A comparison of the efficacy of cleaning and disinfection methods in eliminating Salmonella spp. from commercial egg laying houses

Figures & data

Table 1.  Number of laying houses investigated by type of production and disinfection procedure

	Cage	Non-cage	All
“In-house” method	18	6	24
FGQ disinfectant (applied at a lower dilution than the GO rate)	7	2	9
Peroxygen-based disinfectant	6	2	8
Non-DEFRA-approved disinfectant	2	0	2
No disinfectant used	3	2	5
FGQ (at the GO rate)	19	4	23
Formalin 10%	11	2	13
Total	48	12	60

Figure 1.  Results of the C&D procedure of cage houses using three disinfection methods: an “in-house” method (n=18), formaldehyde/glutaraldehyde/quarternary ammonium (FGQ) at the GO rate (n=19) and using 10% formalin dilution (n=11).

Figure 2.  Results of the cleaning and disinfection of non-cage houses using an “in-house” disinfection method (n=6), and formaldehyde/glutaraldehyde/quarternary ammonium (FGQ) at the GO rate (n=4).

Table 2.  Salmonella-positive sample prevalence by sample type

	“In-house”		FGQ (GO rate)		Formalin 10%
	% positive	95% confidence interval	% positive	95% confidence interval	% positive	95% confidence interval
Cage houses
Cage interior	22.9	16.8 to 29.0	4.8	1.7 to 8.0	1.8	0.0 to 4.3
Drinkers	26.0	19.6 to 32.3	12.5	7.7 to 17.4	1.8	0.0 to 4.3
Feeders	26.6	20.0 to 33.3	8.1	4.2 to 12.0	3.6	0.1 to 7.1
Dropping boards	44.9	37.2 to 52.6	10.3	5.4 to 15.2	6.4	1.8 to 10.9
Egg belts	21.4	15.2 to 27.6	3.9	1.2 to 6.7	1.8	0.0 to 4.3
Floor	47.0	39.3 to 55.3	15.5	10.1 to 21.0	3.6	0.1 to 7.1
Non-cage houses
Nest boxes	1.7	0.0 to 4.9	0.0	N.C.	15	0.0 to 30.6
Drinkers	5.0	0.0 to 10.5	0.0	N.C.	30	9.9 to 50.1
Feeders	9.5	2.0 to 16.9	0.0	N.C.	0.0	N.C.
Slats	3.3	0.0 to 7.9	3.3	0 to 10.0	0.0	N.C.
Scratching	43.5	30.1 to 56.0	0.0	N.C.	0.0	N.C.
Soil (range)^a	52.5	37.2 to 67.1	2.5	0 to 6.7	45	N.C.
N.C., not calculated. ^aNote that soil prevalence is presented as mean (range).

Figure 3.  Change in the percentage of positive samples collected from the flocks before and after disinfection using each of the three methods.

Table 3.  Change in the sample prevalence between Flock 1 (prior to treatment) and Flock 2 (after treatment)

Type of house	Method	Median difference	75% interquartile range
Cage	“In-house”	−47.2	−72.6 to 3.92
	FGQ	−70.0	−98.9 to −14.1
	Formalin	−92.7	−100 to −85.4
Non-cage	“In-house”	−91.9	−98.6 to −59.8
	FGQ	−100	−100 to −100
	Formalin	−74.0	−53.7 to −33.4

Table 4.  Relationship between post C&D sampling results and follow-on flock

	Follow-on flock Salmonella status
% positive samples	Positive	Total	% Salmonella positive
Negative	6	14	42.9
>0 to 5%	8	14	57.1
>5 to 11.3%	8	9	88.9
>11.3 to 25%	11	12	91.7
>25%	10	11	90.9
Total	43	60