Sweet itch, Queensland itch, seasonal recurrent dermatitis, and summer itch are all common names for a condition in horses caused by hypersensitivity to the saliva of Culicoides sp. Common affected areas include the tail head, mane, ears, and ventrum. Alopecia occurs secondary to pruritus.
Horn Flies, Face Flies, and Stable Flies
Phormia regina A member of the family Calliphoridae, Phormia regina is an important cause of secondary myiasis, or wound myiasis with a tendency to invade not only necrotic tissue, but fresh tissue as well. Commonly known as the black blow fly, these flies are ubiquitous in the United States; times of peak activity vary by climate.
Horse Flies, Deer Flies, and Black Flies
A feeding female Tabanus melanocerus. Female Tabanids are well known blood-feeders but will also feed on honeydew and nectar as the males do. When biting a host, they cut the skin and lap up the blood that pools on the skin. This direct blood contact gives them the ability to act as a mechanical vector for many diseases. They also serve as biological vectors for Trypansosma theileri and Elaeophora schneideri.
Simulium sp. female
Simulium, also known as the "buffalo gnat," "black fly," or "humpback fly," are biting flies that swarm when they attack. There are reports of Simulium attacks resulting in the death of livestock and wildlife as a primary cause. Simulium is also known to vector various viruses such as Eastern Equine Encephalitis and Vesicular Stomatitis, along with various protozoa and nematodes such as Leucocytozoon and Onchocerca, respectively.
Simulium sp. larvae
Simulium lay their eggs on stones or plants just below the surface of the water in running streams. The eggs hatch in 4 to 12 days and the larvae attach themselves to rocks by means of a posterior organ that is armed with small hooks. Their anterior is equiped with a pair of brush-like organs with which they trap and ingest other insects.
Nodules on the backs of cattle caused by encysted Hypoderma larvae, said to be in the, 'warble' stage. The larvae cut small holes or pores in the backs of cattle through which they respire. This stage lasts approximately 30 days before the larvae emerge through the pores and begin pupation on the ground.
Migrating first stage larvae of Hypoderma lineatum found on necropsy of a bovine. Adult female Hypoderma lineatum deposit their eggs below the hocks on the hair of cattle during the spring, the eggs hatch, larvae penetrate, and may be found around the esophagus during the winter.
Oestrus ovis larvae in the nasal turbinates of a sheep head cross section. Though the adults do not feed on animals, Oestrus is still considered parasitic as its larvae feed solely off the bodily fluids of their host. "False gid" is a condition wherein the larvae erode the bone of the skull and damage the brain, causing neurologic signs.
Keds (Wingless Flies)