Ltr1 on chromosome 2 controls in interaction with Ltr4 only parasite numbers in lymph nodes, whereas the more distal Ltr2 on the same chromosome influences development of skin lesions, splenomegaly (in interaction with Ltr3), hepatomegaly, parasite load in liver and level of CCL7 in serum. The gene discussed is CCL7; the disease is Hepatomegaly.