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Management strategies for recurrent Ascaris suum in an outdoor pig unit…

- - - - Katakam et al. (2016) found statistically significant lower levels of infective eggs on deep litter compared to shallow litter in September which is important as the highest degree of development of infective eggs was found in this month.
    - - The survey by Sanchez-Vazquez et al. (2010) identified a weak but significant reduction in the risk of milk spot with use of fully slatted floors compared to other litter systems however it did not distinguish between deep and shallow litter.
      - The study by Katakam et al. (2016) found that the farm that had the strictest cleaning regime had the lowest overall parasite occurrence and slatted floors are the easiest system to maintain a high level of hygiene. #
      - Roepstorff and Jorsal (1990) found no statistically significant correlation with bedding materials and incidences of A. suum however the percentage of incidences were lower on slatted floors compared to solid.
    - - It is important to also consider the higher ammonia and nitrogen dioxide experienced in deep litter systems compared to grated floors due to its negative impact on animal and public health (Jankowska-Makosa and Knecht, 2015).
      - The study by Knecht et al. (2012) demonstrated prevalence of infection in growing pigs in a closed cycle kept on shallow litter (25%) or grated floors (15%) was statistically significantly higher than those kept on deep litter (5%), this could be due to the thermophilic composting effect of deep litter as eggs in the faeces are compacted into the litter resulting in inactivation of the eggs due to lack of oxygen, the unsuitable pH and the effects of rotting and fermentation in the litter.
      - The study by Knecht et al. (2012) also found that the group of growing pigs kept on deep litter had a higher % of meat in the carcass compared to those on shallow litter and grated floors suggesting that the higher prevalence of A. suum in the latter groups affected the meat quality resulting in economic losses. #
      - Katakam et al. (2014) stated that deep litter systems created unfavourable conditions for the development of eggs to infective stages, however, transmission was still unavoidable due to eggs becoming infective in the upper cleaner layer of the pen.
  - - - Although the majority of Ascaris eggs die very quickly outdoors, the eggs that survive are highly resistant to adverse environmental conditions and disinfectants. Once the environment has become contaminated the eggs can survive in soil for up to 9 years making it difficult to eradicate (Oh et al., 2016; Katakam et al., 2016). #
      - Due to the longevity of A. suum eggs on pasture of up to 9 years, most rotation cycles would be far too short due to availability of land (Katakam et al., 2016; Roepstorff et al., 2011).
      - If A. suum burden in soil becomes extreme, as there is no environmentally acceptable way of eradication and the eggs can survive for many years, the ground should be permanently abandoned for pigs (RUMA, 2010). #
      - Avoiding use of "pig sick" pastures and moving pigs to clean ground is recommended although this can be difficult where there is limited land for the farmer (RUMA, 2010).
      - Outdoor farms should operate on a nomadic basis if possible, moving onto fresh pasture every one to two years and never returning to the same field within 9 years (RUMA, 2010; Neville, 2014; Katakam et al., 2016).
      - Ploughing of fields appeared to reduce parasite transmission however A. suum pasture infectivity was still too high to be suitable for pigs nine years after contamination demonstrating that ploughing was ineffective (Mejer and Roepstorff, 2011).
- - - - If burden is managed then the cost of treatment is trivial compared to the potential cost of infestation as listed below (RUMA, 2010).
- - - - More cost effective (Wright, 2017).
    - - Only cost effective if combined as use against sarcoptic mange as well as A. suum, however there may be precedence to vary anthelmintics class in order to reduce risk of resistance (Wright, 2017).
- - - - However, there are limitations to this method as it requires adult worms so the disease is already manifested, also A. suum eggs are only excreted intermittently so single sampling may not prove accurate (RUMA, 2010).
    - - If milk spot lesions are evident at slaughter, this indicates the problem is occurring in the finishing area as lesions will resolve after 40 days (Wright, 2017).
      - However, low levels of lesions in the liver may represent Toxocara species rather than A. suum, particularly where there are dogs and cats present on farm (RUMA, 2010),
  - - - Worms are spread via faecal-oral recycling so basic hygiene and regular cleaning out and keeping pigs away from their faeces is an important part of management of A. suum (RUMA, 2010). #
      - All pens and farrowing huts should be systematically cleaned to control contamination levels, this should be carried out between pig batches using an all in all out concept - designed to break the cycle of disease between batches (Katakam et al., 2016).
      - Final treatment of cleaned area with the use of a flame gun or applying hydrated lime are both effective ways of killing the eggs, however both techniques have significant health and safety issues which need to be considered and weighed against benefits (Taylor, 2006; Wright, 2017).
        
        Lime washing is a hazardous procedure but is particularly useful where cracked or uneven floors or walls are present (RUMA, 2010).
      - However, Roepstorff and Nansen (1994) indicated a link between cleanliness and an increase in A. suum infection, thought to be due to the longevity and resistance to disinfectants of the eggs and the establishment of conditions (less ammonia and lower pH) better for the development of the eggs and for mechanical transfer (RUMA, 2010). #
      - A. suum eggs are known as the most resistant to the majority of conventional disinfectants and inactivation methods including chlorine, paraformaldehyde, potassium hydroxide, low-pressure UV and many more, and are harder to wash away due to their sticky coat (Oh et al., 2016; RUMA, 2010).
      - The use of steam cleaners followed by the application of detergents which can partially break down the stick outer coat may allow for the eggs to be flushed away (RUMA, 2010).
      - In outdoor pastures where strict cleaning cannot be implemented, control of worm build up should be managed through regular worming and movement of pigs to clean pastures (RUMA, 2010).
      - Katakam et al. (2016) found that farms with the strictest cleaning regimes had the lowest overall parasite occurrence.