Evolving perceptions of bluetongue: A challenge for government and industry

From the first discovery of bluetongue virus activity in Canada in the Okanagan Valley of British Columbia in 1976 to the present, more than 175,000 sera from cattle in Canada have been tested for the presence of bluetongue antibody during the course of disease investigations and during regional or national surveys. Serological reactors have been detected only in cattle resident in the Okanagan Valley or in those originating in the United States.

Despite the regional nature of the distribution of antibody to bluetongue, international trade sanctions were applied on a nationwide basis. The strategy of the federal government for limiting the international, as well as the domestic, impact of bluetongue has evolved over the past 15 years as the epizootiology of bluetongue has become better understood. This new information is also ameliorating somewhat international attitudes toward nations which experience infections.

     

Modernizing the animal science curriculum: is change needed?

To identify an animal science curriculum is difficult because it is a "moving target" due to changing needs and demands of our society and, more specifically, to changes in the backgrounds and interests of students. Therefore, animal science curriculums not only should change, but must change, if they are to succeed. With new technological innovations and discoveries that either modify, supplement, or change basic concepts and approaches, it is paramount that changes in courses as well as in the curriculum conform. Because of the applied nature of animal science and because of the many unknowns yet to be discovered, the curriculum should be under continual scrutiny. However, we must not fix something when it is not broken. For all practical purposes, a curriculum reflects a philosophy of what subjects should be included to complete a plan of study. After a philosophy has been established the base curriculum will seldom change significantly. When it does, it will be the result of a change in people's philosophies rather than a reflection of industry needs or student interests. Teachers should not forget how to teach most effectively the material and must never lose sight of their goal of molding students into knowledgeable, wise, and responsible citizens in our society.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of mono- and polyclonal antibody-based antigen detection immunoassays for diagnosis of Trypanosoma evansi infection in the dromedary camel.

Two enzyme-linked immunosorbent assays (ELISA), one based on a mouse anti-Trypanosoma brucei group-specific monoclonal antibody and the other on rabbit anti-Trypanosoma evansi polyclonal antibodies, have been evaluated for their ability to detect circulating trypanosome antigens in camel sera as a means for the diagnosis of T. evansi infections. All 91 sera from a negative control camel herd from Kenya gave negative antigen-ELISA results in the monoclonal antibody-based ELISA and only 2 of them (2.2%) gave false positive results in the polyclonal antibody-based ELISA. In subsequent analyses of sera from infected camels (as determined by mouse inoculation), the monoclonal antibody-based ELISA detected antigens in 90 (83.3%) out of the 108 sera tested. This percentage was lower for the polyclonal antibody-based ELISA which was able to detect antigens in 67 (60.9%) out of the 110 sera tested. The two tests detected probably different antigens and when the results were combined, 99 out of 107 (92.5%) sera were shown to be ELISA positive. In a survey involving 316 camels from the Gao and Nara areas, in Mali, a high proportion of animals tested were antigen positive (43.5 and 42.9%, respectively for the mono- and polyclonal antibody-based ELISA) compared to only 22 (7.0%) diagnosed by the parasite detection techniques. Thus, these immunoassays were at least six times more sensitive than the haematocrit centrifugation technique. As a large proportion of cases may be antigen positive but parasite negative, these two of "surra" immunoassays should be used in routine diagnosis in addition to the parasite detection techniques in the dromedary camel.     

Visual assessment of pneumonic area in ovine lungs

Twelve veterinarians were asked to estimate the percentage of lung surface that appeared consolidated in eleven projected colour transparencies of pneumonic ovine lungs. The estimates were compared to the pneumonic area measured by image analysis. Although all observers had some experience in veterinary pathology there was considerable variation between individuals in the accuracy of their estimates. Large lesions were underestimated and small lesions overestimated by most observers.     

Temperature cycling periods affect growth and tuberization in potatoes under continuous irradiation

Plants of the potato (Solanum tuberosum L.) cultivars Denali, Norland, Haig and Kennebec were grown for 42 days under three temperature cycling periods (thermoperiods) with continuous irradiation in two repeated experiments to help determine if temperature cycling might be varied to optimize tuber development of potatoes in controlled environments. Thermoperiods of 6/6 hours, 12/12 hours and 24/24 hours were established with the same temperature change of 22/14C and same controlled vapor pressure deficit of 0.60 kPa. The thermoperiod of 24/24 hours significantly promoted tuber initiation but slowed tuber enlargement in all four cultivars, compared to the thermoperiods of 6/6 hours and 12/12 hours. Denali' produced the highest tuber and total dry weights under the 6/6 hours thermoperiod. Kennebec' produced the highest tuber dry weight under the 12/12 hours thermoperiod. Thermoperiods had no significant effect on shoot and root dry weights of any cultivars. The major effect of thermoperiods was on initiation and enlargement of tubers.     

The biochemical basis of resistance of potato to soft rot bacteria

Evidence is presented that a number of mechanisms are involved in the resistance of commercial cultivars of potato to soft rottingErwinia spp. These include phytoalexins, phenolics, cell wall modification, and possibly proteins. The role of elicitor-active oligogalacturonides, which are released from plant cell walls by pectic enzymes, is discussed.     

Virus transmission by aphids in potato crops

This paper reviews the contribution of vector activity and plant age to virus spread in potato crops. Determining which aphid species are vectors is particularly important for timing haulm destruction to minimize tuber infection by potato virus Y (PVY). Alate aphids of more than 30 species transmit PVY, and aphids such asRhopalosiphum padi, that migrate in large numbers before flights of the more efficient vector,Myzus persicae, appear to be important vectors. Differences in methodology, aphid biotypes and virus strains prevent direct comparisons between estimates of vector efficiencies obtained for aphids in different countries in north western Europe. M. persicae is also the most efficient vector of potato leafroll virus (PLRV), but some clones ofMacrosiphum euphorbiae transmit PLRV efficiently toNicotiana clevelandii and potato test plants. The removal of infected plants early in the season prevents the spread of PLRV in cool regions with limited vector activity. The proportion of aphids acquiring PLRV from infected potato plants decreases with plant age, and healthy potato plants are more resistant to infection later in the season. Severe symptoms of secondary leafroll developed on progeny plants of cv. Maris Piper derived from mother plants inoculated with PLRV in June or July of the previous year. Progeny plants derived from mother plants inoculated in August showed only mild symptoms, but the concentration of PLRV in these plants was as high as that in the plants with severe symptoms.