Polymicrobial Nature of Tick-Borne Diseases

Abstract

Tick-borne diseases have doubled in the last 12 years, and their geographic distribution has spread as well. The clinical spectrum of tick-borne diseases can range from asymptomatic to fatal infections, with a disproportionate incidence in children and the elderly. In the last few years, new agents have been discovered, and genetic changes have helped in the spread of pathogens and ticks. Polymicrobial infections, mostly in Ixodes scapularis, can complicate diagnostics and augment disease severity. Amblyomma americanum ticks have expanded their range, resulting in a dynamic and complex situation, possibly fueled by climate change. To document these changes, using molecular biology strategies for pathogen detection, an assessment of 12 microbes (9 pathogens and 3 symbionts) in three species of ticks was done in Suffolk County, New York. At least one agent was detected in 63% of I. scapularis ticks. Borrelia burgdorferi was the most prevalent pathogen (57% in adults; 27% in nymphs), followed by Babesia microti (14% in adults; 15% in nymphs), Anaplasma phagocytophilum (14% in adults; 2% in nymphs), Borrelia miyamotoi (3% in adults), and Powassan virus (2% in adults). Polymicrobial infections were detected in 22% of I. scapularis ticks, with coinfections of B. burgdorferi and B. microti (9%) and of B. burgdorferi and A. phagocytophilum (7%). Three Ehrlichia species were detected in 4% of A. americanum ticks. The rickettsiae constituted the largest prokaryotic biomass of all the ticks tested and included Rickettsia amblyommatis, Rickettsia buchneri, and Rickettsia montanensis. The high rates of polymicrobial infection in ticks present an opportunity to study the biological interrelationships of pathogens and their vectors. IMPORTANCE Tick-borne diseases have increased in prevalence in the United States and abroad. The reasons for these increases are multifactorial, but climate change is likely to be a major factor. One of the main features of the increase is the geographic expansion of tick vectors, notably Amblyomma americanum, which has brought new pathogens to new areas. The clinical spectrum of tick-borne diseases can range from asymptomatic to fatal infections, with a disproportionate incidence in children and the elderly. In addition, new pathogens that are cotransmitted by Ixodes scapularis have been discovered and have led to difficult diagnoses and to disease severity. Of these, Borrelia burgdorferi, the agent of Lyme disease, continues to be the most frequently transmitted pathogen. However, Babesia microti, Borrelia miyamotoi (another spirochete), Anaplasma phagocytophilum, and Powassan virus are frequent cotransmitted agents. Polymicrobial infection has important consequences for the diagnosis and management of tick-borne diseases.

Sharing the Ride: Ixodes scapularis Symbionts and Their Interactions

“…Cross et al also detected a negative co-occurrence Schwartz et al, 1997;Steiner et al, 2008;Tokarz et al, 2010Tokarz et al, , 2017Tokarz et al, , 2019Aliota et al, 2014;Johnson et al, 2018;Sanchez-Vicente et al, 2019B. burgdorferi -Babesia microti 1-22 Adelson et al, 2004Steiner et al, 2008;Tokarz et al, 2010Tokarz et al, , 2017Tokarz et al, , 2019Aliota et al, 2014;Johnson et al, 2018;Sanchez-Vicente et al, 2019B. burgdorferi -Bartonella spp.…”

“…8 Adelson et al, 2004B. burgdorferi -B. miyamotoi 1-3.5 Tokarz et al, 2017Sanchez-Vicente et al, 2019B. burgdorferi -DTV 0.4-2.5 Aliota et al, 2014Tokarz et al, 2017A.…”

“…Ixodes scapularis, commonly known as the black-legged or deer tick, is a major vector of human disease agents in the United States. In New York state, 22% of surveyed I. scapularis carried more than one human pathogen (Sanchez-Vicente et al, 2019). In some regions of North America, these polymicrobial infections occur at a higher prevalence than previously thought and may complicate both proper diagnoses and treatments.…”

Characterization of a Monanema nematode in Ixodes scapularis

“…We determined that ISN along with the nematode found in A. americanum represent the rst species of the genus Monanema uncovered outside of Africa. Recent insights into the I. scapularis microbiome have demonstrated that the prevalence of ISN is comparable to the prevalence of some I. scapularis-vectored pathogens [5,10]. In addition, its presence in ticks from the Mid-West and eastern USA suggest that ISN may have a geographical distribution throughout the range of I. scapularis.…”

Emerging tick-borne pathogens of public health importance: a mini-review

“…Larval stages of most tick species pose little to no risk of pathogen transmission to humans. Some tick species, such as Ixodes scapularis, may harbour numerous pathogens, whereas other commonly encountered species may typically be associated with one major pathogen ( Table 1) [33]. Successful prophylaxis of Lyme disease with preventative antibiotic treatment requires not only accurate tick species identification, but also the determination of the duration of tick feeding [32,34].…”