The nose worm in roe deer

Among our big game species, the roe deer is second in range and demographic success. From its minimal spatial expression at the end of the first half of the 20th century, it has spread to almost all ecosystems in Spain and Europe, from northern latitudes to the Strait of Gibraltar. Much of this success is due to its health. There are few common pathogens, few pack behaviors that do not promote infection, and the initial state is very clean.

Over the years, some parasites have gained importance, modifying the growth rate of roe deer populations in different parts of Spain and Europe, as their numbers increased.

The nose worm and its effects

Without a doubt, the parasite causing the greatest damage to this ungulate is Cephenemyia stimulator , commonly known as the "nose worm." This disease is very common and has generated great concern among hunters and managers in recent years due to its effects.

This parasite originates from horseflies, which use roe deer as a host and undergo their larval stage inside them. As they begin to grow, the larvae occupy the roe deer's nostrils and pharynx, causing respiratory problems and making it difficult for them to swallow food. This leads to other diseases that healthy roe deer would not contract, as the larvae weaken them. Finally, after a slow and painful process, the roe deer dies or is more easily exposed to predators. This disease mostly affects young and male animals.

In endemic areas, a change in roe deer behavior has been observed, avoiding open spaces during times when flies are most active and feeding in areas with greater vegetation cover. When they detect the presence of flies, and to prevent them from laying larvae around their nostrils, roe deer defend themselves by lowering and shaking their heads, sneezing, kicking, and even starting long runs and jumps. To observe these specimens closely and determine if they are suffering from the disease, you can purchase our recommended DELTA BINOCULARS . (Image source: ACE)

How did it get to our roe deer?

This fly has a wide distribution throughout Europe and is currently expanding rapidly. Throughout the last decade of the 20th century, numerous reintroductions of roe deer were carried out in different parts of Spain and Portugal. Some are documented; others were simply irregular. Many of these roe deer originated in France.

The existence of this disease is well documented in the neighboring country. Therefore, it is reasonable to believe that the zephenemiosis affecting northwestern Spain arrived in Asturias at the beginning of this century with the irregular introduction of roe deer from somewhere in Europe, where the disease is endemic.

One of the reasons for this phenomenon is rising temperatures and the increased movement of people and goods across the continent. Diagnosis of the disease is usually made by necropsy, opening the cavities to check for the presence of the worm, which isn't always possible when the head is to be kept as a trophy.

Hunting as a management method

The abundance of roe deer prior to the epidemic outbreak described above was undoubtedly a factor that favored its spread and severity. With fewer roe deer and those in better health, the impact of the epidemic would likely have been less significant. Hence, we insist on reasonable management of this species in order to prevent further relapses.

Likewise, and in order to prevent the spread of the disease to distant territories, it is necessary to consider taking certain precautions when transporting trophies obtained in affected areas (such as boiling or freezing the heads).

Preventing and curing these diseases is complicated, if not impossible, given that they are transmitted by insects and roe deer are not sheep kept in a corral. So for the time being, our efforts must focus on continuing to improve our understanding of these diseases to understand when and why they occur.

In this episode 3 of our series "The Northern Roe Deer" we see how to act once the roe deer has been shot to help in the study of this worm: