Single cleaning of pig pens is ineffective against roundworms
by Herman M. Vermeer, F. Borgsteede, C. Gaasenbeek and K. Blanken, Animal Sciences Group, Wageningen UR, NL
||Cleaning of outdoor pig pens after 10 weeks could break the life cycle of Ascaris suum and prevent pigs form being infected by the worm. However, the present study shows that cleaning alone is not able to reduce Ascaris suum infections, but should be part of a package of measures against Ascaris suum.
Control of roundworms in pigs
Ascaris suum is the most prevalent helminth on organic pig farms and is transmitted mainly via the faeces of infected pigs. The parasitic eggs are infectious to other pigs after an incubation period in the dung of at least 4 weeks. Subsequently it takes 6 weeks for an ingested egg to develop into a mature worm.
Regular (every three weeks) cleaning is a method to achieve an Ascaris suum free status without medication (Roepstorff and Nansen, 1994). However, this measure is time consuming and often unpractical.
Therefore, in the present project (Vermeer et al., 2008) we tested whether the Ascaris suum burden for organic finishing pigs can be reduced by cleaning the outdoor run once, at a time just before the eggs have become infectious.
Cleaning at week 10 could break the life-cycle
Experiments were done in 4 batches with 8 identical pens for 15 pigs each (n=480 pigs). Design of the pens are shown in >> Figure 1. Six pigs per pen were orally infected with Ascaris suum. The other non-infected pigs served as focal animals. During each of the 4 batches two cleaning treatments were tested. These treatments were:
- Nocleaning: No cleaning of the outdoor run during a batch (16 weeks) of finishing pigs
- Cleaning : Thoroughly cleaning with water (high pressure) of outdoor run in week 10 (day 70).
Day 70 was choosen as it takes 6 weeks for any eggs taken up by a pig to become adult, and another 4 weeks for eggs excreted by the adult worms to become infectious.
Thorough cleaning at day 70 following introduction of pigs breaks this cycle, as it will take another 4 weeks for newly excreted eggs to become infectious. At that time the animals have been sent for slaughter.
Infection occurs in spite of cleaning
Affected livers and egg counts in the manure had to show if this cleaning protocol keeps the non infected animals free of Ascaris suum.
The percentage of affected and condemned livers at slaughter varied between the four batches. For batch 1 in particular the experimental infection proved to be unsuccessful, because no liver damage and no Ascaris suum eggs were found at any occasion.
Overall, the percentage of unaffected livers was 59.9% for 'No cleaning' and 51.8% for 'Cleaning' and these differences were not statistically significant. Figure 2 shows the differences between treatments. Likewise, none of the differences was statistically significant.
Figure 2. Proportion unaffected livers per treatment and infected/not infected pigs.
When Ascaris suum eggs were counted in one of the manure samples of a pig the pig was labelled as 'positive'. On average 50% of the pigs was “positive” and when batch 1 was excluded it was 60%. Table 1 shows the percentage of positive pigs per cleaning treatment and infected or not infected. None of the differences was significantly different.
|Table 1. Percentage of animals with Ascaris suum eggs in the manure (all differences are statistically non significant).
Cleaning should be part of integrated measures
Based on the present experiments it is concluded that:
- Cleaning the outdoor dunging area of organic growing finishing pigs 10 weeks after the start at 25 kg does not prevent the pigs from being infected by Ascaris suum
- Conventional cleaning between batches does not remove all Ascaris suum eggs.
The results further suggest that it is very important to clean the pen between two batches. This means outdoor as well as indoor area and every surface, gap and slot. Before cleaning a chemical treatment can be applied to make the eggs less sticky and easier to remove.
Yet, the present study shows that cleaning alone is not able to reduce Ascaris suum infections, but should be part of a package of measures against Ascaris suum.
Roepstorff, A. and P. Nansen, 1994. Epidemiology and control of helminth infections in pigs under intensive and non-intensive production systems. Veterinary Parasitology, 54: 69-85.
Herman M. Vermeer, Fred H. M. Borgsteede, Cor P.H. Gaasenbeek and Klaas Blanken, 2008. Reduction of Ascaris transmission to pigs by cleaning the dunging area. Final report, April 2008.