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Medical term: challenge studies

From: Laura

Dear Jessica, you just can't begin to know how helpful your answers are to people like me who live out in the middle of nowhere and have nobody to help us. Whenever I need help I look in the HORSE-SENSE archives first. This time I have to write, because nobody else has asked this question yet! It's about medical terms or anyway scientific terms. My vet is a very well qualified vet, unlike most of the other vets out here he is a horse vet, not just a cow vet who treats some horses on the side. But he doesn't have much of a bedside manner, what I mean is, he's very good with the horses, and I trust him completely, but he isn't at all good at talking to people or answering questions in a way that normal (non-doctor) humans can understand.

This spring, he vaccinated my six horses for West Nile Virus. He came back two weeks later to give the second shots, then said they'd need a booster shot in a year. Last week he called and left a message that he would be out in three weeks to do fall boosters including West Nile Virus. I called him and asked if this meant we were in more danger than he had previously thought, and he left another message for me a few days later, saying "I don't guess so, just figure they're all part of a challenge study."

I don't know what this means. I've heard the term "challenge study" before, but I thought it meant that some noncommercial organization or else some other company would run a study of their own, to show that the first company's vaccine product wasn't working. It makes sense to me that another company would "challenge" the first one's claims. Is that what it means, or do I have it all wrong? I would like to know before my vet comes out, because I know I'll never get a clear explanation from him. I don't know whether he just can't explain clearly, or whether he doesn't think he should have to explain, we should just do what he says, or whether he thinks everyone else knows all the terms he knows. I know you always tell people to ask their vets, but what are we supposed to do when we ask and don't get answers we can understand? Help, please!


Hi Laura! Your guess isn't exactly right, but it's not too far wrong, and your reasoning really did sound very logical. ;-)

A "challenge study" is a study aimed at testing the effectiveness of a drug. In the case of the West Nile Virus vaccine, the way to conduct a challenge study would be to take a group of horses that had been given both initial doses of the vaccine. The horses would then be deliberately exposed to the disease - "challenged" with West Nile Virus. At that point, the researchers would collect all sorts of data, recording which (if any) horses became actively ill, HOW ill each horse became, how long each horse took to recover, and how many (if any) horses died from the disease. There are studies like these being conducted at various veterinary research facilities in the USA, and if I remember correctly, Fort Dodge Laboratories (Fort Dodge makes the WNV vaccine) was conducting some challenge studies of its own.

I'm going to guess that your veterinarian was indulging in a little bit of vet humour when he made that remark. If your horses have received both initial doses of the WNV vaccine, and a six-month booster shot, and the disease is still sweeping through your state or region, your horses may well be bitten by disease-carrying mosquitos. Since there is no way to prevent this, you COULD make a small joke by announcing that you see your horses as part of an informal, state-wide challenge study. I'll admit it's not a very big or very funny joke, but I've heard worse. ;-)


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