Possible new foal pneumonia treatment?

A possible new treatment for foal pneumonia that doesn’t risk causing multi-drug resistance has been discovered.  Researchers at Texas A&M University and the University of Georgia found that gallium maltolate (GaM), a semi-metal compound with antimicrobial and anti-inflammatory properties, could be a viable alternative to overprescribed antibiotics.

The research, funded by the Morris Animal Foundation, has been published in the Nature journal Scientific Reports.

Pneumonia is a leading cause of disease and death in foals and there is currently no effective vaccine licensed. The bacterium Rhodococcus equi (R. equi), a bacterium that occurs naturally in soil, is implicated in the most severe cases in horses. 

Unfortunately, current methods of screening for R. equi are imprecise and so many foals are treated with antibiotics, even though they would not have developed pneumonia. A combination of antibiotics is commonly used, such as azithromycin (a macrolide antimicrobial, which important for human use) and rifampin.

"While that treatment strategy saves lives in the short term, it's really driving this resistance problem because for every one foal that needs treatment, you treat several foals that don't need treatment," said Dr. Noah Cohen, the Patsy Link Chair in Equine Research at Texas A&M University, a primary investigator of the study, along with his colleague Steeve Giguère (deceased). "For the sake of foals, we want to offer veterinarians a better, non-traditional option."

For the study, the team screened 57 foals from four farms in central Kentucky for subclinical pneumonia, then divided the foals into three equal groups. Two groups contained foals with subclinical pneumonia, meaning ultrasound scans found lesions on their lungs but the foals had no clinical signs. All foals lived on farms with positive cases of R. equi pneumonia that year. Those groups were given either a combination of azithromycin and rifampin (MaR) or GaM for two weeks.

The third group served as a control group and was made up of healthy foals that were the same age as the subclinically affected foals in the two treatment groups. They were monitored and not given any treatment.

After two weeks, researchers analysed faecal samples from each foal. DNA tests revealed that the MaR treated group had an increase in both the number and diversity of antibiotic-resistant genes in the bacteria. Most alarming was the discovery that the bacteria were resistant to multiple drugs and antibiotics. The GaM treated and control groups showed no change in the number or diversity of resistance genes, a positive finding.

The team also experimentally infected soil plots with resistant and non-resistant strains of R. equi to see how foals might contaminate their environment with their excrement that can contain unabsorbed and metabolized antibiotics. MaR tended to reduce the number of bacteria in a plot's soil but increase the proportion that were resistant.

Dr. Cohen said one of his team's next steps is to test the effectiveness of GaM on foals that are clinically infected with R. equi.

"The widespread use of antibiotics has consequences and we really need to be prudent in prescribing them," said Dr. Janet Patterson-Kane, Morris Animal Foundation Chief Scientific Officer. "Gallium maltonate may be an excellent alternative and we hope, if proven fully effective, that it could be put into regular use."

For more details, see:

A Common Practice of Widespread Antimicrobial Use in Horse Production Promotes Multi-Drug Resistance

S. Álvarez–Narváez, L. J. Berghaus, E. R. A. Morris, J. M. Willingham-Lane, N. M. Slovis, S. Giguere & N. D. Cohen

Scientific Reports (2020) vol 10, Article number: 911
https://doi.org/10.1038/s41598-020-57479-9

Foot lameness improved by stifle anaesthesia

A positive response to blocking the stifle joint does not rule outlameness in the foot, recent research has shown.

Diagnostic analgesia is a common technique for locating the site of pain in lameness examinations. An anaesthetic agent is injected into a joint, or around nerves, with the aim of desensitising a specific area. If the lameness improves, that supports the site of pain being in that area.

However, things are not always as simple as they might seem. Anaesthetics don’t always stay where they have been injected and can diffuse out of joints. Their action may spread to affect neighbouring structures.

The sensory nerves supplying the lower hind limb pass close to the stifle joint, and may be blocked if the anaesthetic diffuses out of the joint.

Researchers at Cornell University College of Veterinary Medicine investigated whether anaesthetic injected into the stifle joint would influence lameness originating in the lower leg.

The study used nine adult horses and ponies of various breeds. Horses were excluded from the investigation if clinical examination or gait analysis found either a moderate bilateral hindlimb lameness or a severe unilateral hindlimb lameness.

The research team induced temporary hindlimb lameness by applying a clamp around one hind foot.

They injected local anaesthetic into the three compartments of the stifle joint, and then monitored the response with gait analysis every ten minutes for an hour and a half. At that point the foot was anaesthetised at the level of the fetlock joint (abaxial sesamoid block) to confirm that any remaining lameness originated in the foot.

In large joints like the stifle, it may take up to 30 minutes for anaesthesia to take effect. Sometimes if the lameness improves after that time it can be due to the stifle but may be due to anaesthetic affecting nerves passing close to the stifle joint..

The researchers found that intra-articular anaesthesia of the stifle produced reduction in degree of the induced foot lameness by up to 50% in a third of the horses within 30 minutes.

They suggest that clinicians should bear these results in mind before concluding that the stifle joint is the seat of the lameness. It may be that further tests need to be performed to rule out lower limb pain.

For more details, see:

Intra-articular anaesthesia of the equine stifle improves foot lameness

A Radtke, LA Fortier, S Regan, S Kraus, ML Delco.

Equine Vet Journal (2020) 52 p 314-319

Doi:10.1111/evj.13135

International interest in National Equine Forum

The 28th National Equine Forum, held in London earlier this month, sparked animated interaction from around the globe.

Leading names in the veterinary, charitable and equestrian sectors shared their knowledge and encouraged discussion to help the industry move forward in the best way for our horses.

This year’s programme covered a wide range of topics from disease risks, the donkey skin trade and social licence, to rights of way, behavioural change and preparations for the Tokyo Olympics.

You can watch all sessions can be viewed on NEF’s YouTube channel

https://www.youtube.com/c/nationalequineforum

Equine asthma survey

Australian horse owners are being sought to take part in a survey to investigate equine asthma.

Researchers at the University of Adelaide are investigating the frequency of equine asthma and risk factors for its presence in horses across Australia, and whether the recent bushfires have increased respiratory distress.

"We know from studies of race horses overseas that up to 57-80% of horses have a mild to moderate form of asthma and that as many as 14-20% of horses may have a severe form of asthma but we don't currently have much information about prevalence in Australia," says Dr. Surita du Preez, specialist veterinarian in equine internal medicine at the University's Equine Health and Performance Centre at its Roseworthy campus.

"If we can determine the prevalence of asthma in our horses here, and identify Australian-specific risk factors for development of equine asthma, we may be able to prevent disease development, and better manage horses that are already affected."

Asthma is one of the main causes of poor performance in horses, making them unwilling to go forward in race, sport or pleasure riding situations.

Dr. du Preez and honours student Jewel Azaria Tan are conducting a survey of horse owners with questions about their horses' health, use, and management including feeding and housing practices. Owners will also be asked if they have noticed increased respiratory distress in their horses after the bushfires.

"The mild to moderate form of asthma can affect horses of all ages and disciplines, not just racehorses," says Dr. du Preez. "It can result in intermittent coughing or nasal discharge or both.

"Horses have a poorly developed cough reflex and should not cough at all. If they cough it usually signifies a problem, unlike in people who have a very well-developed cough reflex and may cough because of a simple throat tickle.

"The severe form of asthma affects middle aged to older horses and is a life-long, progressive disease which if left unmanaged can results in severe airway remodelling and obstruction to airflow, resulting in breathing difficulties."

It is unclear if equine asthma has become more common, or if horses with the disease have been more severely affected, since the bushfires. 

Dr du Preez says: "We hope through this survey to establish some baseline information about the numbers of horses affected by bushfires and whether the owners noticed an increase in respiratory signs."

The survey, which is limited to horse owners living in Australia, is available at:  
https://is.gd/EAsurvey