Prevalence of PEDV contamination in trucks
Among the 518 trucks sampled on admission, we found a PEDV contamination prevalence of 71.8% (CI 95%: 70.8% -72.8%) and found a 20.12% of suspicious trucks (CI 95%: 19.12% -21.12%); regarding among the 518 trucks sampled at the exit, we found a PEDV contamination prevalence of 70.5% (CI 95%: 69.5% -71.5%) and we found a 19.5% (CI 95%: 18.5% -20.5%) of suspicious trucks. (See table 1)
Table 1 Prevalence of PEDV contamination in tucks
At the time of PCR
|
On entry of the slaughterhouse
|
On exit of the slaughterhouse
|
n (%)
|
n (%)
|
RT-PCR result
|
(˗)
|
42 (8.1)
|
52 (10)
|
(+)
|
372 (71.8)
|
365 (70.5)
|
(+/˗)
|
104 (20.1)
|
101 (19.5)
|
Total
|
518
|
518
|
In total, 54.4% of the surveys (282 surveys) were collected at 11 slaughterhouses in Antioquia, 19.3% were collected at 4 slaughterhouses in Cundinamarca, 7.7% were collected at 3 slaughterhouses in the Valle del Cauca and 7.1% were collected at 4 slaughterhouses in the Colombian coffee region (a zone composed of the departments of Caldas, Quindío and Risaralda), which was the area containing the greatest number of slaughterhouses. Of the total surveys conducted, 59.3% (307) were carried out in national plants, 30.1% (156) in national export-type plants and 10.6% (55) in local plants. Furthermore, 88.6% (459) of the trucks were sampled at plants located in the zone containing the greatest number of slaughterhouses (Figure 1).
With respect to the practices used in slaughterhouses, it was evident that 57% (299) of the trucks were washed at the entrance, for 67.8% (351 trucks) the disinfection bow/back pump system was used, while 25.1% (130 trucks) were not subjected to any disinfection process. In addition, in 44.8% (232) of the trucks, beds were collected and in 59.5% (308) of the trucks, the beds were not disinfected.
Mobilization practices: Regarding the number of farms and slaughterhouses visited, it was evident that 68.1% trucks (353 trucks) visited another location. Among the trucks, 96.7% (501 trucks) do not visit the fair, 48.8% (253 trucks) visited a second plant animal food plants and 45.9% (238 trucks) visited only one plant. Among the trucks, 37.3% (193 trucks) were exclusively engaged in the transport of pigs, 62.2% (322 trucks) transported pigs and other products and 0.5% (3 trucks) of the drivers did not answer the question. Of the trucks that transported other products, 9.7% (50 trucks) carried other species of animals. When evaluating the number of departments visited by the trucks, it was found that 83.4% (432 trucks) were mobilized within the same department. Regarding the frequency of transportation of animals or other products, it was found that 54.8% (284 trucks) journeyed at least once a week.
Truck cleaning practices:
Truck cleaning was a practice performed in 93.8% (486) of cases, for 49.2% (255 trucks) this was performed daily. More specifically, 95.8% (496 trucks) underwent cleaning of the body, 92.7% underwent cleaning of the tires (480 trucks) and 80.5% (417 trucks) underwent cleaning of the cabin.
In terms of cleaning practices, it was found that for 96.9% (502 trucks) water was used, for 47.7% (247 trucks) soap was used and for 77.4% (401 trucks) disinfectant was used for cleaning. Regarding the type of disinfectant used, for 12% (62 trucks) oxidant agents were used. The practice of removal of organic matter was reported for 93.8% (486 trucks).
Transport practices: In relation to the use of equipment during transportation, 53.9% (279 drivers) reported not using any equipment, 66.4% (344 drivers) stated that they did not wear overalls during transport, 53.9% (279 drivers) do not use boots, 88% (456 drivers) do not use gloves and 91.5% (474 drivers) stated that they did not use any other equipment during transportation. In addition, 81.7% (423 drivers) indicated that they descend from the vehicle on arrival at farms or slaughterhouses.
Practices on the farm in preparation for transportation:
The process of washing and disinfecting trucks on the farm was carried out by 89% (461 trucks). The systems used for washing and disinfecting were predominantly a back pump 80.9% (419 trucks) and a disinfection arc 10.2% (53 trucks).
Regarding the practices implemented on entry to the farm, it was found that 79.3% (411 drivers) were not asked to shower and 68.9% (357 drivers) were not asked to use any protective elements (gaiters).
Of the drivers, 49.4% (256 drivers) stated that they were not provided endowment, 60.2% (312 drivers) reported that they were not given overalls, 52.3% (271 drivers) stated that they were not supplied with boots, 82% (425 drivers) did not receive gloves and 82.4% (427 drivers) indicated that they had not received any other protective equipment.
About the use of the truck for the transportation of farm products, 58.9% (305 trucks) indicated exclusive use of the vehicle for the farm, while 40.7% (211 trucks) were not used exclusively for the farm. In addition, 59.5% (308 drivers) reported that the farms had a parking lot and a jetty outside the farm.
Factors associated with the presence of PEDV and the transport practices to slaughterhouses:
Washing practice vs. RT-PCR result: The results showed that in 98% (391) of the trucks there were no changes in the result of RT-PCR at admission and at exit of the slaughterhouse, and only 1% (4) of the trucks that were positive before washing gave a negative result after this process (McNemar value p: 0.375). This means that there is no evidence to claim that washing at the slaughterhouse is associated with the PCR result. The factors associated with the contamination of PEDV were: the type of national slaughterhouse or national-exportation slaughterhouse, the washing system, the non-exclusive use of vehicles for the transport of pigs, visits to animal feed plants, drivers alighting the vehicle and not using personal protective equipment, as shown in Table 2.
Table 2 Factors associated with contamination of PEDV
|
|
|
OR (CI 95%)
|
p value
|
Type of Slaughterhouse
|
|
|
National
|
42.6 (16.8 -107.7)
|
0.000
|
National - Export
|
26.2 (9.4 -72.8)
|
0.000
|
Local
|
1
|
|
Washing System
|
|
|
None
|
1
|
|
Arc decontamination system / back pump
|
5.17 (2.53 - 10.56)
|
0.000
|
Other
|
0.53 (0.18 - 1.59)
|
0.262
|
Zone of slaughter
|
|
|
Zone of greater slaughter (> slaughter zone)
|
1
|
|
Zone of lesser slaughter (< slaughter zone)
|
0.04 (0.018-0.086)
|
0.000
|
|
Visit animal feed plants
|
|
|
Yes
|
14.3 (5.00-40.9)
|
*0.000
|
No
|
1
|
|
Use of the vehicle
|
|
|
Transport of pigs exclusively
|
1
|
|
Transport pigs and other products
|
2.41 (1.26-4.60)
|
0.006
|
|
Vehicle cleaning
|
|
|
Yes
|
0.089 (0.03-0.23)
|
0.000
|
No
|
1
|
|
Cabin cleaning
|
|
|
Yes
|
0.16 (0.08-0.31)
|
0.000
|
No
|
1
|
|
Use of disinfectant in cleaning
|
Yes
|
0.32 (0.16-0.62)
|
0.001
|
No
|
1
|
|
|
|
|
Alighting the vehicle
|
|
|
Yes
|
3.50 (1.05-11.6)
|
*0.039
|
No
|
1
|
|
|
Use of pressurized water in the farm
|
Yes
|
0.38 (0.15 - 0.95)
|
0.033
|
No
|
1
|
|
Use of a back pump in the farm
|
Yes
|
0.17 (0.08-0.35)
|
0.000
|
No
|
1
|
|
Use of protection equipment
|
Yes
|
1
|
|
No
|
2.63 (1.07-6.46)
|
0.028
|
Vehicle for the exclusive use of the farm
|
Yes
|
0.36 (0.19-0.70)
|
0.002
|
No
|
1
|
|
*Fisher's exact test
|
|
|
Determination of the association between transport-related practices:
Two models were applied to associate the presence of PEDV with transport biosecurity measures. The variables that fitted and provided the best explanation for each model were used. The first model contained independent variables relating to slaughterhouses such as: the type of plant, the area where the slaughterhouse was located and the use of the vehicle, where the reference categories for each were: local plant, area of least sacrifice and transportation of pigs only, respectively. The second model contained independent variables relating to biosecurity practices in pig mobilization, such as the type of plant, visits to the fair and visits to animal feed plants, where the reference categories for each were: local plant, do not visit fairs and do not visit animal feed plants, respectively.
For the goodness of fit of the models, p-values determined by the Hosmer–Lemeshow test of 0.240 and 0.950 were obtained, indicating good adjustment of the logistic model in both cases. This indicated that the models were calibrated and that the observed results were similar to the expected results (Table 3 and 4).
Regarding the positive detection of PEDV on entry of a slaughterhouse, it was observed that the national plant type (OR 15.9, CI 95%: 4.9–51.85) and national-export plant type (OR 9.0, CI 95%: 2.20–36.91), the highest slaughter area (OR 9.05, CI 95%: 2.96–27.63) and the use of vehicles for transporting pigs and other products (OR 3.75, CI 95%: 1.55–9.08) were factors that increased the possibility of a truck testing positive for PEDV. These data are shown in Table 3.
Table 3 Model 1: RT-PCR of PEDV vs. plant variables
Variable
|
Adjusted OR
|
CI 95% for the adjusted OR
|
p value
|
Plant type
|
|
|
0.000
|
National
|
15.95
|
4.90–51.85
|
0.000
|
National - export
|
9.02
|
2.20–36.91
|
0.002
|
Slaughter zone (>slaughter zone)
|
9.05
|
2.96–27.63
|
0.000
|
Vehicle use (pork and other products)
|
3.75
|
1.55–9.08
|
0.003
|
In addition, positive detection of PEDV at the entrance of slaughterhouses was found to be highly dependent on the following factors related to the movement of pigs: the type of national plant (OR 35.5, CI 95%: 12.7–111.1), national - export plants (OR 33.1, CI 95%: 10.0–109.63) and visits to animal feed plants (OR 13.56, CI 95%: 4.17–44.12). These data are shown in Table 4.
Table 4 Model 2: RT-PCR of PEDV vs. movement variables
Variable
|
Adjusted OR
|
CI 95% for adjusted OR
|
p value
|
Plant type
|
|
|
0.000
|
National
|
35.58
|
12.71–111.15
|
0.000
|
National - export
|
33.16
|
10.03–109.63
|
0
|
Fair visits (Yes)
|
2.05
|
0.27–15.78
|
0.49
|
Animal feed plants visits (Yes)
|
13.56
|
4.17–44.12
|
0.000
|