Saturday, July 28, 2018

Effect of insulin on the laminae

Most cases of laminitis are associated with metabolic disturbances – often involving elevated blood levels of insulin. How the hyperinsulinaemia results in laminitis is not fully understood.

One possible mechanism has been identified in a recent study that showed that insulin weakens the structural integrity of equine lamellae.

The laboratory study used explants (small portions of hoof wall, lamellar tissue and distal phalanx) maintained in tissue culture medium.

Half of the explants were kept in plain culture medium; the other half were grown in medium supplemented with insulin (2.5 μg/ml).

After eight hours the explants were subjected to biomechanical testing.

The authors report: “Lamellar explants that had been incubated in medium supplemented with insulin failed at significantly lower load (P = 0.0001) and lower stress (P = 0.001) and had greater elongation to failure (P = 0.02).”

They conclude that insulin weakens the structural integrity of equine lamellar explants.

They suggest that this laboratory model will be useful for further studies hyperinsulinaemia‐induced lamellar failure.

For more details, see:

Ex vivo effects of insulin on the structural integrity of equine digital lamellae

Sandow, C., Fugler, L.A., Leise, B., Riggs, L., Monroe, W.T., Totaro, N., Belknap, J., Eades, S.

EVJ (2018)

Does oral sulphadiazine-trimethoprim reach the uterus?

Bacterial infections of the endometrium (the superficial layer of cells lining the uterus) are an important cause of conception failure. 

Treatment often involves local administration of antibacterial agents directly into the uterus.

Potentiated sulphonamide drug combinations, such as sulfadiazine and trimethoprim, are commonly used in equine practice. They have a broad spectrum of activity and are well distributed throughout the body tissues.

Could oral administration of a suspension of sulfadiazine and trimethoprim (SDT) have a place in the treatment of bacterial endometritis?

Studies at the School of Veterinary Medicine, Louisiana State University, Baton Rouge, looked at the concentration of SDT in both the blood and endometrium of healthy, in season, mares after the administration of an oral suspension of sulfadiazine and trimethoprim.  

Mares were treated five times at twelve hourly intervals. Blood was collected to monitor the concentration of SDT during the study and an endometrial biopsy was taken after sixty hours to measure the SDT concentration in the endometrium.

The Minimum Inhibitory Concentration (MIC) is the lowest concentration of an antibiotic that inhibits the growth of a given strain of bacteria.

The research, led by Gabriel Davolli, found that, after five consecutive treatments, the sulfadiazine and trimethoprim reached concentrations in the endometrium above the MIC – and so likely to be effective -for pathogens (such as Streptococcus equi zooepidemicus and Escherichia coli) that are commonly involved in uterine infections.

The work is reported in the Journal of Equine Veterinary Science.

The authors conclude: “the oral suspension of sulfazdiazine-trimethoprim should be an efficacious and viable treatment for bacterial endometritis.”

For more details, see:

Concentrations of Sulfadiazine and Trimethoprim in Blood and Endometrium of Mares After Administration of an Oral Suspension
Gabriel M.Davolli, Kelli N.Beavers, Victor Medina, Jennifer L.Sones, Carlos R.F.Pinto,  Dale L.Paccamonti, Robert C.Causey
Journal of Equine Veterinary Science (2018) 67:27-30

New approach to worm control

A worm-eating fungus brings new hope in the fight against parasitic gastro-intestinal worms.

Anthelmintic resistance is now a widespread and growing problem. It is becoming increasingly clear that we cannot rely on chemicals alone to control gastro-intestinal parasites. 

Consequently, alternative worm control strategies are being investigated. One method showing promise is the use of a fungus that attacks the free-living larval stages of parasitic worms and so reduces the number of infective larvae on the pasture. 

Duddingtonia flagrans is a nematophagous fungus (from the Greek for “worm eating”). The fungus grows rapidly in fresh faeces and its chlamydospores (resistant spores) can survive the passage through the gastro-intestinal tract of the horse. These fungal spores have no effect on the animal and only germinate once passed in the faeces where they develop into nematode-trapping fungal nets.

Recent work in Australia showed that feeding BioWorma®, a supplement containing the Duddingtonia spores, produced substantial reductions in infective larvae on pasture surrounding faeces of treated horses, cattle and goats.

The placebo-controlled trials were conducted in different seasons and bioclimatic regions of Australia (New South Wales, Queensland). 

Faeces were collected from worm-infected animals after they had been treated with either the D flagrans supplement or a placebo. The manure was placed on pasture plots and the researchers monitored the numbers of parasitic larvae on the pasture around the faecal pats over an eight-week period.

They report that a minimum daily dose of 3 × 104 D flagrans spores/kg bodyweight reduced parasite larvae in the pasture surrounding the faeces by 53–99 % over the eight-week period after treatment in horses, cattle and goats.

Other work has shown that, unlike some chemical wormers, the fungus does not harm dung beetles or other organisms found in the faeces.

BioWorma® is about to be approved for sale in Australia and New Zealand. It should be available in the United States shortly and in Europe within the next year or two.

For more details, see the following open access article:

Field evaluation of Duddingtonia flagrans IAH 1297 for the reduction of worm burden in grazing animals: Pasture larval studies in horses, cattle and goats
Kevin Healey, Chris Lawlor, Malcolm R.Knox, Michael Chambers, Jane Lamb, Peter Groves
Veterinary Parasitology. Vol 258, pp 124-132

Origins of equine dentistry

Humans were removing horses’ teeth to relieve their pain over 3,000 years ago, according to scientists.

A team of scholars, led by William Taylor of the Max Planck Institute for the Science of Human History, examined horse remains from an ancient pastoral culture which roamed the steppes of Mongolia and eastern Eurasia between 1300 to 700 BC.

Horses congregate near a deer stone site in Bayankhongor, in central Mongolia's Khangai mountains. (c) William Taylor
Horses congregate near a deer stone site in Bayankhongor, in central Mongolia's Khangai mountains. (c) William Taylor
The Deer Stone-Khirigsuur Culture is named after the standing stones (‘deer stones’ - often decorated with images of deer) and burial mounds (khirigsuurs) it built across the Mongolian Steppe. These sites were used for ritual burial of hundreds – maybe thousands – of domestic horses.

Through careful study of skeletal remains from these burials, Taylor and colleagues found that Deer Stone-Khirigsuur people began using veterinary dental procedures to remove baby teeth that would have caused young horses pain or difficulty with feeding. In particular, they found evidence of attempts to remove temporary central incisor teeth that had not erupted correctly.

These findings provide the earliest directly dated evidence for veterinary dentistry. They suggest that innovations in equine care by nomadic peoples c 1150 BC allowed horses to be used for increasingly sophisticated mounted riding and warfare.

Drawing on insights from his Mongolian colleagues, Jamsranjav Bayarsaikhan and Tumurbaatar Tuvshinjargal of the National Museum of Mongolia, Taylor argues that the development of horseback riding and a horse-based pastoral economy was a key driver for the invention of equine veterinary care. 

The incorporation of bronze and metal mouthpieces for riding spread into eastern Eurasia during the early first millennium BC. It gave riders more control over horses and enabled them to be used for new purposes – especially warfare.

But using metal to control horses brought with it new problems – such as painful interactions with the “wolf tooth” - the vestigial first premolar tooth present in some animals. Dr Taylor and his colleagues found that as herders began to use metal bits they also developed a method for extracting the problematic “wolf tooth”. The first evidence they identified for wolf tooth removal dated to about 750BC.

"We may think of veterinary care as kind of a Western science," Taylor says, "but herders in Mongolia today practice relatively sophisticated procedures using very simple equipment. The results of our study show that a careful understanding of horse anatomy and a tradition of care was first developed, not in the sedentary civilizations of China or the Mediterranean, but centuries earlier, among the nomadic people whose livelihood depended on the well-being of their horses."

Co-author Dr Nicole Boivin, director of the Department of Archaeology at the Max Planck Institute, commented: “In many ways, the movements of horses and horse-mounted peoples during the first millennium BC reshaped the cultural and biological landscapes of Eurasia. Dr Taylor’s study shows veterinary dentistry – developed by Inner Asian herders – may have been a key factor that helped to stimulate the spread of people, ideas, and organisms between East and West.”

For more details, see: 

WTT Taylor and others.
PNAS July 17, 2018. 115 (29) E6707-E6715