Prospects for a novel vaccine against tuberculosis

The development of a new and improved vaccine against tuberculosis has in the last 10 years been accelerated tremendously from the completed Mycobacterium tuberculosis genome and the progress in molecular biology. This has resulted in the identification of a large number of antigens with potential in tuberculosis vaccines. The next phase of this work has now started--putting the most relevant molecules back together as fusion molecules and cocktails. This requires carefully monitoring of aspects as immunodominance, recognition in different populations as well as the influence of different adjuvants and delivery systems. The most advanced of these vaccines such as the fusion between ESAT6 and Ag85B have been evaluated in a range of animal models including non-human primates and are now entering into clinical trials. For these vaccines to be successfully implemented in future vaccination programmes it is necessary to understand the immunological background for the failure of BCG and optimize the vaccines for their ability to boost the immuno-response primed by BCG.     

Serological Investigations of Leptospiral Deoxyribonucleases

Enzymoserological comparison of a selection of leptospira strains tested with sera from rabbits immunized with unpurified DNase of Leptospira interrogans, serotype canicola, indicates the production of DNase of serologically very similar properties by the serotypes canicola, autumnalis, icterohemorrhagiae and pomona. The DNase produced by serotype hyos was serologically different from the others, while the serotypes grippotyphosa and bataviae did not produce DNases at all. The method used made it possible to differentiate between leptospiral DNase and normally occurring DNases in the serum samples. Neither leptospira DNase nor specific leptospira-DNase-antibodies could be detected in dog sera with high agglutinationlysis titres after natural infection.     

Phenotypic and genetic relationships between residual energy intake and growth, feed intake, and carcass traits of young bulls.

Residual energy intake, defined as actual minus predicted energy intake during a production period, was estimated for each of 650 bull calves of 31 Holstein Friesian or Brown Swiss sires. Residual energy intake, measured under ad libitum feeding, had heritabilities similar to those of growth rate and energy conversion ratio with an estimate of approximately .3. Residual energy intake was related to average daily energy intake both phenotypically and genetically such that selection for decreased residual energy intake would lead to a decrease in daily feed intake. Such selection would also tend to increase carcass fatness (i.e., genetically fat animals are the most efficient). Residual energy intake estimated with and without correction for carcass composition were closely correlated. Thus, residual energy intake may be estimated without the knowledge of carcass composition in growing bulls of dual-purpose breeds.     

Complex vertebral malformation in holstein calves.

A recently observed lethal congenital defect of purebred Holstein calves is reported. Eighteen genetically related calves were necropsied. One calf had been aborted on gestation day 159, and the others were delivered between day 250 and day 285. Birth weights were reduced. The defect was characterized by shortening of the cervical and thoracic parts of the vertebral column due to multiple hemivertebrae, fused and misshaped vertebrae, and scoliosis. Symmetrical flexures of the carpal joints and the metacarpophalangeal joint in combination with a slight lateral rotation of the phalanges also were present. Similar low-grade arthrogryposis was present in the posterior limbs. Fifty percent of the calves had heart malformation. Other malformations occurred in a few calves. Complex vertebral malformation (CVM) is proposed as the designation for this defect. A genetic etiology is indicated because cases occurred following breeding between genetically related individuals. Two common ancestors were found; both were former elite sires of US Holstein origin. Because of the widespread international use of semen from sires occurring in the pedigrees of affected calves, CVM is expected to occur in several countries.     

Cross reaction between bovine enterovirus and South African Territories I5 foot-and-mouth disease virus.

A bovine enterovirus (E76T) isolated from a 2-year-old bull produced serologic cross reactions to South African Territories (SAT) I5 foot-and-mouth disease virus when inoculated into guinea pigs and cattle. Cross-reacting serum titers to SAT I5 virus of 1:320 by the plaque-reduction neutralization test and 1:20 by the radial immunodiffusion test occurred in 2 steers after they were inoculated with the E76T virus. In 1 steer, maximal cross-reacting titers appeared related to a 2nd exposure to the viruses or to a hyperimmune state. Ultracentrifugation and 2-mercaptoethanol studies indicated that the cross reactions were due to immunoglobulin M antibody. Sera from guinea pigs immunized with the E76T or the SAT I5 virus cross reacted with the heterologous virus by postinoculation day 7. Cross-reacting titers had decreased markedly by postinoculation day 35, whereas the homologous virus titer remained constant. Cross reactivity of the E76T virus was primarily with the SAT I5 virus, and to a lesser degree with SAT II3. Cross reactions did not occur with representatives of the 5 other antigenic types of foot-and-mouth disease virus.     

Assessment of defined antigens for the diagnosis of bovine tuberculosis in skin test-reactor cattle

The continued use of purified protein derivative (PPD) tuberculin is considered to be the main factor which limits the specificity of diagnostic tests for bovine tuberculosis (TB). This study evaluated a whole blood interferon-gamma (IFN-gamma) assay and compared the diagnostic potential of PPD with two tuberculosis-specific antigens, ESAT-6 and MPB70. To provide estimates of sensitivity and specificity, responses were measured in 180 skin test-reacting cattle, of which 131 were confirmed as tuberculous, and in 128 cattle from TB-free herds. For the skin test reactors, there was a positive correlation between the IFN-gamma responses to PPD from Mycobacterium bovis (PPDB) and PPD from Mycobacterium avium (PPDA), indicating cross-reactivity between these complex antigens which are the basis of the skin test. In comparisons of the ESAT-6 IFN-gamma test with a PPD IFN-gamma test (using PPDB compared with PPDA), there was a decrease in sensitivity (76.3 per cent vs 89.3 per cent), but a clear increase in specificity (99.2 per cent vs 92.2 per cent). The provision of high specificity, even with lower sensitivity, offers major benefits for testing in areas with a low incidence of TB.     

A COMPUTED TOMOGRAPHIC STUDY OF VOLUME AND X-RAY ATTENUATION OF THE LUNGS OF BEAGLES IN VARIOUS BODY POSITIONS

The influence of body position on volume and x-ray attenuation of the lungs of three Beagles was investigated with computed tomography. In left and right lateral recumbency, the dependent lung had decreased volume and increased x-ray attenuation compared with ventral recumbency. Volume and x-ray attenuation of the nondependent lung, however, were unchanged. In dorsal recumbency, there was a vertical gradient of x-ray attenuation being increased dorsally and decreased ventrally compared with ventral recumbency where regional differences in x-ray attenuation were not found. Results indicate a risk of overlooking a mass in the dependent pulmonary parenchyma of dogs in lateral and dorsal recumbency. Regional differences in x-ray attenuation of the lungs of dogs can be avoided if the radiographs are obtained with the dog in ventral recumbency.     

The effect of including genomic relationships in the estimation of genetic parameters of functional traits in pigs

The term functionality in animal breeding is used for traits that increase the efficiency of production by lowering the input cost, such as animal health and leg weakness related to longevity. The main objective of the study was to investigate the impact of genomic information, in a multivariate variance component analysis, on some of these traits. In addition, the effect of the inclusion was studied by testing the model's prediction ability based on best linear unbiased estimates for fixed and random effects. The material in this study consists of phenotypes from 76 683 animals, of which 4933 animals are genotyped. The heritabilities for front leg conformation, stayability, osteochondrosis and arched back, estimated using the traditional pedigree, were found to be between 0.12 and 0.29. When using the combined genomic and pedigree relationship matrix, the heritabilities were between 0.14 and 0.36. The results show that the combined relationship matrix can be used for the estimation of (co)variance components, and that the predictive ability of the model in this study marginally increases with the inclusion of genomic information.     

Adoption of milk cooling technology among smallholder dairy farmers in Kenya

Factors influencing adoption of milk cooling technology were studied with data for 90 smallholder dairy farmers who were randomly selected from seven dairy cooperative societies in Kiambu County, Kenya. Logistic regression identified the age of the household head, daily household milk consumption, freehold land ownership, fodder production area, number of female calves, cooperative membership and cooperative services as significant factors influencing farmers’ willingness to invest in milk cooling technology. These findings offer an entry point for increased interventions by policy makers and various dairy sector stakeholders in promoting milk cooling technology with the aim of significantly reducing post-harvest losses and increasing the sector’s competitiveness.