Lice and Mites in Dairy Cattle

Itching, rubbed-out hair and restless cows are common signs of external pests. This guide explains what to look for, how these pests spread and what to ask your veterinarian.

Key points

Itching and hair loss in a group often point to lice or mites.
Get a diagnosis, because other skin problems look similar.
Treat the pen, tools and new arrivals, not only the single animal.
Follow label and vet directions, including milk and meat withdrawal times.

Why external pests matter

Lice and mites live on the skin and hair. They irritate the animal, cause itching and rubbing, and can leave bare patches. Heavily affected animals may eat less, lose condition and become restless, which can show up in growth and milk.

These pests tend to build up in winter and when animals are thin, crowded or stressed. A calf or heifer group in a tight pen can pass them along quickly, and a thick winter coat makes them harder to see.

Do not dismiss mild itching. A few rubbed spots can be the first sign of a problem that will spread through the pen over the following weeks, so early attention saves effort later.

Signs to look for

Check animals up close, in good light, and part the hair in the areas where pests collect. Common spots include the neck, shoulders, back, tailhead and around the eyes and ears.

Different pests cause different skin changes, and some skin problems that look similar are not parasites at all. That is why a vet or lab should confirm what you are dealing with before anything is applied.

Make a habit of looking at coats during routine handling such as moving, trimming or vaccinating. Spotting early changes is far easier when you are already close to the animal.

Constant scratching or rubbing on posts and gates
Hair loss, thin patches or rough coat
Scabs, crusting or thickened skin
Visible lice or eggs attached to hair
Restless animals and reduced feed intake
Several animals in the same pen showing the same signs

How they spread

Direct contact is the main route. New arrivals, shared pens, borrowed animals and fairs or shows can all bring pests onto the farm. Grooming tools, brushes, halters and blankets can carry them between animals.

Heavily infested animals may serve as a source for the whole group. Treat the pen and the shared equipment as part of the problem, not only the animal.

Wild birds and rodents can also carry some pests into barns, and bedding that has been in contact with affected animals can hold them for a time. Clean out and replace bedding in heavily affected pens as your vet advises.

Getting a diagnosis

Ask your veterinarian to examine affected animals and confirm the cause. Some mange mites require skin scraping to identify, and skin conditions such as ringworm or nutritional problems can look similar.

Take notes before the visit: which animals, which pen, when it started, how long animals have been on the farm and whether new stock arrived recently. That history saves time and helps the vet pick the right next step.

Your vet may take a small sample from the skin or hair and look at it under a microscope. Ask what the result means for the other animals in the pen, not only the one sampled.

Control and prevention

Treatment choices belong to your vet. Products vary in what they target, which ages they can be used on and whether they are allowed in lactating cows. Follow the label and your vet's directions exactly, including any repeat steps they advise.

Management supports any treatment. Keep pens uncrowded, clean and dry. Clean or replace shared grooming tools. Include new arrivals in your quarantine routine so pests do not move into the main herd.

Inspect new animals before they join the group
Do not share brushes or blankets between pens without cleaning
Reduce crowding in winter housing
Keep records of which animals were affected and when

Safety, withdrawal and common mistakes

Wear gloves when handling animals with skin disease and wash your hands afterward, because some skin conditions can affect people. Follow label directions for handler protection. Milk and meat withdrawal times on the label or set by your vet must be followed exactly.

Common mistakes include treating the one itchy cow and ignoring the pen, using a product on the wrong age group, and skipping the follow-up check. Another is blaming pests when the real problem is a feed or skin issue.

Write down the pen, the date and the steps taken. If signs return after treatment, those notes will help your vet decide whether the diagnosis, the product or the management needs to change.

When to get help: Call your veterinarian if animals have widespread hair loss, scabbing, thickened skin or are losing condition. Ask about handler safety if people on the farm develop a rash after working with affected cattle.

Sources and further reading

Organization homepages are linked so you can search them for current guidance on this topic.

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