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Vaccine shown to protect sheep against parasitic nematode
A. J. Nisbet, T. N. McNeillym, L. A. Willblood, A. A. Morrison,
D. J. Bartley, C. Longhi and others
Teladorsagia circumcincta is the primary cause of parasitic gastroenteritis, which is common in small ruminants in temperate conditions and is generally controlled using anthelmintics; however, multidrug resistance to the nematode is increasing. This paper describes the development of a vaccine against T circumcincta and a study to investigate its efficacy in challenged sheep.
By studying the immune responses directed at proteins specific to larvae that had infected sheep, a vaccine was developed containing eight recombinant proteins and tested in sheep in two independent trials. In both trials, sheep were given the vaccine with an adjuvant on three occasions, three weeks apart. Control groups received the adjuvant only, at the same time as the vaccinated groups. Following the final immunisation, all sheep were challenged with T circumcincta and dosed three times per week for four weeks.
Overall, vaccinated sheep had significantly lower mean faecal worm egg counts over the sampling period, with a mean reduction in egg output of 70 per cent in trial 1 and 58 per cent in trial 2. During peak worm egg shedding, vaccinated sheep shed 92 per cent fewer eggs than control animals in trial 1, and 73 per cent fewer eggs in trial 2. At postmortem examination, adult worm burdens in vaccinated animals were 75 per cent lower than in control animals in trial 1, and 56 per cent lower in trial 2. The authors suggest that the differences in the effect of the vaccine seen between trials may be because animals in trial 2 were approximately 30 days younger than those in trial 1.
They conclude that sheep immunised with the recombinant vaccine appeared to be more protected against T circumcincta than those that had received the adjuvant only. They add that the recombinant vaccine offers a potential alternative to anthelmintics in the face of multidrug resistance.
Implant device helps manage incontinence in paraplegic dogs
N. Granger, D. Chew, P. Fairhurst, J. W. Fawcett, S. P. Lacour, M. Craggs and others
SPINAL cord injury can often result in a loss of control over urine voiding. The options available to manage incontinence in dogs, such as intermittent catheterisation or manual expression, can cause urinary tract infections and are also impractical for the owner. A device known as a sacral anterior root stimulator can enable the bladder to empty on demand by stimulating the sacral spinal nerves using an electrical impulse. Such devices are already used in people who are paralysed. This study reports the implantation of a similar device for use in dogs, which was the result of a collaboration between vets and neuroscientists. The efficacy of the implant was monitored.
The device was fitted in nine dogs that had experienced a spinal injury for at least three months by the start of the study The surgical procedure took around two hours and the urine voiding of the dogs was assessed two days after surgery. The dogs were further assessed one and three weeks later at the clinic and any subsequent follow up was by telephone or a visit if required.
Two days after surgery, the stimulator enabled dogs to pass urine with increasingly powerful urine flow. The efficiency of urine voiding ranged from 30 to 99 per cent one week after the device was implanted. On reassessment three weeks after surgery, the eight dogs that remained in the study had a voiding efficiency of 92 to 99 per cent. On follow up at six months after surgery, the implant had resolved urine leakage in seven of eight dogs.
The authors conclude that the sacral spinal nerve stimulator is an alternative and effective method for managing incontinence in paraplegic dogs.
Journal of Veterinary Internal Medicine (2013) 27, 99-105
Use of blue LED lights to suppress melatonin secretion in mares
C. M. Walsh, R. L. Prendergast, J. T. Sheridan, B. A. Murphy
IT is common practice in the equine industry to selectively inhibit melatonin secretion in mares by exposing them to increased lighting levels during the darker winter months, thereby artificially advancing their breeding season. Currently, the standard industry protocol is to expose mares to 16 hours of light per day using a 100 W fluorescent light bulb. This study aimed to investigate the usefulness of blue light-emitting diodes (LEDs) for melatonin suppression in mares and to determine whether light administered to a single eye was enough to suppress melatonin.
Four mares were housed in a custom-built barn that mimicked natural external lighting conditions, with light provided by fluorescent bulbs during the day. On day one of the experiment two of the horses were fitted with racing cup blinkers containing a blue LED over one eye and light-proof material over the other eye. Two more mares were fitted with blinkers with blue LEDs on both eyes. The following day, in an experiment using a crossover design, each horse experienced light in one eye and light in both eyes, with varying light intensities. Each hour of exposure to light was followed by an hour of darkness. Blood samples were taken after the horses had been exposed to blue LED light and after being exposed to darkness, and melatonin levels were measured.
The authors found that there was no significant difference in melatonin inhibition when blue LED light was administered to just one eye compared to two eyes. They also found that a relatively low light intensity of 10 lux was sufficient to repress melatonin to the same level as standard barn lighting with a 100 W bulb.
They conclude that the findings have implications for the artificial manipulation of the equine breeding season, suggesting that it may be possible for mares to undergo light therapy outdoors by wearing a blue LED device aimed at just one eye. They suggest that such an innovation could improve the health and welfare of mares, as well as reducing management costs.
Veterinary Journal (2013) 196, 231-235
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