Can Parasites Be Found in Hen's Eggs?
25 July 2025
A Rare but Documented Occurrence
While it is very rare to find internal parasites inside a hen's egg, it is not impossible. There are occasional reports, primarily involving Ascaridia galli, a common roundworm of poultry, where adult worms or their eggs have been discovered within the egg contents or shell membrane. These incidents are unusual and typically associated with specific predisposing factors.
One of the reasons this phenomenon can occur lies in the unique anatomy of birds. In hens, the digestive, urinary and reproductive systems all converge at a single exit point called the cloaca. Eggs, faeces and urates are all passed out through this shared vent. While the egg typically moves one-way through the oviduct during formation, the close proximity of the digestive and reproductive tracts can, in rare circumstances, allow parasites or their eggs to find their way into the oviduct.
One of the reasons this phenomenon can occur lies in the unique anatomy of birds. In hens, the digestive, urinary and reproductive systems all converge at a single exit point called the cloaca. Eggs, faeces and urates are all passed out through this shared vent. While the egg typically moves one-way through the oviduct during formation, the close proximity of the digestive and reproductive tracts can, in rare circumstances, allow parasites or their eggs to find their way into the oviduct.
This cross-contamination is not the norm and usually requires exceptional conditions, such as:
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High parasite burdens, which increase the likelihood of aberrant migration
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Compromised immune function, which may weaken tissue barriers
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Stress or poor husbandry, which can exacerbate parasitic infections
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Cloacal reflux, a rare reversal of flow where material from the cloaca re-enters the oviduct
Importantly, the oviduct itself is not directly connected to the intestines, so parasites must either migrate aberrantly through tissue or be introduced via the cloaca. Most eggs pass through the reproductive tract cleanly and without issue.
Although the presence of worms inside eggs is disturbing when it happens, it's more of a biological anomaly than a routine risk. However, it does serve as a reminder of the importance of good parasite control.
Regular worm egg counts (WEC) and targeted treatment remain essential tools in maintaining poultry health and preventing heavy burdens that could lead to such rare complications.
Regular worm egg counts (WEC) and targeted treatment remain essential tools in maintaining poultry health and preventing heavy burdens that could lead to such rare complications.