Ixodida

Cheboygan Co., Michigan

Otsego Co., Michigan

Cheboygan Co., Michigan

All Biocode files are based on field identifications to the best of the researcher’s ability at the time.

Hobro, Jylland, Danmark

Multihost life cycle for argasid (soft) ticks.Unlike the Ixodidae (hard ticks), members of the family Argasidae (soft ticks) have two or more nymphal stages, each of which requires a blood meal. This pattern is referred to as the multihost life cycle. Two species of public health concern in the United States, Ornithodoros hermsi and O. turicata, are vectors of tick-borne relapsing fever (TBRF) spirochetes. In Africa and Asia, O. moubata is a vector of TBRF spirochetes. Members of the genus Carios are vectors of TBRF spirochetes in Central and South America.In argasid ticks, mating usually occurs (and egg-laying always occurs) off the host in a sheltered area, usually an animal nest. Eggs hatch into six-legged larvae (1) in the parents’ sheltered area. Larvae search for a host in the vicinity of the sheltered area. Once a suitable host is found, they feed for anywhere from one hour to several days, depending on the species (2). After feeding, the larvae leave the host and molt into the first nymphal instars in the sheltered area (3a-3b). The nymphs search for, and feed on, the second host (4) rapidly (usually about an hour). The second host is usually the same species, and often the same individual, as the first host. The first nymphal instars leave the host and molt into the next nymphal instars in the sheltered area >(5a-5b). This cycle can continue to accommodate up to seven nymphal instars (6), depending on the species. After the last nymphal instar has fed, it leaves the host and molts into an adult (7a-7b) in the sheltered area. Adults may continue to feed on the host (8), feeding rapidly and detaching after each blood meal. Females of some species lay egg batches after each meal. Humans are usually only incidental hosts for argasid ticks and may be fed upon by any of the stages.From Centers for Disease Control Parasites and Health website.

Spinose Ear Ticks (Otobius megnini)From Bugwood-University of Georgia

Mackinac Co., Michigan

All Biocode files are based on field identifications to the best of the researcher’s ability at the time.

Life cycle of one-host ixodid (hard) ticks.The adult of a one-host ixodid (hard) tick is considered the diagnostic stage, as identification to the species level is best achieved with adults. Few ixodids of public health importance have this type of life cycle, but one example is Rhipicephalus annulatus, which can serve as a vector for babesiosis. Rhipicephalus microplus, a major tick parasite of cattle in much of the world, also has a 1-host life cycle (Merck Veterinary Manual online).One-host ixodid ticks remain on the same host for the larval, nymphal, and adult stages, only leaving the host prior to laying eggs. Vertical transmission of Babesia via transovarial transmission has been demonstrated for some species of ticks. Gravid females lay eggs in the environment (1). The eggs hatch into six-legged larvae (2). Larvae seek out and attach to the host and after two molts, develop into adults (3a-3c). Although humans may serve as incidental hosts for species normally found on other animals, they usually do not host all three stages. Females drop from the host to lay eggs (4) and the cycle repeats.From Centers for Disease Control Parasites and Health website.

All Biocode files are based on field identifications to the best of the researcher’s ability at the time.

Kærby Mølle

Life cycle of the two-host ixodid (hard) ticks.The adult of a two-host ixodid (hard) tick is considered the diagnostic stage, as identification to the species level is best achieved with adults. An example of an ixodid tick of public health concern with this life cycle is Hyalomma marginatum, a vector of Crimean-Congo viral hemorrhagic fever.Two-host ixodid ticks have a life cycle that usually extends over two years. After feeding, gravid females drop off the second host to lay eggs (1), usually in the fall. Eggs hatch into six-legged larvae (2) and overwinter in this stage. The following spring, the larvae seek out and attach to the first host (3), usually a rodent (e.g., a mouse) or lagomorph (e.g., a rabbit). The larvae molt into nymphs on the first host (3a - 3b). Engorged nymphs drop off the first host, usually in the late summer or fall (4) and overwinter in the nymphal stage. Nymphs molt into adults the following spring (5) and seek out the second host (6), which is usually a larger herbivore (bovids, cervids, etc). Adults feed on the second host during the summer and mate. In the fall, females drop off the second host to continue the cycle. Females may reattach and feed multiple times. Humans may serve as first or second hosts for ticks with this life cycle. Also, the second host does not necessarily have to be a separate species, or even a separate individual, from the first host.From Centers for Disease Control Parasites and Health website.

Kilde ved Kærby Mølle

Life cycle of three-host ixodid (hard) ticks.The adult of a three-host ixodid (hard) tick is considered the diagnostic stage, as identification to the species level is best achieved with adults. Most ticks of public health importance are three-host ticks, including members of the genera Ixodes (Lyme borreliosis, babesiosis, human granulocytic ehrlichiosis), Amblyomma (tularemia, ehrlichiosis and Rocky Mountain spotted fever), Dermacentor (Rocky Mountain spotted fever, Colorado tick fever, tularemia, tick paralysis), and Rhipicephalus (Rocky Mountain spotted fever, boutonneuse fever).Three-host ixodid ticks have a life cycle that usually spans three years, although some species can complete the cycle in just two years. After feeding, adult females drop off the third host to lay eggs (1), usually in the fall. Eggs hatch into six-legged larvae (2) and overwinter in the larval stage. In the spring, the larvae seek out and attach to the first host, usually a small rodent (3). Later in the summer, engorged larvae leave the first host (4) and molt into nymphs (5), usually in the fall. The ticks overwinter in this stage. During the following spring, the nymphs seek out and attach to the second host (6), usually another rodent (e.g., a mouse) or lagomorph (e.g., a rabbit). The nymphs feed on the second host and drop off later in the summer (7). Nymphs molt into adults (7a-7b) off the host in the late summer or fall, and overwinter in this stage. The next spring, adults seek out and attach to a third host, which is usually a larger herbivore (including cervids and bovids), carnivore, or human (8). The adults feed and mate on the third host during the summer. Females drop off the host in the fall to continue the cycle. Females may reattach and feed multiple times. The three hosts do not necessarily have to be different species, or even different individuals. Humans may serve as first, second or third hosts.From Centers for Disease Control Parasites and Health website.

Kærby Mølle

Kærby Mølle

Midtsjælland

Midtsjælland, Denmark

Midtsjælland, Denmark

Midtsjælland, Denmark

Ixodes ricinus female in dorsal view. Photo credit: Harry Taylor, NHM.