Regarding the "Misdiagnosis" article referred to in my 9 Dec 07 entry: The comments below are observations made by Gordon DeWolf, PhD, and are published here with his consent.
********************************
Guest Post
********************************
Recently I was referred to site called Friends of the Peruvian Horse. This site purports to provide the general public with accurate information about Peruvian Horses.
I do not claim to be knowledgeable about Peruvian Horses ¬ but two sections of the site disturb me greatly. The section entitled History seems to be not as carefully researched as it should have been and the site entitled Research Articles seems to be somewhat misleading.
It would seem to me that a website purporting to promote the Peruvian Horse breed should be scrupulously accurate.
My comments on those two sections follow:
The history of the Peruvian Paso Horse, its ancestry and relationship to the Paso Fino Horse.
The horses sent to the West Indies for breeding after 1493 came, for the most part, from the districts of Spain called Andalusia and Estremadura.
Both the modern Andalusian of European and all horses of Spanish extraction in the New World are descendants of the sixteenth-century Spanish jennet, the type of horse then bred in the provinces of Estremadura and Andulacia.² Deb Bennett, Conquerors, p. 159).
The Barb did enter into the ancestry of the Jennet. However the jennet was the product of Barbs crossed onto native Spanish horses, beginning about about 800 AD. (the time of the conquest of Spain by the Moors) The jennet, which was imported to the New World, was what we would, today, call a grade horse of mixed Barb and native Spanish horse ancestry (Deb Bennett, Conquerors, p.130) In general the jennet could both pace and trot. (Deb Bennett, Conquerors, pp. 195-196)
(The Andalusian (as we know it today) dates from well after the takeover of the Spanish throne by Charles 1 of the Netherlands.)
Starting in 1493, horse breeding farms were established in all of the new Spanish colonies in the West Indies and Central and South America.
Nicaragua was settled around 1524-5. Horse breeding began with horses from the farms in the West Indies. These were the horses, raised on the breeding farms in Nicaragua, and Panama that were imported into Peru, beginning with Pizarro in 1531. They represent the same base stock which subsequently became, in Central America, the West Indies, and northern South America, what we now call Paso Fino. Most subsequent importations of horses into Peru were from these same Central American and West Indian sources.
In 1536 Argentina was settled and Spanish horses established there. In 1539, 40 horses from the Nicaraguan ranches were exported to Argentina (Deb Bennett, Conquerors, p 186). By 1830 Argentinean mules (and presumably horses) were driven across the Andes and sold in the horse market in Lima.
In about 1560 it is recorded that there were about 4,000 mares in Peru. Presumably there was then no pressing need to import more horses.
What we, today, call Paso Finos and Peruvian Pasos have developed from the same basic stock. In the West Indies the original Spanish stock was interbred with horses brought, during the colonial Period, from New England and the other British Colonies. In Colombia and the rest of Spanish America, the original Spanish stock was apparently relatively undiluted. Most differences in appearance between Paso Finos and Peruvians are due to difference in climate and hence animal survival up until the early 1800s, and to stylistic selection since that time. As a note, what the Peruvians call termino is a characteristic inherited from the jennet. In Colombia, it is regarded as a fault (Deb Bennett, Conquerors, p 218). In Spain there are (or were) a few lines of Andalusian where it was perpetuated (Sylvia Loch, The Royal Horse of Europe, P. 118).
Friends of the Peruvian Horse, Research Articles
Any meaningful scientific investigation must, to begin with, determine what single thing it is going to investigate. And any meaningful critique of a scientific investigation must critique the particular investigation and not something else.
(1) The phenomenon which has been called DSLD is a degenerative breakdown of the suspensory ligaments and tendons in two or four legs that is not the result of trauma. It is clearly shown in ultrasound scans, and does not "heal" with time (as shown by further ultrasound scans). In early stages it may appear to go into remission (sometimes for periods of months or years), but it always recurs. It is likely that most or all of the so-called cures of DSLD (cases which have been originally verified by ultrasound examination) represent these periods of quiescence which are simply normal in the development of the disease. Use of special supplements or therapeutic hoof trimming has no effect on the progression of the disease, whether or not they have a palliative effect. True cure can only be determined by a change in subsequent ultrasound exams.
DSLD appears to be the end result of physical and physiological changes in an animal, brought about by over production of proteoglycans in the whole body. Depending on the individual animal, the course of the bodily changes may be rapid (the animal showing classic DSLD at an early age) or slow (the animal showing DSLD at an advanced age ¬ 18-20 years or even later). Biopsy of the nuchal ligament is the best way of confirming the diagnosis before classic lameness symptoms appear.
(2) DSLD is to be distinguished from suspensory desmitis which usually occurs in one limb as a result of trauma or excessive stress, which does heal with time and may well not recur under normal use of the horse.
(3) A third phenomenon, related to the first is the determination that all horses with bilateral or quadrilateral DSLD (upright or dropped form) have a hypo production of proteoglycans which, among other things, interfere with normal healing or repair of suspensory tissues.
(4) Horses with bi- or quadri-lateral DSLD may not express the symptoms until the suspensories are stressed. It can, however by detected, in asymptomatic animals, by the use of an ultrasound examination.
Horses which are developing the disease but which do not show symptoms (asymptomatic) will fail a flexion test either on a pair of legs or on all four legs. Horses failing the flexion test on at least two legs should be given an ultrasound test on both legs following the protocol of Dr Mero.
(5) Bi- or quadri-lateral DSLD may first be expressed with an episode of slight, ill-defined lameness which responds to a month or more of rest. The period of normalcy which follows the rest period may continue for many months, until the ligaments are stressed again. This period of apparent normalcy may give the impression that the problem has been cured. Subsequently, lameness may appear in the other pair of legs.
(6) During the periods of normalcy, between episodes of lameness, the horse may be conditioned to perform normally. For example, my horse (for at least two years) could be conditioned to do 5-6 miles per day, 5 or 6 days per week, at about 5 mph for months on end. One day of 8-10 miles, however, would produce a bout of lameness. That amount of condition would be quite enough to allow a horse to compete successfully under show ring conditions. In other words, asymptomatic horses are perfectly capable of performing in the show ring. To put it another way, just because a horse performs well in the show ring does not mean that it does not have the beginnings of DSLD.
Sometimes this period of normalcy may be prolonged by medication which masks the pain, but does not slow the progression of the disease.
It appears that none of the "cures" instanced in either paper were confirmed by ultrasound analysis.
(7) The phenomenon called DSLD seems to be an inherited problem, and inherited in a manner that strongly suggests that it is caused by a single recessive gene.
With regard to the FRIENDS OF THE PERUVIAN HORSE RESEARCH ARTICLES the proposition is made that what has been called DSLD ¬ or what might properly described as bilateral degeneration of the suspensory ligaments - has been used by some people to give the Peruvian Paso breed a bad name.
Four points need to be made. (1) DSLD is not the only physical problem in the Peruvian Paso breed. Over the past 11 years I have had full pre-purchase exams done on 6 Peruvian Pasos, who were apparently sound at the time of the exam. Only 1 of the six proved to be truly sound. I must explain that I was seeking a horse able to compete in competitive trail trials. This requires a horse that is physically and mentally sound. The first horse quickly developed episodes of ill-defined lameness. Subsequent ultrasound exams showed deterioration of the top portions of the suspensory ligaments in both front legs. Over a period of 5 years the lameness increased until, eventually, it was not possible to keep the horse comfortable with drugs, and he had to be put down. The second horse failed the flexion test on three legs. Whatever the nature of his problem, he was not sound. The third horse had OCD in one front leg. The fourth horse had deterioration of the latissimus dorsi muscle on both side of the spine. He also had some sort of physiological problem than made it impossible for him to put on weight. The fifth horse had multiple bone spurs in two hooves. The sixth horse vetted sound and has remained sound for four years.
So, in my experience, 16 % of the horses examined had DSLD, 83% of the horses examined were unsound in one way or another, and only 16% proved to be sound. 16% of horses turning out to be sound on a thorough examination does not speak well for the soundness of the breed. Let me reiterate that all of the horses examined appeared to be sound to the naked eye, and when ridden, at the time of the exam.
(2) Sweeping serious physical bred problems under the carpet will not make the breed more attractive to potential buyers. Selling supposedly sound horses, but horses which are actually unsound, to people new to the breed tells new buyers and prospective new buyers that the people who sell (breed) Peruvian Pasos are either ignorant of their breed, ignorant about horses in general, or are not reliable people with whom to do business. Such people do the reputation of the breed far more harm than those people who acknowledge the breed problems, continue to own and use truly sound Peruvian Pasos and extol the virtues of truly sound horses.
(3) Most, if not all, technical journals expect that the papers submitted for publication will be written by be people knowledgeable in the particular field being discussed, ¬ and those papers are submitted for review to other persons knowledgeable in that particular area of the field for review of facts and conclusions. Snide comments and innuendos about other students in the field are not tolerated. It is expected that an author or a reviewer will provide full and complete data (verifiable facts and figures to substantiate his/her conclusions.
It does not appear that any of the authors of these two papers have expertise in matters veterinary ¬ nor does it appear that people knowledgeable in veterinary medicine have reviewed these papers. Further, it does not appear that the authors have differentiated DSLD from other causes of lameness.
(4) No figures are given as to the number of horses diagnosed with DSLD by verifiable ultrasound examination. No figures are given as to how many horses recover from verifiably diagnosed DSLD ¬ and this recovery verified by ultrasound examination and /or biopsy. No data is presented as to the subsequent use of the allegedly recovered horses. No data is given as to the length of time the verifiably, or allegedly, recovered horses remained sound. No figures are given as to how many horses showing DSLD as verified by ultrasound exams, had developed that condition by poor nutrition, poor farrier care, poor training, poor riding, or any of the other alleged causes of DSLD. Neither are figures given as to the ultrasound verified recovery of these horses.
Lacking ultrasound verified figures, the speculations detailed in these two papers are merely unverified conjectures which serve no useful purpose.
