Cryopreservation of the infective larvae of the common nematodes of ruminants

Exsheathed infective larvae (L 3) of 19 species of nematodes were tested for infectivity in either sheep or cattle after they had been frozen in 0, 9% NaCI solution, stored for a relatively short time in the gas phase of liquid nitrogen and subsequently thawed. In addition, 13 of these species were tested after similar storage for up to 18 months. In sheep, Haemonchus contortus, Ostertagia circumcincta, Trichostrongylus axei, Trichostrongylus colubriformis, Nematodirus spathiger and Oesophagostomum columbianum were viable after 2 years of cryopreservation, a mean of > 90% of the L 3 being alive when thawed after this period. Similar results were obtained with Chabertia ovina L 3 after 18 months and with Marshallagia marshalli, Trichostrongylus falculatus and Dictyocaulus filaria, after a short period of freezing. On the other hand, Gaigeria pachyscelis and Strongyloides papillosus survived freezing for up to 7 months but neither was viable at the end of this period, nor was exsheathed G. pachyscelis viable without freezing. Most of these infestations were established by inoculating the infective larvae into the abomasum and/or duodenum. M. marshalli, T. falculatus and C. ovina also proved infective after oral dosing. D. filaria, the only other species tested by this route, was not infective when dosed per os after thawing. The infective larvae of the bovine nematodes, Haemonchus placei, Ostertagia ostertagi, Nematodirus helvetianus, Oesophagostomum radiatum, Cooperia pectinata and Cooperia punctata survived freezing for a mean of 26 months, > 90% being alive on thawing, but infectivity was generally lower than with the same genera in sheep. Even when not frozen, exsheathed Bunostomum phlebotomum was non-infective. When Cooperia spp. after thawing were tested for infectivity by the oral route, more worms developed in one calf infested orally than in another infested by inoculation into the duodenum. Ova of H. contortus, M. marshalli, 0. circumcincta, T. colubnformis, T. falculatus, N. spathiger, C. ovina, H. placei, 0. ostertagi, Cooperia spp. and N. helvetianus were recovered from the faeces of animals infested with cryopreserved L 3. No ova of 0. columbianum or 0 . radiatum were recovered from faeces, because differential larval counts were performed before they were patent. Nevertheless, gravid females were obtained post-mortem. Frozen L 3 of N. helvetianus were used to re-establish a pure strain in calves, 2,3 million ova being recovered from infestations with 10 670 L 3 frozen for 26 months. The infectivity of the progeny of frozen L 3 was tested with M. marshalli and C. ovina. In both instances infectivity was high and the worms which developed also produced ova, thus completing the cycle. This appears to be the first report of infective larvae of parasitic nematodes retaining their infectivity after being frozen in liquid nitrogen (gas phase) for longer than 2 years. This is also apparently the first time that M. marshalli, T. colubriformis, T. falculatus, T. axei, N. spathiger, C. ovina, D. filaria, H. placei, 0. ostertagi, Cooperia spp., N. helvetianus and 0. radiatum have been shown to be infective after freezing in liquid nitrogen (gas phase), and that G. pachyscelis, S. papillosus and B. phlebotomum have been found to survive similar freezing and thawing, even though they do not appear to be infective thereafter.The articles have been scanned in colour with a HP Scanjet 5590; 300dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Entrepreneurial knowledge and aspirations of dentistry students in South Africa

An investigation of the intentions and knowledge of entrepreneurship of final-year university dentistry students is reported, with particular regard to the factors of gender and race. A questionnaire survey was used with final-year dentistry students, over two years, at the University of the Western Cape in South Africa. The findings show that dentistry students across race and gender groups believed that entrepreneurship education was important. At least half of the students showed an interest in starting a business practice soon after their graduation and completion of a mandatory one-year internship, with more male students indicating an interest in starting a business than female students. More Black African students indicated interest compared to other race groups (Coloureds, Whites and Indians). There were no significant differences between male and female students with regard to knowledge of entrepreneurship, but there were significant differences with regard to race in the scores for knowledge of entrepreneurship, with White students scoring the highest and African students the lowest. The authors conclude that entrepreneurship education should be included in the curriculum in the final year of dentistry studies to encourage business practice start-up soon after the one-year internship period, with the aim of contributing to growth in employment.Department of HE and Training approved lis

Spawning and non-breeding activity of adult giant bullfrogs ( Pyxicephalus adspersus

Populations of the giant bullfrog (Pyxicephalus adspersus) have been poorly monitored due to the unpredictable appearance of this species aboveground. To better understand the activity of P. adspersus we quantified spawning by a population during five summers, and the activity of twenty adult frogs radio-tracked at the same site ca. twice weekly during the first three summers. In addition we examined animal activity, and population spawning in relation to meteorological variables, day of season, and moonlight. During the six-month summer period, males and females, respectively, spent 10±7 and 3±2 days at water, and 22±5 and 13±5 nights active. Greater proportions of radio-tracked animals moved overland, and/or foraged at night, around full moon, after heavy rainfall, when cooler, and less windy conditions prevailed. More animals were found at water, or on land during the day, and population spawning was more likely, earlier in summer, following heavier rainfall. Spawning occurred most frequently, in descending order, during December, January, and November, and was triggered by 40±16 mm rain in 24h. Spawning events lasted 2±1 days, but were prolonged around full moon. Numbers of males at spawning events varied between 30 and 500 males, and were positively correlated with the previous day's rainfall. Annually 6±1 spawning events occurred, and numbers of annual spawning events were positively correlated with total summer rainfall. Results of this study show that single counts of spawning adults will often result in gross underestimates of population size, and therefore, long-term adult counts are necessary to detect real population trends. Due to the unpredictable activity of adults, however, it may be more practical to monitor, within certain areas, the number of aquatic sites where breeding occurs, for improved conservation management of P. adspersus.The study was funded through the Endangered Wildlife Trust by Rand Merchant Bank, the Pretoria East branch of the South African Hunter’s and Game Conservation Association, Arrow Bulk Marketing, Cellar Rats Wine Club, Bill Flynn and Diaz Films.http://www.tandfonline.com/loi/ther2