I'm sorry I have no answer for you. I would just like to wish you the best and hoping it's not serious.

If it is due to parasite induced anemia such as with hookworms, the RBC count would normally drop too.

The important question is which WBCs are dropping? T-cells? Which one?

Bone marrow biopsy can provide some clues but carries risks.

There are cases where the WBCs will accumulate at a site, making the blood counts temporarily lower.

Look for abnormal liver, spleen, thymus activity / sensitivity, or unusual swelling / tenderness in other areas of the body.

Also note that Ivermectin may cause low white blood cell count in 3% of people.

Clearly your WBC wage a war with something or at least try to control the situation so the body struggle to keep up with a high demand on it.

What I recommend? Support your WBC...

L-Glutamine (5g a day) it can support WBC proliferation + with higher dose it can help with a leaky gut which all have with parasites.

Taurine (500mg-1g a day) was shown to boost WBC even with a chemotherapy. It acts like an extra armor for your WBC and the rest of cells since it has a strong cytoprotective affect.

Eat raw garlic.

Vit D might help as well if you def that is.

Zinc can also support immune function but it can also slam the break on it via NF-KB pathway so it's a bit complex here.

Diet, exercise, avoid alcohol and smoke. None of this is a choice here.