"We need about 2,000 additional samples and hopefully we'll get these before the year's end, so it's a little sluggish but we've received more than half," Caroline Bröjer, a veterinarian with the Institute, told Swedish Radio.
The Veterinary Institute has tried to map out how the parasite spreads and where it can be found by examining the samples. Since last year, it has urged hunters and others to send in the droppings for analysis.
Caroline Bröjer said the tapeworm's spread to date has been minimal.
"Right now it seems that we have a very low-grade infection, we have not found very many foxes testing positive in the country at all," she said.
The tapeworm was first found in foxes in 2011. The parasite is relatively harmless to animals and it does not usually spread to humans but if it does it could cause serious illness, as it is hard to treat and discover.