Which part? About Quest being a broad spectrum and targeting the encysted and nematode forms of strongyles / cyathosims or about how once the adult forms are killed, the juvenile forms hatch and/or migrate?
I think some of that was in a link someone else had here. I’m on a diff computer, so I don’t have my links handy. I’ll try to find them.
Here’s one article that discusses the emergence of “hypobiotic” (dormant so to speak) once adults are killed off from a dewormer treatment:
http://www.thehorse.com/ViewArticle.aspx?ID=10428
EXCERPT:
As a result, most of the parasite eggs seen on an FEC exam come from one of many small strongyle species–collectively known as cyathostomins.
There are 52 known species of equine cyathostomins (small strongyles). However, only 12 species are widely prevalent and they represent the largest percentage of the parasite burden carried by most managed horses in the U.S. today. As a result, a positive fecal egg count is a probable indicator of infection with one or more of these 12 species. In the case of horses that have not been regularly treated for parasites, the positive result might also indicate infection with ascarids, large strongyles, or resistant types of cyathostomins (small strongyles).
The FEC measures only the presence of eggs from any of these–or many other–parasites in the horse’s manure. It cannot, however, specifically reveal what species of strongyle parasite is living inside the horse.
Excerpt
yielding a result called “eggs per gram,” or EPG.
For example, cyathostomin (small strongyles) in North America shed eggs in a very seasonal pattern. As a result, EPG values will increase in the spring for horses living in the northern tier state climates. These readings will then peak in the late summer and autumn, and decline in the winter. In states south of the northern tier states, this pattern is precisely the opposite, with the peak occurring in the winter months.
Another important factor that affects FEC results is something known as the “hypobiotic cycle.” Cyathostomin (small strongyle) larvae infest pastures and horses eat them when grazing. After they enter the horse, these parasites invade the tissue of the large intestine and burrow in–becoming “encysted” cyathostomin. Once they are encysted, small strongyles can become dormant, sitting in the intestinal tissue for months or even years. This arrested or inhibited development is called “hypobiosis.”
A horse with a substantial number of cyathostomin in hypobiosis might still have a negative or low EPG because these inhibited parasites are not shedding eggs. Additionally, when a horse is given an effective dose of a dewormer, it will kill off the adult strongyles. The absence of the adults created in the intestines, however, will send a signal to the inhibited cyathostomin to break out of their cysts, become adults, and start producing eggs. As a result, effective parasite treatment might occasionally increase a horse’s EPG.
I hope I didn’t quote anything out of context. I’ve read similar info from other sources. I just don’t have them handy right now.
shrug