Vector-borne Bacterial Pathogens Research Articles

Molecular Survey of Vector-Borne Pathogens in Ticks, Sheep Keds, and Domestic Animals from Ngawa, Southwest China.

Vector-borne pathogens are mainly transmitted by blood-feeding arthropods such as ticks, mosquitoes, fleas, lice, mites, etc. They pose a significant threat to animal and human health due to their worldwide distribution. Although much work has been performed on these pathogens, some neglected areas and undiscovered pathogens are still to be further researched. In this study, ticks (Haemaphysalis qinghaiensis), sheep keds (Melophagus ovinus), and blood samples from yaks and goats were collected in Ngawa Tibetan and Qiang Autonomous Prefecture located on the eastern edge of the Qinghai–Tibet Plateau, Southwest China. Several vector-borne bacterial pathogens were screened and studied. Anaplasma bovis strains representing novel genotypes were detected in ticks (8.83%, 37/419), yak blood samples (45.71%, 64/140), and goat blood samples (58.93%, 33/56). Two spotted fever group (SFG) Rickettsiae, Candidatus Rickettsia jingxinensis, and a novel Rickettsia species named Candidatus Rickettsia hongyuanensis were identified in ticks. Another Rickettsia species closely related to the Rickettsia endosymbiont of Polydesmus complanatus was also detected in ticks. Furthermore, a Coxiella species was detected in ticks (3.34%, 14/419), keds (1.89%, 2/106), and yak blood (0.71%, 1/140). Interestingly, another Coxiella species and a Coxiella-like bacterium were detected in a tick and a goat blood sample, respectively. These results indicate the remarkable diversity of vector-borne pathogens circulating in this area. Further investigations on their pathogenicity to humans and domestic animals are still needed.

Molecular detection of vector-borne bacterial pathogens in dromedary camels from Algeria

Background: In Algeria, little focus was placed on camels as hosts of tick-borne bacterial diseases. Recent studies showed a high prevalence of tick infestation in dromedaries. Transmission of various pathogenic micro organisms to camels by ticks imposes considerable economic losses to livestock and greatly impact on human and animal health. The aim of our study was to investigate the occurrence of vector-borne zoonotic bacteria in camels from Algeria.
 Methodology: Blood samples were collected from 80 randomly selected camels in Laghouat province, southern Algeria. The samples were screened for Anaplasma spp, Bartonella spp, Rickettsia spp and Coxiella burnetii by qPCR. All positive samples were confirmed by standard PCR followed by sequencing. Data on age, sex, tick infestation and location of the camels were analyzed using the SPSS version 17.0 and association of these with vector-borne bacterial pathogens was determined using Chi-square (χ2) test. P value lower than 0.05 wasconsidered as indicative of significance.
 Results: Twenty five of the 80 (31.3%) camels were positive to at least one vector-borne bacterial pathogen with Anaplasma phagocytophilum (22.5%, 18/80) being the most prevalent species, followed by Anaplasma platys (7.5%, 6/80) and Bartonella dromedarii (2.5%, 2/80). Only one camel was co-infected with two pathogens. All samples tested negative for Rickettsia spp and Coxiella burnetii. None of the factors (age, sex, tick infestation and study sites) was significantly associated with prevalence of vector-borne bacteria in the camels (p>0.05).
 Conclusion: The present study is the first report of anaplasmosis and bartonellosis in "Camelus dromedaries" from Algeria. Our results highlighted the need for further investigations on tickborne pathogens of camels.

Seroprevalence and epidemiology of typhus group Rickettsia infection in Texas

Background: Typhus group Rickettsia (TGR) are a subgroup of vector-borne bacterial pathogens in the genus Rickettsia. Flea-borne TGR rickettsiosis in humans is most often caused by R. typhi. Clinical disease characteristically presents as fever, rash, headache, nausea, and vomiting, making it difficult to distinguish clinically from other flu-like syndromes. If left untreated or with delayed treatment, severe and life-threatening disease can develop. TGR is a growing public health concern in Texas, where surveillance data indicates increasing incidence of flea-borne rickettsiosis, from 157 reported cases in 2008 to 738 in 2018. Fleas that transmit TGR take bloodmeals from a variety of mammalian species, including farm, wild, and domestic animals. For this reason, individuals with frequent animal contact or who engage in outdoor activities with abundant wildlife could be at heightened risk of TGR exposure. Greater understanding of the local epidemiology in the southern United States, where the ecology is conducive to TGR endemicity, in needed. Methods and materials: As part of an attempt to understand the epidemiology of zoonotic and vector-borne diseases in Texas, we conducted serologic screening among individuals engaged in hunting and/or ranching across the state of Texas, enrolled from 2015 to 2018. Serum was tested for IgG to TGR using a commercial ELISA kit, tested in parallel for IgG to Spotted Fever Group Rickettsia (SFGR), and confirmed by immunofluorescence assay. Utilizing interview data on demographics, behaviors, and other potential exposures, we defined characteristics associated with TGR seropositivity. Results: Among 631 study participants, ages 6 to 81 (median 48) years and 80% male, 35% had IgG against TGR by ELISA. To characterize the local epidemiology, spatial distribution of TGR seropositivity are demonstrated, with hotspot and overlay analyses. Potential risk factors for TGR exposure are reported as odds ratios with 95% confidence intervals. Conclusion: This new evidence of highly prevalent TGR exposure among a presumed high-risk population from across Texas suggests that TGR infections may be going under-recognized and underreported, with higher incidence than previously thought, at least in some groups. These findings can drive targeted educational campaigns to raise awareness about risk factors and disease prevention, facilitate early clinical recognition, and inform surveillance strategies.

Fleas (Siphonaptera) Parasitizing Peridomestic and Indigenous Mammals in Panamá and Screening of Selected Fleas for Vector-Borne Bacterial Pathogens.

In total, 341 fleas belonging to 16 species were collected from 78 host mammals belonging to 10 species in Panamá from 2010 to 2016. The cat flea, Ctenocephalides felis (Bouché) predominated on domestic dogs and was also recorded from domestic cats, the raccoon, Procyon lotor (Linnaeus) and the common opossum, Didelphis marsupialis Linnaeus. The largest number of flea species (7) was recorded from D. marsupialis and the most common flea on that host was the ctenophthalmid, Adoratopsylla intermedia copha Jordan. One Oriental rat flea, Xenopsylla cheopis (Rothschild), was collected from D. marsupialis. Native rodents were parasitized by indigenous ceratophyllid, rhopalopsyllid, and stephanocircid fleas. The Mexican deermouse, Peromyscus mexicanus (Saussure), was parasitized by six species of ceratophyllids belonging to the mostly Central American genera, Baculomeris, Jellisonia, Kohlsia and Plusaetis. The long-tailed singing mouse, Scotinomys xerampelinus (Bangs), was parasitized by Plocopsylla scotinomi Tipton and Méndez, the only species of stephanocircid flea known from Central America. Twenty-six pools of extracted flea DNA representing 5 flea species (C. felis, Pulex echidnophagoides (Wagner), Pulex simulans Baker, A. intermedia copha, and P. scotinomi) and 79 individual fleas were all real-time polymerase chain reaction negative for Rickettsia felis, Rickettsia typhi, and Bartonella henselae.

A Novel Rapid Sample Preparation Method for MALDI-TOF MS Permits Borrelia burgdorferi Sensu Lato Species and Isolate Differentiation.

The genus Borrelia comprises vector-borne bacterial pathogens that can severely affect human and animal health. Members of the Borrelia burgdorferi sensu lato species complex can cause Lyme borreliosis, one of the most common vector-borne diseases in the Northern hemisphere. Besides, members of the relapsing fever group of spirochetes can cause tick-borne relapsing fever in humans and various febrile illnesses in animals in tropical, subtropical and temperate regions. Borrelia spp. organisms are fastidious to cultivate and to maintain in vitro, and therefore, difficult to work with in the laboratory. Currently, borrelia identification is mainly performed using PCR and DNA sequencing methods, which can be complicated/frustrating on complex DNA templates and may still be relatively expensive. Alternative techniques such as matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) are not well established for Borrelia spp., although this technique is currently one of the most used techniques for rapid identification of bacteria in microbiological diagnostic laboratories. This is mainly due to unsatisfactory results obtained by use of simple sample preparation techniques and medium-contamination obscuring the mass spectra. In addition, comprehensive libraries for Borrelia spp. MALDI-TOF MS have yet to be established. In this study, we developed a new filter-based chemical extraction technique that allows measurement of high quality Borrelia spp. spectra from less than 100,000 bacteria per spot in MALDI-TOF MS. We used 49 isolates of 13 different species to produce the largest mass-library for Borrelia spp. so far and to validate the protocol. The library was successfully established and identifies >96% of used isolates correctly to species level. Cluster analysis on the sum spectra was applied to all the different isolates, which resulted in tight cluster generation for most species. Comparative analysis of the generated cluster to a phylogeny based on concatenated multi-locus sequence typing genes provided a surprising homology. Our data demonstrate that the technique described here can be used for fast and reliable species and strain typing within the borrelia complex.

Seroprevalence of viral and vector-borne bacterial pathogens in domestic dogs (Canis familiaris) in northern Botswana.

Domestic dogs (Canis familiaris) have the potential to act as disease reservoirs for wildlife and are important sentinels for common circulating pathogens. Therefore, the infectious disease seroprevalence among domestic dogs in northern Botswana may be indicative of pathogen exposure of various wildlife species. The objective of this study was to assess the seroprevalence of Ehrlichia spp., Borrelia burgdorferi, Anaplasma spp., Dirofilaria immitis, canine adenovirus, canine parvovirus, and canine distemper virus in domestic dogs as proxies of disease prevalence in the local wildlife in the Okavango Delta region of Botswana. Statistical analysis assessed crude and factor-specific seroprevalence proportions in relation to age, sex, and geographical location as predictors of seropositivity. Logistic regression was used to identify adjusted predictors of seropositivity for each of the pathogens of interest. Samples from 233 dogs in a total of seven locations in Maun, Botswana, and surrounding villages were collected and serologically analyzed. No dogs were seropositive for B. burgdorferi, while low seroprevalence proportions were observed for Anaplasma spp. (2.2%) and D. immitis (0.9%). Higher seroprevalence proportions were observed for the tick-borne pathogen Ehrlichia spp. (21.0%), and 19.7% were seropositive for canine adenovirus (hepatitis). The highest seroprevalence proportions were for canine parvovirus (70.0%) and canine distemper virus (44.8%). The predictors of seropositivity revealed that adults were more likely to be seropositive for canine adenovirus, canine distemper virus, and canine parvovirus than juveniles, and location was a risk factor for canine adenovirus, canine distemper virus, canine parvovirus, and Ehrlichia spp. Results indicate that increasing tick control and vaccination campaigns for domestic dogs may improve the health of domestic animals, and potentially wildlife and humans in the Okavango Delta since viral and vector-borne bacterial pathogens can be transmitted between them.

Neorickettsia risticii, Rickettsia sp. and Bartonella sp. in Tadarida brasiliensis bats from Buenos Aires, Argentina.

Bats are potential reservoirs of many vector-borne bacterial pathogens. The aim of the present study was to detect species of Anaplasma, Ehrlichia, Neorickettsia, Rickettsia, Borrelia and Bartonella in Brazilian free-tailed bats (Tadarida brasiliensis, Molossidae) from Buenos Aires city, Argentina. Between 2012 and 2013, 61 T. brasiliensis from urban areas of Buenos Aires city were studied. The samples were molecularly screened by PCR and sequencing. Five bats (8.2%) were positive to Neorickettsia risticii, one (1.6%) was positive to Rickettsia sp. and three bats (4.9%) to Bartonella sp. For molecular characterization, the positive samples were subjected to amplification and sequencing of a fragment of p51 gene for N. risticii, a fragment of citrate synthase gene (gltA) for Rickettsia genus and a fragment of gltA for Bartonella genus. Phylogenetic tree was constructed using the maximum-likelihood method. Phylogenetic analysis of N. risticii detect in our study revealed that it relates to findings in the USA West Coast; Rickettsia sp. detected is phylogenetically within R. bellii group, which also includes many other Rickettsia endosymbionts of insects; and Bartonella sp. found is related to various Bartonella spp. described in Vespertilionidae bats, which are phylogenetically related to Molossidae. Our results are in accordance to previous findings, which demonstrate that insectivorous bats could be infected with vector-borne bacteria representing a potential risk to public health. Future research is necessary to clarify the circulation of these pathogens in bats from Buenos Aires.

Vector-Borne Bacterial Plant Pathogens: Interactions with Hemipteran Insects and Plants.

Hemipteran insects are devastating pests of crops due to their wide host range, rapid reproduction, and ability to transmit numerous plant-infecting pathogens as vectors. While the field of plant–virus–vector interactions has flourished in recent years, plant–bacteria–vector interactions remain poorly understood. Leafhoppers and psyllids are by far the most important vectors of bacterial pathogens, yet there are still significant gaps in our understanding of their feeding behavior, salivary secretions, and plant responses as compared to important viral vectors, such as whiteflies and aphids. Even with an incomplete understanding of plant–bacteria–vector interactions, some common themes have emerged: (1) all known vector-borne bacteria share the ability to propagate in the plant and insect host; (2) particular hemipteran families appear to be incapable of transmitting vector-borne bacteria; (3) all known vector-borne bacteria have highly reduced genomes and coding capacity, resulting in host-dependence; and (4) vector-borne bacteria encode proteins that are essential for colonization of specific hosts, though only a few types of proteins have been investigated. Here, we review the current knowledge on important vector-borne bacterial pathogens, including Xylella fastidiosa, Spiroplasma spp., Liberibacter spp., and ‘Candidatus Phytoplasma spp.’. We then highlight recent approaches used in the study of vector-borne bacteria. Finally, we discuss the application of this knowledge for control and future directions that will need to be addressed in the field of vector–plant–bacteria interactions.

Police dogs from Albania as indicators of exposure risk to Toxoplasma gondii, Neospora caninum and vector-borne pathogens of zoonotic and veterinary concern

Knowledge on the prevalence of the zoonotic and animal pathogens in dogs from Albania is thus far limited. Samples were collected from 119 police dogs which were deployed throughout Albania and which were living in close relationship with humans. Direct and/or indirect methods were used to examine 119 whole blood and 117 serum samples for the protozoans Toxoplasma gondii (IFAT) and Neospora caninum (IFAT), various vector-borne pathogens of zoonotic and veterinary concern (SFG rickettsiae [ELISA, IFAT], Anaplasma spp. [PCR, IFAT], Ehrlichia canis [PCR, IFAT], Babesia spp. [PCR, IFAT], Leishmania infantum [PCR, IFAT], Hepatozoon canis [PCR], Dirofilaria immitis [ELISA]), and haemotropic mycoplasmas [PCR]. DNA of L. infantum and Anaplasma platys was detected in the blood of four and two dogs, respectively, but all samples were negative for DNA of E. canis, Babesia spp., H. canis and haemotropic mycoplasmas. D. immitis antigen was detected in 11.2% of the serum samples. The overall seroprevalences were: SFG rickettsiae (ELISA), 71.5%; Rickettsia conorii (IFAT), 61.5%; T. gondii, 65.0%; Anaplasma spp., 31.6%; E. canis, 17.9%; L. infantum, 12.0%; N. caninum, 12.0% and Babesia canis, 3.4%. Seven dogs were PCR-negative and seronegative for all tested pathogens. Significantly more dogs from South Albania (24.3%) had antigen of D. immitis than dogs from North Albania (5.4%, p=0.046). There was no difference in the geographical distribution of exposure to any other pathogen. Age was found to be a risk factor (p<0.05) for exposure to T. gondii, SFG rickettsiae, Anaplasma spp. and L. infantum. Co-exposure to up to five vector-borne pathogens was found in 51.5% of the 103 dogs that were seropositive for at least one vector-borne pathogen. Results of this study indicate a considerable risk of infection for dogs and/or humans with T. gondii and N. caninum and a range of zoonotic vector-borne bacterial and protozoan pathogens.

Prevalence of Vector-borne Bacterial Pathogens in Riparian Brush Rabbits (Sylvilagus bachmani riparius) and their Ticks

From June to October 2010, 48 endangered riparian brush rabbits (Sylvilagus bachmani riparius) were trapped at a captive propagation site in central California with the intention of release into re-established habitats. During prerelease examinations, ticks and blood samples were collected for surveillance for Rickettsia spp., Anaplasma phagocytophilum, Borrelia burgdorferi, and Bartonella spp. Ticks were identified, and DNA was extracted for PCR analysis. Serology was performed to detect exposure to Rickettsia spp., B. burgdorferi, and A. phagocytophilum. DNA was extracted from blood samples and analyzed for A. phagocytophilum using PCR assays. Rabbit blood samples were also cultured for Bartonella spp. Haemaphysalis leporispalustris ticks were detected on all rabbits except one. A total of 375 ticks were collected, with 48% of the rabbits (23 rabbits) having a burden ranging from 0 to 5 ticks, 15% (seven rabbits) from 6 to 10 ticks, 25% (12 rabbits) from 11 to 15 ticks, and 12% (six rabbits) with >15 ticks. There was no evidence of B. burgdorferi or R. rickettsii in tick or rabbit samples. There was also no evidence of Bartonella spp. in the rabbit samples. Four tick samples and 14 rabbits were weakly PCR positive for A. phagocytophilum, and six rabbits were antibody positive for A. phagocytophilum. These results suggest that there may be little risk of these tick-borne diseases in riparian brush rabbits or to the people in contact with them.

Anaplasma phagocytophilum Infects Mast Cells via α1,3-Fucosylated but Not Sialylated Glycans and Inhibits IgE-Mediated Cytokine Production and Histamine Release

Mast cells are sentinels for infection. Upon exposure to pathogens, they release their stores of proinflammatory cytokines, chemokines, and histamine. Mast cells are also important for the control of certain tick-borne infections. Anaplasma phagocytophilum is an obligate intracellular tick-transmitted bacterium that infects neutrophils to cause the emerging disease granulocytic anaplasmosis. A. phagocytophilum adhesion to and infection of neutrophils depend on sialylated and α1,3-fucosylated glycans. We investigated the hypotheses that A. phagocytophilum invades mast cells and inhibits mast cell activation. We demonstrate that A. phagocytophilum binds and/or infects murine bone marrow-derived mast cells (BMMCs), murine peritoneal mast cells, and human skin-derived mast cells. A. phagocytophilum infection of BMMCs depends on α1,3-fucosylated, but not sialylated, glycans. A. phagocytophilum binding to and invasion of BMMCs do not elicit proinflammatory cytokine secretion. Moreover, A. phagocytophilum-infected cells are inhibited in the release of tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), IL-13, and histamine following stimulation with IgE or antigen. Thus, A. phagocytophilum mitigates mast cell activation. These findings potentially represent a novel means by which A. phagocytophilum usurps host defense mechanisms and shed light on the interplay between mast cells and vector-borne bacterial pathogens.

Arthropod Vectors and Vector-Borne Bacterial Pathogens in Yosemite National Park

Ticks, fleas, and vector-borne pathogens were surveyed in diverse small mammals in Yosemite National Park, California, from 2005 to 2007. A total of 450 unique captures of small mammals was collected during a 3-yr period and yielded 16 species of fleas and 10 species of ticks, including known vectors of Anaplasma phagocytophilum and Borrelia burgdorferi and plague. Serology was performed for A. phagocytophilum, spotted fever group Rickettsia spp., B. burgdorferi, and Yersinia pestis. A. phagocytophilum exposure was identified in 12.1% of all wild small mammals tested, with seropositive animals in 10 species, notably Belding's ground squirrels (Spermophilus beldingi), jumping mice (Zapus princeps), and voles (Microtus sp.). Spotted fever group Rickettsia spp. exposure was detected in 13.9% of all small mammals tested, with seropositive animals in eight species. Additionally, 37.0% of rodents in five species tested were seropositive for B. burgdorferi. No individuals were seropositive for Y. pestis. No animals were polymerase chain reaction positive for any pathogen tested. These results provide baseline data for future research and prediction of emerging vector-borne disease in Yosemite National Park, as well as adding to the known ranges and host species for tick and fleas in California.

Tick-borne Relapsing Fever andBorrelia hermsii, Los Angeles County, California, USA

The primary cause of tick-borne relapsing fever in western North America is Borrelia hermsii, a rodent-associated spirochete transmitted by the fast-feeding soft tick Ornithodoros hermsi. We describe a patient who had an illness consistent with relapsing fever after exposure in the mountains near Los Angeles, California, USA. The patient's convalescent-phase serum was seropositive for B. hermsii but negative for several other vector-borne bacterial pathogens. Investigations at the exposure site showed the presence of O. hermsi ticks infected with B. hermsii and the presence of rodents that were seropositive for the spirochete. We determined that this tick-borne disease is endemic to the San Gabriel Mountains near the greater Los Angeles metropolitan area.

SURVEILLANCE OF EGYPTIAN FLEAS FOR AGENTS OF PUBLIC HEALTH SIGNIFICANCE: ANAPLASMA, BARTONELLA, COXIELLA, EHRLICHIA, RICKETTSIA, AND YERSINIA PESTIS

Serologic surveys in Egypt have documented human and animal exposure to vector-borne bacterial pathogens, but the presence and distribution of these agents in arthropods has not been determined. Between July 2002 and July 2003, fleas were collected from 221 mammals trapped in 17 cities throughout Egypt. A total of 987 fleas were collected, representing four species (Ctenocephalides felis, Echidnophaga gallinacea, Leptopsylla segnis, and Xenopsylla cheopis); 899 of these fleas were X. cheopis from rats (Rattus spp.). Fleas were tested for DNA from Anaplasma spp., Bartonella spp., Coxiella burnetii, Ehrlichia spp., Rickettsia spp., and Yersinia pestis. Rickettsia typhi, the agent of murine typhus, was detected in X. cheopis and L. segnis from rats from nine cities. A spotted-fever group Rickettsia sp. similar to "RF2125" was detected in E. gallinacea, and two unidentified spotted fever group Rickettsia were detected in two X. cheopis. Novel Bartonella genotypes were detected in X. cheopis and L. segnis from three cities. Coxiella burnetii was detected in two fleas. Anaplasma, Ehrlichia, and Y. pestis were not detected.

Important emerging bacterial zoonotic infections affecting the immunocompromised

The immunocompromised are at particular risk for infection with zoonotic diseases. Persons can be temporarily immunocompromised due to pregnancy or developmental stage (i.e. infants); longer-term or permanent states of immunosuppression can occur as a result of immunosuppressive treatment following cancer or organ transplant, or from infectious diseases, such as AIDS. The focus of this review article is on emerging bacterial zoonotic diseases that are of particular concern among the immunocompromised. Factors that affect disease emergence can include factors such as human demographics and behavior; technology and industry; economic development and land use; international travel and commerce; microbial adaptation and change; and breakdown of public health measures. The immunocompromised need to take precautions when engaging in seemingly normal activities such as food preparation; caring for companion animals; and recreational or occupational activities. The immunocompromised are not only more susceptible to infection, but often suffer more serious sequelae as a result of infection. This review article provides an overview of the major foodborne, respiratory, and vector-borne bacterial pathogens that affect the immunocompromised. The major categories of immunodeficiency are described. In addition, measures that can be taken to prevent infection, including the role of health education, are discussed.