Parasitic infection, indeed, can lead to low WBC count and swollen lymph nodes, along with many other complains, mainly from the gastrointestinal tract (weight loss, loss of appetite, diarrhea).
Malignant process that affects the bone marrow, usually, results in low WBC count.
Swollen lymph nodes, decreased number of lymphocytes (type of white blood cells), night sweats, itchy skin, loss of weight, chest pains are symptoms of lymphoma.
However, there are many possibilities for his symptoms, so,it is important to see a physician.
At his age, it is very common to catch viral infection, known as mononucleosis, which can be manifested with swollen lymph nodes and swollen spleen (swollen spleen is responsible for the holding of white blood cells as it becomes over engorged with blood, so, the WBC count from the peripheral blood is low).

See physician!