Virolysis of feline calicivirus and human GII.4 norovirus following chlorine exposure under standardized light soil disinfection conditions.

The relationship between the infectivity of the feline calicivirus (FCV) vaccine strain F-9 and capsid destruction (virolysis) in response to available chlorine was investigated under standardized light soil disinfection conditions. Virolysis was measured using RNase pretreatment (in order to destroy exposed RNA following chlorine treatment) and quantitative reverse transcription PCR. A comparison between the results of plaque assays and virolysis following exposure of FCV F-9 grown in tissue culture to different concentrations of available chlorine showed a similar log-linear relationship, with >4-log reductions occurring at 48 and 66 ppm, respectively. Three non-epidemiologically linked human GII.4 noroviruses (NoVs) present in dilute clinical samples showed behavior similar to each other and were 10 times more resistant to virolysis than cultured FCV F-9. FCV F-9 when present in dilute human GII.4 samples acquired increased resistance to virolysis approaching that of human NoVs. This study represents a direct comparison between the virolysis of a surrogate virus (FCV F-9) and that of human GII.4 NoVs within the same matrix in response to available chlorine. The results support the view that matrix effects have a significant effect on virus survival.

Measurement of the virolysis of human GII.4 norovirus in response to disinfectants and sanitisers.

The aim of this study was to develop a method for investigating the stability of the human NoV capsid in response to disinfectants and sanitisers (virucides) as an indirect method for determining virus infectivity. Capsid destruction or "virolysis" was measured using the reverse transcribed quantitative PCR (RT-QPCR) reaction in conjunction with RNase treatment (in order to destroy any exposed RNA). Two commercially available alcohol based handwashes, alcohols (75% (v/v) ethanol or isopropanol), quaternary ammonium compounds (0.14% BAC or 0.07% DIDAC), and chlorine dioxide (200 ppm) were all ineffective at promoting virolysis of human norovirus present in dilute clinical samples at the concentrations tested. GII.4 NoVs were sensitive to a combination of heat and alkali. These data show that NoVs present in dilute stool samples are resistant to virolysis using virucides that are used commonly.

Disinfection of stockyards.

Stockyards are premises where livestock from different sources are brought together for a period of time, before returning to their place of origin, or moving on to new premises or to the abattoir. Such premises pose particular problems for disease control, as they are potential sources for the dissemination of disease agents over wide geographical areas. The author describes a thorough programme of cleaning and disinfection for use during the routine operation of a stockyard. A different programme is described for use in the event of an outbreak of an Office International des Epizooties List A disease, taking into account the extra risks involved in such a disease outbreak.

Disinfection of livestock production premises.

Livestock production premises (e.g. barns, and pens for lambing, calving, weaning and holding animals) encounter disease problems mainly associated with the housing of new-born and young animals, pregnant females and suckling mothers. The author describes a programme of cleaning and disinfection for use during the routine operation of livestock premises. A further programme is described for use in the event of an outbreak of an Office International des Epizooties List A disease, taking into account the particular problems associated with this type of disease.