The sources of comparative advantage in tourism

Tourism flows are usually explained through demand-side factors such as income growth in developed economies and changes in the preferences of visitors. While these models are adequate for short-term forecasts, little theoretical justification is provided to explain why certain countries perform better than others. This paper identifies which countries have a comparative advantage in the export of travel services (tourism). Consequently, the paper seeks to identify the sources of this comparative advantage. We include the standard explanatory variables (factors of production, including natural environment) for Ricardian comparative advantage, plus measures of infrastructure, health, safety and security, tourism prioritization, and various dummy variables. We also develop and test new variables, including a neighbourhood variable, which measures the benefits obtained from regional tourism clusters. Our results have important policy implications; it is clear that the natural environment has a large positive and significant impact on a country’s revealed comparative advantage, as do transport endowments (a measure of relative accessibility) and the neighbourhood variable. These findings correspond to the predictions of the neoclassical trade theories (namely Heckscher-Ohlin) and to some extent the new trade theories (Krugman).tourism, comparative advantage, trade in services

The population dynamics of the rock hyrax procavia capensis (Pallas, 1766) in the Mountain Zebra National Park

The chief objective of the study was to investigate the population dynamics of the hyrax in the Mountain Zebra National Park (MZNP). To realise this objective information on growth, age determination, reproduction, habitat utilization, behaviour, parasites and mortality had to be gathered. The growth of hyrax in relation to age is described by means of Stevens asymptotic regression equations. Near asymptotic measurements are attained first in hind foot length (at 30-33 months of age), head/body length (at 37-39 months of age), girth (at 41-48 months of age) and body mass (at 68-70 months of age). Allometric growth of the various body measurements was investigated and useful predictive relationships for mass are presented. Age determination of hyrax was studied in detail. Cementum annuli counts provided reliable estimates of age. One primary cementum line is formed annually. The dried eye lens mass was an accurate means of age determination up to c. 72 months of age. A summary of findings which will facilitate age determination of dead animals or skulls, and live animals, is provided. Reproduction in the hyrax was studied with emphasis on breeding season, age-specific litter sizes, prenatal mortality and lactation. Male hyrax attained puberty at 15-17 months of age or one year later. Females generally attained puberty at 15-17 months of age. One female (1,4% of total shot sample for the specific age group) attained puberty at 4-5 months of age. Middle-aged hyrax had significantly larger litter sizes than younger animals. Hyrax in the MZNP feed on at least 80 different plant species belonging to 33 plant families. Crude protein of stomach contents and faecal samples showed little seasonal fluctuation implying that hyrax in the MZNP were on a stable quality diet. Female hyrax enjoyed a significantly better quality diet than males for the four month period prior to parturition and during the first two months of lactation. The crude protein values of faecal and stomach samples had a significant correlation. Body fat of male and female hyrax showed seasonal variation related to physiologically stressful periods. Seasonal differences in activity patterns were demonstrated. The basic structure of hyrax social organization is the multi-female kinship group that is matrilocal. Territorial dominant males maintain harems and exclude all other adult males. Peripheral males occupy areas on the periphery of the activity areas of other members of the hyrax colony. Peripheral males do not form bachelor groups and are normally younger than territorial males. It is suggested that territorial males are able to monopolize between 3-17 females in a successful and energetic manner. Both natal and breeding dispersal occurred, the former being considerably more extensive than the latter. The ecto- and endoparasites of hyrax were identified and their burdens quantified over a 13 month period. Juveniles had significantly larger burdens of ectoparasites than did adults. Information on age-specific mortality was obtained from skulls collected in the field and at black eagles' nests. Losses that occurred in the study population due to caracal and black eagle predation were quantified. Evidence is supplied which indicates that juvenile mortality may fluctuate markedly. The population dynamics of the hyrax population in the MZNP was studied by the use of time specific life-tables, models on population growth rates, population simulation models and sensitivity analysis. Sensitivity coefficients were used as a predictor of population regulation. Female juvenile mortality was considered to be the main regulating factor. Changes in fecundity schedule are important compensatory mechanisms and also play an important role in the regulation of a hyrax population. Predation, particularly by caracal, is thought to dampen population fluctuations

A field outbreak in Ile-de-France sheep of a cardiotoxicosis caused by the plant Pachystigma pygmaeum (Schltr) Robyns (Rubiaceae)

A field outbreak of Pachystigma pygmaeum intoxication in sheep is described. Noteworthy clinical signs were: respiratory distress, apathy and subcutaneous oedema of mainly the head. Gross changes included cardiomegaly, centrilobular hepatic necrosis and effusion of body cavities. Microscopically myocardial fibrosis, affecting predominantly the endocardium of the apex, left free ventricular wall and interventricular septum, was most striking in the majority of animals, whilst myofibre atrophy was present in 1 sheep.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.lmchunu2014mn201

Isolation of the toxin responsible for gousiekte, a plant-induced cardiomyopathy of ruminants in southern Africa

Gousiekte was induced in sheep and goats by the oral and intravenous (i/v) administration of methanolic and ethanolic precipitates of aqueous extracts of Pavetta harborii. Further purification of the toxic principle was carried out by dialysis and ion-exchange chromatography. The toxin was eluted from the cation-exchange resin with 1 mol/l of ammonium acetate and finally purified on Sephadex G-10 and silica gel. Spots on thin-layer chromatographic plates (TLC) were visualized with ninhydrin. Gousiekte was induced with the pure toxin after i/v administration in goats. The yield of pure toxin was about 10 mg/kg of dried leaves. A compound, indistinguishable from the above on TLC, was also isolated from the gousiekte-inducing plants Pavetta schumanniana, Fadogia homblei and Pachystigma pygmaeum.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201

Interrupted Blood Feeding in Ticks: Causes and Consequences

Ticks are obligate hematophagous arthropods and act as vectors for a great variety of pathogens, including viruses, bacteria, protozoa, and helminths. Some tick-borne viruses, such as Powassan virus and tick-borne encephalitis virus, are transmissible within 15–60 min after tick attachment. However, a minimum of 3–24 h of tick attachment is necessary to effectively transmit bacterial agents such as Ehrlichia spp., Anaplasma spp., and Rickettsia spp. to a new host. Longer transmission periods were reported for Borrelia spp. and protozoans such as Babesia spp., which require a minimum duration of 24–48 h of tick attachment for maturation and migration of the pathogen. Laboratory observations indicate that the probability of transmission of tick-borne pathogens increases with the duration an infected tick is allowed to remain attached to the host. However, the transmission time may be shortened when partially fed infected ticks detach from their initial host and reattach to a new host, on which they complete their engorgement. For example, early transmission of tick-borne pathogens (e.g., Rickettsia rickettsii, Borrelia burgdorferi, and Brucella canis) and a significantly shorter transmission time were demonstrated in laboratory experiments by interrupted blood feeding. The relevance of such situations under field conditions remains poorly documented. In this review, we explore parameters of, and causes leading to, spontaneous interrupted feeding in nature, as well as the effects of this behavior on the minimum time required for transmission of tick-borne pathogens

Cardiomyopathy of ruminants induced by the litter of poultry fed on rations containing the ionophore antibiotic, maduramicin. 1. Epidemiology, clinical signs and clinical pathology

The epidemiological, clinical and clinical pathological findings in 20 cattle and 4 sheep from 15 outbreaks of poultry litter toxicity in South Africa over the past 6 years are documented. In 6 outbreaks, the litter emanated from batteries where maduramicin had been incorporated into rations of broilers. According to circumstantial evidence the litter involved in the 9 other outbreaks was also derived from broilers which had been fed on rations containing an ionophore. The litter was fed ad libitum to the affected stock or constituted 30-80% by volume of their rations. The principal sign manifested was sudden mortality of up to 70% of the herd or flock, usually within 20-40 days of commencement of feeding of poultry litter. A few cattle developed signs of congestive heart failure, and stiffness was commonly seen in sheep. In a dosing trial with poultry litter involving 1 steer and 6 sheep, the steer and a sheep died suddenly and a second sheep was destroyed in extremis. Tachycardia and/or cardiac arrythmia were recorded in 5 sheep, and the activity of aspartate transaminase (AST) and/or lactate dehydrogenase (LD) in the sera of 4 was elevated. Since the cardiac lesions in field cases were similar to those of ionophore poisoning and broiler rations containing maduramicin was a common factor in several outbreaks, toxic litter from some of these outbreaks were tested for the presence of this compound. Analysis by high performance liquid chromatography of litter from 2 specimens of outbreaks revealed that they contained 2,5ppm and 6,1ppm maduramicin. Sheep in a trial fed rations incorporating c 2,5ppm and 5ppm maduramicin, developed clinical signs and lesions consistent with those of the field cases.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201

Cardiomyopathy of ruminants induced by the litter of poultry fed on rations containing the ionophore antibiotic, maduramicin. II. Macropathology and histopathology

This report contains an account of the gross and histopathological lesions of 20 cattle and four sheep in 15 field outbreaks of poultry litter toxicity, one steer fed ad lib. and six sheep dosed with toxic poultry litter, and ten sheep fed experimental rations containing c 2,5 ppm and 5 ppm maduramicin. The principle macroscopic lesions in most cattle that died in field outbreaks were indicative of congestive heart failure. The lesions in sheep were similar, but generally milder. Cardiac dilatation was observed in both sheep and cattle. Microscopically, the cardiac lesions were more pronounced in cattle and comprised varying degrees of atrophy, hypertrophy, degeneration, necrosis of myocardial fibres, and interstitial fibrosis. Skeletal muscle lesions were usually more severe in sheep, particularly in the muscles of the hindquarters which appeared pale, oedematous and mottled. One of the sheep in the poultry litter dosing trial developed signs of congestive heart failure and the hearts of two others were dilated. Extensive hypertrophy and atrophy of myocardial fibres were evident in the steer fed ad lib. with this material. As in field cases, the myocardial lesions of the sheep were less severe than those of the steer. Mild cardiac dilatation was present in four of the seven sheep in the maduramicin feeding trial. Diffuse hypertrophy of myocardial nuclei was present in all seven cases, myocardial fibre atrophy in six, multifocal fibrosis and necrosis in six and two cases, respectively, and focal endocardial thickening in two. The skeletal muscles revealed granular degeneration and foci of necrosis and regeneration. The cardiac and skeletal lesions in the field outbreaks, poultry litter feeding trials and maduramicin feeding trials, were highly comparable. This suggests that this form of poultry litter intoxication is a chronic form of ionophore toxicity, the pathology of which is characterized by a dilated cardiomyopathy with congestive heart failure and mild (cattle) to severe (sheep) skeletal muscle lesions.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201

Effect of pavetamine on protein synthesis in rat tissue

Pavetamine, the active principle of plants causing gousiekte in ruminants, was found in this study to be an inhibitor of protein synthesis in the rat heart. Sprague-Dawley rats were injected intra-peritoneally with 8-10 mg/kg pavetamine and the levels of protein synthesis in the different organs determined utilizing L-[4-³H]phenylalanine incorporation. In contrast to the more than 23% inhibition found in heart tissue at 4, 24 and 48 h after administration of pavetamine, the effect on the kidney, liver, spleen, intestine and skeletal muscle was minimal or returned to pretreatment levels within 48 h. These results may offer an explanation for the clinical signs observed in ruminants with gousiekte, where the heart only is affected.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat v.9 was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.ARC-Onderstepoort Veterinary Institute. Directorates of Veterinary Services (Department of Agriculture, Conservation and Environment) of the North-West and Gauteng Provinces

Clinical pathological changes in gousiekte, a plant-induced cardiotoxicosis of ruminants

Twenty sheep were dosed with either Pachystigma pygmaeum or Fadogia homblei belonging to the Rubiaceae. The experimentally-induced cardiotoxicoses were monitored by various clinical pathological parameters and heart function tests. Elevated AST (aspartate transaminase) activity in the serum proved to be a more reliable indicator of cardiac damage in gousiekte than either LD (lactate dehydrogenase) or CK (creatine kinase). Persistent increases of AST activity were recorded from c. 14 days after commencement of dosing, and this activity sometimes peaked as late as 30 days after the dosing had ceased. Tachycardia and diminished heart function were registered only terminally. Lesions of gousiekte were present in all the sheep that were exposed to the plants. In a field outbreak of P. pygmaeum, where 60 out of 90 sheep died, 14 out of the 15 animals examined had increased AST levels compared with none of the 15 controls. These results indicated that increased enzyme levels can be of use to identify affected animals during latency in a natural outbreak of gousiekte.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.lmchunu2014mn201

Laparoscopic sterilization of the African lioness (Panthera leo)

OBJECTIVE : To describe laparoscopic ovariectomy and salpingectomy in the African lioness (Panthera leo). STUDY DESIGN : Descriptive clinical study. ANIMALS : Female lions (n = 16). METHODS : Lionesses were randomly divided into 2 groups: O = ovariectomy (n = 8) and S = salpingectomy (n = 8) for laparoscopic surgery. Two Veress needle placement techniques were used. RESULTS : Laparoscopic ovariectomy and salpingectomy were performed without complications. The poorly developed mesosalpinx and ovarian bursa rendered the uterine tube more accessible for salpingectomy compared to the dog making the procedure easier in the lioness. Similarly, salpingectomy is a relatively easier procedure compared with ovariectomy especially when the modified Hasson technique for Veress needle placement is used. CONCLUSIONS : Laparoscopic ovariectomy and salpingectomy can be safely performed in the African lioness.University of Pretoria, Pretoria, South Africa and the Arabella Dean fund of the South African Veterinary Foundation. This study was partly funded by the NRF grant of Prof. Schoeman.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1532-950Xhb2013mn201