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Transmission of the Human Relapsing Fever Spirochete Borrelia persica by the Argasid Tick Ornithodoros tholozani Involves Blood Meals from Wildlife Animal Reservoirs and Mainly Transstadial Transfer.

ABSTRACT: Borrelia persica, transmitted by the argasid tick Ornithodoros tholozani, causes human tick-borne relapsing fever in the Middle East and Central Asia. Infection is acquired often when visiting tick-infested caves and reported to be transmitted mainly transovarially between ticks, occasionally infecting humans. To study the epidemiology of this infection, ticks were trapped in 24 caves in 12 geographic zones covering all of Israel and identified morphologically. DNA was extracted from larvae, nymphs, and adult stages from each location and PCR followed by DNA sequencing was performed to identify Borrelia infection, tick species, and tick blood meal sources. We collected 51,472 argasid ticks from 16 of 24 caves surveyed. We analyzed 2,774 O. tholozani ticks, and 72 (2.6%) from nine caves were PCR positive for B. persica Infection rates in male, female, and nymphal ticks (4.4%, 3%, and 3.2%, respectively) were higher than in larva (P < 0.001), with only 3 (0.04%) positive larvae. Presence of blood meal was associated with B. persica infection in ticks (P = 0.003), and blood meals of golden jackals, red foxes, and Cairo spiny mouse were associated with infection (P ≤ 0.043). PCR survey of 402 wild mammals revealed B. persica infection with the highest rates in social voles (22%), red foxes (16%), golden jackals (8%), and Cairo spiny mice (3%). In conclusion, although transovarial tick transmission of B. persica occurs at low levels, ticks apparently acquire infection mainly from wildlife canid and rodents and may eventually transmit relapsing fever borreliosis to humans who enter their habitat.IMPORTANCE Borrelia persica is a spirochete that causes tick-borne relapsing fever in humans in an area that spans from India to the Mediterranean. Until now, it was thought that the soft tick vector of this infection, Ornithodoros tholozani, is also its main reservoir and it transmits B. persica mostly transovarially between tick generations. This study showed that tick infection with B. persica is associated with feeding blood from wild jackals, foxes, and rodents and that transovarial transmission is minimal. Since O. tholozani ticks are found in isolated caves and ruins, it is assumed that wild canids who migrate over long distances have a major role in the transmission of B. persica between remote tick populations, and it is then maintained locally also by rodents and eventually transferred to humans during tick bites. Prevention of human infection could be achieved by restricting entrance of canines and humans to habitats with O. tholozani populations.

SUBMITTER: Kleinerman G

PROVIDER: S-EPMC8208150 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Vector competence refers to the ability of an arthropod to acquire, maintain, and successfully transmit a microbial pathogen. Tick-borne relapsing fever (TBRF) spirochetes are globally distributed pathogens, and most species are transmitted by argasid ticks of the genus Ornithodoros. A defining characteristic in vector competence is an apparent specificity of a species of TBRF spirochete to a given tick species. In arid regions of the southern United States, Borrelia turicatae is the primary cause of TBRF. Interestingly, there are two populations of the tick vector distributed throughout this region. Ornithodoros turicata is a western population that ranges from California to Texas. There is a gap through Louisiana, Mississippi, and Alabama where the tick has not been identified. An isolated eastern population exists in Florida and was designated a subspecies, O. turicata americanus. A knowledge gap that exists is the poor understanding of vector competence between western and eastern populations of ticks for B. turicatae. In this study, we generated uninfected colonies of O. turicata that originated in Texas and Kansas and of O. turicata americanus. B. turicatae acquisition, maintenance through the molt, and subsequent transmission were evaluated. Our findings revealed significant differences in murine infection after feeding infected O. turicata and O. turicata americanus ticks on the animals. Interestingly, the salivary glands of both tick populations were colonized with B. turicatae to similar densities. Our results suggest that the salivary glands of the tick colonies assessed in this study impact vector competence of the evaluated B. turicatae isolates.IMPORTANCE Several knowledge gaps exist in the vector competence of various geographical populations of O. turicata that transmit B. turicatae A western population of this tick is distributed from California to Texas, and an eastern population exists in Florida. Utilizing western and eastern populations of the vector, we studied acquisition and transmission of two B. turicatae isolates. Regardless of the isolate used, infection frequencies were poor in mice after the eastern population feeding on them. Since salivary gland colonization is essential for B. turicatae transmission, these tissues were further evaluated. Interestingly, the salivary glands from the two populations were similarly colonized with B. turicatae. These findings suggest the role of tick saliva in the establishment of infection and that the salivary glands may be a bottleneck for successful transmission.

Project description:The argasid tick Ornithodoros erraticus is the vector of African swine fever virus and of several Borrelia species that cause human relapsing fever in the Iberian Peninsula. The tick midgut is part of the ectoparasite-host interface and expresses proteins that are vital for the survival of the tick. Midgut proteins are therefore potential targets for drug and/or vaccine design aimed at the development of new strategies for tick control. Thus, the aim of this work was the characterization of the proteome of the O. erraticus midgut before and after a blood meal trying to elucidate the induced changes upon blood feeding.Midgut tissues from unfed and engorged O. erraticus females were dissected and proteins were fractionated by centrifugation and SDS-PAGE, and the corresponding gel pieces analysed by LC-MS/MS. The identified proteins were classified according to their Protein Class and Molecular Function and the differences between fed and unfed specimens were analysed.Overall 555 tick proteins were identified: 414 in the midgut of the unfed specimens and 376 in the fed specimens, of which 235 were present in both groups. The proteins with catalytic, binding and structural functions were the most numerous and abundant, consistent with their role in the intracellular processing of the blood meal. The analysis of some groups of proteins putatively involved directly in blood meal digestion, including protein digestion (peptidase activity), iron metabolism, enzymes involved in oxidative stress and detoxification and membrane traffic and transport proteins, detected some differences between the fed and unfed ticksThis work reports for the first time the collection and analysis of the midgut proteome of an argasid tick species and provides molecular information about the argasid machinery involved in blood digestion. This information represents a starting point for the identification and selection of new targets for the development of alternative control strategies.

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Transmission of the Human Relapsing Fever Spirochete Borrelia persica by the Argasid Tick Ornithodoros tholozani Involves Blood Meals from Wildlife Animal Reservoirs and Mainly Transstadial Transfer.

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