A novel galectin, a polynucleotide encoding the same, a vector and a transformant comprising the polynucleotide, an antibody against the galectin, and a screening method for screening a substance capable of modifying the galectin, are disclosed. According to the galectin, polynucleotide, or vector, it is possible, for example, to exterminate ticks, or to treat or prevent tick-borne infections such as rickettsiosis, filariasis, Q fever, African recurrent fever, or viral encephalitis.