Numerous flying insects, mites, and other ectoparasites target livestock, spreading disease and causing significant health problems. Our Church’s Mobile Veterinary Service team knows that controlling parasites can be difficult, so we are providing information about the ectoparasites that are problematic for cattle, small ruminants, and pigs, along with helpful management tips.

Face flies

Face flies develop in freshly deposited manure. They are most active on hot, sunny days, accumulating on cattle’s faces and feeding on the protein-rich secretions from the eyes and nose, saliva, and any open wounds. Their abrasive mouthparts stimulate tear flow from the eyes, causing significant irritation.

Face flies also have a significant economic impact, because 12 to 14 flies on an animal’s face can decrease grazing time by one hour per day. In addition, these parasites are the primary vector for Moraxella bovis, a bacteria that causes pink eye (i.e., bovine keratoconjunctivitis [IBK]) in cattle and is the most common eye disease in breeding females and calves. Signs include tearing, tear-staining, and squinting, and the eye may appear cloudy or white and an ulcer may develop as the condition worsens. 

Face fly control is an important part of treating and preventing pink eye. Devices that target the head and face and allow animals to treat themselves frequently are most effective and include:

  • Backrubbers — Backrubbers allow cattle to treat themselves when they scratch.
  • Dust bags — Dust bags that are placed where cattle must pass underneath to get to water or mineral feeders and in positions where the animals must lift the bag with their head can be somewhat effective. 
  • Insecticide-impregnated ear tags — Pyrethroid tags significantly reduce face flies for several weeks.
  • Feed additives — Feed additives or an insecticide bolus can target face fly maggots breeding in fresh manure.

Ringworm

Ringworm commonly affects cattle and small ruminants, and can also affect pigs. The condition is a fungal infection caused most often by Trichophyton verrucosum, and the fungal spores can remain alive in dry environments for years. Transmission most commonly occurs through contact with an infected animal, but spore-contaminated grooming equipment can also spread infection. The fungal spores germinate and target the hair shafts and skin surface. Ringworm lesions appear as grey-white, circular, slightly raised areas on the skin that are treated by removing the lesion crusts and applying a topical antifungal agent. Lesions should be treated twice, three to five days apart. Prevention tips include:

  • Reducing animal density to help prevent contact
  • Increasing sunlight exposure
  • Keeping animals on dry lots
  • Frequently disinfecting grooming equipment

If you have infected animals, treat them as soon as possible, and burn the crusts to help prevent environmental contamination.

Mites

More than 250 mite species can infect humans and domestic animals. Mites that affect livestock include:

  • Cattle follicle mite — Demodex bovis infests cattle hair follicles and causes lesions on the neck, shoulders, and udder. Nodules form and can rupture and produce sores that range in size from a pin head to a chicken egg.
  • Cattle ear mite — Raillietina auris infests beef and dairy cattle, causing ear canal inflammation, ear discharge, and ulcerated lesions. In severe cases, hearing loss can occur.
  • Chorioptic scab mite — Chorioptes bovis infests cattle, sheep, and camelids, primarily on the head and feet. Most animals show no signs, but sensitive animals may stamp their feet, and chew and rub their legs.
  • Psoroptic ear mite — Psoroptes cuniculi infest sheep and camelids, causing inflammation and hair loss in the ear, wax accumulation, head shaking, and ear rubbing. Chronic cases can lead to anemia and weight loss.
  • Goat follicle mite — Demodex caprae infest young and pregnant does and dairy goats, causing lesions on the face, neck, and udder.
  • Scabies mite — Sarcoptes scabiei infest all domestic animals, except cats and guinea pigs. The mites burrow under the skin, defecate, and cause itchiness and hair loss.
  • Sheep scab mite — Psoroptes ovis infests sheep and cattle. Sheep lose significant wool and weight, while cattle typically develop skin lesions and hair loss. 
  • Sheep itch mite — Psorobia ovis infests all sheep breeds, causing dry, scruffy skin and hair loss. Infested sheep become restless and bite or rub affected areas, most commonly the neck, shoulders, face, flanks, and thighs.

Mite prevention tips include:

  • Inspecting animals for skin lesions and itchiness before purchase
  • Isolating newly acquired animals for three weeks
  • Cleaning living areas and providing fresh bedding for new animals
  • Disinfecting grooming tools and other equipment used on animals

Cattle grubs 

Adult cattle grubs are known as heel flies, warble flies, bomb flies, or gad flies. A female fly can lay up to 800 eggs on a single animal. When the eggs hatch, the larvae crawl down the hair and penetrate the host’s skin, and then migrate in the subcutaneous tissue, gradually increasing in size and eventually reaching the animal’s back. Swelling occurs at the site and the skin becomes perforated, allowing the larvae to breathe. Over the next 30 days, the larvae go through two molting phases, until the spring, when the mature larvae leave the site, fall to the ground, and penetrate the soil. The adult fly emerges in 35 to 60 days. These parasites can depreciate the carcass value because the tissue becomes greenish and jelly-like where they migrate and they injure the hide where they emerge. Systemic insecticides used during the autumn and early winter kill the larvae in their younger stages, before they can migrate through tissues and cause damage.

If you have concerns about ectoparasites affecting your livestock, contact our Church’s Mobile Veterinary Service team, so we can help devise an effective management plan.