Prevalence of trucks contaminated with PEDV
The prevalence of trucks contaminated upon slaughterhouse entrance was 71.8% and 20.12% of the trucks were suspicious; while the prevalence of trucks contaminated with PEDV at the exit of the slaughterhouse was 70.5% and 19.5% of the truck were suspicious. (Table 1)
Table 1. Proportion of trucks contaminated by PEDV at slaughterhouse
Real time
PCR
|
On entry to the slaughterhouse
|
On exit of the slaughterhouse
|
n (%)
|
CI 95%
|
n (%)
|
CI 95%
|
RT PCR Result
|
(-)
|
42 (8.1)
|
7.1 -9.1
|
52 (10)
|
9-11.
|
(+)
|
372 (71.8)
|
70.8 -72.8
|
365 (70.5)
|
69.5 -71.5
|
(+/-)
|
104 (20.1)
|
19.1 -21.1
|
101 (19.5)
|
18.5 -20.5
|
Total
|
518
|
|
518
|
|
(+/˗) suspicious
Characterization of practices related to transportation of pigs:
Fifty nine percent of the surveys were carried out in national slaughterhouses, followed by 30% and 10% in exportation and local slaughterhouses respectively. Additionally, 88.6% of the trucks were sampled in plants located in the area of greater sacrifice (area where the majority of slaughterhouses are located). (Figure 1).
With regards to practices used in slaughterhouses, 57% (299) of the truck were sprayed with disinfectant at the slaughterhouse entrance; in 67.8% (351 trucks) disinfection was done with back pump or spraying equipment, whereas 25.1% (130 trucks) did not undergo any disinfection process. In addition, beds (straw or wood shavings) were only gathered in 44.8% (232) of the trucks and in 59.5% (308) these were not disinfected. (Supplementary material Table)
Fig. 1 Slaughterhouse distribution according to type of slaughterhouse and area of sacrifice.
Source: Author´s design
Mobilization practices:
68.1% of the trucks visited a destination or place (only farm or slaughterhouse); 96.7% (501 trucks) do not visit the animal fair, while 48.8% (253 trucks) visited feed mills. Additionally, 37.3% of the trucks were used exclusively for pig transportation and 62.2% to transport pigs and other products. When evaluating the number of departments visited by the trucks, we found that 83.4% (432 trucks) moved within the same department, while 54.8% (284) of the trucks transport animals or products once a week.
Truck cleaning practices:
The 93.8% (486) of the cases cleaned the truck after each trip and the 49.2% (255 trucks) cleaned daily. Specifically, in 95.8% (496 trucks) they clean the truck´s body, 92.7% clean the tires (480 trucks) and 80.5% (417 trucks) clean the cabin. The cleaning elements that were most used on the trucks were: water (96.9%), soap (47.7%) and disinfectant (77.4%). The removal of organic matter was reported for 93.8% (486) of the trucks.
Transportation practices:
With regards to the use of supplies and equipment during transportation, 53.9% (279 drivers) reported not using any, 66.4% (344 drivers) did not use overalls, 53.9% (279 drivers) do not use boots, and 88% (456 drivers) do not use gloves. In addition, 81.7% (423 drivers) expressed that the step off the vehicle when they arrive at the farms or slaughterhouses.
Practices at the farms in preparation for transportation:
Washing and disinfection of trucks at the farm were done in 89% (461 trucks), where the main disinfection systems used were the back pump 80.9% (419 trucks) and the disinfection arch 10.2% (53 trucks). Whereas, to enter the farm, 79.3% (411 drivers) did not shower, and 68.9% (357 drivers) did not use any protective element. As far as supply of protective elements and equipment to the drivers, 49.4% (256 drivers) did not receive any, and 60.2% (312 drivers) and 52.3% (271 drivers) did not receive overalls and boots respectively. Additionally, 58.9% (305 trucks) are for the farm´s exclusive use.
Factors associated to the presence of PEDV and practices in transportation to slaughterhouses:
Washing practices vs. RT – PCR Results: 98% (391) of the trucks did not have any changes in the RT-PCR at the entrance or exit of the slaughterhouse, and only 1% (4) of the trucks that were positive before the washing had a negative result after this process (McNemar p value: 0.375). Therefore, there is no evidence that disinfection in the slaughterhouses is associated with a modification of the PCR result.
Table 2 shows the main factors associated to contamination with PEDV such as: the type of slaughterhouse – national or national – export slaughterhouse, the washing system, the non-exclusive use of vehicles for the transportation of pigs, visits to animal feed mills, drivers that getting off the trucks and do not use personal protective equipment. The factors identified that reduce the possibility of contamination were cleanliness of the body truck and the cabin, use of disinfectant, pressurized, and back pump and the exclusive use of the vehicle for pig transportation.
Table 2 Factors associated to contamination by PEDV
Due to technical limitations, full-text HTML conversion of Table 2 could not be completed. However, the table can be downloaded and accessed in the Supplementary Files.
Association between RT PCR results and practices related to transportation:
Two models were applied to associate PEDV with biosecurity measures in transportation. The variables used were adjusted and provided the best explanation for each model. The first model contained independent variables related to the slaughterhouses such as: type of plant, zone where the slaughterhouse was located, and vehicle use, where reference categories were; local plant, zone of lower sacrifice and transportation of only pigs respectively. The second model contained independent variables related to biosecurity practices in porcine mobilization such as they type of plant, visits to animal fairs, and visits to feed mills, where the reference categories for each one were: local plant, not visiting fairs, and not visiting animal feed mills, respectively.
P-values were obtained for the goodness of fit of the models, determined by the Hosmer-Lemeshow test, of 0.240 and 0.950, which indicates a good adjustment of the logistic model in both cases. (Tables 3 and 4).
The factors that increased the possibility of a truck being positive for PEDV when entering a slaughterhouse were: the national type (OR 15.9, CI 95%: 4.9–51.85) and the export type (OR 9.0, CI 95%: 2.20-36.91), the highest slaughter area (area where the majority of slaughterhouses are located) (OR 9.05, CI 95%: 2.96-27.63) and the use of vehicles for transportation of pigs and other products (OR 3.75, CI 95%: 1.55-9.08) instead of only pigs. Table 3.
Table 3 Model 1: PEDV RT-PCR versus slaughterhouse variables
Variable
|
Adjusted OR
|
CI 95% for the adjusted OR
|
p value
|
Slaughterhouse type
|
|
|
<0.001
|
National
|
15.95
|
4.90–51.85
|
<0.001
|
Export
|
9.02
|
2.20–36.91
|
0.002
|
Zone of sacrifice
(> slaughter zone)
|
9.05
|
2.96–27.63
|
<0.000
|
Use of vehicle ( pigs and other products)
|
3.75
|
1.55–9.08
|
0.003
|
In addition, factors related to the movement of pigs that played a role in the contamination of the truck by PEDV were: the national type slaughterhouse (OR 35.5, CI 95%: 12.7-111.1), export type slaughterhouse (OR 33.1, CI 95% : 10.0-109.63) and visits to animal feed mills (OR 13.56, IC 95%: 4.17–44.12). Table 4.
Table 4 Model 2: PEDV RT-PCR versus movement variables
Variable
|
Adjusted OR
|
CI 95% for adjusted OR
|
p value
|
Slaughterhouse type
|
|
|
<0.000
|
National
|
35.58
|
12.71–111.15
|
<0.000
|
Export
|
33.16
|
10.03–109.63
|
<0
|
Visits to fairs (Yes)
|
2.05
|
0.27–15.78
|
0.49
|
Visits to animal feed mills (Yes)
|
13.56
|
4.17–44.12
|
<0.000
|