The agents of scrapie and BSE are extremely resistant to physical and chemical influences. Compared with the conditions during gelatin production, in experiments they withstood an acidity, which was ten times as high, an alkaline concentration twenty times as high and a drying temperature that was about 220°C higher. As the procedures of gelatin production can not be tightened up without significant losses of yield and quality, gelatin can only be produced safely from healthy animals. In order to get a reliable test for the agent in man, animal, and raw material, it has to be shown, whether the altered prion protein is identical with the agent. Therefore a simple experiment has been proposed, by which the prion theory can be proved or refuted within a few days.
Gelatin is a primary product with an extraordinary wide field of application, used for quality improvement of innumerable foodstuffs and medicaments. It serves for supplementary source of protein, carrier material, bonding agent, stabiliser and emulsifier. It is also used as an aid for frothing up, flavour enhancement, common salt replacement, clearing of drinks and as a collagen source for dietetics.
It can be found in jelly, jellied meat and aspic, in ice cream, some margarines, sweets like gummy bears, soft caramels, marshmallows, meringues, liquorice and cream-filled chocolate cakes, in gateau fillings and desserts, in milk products like yoghurt and creames as well as in pies and convenience food. Cream and foam are often made of jelly with beaten egg white, whipped cream or curd.
Quality-tested wines, cider, apple juice and in some countries also beer, are freed from blurrings, tannin agent and bitter constituents with the help of gelatin. From fizzy drinks it is not removed at all. In milk-shakes with fruit or vegetable additives gelatin prevents the milk from curdling. Vegetable juices are thickened with gelatin and enriched with vitamins and minerals. In tinned meat gelatin binds the meat juice. In some cases salami and pepper sausage are protected from drying up by gelatin.
The pharmaceutical industries use gelatin in soft and hard medicament capsules, for binding in tablets and dragees, in form of sponges for treating wounds and as a colloid to expand the plasma after severe losses of blood. They are also included in vitamin compounds and cosmetics. People having problems with their nail growth or with their joints and cartilage are treated with gelatin. Animal food industries sometimes use gelatin in substitute milk products for calves. As gelatin is so omnipresent, nobody in the industrial nations can avoid its assimilation. Therefore even vegetarians have to doubt whether the production of gelatin from slaughter wastes of pigs and cattle totally removes BSE infectivity.
The World Health Organization writes in its data sheet 113 and in the report WHO/EMC/DIS/96.147 about the conference on April, 2 and 3 1996 in Geneva they held together with the FAO and the OIE (Office International des Epizooties) on human and outher transmissible spongiform Encephalopathies: "Gelatin in the food chain is considered to be safe if produced by a manufactoring process utilizing production conditions which has been demonstrated to significantly inactivate any residual infectiviy".
This is as true as it is trivial. Unfortunately there is no sensitive test for low titers of infectivity, so that this condition can not be fulfilled. The reasons are the short lifespan of rodent recipients and the necessity to overcome the species barrier between cattle and rodents.
The Press Release WHO/28 - 3 April 1996 (Rev.1 15 April 1996) garbles this insignificant but true assessment to a misleading and scientifically untenable contention: "Gelatin is considered safe for human consumption since its preparation involves a chemical extraction process that destroys BSE infectivity". BSE-infectiousness is also destroyed during cooking and baking, but nevertheless anyone with a bit of sense would not eat the cooked brain from a cow which died of BSE. This attitude is especially questionable, as WHO knew about a scottish study which had been ordered by the European gelatin industries in Scotland in 1993. A scaled-down simulation of the acid and the lime treatment, the two chemical key stages in the manufacturing process of gelatin, did not reveal any reduction of scrapie infectivity.
Likewise in the report WHO/EMC/DIS/96.147 it is explicitly pointed out, that parts of cattle destined for the pharmaceutical industries should only be bought from practically BSE-free countries. The reason is the fact that the applicable inactivating procedures can only reduce the risk of infection with the BSE agent, which is extremely resistant to physical and chemical influences. The European Agency for the Evaluation of Medical Products in London decided, that gelatin for medicaments should not come from cattle slaughtered in Britain.
British slaughter wastes contain considerable amounts of infectivity and there is no manufactoring process utilizing production conditions which has been demonstrated to significantly inactivate any residual infectiviy. Nevertheless EU-commissioner Franz Fischler pushed through a lifting of the export ban for British gelatin, on condition that it is produced according to the procedure applied by the German gelatin factories Stoess AG [6]. Therefore it is interesting to compare the conditions of this procedure with those of the experiments, which the agents have demonstrably withstood.
About 65 % of the world-wide produced gelatin comes from hidesplits, connective tissue and the bones of cattle [6]. Otherwise pigs serve for source material [6]. Only in Australia, South Africa and New Zealand also sheep are used [6]. The quality of the gelatin is influenced by the source of supply, which in Europe traditionally is mainly from pigs in the case of gelatin for food and medicaments [6].
There is such a huge demand of raw material, that a limitation to very young or especially natural living animals is not possible [6]. But at least in Germany only slaughter wastes from animals, which are released for human consumption, are used for the production of gelatin for food and medicaments. Because however, up to now BSE can only be diagnosed very lately, most of the infected animals are not identified. Thus the veterinarian's check-up before slaughtering does not provide a remarkable protection against BSE and scrapie.
It is obvious, that hidesplits, connective tissues and bones of BSE-infected animals are far less infectious than the central nervous system. But as long as the agents are not definitely identified and not detectable by any sensitive test, not any tissue and body liquid can seriously be declared free of infectivity. Skin and bones from infected animals must also be supposed to be infectious, because they are well supplied with blood and nerves. The infectivity of blood has been demonstrated as early as 1962 with a goat [5] and among others in 1992 with human beings [7]. That this did not work with cattle until now, is due to the very low sensitivity of the common functional test and absolutely insufficient efforts made in this concern.
The 10-15 kg raw material from one cow disappear in production batchs of 20,000 to 100,000 kg. It is then diluted with other gelatin about the factor 10-100 to achieve the final products [6]. Thus the agent is certainly diluted to a great extent, but at the same time it is distributed to a very large number of end products.
Bones are splintered into pieces of less than 12 mm diameter. Their fat content becomes reduced to below 2% with hot water and then they are dried for a minimum of 30 minutes at a temperature of well over 100°C [6]. This procedure removes much of the infectiousness of the raw material, but certainly not all of it.
The cleaned pieces of bone are freed from phosphate minerals with 4% hydrochloric acid, at a pH below 1.5, so that only the collagen structure remains [6]. This procedure takes five days, but begins with an already used, more diluted hydrochloric acid, which becomes replaced by a fresh one only toward the end of the treatment [6]. The finally reached pH 1.5 corresponds to a concentration of less than 0.1 M hydrochloric acid. Unfortunately, the effect of this long-lasting treatment with a weak acid on the BSE agent has never been published yet.
According to one publication however, the effect of acids in contrast to strong caustic solutions seems to be only temporary [3]. In an experiment the treatment with 1 M hydrochloric acid turned out to be insufficient [2]. This indicates, that the acid treatment during the gelatin production is quite probably not adequate to inactivate the agent.
More than 90 % of the gelatin won from cattle receives an additional treatment. It normally takes about 50 days with pH higher than 12.5 to open cross connections between the collagen molecules [6]. Even a pH 13 corresponds to a sodium hydroxide concentration of only 0.1 M. Sometimes the incubation time is being shortened from 50 to 14 days by increasing the concentration up to 0.3 M [6]. As the infectivity is not fully inactivated by 2 M sodium hydroxide [8], this lime treatment cannot be considered to be safe. The non published scottish study which had been ordered by the European gelatin industries demonstrated no measurable reduction of scrapie infectivity after days of treatment with acid or lime (personal communication). Furthermore the lime treatment is only applied for raw material from cattle [6]. The delicate skin of young pigs is not treated with the caustic solution. For them an acid treatment during one day is sufficient. The effect on BSE agents however is comparable to the demineralization of bones.
After having been extracted step by step with water of increasing temperature, the gelatin is sterilized at 140°C for 4 seconds. Of course, also this treatment is not suitable to fully inactivate the BSE-agent. This was demonstrated by an experiment, in which brain samples with an average weight of 340 g were autoclaved during 1 hour at 134°C or for at least 18 minutes at temperatures of 135°C or 134-138°C. This was not sufficient either to inactivate scrapie- and BSE agents. So 14 out of 22 mice fell ill from the brain of hamsters which had been autoclaved during 1 hour at 134°C. Hamster brain that had been autoclaved at 134-138°C during 18 minutes, killed all of 19 mice. It is interesting that a longer period of time of autoclaving does not result in a more efficient inactivation. Although autoclaving reduced the infectiousness by 7 orders of magnitude, it was still fit for lethal infections. Drying material is even more difficult to sterilise. Amylid fibrils from scrapie-infected brains of hamsters remained infectious after autoclaving and partially even after one hour at 360°C [1].
On the whole the procedures used for gelatin production certainly are suited to reduce the infectiousness of BSE-contaminated raw material. But it is just as certain, that hereby a complete inactivation is not possible. There is not any indication that a minimun dose is required for the transmission of BSE to other species.
On the contrary, the characteristic stability of the agent and the defenselessness of the immune system seem to indicate, that extremely small doses up to only one single molecule could be enough for an infection. On the other hand, from all the cattle that got infected foodstuff and the thousands of recipients of infectious growth hormone, only comparatively few fell ill. Thus there must be an individually different, but unknown lethal dose.
Not mortally infected human beings and animals can nethertheless represent sources of infection. Therefore it is important to distinguish lethal from sublethal infections, and at the same time the non-mortal infections have to be recognized much more as a problem.
From the scientific pont of view it is surprising, that until now there has been published no simulation of the gelatin manufacturing process with highly infectious material.
This would be necessary to calculate the degree of agent inactivation. To detect even very low levels of infectivity, we need a for example immunologic system, that directly marks the agent instead of functional tests with the injection of test material into the brains of mice. Beforehand however, the agent has to be identified. Therfore scientists have been searching for a scrapie virus since decades. This approach was without success and by combining available facts, the virus-theory can already be excluded [4].
If the prion theory was right, we would already know quite a lot about the agents and we could immediately detect them with available antibody-tests. Unfortunately this already fairly old theory has not been proved or refuted despite of numerous attempts. However, this could be done within a few days, with an experiment, which in principle has been published repeatedly. It only has to be carried out and analyzed somewhat more sophisticated.
Therefore one has to mix radioactively labelled prion proteins with infectious material in a test tube and to record the increase of amount of protease resistant and labelled prion protein.
According to the virus-hypothesis this increase would be at most linear, because only driven by the added infectious material, which could not reproduce. In accordance with the prion-theory the newly transformed prion protein would contribute to conversion of the rest. In that case an accelerating increase of the protease resistant and radioactive prion protein could be observed, until the reserves of normal prion protein will run out.
1) Brown,P.; Liberski,P.P.; Wolff,A.; Gajdusek,D.C. - Resistance of scrapie infectivity to steam autoclaving after formaldehyde fixation and limited survival after ashing at 360 degrees C: practical and theoretical implications. - Journal of Infectious Diseases 1990 Mar; 161(3): 467-72
2) Brown,P.; Rohwer,R.G.; Gajdusek,D.C. - Newer data on the inactivation of scrapie virus or Creutzfeldt-Jakob disease virus in brain tissue - Journal of Infectious Diseases 1986 Jun; 153(6): 1145-8
3) Gasset,M.; Baldwin,M.A.; Fletterick,R.J.; Prusiner,S.B. - Perturbation of the secondary structure of the scrapie prion protein under conditions that alter infectivity - Proceedings of the National Academy of Sciences of the United States of America 1993 Jan 1; 90(1): 1-5
4) Heynkes,R. - Rinderwahnsinn - Durch die moderne Medizin erst gefährlich - Therapiewoche 1995; 15: 886-92
5) Pattison,I.H.; Millson,G.C. - Distribution of the scrapie agent in the Tissues of experimentally inoculated goats - Journal of Comparative Pathology and Therpeutics 1962; 72: 233-44
6) Schrieber,R.; Seybold,U. - Gelatine production, the six steps to maximum safety - Developments in Biological Standardization 1993; 80: 195-8
7) Tamai,Y.; Kojima,H.; Kitajima,R.; Taguchi,F.; Ohtani,Y.; Kawaguchi,T.; Miura,S.; Sato,M.; Ishihara,Y. - Demonstration of the transmissible agent in tissue from a pregnant woman with Creutzfeldt-Jakob disease [letter] - New England Journal of Medicine 1992 Aug 27; 327(9): 649
8) Taylor,D.M.; Fernie,K. - Exposure to autoclaving or sodium-hydroxide extends the dose- response curve of the 263k strain of scrapie agent in hamsters - Journal of General Virology 1996; 77(APR): 811-3
9) Taylor,D.M.; Fraser,H.; McConnell,I.; Brown,D.A.; Brown,K.L.; Lamza,K.A.; Smith,G.R.A. - Decontamination studies with the agents of bovine spongiform encephalopathy and scrapie - Archives of Virology 1994; 139(N3-4): 313-26
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