Gerardo Acosta-Jamett

Universidad Austral de Chile · Instituto de Medicina Preventiva Veterinaria

Candidatus Orientia chiloensis causes scrub typhus over a wide geographical range in southern Chile. The life cycle, including vectors and reservoirs of this novel rickettsial pathogen, is incompletely understood. We analyzed rodent tissue and rodent-associated mite samples collected during a field study in six localities on Chiloé Island, where hu...

Although a lack of diversity in genetic studies is an acknowledged obstacle for personalized medicine and precision public health, Latin American populations remain particularly understudied despite their heterogeneity and mixed ancestry. This gap extends to COVID-19 despite its variability in susceptibility and clinical course, where ethnic backgr...

Host genetic variability can modulate infection resistance, although its role in infection clearance remains unclear. Hookworm disease (Uncinaria sp.) is the leading cause of pup mortality in several otariid species, although the parasite can be cleared through immune-mediated processes. We evaluated the association of host genetic diversity, body...

Wild rodents often harbor Cryptosporidium species that can be transmitted to multiple mammal hosts. In Chile, little is known about Cryptosporidium in wild rodents, and available studies have been focused on morphological findings with no molecular-based evidence. A longitudinal survey was conducted between 2021 and 2022 to investigate the occurren...

Mammals in drylands face environmental challenges exacerbated by climate change. Currently, human activity significantly impacts these environments, and its effects on the energy demands experienced by individuals have not yet been determined. Energy demand in organisms is managed through elevations in glucocorticoid levels, which also vary with de...

Humans are rapidly transforming whole ecosystems by deforestation, habitat fragmentation, pollution, and climate change, among others. Increased human populations and the transformation of original habitats to productive lands have led to increased contact between humans, domestic animals, and wildlife. Although the maintenance and circulation of p...

Neotropical environments are currently under constant and increasing anthropogenic pressure, transforming landscapes and the communities of species that use them. This undoubtedly favors changes in the patterns of interaction between components of infectious disease systems. In addition, it reduces the contact gap between humans and their domestic...

In Chile, selling cattle through auction markets is common, and involves various stressful events. The objective of this study was to determine the effects of selling weaned beef calves through an auction market on indicators of physiological stress. Considering that transportation is invariably linked to any commercialization procedure, we compare...

PURPOSE: Molecular mechanisms underlying COVID-19 susceptibility and severity are still poorly understood. The presence of genetic risk factors associated with ethnic background has been suggested, highlighting non-European ancestry as a risk factor for hospitalization in the United States. However, the representation of non-European populations in...

The tick Amblyomma tigrinum inhabits areas with diverse climatic conditions, with adult stages parasitizing wild canids, such as chilla (Lycalopex griseus) and culpeo (Lycalopex culpaeus) foxes. We described the infestation loads in wild foxes captured at three sites (periurban, rural and wild) through an anthropization gradient in north-central Ch...

The divergence between the Andean fox (Lycalopex culpaeus) and the South American gray fox (L. griseus) represents a recent speciation event in South America. These taxa are partially sympatric and share biological, morphological, and ecological traits. Previous studies failed to recover reciprocal monophyly, suggesting the occurrence of introgress...

Despite the extensive information on the effects of habitat alteration on the structure of helminth communities in small mammals, the evidence is still inconclusive. A systematic review was carried out using the PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analysis) guideline to compile and synthesize available literature on the...

The main objective of this study was to estimate the performance, under local epidemiological conditions, of two in-house ELISA assays for the combined detection of anti-SARS-CoV-2 IgA, IgM, and IgG immunoglobulins. A total of 94 serum samples were used for the assessment, where 44 corresponded to sera collected before the pandemic (free of SARS-Co...

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 regi...

Adult individuals of Amblyomma tigrinum were collected for the first time from a Molina’s hog-nosed skunk (Conepatus chinga), captured in a rural area of north-central Chile, which were described and identified morphologically. There are scarce studies that address the role of the skunk as ectoparasite host; however, the great plasticity of A. tigr...

Our goal was to assess whether free-ranging foxes have been exposed to canine distemper virus (CDV) in the Araucanía region in Chile. The study was conducted at three sites in rural areas where free-ranging foxes were trapped and bled from 2009 to 2012. We sampled two species of foxes: the culpeo (Lycalopex culpaeus) (n=13) and the chilla (Lycalope...

Gastrointestinal parasites are well-documented in small mammals from north-central Chile, but little is known about endoparasites of rodents in southern Chile. A survey was conducted between January and February 2018 to evaluate gastrointestinal parasites and risk factors of wild rodents that live in rural areas in Northern Chiloé Island, Chile. A...

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....

Chile is a large country with a marked range of climate conditions that make it an ideal scenario for the study of vector-borne parasites; however, knowledge about their distribution is limited to a few confined areas of this country. The presence of Hepatozoon spp., piroplasmids, Leishmania spp. and filarioids was investigated through molecular an...

Background: A series of abiotic and biotic modifications occur in an anthropogenic landscape which influence the ecology and physiology of wild hosts and their parasites. How these changes affect the parasitism is highly context-dependent, based on the host-parasite system and the type of perturbation. We aimed to investigate the differences in inf...

Background Cystic echinococcosis (CE) caused by Echinococcus granulosus sensu lato (s.l.) is a neglected and underdiagnosed parasitic zoonosis that has a significant socioeconomic impact on rural communities relying on livestock farming. CE is endemic across Latin America, including Chile, where the Coquimbo region exhibits a relatively high record...

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.

Anaplasma platys and Ehrlichia canis are members of the Anaplasmataceae family that cause disease in dogs and are mainly transmitted by Rhipicephalus sanguineus species group ticks. We performed a cross-sectional study on these pathogens across six bioclimatic regions of Chile, including 719 free-ranging rural dogs, 132 Andean foxes (Lycalopex culp...

The genetic diversity of populations is the basis for individual fitness and potential adaptability to environmental changes. The South American fur seal (Arctocephalus australis) is a pinniped species that is widely distributed along the southern cone of South America. However, two distinct populations have evolved: the Northern Pacific/Peruvian p...

Trichinellosis is a zoonosis with worldwide distribution. Several hosts have been recognized around the world; however, there is a lack of knowledge of the role of feral mammals in Chile in its transmission. Herein, we tested muscle samples from 555 individuals among American minks (Neovison vison Schreber, 1777. n = 100) and several myomorph roden...

Blood samples of 626 rural dogs, 139 Andean foxes (Lycalopex culpaeus), and 83 South American grey foxes (L. griseus) from six bioregions of Chile spanning 3,000 km. were screened for Mycoplasma DNA by conventional PCR and sequencing. Risk factors of infection were inferred using GLMMs and genetic structure by network analyses. Overall, M. haemocan...

Domestic dogs (Canis familiaris) often cohabite at interfaces shared by humans and wildlife, interacting with wild canids as predators, prey, competitors and reservoirs of several multi-host pathogens, such as canid-borne micro and macro parasites that could impact on wildlife, livestock and public health. However, spatio-temporal patterns of indir...

Trichinellosis is a worldwide disease that is considered emerging and neglected. Several hosts have been recognized around the world, however, there is a lack of knowledge of the role of free-range mammals in Chile. Herein we examined 555 individuals among American minks (Neovison vison Schreber, 1777. n = 100) and several myomorph rodent species (...

The aim of this experiment was to determine if the provision of straw and the presence of undocked twins could be used to mitigate the pain experienced by lambs having their tails docked using rubber rings. A total of 54 twin St. Croix 60-days-old weaned lambs were assigned to one of four treatments: (i) the presence of undocked twins and no provis...

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 Ste...

Cystic echinococcosis (CE) is a parasitic zoonosis, caused by the larval stage of Echinococcus granulosus. This disease has a worldwide distribution and is considered an important zoonosis in Chile, especially in regions where raising livestock dominates. We aimed to describe the spatial distribution and risk factors for CE in cattle and sheep slau...

Scrub typhus is a potentially severe tropical rickettsiosis, which is known for centuries in the Asia Pacific region, where it threatens >1 billion people, causing significant morbidity and mortality [ 1 ]. In recent years, however, scrub typhus caused by a distinct Orientia species has been discovered in various regions of Chile [ 2 , 3 ]. Here we...

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...

Simple Summary: Feline gurltiosis is a parasitic myelopathy caused by Gurltia paralysans. This nematode infects domestic cats without distinction of sex, breed or age, invading the venous system of the spinal leptomeninges and causing vascular congestion that mainly produces paralysis of the pelvic limbs, among other clinical signs of chronic myelo...

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...

Effective interventions are mandatory to control the transmission and spread of SARS-CoV-2, a highly contagious virus causing devastating effects worldwide. Cost-effective approaches are pivotal tools required to increase the detection rates and escalate further in massive surveillance programs, especially in countries with limited resources that m...

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 seropreval...

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 ve...

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.

Cystic echinococcosis (CE) is a zoonotic parasitic disease associated with Echinococcus granulosus. The parasite is maintained by domestic and wild canids as definitive hosts with several ungulate species as intermediate hosts in domestic and peridomestic transmission cycles. In Chile, CE is endemic, and the role of livestock and dogs ( Canis lupus...

El reconocimiento de una nueva enfermedad infec-ciosa en un país constituye un desafío diagnóstico por la falta de reconocimiento por los médicos clínicos y la ausencia de pruebas diagnósticas. En el año 2006 se diagnosticó por primera vez en Chile un caso de tifus de los matorrales en un biólogo que regresaba de trabajo en terreno cerca de Ancud,...

We aimed to identify faeces belonging to either Darwin’s fox (Lycalopex fulvipes) or kodkod (Leopardus guigna) by using molecular genetic techniques, and to describe and compare the gastrointestinal parasites harbored by both carnivores in Chiloé Island. We found that 60% (25/42) and 88% (28/32) of faeces of Darwin’s fox and kodkod had parasite egg...

La conservación de la biodiversidad, es un gran desafío para nuestra sociedad por cuanto requiere importantes cambios sociales. Sin embargo, difícilmente se podrán impulsar dichos cambios sin un entendimiento de las dimensiones humanas de la conservación. Trabajar en dimensión humana de la conservación de la biodiversidad, significa destinar esfuer...

Marketing is a stressful process for beef calves, because they are removed from their environment, often weaned just before loading, loaded, transported, and unloaded. It also involves extended periods without food and water and mixing with unfamiliar animals in an unknown environment. Some studies have shown that calves sold through markets are ex...

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 sen...

Cystic echinococcosis (CE), a zoonotic disease caused by tapeworms of the species complex Echinococcus granulosus sensu lato, represents a substantial global health and economic burden. Within this complex, E. granulosus sensu stricto (genotypes G1 and G3) is the most frequent causative agent of human CE. Currently, there is no fully reliable metho...

Echinococcus granulosus sensu stricto (s.s.) is the major cause of human cystic echinococcosis worldwide and is listed among the most severe parasitic diseases of humans. To date, numerous studies have investigated the genetic diversity and population structure of E. granulosus s.s. in various geographic regions. However, there has been no global s...

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...

Background Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (MS) is a new and revolutionary identification method for microorganisms and has recently been introduced into clinical microbiology in many industrialized countries in Europe and North America. Objectives Our study aimed to compare the performance...

Data of microbial identification using Microflex LT and Vitek MS plus molecular biology. (XLSX)

Background: The Coquimbo Region in Chile has the highest incidence of hydatidosis in central and northern Chile. Aim: To analyze the incidence of human cystic echinococcosis (CE) in the Coquimbo Region between 2008 and 2012. Material and methods: Official records of reported cases were analyzed. The association of the location, age and sex wit...

Cystic echinococcosis, a zoonotic disease caused by Echinococcus granulosus sensu lato (s. l.), is a significant global public health concern. Echinococcus granulosus s. l. is currently divided into numerous genotypes (G1–G8 and G10) of which G1–G3 are the most frequently implicated genotypes in human infections. Although it has been suggested that...

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. MethodsA cross-secti...

Echinococcus granulosus is a taeniid cestode and the etiological agent of an infectious zoonotic disease known as cystic echinococcosis (CE) or hydatid disease. CE is a serious public health concern in many parts of the world, including the Americas, where it is highly endemic in many regions. Echinococcus granulosus displays high intraspecific gen...

This report summarizes the outcomes of a meeting on cystic echinococcosis (CE) in animals and humans in Chile held in Santiago, Chile, between the 21st and 22nd of January 2016. The meeting participants included representatives of the Departamento de Zoonosis, Ministerio de Salud (Zoonotic Diseases Department, Ministry of Health), representatives o...

Objective: To determine the prevalence of hydatidosis in humans and livestock in the Los Rios region during the years 1999-2009. Methods: A retrospective survey of all discharge records of patients undergoing removal of cysts produced by Echinococcus granulosus during the period 1999-2009 in the Hospital Clinico Regional of Valdivia was conducted....