As the temperature warms up and Californians start spending more time outdoors their risk ofatick bite increases. “Nymphs,”or immature form of the western black-legged ticks, which transmit Lyme Disease (LD), are most active during the spring and early summer months. This advisory is to review the salient clinical characteristics of LD, to provide guidelines on diagnosis and treatment, to provide instruction for reporting cases, to briefly cover other tick-borne illnesses and to provide guidance on when to submit ticks for testing. According to the 2006 Vector Borne Diseases in California 2006 Annual Report from the California Department of Public Health (CDPH0, the incidence of LD in Napawas 1.2 cases/100,000 person years from 1997-2006. LYME DISEASE Background Lyme Disease (LD) was first described in 1977 as a cluster of oligoarticular arthritis in children and adults near Lyme, Connecticut. The spirochetal agent of LD is Borreliaburgdorferi, which istrasmitted by the bite of an infected tick vector. The CDC made LD anationally notifiable condition in 1982. Title 17 oftheCalifornia Code of Regulations requires that physicians report all newly diagnosed cases of LD to their local health departments. The first recognized human casein California occurred in 1978 in a hiker from Sonoma County. As of 2000, the CDPH has reported 1,700 of LD from 52 of 58 counties. Transmission In California, the bacterium (B. burgdoferi) that causes LD is transmitted to humans by the western black-legged tick, Ixodespacificus, which has three life stages: larva, nymph, and adult. Only nymphs and adult ticks can transmit the infection to humans. Nymphs are most active from March through July, while adults are most active November through March. However, if conditions are favorable, ticks can be active year -round. The CDPHVector Borne Diseases section regularly conducts surveillance for Ixodespacificus in Bothe- Napa ValleyState Park where pooled samples of ticks first tested positive for Borreliaburgdoferi in 2005. Factors Affecting Transmission of Lyme Disease Tick type-B. bergdoferiisonly transmitted by ticks of the genus Ixodes, and most infections are transmitted by nymphal ticks which are approximately the size of poppy seeds (as opposed to the dog tick which is about the size of a pencil eraser)….

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