SO1
Well-Known Member
I like science and understand most of the science behind worming such as refugia and resistance but I am struggling to understand how horses develop immunity to worms.
I can understand how different horses on the same worming program in the same field may have different worm counts as egg distribution is not uniform across grass and there would be an element of luck involved in if a horse happened to each more grass with worm eggs in than another horse. Also younger and older horses that are not being ridden may spend longer in the field and so they end up eating more grass so more likely to get exposed to more eggs perhaps.
The statistic 20% of the horses have 80% of the worms is often quoted - how long ago was this study. How did they know that the horses were all consuming the same amount of viable worms eggs or were the horses stabled and all fed the same amounts of viable eggs and then tested over a long period of time so they could see which horses had an immunity of not. Has the numbers of horses with immunity increased over time or decreased, are horses evolving like the worm population probably not.
I am just wondering what was different about these horses that made them more susceptible to worms and how can a horse build up an immunity to worms. Is it genetic I presume not as it appears horses immunity can change with age or their circumstances? It appears horses can also build up local immunity to parasites too as worm populations may vary in areas so it is exposure that creates the immunity a bit like with some viruses you build up antibodies after you have had the virus making you less prone to getting it again, so in order to build an immunity you need to be exposed to the pathogen at high enough levels to gain immunity so in this cases a horse that has never been exposed to a worm would have less of an immunity than a horse that has been exposed to lots of worms which might explain regional immunity if there is a difference in the genetics of worm populations.
Secondly what happens in the bodies of the horses with strong immunity to worms as they don't necessarily consume less eggs than those that are not immune do their bodies identify the eggs as harmful and expel the eggs the more quickly before they have time to develop into larva and reproduce for example.
If resistance is going to be a problem in the future what can we learn from horses that have immunity to worms in order to help protect those that don't or help them to develop immunity?
I can understand how different horses on the same worming program in the same field may have different worm counts as egg distribution is not uniform across grass and there would be an element of luck involved in if a horse happened to each more grass with worm eggs in than another horse. Also younger and older horses that are not being ridden may spend longer in the field and so they end up eating more grass so more likely to get exposed to more eggs perhaps.
The statistic 20% of the horses have 80% of the worms is often quoted - how long ago was this study. How did they know that the horses were all consuming the same amount of viable worms eggs or were the horses stabled and all fed the same amounts of viable eggs and then tested over a long period of time so they could see which horses had an immunity of not. Has the numbers of horses with immunity increased over time or decreased, are horses evolving like the worm population probably not.
I am just wondering what was different about these horses that made them more susceptible to worms and how can a horse build up an immunity to worms. Is it genetic I presume not as it appears horses immunity can change with age or their circumstances? It appears horses can also build up local immunity to parasites too as worm populations may vary in areas so it is exposure that creates the immunity a bit like with some viruses you build up antibodies after you have had the virus making you less prone to getting it again, so in order to build an immunity you need to be exposed to the pathogen at high enough levels to gain immunity so in this cases a horse that has never been exposed to a worm would have less of an immunity than a horse that has been exposed to lots of worms which might explain regional immunity if there is a difference in the genetics of worm populations.
Secondly what happens in the bodies of the horses with strong immunity to worms as they don't necessarily consume less eggs than those that are not immune do their bodies identify the eggs as harmful and expel the eggs the more quickly before they have time to develop into larva and reproduce for example.
If resistance is going to be a problem in the future what can we learn from horses that have immunity to worms in order to help protect those that don't or help them to develop immunity?
Haven't a clue, hopefully some knowledgeable worm geeks will come along and fill us in! :lol: 
