4 minute read
Itching in the Scratch: Ecto and Endoparasites in Small/Backyard Flocks
By Linnea M. Tracy, VMD, MPH, MAM, DACPV
Parasite awareness isn’t just for mammalian patients! As more backyard chicken flocks pop up across Pennsylvania, there’s no better time to refresh your knowledge of the little organisms that can be a big headache for birds. Parasitism contributes to decreased egg production, weight loss, behavioral issues, feather loss, and physical discomfort. If you don’t regularly see poultry in practice or have been lucky enough to avoid these creepy critters since the North American Veterinary Licensing Examination, here’s a quick refresher of just a few common chicken parasites for your small flock practice.
Mites
Northern fowl mites, Ornithonyssus sylviarum, are the mites of greatest concern for most North American flocks. These hematophagous mites spend their entire lives on hens, so the best control strategy is to treat birds directly. If you suspect Northern fowl mites, check the area around the vent for erythema and scabs. You might notice that vent feathers are dirty from mite excreta, and you may even see some of the tiny, brown culprits scurry for shelter under feathers.
The key to mite control is prevention! Exclude wild birds from your coop to prevent introduction and keep your coop clean with opportunities for dust bathing. If you must introduce new birds to an established flock, quarantine newcomers for at least 14 days and regularly inspect them for signs of parasites before introducing them to your flock.
Tip-Offs
Chickens, like other birds, are careful not to betray illness or infestation. Any of the following subtle signs should prompt further investigation in flocks, as parasites could be a cause:
• Behavior changes—increased anxiety, flightiness, increased vocalization, pecking self or others, depression.
• Production changes—consistently decreased egg production or weight loss.
• Changes in appearance—feather loss; reddened, scabbing areas around the vent or under the wings; thickening or raising of leg scales; poor feather condition; comb or wattle pallor; excreta adhered to feathers; loose or bloody stool; abnormally wet litter.
ITCH ALERT!
Poultry bed bug infestations can cause significant anemia and drops in egg production. While poultry mites only occasionally bite humans, both human and poultry bed bug species can infest people and can be carried home (or accidentally carried into a flock). Keep your coops clean and use designated clothing when tending to your birds!
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EGGS-CUSE ME?
Ascaridia galli, the chicken roundworm, is rarely spotted inside eggs. Piperazine usage, an off-label deworming agent that temporarily paralyzes nematodes, may contribute to causing these egg invaders. If a paralyzed nematode is expelled into the cloacal area and regains its movement, it may reenter the oviduct rather than the rectum and be incorporated into an egg.
If you have questions about poultry parasites, get in contact with your local vet school poultry department or state extension agent.
Coccidia
Coccidian organisms may be too small to see with the naked eye but can cause flock-wide problems. These protozoa proliferate in the intestinal mucosa, causing loose or bloody stool, weight loss, dehydration, mortality, and failure to thrive. Poultry accumulate immunity to coccidia over time by low-level fecal-oral exposure, but by about 12 weeks of age, minimal oocysts should be found in a fecal flotation (unless you have used medicated feed). Clinical signs coupled with a bloom of fecal oocysts are a strong indication of coccidiosis.
Treating with a labeled dose of amprolium in the entire flock’s drinking water or feed is typically the most effective method to medically manage coccidiosis. Amprolium’s efficacy may vary by coccidian species, so the best offense is a good defense: Keeping the scratch and coop floor dry, mucking out, and top-dressing the area with shavings can help to reduce coccidian sporulation and the flock’s access to feces.
Worms
Intestinal nematodes and cestodes are a frequent refrain in client conversations about poultry. While heavy infestations are a concern for causing poor body condition, diarrhea, and production issues, the occasional intestinal parasite is quite normal for birds with access to outdoor scratch and forage. Periodic fecal flotations using pooled, fresh flock droppings can be useful in assessing nematode and cestode burden when interpreted in tandem with the flock’s clinical presentation. Sanitation is key in the prevention of endoparasites. Regularly mucking out the coop area and replacing shavings help to mitigate parasite loads, as does rotating your pasture. For cestodes, the single most effective means to reduce incidence is fly control. Place fly tapes or bait jars near, but out of reach of, your hens to decrease their consumption of flies that serve as intermediate hosts of cestodes.
Frequent prophylactic deworming of healthy small flocks is often unnecessary. The development of parasiticide resistance in poultry via overuse presents a real danger to our ability to medically manage clinically affected small and commercial flocks. Judicious use in small flocks should combine assessment of clinical presentation and informed interpretation of fecal flotation results.
About the Author: Linnea M. Tracy, VMD, MPH, MAM, DACPV, is a board-certified poultry veterinarian working with a commercial egg company based in Pennsylvania. She completed her poultry specialty training at the University of Georgia, where she gained experience in various poultry species and production styles before returning to Pennsylvania to practice. Dr. Tracy is passionate about poultry medicine and health education for veterinary professionals and students for both backyard and commercial-scale flocks. She can be reached at