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Onchocerciasis in Venezuela
418
CORRESPONDENCE
TABLE II. Dioecious helminths. Apparent and real incidence values of H from 0" 1% to 9 ' 9 % .
/-/%
0"0
0"1
0"2
0"3
0"4
0.5
0.6
0.7
0"8
19"0 26 "3 31 "6 36"0 39.7 43-0 45.9 48"6 51 "0
6"2 19"9 26"9 32" 1 36 "4 40"0 43-3 46"2 48 "8 51 "2
8"7 20"7 27 "5 32 "6 36 "8 40"4 43- 6 46 "5 49"0 51 "5
10.7 21 "5 28"0 33"0 37 "2 40-7 43- 9 46.7 49 "3 51.7
12 "3 22 "3 28-6 33"5 37 "6 41 "1 44"2 47-0 49" 6 51 "9
13"6 23.0 29" 1 33-9 37-9 41.4 44"5 47"3 49 "8 52.1
14-9 23.6 29.6 34.3 38 "3 41.7 44-8 47.5 50-1 52.4
16.0 24.4 30.2 34.8 38.8 42.0 45.1 47.8 50.3 52.6
17.1 25.0 30 "7 35.2 39"0 42"4 45 "4 48-1 50 "5 52-8
0"9 18.1 25.7 31-2 35-6 39-4 42.7 45.6 48 "3 50-8 53"0
I am, etc., g . ELSDON-DEw. Director Amoebiasis Research U n i t t Institute for Parasitology, Durban. 17 March, 1966. t The Amoebiasis Research Unit is sponsored by the following bodies: The South African Council for Scientific and Industrial Research T h ~ Natal Provincial Administration The University of Natal The United States Public Health Service (Grant AI 01592).
ONCHOCERCIASISIN VENEZUELA SIR,--While reporting on a case of ocular onchocerciasis found in a patient from Colombia, ASSlS-MASRI and LITTLE (1965) state that the illness has a "limited focus in eastern Venezuela". This was a valid concept up to 1954 when ARENBS et al. (1954) reported finding 2 cases in central Venezuela. Subsequently, extensive investigations have shown the prevalence of onchocerciasis in a wide z o n e surrounding the Lake of Valencia (GARcIA OCAMI'O et al., 1957; PEI~IALVERet al., 1963; RIVAS et al., 1964). Therefore, today it should be considered that onchocerciasis is prevalent throughout the whole northern part of Venezuela. I am, etc., T. ARENDS Department of Experimental Hematology, Instituto Venezolano de Investigaciones Cientificas, Caracas, Venezuela. 25 March 1966. REFERENCES ARENDS, T , RONDON, M. F. & GONZALEZMIJARES, P. (1954). Gac. reed. Caracas, 62, 646. ASSIS-MAsRI, G. & LITTLE, M. D. (1965). Trans. R. Soc. trop. Med. Hyg., 59, 717.
CORRESPONDENCE
419
GARClA OCAMPO, N., PADRON LIZARDO, O. & MAEKELT, G. A. (1957). Revta Soc. venez. Salud Pub,, 3, 323. PEI~ALVER, L. M., CONVIT, J., SISIRUCA, C., MAEKELT, G. A., RIVAS, A., BEAUJON, S., RASI, E. & MORA, J. A. (1963). Proe. VII Congr. int. trop. Med. Malaria, Brasil, 27~ 150. RIVAS, A., RASI, E., LSOGON, L. & GONZALEZ,L. (1964). Revta venez. Sanid. Asist. soc, 29, 75. CORRESPONDENCE MECHANICAL TRANSMISSION OF L E I S H M A N I A
SIR,--Dr. D. A. Berberian (Transactions, 1966, 60, pp. 277-278) referred to the use of sugar for inducing Phlebotomus argemipes to transmit Leishmania cyclically in the laboratory, and suggested that sugar was a laboratory artifice rather than a normal natural food of phlebotomine sand-flies, and that these insects might not be the commonest means of propagation. He urged that investigators should make further studies on mechanical transmission by biting flies. Sugar is an integral part of the normal diet of female Tabanidae (OLDROYD, 1954), and nectar is an important source of energy for many mosquitoes of both sexes (CLEMENTS, 1963). I have made observations, to be published, which suggest that sugar is a normal food of sand-flies and Simuliidae, at least in some areas, even when no source is obvious. I do not wish to weaken Dr. Berberian's appeal, however, but to support it by pointing out that from time to time kala-azar is reported from areas where no known sand-fly vector has been found. GARNI-IAM(1965) has reviewed some possible causes of such cases, and it may be that mechanical transmission by flies is sometimes responsible. I am, etc., D. J. LEWIS, External Staff, Medical Research Council, c/o British Museum (Natural History). 27 April 1966. REFERENCES
CLEMENTS, A. N. (1963). The Physiology of Mosquitoes. Oxford: Pergamon. Gm~NHAM, P. C. C. (1965). Amer. Zoologist, 5, 141. OLDROYD, H. (1954). The Horse-flies of the Ethiopian Region. II. London: British M u s e u m (Natural History).
THE POSSIBLE INVOLVEMENT OF AN INTERFERING SUBSTANCE IN THE ACTION OF THIOSEMICARBAZONES AGAINST VIRUSES
SIR,--It has been shown recently that in the prophylaxis of variola major among contacts in Madras a single absorbed dose of a thiosemicarbazone (M&B 7714) gave results almost identical with those of absorbed doses repeated daily for 3 days (RAo et al., in press). A possible explanation of this surprising result is that an interfering substance is produced from the interaction of drug and variola virus, the evidence for which follows I n prophylactic trials in man 2 thiosemicarbazones (BAUER et al., 1963; RAO et al.,~ 1965) have been shown to be active against the variola virus, but their mode of action has not been established. BAtmR (1955) showed that in mice infected with neurovaccinia, after treatment with isatin p-thiosemicarbazone (IBT), the viral titre in the brain was reduced but the virus that could be recovered was still virulent. T h e maximum effect was obtained with a small concentration of the compound, increased dosing giving no better effect. Our studies with the thiosemicarbazone of 4-bromo-3-methylisothiazole5-carboxaldehyde (M&B 7714) (SLACK et al., 1964) showed the same effect, namely that administration afforded protection to infected animals but fully infectious virus could be recovered from the brains of treated animals. SHEFFIELD, BAUER and STEVHENSON (19603 showed that I B T prevented the appearance of cytopathogenic effects in cell cultures ( E R K cells), but the infectivity of the virus was not destroyed. T h e adsorption of the virus was likewise not prevented.
CORRESPONDENCE
TABLE II. Dioecious helminths. Apparent and real incidence values of H from 0" 1% to 9 ' 9 % .
/-/%
0"0
0"1
0"2
0"3
0"4
0.5
0.6
0.7
0"8
19"0 26 "3 31 "6 36"0 39.7 43-0 45.9 48"6 51 "0
6"2 19"9 26"9 32" 1 36 "4 40"0 43-3 46"2 48 "8 51 "2
8"7 20"7 27 "5 32 "6 36 "8 40"4 43- 6 46 "5 49"0 51 "5
10.7 21 "5 28"0 33"0 37 "2 40-7 43- 9 46.7 49 "3 51.7
12 "3 22 "3 28-6 33"5 37 "6 41 "1 44"2 47-0 49" 6 51 "9
13"6 23.0 29" 1 33-9 37-9 41.4 44"5 47"3 49 "8 52.1
14-9 23.6 29.6 34.3 38 "3 41.7 44-8 47.5 50-1 52.4
16.0 24.4 30.2 34.8 38.8 42.0 45.1 47.8 50.3 52.6
17.1 25.0 30 "7 35.2 39"0 42"4 45 "4 48-1 50 "5 52-8
0"9 18.1 25.7 31-2 35-6 39-4 42.7 45.6 48 "3 50-8 53"0
I am, etc., g . ELSDON-DEw. Director Amoebiasis Research U n i t t Institute for Parasitology, Durban. 17 March, 1966. t The Amoebiasis Research Unit is sponsored by the following bodies: The South African Council for Scientific and Industrial Research T h ~ Natal Provincial Administration The University of Natal The United States Public Health Service (Grant AI 01592).
ONCHOCERCIASISIN VENEZUELA SIR,--While reporting on a case of ocular onchocerciasis found in a patient from Colombia, ASSlS-MASRI and LITTLE (1965) state that the illness has a "limited focus in eastern Venezuela". This was a valid concept up to 1954 when ARENBS et al. (1954) reported finding 2 cases in central Venezuela. Subsequently, extensive investigations have shown the prevalence of onchocerciasis in a wide z o n e surrounding the Lake of Valencia (GARcIA OCAMI'O et al., 1957; PEI~IALVERet al., 1963; RIVAS et al., 1964). Therefore, today it should be considered that onchocerciasis is prevalent throughout the whole northern part of Venezuela. I am, etc., T. ARENDS Department of Experimental Hematology, Instituto Venezolano de Investigaciones Cientificas, Caracas, Venezuela. 25 March 1966. REFERENCES ARENDS, T , RONDON, M. F. & GONZALEZMIJARES, P. (1954). Gac. reed. Caracas, 62, 646. ASSIS-MAsRI, G. & LITTLE, M. D. (1965). Trans. R. Soc. trop. Med. Hyg., 59, 717.
CORRESPONDENCE
419
GARClA OCAMPO, N., PADRON LIZARDO, O. & MAEKELT, G. A. (1957). Revta Soc. venez. Salud Pub,, 3, 323. PEI~ALVER, L. M., CONVIT, J., SISIRUCA, C., MAEKELT, G. A., RIVAS, A., BEAUJON, S., RASI, E. & MORA, J. A. (1963). Proe. VII Congr. int. trop. Med. Malaria, Brasil, 27~ 150. RIVAS, A., RASI, E., LSOGON, L. & GONZALEZ,L. (1964). Revta venez. Sanid. Asist. soc, 29, 75. CORRESPONDENCE MECHANICAL TRANSMISSION OF L E I S H M A N I A
SIR,--Dr. D. A. Berberian (Transactions, 1966, 60, pp. 277-278) referred to the use of sugar for inducing Phlebotomus argemipes to transmit Leishmania cyclically in the laboratory, and suggested that sugar was a laboratory artifice rather than a normal natural food of phlebotomine sand-flies, and that these insects might not be the commonest means of propagation. He urged that investigators should make further studies on mechanical transmission by biting flies. Sugar is an integral part of the normal diet of female Tabanidae (OLDROYD, 1954), and nectar is an important source of energy for many mosquitoes of both sexes (CLEMENTS, 1963). I have made observations, to be published, which suggest that sugar is a normal food of sand-flies and Simuliidae, at least in some areas, even when no source is obvious. I do not wish to weaken Dr. Berberian's appeal, however, but to support it by pointing out that from time to time kala-azar is reported from areas where no known sand-fly vector has been found. GARNI-IAM(1965) has reviewed some possible causes of such cases, and it may be that mechanical transmission by flies is sometimes responsible. I am, etc., D. J. LEWIS, External Staff, Medical Research Council, c/o British Museum (Natural History). 27 April 1966. REFERENCES
CLEMENTS, A. N. (1963). The Physiology of Mosquitoes. Oxford: Pergamon. Gm~NHAM, P. C. C. (1965). Amer. Zoologist, 5, 141. OLDROYD, H. (1954). The Horse-flies of the Ethiopian Region. II. London: British M u s e u m (Natural History).
THE POSSIBLE INVOLVEMENT OF AN INTERFERING SUBSTANCE IN THE ACTION OF THIOSEMICARBAZONES AGAINST VIRUSES
SIR,--It has been shown recently that in the prophylaxis of variola major among contacts in Madras a single absorbed dose of a thiosemicarbazone (M&B 7714) gave results almost identical with those of absorbed doses repeated daily for 3 days (RAo et al., in press). A possible explanation of this surprising result is that an interfering substance is produced from the interaction of drug and variola virus, the evidence for which follows I n prophylactic trials in man 2 thiosemicarbazones (BAUER et al., 1963; RAO et al.,~ 1965) have been shown to be active against the variola virus, but their mode of action has not been established. BAtmR (1955) showed that in mice infected with neurovaccinia, after treatment with isatin p-thiosemicarbazone (IBT), the viral titre in the brain was reduced but the virus that could be recovered was still virulent. T h e maximum effect was obtained with a small concentration of the compound, increased dosing giving no better effect. Our studies with the thiosemicarbazone of 4-bromo-3-methylisothiazole5-carboxaldehyde (M&B 7714) (SLACK et al., 1964) showed the same effect, namely that administration afforded protection to infected animals but fully infectious virus could be recovered from the brains of treated animals. SHEFFIELD, BAUER and STEVHENSON (19603 showed that I B T prevented the appearance of cytopathogenic effects in cell cultures ( E R K cells), but the infectivity of the virus was not destroyed. T h e adsorption of the virus was likewise not prevented.