Most people who get infected do not remember a tick or a bite, and the EM rash need not look like a bulls eye (most EM rashes in the U.S. do not) or be accompanied by any other symptoms. In the U.S., Lyme is most common in the New England and Mid-Atlantic states and parts of Wisconsin and Minnesota, but it is expanding into other areas. Several bordering areas of Canada also have high Lyme risk.In the absence of an EM rash or history of tick exposure, Lyme diagnosis depends on laboratory confirmation. The bacteria that cause Lyme disease are difficult to observe directly in body tissues and also difficult and too time-consuming to grow in the laboratory. The most widely used tests look instead for presence of antibodies against those bacteria in the blood. A positive antibody test result does not by itself prove active infection but can confirm an infection that is suspected because of symptoms, objective findings, and history of tick exposure in a person. Because as many as 5–20% of the normal population have antibodies against Lyme, people without history and symptoms suggestive of Lyme disease should not be tested for Lyme antibodies: a positive result would likely be false, possibly causing unnecessary treatment.In some cases, when history, signs, and symptoms are strongly suggestive of early disseminated Lyme disease, empiric treatment may be started and reevaluated as laboratory test results become available.
Data indicates that the smaller the wooded area, the more ticks it will contain and the likely they are to carry Lyme disease, supporting the idea that  deforestation and habitat fragmentation affect ticks, hosts and disease transmission.Tick-borne diseases are estimated to affect ~80 % of cattle worldwide. They also affect cats, dogs, and other pets. Routine veterinary control of ticks of domestic animals through the use of acaricides has been suggested as a way to reduce exposure of humans to ticks. However, chemical control with acaricides is now criticized on a number of grounds. Ticks appear to develop resistance to acaricides; acaricides are costly; and there are concerns over their toxicity and the potential for chemical residues to affect food and the environment.In Europe, known reservoirs of Borrelia burgdorferi were 9 small mammals, 7 medium-sized mammals and 16 species of birds (including passerines, sea-birds and pheasants). These animals seem to transmit spirochetes to ticks and thus participate in the natural circulation of B. burgdorferi in Europe. The house mouse is also suspected as well as other species of small rodents, particularly in Eastern Europe and Russia. "The reservoir species that contain the most pathogens are the European roe deer Capreolus capreolus; "it does not appear to serve as a major reservoir of B. burgdorferi" thought Jaenson & al.