The phrase "infective stage" refers to the specific period in a disease or illness when it is contagious and can be transferred to others. Full definition
The Centers for Disease Control states that if conditions are right, eggs can develop into infective stage larvae in as few as five days. (cat-lovers-only.com)
And while all equine harbor some worms because of the self - perpetuating cycle of fecal contamination and pasture grazing, high egg numbers in the feces based on FEC translate into large numbers of infective stages on pasture. (vetmed.tufts.edu)
Even when infections are treated with appropriate drugs, they often recur because the infective stages of the parasite are ever present in the soil. (sciencedaily.com)