Many mysteries remain over equine grass sickness

A mare suffering from grass sickness. She made a total recovery. © Kirsty Kellaway/Equine Grass Sickness Fund

Equine grass sickness remains an enigma, 100 years afterwards the firstly cases were identified inward Scotland, a scientist says.

“This devastating affliction remains ane of the groovy unsolved mysteries inward equine medicine,” says Dr Hanspeter Meier, from the Equine Clinic at the University of Berne, Switzerland.

Still non knowing its cause, together with thus lacking whatever way for causal therapy, the affliction continues to live a threat, Meier wrote inward the latest number of Equine Disease Quarterly.

“As its cite suggests, grass sickness is strongly associated amongst grazing together with occurs inward acute, subacute, together with chronic forms amongst a considerable overlap inward clinical signs. The major symptoms relate to partial or consummate paralysis of the digestive tract.

“Considering the nature of the harm to the nervous system, combined amongst epidemiological factors, a type of toxin is suggested every bit the causative agent.

Meier says many potential causes guide maintain been examined, simply none has survived scientific scrutiny despite near xc years of investigation.

“However, the crusade was associated amongst exposure to grazing or the Earth correct from the get-go together with thus it was likewise considered that grass sickness mightiness live a cast of botulism.

“The firstly reports of botulism inward horses inward connection amongst feedstuffs were reported inward the the U.S. together with additional cases likewise were associated amongst grazing.

“Beside this, roughly symptoms of these 2 diseases are comparable.”

That grass sickness mightiness live caused yesteryear Clostridium botulinum was firstly proposed near xc years agone inward 1923, Meier said. However, these investigations failed to demonstrate clear bear witness together with the thought lost favor. Moreover, doubts persisted because of the anaerobic together with ubiquitous nature of C. botulinum.

In 1999, novel involvement inward the organism began. Researchers showed that light-green grass blades tin comprise botulinum toxin.

“On a European stud where grass sickness occurred twice inside 8 months, grass together with soil samples together with necropsy specimens were tested for the presence of bacterial forms together with toxin of C. botulinum. Different types of the germ (A-E) together with neurotoxin (BoNT) were flora together with showed that growing grass contained gratuitous BoNT.

“Bacterial forms inward soil were numerous inward May, simply were non flora inward August together with September. It is speculated that biofilms adhere to lower parts of the grass together with let C. botulinum to hold out inside a bacterial consortium piece beingness trapped together with protected from dehydration.

“Other indications for the involvement of clostridia are roughly similarities amongst the equine atypical myopathy, amongst Clostridium sordellii every bit a suspected causative agent.

“Here, nosotros likewise come across a regional, seasonal, together with pasture-associated disorder that is characterized yesteryear degenerative alterations. Also, environmental factors look to influence the incidence of both diseases every bit good as access to pasture, sure enough atmospheric condition conditions together with the marker of resistance inward older horses. The exact purpose the toxins of C. sordellii or C. botulinum play inward the respective diseases has soundless to live defined.”

Researchers inward 1924 demonstrated statistically highly pregnant protection against grass sickness yesteryear vaccinating horses amongst a mixture of botulinum toxin together with antitoxin, together with today locomote continues inward the U.K. toward demonstrating the effectiveness of a botulinum toxoid against equine grass sickness.

“Such progress volition accept to a greater extent than time, together with nosotros must brand sure enough to usage other preventive measures to the best of our knowledge. Careful husbandry together with meticulous pasture management must live of the highest standards.

“It brings to hear the maxim of the French physiologist Claude Bernard (1813-1878): ‘It is non the germ that causes affliction simply the terrain inward which the germ is found’ — an persuasion that is older than the grass sickness itself.”

 

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