Tick saliva contains about 1,500 to 3,000 proteins depending on the tick species. The American mink often carries light tick and flea infestations. Most people who get infected do not remember seeing a tick or the bite. It is not useful following the bite of an infected tick. Humans contract infection from the bite of nymphs of the tick. "B. burgdorferi" is injected into the skin by the bite of an infected "Ixodes" tick. Neurological problems following tick bites were recognized starting in the 1920s. Pregnant women bitten by a tick should see their doctor. We can tick that off the list. Rickettsiae are transmitted to through saliva injected while a tick is feeding. Using pesticides to reduce tick numbers may also be effective. The risk of infectious transmission increases with the duration of tick attachment. All three clocks simultaneously start to tick in S. Flying foxes are also threatened by disease such as tick paralysis. The oldest example is an argasid bird tick from Cretaceous New Jersey amber.