PET scan progress

Another step forward in equine diagnostic imaging has been taken with the successful use of positron emission tomography (PET) on a standing horse. 

The use of Equine PET was pioneered at UC Davis. The first horse was imaged in 2015, and until now, the equipment available has required horses to be under general anaesthesia for the examination to be performed. 

PET shows the activity of bone or soft tissue lesions at the molecular level. A πPET scanner from Brain Biosciences, Inc. (Rockville, Maryland), was used to produce the first equine PET images. The device was originally designed to image the human brain, for research into conditions such as Alzheimer’s disease, Parkinson’s disease, Traumatic Brain Injury, Brain Cancer, and other neurological and psychiatric disorders.

A clinical program launched in August 2016 with support from the UC Davis Center for Equine Health (CEH) resulted in PET images of more than 100 horses. Reports on the research has been published*.

PET is particularly useful for detecting bone lesions that are not recognized using other imaging techniques, and for differentiating active and inactive injuries in bone or soft tissue. Movement of the subject could disrupt the image, so the early studies were carried out with the horse under general anaesthesia. Anaesthesia adds to the cost of the procedure, requires additional staff and equipment, and although rare, patients can have adverse reactions to anaesthetic drugs.

In order to develop a PET scanner specifically designed to address the unique needs of equine imaging, the PET research group at UC Davis, led by Dr. Mathieu Spriet, worked with the engineering team from Brain Biosciences, led by David Beylin and Pavel Stepanov. 

PET images are captured using detectors arranged in a ring. The current research was performed on a prototype that used the ring of detectors present in the πPET scanner but placed horizontally on the ground. The detector unit was encased in a low protective shell. This permits imaging of the foot but keeps the ring low enough for the horse to step out of the scanner safely.

Two horses from the CEH research herd were imaged using the standing equine PET prototype for the first time on January 16, 2019 under the supervision of Spriet, with assistance from UC Davis equine surgery residents Drs. Jannah Pye and Bridget Nottle, and technical support from Rich Larson.

The clinicians positioned the front feet of the sedated horse in the centre of the ring of the scanner, one at a time. 

High quality PET images, presenting 3-dimensional information, were captured within five minutes for each foot. Images were obtained on two consecutive days using the two most common PET tracers for equine imaging, the 18F-Sodium Fluoride (bone tracer) and the 18F-Fluorodeoxyglucose (soft tissue tracer). The entire procedure went smoothly, and the data collected confirmed the ability to acquire PET images of the equine forelimb in standing patients without motion artifacts compromising image quality.

Another important goal of this initial imaging session was to measure the radiation exposure to staff. Radiation measurements showed that the dose received by the staff was like that for scintigraphic bone scans, which are commonly performed in horses, thereby confirming the safety of the procedure.

 “This is a major milestone in the development of clinical equine PET imaging,” said Spriet. “The ability to perform PET on standing horses will open many new clinical applications, such as following up on injury healing and screening for lesions at risk for catastrophic breakdown in racehorses.”

In order to image the standing horse limb from the foot to the knee, the ring of detectors needs to open freely to allow the horse to remove its leg from the instrument without getting hurt. Belin and Stepanov have validated a mechanical design for such a scanner, and effort is currently underway to build it.

 

For more details, see:

 

https://www.vetmed.ucdavis.edu/news/positron-emission-tomography-performed-standing-horse-first-time

*References:

Positron emission tomography of the equine distal limb: exploratory study.

Mathieu Spriet, Pablo Espinosa, Andre Z. Kyme, Pavel Stepanov, Val Zavarzin, Stephen Schaeffer, Scott A. Katzman, Larry D. Galuppo, David Beylin,

Veterinary Radiology (2016) 57, p 630-638

https://doi.org/10.1111/vru.12430

18 F-sodium fluoride positron emission tomography of the equine distal limb: Exploratory study in three horses.

Spriet M, Espinosa P, Kyme AZ, Phillips KL, Katzman SA, Galuppo LD, Stepanov P, Beylin D.

Equine Vet J. (2018) 50, p125-132.

https://doi.org/10.1111/evj.12719

Is garlic effective against worms?

Two studies offer differing assessments of the value of garlic in worm control in horses.

Garlic is said to have many beneficial properties and is often fed to horses. Supplements claim benefits including anti-septic, anti-inflammatory and antibacterial effects, as well as acting as a fly repellent and appetite stimulant.  Garlic is also said to act against intestinal parasites.

There is a worldwide problem of drug resistance in nematode (roundworm) populations, which has led to a growing interest in alternative methods of control. 

Garlic formulations are often used in prevention and treatment of intestinal parasites. But are the effective? Recent reports have produced conflicting evidence regarding the effect of garlic against strongyle nematodes.

Mousa Tavassoli and colleagues at the Faculty of Veterinary Medicine, Urmia University, Iran conducted a study of the anti-parasitic effects of hydroalcoholic extracts of garlic (Allium sativum) and Ferula asafoetida (a plant native to the area that has been used to treat intestinal parasite infections in traditional medicine).

Third stage strongyle larvae were exposed to different concentrations of extracts of both plants and to tap water. 

The researchers found that both garlic and Ferula asafoetida extracts were effective against the larvae, demonstrating dose-dependent anthelmintic activities. Larval mortality rate increased significantly as the time of exposure to the extracts increased.

They conclude that hydroalcoholic extracts of F. asafoetida and A. sativum have potential anthelmintic and larvicidal activities in vitro. They suggest that further in vivo evaluation of the different parts and fractions is needed to make use of these plants for beneficial purposes.

On the other hand, a study in Italy assessed the effect of garlic on egg-shedding and found that garlic failed to control intestinal strongyles in naturally infected horses.

Francesco Buono and colleagues monitored the effect on egg shedding in horses naturally infected with intestinal strongyles.

The field trial was conducted in a horse trotter farm in Southern Italy. Fifteen naturally infected mares were allocated to one of three treatment groups:

• fresh garlic group - animals received 40 g of fresh crushed garlic once daily for 15 days;
• dry garlic group - animals received 40 g of commercial dry garlic flakes food supplement once daily for 15 days;   
• control group - no treatment

After two weeks of garlic administration, a faecal egg count reduction test showed the garlic failed to reduce strongyle egg shedding.

Long term administration of garlic has been associated with anaemia. However, in this study, red blood cell counts remained within normal limits throughout the treatment period.

They conclude: “In our study model, the oral administration of garlic formulations has no effect on reducing the egg shedding of intestinal strongyles, and the garlic supplementation over a short period of time is not responsible for hematological changes in horses.”

For more details, see:

The in vitro effect of Ferula asafoetida and Allium sativum extracts on Strongylus spp.

M. Tavassoli, G. Jalilzadeh-Amin, VRB Fard, R. Esfandiarpour.

Ann Parasitol. (2018) 64 p59–63.

https://www.ncbi.nlm.nih.gov/pubmed/29717575

Preliminary Observations of the Effect of Garlic on Egg Shedding in Horses Naturally Infected by Intestinal Strongyles

F.Buono, L. Pacifico, D. Piantedosi, G. Sgroi, B. Neola, C. Roncoroni, A. Genovese, D. Rufrano, V. Veneziano

Journal of Equine Veterinary Science (2019) 72, p79-83.

https://doi.org/10.1016/j.jevs.2018.10.025

Laminitis more common than previously thought

Recent research suggests that laminitis is as common as colic. The study, led by Dr Danica Pollard, a PhD student at the Royal Veterinary College, found that one in 10 horses or ponies may develop at least one laminitis episode each year.

The research was conducted at the Animal Health Trust, in collaboration with Rossdales Equine Hospital, and funded by World Horse Welfare.

Laminitis is a debilitating and extremely painful condition in horses and ponies with significant welfare implications. It often recurs in individual animals and around 15% of equine deaths in the UK are linked to laminitis.

The study followed 1,070 horses and ponies in Great Britain and monitored regular updates on their management and health over 29 months. Laminitis was reported 123 times in 97 animals.

Despite a long-standing belief that laminitis is a spring-time disease, this study identified that there is no ‘safe’ season. Laminitis remains a threat across England, Scotland and Wales regardless of the time of year. The research, published in Equine Veterinary Journal, has emphasised that laminitis needs to be considered an important year-round equine welfare concern in Great Britain.

Dr. Danica Pollard said: “Our findings indicate that laminitis is more common than we initially thought and occurs at similar rates to other high welfare health concerns, such as colic. “

Owners must remain vigilant and not reduce preventive measures when they mistakenly believe that the ‘high-risk’ period is over. 

She adds “We also need to stress that laminitis is not just a spring-time disease and it’s essential horse and pony owners remain proactive about its prevention at all times of the year.”

The study highlights the importance of recognising subtle signs of potentially life-threatening episodes. Most laminitic animals were reported by their owners to display non-specific and mild clinical signs, including difficulty in turning and a short/stilted gait (also referred to as ‘pottery’ gait) or lameness at walk - present in over 70% of laminitis episodes.

However, less than a quarter of affected animals displayed the more classically recognised signs, such as the typical ‘rocked back on the heels’ laminitic stance and divergent hoof rings (rings that are wider at the heel than at the toe).

Furthermore, a considerable proportion of horse/pony owners did not assess the presence of a bounding digital pulse, a commonly reported clinical sign of laminitis by vets. This suggests that owners may benefit from additional help with correctly locating and assessing their animal’s digital pulse, which could contribute to earlier detection of laminitis episodes in the future.

Only half of the 123 owner-reported laminitis episodes were confirmed by a veterinary diagnosis. Therefore, despite laminitis being considered a medical emergency by vets and expert researchers, many animals with laminitis are not receiving initial veterinary attention.  

Owners are encouraged to consult their vets if they suspect laminitis, or if they notice any of the subtle clinical signs associated with the disease, as by the time even subtle clinical signs arise, the damage within the foot has already begun. Early diagnosis and appropriate management is crucial in preventing long-term, often irreversible damage to structures within the laminitis-affected foot.

“The earlier an episode is recognised, the earlier action can be taken to give that animal the best chance of recovery” Pollard said. “We also encourage owners to consult their vets if they suspect laminitis and to work together with their vets and farriers as part of a ‘laminitis recovery’ team.”

Further work, supported by the Margaret Giffen Charitable Trust and World Horse Welfare, is underway to identify which management and health factors were collectively associated with the development of laminitis in this population of animals.

For more details, see:

Incidence and clinical signs of owner‐reported equine laminitis in a cohort of horses and ponies in Great Britain.

Pollard, D., Wylie, C. E., Newton, J. R. and Verheyen, K. L. (2018),

Equine Vet J. doi:10.1111/evj.13059