PREFACE PURPOSE I want to shed light on the occurrence of Ascaris Suum on a traditional Danish pig farm. I will focus on the morphology of Ascaris Suum eggs to establish the state of development and where in the housing they develop to the infective stage. OCCURRENCE Ascaris Suum is among the most common intestinal parasites in the Danish pig industry. According to Roepstorff and Jorsal [1989] 85 % of pig herds in Denmark are infected with Ascaris Suum. Prevalence throughout Denmark [Ropestorff et al. 1998] found to be 5.1 % piglets, 5.8 % weaners, 13.8 % growers, 20.8 % for finishers, 24.7 % gilts, 13.4 % dry sows, 10.4 % for lactating sows and 11.0 % for boars. Ropestorff and Nansen [1994] report that it is almost impossible to find an uninfected swine farm in Denmark, not even among the most well managed. Furthermore, Eriksen et al. [1981] remarks that it is impossible to avoid a build up of Ascaris Suum in experimental work with this parasite, in spite of isolation of pigs, disinfection of all work clothing, high pressure cleaning and regular anthelmintic treatment of sows and pigs not directly involved in experimentation. LIFECYCLE A.suum has a direct lifecycle. After oral intake, the Ascaris eggs 'hatch' and L2 larvae penetrate the gut, from whence they migrate to the liver through the portal veins. In the liver they develop to L3 and, after 2-4 days, they leave the liver scar formed [milk spots][interstitial hepatitis]. The L3 go with the blood to the lungs where they enter the alveolus. The larva migrate trough the trachea to the pharnyx from where they are swallowed and enters the intestinal system approximately 10 days after the eggs were ingested. Two skin changes occur in the gut while larva increase in size. 6-8 weeks after ingestion, the infection is patent and the new eggs are shed in the faeces. The newly shed eggs are ovoid 50-80 mm and have an amber brown outer appearance and small-knobbly, thick surface. This surface is very resistant to many chemical treatments and temperatures up to 50 °C [description taken from Monrad and Nansen (1994)]. REACTION TO HEAT According to Juris et al [1991], mechanical, chemical and biological waste treatment plant can extract all A.suum eggs. Tharaldsen and Helle [1989] found that all A.suum eggs are dead after 31 days in a slurry tank, agitated and kept at a constant 37 °C. Aerobic fermentation occurs. Tharaldsen and Helle [1989] referred to the article by Lündsmann [1972] that all A.suum eggs after 25 days at 40 °C are dead. Burden [1978] found that all the non- embryonic eggs are dead after 30 minutes, and 15 minutes for embryonic eggs at 55 °C. The same result [Juris et al. 1992] reached. [Barnard et al. 1987] showed, that at 50°C, all of 1.000 eggs sampled were dead after 4 hours 45 minutes. Polprasert and Valencia [1981] refer to Feachem et al. [1978] for establishing total destruction of A.suum eggs: 1 minute at 68°C, 1 hour at 50 °C, 7 days at 46 °C, 30 days at 43 °C.
Download PDF file