Trypanosoma evansi in horses from Colombia - associated infection factors

Background: Trypanosoma evansi is the most common protozoan in tropical and subtropical regions of the world, due to its ability to maintain and be transmitted by vectors such as Stomoxys spp. and Tabanus spp. This protozoan causes high morbidity and mortality rates in horses in African, American and Asian countries. In the years 2021 and 2022, a high mortality rate was reported among horses with symptoms associated with Trypanosoma spp. in the municipality of Arauca, department of Arauca, Colombia. The investigation described here was therefore carried out, seeking to identify the pathogens and risk factors that led to the death of the horses in this region of Colombia. Cases: Blood samples were collected from Colombian criollo horses and dogs, as were samples of ticks, flies and horseflies that infested the horses. A variety of tissue samples were removed from the horses a few min after their death for histopathological analysis. Two questionnaires were applied to obtain information about the horses and the environment in which they live. The results of the clinical examination revealed pale mucous membranes, jaundice, high fever, dehydration and lethargy. The horses were also infested with Amblyomma mixtum (17.6%) and Dermacentor nitens (82.4%) ticks, and with Tabanus pungens (74%), Tabanus spp. (26%), and Stomoxys calcitrans flies (100%), while the dogs were infested with Rhipicephalus sanguineus s.l. (77.7%) and Amblyomma mixtum (22.2%) ticks. The blood smear test results revealed the presence of Trypanosoma spp. in 66.6% (n = 4) of the horse blood samples, and in 50% (n = 1) of the dog blood samples. PCR performed to identify the Trypanosoma species confirmed the presence of T. evansi. Histological examination of the spleen revealed the involvement and dissemination of T. evansi in the tissues. The horses also showed the presence of Equine Infectious Anemia Virus (EIAV). Discussion: This is the first updated specific report of T. evansi in criollo horses in the savannah flood zone of the municipality of Arauca, Colombia. The main risk associated with T. evansi infection in horses was found to be infestation with the natural vector T. pungens and the mechanical vector S. calcitrans, which are efficient ectoparasites for the transmission of this parasite. The presence of T. evansi in dogs represents a constant risk to horses, because dogs may serve as a reservoir for the maintenance of the hemoparasite in the population under study. Another risk factor for horses could be the presence of vampire bats (Desmodus rotundus), a species of bat that has been described as a vector and reservoir of T. evansi in Colombia. The presence of EIAV antibodies in the horses under study can be attributed to the exposure of sick horses to vectors of this virus, such as Tabanus spp., S. calcitrans and inanimate needle-shaped fomites. This is the first study that identifies the coinfection of T. evansi and EIAV in horses in the floodplain region of Colombia. In view of the importance of these 2 pathologies to the health of horses, a greater number of tests and a larger animal population will be required to determine if this coinfection is the cause of the death of criollo horses in this region of Colombia. Lastly, the owners reported that pharmacological control with trypanocides has not been successful in most of the outbreaks that occurred during the years 2021 and 2022. This may suggest that Trypanosoma evansi is developing resistance to these drugs; therefore, specific studies will be required in the future to test this hypothesis.

Genetic identification, clinical and epidemiological aspects of an equine infectious anemia outbreak in the Rio Grande do Sul state, Brazil / Identificação genética, aspectos clínicos e epidemiológicos de um foco de anemia infecciosa equina no estado do Rio Grande do Sul, Brasil

The study describes the genetic identification, clinical, and epidemiological characteristics of an outbreak of equine infectious anemia occurring in the state of Rio Grande do Sul, Brazil. Three animals kept in the periurban region of Uruguaiana city tested positive for the AGID test. The serology was performed as a requirement for transit. None of the animals showed clinical signs of infection, one animal was necropsied, and the others were stolen. In the post-mortem examination, no macroscopic changes were observed, and microscopically, discrete hemosiderosis was detected in fragments of the liver and spleen. Amplifying and sequencing a proviral DNA fragment in blood, spleen, and mesenteric lymph node samples confirmed EIAV infection. Phylogenetic analysis of the first sequenced EIAV sample from the Rio Grande do Sul State indicates a high similarity with other Brazilian samples. Results confirmed the viral presence in the state's herds and described epidemiological and virological characteristics of EIA that contribute to the maintenance and dissemination of the virus in herds.

O estudo descreve a identificação genética, as características clínicas e epidemiológicas de um foco de Anemia Infecciosa Equina que ocorreu no Estado do Rio Grande do Sul, Brasil. Três equinos criados na região periurbana da cidade de Uruguaiana testaram positivos pela prova sorológica de IDGA. O exame foi realizado como requerimento para trânsito dos animais. Nenhum animal apresentava sinais clínicos da infecção, um cavalo foi necropsiado e os outros dois foram roubados. Na necropsia não obsevou-se nenhuma alteração e microscopicamente foi constatada hemosiderose discreta em fragmento do fígado e baço. A infecção foi confirmada pela amplificação e sequenciamento de um segmento do genoma pró-viral do EIAV de amostras do sangue, baço e linfonodo mesentérico. A análise filogenética do primeiro EIAV sequenciado no Estado do RS indica similaridade com outras amostras que circulam no Brasil. O resultado confirma a presença do vírus no rebanho equino da região e descreve características clínicas e epidemiológicas que contribuem para a manutenção e disseminação do vírus no rebanho.

True prevalence and spatial distribution of equine infectious anemia virus (EIAV) in horses from northeast region of Brazil

Equine infectious anemia (EIA) is a viral infection, caused by a lentivirus of the Retroviridae family, Orthoretrovirinael subfamily and its occurrence generates significant economic losses due to culling of positive animals as a measure of infection control. The objective of this work was to determine the prevalence of horses positive for equine infectious anemia virus (EIAV) and to identify the occurrence of areas with higher densities of cases in the states of Paraíba (PB), Pernambuco (PE), Rio Grande do Norte (RN) and Ceará (CE), Northeast region of Brazil, during the rainy (May and June) and dry (October and November) periods of 2017 and 2018. Serum samples from 6,566 horses from the states of PB, PE, RN and CE, Brazil, provided by the Laboratório Veterinária Diagnóstico - Ltda., were used. Serological diagnosis of EIA was performed using indirect enzyme-linked immunosorbent assay (ELISA) as a screening test and agar gel immunodiffusion test (AGID) as a confirmatory test. The apparent prevalence was obtained by dividing the number of seroreactive animals by the total number of animals, while the true prevalence was estimated by adjusting the apparent prevalence, considering the sensitivity (100%) and specificity (98.6%) of the diagnostic protocol used. For the construction of Kernel estimates, the Quartic function was used. In the dry season, of the 1,564 animals sampled, 28 were serologically positive, of which 19 belonged to the state of Ceará, 7 to Paraíba and 2 to Rio Grande do Norte. In 2018, it was observed that, during the rainy season, 26 of the 1,635 horses were seroreactive, with 19 cases resulting from Ceará, 4 from Paraíba and 3 from Pernambuco. In the dry season, 32 of the 1,526 animals were seroreactive to EIAV, of which 26 were from Ceará, 3 from Paraíba, 1 from Rio Grande do Norte and 2 from Pernambuco. In the dry period of 2017, the CE had a real prevalence of 1.22% (95% CI = 0.05 - 2.99%). In 2018, during the rainy season, prevalences of 0.03% (95% CI = 0 - 1.18%) were identified in CE and 1.69% (95% CI = 0 - 8.38%) in PE. Regarding the 2018 dry period, a prevalence of 1.32% (95% CI = 0.26 - 2.84%) was found in the state of CE. In both dry and rainy periods of 2017, the presence of spatial clusters of animals positive for EIA was observed, mainly in the border areas among the states of CE, PE, PB and RN. In 2018, there was a variation in the distribution of areas with higher densities of cases between the rainy and dry periods. The state of CE had the highest prevalence of positive animals and the presence of areas with higher densities of EIA cases in both climatic periods, in the years 2017 and 2018. In some municipalities of the CE, important sporting events of agglomeration of animals take place, which can favor the transmission of EIAV by facilitating the contact of infected and susceptible animals. Population density may be a factor associated with the higher prevalence observed in this region, as it has the second largest herd among the states studied. Higher densities indirectly contribute to the occurrence of infectious diseases, as they favor the contact of infected and susceptible animals. The occurrence of higher densities of cases in the border areas of the states of PE, RN, CE, and PB may be related to the greater movement of animals in these regions, favoring the indirect contact of infected horses with susceptible ones. The observed results demonstrate the circulation of the EIAV in four states in the Northeast region of Brazil.(AU)

Ocorrência de equídeos soropositivos para os vírus das encefalomielites e anemia infecciosa no Estado de Mato Grosso

The present work evaluated the occurrence of seropositive equids for eastern encephalomyelitis virus (EEE), western encephalomyelitis virus (WEE), Venezuelan encephalomyelitis virus (VEE) and infectious anemia virus (IAV) in the Pantanal, Savannah and Amazon biomes of Mato Grosso State, Brazil. The detection of antibodies against IAV was carried out in 886 sera of equids by the immunodiffusion test, and antibodies against EEE, WEE and VEE were evaluated in 473 sera by the seroneutralization test performed in VERO cells. The results showed 46 IAV seropositive equids (5.1%). No sera was positive in the Amazon region, and the Pantanal biome showed a higher occurrence with 36.6% of seropositives (P 0.05). No sera was positive for WEE virus and 168 (35.5%) and 31 (6.5%) equids were positive for EEE and VEE respectively. Higher frequencies (P 0.05) were observed for EEE in the Pantanal and Amazon regions with 45.8% and 62.0% respectively. Regarding EEV, no differences were observed between the Pantanal, Savannah and Amazon regions, presenting 4.1%, 6.4% and 10.3% respectively (P > 0.05). Despite that IAV was not observed in equids from the Amazon, the occurrence of seropositive equids agree with the Brazilian prevalence. The differences of EEE and VEE behavior between biomes reinforce the presence of animal reservoirs, along with environmental and weather characteristics that support vector maintenance, which favor the presence of the viral infection in Mato Grosso State.

O presente trabalho determinou a ocorrência de equídeos com sorologia positiva para os vírus das encefalomielites virais dos tipos Leste (EEL), Oeste (EEO) e Venezuelana (EEV) e Anemia Infecciosa (AIE) nos biomas Amazônico, Pantaneiro e Cerrado do Estado de Mato Grosso. A detecção de anticorpos para AIE foi realizada em 886 soros pela prova de Imunodifusão em Gel de Ágar (IDGA), enquanto que para EEL, EEO e EEV foi realizada em 473 soros pela Microtécnica de Soroneutra-lização viral em culturas de células VERO. Para AIE, 46 (5,1%) equídeos foram positivos, não sendo observados animais positivos da região amazônica e a maior frequência ocorrendo no ambiente do pantanal com 36,6% de animais positivos (P 0,05). Para as encefalites virais, foram detectados 168 (35,5%) equídeos positivos para EEL e 31 (6,5%) para EEV. Não houve soros positivos para EEO. As maiores frequências de animais positivos para EEL foram observadas nos ambientes pantaneiro e amazônico com 45,8% e 62,0%, respectivamente (P 0,05). Os três biomas estudados apresentaram ocorrência similar (P > 0.05) de animais positivos para EEV, com 4,1%, 6,4% e 10,3% para o pantanal, cerrado e amazônia, respectivamente. Embora não apresentando equídeos reagente ao vírus da AIE na região amazônica, a presença de positivos em Mato Grosso encontra-se dentro do relatado no Brasil. O comportamento diferenciado do vírus da EEL e EEV nos três ecossistemas estudados reforça a presença de animais reservatórios, condições ambientais e climáticas que favorecem a proliferação de vetores que propiciam a infecção pelos vírus no Estado de Mato Grosso.

Ocorrência de equídeos soropositivos para os vírus das encefalomielites e anemia infecciosa no estado de Mato Grosso / The occurrence of equids seropositive for encephalomyelitis and infectious anemia virus in Mato Grosso state, Brazil

O presente trabalho determinou a ocorrência de equídeos com sorologia positiva para os vírus das encefalomielites virais dos tipos Leste (EEL), Oeste (EEO) e Venezuelana (EEV) e Anemia Infecciosa (AIE) nos biomas Amazônico, Pantaneiro e Cerrado do Estado de Mato Grosso. A detecção de anticorpos para AIE foi realizada em 886 soros pela prova de Imunodifusão em Gel de Ágar (IDGA), enquanto que para EEL, EEO e EEV foi realizada em 473 soros pela Microtécnica de Soroneutra-lização viral em culturas de células VERO. Para AIE, 46 (5,1%) equídeos foram positivos, não sendo observados animais positivos da região amazônica e a maior frequência ocorrendo no ambiente do pantanal com 36,6% de animais positivos (P 0.05) de animais positivos para EEV, com 4,1%, 6,4% e 10,3% para o pantanal, cerrado e amazônia, respectivamente. Embora não apresentando equídeos reagente ao vírus da AIE na região amazônica, a presença de positivos em Mato Grosso encontra-se dentro do relatado no Brasil. O comportamento diferenciado do vírus da EEL e EEV nos três ecossistemas estudados reforça a presença de animais reservatórios, condições ambientais e climáticas que favorecem a proliferação de vetores que propiciam a infecção pelos vírus no Estado de Mato Grosso.

The present work evaluated the occurrence of seropositive equids for eastern encephalomyelitis virus (EEE), western encephalomyelitis virus (WEE), Venezuelan encephalomyelitis virus (VEE) and infectious anemia virus (IAV) in the Pantanal, Savannah and Amazon biomes of Mato Grosso State, Brazil. The detection of antibodies against IAV was carried out in 886 sera of equids by the immunodiffusion test, and antibodies against EEE, WEE and VEE were evaluated in 473 sera by the seroneutralization test performed in VERO cells. The results showed 46 IAV seropositive equids (5.1%). No sera was positive in the Amazon region, and the Pantanal biome showed a higher occurrence with 36.6% of seropositives (P 0.05). Despite that IAV was not observed in equids from the Amazon, the occurrence of seropositive equids agree with the Brazilian prevalence. The differences of EEE and VEE behavior between biomes reinforce the presence of animal reservoirs, along with environmental and weather characteristics that support vector maintenance, which favor the presence of the viral infection in Mato Grosso State.

Ocorrência de equídeos soropositivos para os vírus das encefalomielites e anemia infecciosa no Estado de Mato Grosso

The present work evaluated the occurrence of seropositive equids for eastern encephalomyelitis virus (EEE), western encephalomyelitis virus (WEE), Venezuelan encephalomyelitis virus (VEE) and infectious anemia virus (IAV) in the Pantanal, Savannah and Amazon biomes of Mato Grosso State, Brazil. The detection of antibodies against IAV was carried out in 886 sera of equids by the immunodiffusion test, and antibodies against EEE, WEE and VEE were evaluated in 473 sera by the seroneutralization test performed in VERO cells. The results showed 46 IAV seropositive equids (5.1%). No sera was positive in the Amazon region, and the Pantanal biome showed a higher occurrence with 36.6% of seropositives (P 0.05). No sera was positive for WEE virus and 168 (35.5%) and 31 (6.5%) equids were positive for EEE and VEE respectively. Higher frequencies (P 0.05) were observed for EEE in the Pantanal and Amazon regions with 45.8% and 62.0% respectively. Regarding EEV, no differences were observed between the Pantanal, Savannah and Amazon regions, presenting 4.1%, 6.4% and 10.3% respectively (P > 0.05). Despite that IAV was not observed in equids from the Amazon, the occurrence of seropositive equids agree with the Brazilian prevalence. The differences of EEE and VEE behavior between biomes reinforce the presence of animal reservoirs, along with environmental and weather characteristics that support vector maintenance, which favor the presence of the viral infection in Mato Grosso State.

O presente trabalho determinou a ocorrência de equídeos com sorologia positiva para os vírus das encefalomielites virais dos tipos Leste (EEL), Oeste (EEO) e Venezuelana (EEV) e Anemia Infecciosa (AIE) nos biomas Amazônico, Pantaneiro e Cerrado do Estado de Mato Grosso. A detecção de anticorpos para AIE foi realizada em 886 soros pela prova de Imunodifusão em Gel de Ágar (IDGA), enquanto que para EEL, EEO e EEV foi realizada em 473 soros pela Microtécnica de Soroneutra-lização viral em culturas de células VERO. Para AIE, 46 (5,1%) equídeos foram positivos, não sendo observados animais positivos da região amazônica e a maior frequência ocorrendo no ambiente do pantanal com 36,6% de animais positivos (P 0,05). Para as encefalites virais, foram detectados 168 (35,5%) equídeos positivos para EEL e 31 (6,5%) para EEV. Não houve soros positivos para EEO. As maiores frequências de animais positivos para EEL foram observadas nos ambientes pantaneiro e amazônico com 45,8% e 62,0%, respectivamente (P 0,05). Os três biomas estudados apresentaram ocorrência similar (P > 0.05) de animais positivos para EEV, com 4,1%, 6,4% e 10,3% para o pantanal, cerrado e amazônia, respectivamente. Embora não apresentando equídeos reagente ao vírus da AIE na região amazônica, a presença de positivos em Mato Grosso encontra-se dentro do relatado no Brasil. O comportamento diferenciado do vírus da EEL e EEV nos três ecossistemas estudados reforça a presença de animais reservatórios, condições ambientais e climáticas que favorecem a proliferação de vetores que propiciam a infecção pelos vírus no Estado de Mato Grosso.

Ocorrência de equídeos soropositivos para os vírus das encefalomielites e anemia infecciosa no estado de Mato Grosso / The occurrence of equids seropositive for encephalomyelitis and infectious anemia virus in Mato Grosso state, Brazil

O presente trabalho determinou a ocorrência de equídeos com sorologia positiva para os vírus das encefalomielites virais dos tipos Leste (EEL), Oeste (EEO) e Venezuelana (EEV) e Anemia Infecciosa (AIE) nos biomas Amazônico, Pantaneiro e Cerrado do Estado de Mato Grosso. A detecção de anticorpos para AIE foi realizada em 886 soros pela prova de Imunodifusão em Gel de Ágar (IDGA), enquanto que para EEL, EEO e EEV foi realizada em 473 soros pela Microtécnica de Soroneutra-lização viral em culturas de células VERO. Para AIE, 46 (5,1%) equídeos foram positivos, não sendo observados animais positivos da região amazônica e a maior frequência ocorrendo no ambiente do pantanal com 36,6% de animais positivos (P < 0,05). Para as encefalites virais, foram detectados 168 (35,5%) equídeos positivos para EEL e 31 (6,5%) para EEV. Não houve soros positivos para EEO. As maiores frequências de animais positivos para EEL foram observadas nos ambientes pantaneiro e amazônico com 45,8% e 62,0%, respectivamente (P < 0,05). Os três biomas estudados apresentaram ocorrência similar (P > 0.05) de animais positivos para EEV, com 4,1%, 6,4% e 10,3% para o pantanal, cerrado e amazônia, respectivamente. Embora não apresentando equídeos reagente ao vírus da AIE na região amazônica, a presença de positivos em Mato Grosso encontra-se dentro do relatado no Brasil. O comportamento diferenciado do vírus da EEL e EEV nos três ecossistemas estudados reforça a presença de animais reservatórios, condições ambientais e climáticas que favorecem a proliferação de vetores que propiciam a infecção pelos vírus no Estado de Mato Grosso.(AU)

The present work evaluated the occurrence of seropositive equids for eastern encephalomyelitis virus (EEE), western encephalomyelitis virus (WEE), Venezuelan encephalomyelitis virus (VEE) and infectious anemia virus (IAV) in the Pantanal, Savannah and Amazon biomes of Mato Grosso State, Brazil. The detection of antibodies against IAV was carried out in 886 sera of equids by the immunodiffusion test, and antibodies against EEE, WEE and VEE were evaluated in 473 sera by the seroneutralization test performed in VERO cells. The results showed 46 IAV seropositive equids (5.1%). No sera was positive in the Amazon region, and the Pantanal biome showed a higher occurrence with 36.6% of seropositives (P < 0.05). No sera was positive for WEE virus and 168 (35.5%) and 31 (6.5%) equids were positive for EEE and VEE respectively. Higher frequencies (P < 0.05) were observed for EEE in the Pantanal and Amazon regions with 45.8% and 62.0% respectively. Regarding EEV, no differences were observed between the Pantanal, Savannah and Amazon regions, presenting 4.1%, 6.4% and 10.3% respectively (P > 0.05). Despite that IAV was not observed in equids from the Amazon, the occurrence of seropositive equids agree with the Brazilian prevalence. The differences of EEE and VEE behavior between biomes reinforce the presence of animal reservoirs, along with environmental and weather characteristics that support vector maintenance, which favor the presence of the viral infection in Mato Grosso State.(AU)