Distribution, transmission and risk factors of infection with canine vector-borne pathogens in wild foxes and free-ranging dogs in Chile
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2021
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en
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Universidad Andrés Bello
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Los patógenos caninos transmitidos por vectores (CVBP) constituyen un
importante grupo de patógenos de distribución mundial que se transmiten por
artrópodos y afectan a los cánidos salvajes y domésticos. La distribución de los
patógenos transmitidos por vectores tiende a estar circunscrita a ciertas áreas con
características climáticas donde sus vectores son capaces de persistir y
reproducirse. En este aspecto, Chile posee una marcada variedad de regiones
bioclimáticas que proporcionan un escenario ideal para estudiar la distribución de
los patógenos transmitidos por vectores. Los CVBP más relevantes (Anaplasma
platys, Ehrlichia canis, micoplasmas hemotrópicos, Hepatozoon, piroplásmidos y
filarioides) son transmitidos, o presuntamente transmitidos, por garrapatas del
grupo de especies Rhipicephalus sanguineus, que están ampliamente presentes
en Chile. A pesar de esto, la información sobre la presencia, distribución e impacto
del CVBP en caninos domésticos y silvestres en el país es muy escasa y
probablemente ha sido poco estudiada.
Asimismo, los recientes cambios en el uso del suelo causados por la
urbanización y la fragmentación del hábitat han aumentado las probabilidades de
transmisión de patógenos entre especies silvestres y perros. Los perros
domésticos están muy extendidos en Chile y viven en simpatía con las tres
especies de zorros autóctonos presentes en el país: el zorro culpeo (Lycalopex
culpaeus), el zorro chilla (L. griseus) y el amenazado zorro de Darwin (L. fulvipes).
Estos perros rurales suelen estar en libertad y rara vez reciben tratamiento
antiparasitario, lo que puede facilitar aún más la transmisión de los patógenos
mencionados.
Así, el objetivo principal de la presente tesis fue describir la distribución
geográfica y la prevalencia de los CVBP más relevantes en cánidos domésticos y
salvajes a lo largo de seis regiones bioclimáticas de Chile. Se predice que estos
patógenos estarían asociados a regiones bioclimáticas con características más
adecuadas para el establecimiento de sus putativos vectores. Para lograr este objetivo, se obtuvieron muestras de sangre y suero de 981
perros, 155 zorros culpeo, 90 zorros chilla y 82 zorros de Darwin de seis regiones
bioclimáticas diferentes de Chile: Desierto Costero, Desierto Montañoso, Estepa,
Mediterráneo, Templado Cálido Lluvioso (TWR), y Templado Marítimo Lluvioso
(TMR). Se utilizó un conjunto de cebadores para detectar el ADN del CVBP, y
pruebas de inmunofluorescencia para la detección de anticuerpos contra algunos
de ellos. Las garrapatas y pulgas recuperadas de estos animales se identificaron
mediante claves taxonómicas, y los linajes del grupo de especies Rhipicephalus
sanguineus se designaron mediante herramientas moleculares. Por último, se
dedujeron los factores de riesgo de infección para los distintos hospedadores y el
CVBP utilizando modelos lineales generalizados (GLM), modelos lineales mixtos
generalizados (GLMM), la prueba de Chi-cuadrado y la prueba de Fischer, según
procediera.
En el primer capítulo se describió la presencia de ADN y/o anticuerpos
contra Anaplasmataceae en 719 perros, 132 zorros culpeo y 82 zorros chilla de las
seis regiones estudiadas. Las muestras de sangre de perros y zorros se
analizaron primero en busca de ADN de Anaplasmataceae, seguido de dos
protocolos específicos de Ehrlichia para inferir coinfecciones. Los anticuerpos
contra Anaplasma sp. y E. canis se evaluaron mediante inmunofluorescencia en
los perros. Se recogieron e identificaron los ectoparásitos y se determinaron los
linajes del grupo de especies de R. sanguineus mediante análisis moleculares y
filogenéticos. Por último, se investigaron los posibles factores de riesgo de
infección en las distintas regiones bioclimáticas y los distintos huéspedes. Todos
los amplicones de ADN obtenidos correspondieron a Anaplasma platys. La
presencia tanto de ADN como de anticuerpos de A. platys se confirmó en todas las
regiones bioclimáticas, a excepción de aquellas gran altitud y/o sin presencia de
ningún linaje del grupo de especies de R. sanguineus. Los perros infestados con
garrapatas de R. sanguineus fueron significativamente más propensos a estar
infectados y expuestos a Anaplasma spp. La prevalencia del ADN fue
significativamente mayor en los perros jóvenes (19%) que en los adultos (9%),
mientras que se encontró lo contrario para la seroprevalencia (19% frente al 35%, respectivamente). La prevalencia total del ADN de A. platys fue mayor en los
perros (11%) que en los zorros (4%), probablemente debido a una infestación de
garrapatas notablemente menor en los zorros. No se detectó ADN de Ehrlichia
canis en ninguna muestra, y sólo se detectaron anticuerpos contra este patógeno
en cuatro perros, en zonas con ambos linajes de R. sanguineus. Los perros sin
confinamiento en Chile podrían estar favoreciendo el mantenimiento de A. platys
en todas las zonas aptas para su vector. Aunque aparentemente es poco
frecuente, es posible que se produzca infección de perros a zorros, lo que debería
tenerse en cuenta en los planes de gestión en Chile.
En el segundo capítulo, se analizaron muestras de sangre de 626 perros,
140 zorros culpeo y 83 zorros chilla en busca de ADN de Mycoplasma mediante
PCR convencional y posterior secuenciación. Los factores de riesgo de infección
se dedujeron mediante modelos lineales mixtos generalizados y la estructura
genética mediante análisis de redes. En general, la prevalencia observada de
Mycoplasma haemocanis/Mycoplasma haemofelis (Mhc/Mhf) y Candidatus
Mycoplasma haematoparvum (CMhp) fue del 24% y el 13% en perros, del 20% y
el 7% en zorros culpeo, y del 26% y el 8% en zorros chilla, respectivamente.
Ambos hemoplasmas se confirmaron en todas las biorregiones, con mayor
prevalencia en aquellas donde las garrapatas del grupo de especies Rhipicephalus
sanguineus estaban ausentes. Candidatus Mycoplasma haematominutum y un
Mycoplasma sp. previamente encontrado en carnívoros sudamericanos fueron
detectados en zorros. Aunque los haplotipos de Mhc/Mhf y CMhp más prevalentes
fueron compartidos entre perros y zorros, el análisis de networks reveló una
estructura genética de Mhc/Mhf entre huéspedes en algunas regiones. El sexo
masculino se asoció a un mayor riesgo de infección por Mhc/Mhf y CMhp en
perros, lo que sugiere que la ingestión de sangre, producto de interacciones
agresivas, puede ser una vía de transmisión alternativa. No se identificó ningún
factor de riesgo en los zorros. Demostramos que los hemoplasmas caninos están
muy extendidos en Chile, detectándose en todas las especies muestreadas en
todas las biorregiones estudiadas, y que la transmisión interespecífica entre estas
especies está teniendo lugar. En el capítulo III se describió la epidemiología de los hemoplasmas en el
zorro de Darwin y en los perros simpátricos. Mhc es prevalente en el amenazado
zorro de Darwin en la isla de Chiloé, donde se concentra la mayor población de
esta especie (aproximadamente 420 individuos). Sin embargo, el origen de la
infección, su dinámica, su presencia en otras poblaciones de zorros y las posibles
consecuencias para la salud de los zorros siguen sin explorarse. Durante ocho
años, se examinó y caracterizó el ADN de este hemoplasma en la sangre de 82
zorros de Chiloé y de otras dos poblaciones de zorros de la misma especie, y de
250 perros sin confinamiento de Chiloé. La prevalencia de Mhc en zorros fue
constante durante los años de estudio, y se confirmó la coinfección con
Candidatus Mycoplasma haematoparvum en el 30% de los zorros. Ambas
especies de hemoplasma se detectaron en las dos poblaciones de zorros del
continente y en los perros de Chiloé. Mhc fue significativamente más prevalente y
genéticamente más diverso en los zorros que en los perros. Dos de los siete
haplotipos de Mhc identificados fueron compartidos entre estas especies. Los
análisis de network no mostraron una estructura genética por factores de especie
(zorros frente a perros), geográficos (poblaciones insulares frente a continentales)
o temporales (años de estudio). La probabilidad de infección por Mhc aumentó con
la edad del zorro, pero no se asoció con el sexo, la estación del año o el grado de
antropización de los hábitats de cada zorro. Algunos zorros recapturados con años
de diferencia fueron infectados con el mismo haplotipo en ambos eventos y no se
asociaron alteraciones hematológicas con la infección por hemoplasma, lo que
sugiere tolerancia a la infección. En conjunto, nuestros resultados indican que Mhc
es endémico en el zorro de Darwin y que predomina la transmisión intraespecífica.
Sin embargo, un patógeno tan prevalente en una especie amenazada representa
una preocupación que debe ser considerada en las acciones de conservación.
En el capítulo IV, se evaluó la presencia y distribución de parásitos
transmitidos por vectores en perros, zorros culpeo y zorros chilla. Se estudió la
presencia de Hepatozoon, piroplásmidos y nematodos en muestras de sangre de
774 perros rurales sin confinamiento, 154 zorros culpeo y 91 zorros chilla de las
seis regiones bioclimáticas. Se detectó una prevalencia del 43% de ADN de Hepatozoon spp. en zorros. Todas las secuencias en el zorro culpeo se asociaron
filogenéticamente con H. felis. En los zorros chilla, todas pertenecían al clado de
H. americanum, excepto una, que mostró un 100% de identidad con H. canis. La
evaluación de los factores de riesgo identificó que los zorros juveniles presentaban
una mayor probabilidad de infección por Hepatozoon. Todos los perros resultaron
negativos para Hepatozoon. Se encontró ADN de Piroplasmida en el 0,7% de los
perros y en ningún zorro. Se detectaron anticuerpos contra Babesia sp. en el 24%
de los perros y en el 25% de los zorros. Se observó una asociación positiva entre
la presencia de anticuerpos contra Babesia y una elevada carga de Rhipicephalus
sanguineus en los perros. Acanthocheilonema reconditum fue el único nematodo
detectado en sangre, estando presente en el 1,5% de los perros y en ningún zorro.
Nuestro estudio presenta la primera descripción de Babesia en perros y de
Hepatozoon en zorros de Chile. Se detectó un cluster para la presencia de
Babesia en perros en la región de la Estepa, y se encontró una asociación positiva
entre la presencia de anticuerpos contra este piroplásmido y altas cargas de
garrapatas del grupo de especies R. sanguineus. A su vez, se detectó una posible
preferencia de hospedador entre los zorros para las especies de Hepatozoon. La
presencia de parásitos transmitidos por vectores que no habían sido reportados
antes en Chile es fundamental para lograr un correcto diagnóstico en perros
domésticos, mejorando las medidas de control que pueden beneficiar aún más los
planes de conservación de cánidos silvestres simpátricos.
Debido al carácter exhaustivo de este trabajo, en el que se estudiaron los
CVBP más relevantes en las cuatro especies de cánidos de Chile a través de seis
regiones bioclimáticas del país abarcando 3000 km, se considera que este
proyecto contribuyó a completar la pobreza de conocimiento en la epidemiología
de los patógenos transmitidos por vectores compartidos entre animales
domésticos y silvestres en Chile. Los resultados obtenidos pueden ser de utilidad
en programas de conservación de la fauna silvestre, así como en la práctica
clínica.
Canine vector-borne pathogens (CVBP) comprise a major group of worldwidedistributed pathogens that are transmitted by arthropods and affect wild and domestic canids. Vector-borne pathogens distribution tends to be circumscribed to certain areas with climatic features where their vectors are able to persist and reproduce. In this aspect, Chile possess a marked variety of bioclimatic regions that provides an ideal scenario to study the distribution of vector-borne pathogens. The most relevant CVBP (Anaplasma platys, Ehrlichia canis, hemotropic mycoplasmas, Hepatozoon, piroplasmids, and filarioids) are known or believed to be transmitted by ticks of the Rhipicephalus sanguineus species group, which are widely distributed in Chile. Despite this, information about the presence, distribution, and impact of CVBP in domestic and wild canines in the country is very scarce and has probably been underestimated. Likewise, recent changes in land use caused by urbanization and habitat fragmentation have increased the probabilities of cross-species pathogen transmission between wild carnivores and dogs. Domestic dogs are widespread in Chile, living in sympatry with the three species of native foxes present in the country: the Andean fox (Lycalopex culpaeus), the South American grey fox (L. griseus), and the endangered Darwin’s fox (L. fulvipes). These rural dogs are often allowed to range free and rarely receive any antiparasitic treatment, what may further facilitate pathogen transmission. In consequence, the main objective of the present thesis was to describe the geographical distribution, prevalence, and risk factors of the most relevant CVBP in domestic and wild canids across six bioclimatic regions of Chile. We predict that these pathogens would be associated with bioclimatic regions with characteristics more suitable for the establishment of their putative vectors. To achieve this goal, blood and serum samples of 981 dogs, 155 Andean foxes, 90 grey foxes, and 82 Darwin’s foxes were obtained from six different bioclimatic regions of Chile: Coastal Desert, Mountain Desert, Steppe, Mediterranean, Temperate Warm Rainy (TWR), and Temperate Maritime Rainy (TMR). A set of primers were used to detect DNA of the CVBP, and immunofluorescence antibody tests for the detection of antibodies against some of them. Ticks and fleas retrieved from these animals were identified using taxonomic keys, and lineages temperate and tropical of the Rhipicephalus sanguineus species group were designated using molecular tools. Finally, risk factors of infection were inferred for the different hosts and CVBP using Generalized Linear Models (GLM), Generalized Linear Mixed Models (GLMM), Chi-square test, and Fischer’s test, as appropriate. In the first chapter, the presence of DNA and/or antibodies against Anaplasmataceae were described in 719 dogs, 132 Andean foxes, and 82 South American grey foxes from the six regions studied. Dog and fox blood samples were first screened for DNA of Anaplasmataceae followed by two Ehrlichia-specific protocols to infer coinfections. Antibodies against Anaplasma sp. and E. canis were assessed by immunofluorescence in dogs. Ectoparasites were collected and identified, with the determination of the lineages of the R. sanguineus species group by molecular and phylogenetic analyses. Finally, potential risk factors for infection were investigated across the different bioclimatic regions and hosts. All DNA amplicons obtained from the screening protocol corresponded to Anaplasma platys. The occurrence of both A. platys DNA and antibodies was confirmed in all six bioclimatic regions, except for regions at high altitude and/or without either R. sanguineus species group lineage present. Dogs infested with R. sanguineus ticks were significantly more prone to be infected and exposed to Anaplasma spp. Prevalence was significantly higher in juvenile (19%) than in adult dogs (9%), whereas the opposite was found for seroprevalence (19% versus 35%, respectively). Overall prevalence of A. platys DNA was higher in dogs (11%) than in foxes (4%), probably owing to markedly lower tick infestations in the foxes. Ehrlichia canis DNA was not detected in any sample, and antibodies against this pathogen were detected only in four dogs, in areas with both R. sanguineus lineages. Free-ranging dogs in Chile could be favoring the maintenance of A. platys in all areas suitable for its tick vector. Although apparently infrequent, spillovers from dogs to foxes may be taking place and should be considered in management plans in Chile. In the second chapter, blood samples of 626 dogs, 140 Andean foxes, and 83 South American grey foxes were screened for Mycoplasma DNA by conventional PCR and sequencing. Risk factors of infection were inferred using Generalized Linear Mixed Models and genetic structure by network analyses. Overall, Mycoplasma haemocanis/Mycoplasma haemofelis (Mhc/Mhf) and Candidatus Mycoplasma haematoparvum (CMhp) observed prevalence was 24% and 13% in dogs, 20% and 7% in Andean foxes, and 26% and 8% in grey foxes, respectively. Both hemoplasmas were confirmed in all the bioclimatic regions, with higher prevalence in those where ticks from the R. sanguineus species group were absent. Candidatus M. haematominutum and a Mycoplasma sp. previously found in South American carnivores were detected in one fox each. Although the most prevalent Mhc/Mhf and CMhp sequence types were shared between dogs and foxes, network analysis revealed genetic structure of Mhc/Mhf between hosts in some regions. Male were associated with a higher risk of Mhc/Mhf and CMhp infection in dogs, suggesting that blood ingestion product of aggressive interactions, may be an alternative transmission way. No risk factor was identified in foxes. We showed that canine hemoplasmas are widespread in Chile, being detected in all the sampled species across all the studied bioclimatic regions, and that interspecific transmission between these species is taking place. In Chapter III, the epidemiology of hemoplasmas in the endangered Darwin's fox and sympatric dogs was described. Mycoplasma haemocanis is prevalent in the endangered Darwin’s fox in its main stronghold, Chiloé Island. The origin of the infection, its dynamics, its presence in other fox populations and the potential consequences for fox health remain unknown. During eight years, hemoplasmal DNA was screened and characterized in blood from 82 foxes in Chiloé and other two fox populations and 250 free-ranging dogs from Chiloé. The prevalence of Mhc in foxes was constant during the study years, and coinfection with CMhp was confirmed in 30% of the foxes. Both hemoplasma species were detected in the two mainland fox populations and in Chiloé dogs. Mycoplasma haemocanis was significantly more prevalent and more genetically diverse in foxes than in dogs. Two of the seven Mhc haplotypes identified were shared between these species. Network analyses did not show genetic structure either by species (foxes vs. dogs), geographic (island vs. mainland populations), or temporal (years of study) factors. The probability of infection with Mhc increased with fox age but was not associated with sex, season, or degree of anthropization of individual fox habitats. Some foxes recaptured with years of difference were infected with the same haplotype in both events and no hematological alterations were associated with hemoplasma infection, suggesting tolerance to the infection. Altogether, our results indicate that Mhc is endemic in the Darwin’s fox and that intraspecific transmission is predominant. Nevertheless, such a prevalent pathogen in a threatened species represents a concern that must be considered in conservation actions. In Chapter IV, the presence and distribution of vector-borne parasites in dogs, Andean, and grey foxes were evaluated. The presence of Hepatozoon, piroplasmids and filarids was studied in blood samples of 774 free-ranging rural dogs, 154 Andean foxes, and 91 South American grey foxes from the six bioclimatic regions. We found a prevalence of 43% of Hepatozoon spp. DNA in foxes. All sequences in Andean fox were phylogenetically associated with H. felis. In grey foxes, all belonged to the H. americanum clade, except for one, that showed 100% identity with H. canis. Risk factor assessment identified juvenile age associated with higher probability of Hepatozoon infection in foxes. All dogs were negative for Hepatozoon DNA. DNA of Piroplasmida was found in 0.7% of the dogs, and in no fox. Antibodies against Babesia sp. were detected in 24% of the dogs and 25% of the foxes. A positive association between the presence of antibodies against Babesia and high Rhipicephalus sanguineus burden in dogs was observed. Acanthocheilonema reconditum was the only nematode detected in blood, being present in 1.5% of the dogs and in no fox. Our study presents the first description of Babesia in dogs and of Hepatozoon in foxes from Chile. A cluster for Babesia presence in dogs was detected in the Steppe region, and a positive association was found between the presence of antibodies against this piroplasmid and high burdens of ticks of the R. sanguineus species group. Possible host preference among foxes was detected for Hepatozoon species. The presence of vector-borne parasites that were not reported in Chile before, is essential to achieve a correct diagnosis in domestic dogs, improving control measures that can further benefit conservation plans for sympatric wild canids. Due to the comprehensive nature of this work, in which the most relevant CVBP in the four canid species of Chile were studied across a latitudinal gradient of 3000 km, this project contributes to fill the knowledge gap in the epidemiology of vector-borne pathogens shared between domestic and wild animals in Chile, and have implications in the transmission ways of the studied agents. The results obtained can be useful in wildlife conservation programs as well as in clinical practice.
Canine vector-borne pathogens (CVBP) comprise a major group of worldwidedistributed pathogens that are transmitted by arthropods and affect wild and domestic canids. Vector-borne pathogens distribution tends to be circumscribed to certain areas with climatic features where their vectors are able to persist and reproduce. In this aspect, Chile possess a marked variety of bioclimatic regions that provides an ideal scenario to study the distribution of vector-borne pathogens. The most relevant CVBP (Anaplasma platys, Ehrlichia canis, hemotropic mycoplasmas, Hepatozoon, piroplasmids, and filarioids) are known or believed to be transmitted by ticks of the Rhipicephalus sanguineus species group, which are widely distributed in Chile. Despite this, information about the presence, distribution, and impact of CVBP in domestic and wild canines in the country is very scarce and has probably been underestimated. Likewise, recent changes in land use caused by urbanization and habitat fragmentation have increased the probabilities of cross-species pathogen transmission between wild carnivores and dogs. Domestic dogs are widespread in Chile, living in sympatry with the three species of native foxes present in the country: the Andean fox (Lycalopex culpaeus), the South American grey fox (L. griseus), and the endangered Darwin’s fox (L. fulvipes). These rural dogs are often allowed to range free and rarely receive any antiparasitic treatment, what may further facilitate pathogen transmission. In consequence, the main objective of the present thesis was to describe the geographical distribution, prevalence, and risk factors of the most relevant CVBP in domestic and wild canids across six bioclimatic regions of Chile. We predict that these pathogens would be associated with bioclimatic regions with characteristics more suitable for the establishment of their putative vectors. To achieve this goal, blood and serum samples of 981 dogs, 155 Andean foxes, 90 grey foxes, and 82 Darwin’s foxes were obtained from six different bioclimatic regions of Chile: Coastal Desert, Mountain Desert, Steppe, Mediterranean, Temperate Warm Rainy (TWR), and Temperate Maritime Rainy (TMR). A set of primers were used to detect DNA of the CVBP, and immunofluorescence antibody tests for the detection of antibodies against some of them. Ticks and fleas retrieved from these animals were identified using taxonomic keys, and lineages temperate and tropical of the Rhipicephalus sanguineus species group were designated using molecular tools. Finally, risk factors of infection were inferred for the different hosts and CVBP using Generalized Linear Models (GLM), Generalized Linear Mixed Models (GLMM), Chi-square test, and Fischer’s test, as appropriate. In the first chapter, the presence of DNA and/or antibodies against Anaplasmataceae were described in 719 dogs, 132 Andean foxes, and 82 South American grey foxes from the six regions studied. Dog and fox blood samples were first screened for DNA of Anaplasmataceae followed by two Ehrlichia-specific protocols to infer coinfections. Antibodies against Anaplasma sp. and E. canis were assessed by immunofluorescence in dogs. Ectoparasites were collected and identified, with the determination of the lineages of the R. sanguineus species group by molecular and phylogenetic analyses. Finally, potential risk factors for infection were investigated across the different bioclimatic regions and hosts. All DNA amplicons obtained from the screening protocol corresponded to Anaplasma platys. The occurrence of both A. platys DNA and antibodies was confirmed in all six bioclimatic regions, except for regions at high altitude and/or without either R. sanguineus species group lineage present. Dogs infested with R. sanguineus ticks were significantly more prone to be infected and exposed to Anaplasma spp. Prevalence was significantly higher in juvenile (19%) than in adult dogs (9%), whereas the opposite was found for seroprevalence (19% versus 35%, respectively). Overall prevalence of A. platys DNA was higher in dogs (11%) than in foxes (4%), probably owing to markedly lower tick infestations in the foxes. Ehrlichia canis DNA was not detected in any sample, and antibodies against this pathogen were detected only in four dogs, in areas with both R. sanguineus lineages. Free-ranging dogs in Chile could be favoring the maintenance of A. platys in all areas suitable for its tick vector. Although apparently infrequent, spillovers from dogs to foxes may be taking place and should be considered in management plans in Chile. In the second chapter, blood samples of 626 dogs, 140 Andean foxes, and 83 South American grey foxes were screened for Mycoplasma DNA by conventional PCR and sequencing. Risk factors of infection were inferred using Generalized Linear Mixed Models and genetic structure by network analyses. Overall, Mycoplasma haemocanis/Mycoplasma haemofelis (Mhc/Mhf) and Candidatus Mycoplasma haematoparvum (CMhp) observed prevalence was 24% and 13% in dogs, 20% and 7% in Andean foxes, and 26% and 8% in grey foxes, respectively. Both hemoplasmas were confirmed in all the bioclimatic regions, with higher prevalence in those where ticks from the R. sanguineus species group were absent. Candidatus M. haematominutum and a Mycoplasma sp. previously found in South American carnivores were detected in one fox each. Although the most prevalent Mhc/Mhf and CMhp sequence types were shared between dogs and foxes, network analysis revealed genetic structure of Mhc/Mhf between hosts in some regions. Male were associated with a higher risk of Mhc/Mhf and CMhp infection in dogs, suggesting that blood ingestion product of aggressive interactions, may be an alternative transmission way. No risk factor was identified in foxes. We showed that canine hemoplasmas are widespread in Chile, being detected in all the sampled species across all the studied bioclimatic regions, and that interspecific transmission between these species is taking place. In Chapter III, the epidemiology of hemoplasmas in the endangered Darwin's fox and sympatric dogs was described. Mycoplasma haemocanis is prevalent in the endangered Darwin’s fox in its main stronghold, Chiloé Island. The origin of the infection, its dynamics, its presence in other fox populations and the potential consequences for fox health remain unknown. During eight years, hemoplasmal DNA was screened and characterized in blood from 82 foxes in Chiloé and other two fox populations and 250 free-ranging dogs from Chiloé. The prevalence of Mhc in foxes was constant during the study years, and coinfection with CMhp was confirmed in 30% of the foxes. Both hemoplasma species were detected in the two mainland fox populations and in Chiloé dogs. Mycoplasma haemocanis was significantly more prevalent and more genetically diverse in foxes than in dogs. Two of the seven Mhc haplotypes identified were shared between these species. Network analyses did not show genetic structure either by species (foxes vs. dogs), geographic (island vs. mainland populations), or temporal (years of study) factors. The probability of infection with Mhc increased with fox age but was not associated with sex, season, or degree of anthropization of individual fox habitats. Some foxes recaptured with years of difference were infected with the same haplotype in both events and no hematological alterations were associated with hemoplasma infection, suggesting tolerance to the infection. Altogether, our results indicate that Mhc is endemic in the Darwin’s fox and that intraspecific transmission is predominant. Nevertheless, such a prevalent pathogen in a threatened species represents a concern that must be considered in conservation actions. In Chapter IV, the presence and distribution of vector-borne parasites in dogs, Andean, and grey foxes were evaluated. The presence of Hepatozoon, piroplasmids and filarids was studied in blood samples of 774 free-ranging rural dogs, 154 Andean foxes, and 91 South American grey foxes from the six bioclimatic regions. We found a prevalence of 43% of Hepatozoon spp. DNA in foxes. All sequences in Andean fox were phylogenetically associated with H. felis. In grey foxes, all belonged to the H. americanum clade, except for one, that showed 100% identity with H. canis. Risk factor assessment identified juvenile age associated with higher probability of Hepatozoon infection in foxes. All dogs were negative for Hepatozoon DNA. DNA of Piroplasmida was found in 0.7% of the dogs, and in no fox. Antibodies against Babesia sp. were detected in 24% of the dogs and 25% of the foxes. A positive association between the presence of antibodies against Babesia and high Rhipicephalus sanguineus burden in dogs was observed. Acanthocheilonema reconditum was the only nematode detected in blood, being present in 1.5% of the dogs and in no fox. Our study presents the first description of Babesia in dogs and of Hepatozoon in foxes from Chile. A cluster for Babesia presence in dogs was detected in the Steppe region, and a positive association was found between the presence of antibodies against this piroplasmid and high burdens of ticks of the R. sanguineus species group. Possible host preference among foxes was detected for Hepatozoon species. The presence of vector-borne parasites that were not reported in Chile before, is essential to achieve a correct diagnosis in domestic dogs, improving control measures that can further benefit conservation plans for sympatric wild canids. Due to the comprehensive nature of this work, in which the most relevant CVBP in the four canid species of Chile were studied across a latitudinal gradient of 3000 km, this project contributes to fill the knowledge gap in the epidemiology of vector-borne pathogens shared between domestic and wild animals in Chile, and have implications in the transmission ways of the studied agents. The results obtained can be useful in wildlife conservation programs as well as in clinical practice.
Notas
Tesis (Doctora en Medicina de la Conservación)
Palabras clave
Microorganismos Patógenos, Transmisión, Perros, Enfermedades, Zorros, Fauna Silvestre, Investigaciones, Chile