https://pubmed.ncbi.nlm.nih.gov/3840994/ Seems to show that it does, but I guess the logistics of keeping a herd of cattle covered by giving shots every two weeks may be difficult. And there still is damage to the animal
The article you referred to (and I've seen linked elsewhere in this thread) is about "regular" screwworm (Chrysomya bezziana). The recent outbreak is of New World Screwworm (Cochliomyia hominivorax). The article I've linked suggests that it is much harder to kill than regular screwworm (29% of calves developed myiasis even when treated with ivermectin).
Googling "Cochliomyia hominivorax and ivermectin" yields
"Ivermectin can be an effective treatment for myiasis, a condition caused by the larvae of certain dipterous flies, including Cochliomyia hominivorax (the New World screwworm). Studies have shown that ivermectin, when administered orally or topically, can help eliminate the larvae and reduce the severity of the infestation, especially in cases of orbital or oral myiasis.
"
The study I linked to showing the effectiveness of Ivermectin was only done subcutaneously. I did not find a study on the effectiveness of non-subcutaneous Ivermectin treatments on screw worms.
Given one of the areas they focused on the study is the scrotal area post castration, I don't expect that a pour on would cover that area well enough to be an effective treatment. Happy to read other studies if you have them showing otherwise.
There are injectable and transdermal (pour-on and ear tag) forms for cattle and pigs. I'm not aware of an oral formulation for food animals, even though that's pretty common for horses.
is quite funny, where they found that the lambs were licking the topically applied ivermectin, but also that they didnt notice any decrease in parisites for any of the ingestion/injection/topical
they also say theres nothing showing any applicability to cattle
