Bull Pan Am Hedfk Orgnn 15(4), 1981.

CHAGAS’ DISEASE SEROEPIDEMIOLOGY IN THE AREA OF THE FUTURE YACYRETA-APIPE HYDROELECTRIC DAM IN CORRIENTES PROVINCE, ARGENTINA1

C. Edgardo Bordaz and M. Josefa F. Rea3

A survey conducted near a dam-site on the Paraguay-Argentine border showed the area to be highly endemic for Chagas’ disease. It also showed that new housing unsuited to the disease vector’s prol$eration did not eliminate the prob- /em, indicating a strong needfor health education capable of guiding people away from traditional behavior patterm tending to encourage the vector and cause infection.

Introduction communities on the right bank of the Parani River, in Paraguayan territory, and could well In 1977, Borda et al. (I) reported the pres- be present on the opposite bank, in Argentine ence of Triatoma infestam, one of the vectors of territory-were felt to provide ample justifica- Chagas’ disease, in houses located at Ayolas, tion for serologic surveys of representative Santiago, and Yacyrets Island in Paraguay. areas on the Argentine side in order to deter- These communities are situated along the mine the extent and distribution of possible Paraguay-Argentine border, within the area infection. of influence of the future YacyretL-ApipC In October, November, and December of hydroelectric dam, which is to be built by 1978, under the sponsorship of the Ministry of Argentina and Paraguay on the lower part of Public Health of Argentina, the Yacyrets the Parand River. It is logical to assume that Binational Agency, and the National Scien- this project will involve major environmental tific and Technical Research Council, surveys changes, as well as construction of housing for were conducted in a portion of Argentina’s relocation of area residents. These events Corrientes Province. Their aim was to find could create microclimates propitious for col- the index of Triatoma infestation in local onization by local or imported Chagas’ homes; the proportion of the insects infected disease vectors. Similarly, human migrations, with the disease agent, Typanosoma cmzi; and with the consequent arrival of infected people, the prevalence of human infection with T. could contribute to the creation of new domi- cruzi as determined by serologic examination. ciliary disease foci. These considerations-together with the fact that T. infestanshad been detected in Materials and Methods

l Also published in Spanish in the B&fin de la Oficina The Setting Sanifaria Panamericana90(4), 1981. PDirector, National Parasitology Center, and Asso- The site of the Yacyret&ApipC Dam is at ciate Professor of Parasitology, School of Medicine, Na- tional University of the Northeast, Santa Fe 1432, 3400 the borders of southern Paraguay and north- Corrientes, Argentina. eastern Argentina, between 27 and 28 degrees 3Chief, Department of Immunoparasitolo.~, National south latitude. The location of this area is Parasitology Center, and Advancdd Scientific Research Fellow of the National Scientific and Technical Research shown in Figure 1. The zone in question has Council, Buenos Aires, Argentina. experienced only limited development and has

333 334 PAHO BULLETIN l vol. 15, no. 4, 1981

Figure 1. A map showing the location of Corrientes Province, Argentina, and the areas surveyed.

a stable population of nearly 15,000 inhabit- facilities were set up at quarters provided by ants living on both sides of the Parana River. the Yacyreta Binational Agency in Ituzaingo The climate is humid and subtropical, with no and at the San Antonio Health Center on dry season; the average annual temperature, ApipC Grande Island. relative humidity, and rainfall are 21”C, 73 per cent, and 1,700 mm, respectively (2). Ituzaingo’ Project Quarter Within this general region, surveys were conducted at three selected places-all in the This is a residential district 230 km east of department of Ituzaing6 (Corrientes Pro- the city of Corrientes, to which it is linked by a vince). These were the Ituzaingo Project paved road. A total of 182 standard homes quarter, Apipe Grande Island, and ApipC (see photos) have been built there, and since Chico Island. The specific locations of the August 1978 these have been inhabited by populations studied are shown in Figure 1. some 661 people. These residents belong to Overall, 541 houses inhabited by 2,058 people families that had lived in primitive and unhy- were included in the survey. gienic dwellings with dirt walls and floors and Schematic maps were used that showed the thatched roofs situated on land now occupied distribution of homes in each selected area; by the new permanent townsite and the dam’s the homes to be surveyed were selected at ran- reservoir area. The old dwellings were de- dom, and their residents were listed on a form stroyed, and the inhabitants and their belong- by name, age, and sex. Field laboratory ings were relocated to the new houses. During Borda and Rea l CHAGAS’ DISEASE IN CORRIENTES, ARGENTINA 335 the survey 18 per cent of these new homes because of periodic flooding. It was necessary were inspected, and serologic examinations to cross the jungle on foot in order to conduct were performed on 10 per cent of the popula- the survey, as this was the only way of reach- tion. ing the houses. Proceeding in this fashion, 76 per cent of the houses were inspected and blood samples were taken from 81 per cent of A@ Grande Island their residents.

This island is in the Paran River to the north of several small uninhabited islands, the The Study Population island of ApipC Chico, and the town of Itu- All the people studied, including some from zaing6 (see Figure 1). It has an area of 266 Paraguay, were Caucasians. Overall, the km2, and according to a census taken by the study population’s socioeconomic level could Ministry of Social Welfare of Corrientes in be considered low. The economically active 1978, it then had a population of 1,263 people residents were unskilled or semiskilled living in 3 17 dwellings. The islanders were workers temporarily employed doing prelimi- living in four communities-San Antonio, nary work for the dam. This was particularly Panco Cut, Monte Grande, and General true of those living in Ituzaingo. Women in Uriburu-all of them situated along the these areas did household tasks. northern coast, which has the highest eleva- On the islands, most of the arable land was tion. These small villages are separated by dense jungle, lagoons, and densely reeded devoted to primitive subsistence farming; the estuaries. islanders also did some fishing. The household It takes 30 minutes by launch to reach the livestock, depending on each family’s eco- island from Ituzaingb. The crossing is made nomic situation, included cattle, pigs, difficult by the river’s rocky bed and the swift- chickens, dogs, and cats. Some families were ness of the current approaching ApipC Falls. self-employed making bricks, whose manufac- In our case it proved impossible to get from ture engaged all family members, including Panco Cue to General Uriburu by water the children. Those living close to the estuaries because the river’s volume was too small. Ac- exploited the reeds growing there for commer- cordingly, it was necessary to cross the island cial purposes. Primary and secondary school- in a horse-drawn cart, which took three hours ing was available in Ituzaing6, but only in each direction. It was only possible to primary education was provided on the inspect 11 per cent of the dwellings on this islands. island, as they were widely scattered. Most of The dwellings in Ituzaingb appeared com- the blood samples, obtained from 21 per cent fortable compared to those on the islands. The of the population, were procured from former, built of brick and cement, had walls assembled groups of residents. plastered with a limestone-sand mixture, tile or cement floors, and tile or galvanized zinc Apipi Chico Island roofs. Each had two bedrooms, a bath, a kit- chen, and an adjoining yard. (After moving ApipC Chico Island is on the Parana River in, the residents built huts and animal pens in between ApipC Grande Island and Ituzaingo. these yards out of wood, straw, and paper- It can be reached from Ituzaingo in 10 board salvaged from their old dwellings.) All minutes by motorized launch. This island has the homes had drinking water, electricity, and an area of 20.8 km*; at the time of the survey appropriate excreta disposal systems. it had a population of 134 living in 42 dwell- In contrast, the islanders’ homes were poor- ings. As in the ApipC Grande communities, ly ventilated and unsanitary. The walls were these dwellings were situated on high ground generally of wood or tacuam reed plastered 336 PAHO BULLETIN l vol. 15, no. 4, 1981 over with a mixture of dirt and sand that was tained from infected mice by cardiac punc- usually cracked. The roofs were of thatch or ture . paperboard and the floors of compacted dirt. The residents of these island homes lived in overcrowded conditions and in intimate prox- Serologic Examinations imity with their animals. The only buildings that constituted noteworthy exceptions on the Whenever possible, blood samples were islands were the San Antonio Health Center taken from all the household members sur- and a cluster of five buildings forming the veyed, regardless of whether triatomids were compound of the Hogar Filadelfia de Apipt present in their dwellings. The blood was ob- Grande, a religious institution operated by tained by venipuncture using needles and Swedish missionaries. vacuum suction tubes.( Immediately after ex- traction, the serum was separated; it was then Capture and Examination of Vectors stored at -20°C until used. Collected sera were transported from the field laboratories to In the course of the house visits, triatomid the National Parasitolom Center in isopor vectors of Chagas’ disease were shown to the storage boxes containing bags of refrigerant. inhabitants in order to assist them in locating like bugs. The residents were also asked Hemagglutination Tests whether they knew about the relationship be- tween the insects and the disease. A careful These were carried out in accord with the inspection was made of each house surveyed. semiquantitative technique described by Mar- The doors and windows were closed, pyre- tini (5), using U-platess. The sera were con- thrum was released inside, and about 20 sidered positive if they reacted at a dilution of minutes later triatomids were captured with 1: 16 or more. Sheep erythrocytes were the aid of lamps and tweezers. employed in the test. The antigen for these After due preparation, the bugs were sent to tests (and for the immunofluorescence tests) the National Parasitology Center for examina- was prepared from TulahuCn strain epimasti- tion and identification. There they were sub- gotes and was obtained from The Dr. Mario jected to laboratory procedures designed to Fatala ChabCn National Institute for Chagas’ determine their rate of infection with T. cruzi. Disease Diagnosis and Research in Buenos Fresh stools, obtained by pressing on the ab- Aires. domen, were suspended in a 0.85 per cent sodium chloride solution and viewed through ImmunofluorescenceTests a microscope. If this yielded negative results, the triatomids involved were dissected, and The indirect immunofluorescence tech- their gut contents were homogenized in saline nique recommended by Alvarez (6) was solution and examined. Evidence of infection employed. Sera reacting at a titer of 1:30 or with T. cruzi was corroborated by observation more were considered positive. The antigen of (a) flagellates with typical T. cruzi mor- (prepared with epimastigote forms of T. cruzi, phology and movement; (b) Giemsa-stained TulahuCn strain) was cultured in diphasic metacyclic forms of the parasite prepared ac- media (4,). The slides used contained 12 cording to the method of Mayer et al. (3); (c) circles, each 0.8 cm in diameter, that were fresh and stained trypomastigote forms ob- marked with acetone-diluted nail polish. tained from white mice infected by intraperi- toneal inoculation of a saline suspension of the bugs’ feces; and (d) epimastigote forms grown 4Venoject Jintan Terumo Co., Tokyo, Japan. in culture media (4,) inoculated with blood ob- 5Microtiter Kit, Cooke Engineering Co., U.S.A. Borda and Rea l CHAGAS’ DISEASE IN CORRIENTES, ARGENTINA 337

Human anti-gamma globulin labeled with ple represented about 10 per cent of the Itu- fluorescein isothiocyanate from the Pasteur zaingb Project Quarter population; anywhere Institute in Paris was used for this test. The from 8 per cent to 14 per cent of the age “optimum” titer (the greatest dilution of anti- groups shown, except the youngest (the O-4 gamma globulin that reacted with positive year age group), were examined. Analysis of control sera) was 1:80. Observations were the 63 blood specimens obtained disclosed the made with a Karl Zeiss Jena (Ergaval model) presence of T. cru& antibodies in 22 subjects microscope equipped with a 12.5 x eyepiece, a (35 per cent). These people, it should be em- dry 40/0.65 objective, and a 1.05 cardioid phasized, had previously lived in houses colo- dark-field condenser. Ultraviolet light was nized by triatomid bugs. supplied by an Osram HBO 200 lamp, The Although the examination of 21 per cent of filters used included an anticaloric GG 13-2, a the inhabitants of ApipC Grande Island (Table BG3/2G excitor, and a K 510 blocker. All the 2) may be considered representative, only 7 microscopic observation was performed in a per cent of the inhabitants under 5 years old darkroom. and 10 per cent of those over 49 were exam- ined. T, mm’ antibodies were detected in 46 per cent of the sera from Apip& Grande residents. As may be seen in Table 3, the sample examined on Apipt Chico was highly repre- The sera given these two tests were consid- sentative (81 per cent of the population), and ered either responsive (positive) or unrespon- at least 64 per cent of each age group listed sive. The antigen utilized in the immuno- was examined. Sera from 51 per cent of the fluorescence and hemagglutination tests came ApipC Chico residents yielded positive results. from the same batch. As on ApipC Grande, the Apipe Chico resi- dents were living in homes colonized by the Results disease vector. Overall, there was 99 per cent agreement Of the 410 persons over 5 years of age who between the hemagglutination and immuno- were asked about the presence of triatomids in fluorescence test results. That is, the results their homes, barely 1 per cent expressed lack differed with respect to only five of the 435 of familiarity with the insects. This figure in- sera examined. cluded people who had recently arrived in Itu- zaingi, from urban centers in the provinces of Santa Fe and Buenos Aires. Locally, the triatomids were known by their indigenous Infestation Indexes names-yuru pucu bug or guazu bug (from the Guarani yulu for “beak” or “mouth,” pucu for “long,” and guazu for “large”). In all, 99 of the 541 residences surveyed were inspected for triatomids. The triatomine species encountered was T. infestans (in all its stages of development). Of the 99 homes in- Serologic Tests spected in the three survey areas, 71 per cent were found to be infested. However, the in- The 435 persons serologically surveyed con- festation index was relatively low (12 per cent stituted 21 per cent of the three survey areas’ of the inspected homes) in the Ituzaingt, Proj- total population. Table 1 shows the distribu- ect area and extremely high (100 per cent of tion, by age and sex, of the 63 people surveyed the inspected homes) on ApipC Grande and in the Ituzaing6 Project area. This latter sam- ApipC Chico. Table 1. Ituzaing6 Project Quarter serologic results, showing the distribution by age and sex of the 63 people tested for antibodies to T. nun’ in October 1978 and the percentages yielding a positive response to both the hemagglutination and immunofluorescence tests.

Males Femates Total

$6 of whole Positive responses 5%of whole Positive responses % of whole Positive responses Age PUP NO. age .wUP NO. =g= BroUP NO. age group (in years) tested tested NO % tested tested NO. % tested tested NO. %

o-4 2 3 2 100 - 2 1 2 100 5-9 a 16 4 50 6 12 3 50 14 14 7 50 10-14 6 13 2 33 2 7 8 11 2 25 15-19 3 7 1 33 3 9 3 100 6 a 4 67 20-49 a 6 3 37 18 16 4 22 26 11 7 27 2 50 2 11 - - 5 13 7 12 Total 29 9 12 41 34 10 10 29 63 10 22 35

Table 2. ApipC Grande serologic results, showing the distribution by age and sex of the 268 people tested for antibodies to T. m-t& in December 1978 and the percentages yielding a positive response to both the hemagglutination and immunofluorescence tests.

Males Females Total

% of whole Positive responses % of whole Positive responses I of whole Positive responses Age W”P NO age group NO. =g= PmUP NO. %- W”P (in years) tested tested NO 74 tested tested NO % tested tested NO %

o-4 9 10 6 67 5 5 4 80 14 7 10 71 5-9 37 36 15 41 30 35 18 60 67 36 33 49 10-14 34 31 18 53 35 51 18 51 69 39 36 52 15-19 18 30 10 56 17 29 14 82 35 29 24 69 20-49 25 13 6 24 33 21 a 24 58 17 14 24 t 50 a 7 3 37 15 13 3 20 23 10 6 26

Total 131 20 58 44 135 23 65 48 266 21 123 46 Table 3. Apip Chico serologic results, showing the distribution by age and sex of the 106 people tested for antibodies to T. cm.zi in November 1978 and the percentages yielding a positive response to both the hemagglutination and immunofluorescence tests.

Males Females Total

% of whole Positive responses % of whole Positive responses % of whole Positive responses Age group NO. =g= group NO. age group NO. as= .wv (in years) tested tested NO % tested tested NO. % tested tested NO. %

o-4 4 71 2 50 5 100 2 40 9 a3 4 44 5-9 4 67 4 100 11 100 3 27 15 a8 7 47 10-14 12 100 7 58 9 100 5 56 21 100 12 57 15-19 a 100 3 37 1 100 1 100 9 100 4 44 20-49 17 64 10 59 19 91 9 47 36 76 19 53 2 50 6 50 1 17 10 77 7 70 16 64 a 50

Total 51 73 27 53 55 92 27 49 106 81 54 51 340 PAHO BULLETIN l vol. 15, no. 4, 1981

Infection of Triatomids with T. cruzi Paraguayan territory (Ayolas, Santiago, and YacyretL Island). It should be emphasized Of 255 triatomids captured, 74 (29 per that this is the first time T. infestans’ presence cent) were found to have trypanosomes in on Apipe Grande and ApipC Chico has been their feces. These trypanosomes’ morphology, reported. (These islands are evacuated when mobility, staining characteristics, infectivity periodic flooding of the Paran occurs.) This for mice, and growth in vitro places them finding shows that under natural conditions within the T. cruzi biological complex. The this triatomid species is easily capable of four triatomids found in Ituzaingo Project adapting to climatic variations including tem- Quarter homes arrived at the laboratory dead porary flooding and a high relative humidity and dry, which made it impossible to deter- that averages 73 per cent. mine whether they had been infected with T. AV&S (lo), referring to T. infestans in cruzi. Argentina, says that throughout its geographic Within the Ituzaingo Project Quarter, the range the bug is known by the Quechua In- positive sera were obtained from people who dian name vinchuca. This Quechua name had previously lived in bug-infested huts. makes one suspect that the bug’s center of Similarly, virtually all the islanders lived with dispersion has been Peru or Bolivia. This is the insect. Overall, the presence of T. cruzi the same name used in the country’s north- was confirmed in 29 per cent of the triatomids eastern and central provinces, where there collected on ApipC Chico and in 30 per cent of have been either Quechua populations or those from Apipe Grande. Quechua cultural and linguistic influence. However, this influence is not present in the Discussion Corrientes Province communities studied- because this part of Argentina (like Paraguay) The culture, socioeconomic conditions, and was originally inhabited by another Indian physical environment of the study areas ob- group that spoke the Guarani language. For viously tended to favor procreation and main- this reason, the people asked about the tenance of T. infestans. Although it is assumed presence of vinchucas in their homes did not that T. infestans’ range in Argentina extends know them by that name; but when shown the from 22’ to 45’ south latitude, and from the insect they recognized it, calling it chincheyuru Andes Mountains in the west to the eastern pucu or chincheguazu. 6 These native names, in ocean and riverine coastline (7, S), the bug’s which Spanish is mixed with Guarani, should density of infestation is not uniform. Epide- be added to the list of common names for T. miologic surveys made to determine infesta- infestans and should be incorporated into the tion levels have shown the most infested areas health education programs planned for this to be provinces situated in the central and area, so that local people can more easily northern parts of the country (9). understand messages referring to this insect. Confirmation of the existence of T. infstuns On the islands, the residents’ poverty had a in Ituzaingo Department, Corrientes Pro- lot to do with their homes’ makeshift nature- vince (as previously suggested--l), the high a factor greatly favoring Chagas’ disease (100 per cent) infestation indexes found on transmission. However, this housing pattern Apipt Grande and Apip Chico, and the high did not exist in the Ituzaingo Project area- rate of T. infestans infection with T. cruzi because the State financed the building of new justify including this region among those areas homes, and because the materials used did not considered highly endemic for Chagas’ dis- ease. This ties in with epidemiologic data pre- viously reported by Borda et al. (1) showing 6Chinche is a Spanish word for “bug” sometmes used an extensive endemic area that includes some to refer to triatomids. Bon& and Rea l CHAGAS’ DISEASE IN CORRIENTES, ARGENTINA 341

foster proliferation of the bugs. Therefore, ments; indeed, it would appear that such although things were not consciously planned cultural conditioning can only be overcome that way, the bug was discouraged when the through the education needed to establish a unhygienic huts providing ideal habitats were hygienic style of life. removed and replaced with comfortable dwell- T. cruzi antibodies were found in sera from ings. all the age groups involved except those over Nevertheless, lack of basic health education 50 years of age in the Ituzaingo Project area. and public ignorance about the bugs and their Nevertheless, it was not possible to draw con- connection with Chagas’ disease enabled the clusions about the serologic prevalence of T. triatomids to persist in the Ituzaingo Project cruzi antibodies in the different age groups at community (see Table 4). This situation was ApipC Grande and Ituzaingo because the partly attributable to passive transport of T. groups surveyed were not sufficiently homo- in@ans in furnishings and personal effects geneous. Generally speaking, however, the brought from the residents’ previous homes; more homogeneous and representative sam- and it was also partly attributable to the resi- ples of subjects (corresponding to those 5 to 19 dents’ construction of huts in their yards like years old) in each of the three study areas in- those shown in the accompanying pictures. dicated that the rate of positive serologic These huts, made of wood, tacuara reeds, and response tended to increase with age. This was paperboard sheets salvaged from the resi- especially evident in the population surveyed dents’ old homes, offered T. infestans an ade- on ApipC Grande, where the serologic quate refuge. responses taken as a whole became more These yard huts were used as shelters for positive with increasing age (see Table 3). domestic animals and were undoubtedly oc- This finding coincides with what has already cupied by wild mammals, such as rats and been pointed out by other authors (9, 14, 15). weasels, that serve as T. cruzi reservoirs. It Sensitivity and specificity evaluations made was also common to use these improvised by several researchers indicate that the indirect buildings as storage places for utensils, food, immunofluorescence and hemagglutination and logs. Sometimes they were also used as tests used in this study are very suitable for in- family meeting-places and even as places for dividual diagnoses and seroepidemiologic receiving guests. Clearly, these uses and studies of T. crU.zi infection (16-18). From the customs were neither immediately nor com- positive results of these tests and the triatomid pletely eliminated by mere housing improve- infestation densities observed, it can be in-

Table 4. Results of the December 1978 entomologic and parasitologic survey of dwellings in the three study areas of Ituzaing6 Department, Corrientes Province, Argentina.

T. in@znc examined for presence Dwellings of T. cmzzparas,tes

Inspections Dwellings with T. inzrbms Positwe for T. mzt Total no. Survey area of dwellings NO. % % of those Total no. in area mspected inspected NO. inspected examined NO. %

Ituzaingb 182 33 18 4 12 4 Project ApipC Grande 317 34 11 34 100 179 53 30 ApipC Chico 42 32 76 32 100 72 21 29 Total 541 99 18 70 71 255 74 29 342 PAHO BULLETIN . vol. 15, no. 4, 1981

Ituzaing6 Project housing, showing state-financed dwellings (above) and makeshift huts and animal pens subsequently built by residents (below).

d . . i

i

-I- 1.

I It F

-- * Borda and Rea l CHAGAS’ DISEASE IN CORRIENTES, ARGENTINA 343 ferred that T. cruzi infections are proceeding tributed to these differences, it would be worth actively in the three areas studied. However, exploring whether a statistically significant the vectors do not necessarily transmit infec- difference exists between the sexes with regard tions to all the people living in the same in- to rates of T. crui infection. Some authors fested dwelling. For example, sera from 26 have reported finding slightly higher rates of ApipC Chico residents living in a cluster of five infection in women, although a higher per- infested huts were examined for T. cruzi anti- centage of men exhibit ensuing cardiac bodies. Such antibodies were found in only damage (11). Other authors point to the fact nine (35 per cent) of these 26 residents. This that, for undetermined reasons, both cardiac observation supports Oliver’s point (19) that and digestive tract involvement are more the parasite has difficulty passing from its common among men (12)1 while still others triatomid vector to man. The nature of what note that the general prevalence of cardiac causes this observed lack of infection should problems is higher among men (13). be investigated, keeping in mind that sites like It should also be noted that the serologic those studied appear to offer virtually all the findings indicate infection rather than disease. conditions favoring transmission from the in- A more comprehensive study is needed to vertebrate host. detect the parasites by xenodiagnosis and to It also seems noteworthy that we were able determine whether the positive responders to capture a large number of triatomids, at all show evidence of changes in their hearts or stages of development, in bundles of straw other organs attributable to T. cruti. These stored in an islander’s farm. These bundles measures would permit the prevalence of were being sold to fellow islanders and also to Chagas’ disease morbidity among the infected Ituzaingo residents. This trade provided an people to be determined, and would provide easy route of T. infestuns transfer from one an improved statistical basis for assessing the place to another. public health hazard posed by Chagas’ disease The results of the serologic examinations morbidity in this part of Northeast Argentina. confirmed our working hypothesis that T. Likewise, other factors that help determine cruzi infection was highly prevalent in the the epidemiology of Chagas’ disease in rural department of Ituzaingo. Overall, 46 per cent areas should be evaluated, such as the impor- of the people tested gave a positive serologic tance of domestic and wild animal reservoirs. response, and study populations in areas with As this work shows, environmental changes relatively high vector infestation indexes taking place in the area to be served by the yielded relatively high rates of positive Yacyreti-ApipC Dam are being accompanied response. Analysis of the total positive by population movements intimately related responses by sex (45.97 per cent of 211 men to Chagas’ disease transmission. It is clear and 45.53 per cent of 224 women responded that when the new Ituzaing6 houses were positively) showed virtually no difference in planned and built and when people were rates of T. cruzi infection. However, when the being relocated to them endemic Chagas’ three study areas were assessed separately, the disease was not considered, and that vector rate of positive responses was found to have control measures were only taken after the been slightly higher among males in the Itu- problem had emerged. However, the results zaingo Project area (see Table l), among of the surveys reported here are being used by males on Apipt Chico Island (see Table 3), the National Chagas’ Disease Service in the and among females on Apipe Grande Island Corrientes area as the basis for a campaign (see Table 2). against T. in&tans in Ituzaingo Department. Although no particular significance is at- 344 PAHO BULLETIN l vol. 15, no. 4, 1981

ACKNOWLEDGMENTS

This study was carried out with the linan- YacyretL Binational Agency; to Dr. Ramon cial support of Argentina’s Ministry of Public Salas of the San Antonio Health Center of Health and Ministry of Science and Tech- ApipC Grande for the collaboration and ac- nology, through the School of Medicine of the commodations provided; to the principals and National University of the Northeast, as a teachers of national schools 19 and 352 and result of an understanding reached by the the provincial schools on ApipC Grande Yacyreta Binational Agency and the National Island; to the naval personnel of the National Scientific and Technical Research Council of Maritime District of Ituzaingo, Corrientes; Argentina. We also wish to express our thanks and to the technical personnel of the Labora- to the following people: to Dr. Adolf0 J. tory of the National Parasitology Center, Luis Maillie, Deputy Minister of Public Health of Armando Mosqueda, Eleuterio Sanchez, and Argentina, and Dr. Norberto Bienatti of the Maria T. Sanchez de Martinez.

SUMMARY

In late 1978 a survey was conducted to determine T. infestans was found in 12 per cent of the dwell- whether Chagas’ disease vectors and the disease ings inspected in the Ituzaingo Project and in 100 agent, T@anosoma cru.zi, were present in Argentine per cent of the ramshackle dwellings on the two locales near the site of the future Yacyretl-Apipt islands. Of the 255 triatomid bugs captured, 29 per Dam on the Paran% River. This work followed in- cent were found to contain T cruzi Likewise, near- vestigations that had found the vector Triatoma in- ly 46 per cent of the sera tested yielded antibodies &tans to be present in nearby communities on the against T. cruzi. These findings justify including the Paraguayan side of the river. region surveyed among those considered highly Three places were included in the survey. These endemic for Chagas’ disease in Argentina. were the area of the Ituzaingd housing project, The survey also showed that provision of new where people displaced by the dam construction housing ill-suited to vector proliferation had re- had been provided with new housing; Apip& duced but not eliminated T. infestans populations. Grande, an inhabited island in the Parana River; The circumstances involved (especially construc- and Apipt Chico, a smaller inhabited island. In all, tion of vector-prone huts in the yards of new 99 dwellings were searched for insect vectors (after residences) demonstrated that besides new housing, releasing pyrethrum to dislodge them), and sera appropriate health education is needed to guide from 435 residents were tested for the presence of people away from traditional behavior patterns antibodies against T. cruzi likely to cause infection.

REFERENCES

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