PCR beats serology for leptospira detection

Examining urine using a polymerase chain reaction (PCR ) technique is more reliable than serology for identifying horses infected with leptospirosis, according to scientists in Brazil.

Leptospirosis can cause various clinical signs, including abortion, uveitis, and kidney and liver disease. Sub-clinical infections also occur, in which infected horses show no signs, but carry and excrete the organism.

In a letter to the Veterinary Record, Hamond and others report the findings of a study that assessed the relative merits of serology and urine PCR for detecting Leptospira infection in horses.

Their research looked at four herds in Rio de Janeiro, Brazil. Previous cases of leptospirosis had been recorded in the herds, and none of the horses had been vaccinated against the disease.

Blood and urine samples were collected from all adult horses (144). Leptospira antibodies were found in 66 horses, and 89 horses had Leptospira DNA in the urine.

Over half of the Leptospira-positive urine samples came from horses with no Leptospira antibodies in the blood.

The authors conclude that in horses, “serology is a useful tool for detecting leptospirosis on a herd basis, but individual detection of Leptospira species carriers must rely on PCR.”

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Role of bacteria in chronic laminitis

 

Recent research suggests that bacteria may play a more significant role in chronic laminitis than previously thought.

Its not uncommon for abscesses to form underneath the dorsal hoof wall in horses with chronic laminitis. But whether these are the result of aseptic destruction of the laminae, or the result of bacteria tracking up the horn tubules is a matter of debate.

A study, by Janet Onishi and colleagues, based at Rutgers University, New Jersey, USA, investigated whether horses with chronic laminitis had evidence of sub-clinical infection in the laminar tissue.

“The objective of this study was to establish whether bacteria colonize laminar tissue and whether horses with chronic laminitis have higher or different microbes in the laminar tissue compared to non-laminitic horses” they explained.

Hoof samples were collected in a sterile manner from five horses with chronic laminitis, and from eight horses with normal feet.

The researchers found that laminae from horses with chronic laminitis contained 100 times the number of bacteria than did laminae from unaffected animals.

Only a few bacteria, all Gram-positive organisms, were isolated from the laminae of the healthy horses. In contrast, the laminae from chronic laminitic cases contained many more bacteria. Again Gram-postive organisms predominated, including bacteria in the phylum Actinobacteria, and coagulase negative Staphylococci. Many of the bacteria were identified as potential pathogens.

“The bacteria recovered from laminar tissue of chronically laminitic horses are not only potentially pathogenic, but are also known to form biofilm infections. “

(A biofilm is a complex community of micro-organisms, typically attached to a surface. Bacteria within the biofilm may be less accessible to host defences and antibacterial agents. A common example of a biofilm is dental plaque.)

The researchers suggest that horses may develop chronic laminitis as a result of biofilm infections occurring after an initial episode of acute laminitis. “We propose that treating chronically laminitic horses is difficult because there is a bacterial component to the disease that is not understood.”

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Scientists question training method

Research from the University of Sydney questions whether the round-pen (“Join-up”) training method made famous by Monty Roberts is really as humane as its supporters claim.

Lead researcher was Cath Henshall, an animal science masters degree candidate in the Faculty of Veterinary Science.

She explains: “This method of training is widely used around the world and the people that use it claim that it's a humane and kind way to train horses. They also claim that it works because the trainer is able to successfully mimic horse body language and horse behaviour.

“Our study casts doubt on both those claims. We believe that our research highlights the unpleasant underpinnings of round pen horse training and for that reason we caution against its widespread use because it uses fear to gain control of horses."

The technique relies on the trainer using movement and noise to drive the horse around the perimeter of the pen. The trainer gradually reduces their aggressive movements, after which the horse will eventually slow down and approach them.

The researchers used remote control cars to mimic the technique and to eliminate the role of the trainer in imitating the horse's body language.

They believe that the training outcomes were achieved as a result of 'pressure-release' and not the ability of the trainer, or a remote control car, to mimic horse behaviour. "Put simply,” said Henshall, “pressure-release works because the horse finds the pressure applied unpleasant and therefore the removal of the pressure rewarding.”

The response the horse makes immediately before the pressure is removed is what the horse thinks made the pressure go away. When put in the same situation in the future, it is likely to perform that same behaviour to obtain the outcome that it values – safety.

"We 'rewarded' the horses for stopping and turning towards the car with a period of 'safety', when the car didn't chase them as long as they kept facing it. We trained some horses to actually walk up to and touch the car," said Henshall.

“We found that the car is almost as successful as the human trainer, so we think that calls into question whether the horse is responding to the human as though they think the human is another horse. We also confirmed that the reason the training works is for the same reason all horse training and a lot of animal training works. So that it doesn't actually require that you understand horses' body language particularly well. It just requires that you're able to chase and not chase at the right time.”

"Given that we could train horses to produce similar, though not identical responses to those seen in round pen training, but in reaction to non-human stimuli undermines the claim that the human's ability to mimic horse behaviour is an essential component of the technique."

"Although neither Monty Roberts' method nor ours uses pressure applied directly to the horse's body, both apply a form of emotional pressure by scaring and then chasing the horse."

"Our results indicate that because these methods rely on fear and safety, the horse is forced to choose between being repeatedly frightened or remaining with the trainer. We question whether it is humane to rely on fear and its termination to train horses," said Henshall.

"Although it is appealing to think that horses in the round pen choose to follow their trainers because they are responding to us as though we are a horse, we believe that the use of fear has no place in genuinely humane and ethical horse training."

 

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Ten minutes of Low-Deep-and-Round may cause stress

Compared to other head and neck positions, horses ridden in hyperflexion, or “low deep and round” are likely to be exposed to higher levels of physiological stress, according to work presented recently at the International Equitation Science Conference in Edinburgh.

Previous studies explored the effects of the hyperflexed head and neck position on the stress and behavioural responses of horses on the lunge or a treadmill. This study, by Dutch and Danish researchers measured a variety of behavioural and physiological responses of horses ridden in hyperflexion and two other common head and neck positions.

Fifteen Danish dressage horses training at medium to Grand Prix level and routinely ridden in the hyperflexed head and neck position were used. In addition to hyperflexion, low deep and round, the standard “on the bit” or competition frame and loose frame in which there was less tension in the reins were also investigated. Each rider performed a pre-determined riding test of 10 minutes duration in walk, trot and canter in each of the three head and neck positions, randomised over the three days of testing.

Heart rate, heart rate variability, salivary cortisol concentration, behaviour and the tension in reins were recorded during the 10-minute test period. Salivary cortisol concentrations were measured 60 minutes before and 0; 5; 15 and 30 minutes after the test.

“This study is the first to test whether there is an acute stress response to the hyperflexed head and neck position in horses ridden in a typical training environment” said Dr Machteld van Dierendonck from Utrecht University. “We found that the increases in salivary cortisol concentrations from baseline were significantly higher after 10 minutes of riding in the hyperflexed position than the increases observed in the competition head position or with the loose frame.“

Cortisol is known as the ‘stress’ hormone and increased cortisol concentrations are routinely used to quantify stress responses in animal welfare studies.

“We didn’t find any significant differences in heart rate, and heart rate variability between the treatments, but we did find that certain behaviours were higher during hyperflexed riding than the other head positions. Rein tension during the hyperflexed and competition head position was significantly greater than during the loose frame position.”

“Compared to previous studies which have used side reins to maintain the hyperflexed position, the low, deep and round position in this study was less hyperflexed.” she said.

“We wanted to test the horses’ response to this method in a typical training environment. Within the parameters of this training situation, we found that the use of the hyperflexed head position, even in horses routinely ridden this way could result in a physiological stress response as measured by salivary cortisol concentrations.”

“Interestingly, riders indicated a loss of balance and steering control in the loose frame”.

Head and neck positions has been the subject of controversy with the FEI conducting two reviews in recent years.

This study was a joint work with Danish and Dutch universities. Janne Winter Christensen from Aarhus University in Denmark, along with Mirjam van Dalum, Mandy Beekmans from Utrecht University were joint researchers on this study.

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