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Absence of convincing evidence of Coxiella burnetii infection in Chile: a cross-sectional serosurvey among healthy adults in four different regions
(BMJ Publishing Group, 2016) Weitzel, Thomas; Lopez, Javier; Acosta-Jamett, Gerardo; Edouard, Sophie; Parola, Philippe; Abarca, Katia
Background: Coxiella burnetii is an important zoonotic pathogen of global distribution. Still, in most parts of South America including Chile, systematic epidemiological data are lacking. The presented study aims to determine the seroprevalence of Coxiella burnetii antibodies in healthy adults of four different regions in Chile. Methods: A cross-sectional study was performed, which included healthy adults living in rural and urban areas of four cities located in different regions in northern, central, and southern Chile. In urban sectors, households were chosen by double stratified random sampling, while in rural areas convenience sampling was performed. Serum specimens were taken and screened for the presence of IgG antibodies against C. burnetii phase II antigen using a commercial ELISA kit. Positive and indeterminate results were confirmed by a reference laboratory using indirect immunofluorescence assay (IFA). Results: A total of 1112 individuals were included. Of those, 8 were positive by ELISA, but only one sample was confirmed using IFA. Statistical analysis for population freedom from disease revealed a high probability that C. burnetii was absent in our study population. Conclusion: Our work provides the first epidemiological data on human Q fever in Chile indicating either a very low endemicity or the absence of this pathogen in the studied areas.
Canine seroprevalence to Orientia species in southern Chile: A cross-sectional survey on the Chiloé Island
(2018) Weitzel, Thomas; Jiang, Ju; Acosta-Jamett, Gerardo; Martínez-Valdebenito, Constanza; López, Javier; Richards, Allen L.; Abarca, Katia
Background Scrub typhus is a potentially life-threatening vector-borne infection caused by Orientia species. It occurs mainly in the Asian-Pacific region, where it causes significant morbidity and mortality. Recently, an endemic focus of scrub typhus has been described in South America, on Chiloé Island in southern Chile. Dogs have been used as sentinel hosts to determine the presence and spatial distribution of various vector-borne infections. Their suitability to gain insight into human exposure to Orientia tsutsugamushi has been suggested in studies from Asia. Methodology In January 2016, we conducted a cross-sectional study, which included the two main cities on Chiloé Island. Canine blood samples were obtained in households, chosen by double stratified random sampling in urban and by convenience in rural locations. Specimens were tested by ELISA for IgG antibodies against whole-cell antigen preparations from three strains of O. tsutsugamushi. Data were further analyzed for factors associated with seropositivity including spatial clustering. Results Serum samples from 202 dogs (104 urban, 98 rural) were tested for IgG against O. tsutsugamushi, of which 43 (21.3%) were positive. Seroprevalence rates were higher in rural than in urban settings (p<0.01) and in older compared to younger dogs (p<0.01). Spatial analysis by LISA indicated the presence of four localities of highly grouped cases. Conclusions The detected seroprevalence supports the endemicity of scrub typhus in southern Chile and suggests a wide exposure of household dogs to the infected, yet unknown vector(s). The spatial data will be used for future research identifying further human cases as well as the local vector(s)/reservoirs for scrub typhus in southern Chile. The study reinforces that dogs are useful sentinels for Orientia spp. in regions of uncertain endemicity and distribution.
Chigger Mites (Acariformes: Trombiculidae) of Chiloé Island, Chile, With Descriptions of Two New Species and New Data on the Genus Herpetacarus
(2020) Silva, María Carolina; Stekolnikov, Alexandr A.; Weitzel, Thomas; Beltrami, Esperanza; Martínez-Valdebenito, Constanza; Abarca, Katia; Acosta-Jamett, Gerardo
Three species of chigger mites are recorded in our collections from four species of cricetid rodents on Chiloé Island (southern Chile, Los Lagos Region), an area endemic to scrub typhus (Orientia sp.). Two species are described as new—Herpetacarus (Abonnencia) eloisae sp. nov. and Quadraseta chiloensis sp. nov. One species, Paratrombicula goffi Stekolnikov and González-Acuña 2012, is for the first time recorded on a mammal host (one species of cricetid rodent), and its distribution is extended to the Los Lagos Region of Chile. The genus Proschoengastia Vercammen-Grandjean, 1967 is synonymized with the subgenus Herpetacarus (Abonnencia) Vercammen-Grandjean, 1960, and four new combinations are established: Herpetacarus (Abonnencia) herniosa (Brennan and Jones, 1961), comb. nov., Herpetacarus (Abonnencia) insolita (Brennan and Jones, 1961), comb. nov., Herpetacarus (Abonnencia) macrochaeta (Brennan and Jones, 1961), comb. nov., and Herpetacarus (Abonnencia) antarctica (Stekolnikov and Gonzalez-Acuña, 2015), comb. nov.
Development of a New Genus-Specific Quantitative Real-Time PCR Assay for the Diagnosis of Scrub Typhus in South America
(2022) Jiang, Ju; Martínez, Constanza; Weitzel, Thomas; Farris, Christina; Acosta, Gerardo; Abarca, Katia; Richards, Allen
Scrub typhus is a potentially severe rickettsiosis, caused by Orientia tsutsugamushi in the Asia-Pacific region. Recently, however, two distinct pathogens, “Candidatus Orientia chuto” and “Candidatus Orientia chiloensis”, have been discovered in the Middle East and South America, respectively. Since the novel pathogens differ significantly from O. tsutsugamushi, many established diagnostic methods are unreliable. This work describes the development and validation of a new quantitative real-time PCR (qPCR) assay (Orien16S) for the detection of all known Orientia species. Based on a 94 bp sequence of the 16S rRNA gene (rrs), Orien16S recognized DNA samples from O. tsutsugamushi (n = 41), Ca. O. chiloensis (n = 5), and Ca. O. chuto (n = 1), but was negative for DNA preparations from closely related rickettsiae and other members of the order Rickettsiales (n = 22) as well as unrelated bacterial species (n = 11). After its implementation in Chile, the assay was verified, correctly identifying all tested eschar and buffy coat samples (n = 28) of clinical suspected cases. Furthermore, Orien16S detected Orientia DNA in trombiculid mites collected in endemic regions in southern Chile. The presented novel qPCR assay provides a useful tool for detecting Orientia and diagnosing scrub typhus from all geographical regions.
Different Safety Pattern of an Inactivated SARS-CoV-2 Vaccine (CoronaVac®) According to Age Group in a Pediatric Population from 3 to 17 Years Old, in an Open-Label Study in Chile
(2023) Le Corre, Nicole; Abarca, Katia; Astudillo, Patricio; Potin, Marcela; López, Sofía; Goldsack, Macarena; Valenzuela, Vania; Schilling Redlich, Andrea; Gaete, Victoria; Rubio, Lilian; Calvo, Mario; Twele, Loreto; González, Marcela; Fuentes, Daniela; Gutiérrez, Valentina; Reyes, Felipe; Tapia, Lorena I.; Villena, Rodolfo; Retamal-Díaz, Angello; Cárdenas, Antonio; Alarcón-Bustamante, Eduardo; Meng, Xing; Xin, Qianqian; González-Aramundiz, José V.; Alvarez-Figueroa, María Javiera; González, Pablo A.; Bueno, Susan M.; Soto, Jorge A.; on behalf of the PedCoronaVac03CL Study Group; Perret, Cecilia; Kalergis, Alexis M.
During the COVID-19 pandemic, the importance of vaccinating children against SARS-CoV-2 was rapidly established. This study describes the safety of CoronaVac® in children and adolescents between 3- and 17-years-old in a multicenter study in Chile with two vaccine doses in a 4-week interval. For all participants, immediate adverse events (AEs), serious AEs (SAEs), and AEs of special interest (AESIs) were registered throughout the study. In the safety subgroup, AEs were recorded 28 days after each dose. COVID-19 surveillance was performed throughout the study. A total of 1139 individuals received the first and 1102 the second dose of CoronaVac®; 835 were in the safety subgroup. The first dose showed the highest number of AEs: up to 22.2% of participants reported any local and 17.1% systemic AE. AEs were more frequent in adolescents after the first dose, were transient, and mainly mild. Pain at the inoculation site was the most frequent AE for all ages. Fever was the most frequent systemic AE for 3–5 years old and headache in 6–17 years old. No SAEs or AESIs related to vaccination occurred. Most of the COVID-19 cases were mild and managed as outpatients. CoronaVac® was safe and well tolerated in children and adolescents, with different safety patterns according to age.
Eco-epidemiology of rodent-associated trombiculid mites and infection with Orientia spp. in Southern Chile
(2023) Silva, María; Pérez, Caricia; Martínez, Constanza; Pérez, Ruth; Vial Cox, María Cecilia; Stekolnikov, Alexandr; Abarca, Katia; Thomas Weitzel; Weitzel, Thomas; Acosta, Gerardo
Background: Scrub typhus is a potentially severe infection caused by bacteria of the genus Orientia, endemic in Asia-Pacific and recently discovered in southern Chile. The presented study aimed to determine the prevalence and species richness of rodent-associated trombiculid mites and their infection with Orientia spp. in different areas of two regions in southern Chile. Methodology/principal findings: During summer 2020, trombiculid mites were collected from rodents captured in three areas in southern Chile known to be endemic for scrub typhus (Cochamó and Chiloé Island in the Los Lagos Region and Tortel in the Aysén Region). A total of 132 rodents belonging to five species were captured using Sherman-like traps; 89.4% were infested with trombiculids. Mite specimens were morphologically identified and subsequently tested by Orientia-specific qPCR. Six mite species were identified. Among chigger-infested rodents, 33.9% carried Orientia-positive mites; this rate was higher in Tortel (63.8%) than in Cochamó (45.0%) and Chiloé Island (2.0%). The analysis of individual mites (n = 901) revealed that 31.2% of Herpetacarus antarctica samples (n = 202) were positive for Orientia DNA; the prevalence was 7.0% in Paratrombicula neuquenensis (n = 213), 6.9% in Herpetacarus eloisae (n = 144), 3.6% in Argentinacarus expansus (n = 55), and 0% in Paratrombicula goffi (n = 110) and Quadraseta chiloensis (n = 177). The southernmost site (Tortel) showed the highest rates of trombiculid infestation, trombiculid load, and Orientia infection in the captured rodents. Conclusions/significance: Our study provides new insights into the trombiculid fauna and prevalence of Orientia in mites collected from wild rodents in southern Chile. Orientia DNA was detected in four of the six mite species. Rates of infestation, mite loads, and Orientia prevalences differed geographically and were highest in the Aysén Region. Our data improve our knowledge on possible vectors of scrub typhus and their distribution in Chile.
Endemic scrub typhus in South America
(Massachusetts Medical Society, 2016) Weitzel, Thomas; Dittrich, Sabine; Lopez, Javier; Phuklia, Weerawat; Martinez-Valdebenito, Constanza; Velásquez, Katia; Blacksell, Stuart; Paris, Daniel; Abarca, Katia
Scrub typhus is a life-threatening zoonosis caused by Orientia tsutsugamushi organisms that are transmitted by the larvae of trombiculid mites. Endemic scrub typhus was originally thought to be confined to the so called “tsutsugamushi triangle” within the Asia–Pacific region. In 2006, however, two individual cases were detected in the Middle East and South America, which suggested that the pathogen was present farther afield. Here, we report three autochthonous cases of scrub typhus caused by O. tsutsugamushi acquired on Chiloé Island in southern Chile, which suggests the existence of an endemic focus in South America.
Geographical distribution and phylogenetic analysis of Rhipicephalus sanguineus sensu lato in northern and central Chile
(2018) E. Díaz, Fabián; Martínez-Valdebenito, Constanza; López, Javier; Weitzel, Thomas; Abarca, Katia
The presented study analyzed the presence and geographical distribution of the tropical and temperate lineages of Rhipicephalus sanguineus sensu lato in Chile. R. sanguineus s.l. ticks were collected from dogs at 14 sites in northern and central Chile for morphological and genetic analysis based on the 16S rDNA gene. Phylogenetic studies proved the existence of both, the tropical and the temperate lineages. The former was represented by a single haplotype and occurred in the far north; the latter included four haplotypes and was observed from the Tarapacá Region southwards. In four sites at latitudes from 20°S to 22°S, both lineages were found to coexist. Our study discovered for the first time the existence of the tropical lineage in Chile and demonstrated that distributions of the tropical and temperate lineages overlap, forming a transitional zone of approximately 200 km in northern coastal Chile.
Human seroepidemiology of Rickettsia and Orientia species in Chile – A crosssectional study in five regions
(2020) Weitzel, Thomas; Acosta-Jamett, Gerardo; Jiang, Ju; Martínez-Valdebenito, Constanza; Farris, Christina M.; Richards, Allen L.; Abarca, Katia
In recent years, the spectrum and epidemiology of human rickettsioses has become an emerging topic in Chile. This survey aimed to assess the seroprevalence of spotted fever group rickettsiae (SFGR), typhus group rickettsiae (TGR), and scrub typhus group orientiae (STGO) in northern, central, and southern Chile. We performed a cross-sectional study of healthy adults in rural and urban settings of five regions. Participants were chosen by double stratified random sampling in urban and by convenience in rural locations (n = 1302). Serum specimens were analyzed for group-specific IgG antibodies against SFGR, TGR, and STGO by enzyme-linked immunosorbent assays (ELISAs). Overall seroprevalences to SFGR, TGR, and STGO were 5.3 %, 1.2 %, and 0.4 %, respectively. Prevalences showed geographical differences. Statistical analyses revealed an association of older age with seropositivity to SFGR and to TGR and of rural setting and male gender with seropositivity to SFGR. The study indicates that SFGR, TGR, and STGO are endemic in Chile. The very low STGO seroprevalence might indicate an insufficient sensitivity of serological tests using Asian O. tsutsugamushi strains as ELISA antigens for the detection of antibodies against Chilean Orientia species.
Identification of trombiculid mites (Acari: Trombiculidae) on rodents from Chiloe´ Island and molecular evidence of infection with Orientia species
(2020) Acosta-Jamett, Gerardo; Martínez-Valdebenito, Constanza; Beltrami, Esperanza; Silva, María Carolina; Jiang, Ju; Richards, Allen L.; Weitzel, Thomas; Abarca, Katia
Background Scrub typhus is an emerging vector-borne zoonosis, caused by Orientia spp. and transmitted by larvae of trombiculid mites, called chiggers. It mainly occurs within a region of the Asia-Pacific called the tsutsugamushi triangle, where rodents are known as the most relevant hosts for the trombiculid vector. However, the reservoir(s) and vector(s) of the scrub typhus outside Asia-Pacific are unknown. The disease has recently been discovered on and is considered endemic for Chiloé Island in southern Chile. The aim of the present work was to detect and determine the prevalence of chiggers on different rodent species captured in probable sites for the transmission of orientiae responsible for scrub typhus on Chiloé Island in southern Chile and to molecularly examine collected chiggers for the presence of Orientia DNA. Methodology/Principal findings During the austral summer 2018, rodents were live-trapped in six sites and examined for chigger infestation. All study sites were rural areas on Chiloé Island, previously identified as probable localities where human cases acquired the scrub typhus. During a total of 4,713 trap-nights, 244 rodents of seven species were captured: the most abundant was Abrothrix olivacea. Chiggers were detected on all seven rodent species with a 55% prevalence rate. Chiggers showed low host specificity and varied according to site specific host abundance. Three genera of trombiculids were identified. Herpetacarus was the most abundant genus (93%), prevalent in five of the six sites. Infestation rates showed site specific differences, which were statistically significant using a GLM model with binomial errors. Molecular analyses proved that 21 of 133 (15.8%) mite pools were positive for Orientia species, all of them belonged to the genus Herpetacarus. Conclusions/Significance This study firstly reports the presence of different rodent-associated chigger mites positive for Orientia sp., in a region endemic for scrub typhus in southern Chile. Herpetacarus and two other genera of mites were found with high infestation rates of rodents in sites previously identified as probable exposure of scrub typhus cases. A substantial percentage of mite pools were positive for Orientia DNA, suggesting that chigger mites serve as vectors and reservoirs of this emerging zoonosis in South America. Author summary Scrub typhus is a chigger-transmitted zoonotic infection caused by Orientia species, which is endemic to the tsutsugamushi triangle in Asia-Pacific region. Recently, a focus of scrub typhus in South America has been confirmed on Chiloé Island in southern Chile. However, the vectors of scrub typhus in this region remain unknown. We undertook a survey to study the presence of chiggers on different rodent species in areas identified as probable sites of exposure to scrub typhus on Chiloé Island. The study showed that 55% of rodents were infested by trombiculids. Three mite genera were identified, of which Herpetacarus was the most abundant. Chiggers showed low host specificity, but spatial differences. Using molecular techniques, the trombiculid mites were found to be infected with Orientia species. These findings suggest that chigger mites play a role in the life cycle and transmission of this emerging infectious disease in Chile.
Imported scrub typhus: first case in South America and review of the literature
(2018) Weitzel, Thomas; Aylwin, Mabel; Martínez-Valdebenito, Constanza; Jiang, Ju; Munita, José; Thompson, Luis; Abarca, Katia; Richards, Allen L.
Background Scrub typhus is a neglected vector-borne zoonosis causing life-threatening illnesses, endemic in the Asian-Pacific region and, as recently discovered, in southern Chile. Scrub typhus is rarely reported in travelers, most probably due to the lack of clinical experience and diagnostic tests in non-endemic countries. We report the first case of imported scrub typhus in South America. Case presentation A 62-year-old tourist from South Korea presented severely ill with fever, rash, and eschar in Santiago, Chile. Laboratory exams showed thrombocytopenia and elevated inflammation parameters, hepatic enzymes, and LDH. With the clinical suspicion of scrub typhus, empirical treatment with doxycycline was initiated and the patient recovered rapidly and without complications. The diagnosis was confirmed by IgM serology and by real-time PCR, which demonstrated infection with Orientia tsutsugamushi (Kawasaki clade). Conclusions Only due to the emerging clinical experience with endemic South American scrub typhus and the recent implementation of appropriate diagnostic techniques in Chile, were we able to firstly identify and adequately manage a severe case of imported scrub typhus in South America. Physicians attending febrile travelers need to be aware of this rickettsiosis, since it requires prompt treatment with doxycycline to avoid complications.
Inactivated Vaccine-Induced SARS-CoV-2 Variant-Specific Immunity in Children
(2022) Soto, Jorge; Melo, Felipe; Gutierrez, Cristián; Schultz, Bárbara; Berríos, Roslye; Rivera, Daniela; Piña, Alejandro; Hoppe, Guillermo; Duarte, Luisa; Vázquez, Yaneisi; Moreno, Daniela; Ríos, Mariana; Palacios, Pablo; Garcia, Richard; Santibañez, Álvaro; Pacheco, Gaspar; Mendez, Constanza; Andrade, Catalina; Silva, Pedro; Diethelm, Benjamín; Astudillo, Patricio; Calvo, Mario; Cárdenas, Antonio; González, Marcela; Goldsack, Macarena; Gutiérrez, Valentina; Potin, Marcela; Schilling, Andrea; Tapia, Lorena; Twele, Loreto; Villena, Rodolfo; Grifoni, Alba; Sette, Alessandro; Weiskopf, Daniela; Fasce, Rodrigo; Fernández, Jorge; Mora, Judith; Ramírez, Eugenio; Gaete, Aracelly; Acevedo, Mónica; Valiente, Fernando; Soto, Ricardo; Retamal, Angello; Muñoz, Nathalia; PedCoronaVac03CL Study Group; Meng, Xing; Xin, Qianqian; Alarcón, Eduardo; González, José; Le Corre, Nicole; Álvarez, María; González, Pablo; Abarca, Katia; Perret, Cecilia; Carreño, Leandro; Bueno, Susan; Kalergisa, Alexis
Multiple vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been evaluated in clinical trials. However, trials addressing the immune response in the pediatric population are scarce. The inactivated vaccine CoronaVac has been shown to be safe and immunogenic in a phase 1/2 clinical trial in a pediatric cohort in China. Here, we report interim safety and immunogenicity results of a phase 3 clinical trial for CoronaVac in healthy children and adolescents in Chile. Participants 3 to 17 years old received two doses of CoronaVac in a 4-week interval until 31 December 2021. Local and systemic adverse reactions were registered for volunteers who received one or two doses of CoronaVac. Whole-blood samples were collected from a subgroup of 148 participants for humoral and cellular immunity analyses. The main adverse reaction reported after the first and second doses was pain at the injection site. Four weeks after the second dose, an increase in neutralizing antibody titer was observed in subjects relative to their baseline visit. Similar results were found for activation of specific CD4+ T cells. Neutralizing antibodies were identified against the Delta and Omicron variants. However, these titers were lower than those for the D614G strain. Importantly, comparable CD4+ T cell responses were detected against these variants of concern. Therefore, CoronaVac is safe and immunogenic in subjects 3 to 17 years old, inducing neutralizing antibody secretion and activating CD4+ T cells against SARS-CoV-2 and its variants. (This study has been registered at ClinicalTrials.gov under no. NCT04992260.) IMPORTANCE This work evaluated the immune response induced by two doses of CoronaVac separated by 4 weeks in healthy children and adolescents in Chile. To date, few studies have described the effects of CoronaVac in the pediatric population. Therefore, it is essential to generate knowledge regarding the protection of vaccines in this population. Along these lines, we reported the anti-S humoral response and cellular immune response to several SARS-CoV-2 proteins that have been published and recently studied. Here, we show that a vaccination schedule consisting of two doses separated by 4 weeks induces the secretion of neutralizing antibodies against SARS-CoV-2. Furthermore, CoronaVac induces the activation of CD4+ T cells upon stimulation with peptides from the proteome of SARS-CoV-2. These results indicate that, even though the neutralizing antibody response induced by vaccination decreases against the Delta and Omicron variants, the cellular response against these variants is comparable to the response against the ancestral strain D614G, even being significantly higher against Omicron.
Molecular Description of a Novel Orientia Species Causing Scrub Typhus in Chile
(2020-09) Abarca, Katia; Martínez-Valdebenito, Constanza; Angulo, Jenniffer; Jiang, Ju; Farris, Christina M.; Richards, Allen L.; Acosta-Jamett, Gerardo; Weitzel, Thomas
Scrub typhus is a potentially fatal rickettsiosis caused by Orientia species intracellular bacteria of the genus Orientia. Although considered to be restricted to the Asia Pacific region, scrub typhus has recently been discovered in southern Chile. We analyzed Orientia gene sequences of 16S rRNA (rrs) and 47-kDa (htrA) from 18 scrub typhus patients from Chile. Sequences were ≥99.7% identical among the samples for both amplified genes. Their diversity was 3.1%–3.5% for rrs and 11.2%–11.8% for htrA compared with O. tsusugamushi and 3.0% for rrs and 14.8% for htrA compared with Candidatus Orientia chuto. Phylogenetic analyses of both genes grouped the specimens from Chile in a different clade from other Orientia species. Our results indicate that Orientia isolates from Chile constitute a novel species, which, until they are cultivated and fully characterized, we propose to designate as Candidatus Orientia chiloensis, after the Chiloé Archipelago where the pathogen was identified.
Notes from the Field: Scrub Typhus Outbreak - Los Lagos Region, Chile, January-February 2023
(2023) Weitzel, Thomas; Martínez, Constanza; Acosta, Gerardo; Abarca, Katia
During January 14–February 14, 2023, a total of 36 cases of suspected scrub typhus were reported from the Los Lagos Region in southern Chile. Scrub typhus is a bacterial disease caused by one of three Orientia spp. and transmitted through bites from infected chiggers (larval mites).
Novel vector of scrub typhus in subantarctic Chile - evidence from human exposure
(2021) Weitzel, Thomas; Silva, María Carolina; Martínez, Constanza; Stekolnikov, Alexandr; Pérez, Caricia; Pérez, Ruth; Vial, Cecilia; Abarca, Katia; Acosta, Gerardo
The exposure of a research team to chigger mites in southern Chile allowed the first identification of a trombiculid species as vector and reservoir of scrub typhus outside the tsutsugamushi triangle, providing unique insights into the ecology and transmission of this recently discovered rickettsial infection in South America.
Prevalence and risk Factors for echinococcal infection in a rural area of northern Chile: A household-based cross-sectional study
(Public Library of Medical Science, 2014) Acosta-Jamett, Gerardo; Weitzel, Thomas; Boufana, Belgees; Adones, Claudia; Bahamonde, Andrea; Abarca, Katia; Craig, Philip; Reiter-Owona, Ingrid
Hydatidosis is a hyperendemic zoonotic disease in Chile caused by the dog tapeworm, Echinococcus granulosus. In Chile as in many other countries in South America, this disease has been largely neglected with few exceptions. Chile’s growing economy and the interest of health authorities has lead to an increase in the number of studies investigating the epidemiology of echinococcosis and the factors related to infections of the main definitive host, the domestic dog and humans. In this study, we determined the prevalence of human and canine echinococcosis as well as the associated risk factors in a rural area of the Limarı´ province in northern Chile. We undertook a household questionnaire survey in rural areas of the five municipalities of the Limarı´ province in Coquimbo region. For each household serum of an adult family member and fecal samples from a dog were taken. Results of our study indicate that infection occurs in 2.6% of humans and 28% of dogs and is primarily due to feeding of dogs with contaminated offal and high dog-human contact. As a result of this study, the Chilean Ministry of Health instigated a control program aimed to control the infection in dogs and avoid new infections to humans.
Prevalence and Risk Factors of Antibodies to Anaplasma spp. in Chile: A Household-Based Cross-Sectional Study in Healthy Adults and Domestic Dogs
(2020) Acosta-Jamett, Gerardo; Weitzel, Thomas; López, Javier; Alvarado, Doris; Abarca, Katia
Background: Pet-related tick-borne infections constitute an emerging problem in human and veterinary medicine worldwide. In Chile, two pathogens of the Anaplasmataceae family, Anaplasma platys and Ehrlichia canis, have been identified in recent years in dogs and vectors. This epidemiological survey aimed to determine the human and canine seroprevalence of Anaplasma spp. in urban and rural areas of different regions in Chile and to analyze the factors associated with seropositivity. Methods: We performed a cross-sectional household-based study in four regions, where healthy adults and their household dogs were included. Households were chosen by double stratified random sampling in urban areas and by convenience sampling in rural areas. Anaplasma seroreactivity was determined by a commercial microimmunofluorescence assay using Anaplasma phagocytophilum antigens. A questionnaire survey was applied to assess risk factors for Anaplasma seropositivity. Results: A total of 1105 persons and 905 dogs were included. The overall seroprevalence in humans was 9.4%, ranging from 5.6% in central Chile to 13.7% in the extreme north; in dogs the overall prevalence was 44.0% and ranged from 37.2% in the northern region to 61.1% in central Chile. Risk factors for human seropositivity were lower education and external deworming of dogs, whereas canine seropositivity was associated to urban site, mixed-breed, older animals, and tick infestation. Conclusions: This cross-sectional study suggests a broad exposure of both dogs and dog owners to Anaplasma or related agents in Chile. Further epidemiological and clinical studies are necessary to understand the complete spectrum and epidemiology of tick-borne zoonotic infections in the different ecoclimatic regions of Chile.
Safety and Immunogenicity of an Inactivated Severe Acute Respiratory Syndrome Coronavirus 2 Vaccine in a Subgroup of Healthy Adults in Chile
(2021) Bueno, Susan M.; Abarca, Katia; González, Pablo A.; Gálvez, Nicolás M. S.; Soto, Jorge A.; Duarte, Luisa F.; Schultz, Bárbara M.; Pacheco, Gaspar A.; González, Liliana A.; Vázquez, Yaneisi; Ríos, Mariana; Melo-González, Felipe; Rivera-Pérez, Daniela; Iturriaga, Carolina; Urzúa, Marcela; Domínguez, Angélica; Andrade, Catalina A.; Berríos-Rojas, Roslye V.; Canedo-Marroquín, Gisela; Covián, Camila; Moreno-Tapia, Daniela; Saavedra, Farides; Vallejos, Omar P.; Donato, Paulina; Espinoza, Pilar; Fuentes, Daniela; González, Marcela; Guzmán, Paula; Muñoz Venturelli, Paula; Pérez, Carlos M.; Potin, Marcela; Rojas, Álvaro; Fasce, Rodrigo A.; Fernández, Jorge; Mora, Judith; Ramírez, Eugenio; Gaete-Argel, Aracely; Oyarzún-Arrau, Aarón; Soto-Rifo, Ricardo; Weiskopf, Daniela; Sette, Alessandro; Zeng, Gang; Meng, Weining; González-Aramundiz, José V.; Kalergis, Alexis M.; CoronaVac03CL Study Group
Background. The development of effective vaccines against coronavirus disease 2019 is a global priority. CoronaVac is an inactivated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine with promising safety and immunogenicity profiles. This article reports safety and immunogenicity results obtained for healthy Chilean adults aged ≥18 years in a phase 3 clinical trial. Methods. Volunteers randomly received 2 doses of CoronaVac or placebo, separated by 2 weeks. A total of 434 volunteers were enrolled, 397 aged 18–59 years and 37 aged ≥60 years. Solicited and unsolicited adverse reactions were registered from all volun- teers. Blood samples were obtained from a subset of volunteers and analyzed for humoral and cellular measures of immunogenicity. Results. The primary adverse reaction in the 434 volunteers was pain at the injection site, with a higher incidence in the vaccine than in the placebo arm. Adverse reactions observed were mostly mild and local. No severe adverse events were reported. The humoral evaluation was performed on 81 volunteers. Seroconversion rates for specific anti-S1-receptor binding domain (RBD) immunoglobulin G (IgG) were 82.22% and 84.44% in the 18–59 year age group and 62.69% and 70.37% in the ≥60 year age group, 2 and 4 weeks after the second dose, respectively. A significant increase in circulating neutralizing antibodies was detected 2 and 4 weeks after the second dose. The cellular evaluation was performed on 47 volunteers. We detected a significant induction of T-cell responses characterized by the secretion of interferon-γ (IFN-γ) upon stimulation with Mega Pools of peptides from SARS-CoV-2. Conclusions. Immunization with CoronaVac in a 0–14 schedule in Chilean adults aged ≥18 years is safe, induces anti-S1-RBD IgG with neutralizing capacity, activates T cells, and promotes the secretion of IFN-γ upon stimulation with SARS-CoV-2 antigens.
Safety and Non-Inferiority Evaluation of Two Immunization Schedules with an Inactivated SARS-CoV-2 Vaccine in Adults: A Randomized Clinical Trial
(2022) Abarca, Katia; Iturriaga, Carolina; Urzúa, Marcela; Le Corre, Nicole; Pineda, Augusto; Fernández, Carolina; Domínguez, Angélica; González, Pablo; Bueno, Susan; Donato, Paulina; Espinoza, Pilar; Fuentes, Daniela; González, Marcela; Guzmán, Paula; Muñoz Venturelli, Paula; Pérez, Carlos; Potin, Marcela; Rojas, Álvaro; González, José; Gálvez, Nicolás; Aguirre, Francisca; Aljaro, Sofía; Bátiz, Luis; Campisto, Yessica; Cepeda, Mariela; Cortés, Aarón; López, Sofía; Pérez, María; Schilling, Andrea; Kalergis, Alexis; On behalf of the CoronaVac CL Study Group
Several vaccines have been developed to control the COVID-19 pandemic. CoronaVac®, an inactivated SARS-CoV-2 vaccine, has demonstrated safety and immunogenicity, preventing severe COVID-19 cases. We investigate the safety and non-inferiority of two immunization schedules of CoronaVac® in a non-inferiority trial in healthy adults. A total of 2302 healthy adults were enrolled at 8 centers in Chile and randomly assigned to two vaccination schedules, receiving two doses with either 14 or 28 days between each. The primary safety and efficacy endpoints were solicited adverse events (AEs) within 7 days of each dose, and comparing the number of cases of SARS-CoV-2 infection 14 days after the second dose between the schedules, respectively. The most frequent local AE was pain at the injection site, which was less frequent in participants aged ≥60 years. Other local AEs were reported in less than 5% of participants. The most frequent systemic AEs were headache, fatigue, and myalgia. Most AEs were mild and transient. There were no significant differences for local and systemic AEs between schedules. A total of 58 COVID-19 cases were confirmed, and all but 2 of them were mild. No differences were observed in the proportion of COVID-19 cases between schedules. CoronaVac® is safe, especially in ≥60-year-old participants. Both schedules protected against COVID-19 hospitalization.
Scrub Typhus in Continental Chile, 2016-2018 1
(National Center for Infectious Diseases, 2019) Weitzel, Thomas; Martínez-Valdebenito, Constanza; Acosta-Jamett, Gerardo; Jiang, Ju; Richards, Allen; Abarca, Katia
Endemic scrub typhus was recently detected on Chiloé Island in southern Chile. We report a series of cases, acquired over a wide geographical range in continental Chile during 2016-2018, demonstrating that this emerging rickettsial infection is also found on the mainland of South America.

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