At least when treating patients who have never been to countries with widespread strongyloides, the evidence suggests that mainstream doctors in such places are right to avoid prescribing ivermectin
, suggests that the answer is nuanced. Ivermectin probably does help one subset of covid-19 patients: those who are also infected by the worms it was designed to fight.
Wading through the papers whose methodologies appeared sound, Dr Bitterman noticed that the studies that looked best for ivermectin tended to cluster in regions with high rates of infections by strongyloides, a parasitic worm. Common in much of Africa, Asia and Latin America, strongyloides can cause, among other things, diarrhoea, fatigue and weight loss. However, they only pose a graver threat if their numbers grow out of control.
. And dexamethasone, a corticosteroid, is now a standard treatment for severe covid-19, because it prevents the immune system from going into overdrive and attacking the body’s own cells., a professor of medicine at the University of Minnesota, Dr Bitterman concluded that strongyloides may account for the conflicting results of studies about the effectiveness of ivermectin as a treatment for covid-19.
In the groups who received ivermectin during trials, the drug would keep strongyloides in check. But patients in control groups would be left at the worms’ mercy. This would make it look as if ivermectin were preventing deaths caused solely by covid-19, when in fact it was preventing those caused by the parasites or by a combination of the two infections. This mechanism would explain why most studies conducted in places where strongyloides are rare showed no benefit from taking ivermectin.