Poly-ticks: Blue State versus Red State for Lyme disease

Abstract

Lyme disease, caused by the spirochaete Borrelia burgdorferi, is the most common vector-borne disease in the USA. In 2002, 23 763 cases were reported, with patients diagnosed in every state except Montana, Hawaii, and Oklahoma. Most cases were concentrated in the northeastern, middle Atlantic, north central, and Pacific states, a pattern remarkably similar to the distribution of Blue States (Kerry) in the Presidential election in 2004 (figure). Interestingly, the 19 states won by Kerry accounted for over 95% of the total number of cases of Lyme disease. The inauguration on Jan 20 of the victor, from Texas, the Lone Star State, turned our minds to the cause of Lyme disease. Besides a different voting behaviour, most of the Red States (Bush) also have a different kind of “Lyme disease”. B burgdorferi does not appear to be the cause of indigenous cases of Lyme disease in any southern state, besides, possibly, Virginia. Although patients with suspected Lyme disease in the south often have a skin lesion regarded as indistinguishable from erythema migrans, such rashes are frequently preceded by the bite of an Amblyomma americanum tick (the Lone Star tick), which is not a competent vector for B burgdorferi. Therefore, although fulfilling the surveillance case-definition and tabulated as Lyme disease, this rash is more appropriately named southerntick-associated rash illness (STARI). An alternative name is Master’s disease, in recognition of a key investigator, Edwin Masters. The cause of STARI, although sometimes attributed to a Borrelia species other than B burgdorferi, remains unclear, as does its management. It is important to recognise that the range of A americanum extends well beyond the Red States and as far north along the eastern seaboard as Maine. “Lyme disease” cases have followed the bite of this tick in both New Jersey and Maryland, suggesting that cases of erythema migrans in some Blue States are not exclusively due to B burgdorferi infection. A strong recommendation can be made for further study of STARI and of Presidential elections.