Geometric morphometrics and ecological niche modelling for delimitation of near-sibling triatomine species.

Identifying morphologically similar triatomine species is key to Chagas' disease vector control and surveillance, but remains challenging when only qualitative phenotypic data are available. We investigated whether morphometric and ecological variation can provide additional criteria for species delimitation by combining geometric morphometrics and ecological niche modelling to characterize two near-sibling triatomine species, Triatoma sordida and Triatoma garciabesi (Reduviidae: Triatominae). We analysed size and shape variation in 231 wings and 123 heads from one T. garciabesi and three T. sordida populations. Predicted distribution maps (21 climatic variables, 324 vector occurrence points) were produced using the Maxent method. Multivariate analyses summarized morphological and ecological variation. Wings and heads of T. sordida were significantly larger and more elongated than those of T. garciabesi. Discriminant analyses separated the species, with a partial overlap between Argentinean populations. The predicted distribution of T. garciabesi included northwest Argentina (mainly arid Chaco), whereas that of T. sordida included northeast Argentina (humid Chaco) and the Brazilian Cerrado and Caatinga ecoregions. Clear ecological niche differences were observed, with T. garciabesi occupying colder and drier areas than T. sordida. Our results show how morphometric variation and niche divergence can be used to enhance operational criteria for the delimitation of phenotypically similar triatomine species.

Genetic variability of Triatoma rubrovaria (Reduviidae: Triatominae) from Brazil, Argentina and Uruguay as revealed by two different molecular markers.

Randomly amplified polymorphic DNA (RAPD) and nuclear ribosomal DNA sequence analyses were used to assess the genetic population structure of the South American triatomine species Triatomo rubrovario throughout its geographical distribution. To investigate the genetic variability at both intraspecific and intrapopulational levels the RAPD profiles and the nucleotide sequences of the rDNA intergenic spacers, ITS-1 and ITS-2, were analysed and compared. The phenetic analysis based on RAPD profiles show three distinct clusters diverging by similarity coefficients ranging from 0.62 to 0.96. The ITS-1 and ITS-2 sequence variability detected may be considered very high, suggesting reproductive isolation between populations. A total of seven composite haplotypes (CH) were found, among which three are specific for Brazil, other three for Uruguay, and the last one common for the three countries studied. The population studied in Argentina does not represent an independent CH. Sequence analyses proved that the five populations studied are easily differentiable and that there is heterogeneity within each one. True mutations and indels are the responsible of sequence differences between haplotypes and populations, suggesting that divergence processes may presently go on within this species. The large intraspecific variability detected may underlie the known plasticity of T. rubrovaria, making it a potential intradomiciliary invader and consequently an appropriate vector for Chagas disease transmission. Therefore, this triatomine species must be continuously monitored throughout.

Epidemiología de la enfermedad de Chagas en San Roque, Corrientes: infestación por triatominos y seroprevalencia humana / Epidemiology of Chagas disease in San Roque, Corrientes: Triatomine infestation and human seroprevalence

El objetivo fue evaluar la presencia de triatominos en ecotopos domésticos y extradomésticos localizados en el área circundante a una comunidad de palmas, determinar el índice de infección de los triatominos y estimar la prevalencia humana de individuos serorreactivos al Trypanosoma cruzi. Los muestreos se efectuaron en primavera de 1998 y en verano de 1999 en Colonia Laurel, Departamento San Roque, Corrientes, Argentina. La colección de triatominos se realizó por el método de captura/ hora/ hombre. La identificación del T. cruzi se efectuó según criterios morfológicos y por PCR. El diagnóstico de la infección chagásica se llevó a cabo en pobladores voluntarios mediante las pruebas de hemaglutinación indirecta e inmunofluorescencia indirecta. Se analizaron 16 viviendas, 11 resultaron infestadas por Triatoma infestans y dos por Triatoma sordida. Se colectaron 122 ejemplares de T. infestans de todas las edades. La infección por T. cruzi fue 16.7%. Triatoma infestans fue la especie predominante en el domicilio y T. sordida en el peridomicilio. El 77.9% (88/113) de los pobladores se analizaron serológicamente y la prevalencia fue 26.1%. La tasa de infección fue relativamente alta en el grupo etario de 0-10 años. El porcentaje de seropositividad se incrementó con la edad y ascendió al 66.6% en los pobladores de más de 40 años. La presencia de T. infestans, de pobladores serorreactivos y de niños seropositivos ≤4 años, así como las condiciones precarias de vida, indican que la endemia chagásica continúa siendo un problema en el área de estudio.

Epidemiología de la enfermedad de Chagas en San Roque, Corrientes: infestación por triatominos y seroprevalencia humana / Epidemiology of Chagas disease in San Roque, Corrientes: Triatomine infestation and human seroprevalence

El objetivo fue evaluar la presencia de triatominos en ecotopos domésticos y extradomésticos localizados en el área circundante a una comunidad de palmas, determinar el índice de infección de los triatominos y estimar la prevalencia humana de individuos serorreactivos al Trypanosoma cruzi. Los muestreos se efectuaron en primavera de 1998 y en verano de 1999 en Colonia Laurel, Departamento San Roque, Corrientes, Argentina. La colección de triatominos se realizó por el método de captura/ hora/ hombre. La identificación del T. cruzi se efectuó según criterios morfológicos y por PCR. El diagnóstico de la infección chagásica se llevó a cabo en pobladores voluntarios mediante las pruebas de hemaglutinación indirecta e inmunofluorescencia indirecta. Se analizaron 16 viviendas, 11 resultaron infestadas por Triatoma infestans y dos por Triatoma sordida. Se colectaron 122 ejemplares de T. infestans de todas las edades. La infección por T. cruzi fue 16.7%. Triatoma infestans fue la especie predominante en el domicilio y T. sordida en el peridomicilio. El 77.9% (88/113) de los pobladores se analizaron serológicamente y la prevalencia fue 26.1%. La tasa de infección fue relativamente alta en el grupo etario de 0-10 años. El porcentaje de seropositividad se incrementó con la edad y ascendió al 66.6% en los pobladores de más de 40 años. La presencia de T. infestans, de pobladores serorreactivos y de niños seropositivos ≤4 años, así como las condiciones precarias de vida, indican que la endemia chagásica continúa siendo un problema en el área de estudio. (AU)

Competition between vectors of Chagas disease, Triatoma infestans and T. sordida: effects on fecundity and mortality.

Interspecific competition between two species of triatomine bugs (Hemiptera: Reduviidae), vectors of Chagas disease, was assessed for 16 months through comparative fecundity and mortality of experimental populations in chicken nests, maintained indoors with ambient conditions. Triatoma sordida (Stål), the secondary vector in north-eastern Argentina, was compared with Triatoma infestans (Klug) the more widespread domestic vector in the southern cone of South America. Both species populations originated from females collected in 1995 from the community of Empedrado, Corrientes, Argentina. Three population units were monitored: T. infestans alone, T. sordida alone and both species together in equal proportions. Each population started with six male and six female adults, 116 eggs, and nymphal instars I to V numbering 82, 48, 16, 11 and 19, respectively. Numbers and weight of individual bugs were recorded monthly (August 1995 to December 1996). The pure populations of T. infestans and T. sordida showed temporal changes in abundance, rising in summer and falling in winter, similar to the typical trends under normal field conditions. In the mixed population, however, T. sordida fell to extinction after 6 months, whereas T. infestans reached similar abundance to the pure (control) population. For each nymphal instar of T. sordida, the mean body weight was significantly less and mortality rate was higher in the mixed population compared to the pure population, but there were no significant differences of adult longevity or fecundity between the pure and mixed populations of T. sordida. The apparent competitive displacement of T. sordida by T. infestans was attributed to the latter species having better ability to obtain bloodmeals. This might explain the rarity of mixed populations where these two species occur in sympatry.

Triatoma sordida Stål 1859 (Hemiptera, Reduviidae: Triatominae) in palms of northeastern Argentina.

Several palms species provide an important habitat for triatomines and associate vertebrates in tropical America. The objective of this work is to identify the triatomine species living in the palms of rural areas in the Province of Corrientes, and to estimate the potential epidemiological risk they represent for the residents of nearby houses. The survey was carried out in a palm community in Colonia Laurel, Department San Roque, Province of Corrientes, Argentina. Samplings were performed in October, November and December 1998; January, February and March 1999; May and June 1999. Thirty palms: 27 (90%) Butia yatay (Mart.) Becc. and 3 Acrocomia aculeata (Jacq.) Lodd ex Mart. were dissected. Triatoma sordida Stål 1859 was found in 96.2% of B. yatay and in all the A. aculeata palms. A total of 272 live T. sordida was collected; 36 of them (13.2%) were found in bird nests in the frond and the remainder in other locations of the tree. The mean number of triatomines per palm was 9.6 (range 1-60, mode 2). T. sordida was collected during all the sampling months and all stages were present at all seasons. The highest population density was reached in spring and the lowest in autumn. Trypanosoma cruzi was detected in 38.5% in feces of 174 examined insects and identified as such, both by microscopical examination and PCR. This is the first finding of T. sordida populations in B. yatay, an endemic palm of South America distributed in southern Brazil, Uruguay and northeastern Argentina. The high infection prevalence found in this work suggests that T. sordida plays an essential role in the maintenance of the wild T. cruzi transmission cycle in northeastern Argentina.

[Detection of triatomines (Hemiptera: Reduviidae) in domiciliary and extra-domiciliary ecotopes. Corrientes, Argentina. ]. / Detección de triatominos (Hemiptera: Reduviidae) en ambientes domésticos y extradomésticos. Corrientes, Argentina.

In order to identify intra- and extra-domiciliary triatomines, a study in different counties of Corrientes Province, Argentina, was conducted from 1985 to 1995. Triatoma infestans (Klug, 1834), Triatoma sordida (Stål, 1859), Panstrongylus geniculatus (Latreille, 1811), and Panstrongylus megistus (Burmeister, 1835) were detected in domestic ecotopes. T. infestans and T. sordida were also found in the peridomicile. Triatoma platensis (Neiva, 1913), Psammolestes coreodes (Bergroth, 1911), T. sordida, and Triatoma rubrovaria (Blanchard, 1843) were collected in sylvatic biotopes. T. infestans was confirmed as the predominant species in the domestic environment and was the only species infected with Trypanosoma cruzi-like parasites. T. sordida was most frequent in extra-domiciliary ecotopes, but could be considered capable of colonizing human dwellings.

Interactions between Triatoma infestans and Triatoma sordida (Hemiptera: Reduviidae) in artificial ecotopes: population growth and age structure.

Interaction characteristics between Triatoma infestans Klug, 1834 and Triatoma sordida Stal, 1859 populations were studied in artificial ecotopes for 16 mo. The experimental design involved simultaneous treatments with T. infestans and T. sordida together in the same experimental unit (EU) and each separately in two control units (CU) made of adobe bricks. Chickens were used as host animals. Each unit was dismantled monthly to estimate triatomine population size and age structure, rebuilt, and repopulated with the same insects. In both units, T. infestans population growth followed a logistic model, whereas T. sordida did not show this pattern. T. infestans completed a generation in 24 wk (EU) and 32 wk (CU1), whereas T. sordida did not complete one generation during this period. We concluded that T infestans showed a better colonizing success than T. sordida. After living together for 1 yr, an interference process took place that resulted in the extinction of T. sordida.

[Contribution to knowledge of reservoirs of Trypanosoma cruzi (Chagas, 1909) in Corrientes Province, Argentina]. / Contribución al conocimiento de los reservorios del Trypanosoma cruzi (Chagas, 1909) en la Provincia de Corrientes, Argentina.

In order to identify Trypanosoma cruzi reservoirs in transmission areas, 60 mammals in Capital and San Luis del Palmar Departments, Corrientes, Argentina were studied. Primates, rodents, carnivores, marsupials and edentates were investigated, 40 of them living in captivity and 20 caught with traps in a rural area. The mammals were examined by xenodiagnosis and third or fourth instars nymphs of Triatoma infestans starved for 2 weeks were used. The feces were microscopically observed (400x) for Trypanosoma cruzi infection at 30, 60 and 90 days after feeding. Trypanosoma cruzi-like parasites were identified in 2 Saimiri sciureus and 1 Cebus apella analyzed by xenodiagnosis. It was concluded that parasitemia was low. However, the presence in a forest area of Didelphis albiventris, potential reservoir of the parasite, indicates a risk factor and deserves further epidemiological study for a true diagnosis of this endemic infection.

[Clinical cross-sectional and epidemiologic study of Chagas disease in a rural area of the Argentinian northeast]. / Estudio transversal clínico y epidemiológico de la enfermedad de Chagas en una área rural del Nordeste Argentino.

The main goal was to know the epidemiologic, clinical, electrocardiographic and radiologic characteristics among a population of seropositives and seronegatives to Trypanosoma cruzi in a rural area of the Department of San Miguel, province of Corrientes, Argentina. One hundred and thirty-two patients of different ages: 2-79 years old were researched (58 males, 74 females). In order to make a thorough assessment clinical evaluation and cardiologic testing were carried out. Signs and symptoms consistent with heart disease, blood pressure, 12-lead ECG registry and chest x-ray (PA view) were registered. In signs and symptoms, abnormal ECG patterns and radiologic abnormalities, non-significant statistic difference were observed. Although we were unable to find a significant relationship between chagasic infection and a higher prevalence for heart disease, it is important to stress the fact that 54.0% of the studied population was largely composed of very young patients whose ages were less than 20 years old, and 45.0% of those older than 41 years showed ECG abnormalities.

Estudio transversal clínico y epidemiológico de la enfermedad de Chagas en una área rural del Nordeste Argentino / Clinical cross-sectional and epidemiologic study of Chagas disease in a rural area of the Argentinian northeast

Esta investigación tiene por objeto analizar las características epidemiológicas, clínicas, electrocardiográficas y radiológicas de una población de seropositivos y seronegativos al Trypanosoma cruzi en una área rural del Departamento San Miguel, provincia de Corrientes, Argentina. Se seleccionaron 132 pobladores (58 hombres y 74 mujeres) de todos los grupos etareos para la realización de un examen clínico y cardiovascular. Se registraron síntomas y signos compatibles con afección cardíaca, tensión arterial, electrocardiograma de 12 derivaciones y radiografía anteroposterior de tórax. En la signo-sintomatología, anomalías electrocardiográficas y en las alteraciones radiográficas detectadas, no se observaron diferencias estadísticamente significativas entre seropositivos y seronegativos. Se concluye que si bien en la población objeto de estudio la infección chagásica no se asoció a mayor prevalencia de cardiopatía, cabe destacar que los pacientes chagásicos pertenecían a un grupo etareo muy joven con un 54,0% de ellos menores de 20 años y que el 45,0% de los pacientes mayores de 41 años tenían alteraciones electrocardiográficas.

The main goal was to know the epidemiologic, clinical, electrocardiographic and radiologic characteristics among a population of seropositives and seronegatives to Trypanosoma cruzi in a rural area of the Department of San Miguel, province of Corrientes, Argentina. One hundred and thirty-two patients of different ages: 2-79 years old were researched (58 males, 74 females). In order to make a thorough assessment clinical evaluation and cardiologic testing were carried out. Signs and symptoms consistent with heart disease, blood pressure, 12-lead ECG registry and chest x-ray (PA view) were registered. In signs and symptoms, abnormal ECG patterns and radiologic abnormalities, non-significant statistic difference were observed. Although we were unable to find a significant relationship between chagasic infection and a higher prevalence for heart disease, it is important to stress the fact that 54.0% of the studied population was largely composed of very young patients whose ages were less than 20 years old, and 45.0% of those older than 41 years showed ECG abnormalities.

[Domestic infestation by Triatoma infestans and prevalence of Trypanosoma cruzi seropositives in a rural area of the Argentinian northeast]. / Infestacion domestica por Triatoma infestans y prevalencia de seropositivos al Trypanosoma cruzi en un area rural del nordeste argentino.

An epidemiological study was carried out from April 1991 to December 1993 to obtain a general view of T. cruzi domestic transmission in rural areas of San Miguei Department, Corrientes. From 100 analyzed households, 50.0% was infested by T infestans (Klug, 1834) and 1.0% by T. sordida (Stal, 1859). Domiciliary colonization by T. sordida is reported for first time in Corrientes province. T. cruzi infection of T. infestans was 23.1%. Indirect hemagglutination and indirect immunofluorescence antibody tests were used for detection of anti T. cruzi antibodies in 388 human sera, 23.4% showed serological reactivity. An important high rate (12.9%) was observed in the age group of higher transmission risk. Seropositives percentages increased with age and reached 50.0% in 31-40 years old group. Domestic infestation by T. infestans, seropositive human prevalence to T. cruzi and householders precarious life conditions prove that this endemic disease is still a problem in the studied area.

[Population statistics of Triatoma sordida Stäl 1859 (Hemiptera:Reduviidae) in experimental conditions]. / Estadísticos poblacionales de Triatoma sordida Stäl 1859 (Hemiptera:Reduviidae) en condiciones experimentales.

Four cohorts of 100 Triatoma sordida eggs were reared under standard laboratory conditions (28 degrees C, 63% R.H.) and fed weekly on hens during 40 minutes. The numbers of dead insects, moults and eggs laid were recorded weekly. A constant survival value was observed without any important peaks in the four cohorts. Life expectancy was 37.4 weeks for males and 36.8 weeks for females. The average generation time was 61.7 weeks. The average net reproduction rate suggests that this population would increase 143.2 times during each generation. The average intrinsic rate of natural increase was 0.082 per individual per week. The highest reproductive value was observed 3 weeks after entering the adult stage. The age structure, assuming stable age distribution, would be 32% eggs, 26% of first instar nymphs, 19% of second instar nymphs, 13% of third instar nymphs, 6% of fourth instar nymphs, 3% of fifth instar nymphs and 1% of adults. Our results suggest that this species behaves as a k-strategist under experimental conditions.

[Population interactions between Triatoma infestans and Triatoma sordida]. / Interacción entre poblaciones de Triatoma infestans y Triatoma sordida.

Populations of T. infestans and T. sordida were studied between September 1988 and April 1989 with a view to discovering if any kind of interaction took place between them while they lives together in the same experimental unit and exploited the same food resource (chicken). The initial age structure for each species was: 27 N1, 7 N2, 11 N3, 3 N4, 8 N5, 4 males and 10 females. The population dynamics nutritional status, predation and gregarious behavior were estimated by means of a monthly census. The colonizing success of T. infestans was greater than that of T. sordida in view of the values obtained: fecundity (146 eggs/female), longevity (157.8 days) and mortality (39.4) compared with the values recorded for T. sordida: 118 eggs/female, 81.1 days and 54.0% respectively. The population growth of T. insfestans followed an exponential model, with a high nymphal recruitment rate, while the T. sordida population was early extinguished. In general, the average weight of T. infestans remained close to the initial values while that of T. sordida declined. Gregarious groups were formed principally in the inferior sector of wall 1 (near the host) with a higher aggregation in T. infestans. These results make it possible to propose the hypothesis of the competitive superiority of T. infestans.

[Presence of Triatoma sordida Stäl, 1859 in urban ecotopes, of the city of Corrientes, Argentina]. / Presencia de Triatoma sordida Stäl, 1859 en ecotopos urbanos de la ciudad de Corrientes, Argentina.

With the intention of verifying the presence of T. sordida Stál 1859 in urban ecotopes in Corrientes city, Argentina, both, human dwellings and an extradomiciliary habitat were taken as a basis. A complete T. sordida population census was carried on in Mitre Park pigeon house and 400 pigeon nests (Columbia livia) were dissected. The triatomineos samples that had been detected in human dwellings were sent to the Arthropods Laboratory by their inhabitants. These triatomineos were classified systematically and according to their age class. Their feces were examined under a microscope 400 x, so as to identify Trypanosoma cruzi. Six eggs, 45 first-instar nymphs, 110 second-instar nymphs, 226 third-instar nymphs, 303 fourth-instar nymphs, 1.103 fifth-instar nymphs, 12 females and 11 males were collected from the pigeon house. The presence of this species was verified in the 27 houses, situated in 8 different neighborhoods in the city; 13 eggs, 33 different instar nymphs, 27 females and 9 males were captured, 82 samples altogether. No triatomineo was infected by T. cruzi. T. sordida adults moved towards the houses in Spring and Summer. Of the material found in human dwellings 33% was female. The adaptation of T. sordida to extra-domestic habitats and their tendency to invade human houses has thus been verified. This fact should be taken into account in vector control programs.

[Triatoma infestation in the San Luis del Palmar Department of Corrientes Province, Argentina]. / Triatomismo del Departamento San Luis del Palmar de la provincia de Corrientes, Argentina.

The purpose of this study was to determine domestic and peridomestic infestation of Triatominae, Trypanosoma cruzi infection rates, and the prevalence of human seroreactivity in rural areas of the Department of San Luis del Palmar, Corrientes, Argentina (Fig. 1). The study took place from April 1986 to May 1989. The Department of San Luis del Palmar covers an area of 2551 km2 and is part of the Neotropical biogeographic region, Chacoan Dominion and Province. The climate is of the subhumid type. The mean annual temperature is 21.6 degrees C. Some localities were chosen because of the presence of triatominae. Households were carefully examined and classified according to their building materials. A 0.2% solution of tetrametrine was sprayed in all possible hiding places to dislodge bugs, which were collected by capture/hour/man methods. A survey to determine the socioeconomical, sanitary, and cultural conditions of house-dwellers was carried out. The same method was used to examine peridomiciles and total demolition was carried out in the positive ones. Fecal examination was carried out to verify the presence of T. cruzi in collected insects and observed at 400X. Human blood was obtained through venipuncture. The serum was kept in a freezer until examined. Serologic studies included indirect hemagglutination test (IHAT) and indirect immunofluorescence antibody test (IFAT). Positive titer for IHAT and IFAT was 1/64. Seroreactives were those that had two positive assays. The whole data obtained was analyzed by chi 2 tests. From one hundred households studied, 80% belonged to huts and 20% to houses. Mud walls were predominant in huts while brick walls were predominant in houses.(ABSTRACT TRUNCATED AT 250 WORDS)

Triatomismo del Departamento San Luis del Palmar de la provincia de Corrientes, Argentina. / [Triatoma infestation in the San Luis del Palmar Department of Corrientes Province, Argentina]

The purpose of this study was to determine domestic and peridomestic infestation of Triatominae, Trypanosoma cruzi infection rates, and the prevalence of human seroreactivity in rural areas of the Department of San Luis del Palmar, Corrientes, Argentina (Fig. 1). The study took place from April 1986 to May 1989. The Department of San Luis del Palmar covers an area of 2551 km2 and is part of the Neotropical biogeographic region, Chacoan Dominion and Province. The climate is of the subhumid type. The mean annual temperature is 21.6 degrees C. Some localities were chosen because of the presence of triatominae. Households were carefully examined and classified according to their building materials. A 0.2

solution of tetrametrine was sprayed in all possible hiding places to dislodge bugs, which were collected by capture/hour/man methods. A survey to determine the socioeconomical, sanitary, and cultural conditions of house-dwellers was carried out. The same method was used to examine peridomiciles and total demolition was carried out in the positive ones. Fecal examination was carried out to verify the presence of T. cruzi in collected insects and observed at 400X. Human blood was obtained through venipuncture. The serum was kept in a freezer until examined. Serologic studies included indirect hemagglutination test (IHAT) and indirect immunofluorescence antibody test (IFAT). Positive titer for IHAT and IFAT was 1/64. Seroreactives were those that had two positive assays. The whole data obtained was analyzed by chi 2 tests. From one hundred households studied, 80

belonged to huts and 20

to houses. Mud walls were predominant in huts while brick walls were predominant in houses.(ABSTRACT TRUNCATED AT 250 WORDS)

Triatomismo del Departamento San Luis del Palmar de la provincia de Corrientes, Argentina. / [Triatoma infestation in the San Luis del Palmar Department of Corrientes Province, Argentina]

The purpose of this study was to determine domestic and peridomestic infestation of Triatominae, Trypanosoma cruzi infection rates, and the prevalence of human seroreactivity in rural areas of the Department of San Luis del Palmar, Corrientes, Argentina (Fig. 1). The study took place from April 1986 to May 1989. The Department of San Luis del Palmar covers an area of 2551 km2 and is part of the Neotropical biogeographic region, Chacoan Dominion and Province. The climate is of the subhumid type. The mean annual temperature is 21.6 degrees C. Some localities were chosen because of the presence of triatominae. Households were carefully examined and classified according to their building materials. A 0.2

solution of tetrametrine was sprayed in all possible hiding places to dislodge bugs, which were collected by capture/hour/man methods. A survey to determine the socioeconomical, sanitary, and cultural conditions of house-dwellers was carried out. The same method was used to examine peridomiciles and total demolition was carried out in the positive ones. Fecal examination was carried out to verify the presence of T. cruzi in collected insects and observed at 400X. Human blood was obtained through venipuncture. The serum was kept in a freezer until examined. Serologic studies included indirect hemagglutination test (IHAT) and indirect immunofluorescence antibody test (IFAT). Positive titer for IHAT and IFAT was 1/64. Seroreactives were those that had two positive assays. The whole data obtained was analyzed by chi 2 tests. From one hundred households studied, 80

belonged to huts and 20

to houses. Mud walls were predominant in huts while brick walls were predominant in houses.(ABSTRACT TRUNCATED AT 250 WORDS)