Isolation and Molecular Analysis of a Novel Neorickettsia Species That Causes Potomac Horse Fever (original) (raw)
Related papers
Scientific Reports
this study aims to report the presence of Neorickettsia risticii DnA in blood samples from naturally infected horses in Rio de Janeiro, provide clinicopathological findings related to the infection, and report the phylogenetic diversity of the 16S rDNA of N. risticii in order to evaluate its heterogeneity. Real-time quantitative polymerase chain reaction (qpcR) was performed to investigate the presence of N. risticii in samples collected from horses (n = 187). Five positive samples were found in the molecular screening. Hypoalbuminemia and high levels of creatine kinase and lactate dehydrogenase were the predominant findings in the biochemical analysis. The sequences were similar to those of N. risticii. phylogenetic analysis revealed genotype segregation based on the geographical distribution in the N. risticii sequence clade. Dendrograms constructed with five hypervariable regions revealed that V4 distinguished Neorickettsia at the species level and produced a phylogeny that best represented the phylogeny obtained with the complete 16S rDNA sequence. This is the first report of N. risticii DnA in the blood of Brazilian horses based on sequences deposited in GenBank. further studies are necessary to clarify the epidemiological chain of this vector-borne parasite in order to determine and establish appropriate preventive measures in the equine trading market.
Neorickettsia risticii: causative agent of
2009
Neorickettsia risticii is an obligate intracellular bacterium of the trematodes and mammals. Horses develop Potomac horse fever (PHF) when they ingest aquatic insects containing encysted N. risticii-infected trematodes. The complete genome sequence of N. risticii Illinois consists of a single circular chromosome of 879 977 bp and encodes 38 RNA species and 898 proteins. Although N. risticii has limited ability to synthesize amino acids and lacks many metabolic pathways, it is capable of making major vitamins, cofactors and nucleotides. Comparison with its closely related human pathogen N. sennetsu showed that 758 (88.2%) of protein-coding genes are conserved between N. risticii and N. sennetsu. Four-way comparison of genes among N. risticii and other Anaplasmataceae showed that most genes are either shared among Anaplasmataceae (525 orthologs that generally associated with housekeeping functions), or specific to each genome (>200 genes that are mostly hypothetical proteins). Genes potentially involved in the pathogenesis of N. risticii were identified, including those encoding putative outer membrane proteins, two-component systems and a type IV secretion system (T4SS). The bipolar localization of T4SS pilus protein VirB2 on the bacterial surface was demonstrated for the first time in obligate intracellular bacteria. These data provide insights toward genomic potential of N. risticii and intracellular parasitism, and facilitate our understanding of PHF pathogenesis.
Veterinary Research, 2011
Neorickettsia risticii is the Gram-negative, obligate, and intracellular bacterial pathogen responsible for Potomac horse fever (PHF): an important acute systemic disease of horses. N. risticii surface proteins, critical for immune recognition, have not been thoroughly characterized. In this paper, we identified the 51-kDa antigen (P51) as a major surface-exposed outer membrane protein of older and contemporary strains of N. risticii through mass spectrometry of streptavidin-purified biotinylated surface-labeled proteins. Western blot analysis of sera from naturally-infected horses demonstrated universal and strong recognition of recombinant P51 over other Neorickettsia recombinant proteins. Comparisons of amino acid sequences for predicted secondary structures of P51, as well as Neorickettsia surface proteins 2 (Nsp2) and 3 (Nsp3) among N. risticii strains from horses with PHF during a 26-year period throughout the United States revealed that the majority of variations among strain...
Journal of Clinical Microbiology, 2004
The p51 gene that encodes the major antigenic 51-kDa protein in Neorickettsia risticii was identified in strains of Neorickettsia sennetsu and the Stellantchasmus falcatus agent but not in Neorickettsia helminthoeca, suggesting that p51-based diagnosis would be useful to distinguish among them. groESL sequencing results delineated the phylogenic relationships among Neorickettsia spp. Neorickettsia spp. are obligatory intracellular bacteria and belong to the family Anaplasmataceae, in the order Rickettsiales. Currently, three species are recognized in the genus Neorickettsia, namely, N. risticii, N. sennetsu, and N. helminthoeca (4). The ecology and transmission of Neorickettsia spp. are unique among bacteria, in that this agent parasitizes both trematodes and mammals (17, 18). In mammals, these bacteria reside within cytoplasmic vacuoles, primarily in monocytes in the blood and in macrophages of lymphoid or other tissues, and they can cause systemic diseases. N. helminthoeca causes salmon poisoning disease, an acute and highly fatal disease of domestic and wild canidae (17). N. risticii causes Potomac horse fever, an acute diarrheal disease of horses (18). N. sennetsu (6, 10) causes human sennetsu rickettsiosis. In addition, the SF agent isolated directly from the metacercaria of Stellantchasmus falcatus trematodes that encyst within gray mullet fish (7, 21, 22) belongs to the genus Neorickettsia. The adult stage of S. falcatus can parasitize the human intestine (8). Despite the wide environmental distribution of Neorickettsia spp. and their importance to public health and veterinary medicine, few molecular and antigenic markers have been identified for this group of bacteria. N. risticii, N. sennetsu, SF agent, and N. helminthoeca are antigenically cross-reactive, and inoculation with N. sennetsu protects horses from Potomac horse fever (15, 21). However, other than approximate molecular sizes, the nature of these cross-reacting antigens is unknown. A 51-kDa protein (P51) is the major antigen recognized in horses with Potomac horse fever (19). P51 is encoded by the p51 gene, which is not found in any other bacteria based on a search of the GenBank database, and has been found in all N. risticii strains identified to date (2, 5, 9, 11).
Potomac horse fever in Ontario: Clinical, geographic, and diagnostic aspects
The Canadian veterinary journal = La revue veterinaire canadienne, 2021
Clinical findings, geographic locations, laboratory diagnoses, and culture isolation of Neorickettsia spp. in Potomac horse fever (PHF) cases diagnosed in Ontario between 2015 and 2019 are described. Forty-six confirmed PHF cases occurred from late June to early September. Of 41 horses admitted to the Ontario Veterinary College, 28 (68%) survived and 13 (32%) were euthanized due to poor prognosis or financial constraints. Most cases were in southern Ontario along the Canada-USA border. Blood and fecal samples from 43 suspect PHF cases were submitted to 2 laboratories for polymerase chain reaction (PCR) testing for Neorickettsia risticii. Agreement between both laboratories for detection of N. risticii DNA was excellent for feces [κ = 0.932, 95% confidence interval (CI): 0.80 to 1], and fair for blood samples (κ = 0.494, 95% CI: 0.13 to 0.85). Neorickettia spp. were isolated from 16 of 41 (39%) blood samples. DNA analysis confirmed 14 isolates were N. risticii and 2 were N. findlayen...
Two cases of Neorickettsia (Ehrlichia) risticii infection in horses from Nova Scotia
The Canadian veterinary journal. La revue vétérinaire canadienne, 2004
Two horses from Nova Scotia were diagnosed with Potomac horse fever (PHF). Polymerase chain reaction analysis was performed on formalin-fixed colon tissue or whole blood to show the presence of Neorickettsia risticii DNA, the causative agent of PHF. These are the first reported cases of PHF in the Maritime Provinces.
Epidemiological survey of Neorickettsia risticii in equids from the State of Rio de Janeiro, Brazil
Pesquisa Veterinária Brasileira, 2016
ABSTRACT: Equine neorickettsiosis (EN), also known as Potomac Horse Fever, is a non-contagious disease caused by the bacterium Neorickettsia risticii of the Anaplasmataceae family. The objectives of this study were to detect the presence of anti-N. risticii antibodies by the indirect immunofluorescence assay (IFA) and of its DNA by qPCR in equids at high and low altitude regions in the State of Rio de Janeiro, Brazil, and to identify factors associated with seropositive equids by multiple logistic regression analysis. The frequency of anti-N. risticii antibodies was 16.05% (n=113/704). The animal age and breeding region were the factors that influenced the seropositivity rate for N. risticii in the equids (p<0.05). Equids from the lowland region had higher seropositivity (p<0.05; OR=5.87) compared to those of the mountain region. The presence of snails on the farm was a factor associated with this result (p<0.05; OR=2.88). In the lowland region, age of the animal and site o...