VACCINES AGAINST BOVINE EPHEMERAL FEVER and Johnson and Martin (1974) were of the opinion that-"Few, if any, viral vaccines have proved to be more rapidly or completely effective than TC-83". Incidentally, earlier inactivated vaccines against this disease were not very effective, and unsafe in man and horses as they contained residual uninactivated virus (Spertzel 1973). Apparently man was a host more sensitive to the residual virus than were the laboratory animals used in safety tests. It must be accepted that no vaccines are entirely satisfactory and that all are capable of improvement. We should take no action that will hamper the search for better vaccines or for better means of administering vaccmes. However, where there is need we can work effectively with our present imperfect vaccines. Human smallpox, for example, has been virtually eradicated with a vaccine that could not be licensed if the initial application were made today. The risk and the cost of immunisation must be balanced against the losses attributable to the disease whose control is desired. In extreme situations, very unsatisfactory vaccines become acceptable. Koch's original bile vaccine against rinderpest was used even though it might kill 25% of the unimmunised animals. People working with hazardous agents in microbiological laboratories are inoculated with unusual vaccines that would not be acceptable or necessary for the rest of the population. Bovine ephemeral fever is not a devastating disease, but one that does cause appreciable continuing losses in Australia. Obviously more work is required, and this is proceeding, but it has been shown that protection can be induced with attenuated vaccines whose use entails no obvious risks. It would be unfortunate to see this development curtailed because the testing procedures imposed for an eventual commercial vaccine were impossible to conduct. It would also be unfortunate if unduly elaborate testing procedures were required so that the vaccine became too expensive for commercial use. Three points were listed by Della-Porta and Snowdon (1977) as prerequisites for the introduction of an attenunated bovine ephemeral vaccine. The first was the need for a cloned, genetically stable virus for use in the vaccine. There are of course no genetically stable viruses and any large viral population will contain mutants. What we should insist upon is that certain phenotypic characters, especially avirulence and immunogenicity, remain stable under the conditions used to p r e duce working vaccine from a seedlot that was itself established from cloned virus. Similar requirements would apply to the seeds from which inactivated vaccines were produced. The other 2 criteria concerned the detection of viraemia in vaccinated animals and the possible acquisition of vaccine virus by the unidentified arthropod vectors of bovine ephemeral fever virus. The point was made that laboratory methods for isolating bovine ephemeral fever virus are not highly sensitive, and if is conceivable that an arthropod vector could detect a viraemia that is not demonstrable in the laboratory. At present this hypothesis is not susceptible to experimental trial and it would be wasteful to delay further vaccine development until the vector was identified and made available for laboratory studies. Insistence on this point would prevent the development of either type of vaccine, for the tests that are applied to inactivated vaccines must be as stringent as those applied to attenuated vaccines. The procedures that are deemed insufficiently sensitive for detecting attenuated vaccine virus would be similarly insensitive for detecting residual un. inactivated virus in an inactivated vaccine. With both
It is pleasing to see that Lascelles' editorial (Lascelles 1976) is drawing a response and that an exchange Of views on the possible use of bovine ephemeral fever vaccine in Australia has been initiated in these COlUmnS by Francis (1976, 1977) and Della-Porta and Snowdon (1977). I would appreciate the opportunity to add to this debate some general remarks on viral Vaccines and to comment on specific points raised in the previous communications. The previous correspondents have discussed the relative merits of inactivated and attenuated viral vaccines. I accept the general proposition put forward by Francis ( 1976, 1977) that inactivated viral vaccines are generally inferior immunologically to attenuated viral vaccines. Consequently nearly all the viral vaccines used in animals and man are attenuated, the only inactivated vaccines in common use being those against foot-andmouth disease and influenza viruses, and the rabies vaccines used in man. These inactivated vaccines. have unsatisfactory aspects, the most important of whlch is the short period of immunity that results from a single administration. Nor can it be claimed that inactivated viral vaccines are invariably safe. In the past inactivated vaccines have contained residual pathogenic virus (poliovirus vaccines) or uninactivated contaminating virus (SV40 virus in poliovirus vaccines). The use of inactivated respiratory syncytial virus vaccines has resulted in an increased severity of illness in infants receiving natural challenge (Chanock 1970). In the United States of America the program for immunising the human population against the so-called swine influenza has been halted because of suspected neurological side effects of the inactivated vaccine (Boffey 1977). .However, each disease and each vaccine must be considered separately and the efficacy and safety of various vaccines against bovine ephemeral fever must be established by experiment. Attainable factual knowledge is of more value than theoretical considerations in evaluating vaccines. It was suggested in Lascelles' editorial that veterinary surgeons in Australia have not previously been concerned with the efficacy and safety of attenuated vaccines. This is unfair to the veterinarians in the poultry industry who have a long involvement in these matters and who have been instrumental in developing the attenuated vaccines without which OUT poultry industry could not function. The issues of vaccine safety and vaccine efficacy are not new, even in Australia. Della-Porta and Snowdon. (1977) listed a number of imperfect attenuated vaccines, and their list was obviously far .from complete. They did not point out that, despite imperfections, these vaccines are used in situations where the danger of vaccination is judged to be less than the danger of disease. Specifically, attenuated infectious bovine rhinotracheitis vaccine and attenuated mucosal disease vaccines are used in feedlots in the United States of America. Attenuated swine fever vaccines are used in many countries where virulent swine fever occurs and where eradication programs are not being undertaken. Attenuated bluetongue vaccine makes sheep rearing pmsible in some areas of South Africa and stocks of some strains of bluetongue viruses will be stored in Australia, presumably for the production of attenuated vaccines should the disease be introduced into Australia. The imperfect attenuated TC-83 vaccine against Venezuelan equine encephalitis was used to immunise horses in the face of the epizootic entering the United States of America in 1971 and the spread of the virus was halted, probably with the saving of many human lives. Millions of horses have been immunised
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vaccines, there would be the possibility of undetectible viraemia and reversion to virulence. The possibility of vaccine virus; reaching vectors would seem t o be slight as even virulent virus fails to produce detwtible viraemia after subcutaneous inoculation. This slight risk would be acceptable in areas where BEF is endemic and I suspect that a vaccine that produced viraemia would also be acceptable in such areas if it prevented disease. The comparatively recent interest of standards authorities in Australia in viral vaccines for use in animals and birds is welcome. However, one result may be that vaccine development in the future will be done in stages. The initial development will be done, as at present, by vaccine producers or by research laboratories. Those doing the initial development will often not have the resources to prepare experimental vaccines from seedlots that would be of sufficient volume to provide both experimental vaccines and many years supply of commercial vaccine. Nor, I suspect, will they have the sagacity to predict the substrates and cloning procedures that will be required or the multiplication factors that will be allowed in the eventual standard. Second stage experiments will be required when promising vaccine strains are identified and used to produce vaccine seedlots. Probably only manufacturers will have the resources to produce these seedlots, and other laboratories will be able to assist by performing tests on vaccine produced from these seedlots. We do seem to be at variance with our Victorian colleagues regarding the circumstances under which ephemeral fever vaccines might be used. We consider
that they would be used where they are needed, in areas where disease is likely to occur, and not in areas normally free of bovine ephemeral fever. This has been the practice with other viral, bacterial and protozoal vaccines in Australia. The living vaccine against contagious bovine pleuropneumonia was wed in endemic areas, as tick fever vaccines still are. The use of earlier vaccines against infectious laryngotracheitis was restricted to areas where obvious disease occurred. Vaccines are used to prevent disease, or to prevent amplifying hosts from transmitting disease to indicator hosts. Bovine ephemeral fever vaccines are required now, in areas where the disease is adding to the burdens of the cattle producer. P. B. SPRADBROW, B.V.Sc., Ph.D. Department of Veterinary Pathology and Public Health University of Queensland St Lucia, Queensland 14 June 1977 References Boffey, P. M. (1977) - Science 195: 155. Chanock, R. M. (1970) - Science 1 6 9 248. Della-Porta, A. J. and Snowdon, W. A. (1977) Aush. vet. 1. 53: 50. Francis, J. (1976) - Aust. vet. J . 52: 537. Aust. vet. J . 53: 198. Francis. J. (1977) Johnson, K: M. and Martin, D. H. (1974) - Adv. vet. Sci. cornp. Med. 18 79. Lascelles, A. K. (1976) - Aust. vet. I . 52: 381. Spertzel, R. 0. (1973) - Proc. 3rd Znt. Conf. Equine Dis., Paris, 1972. Karger, Basel, p. 146.
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DERMATOPHILOSIS OF HORSES AND CATTLE AN EARLY AUSTRALIAN REPORT underlying scabs with them. He examined these scabs wirh a microscope fitted with hn oil immersion lens (magnification up to 1000 times) and described the presence of spores and mycelia of what he termed a “vegetoid fungus”. He satisfied himself that the disease was not due to parasitic mites, ringworm or “eczema” (? Culicoides dermatitis or “Queensland itch”). This appears to be the earliest record of dermatophilosis in Australia. R. A. McKENZIE, B.V.Sc. Queensland Department of Primary Industries, Animal Research Institute, Yeerongpilly, Queensland 4105 9 June 1977 References Lloyd, D. H. and Sellers, K. C. (1976) - Forward to Derrnatophilus Infection in Animals and Man. Academic Press, London and New York, p. ix. Pascoe, R. R. (1971) - Aust. vet. J . 47: 112. Pascoe, R. R. (1972) AUSLvet. J . 48: 32. Seddon, H. R. (1965) - Diseases of Domestic Animals in Australia: Part 5: Bacterial Disease Volume 2. 2nd edn., revised by H. E. Albiston. Cwlth Dept Hlth, Canberra, p 67. Stanley, E. (1892) - Agric. Gaz. N.S.W. 3: 919.
The definitive description of bovine dermatophilosis and its causative organism, Derrnatophilus congolensis, was made in 1915 by Rene Van Sacheghem in the former Belgian Congo (Lloyd and Sellers 1976). Seddon (1965) details the known history of dermatophilosis in Australia, stating that the natural infection was first recognised in sheep in 1928 and horses in 1940. Pascoe (1971, 1972) recently emphasised the importance of this disease in Australian horses. A report was published late last century by Edward Stanley, F.R.C.V.S., Government Veterinarian for New South Wales, entitled “Epizootic Skin Disease (Prurigo) commonly known as Queensland Horse Mange” (Stanley 1892). From Stanley’s description, this disease appears consistent with dermatophilosis. Stanley’s report states that the disease had been known in Queensland for several years prior to 1887 when it spread throughout the colony during a season of unusually heavy summer rains, disappearing with the onset of winter. Stanley observed the disease in many horses and some cattle around Brisbane and Ipswich in Queensland and in the Richmond and Clarence River districts of New South Wales. He described the skin lesjons over the backline as consisting of multiple focal lesions from which tufts of hair could be plucked carrying the
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It is pleasing to see that Lascelles' editorial (Lascelles 1976) is drawing a response and that an exchange Of views on the possible use of bovine ephemeral fever vaccine in Australia has been initiated in these COlUmnS by Francis (1976, 1977) and Della-Porta and Snowdon (1977). I would appreciate the opportunity to add to this debate some general remarks on viral Vaccines and to comment on specific points raised in the previous communications. The previous correspondents have discussed the relative merits of inactivated and attenuated viral vaccines. I accept the general proposition put forward by Francis ( 1976, 1977) that inactivated viral vaccines are generally inferior immunologically to attenuated viral vaccines. Consequently nearly all the viral vaccines used in animals and man are attenuated, the only inactivated vaccines in common use being those against foot-andmouth disease and influenza viruses, and the rabies vaccines used in man. These inactivated vaccines. have unsatisfactory aspects, the most important of whlch is the short period of immunity that results from a single administration. Nor can it be claimed that inactivated viral vaccines are invariably safe. In the past inactivated vaccines have contained residual pathogenic virus (poliovirus vaccines) or uninactivated contaminating virus (SV40 virus in poliovirus vaccines). The use of inactivated respiratory syncytial virus vaccines has resulted in an increased severity of illness in infants receiving natural challenge (Chanock 1970). In the United States of America the program for immunising the human population against the so-called swine influenza has been halted because of suspected neurological side effects of the inactivated vaccine (Boffey 1977). .However, each disease and each vaccine must be considered separately and the efficacy and safety of various vaccines against bovine ephemeral fever must be established by experiment. Attainable factual knowledge is of more value than theoretical considerations in evaluating vaccines. It was suggested in Lascelles' editorial that veterinary surgeons in Australia have not previously been concerned with the efficacy and safety of attenuated vaccines. This is unfair to the veterinarians in the poultry industry who have a long involvement in these matters and who have been instrumental in developing the attenuated vaccines without which OUT poultry industry could not function. The issues of vaccine safety and vaccine efficacy are not new, even in Australia. Della-Porta and Snowdon. (1977) listed a number of imperfect attenuated vaccines, and their list was obviously far .from complete. They did not point out that, despite imperfections, these vaccines are used in situations where the danger of vaccination is judged to be less than the danger of disease. Specifically, attenuated infectious bovine rhinotracheitis vaccine and attenuated mucosal disease vaccines are used in feedlots in the United States of America. Attenuated swine fever vaccines are used in many countries where virulent swine fever occurs and where eradication programs are not being undertaken. Attenuated bluetongue vaccine makes sheep rearing pmsible in some areas of South Africa and stocks of some strains of bluetongue viruses will be stored in Australia, presumably for the production of attenuated vaccines should the disease be introduced into Australia. The imperfect attenuated TC-83 vaccine against Venezuelan equine encephalitis was used to immunise horses in the face of the epizootic entering the United States of America in 1971 and the spread of the virus was halted, probably with the saving of many human lives. Millions of horses have been immunised
Australian Veterinary Journal, Vol. 53, July, 1977
351
vaccines, there would be the possibility of undetectible viraemia and reversion to virulence. The possibility of vaccine virus; reaching vectors would seem t o be slight as even virulent virus fails to produce detwtible viraemia after subcutaneous inoculation. This slight risk would be acceptable in areas where BEF is endemic and I suspect that a vaccine that produced viraemia would also be acceptable in such areas if it prevented disease. The comparatively recent interest of standards authorities in Australia in viral vaccines for use in animals and birds is welcome. However, one result may be that vaccine development in the future will be done in stages. The initial development will be done, as at present, by vaccine producers or by research laboratories. Those doing the initial development will often not have the resources to prepare experimental vaccines from seedlots that would be of sufficient volume to provide both experimental vaccines and many years supply of commercial vaccine. Nor, I suspect, will they have the sagacity to predict the substrates and cloning procedures that will be required or the multiplication factors that will be allowed in the eventual standard. Second stage experiments will be required when promising vaccine strains are identified and used to produce vaccine seedlots. Probably only manufacturers will have the resources to produce these seedlots, and other laboratories will be able to assist by performing tests on vaccine produced from these seedlots. We do seem to be at variance with our Victorian colleagues regarding the circumstances under which ephemeral fever vaccines might be used. We consider
that they would be used where they are needed, in areas where disease is likely to occur, and not in areas normally free of bovine ephemeral fever. This has been the practice with other viral, bacterial and protozoal vaccines in Australia. The living vaccine against contagious bovine pleuropneumonia was wed in endemic areas, as tick fever vaccines still are. The use of earlier vaccines against infectious laryngotracheitis was restricted to areas where obvious disease occurred. Vaccines are used to prevent disease, or to prevent amplifying hosts from transmitting disease to indicator hosts. Bovine ephemeral fever vaccines are required now, in areas where the disease is adding to the burdens of the cattle producer. P. B. SPRADBROW, B.V.Sc., Ph.D. Department of Veterinary Pathology and Public Health University of Queensland St Lucia, Queensland 14 June 1977 References Boffey, P. M. (1977) - Science 195: 155. Chanock, R. M. (1970) - Science 1 6 9 248. Della-Porta, A. J. and Snowdon, W. A. (1977) Aush. vet. 1. 53: 50. Francis, J. (1976) - Aust. vet. J . 52: 537. Aust. vet. J . 53: 198. Francis. J. (1977) Johnson, K: M. and Martin, D. H. (1974) - Adv. vet. Sci. cornp. Med. 18 79. Lascelles, A. K. (1976) - Aust. vet. I . 52: 381. Spertzel, R. 0. (1973) - Proc. 3rd Znt. Conf. Equine Dis., Paris, 1972. Karger, Basel, p. 146.
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DERMATOPHILOSIS OF HORSES AND CATTLE AN EARLY AUSTRALIAN REPORT underlying scabs with them. He examined these scabs wirh a microscope fitted with hn oil immersion lens (magnification up to 1000 times) and described the presence of spores and mycelia of what he termed a “vegetoid fungus”. He satisfied himself that the disease was not due to parasitic mites, ringworm or “eczema” (? Culicoides dermatitis or “Queensland itch”). This appears to be the earliest record of dermatophilosis in Australia. R. A. McKENZIE, B.V.Sc. Queensland Department of Primary Industries, Animal Research Institute, Yeerongpilly, Queensland 4105 9 June 1977 References Lloyd, D. H. and Sellers, K. C. (1976) - Forward to Derrnatophilus Infection in Animals and Man. Academic Press, London and New York, p. ix. Pascoe, R. R. (1971) - Aust. vet. J . 47: 112. Pascoe, R. R. (1972) AUSLvet. J . 48: 32. Seddon, H. R. (1965) - Diseases of Domestic Animals in Australia: Part 5: Bacterial Disease Volume 2. 2nd edn., revised by H. E. Albiston. Cwlth Dept Hlth, Canberra, p 67. Stanley, E. (1892) - Agric. Gaz. N.S.W. 3: 919.
The definitive description of bovine dermatophilosis and its causative organism, Derrnatophilus congolensis, was made in 1915 by Rene Van Sacheghem in the former Belgian Congo (Lloyd and Sellers 1976). Seddon (1965) details the known history of dermatophilosis in Australia, stating that the natural infection was first recognised in sheep in 1928 and horses in 1940. Pascoe (1971, 1972) recently emphasised the importance of this disease in Australian horses. A report was published late last century by Edward Stanley, F.R.C.V.S., Government Veterinarian for New South Wales, entitled “Epizootic Skin Disease (Prurigo) commonly known as Queensland Horse Mange” (Stanley 1892). From Stanley’s description, this disease appears consistent with dermatophilosis. Stanley’s report states that the disease had been known in Queensland for several years prior to 1887 when it spread throughout the colony during a season of unusually heavy summer rains, disappearing with the onset of winter. Stanley observed the disease in many horses and some cattle around Brisbane and Ipswich in Queensland and in the Richmond and Clarence River districts of New South Wales. He described the skin lesjons over the backline as consisting of multiple focal lesions from which tufts of hair could be plucked carrying the
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