TABLE 4.

Microscopic lesion scores from pigs inoculated with either PRRSV, M. hyopneumoniae, or both

Group	Score for pneumonia induced by PRRSVa or M. hyopneumoniaeb at the following necropsy date:
	Day 3		Day 10		Day 28
	PRRSV	M. hyopneumoniae	PRRSV	M. hyopneumoniae	PRRSV	M. hyopneumoniae
A	1.2 ± 1.1 Bc	0	4.0 ± 0.9 A	1.7 ± 1.0 A	4.8 ± 0.7 A	3.9 ± 0.4 A
B	1.0 ± 0 B	0.3 ± 0.5	3.3 ± 1.5 A	0.8 ± 0.4 B	1.3 ± 0.5 B	1.6 ± 1.1 C
Cd	3.3 ± 0.5 A	0	3.3 ± 0.5 A	1.8 ± 1.0 A	4.3 ± 1.2 A	3.8 ± 0.5 A
D	0 C	0.2 ± 0.4	0 B	0.5 ± 0.6 B,C	0.1 ± 0.4 C	1.0 ± 0 C
E	0.2 ± 0.4 C	0	0 B	0.5 ± 0.6 B,C	0 C	2.5 ± 0.8 B
F	1.5 ± 0.8 B	0.3 ± 0.5	3.7 ± 0.8 A	0 C	1.4 ± 0.5 B	1.1 ± 0.6 C
G	0.2 ± 0.4 C	0	0 B	0.8 ± 0.4 B,C	0 C	0.3 ± 0.5 D

^aPRRSV scores are based on the severity of interstitial pneumonia. 0, no microscopic lesions; 1, mild multifocal pneumonia; 2, mild diffuse pneumonia; 3, moderate multifocal pneumonia; 4, moderate diffuse pneumonia; 5, severe multifocal pneumonia; 6, severe diffuse pneumonia. 

^bM. hyopneumoniae scores are based on the severity of peribronchiolar and perivascular cuffing and lymphoid nodule formation, as follows: 1, mild; 2, moderate; 3, severe; 4, very severe. 0, no microscopic lesions. 

^cWithin each column, values followed by different letters (A, B, C, or D) are significantly different from each other (P < 0.001). 

^dGroup C received PRRSV on day −10 and M. hyopneumoniae on day 0 and so is not matched with the other groups with respect to the number of days after inoculation with PRRSV.