LETTERS TO THE EDITOR THE VETEXINARIAN A N D PRIVATE ENTERPRISE SOCIETY I refer to the letters of Frost and Morris in the The advice given to young people seeking career October Journal. 1 had not completely understood the information. Any fair minded veterinarian giving advice t o high school students should point out the expression ‘ivory tower’ until I read these letters. Both correspondents have overlooked the simple fact that we probability of them being unemployed after graduareside in an elitist and private enterprise society. The tion. supply of veterinary surgeons will be dictated -by the All these pressures could lead. within 5 years, to a demands of the market place. Crude statistics which scenario in which only those affluent families, which equate supply with the number of places in the schools can support the costs of university education, plus a few bear no relationship to what will really happen in prac- ultra poor families with brJliant youngsters, able to tice. There were numerous places available in the obtain government allowances, will provide the entrants veterinary schools in the 1920’s but few candidates for to the veterinary schools. In an elitist and private the honour of spending several years studying for a enterprise society following the dictates of the market veterinary degree. The Melbourne school closed because place, this is how it should be. Who better than veterinit had no students. Already sevcral factors are at work, arians to appreciate the law of the jungle. which will wind down the graduate mill. The principal ones are: J. H. AUTY, M.V.Sc., M.A.C.V.S., Dissatisfaction with the universities by an increasing 1 Nardoo Street, number of young people. Reduction in the living standards of university OConnor, Australian Capital Territory, 2601 students by deliberate government action. 5 November 1976 VAClCINES AGAINST BOVINE EPHEMERAL FEVER Recent discussion in the Australian Velerinory Journal ephemeral fever is considered an exotic disease, it was (,Lascelles 1976; Francis 1976) concerning the use of important that any vaccine to be used in normally BEF live “attenuated” and killed vaccines against bovine free areas should be completely safe otherwise it could ephemeral fever (BEF) has prompted us to reply. In jeopardise our existing exports from otherwise safe this reply we shall put forward our reasons for investigat- areas. At the time we decided to examine the possibility of ing a killed vaccine against B E F and suggest some minimum safety standards which we believe a live a BEF vaccine there was some doubt as t o whether attenuated vaccine against BEF should meet before being there was an urgent need for vaccination. In other words the rapid production of a vaccine which might be used extensively in the field. It is not our intention to comment in detail on the of doubtful safety, was not acceptable to us. While being completely aware of the benefits that have contents of the Francis (1976) letter; however it is important to correct one inaccurate statement and com- accrued from the use of live vaccines, we were also ment upon another. Snowdon (1970) did report upon aware that with very few exceptions, such as the present the protection of cattle using attenuated BEF virus. Dr tissue culture derived rinderpest vaccine, many of these B. J. Erasmus did give his support to an attenuated vaccines have undesirable attributes. A few examples of vaccine apainst bovine ephemeral fever at the Symposium live “attcnuated” vaccines which have caused problems on Bluetongue at the Annual General Meeting of the are given below: Australian Veterinary Association in Adelaide in May Live vaccines against infectious bovine rhinotracheitis (IBR) virus are known to have caused 1974. However, when asked subsequently whether he would use a live BEF vaccine in normally BEF free abortion in pregnant cows (McFeely et a1 1968). areas, he qualified his statement by saying that the There is a body of opinion in North America that believes the use of this vaccine has made a significant vaccine would need to be shown to be entirely safe. When considering whether we should research and contribution to the IBR abortion problem in that country (J. Kendrick, personal communication). develop live or killed vaccines for the control of BEF, Live vaccines against the mucosal disease-virus the following were important considerations in arriving diarrhoea complex viruses have produced untoward at the decision to concentrate on investigating the feasisequelae in vaccinated cattle (Peter et a1 1967). bility of a killed vaccine. At the time we decided to investigate a killed BEF Attenuated or modified live virus vaccines against hog cholera are known to have caused disease in vaccine, the virus had not been recovered from arthrovaccinated pigs and in some cases been transmitted pods. and hence the more extensive investigations of proving which arthropods were vectors of the disease to “in contact” susceptible pigs (Phillips 1966; could not be undertaken. Proving the safety of a live Zinober and Mott 1966). Some of these vaccines vaccine would, in our opinion, always be suspect unless were also demonstrated to revert to virulence on i t could be demonstrated that the virus would not revert passage through pigs (Torrey et a1 1960). In fact, to virulence on passage through its arthropod vector(s). one cf the major factors in the eradication of hog The disease is enzootic in northern Australia and large cholera in the United States of America was the epizootics occur at intervals in eastern and south eastern outlawing of vaccination (Dunne 1975). Aus’ralia. We saw the need for an absolutely safe Attenuated bluetongue virus has produced convaccine that might be used in areas where epizootics genital abnormalities in the progeny of vaccinated occurred irregularly and which could be used in dairy pregnant ewes (Shultz and DeLay 1955; Young and cattle, bulls and valuable stud animals in the face of an Cordy 1964). Furthermore, Foster et a1 (1968) outbreak. demonstrated that C u k o i d e s vuriipennis when fed With the development of a significant export trade on sheep that had received live attenuated Type 10 in cattle and semen from Australia to areas where vaccine were able to transmit bluetongue disease to 50

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susceptible sheep. These authors concluded that “In light of the results of the serial transmission tests in sheep with Culicoides variipennis as the vector, use of a modified live-virus vaccine in bluetonguefree areas may set up new foci of infection”. The attenuated vaccine strain TC83 of Venezuelan equine encephalitis virus was isolated from a pool of Psoroplrora corrfinriis mosquitoes collected during the 1971 epizootic in the United States of America (Pedersen er a/ 1972). The same vaccine strain has been shown to revert to virulence during passage through horses (Luedke et id 1972). Efforts were made over many years to produce safe and effective live vaccines against foot and mouth disease ( F M D ) . but these failed. However, with, modern methods of producing killed F M D vaccines, combined with their widespread and regular use in catt!e, the disease has virtually disappeared from most Western European countries. These examples only serve to illustrate the need to be completely objective in considering the use of live attenuated vaccines. All live vaccines are not potent and safe vaccines, just as all killed vaccines are not potent immunizing agents. The rapid “attenuation“ of ephemeral fever virus after 3 to 5 passages in mice or 3 to 9 passages in cell culture (Van der Westhuizen 1967; Snowdon 1970: Tzipori and Spradbrow 1973; Tzipori et a/ 1975) would certainly suggest that this virus does not have great stability. Perhaps the reason for this apparently rapid attenuation is not that the virus has mutated, but that the production of defective-interfering particles (Tzipori 1975; DellaPorta and Snowdon, unpublished data) has affected the infectivity of the virus. This has been suggested for other members of the rhabdovirus group (Huang and Baltimore 1970). We commend the Australian Meat Research Committee in funding research into both attenuaed and killed BEF vaccines. The results of our work and that of D r Spradbrow and his colleagues suggest that possibly the only feasible method of immunizing cattle against BEF at the present time is to use a live virus. However, the fact that a killed vaccine can produce high levels of neutralising antibody without producing resistance to challenge ( Della-Porta and Snowdon, unpublished data ) indicates that the assessment of resistance to BEF based upon antibody responses alone must be re-examined. We also commend the work of Dr Spradbrow and his colleagues. but will be always cautious of accepting live BEF vaccines until: A c!oned. genetically stable virus is wed in the vaccine. The vaccine has been shown not to produce a viraemia. Negative results already obtained are suspect because of the lack of sensitivity of available laboratory systems.

It has been demonstrated that the vaccine virus on passage through the arthropod vector(s) does not revert to virulence. Finally we believe that adequate standards need to be set to test both the safety and the efficiency of animal virus vaccines to be licensed for use in Australia. We would agree with Francis (1976) that a committee, in consultation with the National Biological Standards Laboratory, similar to that which is considering poultry vaccines. should draw up such guidelines. The deliberations o l this committee would assist the Chief Veterinary Officers when considering the licensing of vaccines for use in Australian livestock. A. J . DELLA-PORTA. B.Sc.. Ph.D. W. A. SNOWDON, B.V.Sc. CSIRO Division of Animal Health, Animal Health Research Laboratory, Private Bag No. I , P.O., Parkville, Victoria, 3052 2 D w e t ~ ~ h c1976 r Rderenees Dunne, H. W. (1975)-in “Diseases of Swine”, (Ed. Dunne. H. W. and Leman, A. D.) 4th edn, Iowa State Univ. Press, Anies, Iowa. Ch. 8. Foster, N. M., Jones, R. H. and Luedke, A. J . (1968)A)),. J. vet. Rrs. 29: 275. Francis, J . (1976)--Aust. vet. J . 52: 537. Huang, A. S. and Baltimore. D. (1970)-Nriture, Lorid. 226: 325. Lascelles. A. K. (1976)--Acts/. v e t . J. 52: 381. Luedke, A. J., Barber, T. L., Foster, N. M., Betalla, D. and Mercado. S. (1972)-J. Am. vet. rtied. Ass. 161: 824. McFeely, R. A., Merritt, A. M. and Slearly, E. L. (1968)-J. An?. vet. nwd. Ass. 153: 657. Pedersen. C. E., Robinson, D. M. and Cole, F. E. (1972)-Ani. J. Epidemiuf. 95: 490. Peter, C. P.. Tyler, D. E. and Ramsey, F. K. (1967)J. Atrr. vet. tried. Ass. 1 5 0 46. Phillips, C. E. (1966)--Proc. U.S. l i v e Srk scrnit. Ass. 70: 302. Shultz, G . and DeLay, P. D. (I955)-J. Am. vet. r n d . Ass. 127: 224. Snowdon, W. A. (1970)-Airst. vet. J . 46 258. Torrey, .I.P., Zinober. M. R. and Amtower, W. C. ( 1960)--Proc.. US. live Stk sanit. Ass. 64: 298. Tzipori. S. (1975)-Aicst. J. exp. B i d . tried. Sci. 53: 273. Tzipori, S. and Spradbrow, P. B. (1973)--Arr.t/. l*er. 1. 49: 183. Tzipori, S., Spradbrow. P. B. and Doyle, T. (1975)Aust. ve/. J. 51: 244. Van der Westhuizen. B. ( 1967)-0nderstt,~no,.r. J. r’et. Res. 34: 29. Young. S. and Cordy, D. R. ( 1 9 6 4 k - J . Nrrtropir/li. e.tp. Neurol. 23: 635. Zinober, M. R. and Mott, L. 0. (1966)--Pror. U.S. live Stk soriir. A.s.s. 70: 3 10.

AKABANE DISEASE: ISOLATION OF THE VIRUS FROM NATURALLY INFECTED OVlNE FOETUSES Two centinel flocks of ewes have been maintained near Epizootics of congenital ovine micrencephaly ( M E ) have been observed in south-eastern New South Wales Sydney, at Bringelly and at Badgery’s Creek respectively, (Hartley and Haughey 1974) and in Israel (Nobel e l a1 since late 1974. There were approximately 50 ewes in 197 1). Outbreaks of congenital bovine arthrogryposis each group and their serums contained no neutralising ( A G ) and hydranencephaly ( H E ) have also been antibodies against Akabane virus. The ewes were bled observed in the same areas (Hartley and Wanner 1974; at regular intervals, usually monthly, and their serums Nobel et d 1971). In New South Wales the bovine tevted for the presence of neutralising antibodies against deformities have been linked with congenital infection 25 fifty-per cent tissue culture infective doses (TCID-,) of Akdbane virus strain B8935 (Doherty 1’1 N / 1972), with Akabane virus (Hartley et a1 1975). Aic.ttrcrliur~ Veterinary Joitrtial, Vol. 53, January, 1977

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