The role of co-infections in M. hyopneumoniae outbreaks among heavy fattening pigs: a field study

Table 3 Minimal models exploring factors affecting variation in M. hyopneumoniae infection status, ln-transformed no. of copies and VNTR types in pigs

Response variable	Explanatory variable		Parameter estimate ± SE	Statistic	p-value
M. hyopneumoniae infection status^†	Group^b	A	2.67 ± 0.55	χ²₂ = 32.8	<0.0001
M. hyopneumoniae infection status^†		B	1.98 ± 0.47
	Time^c	T₁	0.37 ± 0.33	χ²₁ = 0.25	0.62
	M. hyorhinis infection status^d	Infected	0.58 ± 0.27	χ²₁ = 4.59	0.032
	P. multocida infection status^d	Infected	−0.71 ± 0.33	χ²₁ = 4.49	0.034
	Group:Time^{b, c}	Group A: T₁	−0.42 ± 0.61	χ²₂ = 4.01	0.13
		Group B: T₁	−1.01 ± 0.50
M. hyopneumoniae no. of copies (ln-transformed)^{*, a}	Group^b	A	3.45 ± 0.54	F_{2, 425} = 19.7	<0.0001
		B	2.04 ± 0.55
	Time^c	T₁	0.03 ± 0.59	F_{1, 425} = 14.7	0.0001
	M. hyorhinis infection status^d	Infected	1.11 ± 0.33	F_{1, 425} = 11.2	0.0009
	A. pleuropneumoniae infection status^d	Infected	0.65 ± 0.40	F_{1, 425} = 2.70	0.10
	Group:Time^{b, c}	Group A: T₁	−1.84 ± 0.75	F_{2, 425} = 3.48	0.032
		Group B: T₁	−1.74 ± 0.77
M. hyopneumoniae MLVA^{†, a}	Group^b	A	−1.73 ± 0.51	χ²₂ = 1.02	0.60
		B	−1.18 ± 0.49
	Time^c	T₁	2.41 ± 0.59	χ²₁ = 9.20	0.0024
	PRRSV infection status^d	Infected	1.13 ± 0.56	χ²₁ = 4.09	0.043
	Group:Time^{b, c}	Group A: T₁	−2.54 ± 0.70	χ²₂ = 13.42	0.0012
		Group B: T₁	−2.13 ± 0.71

In all the models, pig IDs and farm IDs were included as random intercepts.
^†mixed logistic regression; ^* linear mixed model; ^a only positive animals; ^b Group C held as reference; ^c T0 held as reference; ^d not-infected held as reference.

ISSN: 1297-9716