Evaluation of the influence of sprinkling powdered slaked lime on microorganisms for the prevention of domestic animal infectious diseases

When infectious diseases arise in domestic animals, a large amount of slaked lime is sprinkled on cattle sheds and their surroundings for disinfection and prevention. However, optimal sprinkling methods, standard and upper limit of slaked lime, and influence of slaked lime on non-target microorganisms remain unclear. In this study, we clarified detailed microbicidal effects of slaked lime via in vitro experiments and the influence of sprinkling powdered slaked lime (PSL) in field soil on microorganisms. In vitro disinfection tests assessing the appropriate amount of water and ventilation conditions were also performed in sterilized glass bottles with soil and Salmonella enterica subsp. enterica serovar Typhimurium. Under conditions with a small amount of water relative to the amount of PSL, the bactericidal effect and sustainability of powdered slaked lime (PSL) tended to be lower than those without spraying water. Moreover, the sterilization effect markedly decreased after 7 days under conditions with abundant water. These results indicate that the amount of sprayed water is very important for the bactericidal effect and persistence of PSL. A field experiment showed that the pH and exchange calcium (Ca) content of the soil sprinkled with over 1000 g m^-2 PSL remained high even after a long period (≥1 year), with values of approximately 0.5-1.0 and approximately 3-11 times the level without PSL, respectively. However, sprinkling PSL did not influence viable microbial counts at any concentration.

Calcinated egg shell as a candidate of biosecurity enhancement material

Calcinated egg shell (Egg-CaO), of which the main component is calcium oxide, was evaluated in the forms of powder and aqueous solutions for their efficacies as disinfectants against avian influenza virus (AIV), Newcastle disease virus (NDV), infectious bursal disease virus (IBDV), Salmonella Infantis and Escherichia coli. Egg-CaO powder inactivated these viruses within 3 min in the presence of 33% of fetal bovine serum (FBS). In Egg-CaO solutions, except AIV, all pathogens were inactivated within 1 hr, even in the presence of 5% of FBS. Without FBS, all pathogens, except AIV, were inactivated within 3 min, and AIV within 1 hr. In addition, persistence of virucidal activity against AIV and NDV of Egg-CaO powder was confirmed after exposure to sunlight for 2 weeks or resuspension with water for 7 times, simulating field harsh environments. Chick growth test was conducted to ensure the safety of the use of Egg-CaO powder in chicken cages and showed that it is safe to add Egg-CaO in litter or feed. In conclusion, Egg-CaO can be useful for the enhancement of biosecurity at farms.

Efficacy of scallop shell powders and slaked lime for inactivating avian influenza virus under harsh conditions

The efficacy and stability of scallop shell powder (SSP) were investigated, in terms of its capacity to inactivate avian influenza virus (AIV), and compared with slaked lime (SL). An environmental simulation was conducted by emulating sunlight and wet-dry conditions. The powders were collected at consecutive 2-week intervals under sunlight and upon every resuspension. These materials were tested by mixing them with AIV and incubating the mixture for 3 min or 20 h, followed by AIV titration. At the same time, a pH buffering test was conducted by neutralization with Tris-HCl. The results revealed that SSP and SL have high alkalinity and excellent ability to inactivate AIV. In a simulated harsh environment, SSP and SL retained a satisfactory ability to inactivate AIV within 20 h throughout the experimental procedure. However, SSP was able to inactivate AIV during a short contact period (3 min), even under harsh conditions, and it was more resistant than SL to neutralization.

Inactivation of avian influenza virus, newcastle disease virus and goose parvovirus using solution of nano-sized scallop shell powder

Scallop shell powder produced by calcination process − the average diameter of the powder particles being 20 µm (SSP) − was further ground into nano-sized particles, with average diameter of 500 nm, here designated CaO-Nano. Solution of CaO-Nano could inactivate avian influenza virus within 5 sec, whereas the solution of SSP could not even after 1 hr incubation. CaO-Nano solution could also inactivate Newcastle disease virus and goose parvovirus within 5 sec and 30 sec, respectively. The virus-inactivating capacity (neutralizing index: NI>3) of the solution was not reduced by the presence of 20% fetal bovine serum. CaO-Nano solution seems to be a good candidate of materials for enhancement of biosecurity in farms.