Every bird operates on a fixed energy budget, supplied by the diet. A nutrition program is built to give the bird what it needs to support growth, egg production or immune function, but the bird’s own physiology ultimately decides where that energy gets spent, especially under stress.
External parasites can pull from that energy bank. As the withdrawal happens, it shows up in growth and production losses instead of in a bad diet, and quietly enough that most producers never connect the two.
Where the Energy Actually Goes
Mites feed on blood, and that loss has to be replaced. Research on northern fowl mites has found that in high infestations, birds can lose up to 6% of their blood volume per day.(1) Replacing that blood, and healing the feeding sites left behind, both cost energy that would otherwise go toward the bird’s normal production.
Blood loss is only part of the withdrawal. Another study on poultry red mites measured what infestation does to a hen’s stress physiology directly. Infested birds showed a 1.5 fold increase in corticosterone, a hormone tied to physical stress, along with a 22% drop in beta globulin, a blood protein connected to immune function.(2) That combination points to two things happening at once, a stress response and a weakened immune system, both of which draw on the same limited energy supply needed for growth and egg production. The bird isn’t just losing blood. It’s running a low-grade stress response around the clock, and that has a cost.
Where the Losses Show Up
None of this shows up as a dramatic event. It shows up as numbers that are a little behind.
A study tracking commercial caged laying hens through a northern fowl mite infestation put real figures on that gap. Unmitigated infestations reduced egg production by 2.1 to 4.0%, individual egg weight by 0.5 to 2.2%, and feed conversion efficiency by 5.7%, adding up to a profit loss of $0.07 to $0.10 per hen over just a 10-week period.(3) Run that across a full size commercial flock and the number stops looking small.
What’s most telling is the researchers’ own explanation for where that loss actually comes from. They concluded the damage wasn’t primarily from the blood meals themselves, but from the metabolic cost of the bird’s body fighting the infestation, a tradeoff between spending energy on immune defense versus spending it on growth and egg production.(3) That’s the energy budget argument showing up directly in the research, not just as a way of describing it.
A separate trial on cage free layers found a similar pattern, with infested hens producing about 2% below the breed’s management guide while a control flock without mites ran 7% above it.(4) Nobody walking those houses would catch a swing like that by eye. It only shows up once someone compares the numbers against what the flock should be doing.
Why It’s Easy to Overlook
Part of what makes this hard to catch is that mites don’t build up overnight. A northern fowl mite can complete its full life cycle, egg to adult, in about a week, and that speed is exactly why a few mites can become thousands before anyone notices.(5) Once mature, an adult can also survive for weeks without feeding, longer in cooler, more humid conditions, which means a light infestation can sit quietly in a barn for a long stretch without forcing the issue.(6)
Layers and breeders tend to see more pressure from external parasites than broilers do. It’s less about the bird and more about the barn. Broilers turn over fast enough that most operations get a clean-out window between flocks to break the cycle, while layers and breeders stay in the same house for a much longer stretch with far less downtime to work with. That gap in opportunity, not anything specific to the species, is usually what decides how much of a foothold parasites get.
Checking birds and equipment at night, when mites are more active, can help catch an infestation earlier than a daytime walk alone. But timing your barn checks is only part of the picture. The bigger point is that the energy cost starts well before an infestation is severe enough to be obvious, so routine checks matter more than waiting for a visible sign.
What to Look For
Knowing where to look matters as much as when. Mites tend to collect around the vent, underneath the wings and around the head and face, all places that stay dark, warm and a little protected. Picking birds up and handling them is a more reliable way to find a problem than watching from a distance, since early infestations are often easier to find than they are to see.
A few visual cues are worth knowing specifically. Scaly leg mites burrow into the leg scales until they look raised, red and irritated against otherwise healthy, smooth skin, something that stands out clearly once you know to look for it. A different parasite, a burrowing flea sometimes called a stick flea, shows up on exposed skin like the face as small red scabs or pimple-like bumps rather than a crawling insect. And when something on a bird looks like a speck of dirt, it’s worth a second look before moving on. A few of those specks moving is usually the tell that it isn’t dirt at all.
If you’re ever unsure what you’re looking at, a photo sent to your veterinarian is often enough to confirm it before you commit to a treatment plan.
How Much is Too Much
Not every mite sighting calls for an emergency response, but there is a point where the energy drain becomes too large to ignore. The same economic research referenced above identified roughly 100 mites per bird as the threshold where infestations start producing measurable drops in egg production and feed conversion.(3) That number is a useful line in the sand for deciding when a mild case has become one worth treating rather than just watching.
Protecting the Energy Budget You’re Already Paying For
Biosecurity is still the cheapest way to avoid ever having this conversation. Clean clothes and boots before entering a barn help, even though people aren’t usually the main way parasites spread between operations. Rodents are a bigger risk than most producers think, especially as barns start looking like a warm place to move into for the winter. Keeping rodent populations down is as much a parasite prevention step as a general biosecurity one.
If a parasite problem is already established, treatment needs to match the life cycle, not just the population you can see today. Depending on the product, treatment may mean dusting or spraying the birds directly, treating litter, roosts, walls and cracks and crevices, or both. Permethrin is most often used against fleas specifically, while carbaryl is a more common choice for mites, and products containing tetrachlorvinphos and dichlorvos are typically applied to the housing and structures rather than the birds themselves. Most of these call for a second application roughly two weeks after the first, since a single treatment often misses eggs and other life stages that mature later. Bed bugs are the exception to a spray or dust approach entirely, since heat treatment or fumigation of the house tends to work better against them than a standard chemical application.
Whatever product is used, confirm the label is explicitly approved for use around laying hens. Eggs are collected daily, so there’s no withdrawal period like there is with meat animals, which means any residue issue shows up in the food supply right away rather than after time has passed.
For organic operations, or conventional producers who want a non-chemical option, there’s real research behind a couple of natural tools. In a university trial, hens dusted with diatomaceous earth carried significantly fewer northern fowl mites and weighed more than hens dusted with plain sand.(7) Neem oil has shown similar results specifically against poultry red mites, with one field trial recording a 92% reduction in mite numbers using neem oil traps placed around a commercial laying barn.(8)
None of these tools replace a relationship with your veterinarian, built before you need it rather than after.
How Ralco Can Help Support Your Flock
Treating an active infestation handles the parasite side. Supporting the bird through that stress is a separate piece, and it’s one that’s easy to overlook once the mites themselves are under control.
An infestation puts real strain on hydration, gut health and immune function all at once, the same systems any stress event taxes. That’s where Ralco can help, with natural technologies that are research-proven to support the bird through stress. They won’t treat the parasite itself, but they can help a bird through recovery. We can also help look at the diet itself as part of a broader recovery plan.
Bottom line, a nutrition program is built around giving the bird exactly what it needs and nothing it doesn’t. External parasites quietly work against that goal from a direction most pest control advice doesn’t talk about, not by touching the feed, but by spending the energy that feed was supposed to fund. Catching an infestation early isn’t just about bird comfort. It’s about protecting the return on a diet program you’re already paying for.
Questions?
Connect with the Ralco poultry team. Call 1-800-533-5306 or email PoultryHelp@RalcoAgriculture.com.
Want to Hear More?
Listen to Season 7, Episode 25 of Wing it Wisely, where Carmen Paulsen talks with Dr. Tim Broderick and Alea Gigliotti from the Ralco Poultry Team about identifying external parasites, where they hide and how to build a prevention and treatment plan that fits your operation.
References
- Murillo, A.C., & Mullens, B.A. (2017). A review of the biology, ecology, and control of the northern fowl mite, Ornithonyssus sylviarum (Acari: Macronyssidae). Veterinary Parasitology, 246, 30-37.
- Kowalski, A., & Sokół, R. (2009). Influence of Dermanyssus gallinae (poultry red mite) invasion on the plasma levels of corticosterone, catecholamines and proteins in layer hens. Polish Journal of Veterinary Sciences, 12(2), 231-235.
- Mullens, B.A., Owen, J.P., Kuney, D.R., Szijj, C.E., & Klingler, K.A. (2009). Temporal changes in distribution, prevalence and intensity of northern fowl mite (Ornithonyssus sylviarum) parasitism in commercial caged laying hens, with a comprehensive economic analysis of parasite impact. Veterinary Parasitology, 160(1-2), 116-133.
- Jarrett, R.A., Erasmus, M.A., Murillo, A.C., Scoles, K.L., Robison, C.I., Jones, D.R., & Karcher, D.M. (2022). Laying hen production and welfare in a cage-free setting is impacted by the northern fowl mite. Journal of Applied Poultry Research, 31(4), 100290.
- Murillo, A.C., & Mullens, B.A. (2017). A review of the biology, ecology, and control of the northern fowl mite, Ornithonyssus sylviarum (Acari: Macronyssidae). Veterinary Parasitology, 246, 30-37.
- Chen, B.L., & Mullens, B.A. (2008). Temperature and humidity effects on off-host survival of the northern fowl mite (Acari: Macronyssidae) and the chicken body louse (Phthiraptera: Menoponidae). Journal of Economic Entomology, 101(2), 637-646.
- Bennett, D.C., Yee, A., Rhee, Y.-J., & Cheng, K.M. (2011). Effect of diatomaceous earth on parasite load, egg production, and egg quality of free-range organic laying hens. Poultry Science, 90(7), 1416-1426.
- Lundh, J., Wiktelius, D., & Chirico, J. (2005). Azadirachtin-impregnated traps for the control of Dermanyssus gallinae. Veterinary Parasitology, 130(3-4), 337-342.