Other Vectors – A New Syndrome?

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Section 5: Other Vectors – A New Syndrome?

More information has been recently forthcoming, which provides putative evidence to support the role of other ticks in the transmission of Bb and other microorganisms (42,43). For example, in North Carolina, the Lone Star Tick, or Amblyomma americanum, is more common than Ixodes scapularis (above referenced deer tick), and has been implicated in transmission of Bb. In the western US, another tick, Ixodes pacificus, is recognized as the vector for Bb, and behaves much like its counterpart in the eastern US, Ixodes scapularis. In contrast to the Ixodes scapularis tick, we know much less about the nature of transmission of Bb, when other vectors, like the Lone Star tick, is involved. It would seem unlikely that the Lone Star tick requires 48 to 72 hours of attachment in order to transmit Bb, since the human host would in most instances be expected to recognize the attached tick before that time. No one knows how transmission by a different vector such as Amblyomma americanum would influence the epidemiology and natural course of LD.

Another Lone Star tick borne illness, Southern Tick Associated Rash Illness, or STARI, has been described in the southeast and southern Midwest US (44,45,46). This syndrome bears a great clinical resemblance to LD, including the presence of a bull’s eye rash. The organism responsible for this illness has not been positively identified, although Bb sensu lato is clearly not the agent, as multiple efforts to identify this pathogen from biopsies of the rash have been found negative (47). The presence of another spirochete, named Borrelia lonestari, which has been recovered from the tick midgut but not from clinical specimens in patients with STARI, is of considerable interest. Borrelia lonestari differs in DNA homology from Bb by about 5-7% (48). One important difference for B. lonestari is the absence of the OspA gene, an important surface marker antigen for Bb (49). Until more is known, we cannot assume that this is a self-limited disease, as it is purported to be. For that matter, STARI may simply represent one of the many variant strains of Bb. A family practice physician residing in Missouri, Dr. Ed Masters, is credited with recognizing and categorizing this tick borne illness. As a consequence, the infection is commonly referred to as “Masters Disease” as well as the older eponym STARI.

With Rocky Mountain spotted fever and now West Nile virus also firmly entrenched in the south, there is a much broader differential diagnosis list for the clinician to consider when one encounters flu like illness in warm weather months. The treating MD needs to be particularly mindful should they encounter a rash and/or any alteration of mental status, or encephalopathy, since failure to understand the potential severity of this process may lead to both serious short and long-term morbidity.

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