Tick‐Borne Diseases in the South‐East Need Human Studies: Lyme Disease, STARI and Beyond

To the editor: Stromdahl and Hickling have presented a valuable review of human tick-borne diseases (TBD) in the south-east in their recent article, ‘Aetiology of Tick-borne Human Diseases with Emphasis on the South-Eastern United States’ (Stromdahl and Hickling, 2012). Interestingly, they also supply new data from the Department of Defense gathered from military bases in the south. Southerners will benefit from their warning of increased risk of contracting a growing number of TBDs including Lyme disease and that medical providers’ tick-related knowledge is usually weak. As pointed out, the lone star tick, Amblyomma americanum, is now the most abundant tick in the south-east and is certainly the most aggressive. This tick and Ixodes scapularis are now sympatric over much of the Eastern United States. Amblyomma americanum was noted to have extended as far north as New Jersey 30 years ago (Schulze et al., 1984) and has now surpassed I. scapularis populations there (Schulze et al., 2005). It reached Maine at least 15 years ago (Keirans and Lacombe, 1998). The lone star tick is responsible for much human misery, controversy and, because of so many unknowns, improperly treated human conditions. Amblyomma americanum tick larvae have not been thought to transmit human pathogens, as stated in the review. It is hoped that researchers will look at the question of whether the spirochaete Borrelia miyamotoi, not mentioned by the Stromdahl and Hickling, may be vectored by the lone star tick. In other ticks, transovarial and transstadial transmission has been documented for this spirochaete (Scoles et al., 2001; Barbour et al., 2009). In Tennessee, a study found that 70% of studied turkeys were infested with juvenile A. americanum, and 58% were positive for the B. miyamotoi in either tissue or blood (Scott et al., 2010). In Russia, Borrelia miyamotoi has been shown to cause human disease manifesting as influenza-like illness with high fever, a relapsing febrile illness pattern in some and occasional (EM) rashes Erythema migrans (Platonov et al., 2011). If B. miyamotoi can even occasionally be vectored by lone star ticks, it could account for some of the Lyme-like illness seen in the south because many southerners can get dozens to hundreds of bites in a season, especially if a nest of newly hatched larvae is encountered. The enigma of Lyme-like disease in the south-east persists, especially in the form of southern tick-associated rash illness (STARI) or Masters disease. It may be the time to reinvestigate whether the lone star can occasionally transmit Borrelia burgdorferi because it is known to occasionally carry this organism. The oft-mentioned borreliacidal action of A. americanum saliva (Ledin et al., 2005) is not 100%– after 48 h, just under 13% of saliva-exposed B. burgdorferi were still alive, not 0%. Given the frequency of lone star tick bites, some B. burgdorferi could possibly pass through to a human. One of several studies on whether lone star ticks can transmit B. burgdorferi based part of their finding of lack of transmission on only three ticks, stating the lone stars did not feed well on rodents. In the same study, Dermacentor virabilis had some susceptibility but did not maintain the infection transstadially (Piesman and Happ, 1997) suggesting this tick be restudied, as well. Unfortunately, the dogma that there is little to no Lyme disease in the south continues to be repeated by numerous publications citing flawed case report numbers and ‘confirmed’ by studies seeking to prove the dogma. Because there is so much Lyme-like illness in the south as well as documented Lyme disease, we need studies that question how Lyme disease is being transmitted in the south-east. It is known that locally acquired cases do occur, that there is more genetic variation in southern strains of Borrelia burgdorferi sensu lato (Lin et al., 2001) than northern, that the spirochaete is well established in many areas (Lin et al., 2001; Clark, 2004; Harrison et al., 2010; Smith et al., 2010) and that the ‘northern’ tick-borne organisms Anaplasma phagocytophilum and Babesia microti are established in some areas of the south (Clark, 2012a; Clark et al., 2012b). Some northern areas endemic for Lyme disease now have endemic A. americanum populations. STARI cases in these areas are likely to be subsumed as Lyme disease (except in the rare case the lone star tick is brought in by the patient), leading to artificially high reports of Lyme disease (Feder et al., 2011). Erythema migrans (EM) rashes tend to be accepted as Lyme disease cases for public health reporting in the north regardless of presumed county of acquisition or travel history. Reporting differs in the south. For example, North Carolina now has three counties endemic by the Centres for Disease Control (CDC) criteria for Lyme disease; thus, physician-diagnosed EM rashes in these counties meet LD reporting criteria. EM patients who are residents