIF towards a total of 26 PRRS virus isolates from Canada, 122 isolates from the US and 13 isolates from Europe the 2C12 MAb reacted with all the North American isolates tested including the VR-2332 isolate and the vaccine (RespPRRS) isolate. However no reactivity was observed towards the European isolates tested including the Lelystad virus. This reactivity pattern suggests that the epitope recognized by this MAb on the M protein of PRRS virus appears highly conserved among North American isolates but absent or weakly expressed on European isolates of PRRS virus.     

Attraction of male Rhipicephalus appendiculatus ticks to females in relation to feeding

Five experiments were carried out on the movement of partially fed male Rhipicephalus appendiculatus ticks on rabbits towards other ticks of the same species. Male ticks pre-fed for 5 days were attracted towards pre-fed females, slightly attracted towards other pre-fed males, but not attracted towards nymphal ticks or recently relinquished feeding sites of adult or nymphal ticks. Female ticks fed for 5 days or longer were particularly attractive to male ticks which had also fed for 5 days or longer. Eight-week-old female ticks were most attractive to males, and 8-week-old male ticks most attracted to females. It is suggested that the male ticks may be attracted to the females by means of a sex pheromone, as has been shown in other ixodid tick species.     

A study in animal ethics in New Brunswick

Society uses animals in ever-increasing numbers and ways, providing ethical challenges. Decisions about animal use are guided by the social consensus ethic towards animals. Because there is no clear social consensus ethic, these decisions are difficult. Society's ethic is changing and a "new ethic" towards animals is emerging. This study addressed the need to better understand society's ethics towards animals. Qualitative research methodology (focus groups) was used to study 7 different animal-interest groups. Qualitative data analysis was computer-aided. The group ethical position towards animals of its own group interest was determined for each group. The animal welfare, companion animal, and veterinary groups took Rollin's Position, a position based on both the Utilitarian and the Rights Principles; the farmer and trapper groups the Utilitarian/Land Ethic position, a dual position based on actions producing the greatest amount of pleasure and the least amount of pain for the greatest number, and preserving the integrity, stability, and beauty of the biotic community; the hunter group the Utilitarian/Judeo-Christian position, a dual position based on actions producing the greatest amount of pleasure and the least amount of pain for the greatest number, and having dominion over animals; and the naturalist group took Rollin's Position/Land Ethic. All these groups perceived medium to extreme ethical responsibility towards animals of their own group's interest that are used by others. The study showed that the predicted "new ethic" towards animals is in New Brunswick society and it is Rollin's Position.     

Enhanced virulence of Staphylococcus aureus from bovine mastitis induced by growth in milk whey

The virulence towards mice of Staphylococcus aureus strains from bovine mastitis was enhanced upon growth in milk whey compared to homologous organisms grown in tryptic soy broth (TSB). In the mouse mastitis model, S. aureus grown in milk whey caused more severe lesions than homologous strains grown in TSB. Staphylococcus aureus strain F1440 grown in milk whey induced 75% mortality and local necrotic reaction in subcutaneously inoculated mice, whereas the homologous strain grown in TSB caused only 5% mortality and slight skin reaction. Extracellular capsule on milk whey-grown, S. aureus could not be demonstrated. However, diffuse type colony morphology could be correlated with an increased virulence of S. aureus towards mice.     

Die Differenzierung der Oberflächenzellinie im Labmagen adulter Rinder * The Differentiation of the Surface Mucous-cell Line in the Abomasum of the Adult Cow

The differentiation of the surface mucous-cell lineage during physiological cell renewal was investigated using light and electron microscopy in the abomasal mucosa of adult cattle. The surface mucous cells constitute a morphologically and functionally heterogeneous population, whose members correspond to different developmental stages, arranged in a distoproximal gradient from the depth of the pit towards the free luminal surface. The cell lineage comprises immature pre-pit cells near the proliferative isthmus, mature pit cells within the foveola, and older interfoveolar cells lining the free surface. Ultrastructurally, differentiation can be traced towards a predominantly mucus-producing cell type and finally towards a surface-protective cell variant, which degenerates in situ and is extruded into the lumen without affecting epithelial integrity.     

Lateral musculature in the whitemouth croaker (Micropogonias furnieri): its characterization with respect to different gonadal conditions

Histochemical and ultrastructural studies were performed on the lateral musculature from individual female whitemouth croaker, Micropogonias furnieri, at the anterior, medium and posterior regions. Based upon histochemical myosin-ATPase (m-ATPase) determination, diverse types of red, pink and white fibres were discerned. Red muscle had abundant mitochondria and stained intensely for aerobic enzymes, white muscle scarcely stained for the same enzymes and pink muscle responded in an intermediate manner. Both white and pink muscle had few mitochondria. The relative proportion of red muscle increased towards the caudal region; pink muscle diminished towards this region and white muscle modified its proportion only in the anterior region. m-ATPase activity showed differences in relation to the gonadal condition along the body, particularly in the white fibres at the anterior and medium regions.     

Attitudes of European citizens towards pig production systems

The objective of the study is to map citizen attitudes towards pig meat production systems, and to investigate whether these attitudes associate with pork and pork product consumption. A conjoint experiment was carried out with empirical data collected from 1931 individuals in four European countries with higher-than-average per capita meat consumption (Belgium, Denmark, Poland and Germany). The experiment was based on the following pig farming characteristics: herd size, housing and floor type, efforts to reduce the impact of the production system on the environment, animal feed designed for producing pork with specific fat content, and finally the preferred quality characteristics of the pork end-product. The results of the conjoint analysis were used for a subsequent cluster analysis in order to identify European citizen clusters. Respondents' socio-demographic profile, attitudes towards issues that are expected to influence the way people evaluate pig meat production systems, and consumption frequency of various pork products are used as background information to identify segment profiles. Pork appears to play a substantial role as a part of the diet for most respondents in the four countries of this study. The results of the conjoint experiment at the sample level show that people assigned most importance to animal and environmental well-being as criteria to discriminate between “good” and “bad” pig production practices, despite the fact that their attitudes towards environmental protection, animal welfare and industrial food production were only moderately strong. Moreover, the results of the cluster analysis allowed small-sized, clear-cut clusters of citizens to appear, which pay attention to specific pig farming attributes. In conclusion, attitudes towards environment and nature, animal welfare and the need for an environment-friendly food production were indeed related to citizens' specific attitudes towards pig farming at the cluster level. However, the relationship between citizenship and consumption behaviour was found to be weak. What people think in their role as citizens related to pig production did not appear to significantly influence their pork consumption choices.     

Perceptions of veterinarians and clients to expressions of clinical uncertainty

OBJECTIVES: The aim of this study was to explore the attitudes of veterinarians and clients towards expressions of clinical uncertainty. METHODS: Questionnaires that assessed the respondent's attitudes towards expressions of clinical uncertainty were completed by clients at six small animal practices. In addition, questionnaires that evaluated what veterinarians thought their client's attitudes would be towards expressions of clinical uncertainty were completed by veterinarians. The responses from clients and veterinarians were statistically compared. RESULTS: Veterinarians significantly underestimated the desire of clients to be told about uncertainties in treatment and significantly overestimated how the expression of uncertainty would generally reduce client confidence. Veterinarians significantly overestimated the loss of client confidence resulting from saying "I am not sure about this" and from asking a nurse for advice. Both clients and veterinarians considered that verbal expressions of uncertainty would lead to a greater reduction in client confidence than behavioural expressions of uncertainty. CLINICAL SIGNIFICANCE: This study suggests that most clients want to be told about their veterinarian's clinical uncertainties, and how this uncertainty is expressed can markedly influence client confidence.     

In vitro reactivity and growth inhibition of EPEC serotype O111 and STEC serotypes O111 and O157 by homologous and heterologous chicken egg yolk antibody

IgY is a chicken egg yolk antibody which has been used for treatment and prophylaxis of gastrointestinal infections. Our aim was to verify if IgY obtained from chickens immunized with EPEC O111, STEC O111 and STEC O157 is able to show in vitro reactivity and biological activity towards the three bacteria. IgY was obtained from eggs laid before and after immunization with each bacterium. The preparations of IgY anti-EPEC O111 and anti-STEC O111 shared high reactivity detected by ELISA and growth inhibition ability towards both bacteria EPEC O111 and STEC O111. Nevertheless, the preparation of IgY anti-STEC O157 showed high reactivity and growth inhibitory effect only towards the homologous strain. Our results showing in vitro biological activity of IgY reinforce its use as an alternative for the treatment or prophylaxis of E. coli infections and encourage the development of in vivo studies for a possible future human therapeutic use.     

The prebiotic potential of brewers’ spent grain on livestock’s health: a review

Tropical Animal Health and Production - The increasing interest from the feed as a source of energy towards specific nutrient-yielding compounds in feeds is amongst the latest developments from...     

Effect of glucocorticoids on cows suspected of subclinical infection with M. paratuberculosis

Glucocorticoids were administered to 10 heifers suspected of subclinical infection with Mycobacterium paratuberculosis. Three animals remained untreated. M. paratuberculosis was isolated from the internal organs of 2 animals after this treatment but not from any of the control group. Delayed type hypersensitivity and lymphocyte reactivity towards Johnin and purified protein derivates of M. avium and M. bovis were depressed. A sharp increase in total leucocyte count, due to an increase in neutrophil numbers, occurred. In the three untreated animals these parameters did not change during the experiment. A decrease of specific immunological reactivity towards M. paratuberculosis occurred, but not to such an extent that clinical disease developed.     

Using the genomic relationship matrix to predict the accuracy of genomic selection

Estimated breeding values (EBVs) using data from genetic markers can be predicted using a genomic relationship matrix, derived from animal's genotypes, and best linear unbiased prediction. However, if the accuracy of the EBVs is calculated in the usual manner (from the inverse element of the coefficient matrix), it is likely to be overestimated owing to sampling errors in elements of the genomic relationship matrix. We show here that the correct accuracy can be obtained by regressing the relationship matrix towards the pedigree relationship matrix so that it is an unbiased estimate of the relationships at the QTL controlling the trait. This method shows how the accuracy increases as the number of markers used increases because the regression coefficient (of genomic relationship towards pedigree relationship) increases. We also present a deterministic method for predicting the accuracy of such genomic EBVs before data on individual animals are collected. This method estimates the proportion of genetic variance explained by the markers, which is equal to the regression coefficient described above, and the accuracy with which marker effects are estimated. The latter depends on the variance in relationship between pairs of animals, which equals the mean linkage disequilibrium over all pairs of loci. The theory was validated using simulated data and data on fat concentration in the milk of Holstein cattle.     

Microvasculature of the Foal Metacarpus

The developing vascular architecture of the metacarpus of the foal was studied by a bone-clearing technique. For this technique Microfil was used to demonstrate the periosteal, cortical and medullary vessel distribution. Superficial and deep periosteal vessels were observed. A stratified arrangement of cortical vessels, derived from medullary vessels was shown. Ascending and descending medullary arteries originated from the nutrient artery and traversed the bone medulla towards the epiphyses. Along their course through the medulla, smaller vessels were given off that ran towards the metaphyses and gave rise to numerous sinusoids. Vessels were observed crossing the growth plate in the distal metacarpus. By using the information obtained from this investigation further studies can be initiated that could determine the periosteal contribution to cortical blood flow as it relates to sequestration of bone.     

Attitudes of the public towards dogs and cats as companion animals

A questionnaire was used to collect information on attitudes toward dogs and cats as companion animals. Thirty-nine attitudinal questions on dogs were grouped using principal component analysis (PCA) into six independent major factors; whereas, 38 items on cats were grouped using principal component analysis (PCA) into four independent major factors. In addition, 18 items which did not fit the PCA model but that were related to the respondents' attitudes towards dogs and cats as companion animals were analysed separately. The hypotheses tested, using analysis of variance (ANOVA) were that there was no significant relationship between the factors and five variables, i.e., pet ownership, age or sex of the respondents and their like or dislike of either dogs or cats. The respondents' like or dislike of dogs or cats influenced their attitudes towards ownership of companion animals. Furthermore, nonowners stated they derive minimal value from a dog or cat as a pet and viewed the negative characteristics of the animal itself per se as a more important factor in determining ownership. Female respondents were more emotionally involved and younger owners derived more of a feeling of importance-vanity from dog or cat ownership.