Aspirin and prednisolone modification of radiographic changes caused by adulticide treatment in dogs with heartworm infection.

The effects of aspirin and prednisolone in modifying the radiographic changes following adulticide treatment were studied in 3 groups of 6 dogs each. The dogs were radiographed and then 9 Dirofilaria immitis adults were surgically transplanted in each dog. All dogs were treated with thiacetarsamide 4 weeks later. One group received no additional treatment, the 2nd group received aspirin (10 mg/kg, daily for 4 weeks), and the 3rd group received prednisolone (1 mg/kg, daily for 4 weeks). Radiographs were taken at 1, 2, and 3 weeks after adulticide treatment, and the dogs were euthanatized at 4 weeks. The most consistent radiographic sign of pulmonary disease was a perivascular alveolar pattern in the caudal and accessory lung lobes. The right caudal lobe was the one most frequently affected. These parenchymal lesions were more frequent and more severe in the dogs given only adulticide treatment than in those given aspirin after adulticide treatment; the latter group in turn was more severely affected than the dogs given prednisolone after adulticide treatment. The radiographic evidence of pulmonary disease was resolving in most dogs at 3 weeks. The alveolar pattern on radiographs was distributed similarly to that observed at necropsy, using parenchymal uptake of Evan's blue as an indication of increased vascular permeability. Dissection of the perfusion-fixed lungs revealed that heartworms in 3 of the 6 dogs given prednisolone appeared to survive adulticide treatment.