Viral shedding and viraemia of Andes virus during acute hantavirus infection: a prospective study

BACKGROUND

Andes virus (ANDV) is a zoonotic Orthohantavirus leading to hantavirus cardiopulmonary syndrome. Although most transmissions occur through environmental exposure to rodent faeces and urine, rare person-to-person transmission has been documented, mainly for close contacts. This study investigates the presence and infectivity of ANDV in body fluids from confirmed cases and the duration of viraemia.

METHODS

In this prospective study, 131 participants with confirmed ANDV infection were enrolled in Chile in a prospective study between 2008 and 2022. Clinical samples (buffy coat, plasma, gingival crevicular fluid [GCF], saliva, nasopharyngeal swabs [NPS], and urine) were collected weekly for 3 weeks together with clinical and epidemiological data. Samples were categorised as acute or convalescent (up to and after 16 days following onset of symptoms). Infectivity of positive fluids was assessed after the culture of samples on Vero E6 cells and use of flow cytometry assays to determine the production of ANDV nucleoprotein.

FINDINGS

ANDV RNA was detected in 100% of buffy coats during acute phase, declining to 95% by day 17, and to 93% between days 23-29. ANDV RNA in GCF and saliva decreased from 30% and 12%, respectively, during the acute phase, to 12% and 11% during the convalescent phase. Successful infectivity assays of RT-qPCR-positive fluids, including GCF, saliva, NPS, and urine, were observed in 18 (42%) of 43 samples obtained during the acute phase of infection. After re-culture, the capacity to infect Vero E6 cells was maintained in 16 (89%) of 18 samples. Severity was associated with the presence of ANDV RNA in one or more fluids besides blood (odds ratio 2·58 [95% CI 1·42-5·18]).

INTERPRETATION

ANDV infection is a systemic and viraemic infection, that affects various organs. The presence of infectious particles in body fluids contributes to our understanding of potential mechanisms for person-to-person transmission, supporting the development of preventive strategies. Detection of ANDV RNA in additional fluids at hospital admission is a predictor of disease severity.

FUNDING

None.

TRANSLATION

For the Spanish translation of the abstract see Supplementary Materials section.

Monkeypox Virus in Wastewater Samples from Santiago Metropolitan Region, Chile

Sewage surveillance provides useful epidemiologic and public health information on viral infections at the population level. We detected monkeypox virus DNA from sewage samples covering 85% of the population in Santiago Metropolitan Region Chile. We also isolated infective viruses from those samples. Wastewater surveillance could complement clinical surveillance for monkeypox virus.

Influence of SARS-CoV-2 mRNA Vaccine Booster among Cancer Patients on Active Treatment Previously Immunized with Inactivated versus mRNA Vaccines: A Prospective Cohort Study

Cancer patients on chemotherapy have a lower immune response to SARS-CoV-2 vaccines. Therefore, through a prospective cohort study of patients with solid tumors receiving chemotherapy, we aimed to determine the immunogenicity of an mRNA vaccine booster (BNT162b2) among patients previously immunized with an inactivated (CoronaVac) or homologous (BNT162b2) SARS-CoV-2 vaccine. The primary outcome was the proportion of patients with anti-SARS-CoV-2 neutralizing antibody (NAb) seropositivity at 8-12 weeks post-booster. The secondary end points included IgG antibody (TAb) seropositivity and specific T-cell responses. A total of 109 patients were included. Eighty-four (77%) had heterologous vaccine schedules (two doses of CoronaVac followed by the BNT162b2 booster) and twenty-five had (23%) homologous vaccine schedules (three doses of BNT162b2). IgG antibody positivity for the homologous and heterologous regimen were 100% and 96% (p = 0.338), whereas NAb positivity reached 100% and 92% (p = 0.13), respectively. Absolute NAb positivity and Tab levels were associated with the homologous schedule (with a beta coefficient of 0.26 with p = 0.027 and a geometric mean ratio 1.41 with p = 0.044, respectively). Both the homologous and heterologous vaccine regimens elicited a strong humoral and cellular response after the BNT162b2 booster. The homologous regimen was associated with higher NAb positivity and Tab levels after adjusting for relevant covariates.

Eco-epidemiology of rodent-associated trombiculid mites and infection with Orientia spp. in Southern Chile

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.

Development of a New Genus-Specific Quantitative Real-Time PCR Assay for the Diagnosis of Scrub Typhus in South America

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.

Differential neutralizing antibody responses elicited by CoronaVac and BNT162b2 against SARS-CoV-2 Lambda in Chile

SARS-CoV-2 variant Lambda was dominant in several South American countries, including Chile. To ascertain the efficacy of local vaccination efforts, we used pseudotyped viruses to characterize the neutralization capacity of antibodies elicited by CoronaVac (n = 53) and BNT162b2 (n = 56) in healthcare workers from Clínica Santa María and the Faculty of Medicine at Universidad de Chile, as well as in convalescent plasma from individuals infected during the first wave visiting the Hospital Clínico at Pontificia Universidad Católica (n = 30). We observed that BNT162b2 elicits higher neutralizing antibody titres than CoronaVac, with differences ranging from 7.4-fold for the ancestral spike (Wuhan-Hu-1) to 8.2-fold for the Lambda spike and 13-fold for the Delta spike. Compared with the ancestral virus, neutralization against D614G, Alpha, Gamma, Lambda and Delta variants was reduced by between 0.93- and 4.22-fold for CoronaVac, 1.04- and 2.38-fold for BNT162b2, and 1.26- and 2.67-fold for convalescent plasma. Comparative analyses among the spike structures of the different variants suggest that mutations in the spike protein from the Lambda variant, including the 246-252 deletion in an antigenic supersite at the N-terminal domain loop and L452Q/F490S within the receptor-binding domain, may account for immune escape. Interestingly, analyses using pseudotyped and whole viruses showed increased entry rates into HEK293T-ACE2 cells, but reduced replication rates in Vero-E6 cells for the Lambda variant when compared with the Alpha, Gamma and Delta variants. Our data show that inactivated virus and messenger RNA vaccines elicit different levels of neutralizing antibodies with different potency to neutralize SARS-CoV-2 variants, including the variant of interest Lambda.

Relevance of codetection of respiratory viruses in the severity of acute respiratory infection in hospitalized children

INTRODUCTION

Multiplex polymerase chain reaction (PCR) allows simultaneous detection of respiratory viruses, raising questions about their relevance in the clinical feature.

OBJECTIVE

To evaluate the contribution of clinical, epidemiological, and virological factors in the clinical course of children hospitalized due to ARI with viral co-detection.

PATIENTS AND METHOD

Pediatric patients ≤ 15 years old, hospitalized due to ARI at the UC-CHRISTUS Health Network Clinical Hospital between June and October 2014, and who presented a positive respiratory molecular panel test, were included. Respiratory samples (nasopharyngeal swab, tracheal aspiration, or bronchoalveolar lavage) with positive panel tests by Seeplex® RV15 OneStep ACE Detection Seegene® technique, were analyzed with a second technique (xTAG-RVP-FASTv2 Luminex®, USA), which allows simultaneous and semi-quantitative detection of 17 respiratory viruses. Clinical and epidemiological records were collected.

RESULTS

One virus was identified in 42/57 children (74%) and two or more in 15/57 (26%). Intensive care unit (ICU) hospi talization was significantly more frequent in patients with viral co-detection (OR = 5,5; IC 95%: 1,5 19,6). The most frequently detected viruses were rhinovirus/enterovirus (HRV/EV) (29%) and res piratory syncytial virus (RSV) (25%), and the most common co-detection was HRV/EV-RSV (33%). In x-rays, patients with HRV/EV infection presented interstitial images more frequently, while RSV was associated with condensations (p = 0.002). For HRV/EV, median fluorescence intensity (MFI, semi-quantification) were 1788 and 2456 in co-detection and single agent, respectively (p = 0.022). Children with HRV/EV co-detection had a longer hospital stay compared to isolated identification (5 versus 3 days, p = 0,028).

CONCLUSION

In children hospitalized due to ARI, viral co-detection is frequent and associated with more ICU hospitalizations. Our study highlights the presence of HRV/ EV in viral co-detection and longer length of stay. More studies are needed to define the relevance of viral co-detection in hospitalized pediatric patients.

Novel vector of scrub typhus in subantarctic Chile - evidence from human exposure

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.

Molecular Description of a Novel Orientia Species Causing Scrub Typhus in Chile

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.

Mother-to-Child Transmission of Andes Virus through Breast Milk, Chile1

Andes virus (ANDV) is the only hantavirus transmitted between humans through close contact. We detected the genome and proteins of ANDV in breast milk cells from an infected mother in Chile who transmitted the virus to her child, suggesting gastrointestinal infection through breast milk as a route of ANDV person-to-person transmission.

Chigger Mites (Acariformes: Trombiculidae) of Chiloé Island, Chile, With Descriptions of Two New Species and New Data on the Genus Herpetacarus

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 goffiStekolnikov 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 ProschoengastiaVercammen-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.

Early versus deferred anti-SARS-CoV-2 convalescent plasma in patients admitted for COVID-19: A randomized phase II clinical trial

BACKGROUND

Convalescent plasma (CP), despite limited evidence on its efficacy, is being widely used as a compassionate therapy for hospitalized patients with COVID-19. We aimed to evaluate the efficacy and safety of early CP therapy in COVID-19 progression.

METHODS AND FINDINGS

The study was an open-label, single-center randomized clinical trial performed in an academic medical center in Santiago, Chile, from May 10, 2020, to July 18, 2020, with final follow-up until August 17, 2020. The trial included patients hospitalized within the first 7 days of COVID-19 symptom onset, presenting risk factors for illness progression and not on mechanical ventilation. The intervention consisted of immediate CP (early plasma group) versus no CP unless developing prespecified criteria of deterioration (deferred plasma group). Additional standard treatment was allowed in both arms. The primary outcome was a composite of mechanical ventilation, hospitalization for >14 days, or death. The key secondary outcomes included time to respiratory failure, days of mechanical ventilation, hospital length of stay, mortality at 30 days, and SARS-CoV-2 real-time PCR clearance rate. Of 58 randomized patients (mean age, 65.8 years; 50% male), 57 (98.3%) completed the trial. A total of 13 (43.3%) participants from the deferred group received plasma based on clinical aggravation. We failed to find benefit in the primary outcome (32.1% versus 33.3%, odds ratio [OR] 0.95, 95% CI 0.32-2.84, p > 0.999) in the early versus deferred CP group. The in-hospital mortality rate was 17.9% versus 6.7% (OR 3.04, 95% CI 0.54-17.17 p = 0.246), mechanical ventilation 17.9% versus 6.7% (OR 3.04, 95% CI 0.54-17.17, p = 0.246), and prolonged hospitalization 21.4% versus 30.0% (OR 0.64, 95% CI, 0.19-2.10, p = 0.554) in the early versus deferred CP group, respectively. The viral clearance rate on day 3 (26% versus 8%, p = 0.204) and day 7 (38% versus 19%, p = 0.374) did not differ between groups. Two patients experienced serious adverse events within 6 hours after plasma transfusion. The main limitation of this study is the lack of statistical power to detect a smaller but clinically relevant therapeutic effect of CP, as well as not having confirmed neutralizing antibodies in donor before plasma infusion.

CONCLUSIONS

In the present study, we failed to find evidence of benefit in mortality, length of hospitalization, or mechanical ventilation requirement by immediate addition of CP therapy in the early stages of COVID-19 compared to its use only in case of patient deterioration.

TRIAL REGISTRATION

NCT04375098.

Insights into neutralizing antibody responses in individuals exposed to SARS-CoV-2 in Chile

Chile has one of the worst numbers worldwide in terms of SARS-CoV-2 positive cases and COVID-19-related deaths per million inhabitants; thus, characterization of neutralizing antibody (NAb) responses in the general population is critical to understanding of immunity at the local level. Given our inability to perform massive classical neutralization assays due to the scarce availability of BSL-3 facilities in the country, we developed and fully characterized an HIV-based SARS-CoV-2 pseudotype, which was used in a 96-well plate format to investigate NAb responses in samples from individuals exposed to SARS-CoV-2 or treated with convalescent plasma. We also identified samples with decreased or enhanced neutralization activity against the D614G spike variant compared with the wild type, indicating the relevance of this variant in host immunity. The data presented here represent the first insights into NAb responses in individuals from Chile, serving as a guide for future studies in the country.

[Humoral immune response induced by influenza vaccine in children with acute lymphoblastic leukemia]

BACKGROUND

Patients with acute lymphoblastic leukemia (ALL) have high risk of severe influenza infection and vaccination is highly recommended. The immunogenicity and effectiveness of vaccination are lower than in healthy people.

AIM

To evaluate the immune response induced by influenza vaccine in children with ALL and observe effectiveness.

METHOD

Children with ALL in maintenance phase and healthy children were recruited. Blood samples were taken at vaccination day (D0) and at day 28 (D28). Humoral response was evaluated by hemaglutination inhibition test (HAI) against H1N1. Patients were followed up for one year, clinical data and influenza episodes were recorded.

RESULTS

34 children with ALL and 9 healthy children were included. Concerning HAI on D28, 12/34 patients and 5/8 healthy children had titers ≥ 1/40, with seroprotection rates of 35 and 63% respectively. Seroprotected children were older than non-seroprotected ones. During follow-up, only 3 patients non seroprotected, presented influenza infection, without oxygen supplementation or critical care support.

DISCUSSION

Children with ALL had a lower seroprotection rate than healthy children. Nevertheless, none of the seroprotected children presented influenza infection, reinforcing the annual vaccination recommendation.

Human seroepidemiology of Rickettsia and Orientia species in Chile - A cross-sectional study in five regions

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 Chiloé Island and molecular evidence of infection with Orientia species

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.

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.

A 19 Year Analysis of Small Mammals Associated with Human Hantavirus Cases in Chile

Small mammals present in areas where hantavirus cardiopulmonary syndrome (HCPS) cases had occurred in central and southern Chile were captured and analyzed to evaluate the abundance of rodents and seroprevalence rates of antibodies to Andes orthohantavirus (ANDV). Sampling areas ranged from the Coquimbo to Aysén regions (30–45° S approx.) regions. Ninety-two sites in peridomestic and countryside areas were evaluated in 19 years of sampling. An antibody against ANDV was detected by strip immunoassay in 58 of 1847 specimens captured using Sherman traps. Of the eleven species of rodents sampled, Abrothrix olivacea, Oligoryzomys longicaudatus and Abrothrix hirta were the most frequently trapped. O. longicaudatus had the highest seropositivity rate, and by logistic regression analysis, O. longicaudatus of at least 60 g had 80% or higher probability to be seropositive. Sex, age and wounds were significantly related to seropositivity only for O. longicaudatus. Across administrative regions, the highest seropositivity was found in the El Maule region (34.8–36.2° S), and the highest number of HCPS cases was registered in the Aysén region. Our results highlight the importance of long term and geographically extended studies, particularly for highly fluctuating pathogens and their reservoirs, to understand the implications of the dynamics and transmission of zoonotic diseases in human populations.

[Scrub typhus, an emerging infectious disease in Chile]

Scrub typhus, caused by Orientia tsutsugamushi and transmitted by larvae of trombiculid mites, is an endemic rickettsiosis in the Asia Pacific region. After the first identification of a case in Chile in 2006, more than 30 cases have been diagnosed by our group since 2015. Cases were detected predominantly during the Chilean summer months. Patients presented with fever, rash, and a typical eschar at the inoculation site; other frequent findings were intense headache, night sweats, increased laboratory markers of inflammation and transaminases. The vast majority of cases have been diagnosed in southern Chile (mainly Chiloé Island), although recently some cases were also identified in the central Metropolitan Region in patients returning from trips to southern Chile. Physicians attending Chilean patients should be aware of this emerging infection to be able to initiate empirical therapy with doxycycline. The confirmation of cases by the diagnostic methods available in Chile will contribute to a better understanding of the epidemiological and clinical relevance of this emerging infection in South America.

Scrub Typhus in Continental Chile, 2016-20181

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.

A Single-Nucleotide Polymorphism of αVβ₃ Integrin Is Associated with the Andes Virus Infection Susceptibility

The AndesOrthohantavirus (ANDV), which causes the hantavirus cardiopulmonary syndrome, enters cells via integrins, and a change from leucine to proline at residue 33 in the PSI domain (L33P), impairs ANDV recognition. We assessed the association between this human polymorphism and ANDV infection. We defined susceptible and protective genotypes as “TT” (coding leucine) and “CC” (coding proline), respectively. TT was present at a rate of 89.2% (66/74) among the first cohort of ANDV cases and at 60% (63/105) among exposed close-household contacts, who remained uninfected (p < 0.05). The protective genotype (CC) was absent in all 85 ANDV cases, in both cohorts, and was present at 11.4% of the exposed close-household contacts who remained uninfected. Logistic regression modeling for risk of infection had an OR of 6.2–12.6 (p < 0.05) in the presence of TT and well-known ANDV risk activities. Moreover, an OR of 7.3 was obtained when the TT condition was analyzed for two groups exposed to the same environmental risk. Host genetic background was found to have an important role in ANDV infection susceptibility, in the studied population.

Imported scrub typhus: first case in South America and review of the literature

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.

Canine seroprevalence to Orientia species in southern Chile: A cross-sectional survey on the Chiloé Island

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.

[Parotiditis in Chile: clinical and molecular characterization of two cases in a highly vaccinated population]

Mumps virus usually produces a benign infection characterized by increased parotid volume which, prior to vaccination, mainly affected children and adolescents. After the introduction of measles, mumps and rubella (MMR) vaccine, mumps incidence decreased dramatically. This intervention also produced a change in its clinical presentation, moving to young adult patients, with an increased risk of complications. We report two clinical mumps cases in young adults with different clinical presentations. In both cases, serologic assays were assessed and, in one case, a polymerase chain reaction (PCR) was performed in order to confirm the diagnosis. The isolated virus was characterized and identifed as G genotype, the same genotype observed during outbreaks in United States and Europe, and different to the vaccinal strain. Mumps virus is currently circulating in Chile and it is important to be aware of possible outbreaks. Viral diagnosis can be difficult, particularly in populations with high vaccination coverage. Therefore, the access to etiologic study through PCR and serology becomes more relevant in order to optimize clinical management and secondary prevention measures.

Serum levels of interleukin-6 are linked to the severity of the disease caused by Andes Virus

Andes virus (ANDV) is the etiological agent of hantavirus cardiopulmonary syndrome in Chile. In this study, we evaluated the profile of the pro-inflammatory cytokines IL-1β, IL-12p70, IL-21, TNF-α, IFN-γ, IL-10 and IL-6 in serum samples of ANDV-infected patients at the time of hospitalization. The mean levels of circulating cytokines were determined by a Bead-Based Multiplex assay coupled with Luminex detection technology, in order to compare 43 serum samples of healthy controls and 43 samples of ANDV-infected patients that had been categorized according to the severity of disease. When compared to the controls, no significant differences in IL-1β concentration were observed in ANDV-infected patients (p = 0.9672), whereas levels of IL-12p70 and IL-21 were significantly lower in infected cases (p = <0.0001). Significantly elevated levels of TNF-α, IFN-γ, IL-10, and IL-6 were detected in ANDV-infected individuals (p = <0.0001, 0.0036, <0.0001, <0.0001, respectively). Notably, IL-6 levels were significantly higher (40-fold) in the 22 patients with severe symptoms compared to the 21 individuals with mild symptoms (p = <0.0001). Using multivariate regression models, we show that IL-6 levels has a crude OR of 14.4 (CI: 3.3–63.1). In conclusion, the serum level of IL-6 is a significant predictor of the severity of the clinical outcome of ANDV-induced disease.

Andes virus (ANDV) causes hantavirus cardiopulmonary syndrome (HCPS) that is characterized by the development of vascular leakage syndrome, eventually leading to massive pulmonary edema, shock and, in many cases, death. To date, no FDA-approved immunotherapeutics, specific antivirals, or vaccines are available for use against HCPS. Patient survival rates hinge largely on early virus diagnosis, hospital admission and aggressive pulmonary and hemodynamic support in an intensive care unit. Individual host factors associated with the outcome of an ANDV infection are poorly known, and such knowledge could allow the disease progression of hospitalized patients to be predicted, resulting in individualized treatment. In this study, we show that serum levels of IL-6 at the time of hospitalization in ANDV-infected patients are associated with the severity of the clinical outcome of ANDV-induced disease. Therefore, these finding suggest that determining IL-6 levels at the time of admission to the hospital could be useful to predict the progression of ANDV-induced disease.

Fleas and Ticks in Carnivores From a Domestic-Wildlife Interface: Implications for Public Health and Wildlife

Fleas and ticks are parasites of wild and domestic mammals, and can be vectors of several pathogens. In rural areas, domestic carnivores such as the domestic dog (Canis lupus familiaris L.), may act as a "bridge" between natural areas and human settlements where ectoparasites can be used as a metric of such link. The aim of this study was to identify fleas, ticks, and Rickettsia spp., collected from domestic and wild carnivores in a natural reserve and surrounding human settlements in Central Chile, using morphological keys and molecular analysis. We surveyed 170 households from which 107 dogs and eight cats were sampled. From the natural reserve, we sampled two chilla foxes (Pseudalopex griseus Gray), two lesser grison (Galictis cuja Molina), three kodkods (Leopardus guigna Molina), and four dogs. From dogs, we collected Ctenocephalides felis Bouché, Ctenocephalides canis Curtis, Pulex irritans L., and Rhipicephalus sanguineus s.l. Latreille; C. felis was the most frequent ectoparasite. Cats were infested only by C. felis and Rh. sanguineus s.l. From wild carnivores, we obtained C. canis and P. irritans, the latter being most frequent. Molecular analysis of P. irritans detected 10 haplotypes and two main clades, which tended to separate fleas from wild and domestic hosts. Molecular analysis of ompA and ompB genes confirmed the presence of Rickettsia felis in fleas collected from owned dogs and cats, which could represent a potential risk factor of R. felis transmission in the area.

Association of Single-Nucleotide Polymorphisms in IL28B, but Not TNF-α, With Severity of Disease Caused by Andes Virus

BACKGROUND

Andes virus (ANDV) is the sole etiologic agent of hantavirus cardiopulmonary syndrome (HCPS) in Chile, with a fatality rate of about 35%. Individual host factors affecting ANDV infection outcome are poorly understood. In this case-control genetic association analysis, we explored the link between single-nucleotide polymorphisms (SNPs) rs12979860, rs8099917 and rs1800629 and the clinical outcome of ANDV-induced disease. The SNPs rs12979860 and rs8099917 are known to play a role in the differential expression of the interleukin 28B gene (IL28B), whereas SNP rs1800629 is implicated in the expression of tumor necrosis factor α gene (TNF-α).

METHODS

A total of 238 samples from confirmed ANDV-infected patients collected between 2006 and 2014, and categorized according to the severity of the disease, were genotyped for SNPs rs12979860, rs8099917, and rs1800629.

RESULTS

Analysis of IL28B SNPs rs12979860 and rs8099917 revealed a link between homozygosity of the minor alleles (TT and GG, respectively), displaying a mild disease progression, whereas heterozygosity or homozygosity for the major alleles (CT/CC and TG/TT, respectively) in both IL28B SNPs is associated with severe disease. No association with the clinical outcome of HCPS was observed for TNF-α SNP rs1800629 (TNF -308G>A).

CONCLUSIONS

The IL28B SNPs rs12979860 and rs8099917, but not TNF-α SNP rs1800629, are associated with the clinical outcome of ANDV-induced disease, suggesting a possible link between IL28B expression and ANDV pathogenesis.