This photograph depicts a dorsal view of a male cayenne tick, Amblyomma cajennense. This tick specie is a known North, Central and South American vector of Rickettsia rickettsii, which is the etiologic agent of Rocky Mountain spotted fever (RMSF).
Note the large scutum, or “shield”, which unlike its female counterpart, covers the entire surface of this specimen’s dorsal abdomen. Like the female of the specie, the male also possesses four pairs of legs, placing it in the class of Arachnida, as are spiders and scorpions. Two of this specimen’s legs are tucked up underneath its abdomen.
Rocky Mountain spotted fever, like all rickettsial infections, is classified as a zoonosis. Zoonoses are diseases of animals that can be transmitted to humans. Many zoonotic diseases require a biological vector (e.g., a mosquito, tick, flea, or mite) in order to be transmitted from the animal host to the human host. In the case of RMSF, ticks are the natural hosts, serving as both reservoirs and vectors of R. rickettsii. Ticks transmit the organism to vertebrates primarily by their bite. Less commonly, infections may occur following exposure to crushed tick tissues, fluids, or tick feces.