"[EMAIL PROTECTED]" writes: > i am still curious if a serious study has been done on the subject (since i've seen so many different figures, and the 20-30% one at least came from an academic source) but my access to veterinary literature isn't the greatest...
Hello! As a Professor at Johns Hopkins School of Medicine, let me give you my understanding of why different studies report different percentage of horses that develop SE (ranging from ~20% to over 80%). At least a large part of this difference is the precise location of the horses being studied (both the country and the micro-climate of the farms in their survey). Quite simply, the more culicoides exposure, the higher the percentage of horses that develop SE! Factors that most influence culicoides levels include: - the pasture's closeness to wetlands or even being normally moist itself (areas where culicoides breed), - the general humidity (which culicoides love), - the presence of high, damp grass (which encourages the culicoides to travel there), and - frequent lack of a breeze. (The common breeze level is really important; a breezy hilltop can have virtually no cullicoides, while a nearby protected area can be filled with them, so it depends greatly on precisely where the farm is located.) Other factors influencing the reported percentage of SE horses include: - how long after import the data are collected (often surveys include horses only 1 or 2 years after import, but horses can develop SE more than 5 years after import -- and generally it is in a year with a particularly damp spring and a humid summer), - the length of the SE season in the country being surveyed, and - whether the horses are kept in a clean stall at dusk and dawn (as in many big barns, which are frequently surveyed). And studies financed by a donor that would like Icelandic horses to be sold abroad might be somewhat influenced which horses to survey. Probably the most useful data, for what fraction of horses develop SE if put into a SE-conducive location, are those that specifically focus on horses in such locations, like Anneliese Virro's important observations. Over the years she almost assuredly has received a representative cross-section of Iceys, and a very large fraction contract SE. So a very large percentage is prone to developing SE. Yet, since Anneliese finds that their US-born children virtually never get SE, it is not that they are genetically pre-determined to get this allergy. Please also note that a horse born and raised in a dry area of the US southwest, and then brought to central Florida as an adult, has a good chance of developing SE, too. Just like the Iceland-born Iceys, they did not get exposed to the culicoides' allergens when their immune systems were being programmed with what is "self", what they will not develop antibodies against, which includes the bugs they are regularly exposed to in the first few months of life. I hope this helps. yours, Barbara Barbara Sollner-Webb Biological Chemistry Department
