- Email: [email protected]
ECONOMIC ASPECTS OF REDUCED SMOKING
1077 C. Pison, Nuclear Medicine Service, Hotel-Dieu
Hospital
for technical
help. Hotel-Dieu Hospital, Section of Endocrinology, Metabolism, and Nutrition
and INRS-Santé, L H. Lafontaine Hospital, Montreal, Canada
A. GATTEREAU P. BIELMANN J. DURIVAGE P. LAROCHELLE
University Eye Hospital,
ECONOMIC ASPECTS OF REDUCED SMOKING
90220 Oulu 22, Finland
SIR,-Professor Atkinson and Mrs Townsend refer to my review of the McGuiness and Cowling study in the section of their paper headed Restrictions on Advertising (Sept. 3, p. 492). They say "Moreover a different interpretation of their [McGuiness and Cowling] results by Johnston gives a longterm elasticity with respect to advertising of less than half the reported value. Taking Johnston’s figure, total abolition of television advertising and the reduction of expenditure on advertising in the press by three-quarters could reduce consumption
by 10%." It would be a serious mistake to regard my amendment of the McGuiness and Cowling results as a reliable base for such a forecast. My review contained several criticisms of the study, one of which was that a conceptual and mathematical error had been made in the definition of the long-run elasticity. To demonstrate the effect of this error alone, I showed that their own statistical work implied an elasticity of approximately half the reported figure. The amended figure is still vitiated by the other criticisms. Even with a well-founded statistical study, prediction of the effects of very large changes, such as those considered by Atkinson and Townsend, is subject to ever-
increasing error. Department of Econometrics, University of Manchester * Present address:
J. JOHNSTON
Department of Economics, Emory University, Atlanta, Geor-
gta30322, U.S.A.
TRANSMISSION OF TOXOPLASMOSIS BY TROPHOZOITES
SIR,-It is generally accepted that toxoplasmosis is transby transplacental infection, cysts, and oöcystS.1.2 The
mitted
trophozoites of Toxoplasma gondii are assumed to be unable to resist changes in osmotic pressure, and they are thought not to survive outside the body long enough to transmit the infectionHowever, this assumption has not been proved experimentally. We have studied the role of trophozoites in the transmission of toxoplasmosis by testing their survival and pathogenicity in liquid media. In acute Toxoplasma infections the trophozoites are widely distributed throughout the body and they are liberserous exudates, fseces, urine, saliva, sputum, nasal and conjunctival secretions, vaginal discharges, semen, and milk.4. The trophozoites remain infectious in secretions for several days, in milk for 6 days, in saliva for 5 days, in urine for 7 days, and in tears for 4 days.6 In these media the trophozoites are relatively resistant to changes in osmotic pressure but they will not withstand drying or freezing.3·g The trophozoites
ated in
easily
penetrate intact
mucous
membranes from infected
se-
cretions,9 the smallest infective dose in man being approximately ten parasites.10 These observations suggest that tropho1. Frenkel, J. K., Dubey, J. P. J. infect. Dis. 1972, 126, 664. 2. Hartley, W. J., Munday, B. L. Aust. vet. J. 1974, 50, 224. 3. Jacobs, L. J. Wildlife Dis. 1970, 6, 305. 4 French, J. G., Messinger, H. B., MacCarthy, J. Am. J. Epidem. 185. 5. Janitschke, K. Germ. Med. 1971, 1, 23. 6. Saari, M., Räisänen, S. Acta ophthal., Copenh. 1974, 52, 847. 7 Raisänen, S., Saari, M. Med. Biol. 1976, 54, 152. 8 Saari, M., Räisänen, S. Nordic Coun. arct. med. Res. Rep. 1976, 16, 9 Räisänen, S. Acta univ. tamp. A, 1977, 84, 1. 10 Brown, J., Jacobs, L. Ann. intern.Med. 1956, 44, 565.
1970, 91,
31.
zoites may transmit the disease during acute stages of toxoplasmosis. Transmission of toxoplasmosis by trophozoites may explain why persons in contact with animals possess Toxoplasma antibodies significantly in excess of the average level, transmission of the disease in cattle, and occurrence of the parasite in areas where felines are not present.
Institute of Biomedical Sciences,
University of Tampere
K. M. SAARI S. A. RÄISÄNEN
IS CHILOMASTIX HARMLESS?
SIR,-Chilomastix mesnili is
a cosmopolitan .1agellate proin warm than cool climates. It is generally regarded as a harmless commensal in man transmitted by the faecal-oral route in the cyst form, with trophozoites living in the caecum and ascending colon. I have seen three patients from abroad who have had diarrhoea with C. mesnili and no other significant microbial pathogen detected in the fseces. In at least one patient treatment with metronidazole was followed by rapid and lasting improvement. The first patient was a 5-year-old Libyan boy who underwent partial colectomy for Hirschsprung’s disease of the sigmoid colon. 12 days after closure of colostomy he had severe, offensive diarrhoea. The faeces contained many trophozoites of C. mesnili and a few cysts of Entamaeba coli and ova of Trichuris trichiura. No enteropathogenic bacteria or yeasts were cultured. In view of these findings and the severity of the symptoms he was treated with a 5-day course of metronidazole, and he rapidly improved. Subsequent foccal examination showed no parasites. The second patient was a 24-year-old nurse who had had diarrhoea whilst travelling overland from Australia through India, Afghanistan, Turkey, and Europe. She presented in England with recurrent diarrhoea, and faecal examination showed many cysts of C. mesnili and a few of Entamaeba coli. Routine bacterial cultures yielded no pathogens. A 2-week course of metronidazole was prescribed, but I do not know the outcome. The third patient was a 33-year-old Iranian woman who has lived in England for 17 years without travelling abroad except for a 7-month visit to Pakistan in 1976-77. A few months before travelling she complained of intermittent diarrhoea; faecal examination revealed no causative organisms. After her return she presented with further diarrhoea, and faecal examination showed numerous trophozoites of C. mesnili but no other parasites or bacterial pathogens. Her symptoms were moderately improved after a course of metronidazole; diarrhoea reduced from ten to four times a day, and parasites were not subsequently seen. She is being investigated for malabsorption. Estimates of infection with C. mesnili of less than 1 to more than 10% of populations have been made, varying with the communities and the age-groups studied.I.2 I know of no figures for the prevalence in Britain or in travellers; perhaps this is because the organism is considered non-pathogenic. Laboratories may mistake the trophozoite for that of Giardia lamblia, which is motile and of a similar size. The cyst is a little smaller than that of G. lamblia, more rounded, and it bears a swelling at one end; it has been described as pear or lemon shaped. Since G. lamblia is now the commonest reported intestinal parasite in Britain3 it is important that it be distinguished from C. mesnili. Most parasitology textbooks record that there is no evidence that C. mesnili is a pathogen. The 1966 edition of Manson’s Tropical Diseases discussed the difficulty in assessing its patho-
tozoon more
prevalent
1. Craig and Faust’s Clinical Parasitology; p 63. New York, 1970. 2. Smyth, J. D. Introduction to Animal Parasitology, p. 48. London, 1976. 3. Commun. Dis. Rep Quarterly edition, 77/1-13; p. 18. Communicable Disease Surveillance Centre, Public Health Laboratory Service, 1977.
Hospital
for technical
help. Hotel-Dieu Hospital, Section of Endocrinology, Metabolism, and Nutrition
and INRS-Santé, L H. Lafontaine Hospital, Montreal, Canada
A. GATTEREAU P. BIELMANN J. DURIVAGE P. LAROCHELLE
University Eye Hospital,
ECONOMIC ASPECTS OF REDUCED SMOKING
90220 Oulu 22, Finland
SIR,-Professor Atkinson and Mrs Townsend refer to my review of the McGuiness and Cowling study in the section of their paper headed Restrictions on Advertising (Sept. 3, p. 492). They say "Moreover a different interpretation of their [McGuiness and Cowling] results by Johnston gives a longterm elasticity with respect to advertising of less than half the reported value. Taking Johnston’s figure, total abolition of television advertising and the reduction of expenditure on advertising in the press by three-quarters could reduce consumption
by 10%." It would be a serious mistake to regard my amendment of the McGuiness and Cowling results as a reliable base for such a forecast. My review contained several criticisms of the study, one of which was that a conceptual and mathematical error had been made in the definition of the long-run elasticity. To demonstrate the effect of this error alone, I showed that their own statistical work implied an elasticity of approximately half the reported figure. The amended figure is still vitiated by the other criticisms. Even with a well-founded statistical study, prediction of the effects of very large changes, such as those considered by Atkinson and Townsend, is subject to ever-
increasing error. Department of Econometrics, University of Manchester * Present address:
J. JOHNSTON
Department of Economics, Emory University, Atlanta, Geor-
gta30322, U.S.A.
TRANSMISSION OF TOXOPLASMOSIS BY TROPHOZOITES
SIR,-It is generally accepted that toxoplasmosis is transby transplacental infection, cysts, and oöcystS.1.2 The
mitted
trophozoites of Toxoplasma gondii are assumed to be unable to resist changes in osmotic pressure, and they are thought not to survive outside the body long enough to transmit the infectionHowever, this assumption has not been proved experimentally. We have studied the role of trophozoites in the transmission of toxoplasmosis by testing their survival and pathogenicity in liquid media. In acute Toxoplasma infections the trophozoites are widely distributed throughout the body and they are liberserous exudates, fseces, urine, saliva, sputum, nasal and conjunctival secretions, vaginal discharges, semen, and milk.4. The trophozoites remain infectious in secretions for several days, in milk for 6 days, in saliva for 5 days, in urine for 7 days, and in tears for 4 days.6 In these media the trophozoites are relatively resistant to changes in osmotic pressure but they will not withstand drying or freezing.3·g The trophozoites
ated in
easily
penetrate intact
mucous
membranes from infected
se-
cretions,9 the smallest infective dose in man being approximately ten parasites.10 These observations suggest that tropho1. Frenkel, J. K., Dubey, J. P. J. infect. Dis. 1972, 126, 664. 2. Hartley, W. J., Munday, B. L. Aust. vet. J. 1974, 50, 224. 3. Jacobs, L. J. Wildlife Dis. 1970, 6, 305. 4 French, J. G., Messinger, H. B., MacCarthy, J. Am. J. Epidem. 185. 5. Janitschke, K. Germ. Med. 1971, 1, 23. 6. Saari, M., Räisänen, S. Acta ophthal., Copenh. 1974, 52, 847. 7 Raisänen, S., Saari, M. Med. Biol. 1976, 54, 152. 8 Saari, M., Räisänen, S. Nordic Coun. arct. med. Res. Rep. 1976, 16, 9 Räisänen, S. Acta univ. tamp. A, 1977, 84, 1. 10 Brown, J., Jacobs, L. Ann. intern.Med. 1956, 44, 565.
1970, 91,
31.
zoites may transmit the disease during acute stages of toxoplasmosis. Transmission of toxoplasmosis by trophozoites may explain why persons in contact with animals possess Toxoplasma antibodies significantly in excess of the average level, transmission of the disease in cattle, and occurrence of the parasite in areas where felines are not present.
Institute of Biomedical Sciences,
University of Tampere
K. M. SAARI S. A. RÄISÄNEN
IS CHILOMASTIX HARMLESS?
SIR,-Chilomastix mesnili is
a cosmopolitan .1agellate proin warm than cool climates. It is generally regarded as a harmless commensal in man transmitted by the faecal-oral route in the cyst form, with trophozoites living in the caecum and ascending colon. I have seen three patients from abroad who have had diarrhoea with C. mesnili and no other significant microbial pathogen detected in the fseces. In at least one patient treatment with metronidazole was followed by rapid and lasting improvement. The first patient was a 5-year-old Libyan boy who underwent partial colectomy for Hirschsprung’s disease of the sigmoid colon. 12 days after closure of colostomy he had severe, offensive diarrhoea. The faeces contained many trophozoites of C. mesnili and a few cysts of Entamaeba coli and ova of Trichuris trichiura. No enteropathogenic bacteria or yeasts were cultured. In view of these findings and the severity of the symptoms he was treated with a 5-day course of metronidazole, and he rapidly improved. Subsequent foccal examination showed no parasites. The second patient was a 24-year-old nurse who had had diarrhoea whilst travelling overland from Australia through India, Afghanistan, Turkey, and Europe. She presented in England with recurrent diarrhoea, and faecal examination showed many cysts of C. mesnili and a few of Entamaeba coli. Routine bacterial cultures yielded no pathogens. A 2-week course of metronidazole was prescribed, but I do not know the outcome. The third patient was a 33-year-old Iranian woman who has lived in England for 17 years without travelling abroad except for a 7-month visit to Pakistan in 1976-77. A few months before travelling she complained of intermittent diarrhoea; faecal examination revealed no causative organisms. After her return she presented with further diarrhoea, and faecal examination showed numerous trophozoites of C. mesnili but no other parasites or bacterial pathogens. Her symptoms were moderately improved after a course of metronidazole; diarrhoea reduced from ten to four times a day, and parasites were not subsequently seen. She is being investigated for malabsorption. Estimates of infection with C. mesnili of less than 1 to more than 10% of populations have been made, varying with the communities and the age-groups studied.I.2 I know of no figures for the prevalence in Britain or in travellers; perhaps this is because the organism is considered non-pathogenic. Laboratories may mistake the trophozoite for that of Giardia lamblia, which is motile and of a similar size. The cyst is a little smaller than that of G. lamblia, more rounded, and it bears a swelling at one end; it has been described as pear or lemon shaped. Since G. lamblia is now the commonest reported intestinal parasite in Britain3 it is important that it be distinguished from C. mesnili. Most parasitology textbooks record that there is no evidence that C. mesnili is a pathogen. The 1966 edition of Manson’s Tropical Diseases discussed the difficulty in assessing its patho-
tozoon more
prevalent
1. Craig and Faust’s Clinical Parasitology; p 63. New York, 1970. 2. Smyth, J. D. Introduction to Animal Parasitology, p. 48. London, 1976. 3. Commun. Dis. Rep Quarterly edition, 77/1-13; p. 18. Communicable Disease Surveillance Centre, Public Health Laboratory Service, 1977.