Serological evidence of Ehrlichia minasensis infection in Brazilian dogs

Ehrlichia Species in Dromedary Camels (Camelus dromedarius) and Ruminants from Somalia

Ehrlichioses, caused by Ehrlichia species, are tick-borne diseases (TBDs) that affect animals and humans worldwide. This study aimed to investigate the molecular occurrence of Ehrlichia spp. in 530 animals (155 Dromedary camels, 199 goats, 131 cattle, and 45 sheep) in the Benadir and Lower Shabelle regions of Somalia. Blood DNA samples were tested for PCR targeting dsb and sodB genes of Ehrlichia spp. and PCS20 and map1 genes of E. ruminantium. The obtained sequences were submitted for phylogenetic analyses. Ehrlichia spp. were detected in 26.4% (140/530) of animals by dsb-PCR, with the highest prevalence in dromedary camels (54.8%), followed by cattle (29.8%), goats (7.0%), and sheep (4.4%). Dromedary camels, cattle, and goats had significantly higher infection odds compared to sheep (p < 0.05). Among dsb-PCR-positive samples, 76.9% (30/39) of cattle tested sodB-positive, while other species were negative. E. ruminantium was detected in 13.7% (18/131) of cattle by pCS20-PCR, but none were positive for the map1 gene. Phylogenetic analysis confirmed E. minasensis in camels, sheep, and goats and E. ruminantium in cattle, marking the first molecular evidence of E. minasensis in dromedary camels, sheep, and goats globally, and E. ruminantium in cattle from Somalia. These findings emphasize the need for further research on its economic and public health impact.

Ehrlichia sp. in dairy cattle from Bahia, Brazil: high seropositivity rates and molecular confirmation of Ehrlichia minasensis

BACKGROUND

Ehrlichia spp. are obligate intracytoplasmic Gram-negative tickborne bacteria from the Anaplasmataceae family. Ehrlichiosis is considered an emerging disease in humans and animals. Studies on bovine ehrlichiosis are scarce in Northeastern Brazil. Therefore, the objectives of this work were to determine the frequency of antibodies anti-Ehrlichia sp. in dairy cattle herds in the Feira de Santana microregion, Bahia, and to confirm infection through PCR and nucleotide sequencing in selected seropositive animals.

RESULTS

Blood samples were collected from 256 clinically healthy adult cattle from four dairy farms. Plasma from each animal was tested for Ehrlichia sp. using an indirect immunofluorescence antibody test (IFAT) and a 1:40 cutoff. Of the 256 tested samples, 249 (97.26%) were seropositive for Ehrlichia sp. Forty blood samples (10 from each farm) from IFAT-positive cattle were examined by a PCR for Ehrlichia sp. and resulted in 13 infected animals; DNA samples from six PCR-positive cows were sequenced and matched 100% with Ehrlichia minasensis.

CONCLUSIONS

The results represent the first serological and molecular evidence of E. minasensis in cattle from Bahia state and northeastern Brazil. Despite the limited number of tested cattle, the high frequency of seropositive animals in four farms suggests that Ehrlichia sp. is widely disseminated in the studied microregion. Considering that the infected cattle were asymptomatic, it is possible that they developed protective immunity against Ehrlichia sp.

Molecular detection and characterization of Anaplasmataceae agents, Bartonella spp. and hemoplasmas in armadillos and anteaters from Brazil

Armadillos and anteaters exhibit a wide range of interactions with various pathogens and ectoparasites, which, along with their physiological and ecological characteristics, contribute to their potential as hosts for a broad variety of pathogens with zoonotic potential. However, there has been limited research into the occurrence and diversity of vector-borne agents in this group of mammals. The present study aimed to investigate the occurrence and molecular identity of Ehrlichia spp., Anaplasma spp., Bartonella spp. and hemotropic mycoplasmas (hemoplasmas) in free-ranging armadillos and anteaters sampled in the southeast and central-west regions of Brazil. To this purpose, 167 biological samples (139 blood and 28 spleen) from Xenarthra mammals sampled in the states of São Paulo and Mato Grosso do Sul were analyzed: 48 from six-banded armadillos (Euphractus sexcinctus), 29 from giant armadillos (Priodontes maximus), 4 from nine-banded armadillos (Dasypus novemcinctus), 1 from naked-tailed armadillo (Cabassous unicinctus), 79 from giant anteaters (Myrmecophaga tridactyla) and 6 from southern tamanduas (Tamandua tetradactyla). Screening PCR assays were performed for Ehrlichia spp. based on the dsb gene, nested PCR for Anaplasma spp. and PCR for hemotropic mycoplasmas based on the 16S rRNA gene, and qPCR for Bartonella spp. based on the 16-23S rRNA intergenic region (ITS). The positive samples were additionally subjected to PCR assays targeting different molecular markers for molecular characterization. As a result, 1/48 (0.59%) blood sample from E. sexcintus was positive for Anaplasma spp., and 1/79 (0.59%) blood sample from M. tridactyla was positive for Ehrlichia spp. The 16S rRNA sequence of Anaplasma sp. detected in E. sexcintus clustered within the same clade as 'Candidatus Anaplasma brasiliensis', previously detected in T. tetradactyla. The dsb sequence of Ehrlichia sp. detected in M. tridactyla clustered within the same clade as Ehrlichia minasensis. In the PCR tests for hemoplasmas, 31/46 (64.5%) E. sexcinctus, 9/29 (65.5%) P. maximus, 2/4 (50%) D. novemcinctus, 33/79 (41.7%) M. tridactyla, and 2/6 (33.3%) T. tetradactyla tested positive. The 16S rRNA and 23S rRNA sequences of hemoplasmas found in E. sexcinctus clustered within the same clade as 'Candidatus Mycoplasma haematomaximus', which was previously detected in P. maximus in Brazil. High positivity rates were also observed for Bartonella spp., with 23/48 (47.9%) E. sexcinctus, 1/4 (25%) D. novemcinctus, 9/29 (31%) P. maximus, 21/79 (26.5%) M. tridactyla, and 3/6 (50%) T. tetradactyla showing positive results. The ftsZ sequences of Bartonella sp. detected in E. sexcinctus clustered with 'Candidatus Bartonella washoensis subsp. brasiliensis', previously identified in six-banded armadillos in Brazil. These findings reinforce the presence of 'Candidatus Anaplasma brasiliensis' and 'Candidatus Bartonella washoensis subsp. brasiliensis' in armadillos, and Ehrlichia minasensis in anteaters. This is the first report of 'Candidatus Mycoplasma haematomaximus', a hemoplasma previously described in giant armadillos, in six-banded armadillos. The zoonotic potential and real significance of infection by these agents in xenarthrans' health and conservation efforts are yet to be investigated.

Scientometric mapping of the trends, impact, and thematic evolution of scientific production on ehrlichiosis in veterinary medicine

Background and Aim

This study focuses on the scientific output of ehrlichiosis, a tick-borne disease that affects a variety of animal species, including dogs, cats, and livestock. Therefore, this study aimed to perform a scientometric mapping of the trends, impact, and thematic evolution of scientific production on ehrlichiosis in veterinary medicine.

Materials and Methods

The study design was descriptive and observational, with a quantitative scientometric approach. This study was based on Scopus data collection and analysis from 2018 to 2023. A literature search was conducted on February 12, 2024, and a total of 200 documents were found, of which 177 were articles, 15 book chapters, and eight reviews. A specific search formula was used to obtain documents. The documents were analyzed using SciVal and Bibliometrix in R Studio, focusing on four key metrics: Scholarly Output, View Count, Field-Weighted Citation Impact, and Citation Count.

Results

This bibliometric study covered the period from 2018 to 2023 and analyzed 200 papers from 84 different sources. The average number of citations was 3595 and the mean age was 3.17 years. A total of 1874 keywords and 1085 authors were identified, with an average of 6.25 co-authors per paper. International co-authorship was present in 23% of the papers. The papers were distributed as articles (177), book chapters (15), and reviews (8).

Conclusion

The combination of these metrics enabled a more complete and accurate assessment of research performance. A total of 1874 keywords and 1085 authors were identified. The thematic evolution from "canine ehrlichiosis" and "Ehrlichia canis" to "dog" and "canine" was observed. Bradford's and Lotka's laws were confirmed, with some sources and authors generating most publications.

Molecular screening of tick-borne microorganisms in ticks from rural areas of Panama, with the first record of Ehrlichia minasensis in Rhipicephalus microplus from Central America

During a molecular screening of rickettsial, borrelial and protozoal agents in ticks from rural areas of Panama, we detected DNA of Rickettsia amblyommatis in four Amblyomma mixtum collected from horses in a locality in Los Santos province. Ehrlichia minasensis and Anaplasma marginale were identified from three and two Rhipicephalus microplus, respectively, collected on cows from Chiriqui province. No DNA from other tick-borne agents was found. These results increase the information of R. amblyommatis and A. marginale in Panama, and also mark the first record of E. minasensis in Central America.

Molecular Detection of Tick-Borne Pathogens in Dogs from Indigenous Communities, Amazon, Brazil

Background: There are few reports of tick-borne pathogens infecting dogs living in indigenous communities of Brazil. Herein, we aimed to molecularly detect vector-borne pathogens in dogs from two indigenous communities in the Brazilian Amazon. Materials and Methods: We surveyed 327 dogs raised in Amazon region at 2 distinct indigenous ethnicities for the molecular detection of tick-borne pathogens (114 from Tapirapé and 213 from Karajá indigenous ethnicity). Whole blood samples were subjected to PCR and sequencing for Ehrlichia, Babesia, and Hepatozoon. Univariate and multivariate analyses were used to investigate the factors affecting the pathogen infection patterns in dogs. Results: Among the 327 blood samples, 40 were positive for Ehrlichia canis (12.2%), 2 for Anaplasma platys (0.61%), and 204 were positive for Hepatozoon canis (66.5%). Binary Logistic Regression showed association between E. canis infection and ethnicity (p = 0.010) and tick attachment (p = 0.041). Karajá dogs were 3.4 times (95% CI 1.3-8.5) more likely to be positive for E. canis than Tapirapé dogs. Dogs with ticks were 2.5 times more likely (95% CI 1.0-7.6) to be positive for E. canis than dogs without ticks. Conclusions: Our survey expands the knowledge regarding the presence of vector-borne pathogens in dogs from indigenous communities in the Amazon region.

Serological Evidence Supporting the Occurrence of Ehrlichia chaffeensis or a Closely Related Species in Brazilian Dogs

Ehrlichia chaffeensis is a tick-borne bacterium that causes human monocytotropic ehrlichiosis, an emerging life-threatening disease in humans transmitted by Amblyomma americanum. Although most studies have reported bacterial isolations and clinical cases in the United States, their occurrence is not restricted to North America. Some studies in the Southern Cone of South America have molecularly detected a close phylogenetic relative of E. chaffeensis in ticks and wild mammals. Even so, many gaps must be filled to confirm the presence of this agent in the region. To add new data on this issue, we report the first detection of specific anti-E. chaffeensis antibodies in dogs collected from all regions of Brazil. By means of IFA and ELISA with crude and specific antigens of E. chaffeensis, sera from 1134 dogs were analyzed. Serological analyses using ELISA showed nine (0.7%) seropositive dogs, with seven of them exhibiting IFA titers ranging from 160 to 5120. All regions of Brazil had at least one seropositive dog. Our results support the evidence for the occurrence of E. chaffeensis in South America. As dogs have a close relationship with humans, they can be used as an environmental sentinel for these infections because they can act as a bridge to human parasitism or infection with ehrlichial agents.

Cuticular Lipids as a First Barrier Defending Ixodid Ticks against Fungal Infection

The chemical composition of tick cuticles acts as a barrier to pathogens and may limit infection by entomopathogenic fungi. This study characterized the cuticular neutral lipids (NL) and hydrocarbons (HCs) of four ixodid ticks that are widely distributed in Brazil. HC extracts were analyzed by gas chromatography-mass spectrometry and used to challenge Beauveria bassiana IP361 and Metarhizium robertsii IP146; the effect of cuticular extracts in fungal growth were evaluated by disk diffusion and conidial viability assays. In addition, conidial germination on the tick cuticle was evaluated by scanning electron microscopy, and NL from ticks treated with fungi were assessed by thin layer chromatography. Six HCs were exclusively identified in Amblyomma sculptum. Additionally, cuticle extracts from Dermacentor nitens and A. sculptum inhibited the growth of M. robertsii IP146 and reduced conidial germination of B. bassiana IP361 to 70% and 49%, respectively; the same extracts also produced cytotoxic effects, with conidial death above 30% and 60%. Electron micrographs showed a delayed germination of conidia incubated for 48 h or 72 h on D. nitens and A. sculptum. The lipid profile of A. sculptum treated with fungi was not significantly altered; triacylglycerol was not detected in the cuticle extracts of any other tick species. Finally, A. sculptum and D. nitens cuticles have lipid components that may limit the development of M. robertsii.

Metagenomics of the midgut microbiome of Rhipicephalus microplus from China

Background

Ticks, which are ectoparasites of animals, may carry multiple pathogens. The cattle tick Rhipicephalus microplus is an important bovine parasite in China. However, the midgut microbiome of R. microplus from China has not been characterized via metagenomic methods.

Methods

Rhipicephalus microplus were collected from cattle in the city of Changsha in Hunan province, China. The DNA of the midgut contents was extracted from fully engorged adult female R. microplus. A DNA library was constructed and sequenced using an Illumina HiSeq sequencing platform. SOAPdenovo software was used to assemble and analyze the clean data. The latent class analysis algorithm applied to system classification by MEGAN software was used to annotate the information on the species’ sequences. DIAMOND software was used to compare unigenes with the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, and functional annotation was carried out based on the results of the comparison.

Results

The dominant phyla in the five samples were Firmicutes, Proteobacteria, and Actinobacteria. Streptococcus, Mycobacterium, Anaplasma, Enterococcus, Shigella, Lactobacillus, Brachyspira, Pseudomonas, Enterobacter, Bacillus, and Lactococcus were the dominant genera in the five samples. The endosymbiotic bacterium Wolbachia was also detected in all of the samples. Mycobacterium malmesburyense, Streptococcus pneumoniae, Anaplasma phagocytophilum, Enterococcus faecium, Shigella sonnei, Enterococcus faecalis, Lactobacillus casei, Brachyspira hampsonii, Pseudomonas syringae, Enterobacter cloacae, and Lactococcus garvieae were the dominant species in the five samples. In addition to these bacterial species, we also detected some eukaryotes, such as Rhizophagus irregularis, Enterospora canceri, Smittium culicis, Zancudomyces culisetae, Trachipleistophora hominis, and viruses such as orf virus, human endogenous retrovirus type W, enzootic nasal tumor virus of goats, bovine retrovirus CH15, and galidia endogenous retrovirus in all of the samples at the species level. The results of the annotated KEGG pathway predictions for the gene functions of the midgut microflora of R. microplus indicated genes involved in lipid and amino acid metabolism, infectious diseases (e.g., Streptococcuspneumonia infection, human granulocytic anaplasmosis, Shigellasonnei infection, Salmonella enterica infection, and pathogenic Escherichia coli infection), and cancer.

Conclusions

Our study revealed that the midgut microbiome of R. microplus is not only composed of a large number of bacteria, but that a portion also comprises eukaryotes and viruses. The data presented here enhance our understanding of this tick’s midgut microbiome and provide fundamental information for the control of ticks and tick-borne diseases.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05161-6.