Browsing by Autor "Claudia Aliaga"

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Bias due to methods of parasite detection when estimating prevalence of infection ofTriatoma infestansbyTrypanosoma cruzi
(Wiley, 2016) Frédéric Lardeux; Claudia Aliaga; Stéphanie Depickère
The study aimed to quantify the bias from parasite detection methods in the estimation of the prevalence of infection of Triatoma infestans by Trypanosoma cruzi, the agent of Chagas disease. Three common protocols that detect T. cruzi in a sample of 640 wild-caught T. infestans were compared: (1) the microscopic observation of insect fecal droplets, (2) a PCR protocol targeting mini-exon genes of T. cruzi (MeM-PCR), and (3) a PCR protocol targeting a satellite repeated unit of the parasite. Agreement among protocols was computed using Krippendorff Kα. The sensitivity (Se) and specificity (Sp) of each protocol was estimated using latent class models. The PCR protocols were more sensitive (Se > 0.97) than microscopy (Se = 0.53) giving a prevalence of infection of 17-18%, twice as high as microscopy. Microscopy may not be as specific as PCR if Trypanosomatid-like organisms make up a high proportion of the sample. For small T. infestans, microscopy is not efficient, giving a prevalence of 1.5% when PCR techniques gave 10.7%. The PCR techniques were in agreement (Kα = 0.94) but not with microscopy (Kα never significant with both PCR techniques). Among the PCR protocols, the MeM-PCR was the most efficient (Se=1; Sp=1).
Calculation of the ELISA’s cut-off based on the change-point analysis method for detection of Trypanosoma cruzi infection in Bolivian dogs in the absence of controls
(Instituto Oswaldo Cruz, Ministério da Saúde, 2016) Frédéric Lardeux; Gino Torrico; Claudia Aliaga
In ELISAs, sera of individuals infected by Trypanosoma cruzi show absorbance values above a cut-off value. The cut-off is generally computed by means of formulas that need absorbance readings of negative (and sometimes positive) controls, which are included in the titer plates amongst the unknown samples. When no controls are available, other techniques should be employed such as change-point analysis. The method was applied to Bolivian dog sera processed by ELISA to diagnose T. cruzi infection. In each titer plate, the change-point analysis estimated a step point which correctly discriminated among known positive and known negative sera, unlike some of the six usual cut-off formulas tested. To analyse the ELISAs results, the change-point method was as good as the usual cut-off formula of the form "mean + 3 standard deviation of negative controls". Change-point analysis is therefore an efficient alternative method to analyse ELISA absorbance values when no controls are available.
Combination of cytochrome b heteroduplex-assay and sequencing for identification of triatomine blood meals
(Elsevier BV, 2011) Rosio Buitrago; Stéphanie Depickère; Marie-France Bosseno; Edda Siñani Patzi; Etienne Waleckx; Renata Salas; Claudia Aliaga; Simone Frédérique Brénière
Comparison of transmission parameters between Anopheles argyritarsis and Anopheles pseudopunctipennis in two ecologically different localities of Bolivia
(BioMed Central, 2013) Frédéric Lardeux; Claudia Aliaga; Rosenka Tejerina; Libia Torrez
Development of Exon-Primed Intron-Crossing (EPIC) PCR primers for the malaria vector Anopheles pseudopunctipennis (Diptera: Culicidae)
(Elsevier BV, 2012) Frédéric Lardeux; Claudia Aliaga; Rosenka Tejerina; Raùl Ursic-Bedoya
Using the Anopheles gambiae Giles genome as a template, we designed, screened and identified 14 novel Exon-Primed Intron-Crossing (EPIC) PCR primer pairs for Anopheles pseudopunctipennis Theobald 1901, a major vector of human Plasmodium sp. in South America. These primers were designed to target the conserved regions flanking consecutive exons of different genes and enabled the amplification of 17 loci of which nine were polymorphic. Polymorphisms at these loci ranged from two to four alleles. Intron length polymorphism analysis is a useful tool, which will allow the study of the population structure of this mosquito species, which remains poorly understood.
Eco-epidemiologia de la enfermedad de Chagas en comunidades pobres de Bolivia
(European Organization for Nuclear Research, 2012) Frédéric Lardeux; Lizet Zambrana; Claudia Aliaga; Renata Salas; Gino Torrico; T. Chavez
Experimental control of Triatoma infestans in poor rural villages of Bolivia through community participation
(Oxford University Press, 2015) Frédéric Lardeux; Stéphanie Depickère; Claudia Aliaga; Tamara Chávez; Lilian Zambrana
Even if cleaning activities were still neglected, community participation proved to be effective in reducing house infestation.
Further interest of miniexon multiplex PCR for a rapid typing of Trypanosoma cruzi DTU groups
(Elsevier BV, 2011) Claudia Aliaga; Simone Frédérique Brénière; Christian Barnabé
Genetic Characterization of Trypanosoma cruzi DTUs in Wild Triatoma infestans from Bolivia: Predominance of TcI
(Public Library of Science, 2012) Simone Frédérique Brénière; Claudia Aliaga; Etienne Waleckx; Rosio Buitrago; Renata Salas; Christian Barnabé; Michel Tibayrenc; François Noireau
By exploring large-scale DTUs that infect the wild populations of T. infestans, this study opens the discussion on the origin of TcI and TcV DTUs that are predominant in domestic Bolivian cycles.
Culex (Culex) acharistus, Root, 1927 (Diptera: Culicidae), a new record for Bolivia
(2025) Frédéric Lardeux; Philippe Boussès; Carolina Quezada; Audric Berger; Rosenka Lardeux; Claudia Aliaga; Libia Torrez
Abstract This study reports the first confirmed records of Culex (Culex) acharistus, Root, 1927 in Bolivia, based on both morphological examination and biomolecular identification using the cytochrome c oxidase subunit I (COI) marker. Specimens were collected in four localities representing diverse environmental settings: La Paz (urban environment, ≍3600 m), the nearby high-altitude city of El Alto (≍4000 m), Cochabamba (semi-rural and urban habitats, ≍2600 m), and Licoma a large village in the Yungas region (subtropical environment, ≍1900 m). The larval habitats where the species was found closely match those reported in neighboring countries where Cx. acharistus also occurs, ranging from typical small peridomestic sites to ponds, ditches, and river seepages in semi-rural areas. All identification methods yielded unambiguous results, confirming the species’ presence in Bolivia and extending its known distribution in South America. This finding highlights the importance of integrating morphological and molecular approaches to achieve accurate and reliable mosquito species identification.
New Discoveries of Sylvatic Triatoma infestans (Hemiptera: Reduviidae) Throughout the Bolivian Chaco
(American Society of Tropical Medicine and Hygiene, 2012) Etienne Waleckx; Stéphanie Depickère; Renata Salas; Claudia Aliaga; Marcelo Monje; Hiber Calle; Rosio Buitrago; François Noireau; Simone Frédérique Brénière
Sylvatic populations of Triatoma infestans might be involved in the recolonization of human dwellings. We report here the discoveries of new T. infestans sylvatic foci in the Bolivian Chaco. Eighty-one triatomines were caught, 38 of which were identified as T. infestans. Triatoma sordida and Panstrongylus geniculatus were the other species collected. One T. infestans and one T. sordida were infected with Trypanosoma cruzi TcI; one T. infestans was infected with TcII. These discoveries add to the debate on the geographic distribution of sylvatic T. infestans populations, the geographic origin of the species, and the epidemiological role of these populations.
New insights on the Chagas disease main vector Triatoma infestans (Reduviidae, Triatominae) brought by the genetic analysis of Bolivian sylvatic populations
(Elsevier BV, 2011) Etienne Waleckx; Renata Salas; Nerida Huamán; Rosio Buitrago; Marie-France Bosseno; Claudia Aliaga; Christian Barnabé; Roberto Rodríguez; Faustine Zovéda; Marcelo Monje
Optimization of a semi-nested multiplex PCR to identify Plasmodium parasites in wild-caught Anopheles in Bolivia, and its application to field epidemiological studies
(Oxford University Press, 2008) Frédéric Lardeux; Rosenka Tejerina; Claudia Aliaga; Raùl Ursic-Bedoya; Carl Lowenberger; Tamara Chávez
Without an adequate DNA extraction protocol, the identification of Plasmodium species in whole mosquitoes by PCR is difficult because of the presence of reaction inhibitors from the insects. In this study, eight DNA extraction protocols were tested, from which a chelex-based protocol was selected. Then a semi-nested multiplex PCR technique that detects and distinguishes among the four human Plasmodium species in single mosquitoes and in pools of up to 100 mosquitoes was optimized. The technique was used to detect P. vivax in wild-caught Anopheles pseudopunctipennis from a village in the Andean valleys of Bolivia in May 2003. The prevalence of infection was 0.9%. This is the first direct evidence of P. vivax transmission by this vector in this country. The extraction and PCR technique presented here can be useful to: (1) estimate Plasmodium prevalence in Anopheles populations in low prevalence areas where large numbers of individual mosquitoes would need to be processed to obtain a reliable estimate; (2) incriminate Anopheles species as malaria vectors; (3) identify all the circulating Plasmodium species in vectors from an area; (4) detect mixed infections in mosquitoes; and (5) detect mosquitoes with low-level parasite infections.
Statistical analysis of larval postspiracular filament length reveals continuous variation in Bolivian Anopheles pseudopunctipennis (Diptera: Culicidae)
(2025) Frédéric Lardeux; D. Albornoz Vásquez; Rosenka Tejerina; Claudia Aliaga; Lineth García; Libia Torrez
Abstract Anopheles pseudopunctipennis is a neotropical malaria vector widely distributed from northern Argentina and Chile to the southern United States. At the larval stage, it is characterized by posterior-lateral caudal filaments, which vary markedly in length within the same samples in Bolivia, with some individuals displaying unusually long filaments. The coexistence of individuals with relatively long and relatively short filaments raises the question of whether at least two distinct populations could be differentiated based on caudal filament length. This study examined filament-length distributions in two Bolivian dry-valley populations, El Chaco and Mataral, to determine whether variation reflects distinct subpopulations or continuous phenotypic variation within a single population. Distributions deviated from normality, exhibiting moderate skewness and tail heaviness, and the Generalized Error Distribution provided the best statistical fit. Examination of outliers and a targeted analysis of the distribution tail using multiple complementary methods showed that extreme values did not form a discrete secondary cluster but rather represented the upper continuum of the trait range. The two sites showed broadly comparable distributions, consistent with similar environmental conditions. These results emphasize the importance of using appropriate distributional models for continuous traits, highlight the occurrence of rare extreme phenotypes within otherwise homogeneous populations, and provide a baseline for future studies on the ecological and genetic determinants of caudal filament variation in An. pseudopunctipennis .