Effects of doxycycline dose rate and pre-adulticide wait period on heartworm-associated pathology and adult worm mass

Table 2 Lesion scoring criteria for tissue histology in dogs experimentally infected with Dirofilaria immitis

Tissue		Score
Tissue		1	2	3	4
Heart	Pulmonary artery	Rare, small, intimal proliferation	Multifocal, regular proliferation	Multifocal, villous proliferation	Multifocal bulbous to plaque-like proliferation
Lung	Thrombus	Vessel < 25% occluded	Vessel 25–49% occluded	Vessel 50–74% occluded	Vessel > 75% occluded
	Endoarteritis	WBC infiltration limited to intima	Up to 50% vessel wall	50–99% infiltration	Transmural
	Fibrosis	Focal	Multifocal	Locally extensive	Diffuse
	Vascular proliferation	Focal	Multifocal	Locally extensive	Diffuse
Liver	Necrosis	Mild	Moderate	Marked	N/A
	Granuloma	Low numbers of leukocytes	Moderate numbers of leukocytes	Large numbers of leukocytes	N/A
	Portal/centrilobular infiltrates	Low numbers of leukocytes	Moderate numbers of leukocytes	Large numbers of leukocytes	N/A
Kidney	Interstitial nephritis (cortex)	Rare, minimal infiltrates	Multifocal, ≤ 10 cells	Multifocal, > 10 cells	Multifocal to coalescing w/ necrosis
	Interstitial nephritis (medulla)	Rare, minimal infiltrates	Multifocal, ≤ 10 cells	Multifocal, > 10 cells	Multifocal to coalescing w/ necrosis
	Interstitial fibrosis/ glomerulosclerosis	Mild, focal, one or the other	Multifocal, mild in both	Multifocal, moderate in both	Locally extensive in one or both

ISSN: 1756-3305