Unless you have a parasitic infection, you do not need Ivermectin. Never take drugs unless you really need them as prescribed by your doctor. People landed in the hospital with ivermectin poisoning. Studies in humans showed this antiparasitic drug does nothing to prevent or treat viral infections like Covid-19 or to increase immunity.
https://www.nejm.org/doi/full/10.1056/NEJMc2114907

There was some pseudoscience about this drug, it has been debunked and several studies claiming it can prevent or treat viral infections were retracted for poor practices and misleading information.
https://www.phc.ox.ac.uk/news/new-study-shows-i...

If you heard that Ivermectin helps treat cancer, it is just because some parasitic infections increase the risk for certain cancers, and doctors use ivermectin against those parasitic infections, thus reducing the risk for cancer in the infected people. Parasite removed means lower risk of cancer due to that parasite.
https://www.cancer.org/cancer/risk-prevention/i...

https://pmc.ncbi.nlm.nih.gov/articles/PMC5233816/

Parasites that Can Lead to Cancer | American Cancer Society

https://www.cancer.org/cancer/risk-prevention/infections/infections-that-can-lead-to-cancer/parasites.html

New study shows ivermectin lacks meaningful benefits in COVID-19 treatment

https://www.phc.ox.ac.uk/news/new-study-shows-ivermectin-lacks-meaningful-benefits-in-covid-19-treatment

Parasite Infection, Carcinogenesis and Human Malignancy

https://pmc.ncbi.nlm.nih.gov/articles/PMC5233816/

I doubt one would have various parasites and not notice it. They aren't known for subtleties. And I doubt that anyone cooking their food properly and having a good hygiene in the developed world would be riddled with parasites.
I grew up in Eastern Europe and I had one parasite once in my childhood. We had regular testing and we weren't riddled with parasites, despite the abhorrent level of poverty there in the 1980s.

Of course water treatment would deal with parasites. That is checked frequently and we would be told to boil our water otherwise. The parasites and pathogens you would be exposed to by contaminated drinking water are the type that would make you sick. So it is unlikely you won't notice them and won't need medical attention.
Wastewater has parasites, becasue pets and other animals and even children do have parasites from time to time, uncooked meat can have parasites, flies can lay eggs, but even wastewater is treated to kill pathogens and parasites before being released.
https://microbiomejournal.biomedcentral.com/art...

I saw a lot of snake oil peddlers scaring people blue that they have a lot of parasites because they wanted to sell them some "treatment" on how to get rid of the supposed parasites. I prefer to trust authorities and science. Much safer.

For anyone who fears water has parasites, probably because they have their own well, or use a stream, or travel in tropical areas, then they can just boil their drinking water. Also, swimming in the wild might have some risks of parasitic infection, as well as eating raw meat or fish. But these things are not that common.

I know MPNs fill us with anxiety and we want to find answers and a cure. Maybe some emotional support and help coping with uncertainties are a more productive way for us regarding handling the full plate that is a chronic blood cancer than worrying about factors that most likely have no impact or role in our disease, such as parasites.

Microeukaryotic gut parasites in wastewater treatment plants: diversity, activity, and removal - Microbiome

https://microbiomejournal.biomedcentral.com/articles/10.1186/s40168-022-01225-y