Ticks

Ticks have a life cycle incorporating incomplete metamorphosis. Adult ticks feed and mate on mammals. Engorged females drop to the ground and lay eggs. The eggs hatch, producing six-legged larvae, or seed ticks. The seed tick moults twice, passing through an eight-legged nymphal stage before reaching maturity. A blood meal must be taken before each moult can occur. Ticks are classified as one-, two-, or three-host ticks, based on how many times they drop off, moult, and seek a new animal. A one-host tick remains on the animal from the seed-tick stage to maturity. A two-host tick drops off the initial host to moult from nymph to adult. The adult seeks a second animal for the final blood meal before copulation. The tree host tick drops to the ground for each moult, after which a new host is sought.

A knowledge of the life cycles of ticks is of great practical importance in planning a control program. In some areas control measures must be practiced at regular intervals for swine to be reared profitably.

Mites

In contrast to ticks, mites complete their entire life cycle, which incorporates incomplete metamorphosis, on the host. This is generally accomplished in 3 to 5 weeks. Mites cannot live for more than several days away from animals and are transmitted by direct body contact between pigs.

Lice

All stages of the louse life cycle, which takes about 3 to 4 weeks, occur on the host. Lice can live for only about a week in the absence of the host. Louse eggs, cemented to animal hair, hatch into nymphs, which are small, immature adults. The nymph moults three times before becoming an adult.