Anon is only Anon and would like to ask medically knowledgable Anons to researchantiparasitic resistance.
Anon is concerned that people may be taking ivermectin, when they are showing no symptoms (prophylactically). This Anon would only use ivermectin, if symptomatic.
Parasites can become antiparasitic resistant.
If I understand this correctly, overuse of one antiparasitic can lead to the parasites becoming immune to said antiparasitic. Anon had some livestock in the past and was advised by veterinarian to rotate dewormers and to try to deworm as seldom as animal health requires.
FDA
What isAntiparasitic Resistance?
https://www.fda.gov/animal-veterinary/safety-health/antiparasitic-resistance
Dewormer Resistance
"USHERING IN NEW THOUGHTS ON PARASITE CONTROL"
http://www.fairfieldequine.com/dewormer-resistance