My understanding is that the filariasis test looks for malaria. No big surprise that you don't have malaria if you have no symptoms of malaria!!!
You need to find out HOW you were tested for strongyloides. Was it an antibody test or a stool test or some other test? Again, my understanding is that the antibody test is the only 'real' and reliable test for strongyloides.
Some will merely look at your eosinophil levels for an indication of infection. However, you will read from several sources that chronic infection is often withOUT increase in eosinophil count AND that hyperinfection/disseminated strongyloides infection withOUT eosinophils is indicative of a NEGATIVE outcome for the patient. Meaning if you've reached the point where you do NOT have an increase in eosinophils, you're fairly badly infected!