of infection. unfed tick nymphs are the size of a poppy seed, but a day or two after biting and attaching themselves to a person, they look like a small blood blister. the following areas should be checked especially carefully: armpits, between legs, back of knee, bellybutton, trunk, and in children ears, neck and hair. tick removal removal of a tick using tweezers attached ticks should be removed promptly. risk of infection increases with time of attachment, but in north america risk of lyme disease is small if the tick is removed within 36 hours. cdc recommends inserting a fine-tipped tweezer between the skin and the tick, grasping very firmly, and pulling the closed tweezer straight away from the skin without twisting, jerking, squeezing or crushing the tick. after tick removal, any tick parts remaining in the skin should be removed with a clean tweezer, if possible. the wound and hands should then be cleaned with alcohol or soap and water. the tick may be disposed by placing it in a container with alcohol, sealed bag, tape or flushed down the toilet. the bitten person should write down where and when the bite happened so that this can be informed to a doctor if the person gets a rash or flu-like symptoms in the following several weeks. cdc recommends not using fingers, nail polish, petroleum jelly or heat on the tick to try to remove it. in australia, where the australian paralysis tick is prevalent, the australasian society of clinical immunology and allergy recommends not using tweezers to remove ticks, because if the person is allergic, anaphylaxis could result. instead, a product should be sprayed on the tick to cause it to freeze and then drop off. a doctor would use liquid nitrogen, but products available from chemists for freezing warts can be used instead. another method originating from australia consists in using about 20 cm of dental floss or fishing line for slowly tying an overhand knot between the skin and the tick and then pulling it away from the skin. preventive antibiotics the risk of infectious transmission increases with the duration of tick attachment. it requires between 36 and 48 hours of attachment for the bacteria that causes lyme to travel from within the tick into its saliva. if a deer tick that is sufficiently likely to be carrying borrelia is found attached to a person and removed, and if the tick has been attached for 36 hours or is engorged, a single dose of doxycycline administered within the 72 hours after removal may reduce the risk of lyme disease. it is not generally recommended for all people bitten, as development of infection is rare: about 50 bitten people would have to be treated this way to prevent one case of erythema migrans (i.e. the typical rash found in about 70–80% of people infected). garden landscaping several landscaping practices may reduce the risk of tick bites in residential yards. these include keeping lawns mowed, removing leaf litter and weeds, and avoiding the use of ground cover. a 3-ft-wide rock or woodchip barrier is recommended to separate lawns from wood piles, woodlands, stone walls, and shrubs. without vegetation on the barrier, ticks will tend not to cross it; acaricides may also be sprayed on it to kill ticks. a sun-exposed tick-safe zone at least 9 ft from the barrier should concentrate human activity on the yard, including any patios, playgrounds and gardening. materials such as wood decking, concrete, bricks, gravel or woodchips used on the ground under patios and playgrounds would discourage ticks there. an 8-ft-high fence may be added to keep deer away from the tick-safe zone. occupational exposure outdoor workers are at risk of lyme disease if they work at sites with infected ticks. this includes construction, landscaping, forestry, brush clearing, land surveying, farming, railroad work, oil field work, utility line work, park or wildlife management. u.s. workers in the northeastern and north-central states are at highest risk of exposure to infected ticks. ticks may also transmit other tick-borne diseases to workers in these and other regions of the country. worksites with woods, bushes, high grass or leaf litter are likely to have more ticks. outdoor workers should be most careful to protect themselves in the late spring and summer when young ticks are most active. host animals ticks can feed upon the blood of a wide array of possible host species, including lizards, birds, mice, cats, dogs, deer, cattle and humans. the extent to which a tick can feed, reproduce, and spread will depend on the type and availability of its hosts. whether it will spread disease is also affected by its available hosts. some species, such as lizards, are referred to as "dilution hosts" because they don't tend to support lyme disease pathogens and so decrease the likelihood that the disease will be passed on by ticks feeding on them. white-tailed deer are both a food source and a "reproductive host", where ticks tend to mate. the white-footed mouse is a reservoir host in which the pathogen for lyme disease can survive. availability of hosts can have significant impacts on the transmission of lyme disease. a greater diversity of hosts, or of those that don't support the pathogen, tends to decrease the likelihood that the disease will be transmitted. in the united states, one approach to reducing the incidence of lyme and other deer tick-borne diseases has been to greatly reduce the deer population on which the adult ticks depend for feeding and reproduction. lyme disease cases fell following deer eradication on an island, monhegan, maine, and following deer control in mumford cove, connecticut. advocates have suggested reducing the deer population to levels of 8 to 10 deer per square mile, compared to levels of 60 or more deer per square mile in the areas of the country with the highest lyme disease rates. others have noted that while deer are reproductive hosts, they are not borrelia burgdorferi reservoirs. researchers have suggested that smaller, less obviously visible lyme reservoirs, like white-footed mice and eastern chipmunks, may more strongly impact lyme disease occurrence. ecosystem studies in new york state suggest that white-footed mice thrive when forests are broken into smaller isolated chunks of woodland with fewer rodent predators. with more rodents harboring the disease, the odds increase that a tick will feed on a disease-harboring rodent and that someone will pick up a disease-carrying tick in their garden or walking in the woods. 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. (1992) (incompetent host for b. burgdorferi and tbe virus) but it is important for feeding the ticks, as red deer and wild boars (sus scrofa), in which one rickettsia and three borrelia species were identified", with high risks of coinfection in roe deer. nevertheless, in the 2000s, in roe deer in europe "two species of rickettsia and two species of borrelia were identified". vaccination no human vaccines for lyme disease are currently available. the only human vaccine to advance to market was lymerix, which was available starting in 1998 before being pulled from the market in 2002. the vaccine candidate vla15 was scheduled to start a phase 3 trial in the third quarter of 2022, and other research is ongoing. multiple vaccines are available for the prevention of lyme disease in dogs. lymerix the vaccine lymerix was available from 1998 to 2002. the recombinant vaccine against lyme disease, based on the outer surface protein a (ospa) of b. burgdorferi with aluminum hydroxide as adjuvant, was developed by smithkline beecham. in clinical trials involving more than 10,000 people, the vaccine was found to confer protective immunity to lyme disease in 76% of adults after three doses with only mild or moderate and transient adverse effects. on 21 december 1998, the food and drug administration (fda) approved lymerix on the basis of these trials for persons of ages 15 through 70. following approval of the vaccine, its entry into clinical practice was slow for a variety of reasons, including its cost, which was often not reimbursed by insurance companies. subsequently, hundreds of vaccine recipients reported they had developed autoimmune and other side effects. supported by some advocacy groups, a number of class-action lawsuits were filed against glaxosmithkline, alleging the vaccine had caused these health problems. these claims were investigated by the fda and the centers for disease control, which found no connection between the vaccine and the autoimmune complaints. despite the lack of evidence that the complaints were caused by the vaccine, sales plummeted and lymerix was withdrawn from the u.s. market by glaxosmithkline in february 2002, in the setting of negative media coverage and fears of vaccine side effects. the fate of lymerix was described in the medical literature as a "cautionary tale"; an editorial in nature cited the withdrawal of lymerix as an instance in which "unfounded public fears place pressures on vaccine developers that go beyond reasonable safety considerations." the original developer of the ospa vaccine at the max planck institute told nature: "this just shows how irrational the world can be ... there was no scientific justification for the first ospa vaccine lymerix being pulled." vla15 the hexavalent (ospa) protein subunit-based vaccine candidate vla15 was developed by valneva. it was granted fast track designation by the u.s. food and drug administration in july 2017. in april 2020 pfizer paid $130 million for the rights to the vaccine, and the companies are developing it together, performing multiple phase 2 trials. a phase 3 trial of vla15 was scheduled for late 2022, recruiting volunteers at test sites located across the northeastern united states and in europe. participants were scheduled to receive an initial three-dose series of vaccines over the course of five to nine months, followed by a booster dose after twelve months, with both the initial series and the booster dose scheduled to be complete before the year's peak lyme disease season. other research an mrna vaccine designed to cause a strong fast immune response to tick saliva allowed the immune system to detect and remove the ticks from test animals before they were able to transmit the infectious bacteria. the vaccine contains mrnas for the body to build 19 proteins in tick saliva which, by enabling quick development of erythema (itchy redness) at the bite site, protects guinea pigs against lyme disease. it also protected the test animals if the tick is not removed if only one tick, but not three, remain attached. canine vaccines canine vaccines have been formulated and approved for the prevention of lyme disease in dogs. currently, three lyme disease vaccines are available. lymevax, formulated by fort dodge laboratories, contains intact dead spirochetes which expose the host to the organism. galaxy lyme, intervet-schering-plough's vaccine, targets proteins ospc and ospa. the ospc antibodies kill any of the bacteria that have not been killed by the ospa antibodies. canine recombinant lyme, formulated by merial, generates antibodies against the ospa protein so a tick feeding on a vaccinated dog draws in blood full of anti-ospa antibodies, which kill