Climate and the epidemiology of gastrointestinal nematode infections of sheep in Europe

The free-living stages of gastrointestinal nematode parasites of sheep are strongly affected by climate. Thus, extreme heat and cold are detrimental to development and survival, while, within tolerable limits, increasing temperatures generally accelerate development but increase mortality. Moisture is needed for development and translation of larvae from faeces to pasture, and so rainfall is a limiting factor for transmission. Together, these factors underpin seasonal patterns of infection in sheep, as well as geographic variation in the epidemiology and relative importance of different species within Europe. Local knowledge and experience enable treatment to be targeted appropriately to prevent dangerous levels of infection. This traditional know-how can be supplemented by predictive epidemiological models, built on thorough understanding of the influence of climate on larval availability. However, management also has a dominant role in determining patterns of infection, and is itself influenced by climate. Current geographic variation in nematode epidemiology across Europe, and knowledge of systems from outside Europe, can provide only limited perspectives on the likely effects of climate change on disease in future. This is because disease arises from complex interaction between host and parasite factors, and the implementation of optimal control strategies to meet new challenges will be slowed by the inertia of current systems. Approaches to nematode control must therefore take account not only of parasite biology, but also the forces that shape sheep farming systems and management decisions.     

THE SEROLOGICAL RESPONSE OF CHICKENS TO OIL EMULSION VACCINES CONTAINING THE V4 STRAIN OF NEWCASTLE DISEASE VIRUS

SUMMARY Experiments were conducted with vaccines containing the V₄ strain of Newcastle disease virus (NDV). Both living aqueous vaccines and vaccines consisting of virus incorporated in an oil emulsion were used. The calculated dose of virus contained in the oil emulsion vaccine was 10^8,7 50% embryo infectious doses (EID₅₀) per bird dose. Haemagglutinin inhibition (HI) antibody levels of 8 are presumed protective. One-day-old chicks with low levels of maternal antibody were vaccinated intraocularly with 10^6,3EID₅₀ of live vaccine, and concurrently with oil emulsion vaccine. Presumed protective levels of antibody were present at two weeks post vaccination and were maintained for at least seven weeks longer. When adult birds 15 weeks old with no previous exposure to NDV were vaccinated intraocularly with 10^6,7EID₅₀ per bird, protective levels of antibody were produced within a week. Unvaccinated birds put in contact with the vaccinated birds produced similar antibody levels within 14 days. Revaccination with oil emulsion vaccine after antibody levels had fallen resulted in a rapid response with high levels of antibody. When antibody-free adult commercial birds with an unknown history of exposure to NDV were vaccinated intramuscularly with oil emulsion vaccine, high antibody levels were produced for at least 21 weeks. Concurrent intraocular inoculation with 10^7,0EID₅₀ live virus did not enhance the response. Natural infection of unvaccinated birds occurred during the experiment. This was detected by the presence of HI antibody levels of short duration. When antibody-free commercial birds were inoculated intramuscularly with oil emulsion vaccine containing 10^6,0, 10^7,0, or 10^8,0EID₅₀ per bird dose, 100% of birds inoculated with the highest dose produced presumed protective levels of antibody within two weeks, as compared with a 5-week delay when using the 10^7,0EID₅₀ per bird dose.     

A comparison of two combinations of xylazine-ketamine administered intramuscularly to alpacas and of reversal with tolazoline

ObjectiveTo evaluate the anesthetic and cardiorespiratory effects of two doses of intramuscular (IM) xylazine/ketamine in alpacas, and to determine if tolazoline would reduce the anesthetic recovery time.Study designProspective randomized crossover study.AnimalsSix castrated male alpacas.MethodsEach alpaca received a low dose (LD) (0.8 mg kg⁻¹ xylazine and 8 mg kg⁻¹ ketamine IM) and high dose (HD) (1.2 mg kg⁻¹ xylazine and 12 mg kg⁻¹ ketamine IM) with a minimum of one week between trials. Time to sedation, duration of lateral recumbency and analgesia, pulse rate, respiratory rate, hemoglobin oxygen saturation, arterial blood pressure, blood-gases, and the electrocardiogram were monitored and recorded during anesthesia. With each treatment three alpacas were randomly selected to receive tolazoline (2 mg kg⁻¹ IM) after 30 minutes of lateral recumbency.ResultsOnset of sedation, lateral recumbency and analgesia was rapid with both treatments. The HD was able to provide ≥30 minutes of anesthesia in five of six alpacas. The LD provided ≥30 minutes of anesthesia in three of six alpacas. Respiratory depression and hypoxemia occurred with the HD treatment during the first 10 minutes of lateral recumbency: two animals were severely hypoxemic and received nasal oxygen for 5 minutes. Heart rate decreased, but there were no significant changes in arterial blood pressure. Tolazoline significantly shortened the duration of recumbency with the HD.ConclusionsThe HD provided more consistent clinical effects in alpacas than the LD. Intramuscular tolazoline shortened the duration of lateral recumbency in alpacas anesthetized with the HD combination.Clinical relevanceBoth doses of the combination were effective in providing restraint in alpacas and the duration of restraint was dose dependent. Supplemental oxygen should be available if using the HD and IM administration of tolazoline will shorten the recovery time.     

A questionnaire survey of the prevalence of scrapie in sheep in Britain

An anonymous, self-administered questionnaire has been used in two independent surveys to try to determine the prevalence of scrapie in the national sheep flock. The disease was recorded in 35 counties in England and Wales. About a third (26.5 and 37.3 percent) of respondents owning 100 or more sheep indicated that they had seen sheep with scrapie in their flocks. The incidences of clinical cases recorded in affected flocks in the two surveys were 0.5 and 1.1 cases/100 ewes/year. At present there is no control over the disposal of these animals. If as has been suggested, an increase in the prevalence of scrapie was a contributory factor in the emergence of bovine spongiform encephalopathy, it would seem logical that measures should be introduced to monitor the prevalence and incidence of scrapie and to control the disposal of clinical cases.     

Risk of fatal distal limb fractures among Thoroughbreds involved in the five types of racing in the United Kingdom

The risk of fatal distal limb fractures in thoroughbreds racing in the UK was calculated and shown to vary considerably between the different types of race. Flat turf racing was associated with the lowest risk (0.4 per 1000 starts) and national hunt flat racing was associated with the highest risk (2.2 per 1000 starts). The types of fracture were classified by detailed radiographic and postmortem examinations of all the cases recorded over two years, and the distribution of the different types of fracture in the five main types of racing was examined. Overall, lateral condylar fractures of the third metacarpus were the most common, and they were also the most common in national hunt-type races (hurdle, steeplechase and national hunt flat races). In all-weather flat racing biaxial proximal sesamoid fractures were most common, and in turf flat racing fractures of the first phalanx were most common. The risk of fractures of more than one bone was greater in national hunt-type races.     

Vertebral canal and spinal cord mensuration: a comparative study of its effect on lumbosacral myelography in the dachshund and German shepherd dog

One hundred noncontrast spinal radiographic studies followed by myelography were evaluated to compare vertebral canal size and spinal cord location and size in a chondrodystrophic breed (50 Dachshunds) with those variables in a nonchondrodystrophic breed (50 German Shepherd Dogs). Measurements were made of the sagittal diameter (height) of the vertebral canal, sagittal diameter (height) of the spinal cord, and transverse diameter (width) of the spinal cord in the lumbar and sacral regions. Differences were detected in the craniocaudal location of maximal vertebral canal height and maximal spinal cord height. The spinal cords in the Dachshunds terminated further caudally than those in the German Shepherd Dogs. Location of maximal spinal cord width was different between the breeds, consistent with the apparent, more caudal termination of the cord in the Dachshunds. The ratio of spinal cord to vetebral canal heights was notably greater in the Dachshunds than in the German Shepherd Dogs. These differences in vertebral canal and spinal cord mensuration may influence the choice of radiographic technique and its interpretation. Injection sites may be selected further cranially in German Shepherd Dogs (L4-5) than in Dachshunds (L5-6).     

CANINE HIP DYSPLASIA

It is the purpose of this study to call attention to new bone production that often occurs early in the sequence of pathological changes associated with canine hip dysplasia. New bone production extending to bony remodeling, as well as femoral head subluxation, both occur in the sequence of pathologic changes associated with canine hip dysplasia. Subluxation is considered primary, while osteoarthrosis is a secondary feature, and both are used in the diagnosis of canine hip dysplasia. This report concerns the significance of the presence of a solitary bony osteophyte, or spur, that is frequently evident on the caudal aspect of the femoral neck as viewed on the conventional ventrodorsal projection. This report utilizes findings from pelvic radiographs of 605 dogs (five breeds). There was a greater frequency (54%)of this bony change in cases diagnosed radiographically as dysplastic than in cases diagnosed as normal(15%).Thus, it is suggested that this minimal radiographic change can be used as an indicator of early canine hip dysplasia, especially in the absence of subluxation of the femoral head.