Inactivation of Ascaris eggs in water using sequential solar driven photo-Fenton and free chlorine.

Sequential helminth egg inactivation using a solar driven advanced oxidation process (AOP) followed by chlorine was achieved. The photo-assisted Fenton process was tested alone under different H(2)O(2) and/or Fe(II) concentrations to assess its ability to inactivate Ascaris suum eggs. The effect of free chlorine alone was also tested. The lowest egg inactivation results were found using Fe(II) or H(2)O(2) separately (5 and 140 mmol L(-1), respectively) in dark conditions, which showed about 28% inactivation of helminth eggs. By combining Fe(II) and H(2)O(2) at the same concentrations described earlier, 55% of helminth egg inactivation was achieved. By increasing the reagent's concentration two-fold, 83% egg inactivation was achieved after 120 min of reaction time. Process efficiency was enhanced by solar excitation. Using solar disinfection only, the A. suum eggs inactivation reached was the lowest observed (58% egg inactivation after 120 min (120 kJ L(-1))), compared with tests using the photo-Fenton process. The use of the photo-Fenton reaction enhanced the process up to over 99% of egg inactivation after 120 kJ L(-1) when the highest Fe(II) and H(2)O(2) concentration was tested. Practically no effect on the helminth eggs was observed with free chlorine alone after 550 mg min L(-1) was used. Egg inactivation in the range of 25-30% was obtained for sequential processes (AOP then chlorine) using about 150 mg min L(-1).

Inactivation of Ascaris eggs in soil by microwave treatment compared to UV and ozone treatment.

This study reports on the effect of microwave radiation for inactivation of Ascaris lumbricoides eggs in 25 g of soil compared to ultraviolet irradiation and ozone expose. Microwave radiation at 700 W with 14% water content (w/w) achieved approximately 2.5 log inactivation of eggs in soil within 60s. On the other hand, UV irradiation at 3 mW cm(-2) with and without shaking soil for 3600 s achieved approximately 0.32 and 0.01 log inactivation of eggs, respectively. In ozone treatment, 0.13 log inactivation of eggs was achieved with 5.8+/-0.7 mg L(-1) of dissolved ozone dose for 30 min in a continuous diffusion reactor. In addition, the inactivation of eggs by three disinfection techniques was conducted in water in order to compare the inactivation efficiency of eggs in soil. The inactivation efficiency of microwave radiation was found to be no significant difference between in soil and water. However, the inactivation efficiency of UV irradiation was significantly increased in water while in ozone expose there was no significant difference between in soil and water. Microwave treatment thus proved to be the most efficient method in controlling A. lumbricoides eggs in soil.

Irradiation of Ascaris ova in sludge using an electron beam accelerator.

The efficiency of sludge disinfection by irradiation was investigated using an electron beam accelerator, with the Ascaris ovum as a model. Ova suspensions prepared by worm dissection, immediately after preparation and after storage at 4 degrees C for 2 months were tested. Suspensions of ova extracted from slaughterhouse sludge were also tested. The ova were irradiated in sludge to determine, by probit analysis, the dose that inactivated 90% of viable ova. The D10 values obtained for irradiation of residual sludge contaminated with ova depended on the source of the ova, the D10 values were 788 +/- 172 Gy for suspensions of ova extracted from slaughterhouse sludge and 1125 +/- 145 Gy for suspensions freshly prepared by dissection. Ova suspensions freshly prepared by dissection were more proof against irradiation. Similarly, the D10 value was affected by storage: 1125 +/- 145 Gy for freshly produced ova suspensions and 661 +/- 45 Gy for suspensions of ova stored for 2 months at 4 degrees C in deionized water. The medium in which the ova were irradiated (deionized water or sludge) also affected D10 values, the indirect effects were smaller in samples of contaminated sludge, which were rich in organic matter, with the action of the radiation being mostly direct.

An ultraviolet-attenuated egg vaccine for swine ascariasis: parameters affecting the development of protective immunity.

Pigs inoculated with UV-irradiated Ascaris suum eggs developed immunity against challenge exposure with A suum infective eggs. Trials were conducted to determine the optimal conditions necessary to induce high levels of protective immunity and minimize liver lesions related to larval migration. Protective immunity was defined as the percentage of reduction in the recovery of larvae from the lungs of inoculated pigs, compared with controls, 7 days after challenge exposure with 5 X 10(3) or 10(4) infective eggs. Initial experiments showed that protective immunity was higher in pigs inoculated orally with UV-irradiated eggs than in those inoculated intraperitoneally. The highest level of protection (94%) was obtained by immunization with 5 oral inoculations of 10(4) eggs that had been UV-irradiated at total energy doses (ET) of 150, 100, 75, 75, and 75 mu W-min/cm2, respectively. A level of 83% protection was induced with as few as 2 oral inoculations of eggs irradiated at 150 and 75 ET, respectively. However, protection was reduced when pigs received eggs that were irradiated at and above 400 ET. The minimum number of irradiated eggs required to induce significant (P less than 0.05) protection was determined by feeding pigs 10(4), 10(3), or 10(2) eggs irradiated on 3 consecutive weeks at 150, 100, and 75 ET; the levels of protection induced were 94%, 89%, and 83%, respectively. Pigs inoculated with equal numbers of UV-irradiated eggs or normal eggs developed a similar level of protective immunity after challenge exposure. However, worms developing from the inocula were detected in the intestines of some of those pigs that had received normal eggs, but not in those pigs given UV-irradiated eggs.

Immunization of pigs against experimental Ascaris suum infection by feeding ultraviolet-attenuated eggs.

Pigs fed Ascaris suum eggs attenuated by short-wave ultraviolet radiation developed a resistance to challenge infections that varied according to the protocols used. Two doses of eggs irradiated at total exposures (ET) of 150 muW-min/cm2 resulted in a reduction of adult worm burden in 3 groups challenged with 50, 100, or 500 eggs by 45, 35, and 49%, respectively. However, these results were not statistically significant (P greater than 0.05). Three other groups were fed eggs as follows: Group 1, 3 doses irridated at ET's of 150, 150 and 150; Group 2, 3 doses irradiated at ET's of 150, 150, 100; and Group 3, 3 doses irradiated at ET's of 150, 100, and 75. All of these regimens provided significant protection: Group 1 (P less than 0.02), Group 2 (P less than 0.05), Group 3 (P less than 0.001). An analysis of the lengths of worms recovered showed that in controls fed varying doses of eggs, worm sizes were inversely related to the number of eggs in the challenge dose. Measurements of worms from vaccinated animals showed that 23 of 116 adult worms recovered were probably survivors of one or more of the vaccinating doses. A ratio of 18 female to 5 male worms indicated that males are more susceptible to ultraviolet radiation than females.

[The destruction of parasitic resistant stages in sludge by irradiation with low accelerating voltage electrons (author's transl)]. / Die Vernichtung parasitärer Dauerformen im Klärschlamm durch Bestrahlung mit niederenergetischen Elektronen

The destroying effect of ionizing radiation on parasitic resistant stages in sludge has been tested. Suitable for that process is an electron beam accelerator which will be provided with energy from the electric power supply network which can be switched on and off according to the requirements. Such modern utilities have an enormous beam capacity and a high operating safety. The process is working according to the continuous flow principle and at room temperature. In a series of 13 experiments the effect of different doses has been tested. A dose of 480 kRad (accelerating voltage; 400 kV, beam current; 10 mA, irradiation time: 24 sec.) can easely obtained in practical work and is economically acceptable. By these means approximately 97% of the following parasitic stages have been destroyed: undeveloped eggs of Ascaris suum, Trichuris suis, Fasciola hepatica and gastrointestinal strongylids of pigs, embryonated eggs of Capillaria obsignata and probably of Taenia spec. A few third-stage larvae of Oesophagostomum (Strongylidae) of pigs survived even 108 sec of irradiation; however, they did not develop to maturity in the definitive host. Approximately 25% of the sporulated oocysts of Eimeria renella were still infective after 108 sec of irradiation.