Nasal Bots in Deer: Harmless but Irritating
Nasal bots are the larvae or "maggot stage" of a specialized
fly. In the scientific world this fly belongs in the genus
Cephenemyia. Biologists find them in a high percentage of
deer, particularly when a thorough examination of the head is
conducted. These bots are specific to cervids (members of the deer
family, such as elk and mule deer) in North America.
Nasal bots begin life when the adult fly lays a group of eggs
around the nose or mouth of deer. The small larvae within these
eggs are released when the deer licks the eggs. The warm, wet
saliva creates an environment that permits the 'hatching' of the
immature bots. These larvae then migrate to the nasal passages and
occasionally into the sinuses where they molt into larger stages of
the maturing larvae. The mature larvae then move to some very deep
cavities in the mouth called the retropharyngeal pouches. Finally,
the fully matured bots exit and pupate in the ground until emerging
as adult flies that begin the life cycle again.
These bots are an obvious minor nuisance to deer as they
irritate the lining of the nasal passages and move about in the
retropharyngeal pouches. Some sneezing and coughing of deer is
assumed to be the result of nasal bots. I have heard it falsely
reported that the snorting of deer is also a condition caused by
the bots. However, deer snort to provide a warning alarm to other
deer. Clinically, the bots do not cause the deer any harm. No
sores, infection, or other problems have been reported even when
the parasites are present in large numbers.
Hunters normally encounter nasal bots after the deer they
harvested begins to cool. After the deer dies, body temperature
falls and the bots begin to leave the nasal passages and
retropharyngeal pouches in search of more hospitable living
arrangements. These bots exit through the nose or mouth.
Occasionally they will be found while field dressing deer, in what
the hunter thinks is the body cavity. Actually these bots have
traveled down the trachea and appear to be in the body cavity of
the deer. Bots are also readily seen under a deer that is hanging
in some stage of the field dressing or skinning process. Bots can
also be found in truck beds after transporting a deer that has
significantly cooled. Nasal bots are not a public health concern.
They pose no disease threat to humans and do not harm the venison
in any way. Deer found to harbor these harmless parasites are
obviously quite safe for human consumption and should not be