Prevalence of vector-borne bacterial pathogens in riparian brush rabbits (Sylvilagus bachmani riparius) and their ticks

Newly Recognized Spotted Fever Group Rickettsia as Cause of Severe Rocky Mountain Spotted Fever-Like Illness, Northern California, USA

The incidence of spotted fever group (SFG) rickettsioses in the United States has tripled since 2010. Rocky Mountain spotted fever, the most severe SFG rickettsiosis, is caused by Rickettsia rickettsii. The lack of species-specific confirmatory testing obfuscates the relative contribution of R. rickettsii and other SFG Rickettsia to this increase. We report a newly recognized rickettsial pathogen, Rickettsia sp. CA6269, as the cause of severe Rocky Mountain spotted fever-like illness in 2 case-patients residing in northern California. Multilocus sequence typing supported the recognition of this pathogen as a novel Rickettsia genotype most closely related to R. rickettsii. Cross-reactivity observed for an established molecular diagnostic test indicated that Rickettsia sp. CA6269 might be misidentified as R. rickettsii. We developed a Rickettsia sp. CA6269-specific real-time PCR to help resolve this diagnostic challenge and better characterize the spectrum of clinical disease and ecologic epidemiology of this pathogen.

Occurrence of Anaplasma spp. in wild lagomorphs from Southern Spain: Molecular detection of new Anaplasma bovis lineages

Wild lagomorphs can act as reservoirs of several pathogens of public and animal health concern. However, the number of studies assessing the presence of Anaplasma spp. in these species is scarce. The aim of the present study was to molecularly identify Anaplasma spp. in wild rabbits (Oryctolagus cuniculus) and Iberian hares (Lepus granatensis) from Southern Spain and assess their epidemiological role in the maintenance of the bacterium. During 2017-2021, spleen samples of 394 wild rabbits and 145 Iberian hares were collected. Anaplasma DNA was detected using different PCR assays (16S rRNA and groEL) and phylogenetic analyses were carried out by Bayesian approach. The possible influence of lagomorph species, age and sex on the prevalence of Anaplasma spp. was evaluated by a multiple logistic regression model. The 9.4% of the rabbits were positive to Anaplasma bovis, but all the hares were negative. No significant differences were found in Anaplasma spp. prevalence regarding to age or sex. This is the first report of A. bovis in lagomorphs from Europe. The phylogenetic analysis of A. bovis confirms the existence of different clusters suggesting the existence of several lineages. In addition, a high divergence of nucleotide identity was observed within the lineage 4, which could result in the under-detection of some strains when using A. bovis-specific PCR, hindering its detection and characterization. Since this analysis is based on a limited number of nucleotide bases and sequences, more studies are needed for further characterize A. bovis, as well as its relationship with other Anaplasma spp.

Emerging rodent-associated Bartonella: a threat for human health?

Background

Species of the genus Bartonella are facultative intracellular alphaproteobacteria with zoonotic potential. Bartonella infections in humans range from mild with unspecific symptoms to life threatening, and can be transmitted via arthropod vectors or through direct contact with infected hosts, although the latter mode of transmission is rare. Among the small mammals that harbour Bartonella spp., rodents are the most speciose group and harbour the highest diversity of these parasites. Human–rodent interactions are not unlikely as many rodent species live in proximity to humans. However, a surprisingly low number of clinical cases of bartonellosis related to rodent-associated Bartonella spp. have thus far been recorded in humans.

Methods

The main purpose of this review is to determine explanatory factors for this unexpected finding, by taking a closer look at published clinical cases of bartonellosis connected with rodent-associated Bartonella species, some of which have been newly described in recent years. Thus, another focus of this review are these recently proposed species.

Conclusions

Worldwide, only 24 cases of bartonellosis caused by rodent-associated bartonellae have been reported in humans. Possible reasons for this low number of cases in comparison to the high prevalences of Bartonella in small mammal species are (i) a lack of awareness amongst physicians of Bartonella infections in humans in general, and especially those caused by rodent-associated bartonellae; and (ii) a frequent lack of the sophisticated equipment required for the confirmation of Bartonella infections in laboratories that undertake routine diagnostic testing. As regards recently described Bartonella spp., there are presently 14 rodent-associated Candidatus taxa. In contrast to species which have been taxonomically classified, there is no official process for the review of proposed Candidatus species and their names before they are published. This had led to the use of malformed names that are not based on the International Code of Nomenclature of Prokaryotes. Researchers are thus encouraged to propose Candidatus names to the International Committee on Systematics of Prokaryotes for approval before publishing them, and only to propose new species of Bartonella when the relevant datasets allow them to be clearly differentiated from known species and subspecies.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05162-5.

Wild Rabbit Exposure to Leishmania infantum, Toxoplasma gondii, Anaplasma phagocytophilum and Babesia caballi Evidenced by Serum and Aqueous Humor Antibody Detection

Wild rabbits (Oryctolagus cuniculus) can be important sentinel species for the presence of zoonotic pathogens. Therefore, we collected blood samples from wild rabbits harvested by hunters during the hunting season 2019–2020 on the island of Lemnos, to determine exposure of wild rabbits to the zoonotic pathogens Leishmania infantum, Toxoplasma gondii, Anaplasma phagocytophilum and Babesia caballi, as well as aqueous humor to assess its diagnostic performance in terms of sensitivity, specificity, positive and negative likelihood ratios. Antibodies against these pathogens were detected by Indirect Immunofluorescence Antibody (IFA) assay. Out of the 72 wild rabbits included in the study, 4.2%, 5.5%, 18% and 9.7% were seropositive to L. infantum, T. gondii, A. phagocytophilum and B. caballi, respectively. Although less frequently, antibodies were also detected in aqueous humor of wild rabbits. The antibody detection in aqueous humor presented 100% specificity but decreased sensitivity compared to serum suggesting that aqueous humor could be successfully used in epidemiological studies to confirm exposure at the population level but has little diagnostic value at the individual level. This is the first report on the seropositivity of wild rabbits to A. phagocytophilum and B. caballi and the detection of antibodies against A. phagocytopylum, L. infantum, T. gondii and B. caballi in the aqueous humor.

Longitudinal Study of Bacterial Infectious Agents in a Community of Small Mammals in New Mexico

Background and Objectives: Vector-borne bacterial diseases represent a substantial public health burden and rodents have been recognized as important reservoir hosts for many zoonotic pathogens. This study investigates bacterial pathogens in a small mammal community of the southwestern United States of America. Methods: A total of 473 samples from 13 wild rodent and 1 lagomorph species were tested for pathogens of public health significance: Bartonella, Brucella, Yersinia, Borrelia, Rickettsia spp., and Anaplasma phagocytophilum. Results: Three animals were positive for Yersinia pestis, and one Sylvilagus audubonii had a novel Borrelia sp. of the relapsing fever group. No Brucella, Rickettsia, or A. phagocytophilum infections were detected. Bartonella prevalence ranged between 0% and 87.5% by animal species, with 74.3% in the predominant Neotoma micropus and 78% in the second most abundant N. albigula. The mean duration of Bartonella bacteremia in mark-recaptured N. micropus and N. albigula was 4.4 months, ranging from <1 to 18 months, and differed among Bartonella genogroups. Phylogenetic analysis of the Bartonella citrate synthase gene (gltA) revealed 9 genogroups and 13 subgroups. Seven genogroups clustered with known or previously reported Bartonella species and strains while two were distant enough to represent new Bartonella species. We report, for the first time, the detection of Bartonella alsatica in North America in Sylvilagus audubonii and expand the known host range of Bartonella washoensis to include Otospermophilus variegatus. Interpretation and Conclusion: This work broadens our knowledge of the hosts and geographic range of bacterial pathogens that could guide future surveillance efforts and improves our understanding of the dynamics of Bartonella infection in wild small mammals.

Investigation of the Role of the European Brown Hare in the Epidemiology of Bacterial Zoonotic Pathogens: A Serological and Molecular Survey in Greece

The aim of this study was to investigate the occurrence of Bartonella spp, Brucella spp, Coxiella burnetii, and Francisella tularensis in European Brown hares (Lepus europaeus) hunter harvested during 2-year hunting periods in northern and central Greece. Serum samples were examined for the presence of IgG antibodies by using an immune fluorescence test and/or an enzyme-linked immunosorbent assay. PCR was used to detect Bartonella spp DNA in blood samples and Brucella spp, C. burnetii, and F. tularensis DNA in liver samples. Antibodies against Bartonella spp were detected in 12 hares (12/105); whereas none of the hares examined was seropositive for Brucella spp, C. burnetii, and F. tularensis. The presence of Bartonella spp, Brucella spp, C. burnetii, and F. tularensis DNA was not detected in the samples examined. This study did not provide any evidence that the European Brown hare is involved in the epidemiology of Brucella spp, C. burnetii, and F. tularensis in Greece. However, our results suggest that this species is exposed to Bartonella spp, which gives the impetus for further investigation of its role as another host of this bacterium.

Molecular survey on the occurrence of arthropod-borne pathogens in wild brown hares (Lepus europaeus) from Central Italy

Data about the spreading of arthropod-borne pathogens among hare populations are very scant, so the aim of the present preliminary study was to investigate, through molecular analysis, the occurrence of Anaplasma phagocytophilum, Bartonella sp., Borrelia burgdorferi sensu lato, Coxiella burnetii, Francisella tularensis, Leishmania spp. and piroplasms DNA in blood of 51 wild hares (Lepus europaeus) living in protected areas in Tuscany. All hares resulted negative for A. phagocytophilum, Bartonella sp., B. burgdorferi s.l., C. burnetii and F. tularensis. Five animals (9.8%) were positive for Leishmania and one hare (1.9%) tested positive for piroplasms. Sequencing of this sample showed a piroplasm similar to one Babesia isolate from the same animal species in Turkey. Therefore, to the best of our knowledge, this is the first molecular report of piroplasms occurring in wild hares from Italy, and the second worldwide. The examined hares appeared to be in good health status, corroborating the hypothesis of a chronic carrier state of some vector borne agents for this animal species.

A Molecular Survey for Francisella tularensis and Rickettsia spp. in Haemaphysalis leporispalustris (Acari: Ixodidae) in Northern California

Francisella tularensis and Rickettsia spp. have been cultured from Haemaphysalis leporispalustris Packard, but their prevalence in this tick has not been determined using modern molecular methods. We collected H. leporispalustris by flagging vegetation and leaf litter and from lagomorphs (Lepus californicus Gray and Sylvilagus bachmani (Waterhouse)) in northern California. Francisella tularensis DNA was not detected in any of 1,030 ticks tested by polymerase chain reaction (PCR), whereas 0.4% of larvae tested in pools, 0 of 117 individual nymphs, and 2.3% of 164 adult ticks were PCR-positive for Rickettsia spp. Positive sites were Laurel Canyon Trail in Tilden Regional Park in Alameda Contra Costa County, with a Rickettsia spp. prevalence of 0.6% in 2009, and Hopland Research and Extension Center in Mendocino County, with a prevalence of 4.2% in 1988. DNA sequencing revealed R. felis, the agent of cat-flea typhus, in two larval pools from shaded California bay and live oak leaf litter in Contra Costa County and one adult tick from a L. californicus in chaparral in Mendocino County. The R. felis in unfed, questing larvae demonstrates that H. leporispalustris can transmit this rickettsia transovarially. Although R. felis is increasingly found in diverse arthropods and geographical regions, prior literature suggests a typical epidemiological cycle involving mesocarnivores and the cat flea, Ctenocephalides felis. To our knowledge, this is the first report of R. felis in H. leporispalustris. Natural infection and transovarial transmission of this pathogen in the tick indicate the existence of a previously undocumented wild-lands transmission cycle that may intersect mesocarnivore-reservoired cycles and collectively affect human health risk.

New host records of Haemaphysalis leporispalustris (Acari: Ixodidae) on birds in Brazil

Birds are an important component of the life histories and bioecology of a number of tick species and of some tick associated pathogens. An examination of the data concerning bird/tick associations in the Neotropics, showed that the tick Haemaphysalis leporispalustrisis (Packard, 1869) was rarely recorded infesting birds. The current study reports parasitism by H. leporispalustris in wild birds collected from Atlantic rain forest environments in the states of Rio de Janeiro (4LL) and Minas Gerais (17LL, 1NN), Brazil. All ticks were identified morphologically to the genus level; total DNA was extracted from each Haemaphysalis tick and examined by PCR and nucleotide sequencing of fragments of the eukaryotic genes encoding 16S rRNA and 12S rRNA. The bird species Arremon semitorquatus, Corythopis delalandi, Fluvicola nengeta, Troglodytes musculus, and Volatinia jacarina were recorded as hosts for H. leporispalustris for the first time in South America, and Turdus rufiventris represented a new record for Brazil.