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Malaria Eradication in Chile
31
Parasitology Today, vol. 5, no. 2, 1989
Malaria Eradication in Chile M, UIIoa Malaria was eliminated from Chile by 194 I, by a campaign that used neither DDT nor other insecticides - nor mode.rn antimalarial drugs. This success illustrates the importance of 'classical methods' of environmental management against vector-borne parasites measures that are now being re-endorsed by international agencies such as the WHO. But, as Mauricio UIIoa discusses here, past success can imply future risk due to the lack of continued surveillance and the scarcity of personnel adequately trained to respond to any resurgence.
Until 1941 malariawas endemic in Chile. It was confined to the valleys and oases of the Tarapaca Province 13etween latitudes 18° and 21° south, covering an area of 55 000 km 2 (M. Massa, Thesis, University of Chile, Santiago, 1929). Each year up to that time, more than 50% of the population from this zone was affected by malaria although the disease - due to Plasmodium vivax- was mild and mortality practically nil I. The Chilean antimalaria campaign lasted 10 years. It was carried out in successive stages beginning at the northernmost city of Arica, then continuing to the nearby valleys of Azapa and, by 194 I, extended to the remaining valleys of Tarapac~ 2. The campaign was a complete success even before the application of DDT which served only to consolidate the gains that had been made 3. It consisted of two main periods: the first stage (1937-1944) was based on treatment of malaria patients and prophylactic measures using quinine, together with antilarval procedures against Anopheles pseudopunctipennis - the only species of Anopheles present in the endemic zone 4. The antilarval methods entailed applications of petroleum and sanitation works such as drainage of marshy lands, filling of stagnant pools and small marshes, repair of irrigation canals and control of springs. A novel treatment of the water surface, designed to suffocate anopheline larvae, was the use of a thick layer of shrub branches. Biological control was also widely applied by distributing the larvivorous fish, Gambusia amnis, in all collections of water. At the second stage of the campaign (I 944-1947), with the introduction of DDT, control procedures were modified and primary importance was given to house spraying against adult mosquitoes. The director of the campaign, the late ProfessorJuan Noe, sought to eradicate the Anopheles by house spraying and also by using DDT against larvae. The total amount of DDT consumed was I 002 750 g with a mean of 900 g per house at 2 g/m 7 of wall surface.5 By 194 I, interruption of transmission was evident and in 1946 Chile was officially declared free of malaria by the ~) 1989,ElsevierSciencePublishersLtd,(UK)016.%6147/891502.00
World Health Organization - the first endemic country to achieve this goal in modern times s. With the eradication of malaria and control of Anopheles, Chile could incorporate an extra 12 000 hectares into its agricultural base, and opened the port of Arica to industrial development 6. Yet Chile remains at risk from malaria because the vector is still present in many valleys of the former endemic zone, while there is an increasing risk of imported malaria from neighbouring countries - especially Peru and Bolivia7. Many travellers - tourists, truck drivers, religious parties - can import the parasite, and any geographical changes could stimulate an increase in vector breeding sites. If malaria returns to the country it will be a disaster for public health and very difficult to re-eradicate. Over the years since eradication, the population of the endemic zone has become a highly susceptible non-immune group 8. Moreover, very few surveillance measures are still carried out - and these mainly on a casual basis. Although medical science is very strong in Chile, the country no
longer has the real entomological research capacity - nor fully trained, experienced entomologists - able to respond adequately to any resurgence of malaria transmission. Of course, we must hope that such resurgence will never happen, but it would be of great significance (and reassurance) if studies could be supported on the current status of anopheline vectors in Chile - especially their present distribution, biological characteristics and susceptibility to insecticides. The experience in Chile perhaps illustrates what can be achieved by 'classical methods' of malaria control, but experience in other countries shows we would be unwise to neglect this problem nOW. References I Paez, R. (1930) Rev. Inst. Bact. I, 41-48 2 Noe, J. y Col. (1949) Rev. Parasitol. 4, 5-24 3 Noe, J. y Col. (I 949) Rev. Clin. Hig. Med. Rev. 2, 9-15 4 Neghame, A. y Col. (I 955) Am. ]. Trap. Med. Hyg. 4, II 14-1118 5 World Health Organization ( 1951 ) Bull. WHO 3,557Jo 19 6 Enciclopedia de Arica (Ist edn) (1972) Edit. Universidad, Biblioteca Central, Universitaria de Tarapaca, Sede, Arica 7 World Health Organization (1986) 22nd Pan American Sanitary Conference Washington DC 8 Reyes, H. (1985) Informe Chile 369,372
Mauricio UIIoa is a veterinarian at the University of Chile, Santiago, currently undertaking postgraduate studies at the London School of Hygiene and Tropical Medicine, Keppel Street, London WC I E 7HT, UK.
Towards Standardized Names for Parasitic Diseases The World Association for the Advancement of Veterinary Parasitology (WAAVP) has recently published ~ proposals for a standardized nomenclature of animal parasitic diseases (SNOAPAD). The object is to avoid the confusion which can arise, particularly in searching computerized databases (see Parasitology Today, Vol. 4, pp 324-328), from the variable use of the suffixes -iasis, -asis and -osis in terms such as trypanosomiasis, hydatidosis, taeniasis, and the rest. The SNOAPAD expert committee considered the proposal, made many years ago by Whittock ~, that
the suffix -osis be used for parasitic diseases with obvious clinical manifestations, and -iasis for subclinical infections; they rejected this proposal on the grounds that there is no clear-cut distinction between the two types of infection -indeed, the same infection can sometimes be an -iasis, and at others an -osis. The committee therefore concluded, simply, that only the suffix -osis (plural -oses) should be used, and that this suffix should be attached to the stem of the name of the parasite taxon, which is usually formed from the nominative by omitting the last one or two letters:
Parasitology Today, vol. 5, no. 2, 1989
Malaria Eradication in Chile M, UIIoa Malaria was eliminated from Chile by 194 I, by a campaign that used neither DDT nor other insecticides - nor mode.rn antimalarial drugs. This success illustrates the importance of 'classical methods' of environmental management against vector-borne parasites measures that are now being re-endorsed by international agencies such as the WHO. But, as Mauricio UIIoa discusses here, past success can imply future risk due to the lack of continued surveillance and the scarcity of personnel adequately trained to respond to any resurgence.
Until 1941 malariawas endemic in Chile. It was confined to the valleys and oases of the Tarapaca Province 13etween latitudes 18° and 21° south, covering an area of 55 000 km 2 (M. Massa, Thesis, University of Chile, Santiago, 1929). Each year up to that time, more than 50% of the population from this zone was affected by malaria although the disease - due to Plasmodium vivax- was mild and mortality practically nil I. The Chilean antimalaria campaign lasted 10 years. It was carried out in successive stages beginning at the northernmost city of Arica, then continuing to the nearby valleys of Azapa and, by 194 I, extended to the remaining valleys of Tarapac~ 2. The campaign was a complete success even before the application of DDT which served only to consolidate the gains that had been made 3. It consisted of two main periods: the first stage (1937-1944) was based on treatment of malaria patients and prophylactic measures using quinine, together with antilarval procedures against Anopheles pseudopunctipennis - the only species of Anopheles present in the endemic zone 4. The antilarval methods entailed applications of petroleum and sanitation works such as drainage of marshy lands, filling of stagnant pools and small marshes, repair of irrigation canals and control of springs. A novel treatment of the water surface, designed to suffocate anopheline larvae, was the use of a thick layer of shrub branches. Biological control was also widely applied by distributing the larvivorous fish, Gambusia amnis, in all collections of water. At the second stage of the campaign (I 944-1947), with the introduction of DDT, control procedures were modified and primary importance was given to house spraying against adult mosquitoes. The director of the campaign, the late ProfessorJuan Noe, sought to eradicate the Anopheles by house spraying and also by using DDT against larvae. The total amount of DDT consumed was I 002 750 g with a mean of 900 g per house at 2 g/m 7 of wall surface.5 By 194 I, interruption of transmission was evident and in 1946 Chile was officially declared free of malaria by the ~) 1989,ElsevierSciencePublishersLtd,(UK)016.%6147/891502.00
World Health Organization - the first endemic country to achieve this goal in modern times s. With the eradication of malaria and control of Anopheles, Chile could incorporate an extra 12 000 hectares into its agricultural base, and opened the port of Arica to industrial development 6. Yet Chile remains at risk from malaria because the vector is still present in many valleys of the former endemic zone, while there is an increasing risk of imported malaria from neighbouring countries - especially Peru and Bolivia7. Many travellers - tourists, truck drivers, religious parties - can import the parasite, and any geographical changes could stimulate an increase in vector breeding sites. If malaria returns to the country it will be a disaster for public health and very difficult to re-eradicate. Over the years since eradication, the population of the endemic zone has become a highly susceptible non-immune group 8. Moreover, very few surveillance measures are still carried out - and these mainly on a casual basis. Although medical science is very strong in Chile, the country no
longer has the real entomological research capacity - nor fully trained, experienced entomologists - able to respond adequately to any resurgence of malaria transmission. Of course, we must hope that such resurgence will never happen, but it would be of great significance (and reassurance) if studies could be supported on the current status of anopheline vectors in Chile - especially their present distribution, biological characteristics and susceptibility to insecticides. The experience in Chile perhaps illustrates what can be achieved by 'classical methods' of malaria control, but experience in other countries shows we would be unwise to neglect this problem nOW. References I Paez, R. (1930) Rev. Inst. Bact. I, 41-48 2 Noe, J. y Col. (1949) Rev. Parasitol. 4, 5-24 3 Noe, J. y Col. (I 949) Rev. Clin. Hig. Med. Rev. 2, 9-15 4 Neghame, A. y Col. (I 955) Am. ]. Trap. Med. Hyg. 4, II 14-1118 5 World Health Organization ( 1951 ) Bull. WHO 3,557Jo 19 6 Enciclopedia de Arica (Ist edn) (1972) Edit. Universidad, Biblioteca Central, Universitaria de Tarapaca, Sede, Arica 7 World Health Organization (1986) 22nd Pan American Sanitary Conference Washington DC 8 Reyes, H. (1985) Informe Chile 369,372
Mauricio UIIoa is a veterinarian at the University of Chile, Santiago, currently undertaking postgraduate studies at the London School of Hygiene and Tropical Medicine, Keppel Street, London WC I E 7HT, UK.
Towards Standardized Names for Parasitic Diseases The World Association for the Advancement of Veterinary Parasitology (WAAVP) has recently published ~ proposals for a standardized nomenclature of animal parasitic diseases (SNOAPAD). The object is to avoid the confusion which can arise, particularly in searching computerized databases (see Parasitology Today, Vol. 4, pp 324-328), from the variable use of the suffixes -iasis, -asis and -osis in terms such as trypanosomiasis, hydatidosis, taeniasis, and the rest. The SNOAPAD expert committee considered the proposal, made many years ago by Whittock ~, that
the suffix -osis be used for parasitic diseases with obvious clinical manifestations, and -iasis for subclinical infections; they rejected this proposal on the grounds that there is no clear-cut distinction between the two types of infection -indeed, the same infection can sometimes be an -iasis, and at others an -osis. The committee therefore concluded, simply, that only the suffix -osis (plural -oses) should be used, and that this suffix should be attached to the stem of the name of the parasite taxon, which is usually formed from the nominative by omitting the last one or two letters: