Protection of sheep by vaccination against experimental challenge with Leptospira borgpetersenii serovar Hardjo and L. interrogans serovar Pomona

AIMS: To evaluate a multivalent leptospiral and clostridial vaccine for prevention of renal colonisation and urinary shedding in sheep, following experimental challenge with New Zealand strains of Leptospira borgpetersenii serovar Hardjo type Hardjobovis and L. interrogans serovar Pomona.

METHODS: Two separate but similarly designed studies were conducted. In both studies, Romney-cross lambs, aged 9–11 weeks, were randomly allocated to a vaccinated group and a control group. Vaccinated lambs each received two 1.5-mL S/C doses of a multivalent leptospiral and clostridial vaccine, 4 weeks apart, and animals in the control groups received the same dose of saline. Groups of 12 vaccinated and 12 control lambs were randomly selected in each study for challenge with serovars Hardjo or Pomona. Challenge was initiated 16 weeks following the second vaccination with three daily doses of live leptospires by intranasal and conjunctival routes. Following challenge, urine samples were collected weekly for 6 weeks, for dark field microscopy and leptospiral culture; 6 weeks after challenge the lambs were slaughtered and kidneys collected for leptospiral culture.

RESULTS: In lambs challenged with serovar Hardjo, 8/12 unvaccinated lambs had ≥1 urine or kidney sample that was positive for leptospires following culture, compared with 0/12 lambs in the vaccinated group (p=0.001). In lambs challenged with serovar Pomona, 9/12 unvaccinated lambs had ≥1 urine or kidney sample that was positive following culture, compared with 0/12 lambs in the vaccinated group (p<0.001). Prevention of renal colonisation and urinary shedding, expressed as the prevented fraction, was 100 (95% CI=61.7–100)% and 100 (95% CI=68.3–100)% against challenge with serovars Hardjo and Pomona, respectively, at 4 months after vaccination.

CONCLUSIONS AND CLINICAL RELEVANCE: Use of a multivalent leptospiral and clostridial vaccine demonstrated protection against challenge from New Zealand strains of serovars of Hardjo and Pomona 4 months after vaccination in lambs first vaccinated at 9–11 weeks of age. Further studies are required to assess the duration of immunity against challenge in sheep.     

Seasonality of sarcoptic mange in pigs in South Australia

Retrospective analysis of records, from July 1987 to June 1991, of 1140 inspections of slaughtered pigs from 154 swine herds in the Pig Health Monitoring Scheme of South Australia was conducted to evaluate patterns of variation in the prevalence and severity of skin lesions typical of sarcoptic mange. An increase in the severity of sarcoptic mange in winter and spring was observed. There was a substantial reduction in the severity of mange over the period of monitoring. These observations support the role of monitoring at slaughter in the management of endemic disease. They provide some basis for refining control programs for mange to improve cost-effectiveness.     

An ELISA for the detection of anergic tuberculous cattle

An enzyme-linked immunosorbent assay (ELISA) for bovine antibody to antigens in unheated Mycobacterium bovis culture filtrate was standardised against a reference serum from an experimentally infected cow. Two Northern Territory herds with a total of 561 cattle were tested. All cattle reacting in the caudal fold tuberculin test, those giving strong reactions in the ELISA and those with visible lesions of tuberculosis were subjected to a detailed bacteriological examination. Of the 19 cattle which yielded isolates of M. bovis, only 4 were positive to the tuberculin test. Serum samples from 5 cattle gave ELISA values greater than 7.0 units. None of these 5 reacted in the tuberculin-test and 2 had no visible lesions. Of the 10 remaining cattle from which M. bovis was isolated, 3 had ELISA values between 6.5 and 7.0 units and were also without visible lesions. The ELISA values for the remaining 7 infected cattle ranged down to 4.6 units. Forty cattle yielded no M. bovis on culture of their tissues. They included 7 which were reactors in the tuberculin test and 23 with ELISA values of 7.0 units or more. The evident low specificity and sensitivity of the ELISA make it of little value as an alternative to the tuberculin test, but it can detect some anergic cattle at the cost of increasing the number of false positive reactors. This may be acceptable in some circumstances and would justify the use of the ELISA as a complement to the tuberculin test or to an in vitro assay of T-cell immunity. In the 2 Northern Territory herds described, the removal of 5 of the anergic cattle would have required a cull of 28 animals of 5% of the total. A cut off value of 6.5 units would have eliminated 3 more, but at the cost of culling 80 animals or nearly 15% of the cattle. Even so, 7 cattle from which M. bovis was isolated would have remained undetected by either test.     

Studies on energy metabolism in lines of mice selected for different growth parameters

Growth is a very complex physiological process and is controlled by many genes and therefore easy to manipulate by selective breeding. Such manipulation of growth was realized by long-term selection of laboratory mice for different growth parameters (body weight, total protein amount in the carcass and an index combining body weight and endurance fitness) resulting in a high phenotypic and genetic differentiation compared to the nonselected control (Bünger et al. 1983, 1992, 1994; Renne et al. 1995). After 70 generations the 42-day body weights increased from 28 g at the start of selection to 58.3 g, 51.9 g and 47.4 g in these lines, respectively (Bünger et al. 1994). At the same time the carcass protein content increased from 2.92 to 5.23 g in the line selected for protein mass without an increase of fat percentage up to the age of 42 days (Renne et al. 1995). In comparison with that, selection for body weight was accompanied by a marked increase of fat percentage up to this age as reported in literature for many long-term selection experiments. Because of the different chemical composition of the body gain at relatively small differences in growth rate, these selected lines seemed to be suitable models for studying some aspects of energetic efficiency of growth. The results of a former experiment conducted in generations 32–42 suggested a higher efficiency of energy utilization in the line selected for body weight than in the other selected lines (Bünger et al. 1987). The objective of the present study was to characterize the energy metabolism of these different selected lines complementary to the studies on protein metabolism given by Schadereit et al. (1997, 1998).     

长胚芽鞘小麦品种耐深播出苗好

综述澳美欧亚非30多国百多家有关研究表明,胚芽鞘长、细、硬、快的小麦品种耐深播、立苗好。从细胞能性角度阐述胚轴划分并澄清小麦胚芽鞘的错位描述及地中茎的混淆定义。图示双胚苗的第二胚芽鞘自然开裂。图释深播地中拔节现象值得春化学者关注。概述胚芽鞘遗传长度、生理长度及环境长度。提到小麦脂肪优质育种问题。对国内麦学界提出3个具有理论或实践意义的建议。     

Age and timing of the Permian mass extinctions: U/Pb dating of closed-system zircons

The age and timing of the Permian-Triassic mass extinction have been difficult to determine because zircon populations from the type sections are typically affected by pervasive lead loss and contamination by indistinguishable older xenocrysts. Zircons from nine ash beds within the Shangsi and Meishan sections (China), pretreated by annealing followed by partial attack with hydrofluoric acid, result in suites of consistent and concordant uranium/lead (U/Pb) ages, eliminating the effects of lead loss. The U/Pb age of the main pulse of the extinction is 252.6 +/- 0.2 million years, synchronous with the Siberian flood volcanism, and it occurred within the quoted uncertainty.