[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Calculating infectivity of BSERe: BSE/22D

At 09:47 AM 4/23/97 -0400, Antonio wrote:
>I reached the 22D value on the following basis:
> "The contamination level of cow brain can be expected
> to be about ten to eleven (10^11) prions / g [Brown et al., 1982].
> The nervous system is about  1/1000th of the body weight.
> Then we may consider the maximum level of infected beef
> contamination to be about  ten to eight (10^8) prions/g,
> irrespective of the tissue type. One hundred grams (a portion)
> of beef will hold about 10^10 (ten to ten)prions. Then the
> minimum number of D required to sanitize 100g beef would
> be ten D (10D). The total number of D  rises to 10+12=22D
> to meet the usual basic requirement of a  low survival
> probability 10^ -12 (ten to minus twelve = the  minimum
> botulinum cook) and to assure an acceptable remote
> probability of infection by BSE prions.
> Antonio

This argument is flawed.

Assuming, as you do, that the infectivity can be presumed to be a maximum
of 10^11 prions/g in the worst-case (brain), and that the central nervous
system is the only infectious tissue of consequence, then the "whole
animal" infectivity could be expected to be 10^8 prions/g.

Assuming, as you do, that ground beef exhibits the average carcass prion
rate,  then a 100 g portion would contain 10^10 prions. Also assuming, as

[110 lines left ... full text available at <url:http://www.reference.com/cgi-bin/pn/go?choice=message&table=04_1997&mid=3819570&hilit=BRAIN+BRAINS+FEEDBACK> ]

Article-ID: 04_1997&3826312
Score: 78
Subject: Re: DVORAK typing