The nose worm in roe deer

Among our big game species, the roe deer has second place in terms of range and demographic success. Since 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 his health. There are few common pathogens, few herd behaviors that do not promote infection, and the initial state is very clean.

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

The nose worm and its effects

Undoubtedly, the parasite that is causing the most damage in this ungulate is Cephenemyia stimulator , commonly known as “the nose worm or fly”. This disease is very common and in recent years has generated great concern among hunters and managers, due to the effects it unleashes.

This parasite comes from horseflies, which use the roe deer as a host and carry out the larval phase inside it. When they begin to grow, the larvae occupy the nostrils and pharynx of the specimen, this causes respiratory problems and makes it difficult for them to swallow food. As a consequence, it leads to other diseases that if the roe deer were healthy it would not contract, since the larva weakens them. Finally, after a slow and long-suffering process, the roe deer dies or is more easily exposed to predators. This disease affects mostly young and male animals.

In endemic areas, a change in the behavior of roe deer has been observed, avoiding open spaces at times when the flies are most active in flight and feeding in areas with greater vegetation cover. When they detect the presence of flies, and to prevent them from depositing the larvae around their nostrils, the roe deer defend themselves by lowering and shaking their heads, sneezing, kicking, and even undertake long runs and jumps. (Image source: ACE)

How has it reached our roe deer?

This diptera has a wide distribution throughout Europe, and is currently in full expansion. 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. Much of these roe deer came from France.

In the neighboring country, the existence of this disease is well established. For this reason, it is possible to think that the cefenemiosis that affects the Spanish northwest arrived in Asturias at the beginning of this century with an irregular introduction of roe deer from some point in Europe, where this disease is endemic.

One of the reasons for this phenomenon is the rise in temperatures and the increased mobility of people and goods across the continent. The diagnosis of the disease is usually made by necropsy, opening these cavities to check if the worm is present, which is not always possible when you want to keep the head as a trophy.

Hunting as a management method

The abundance of roe deer prior to the epidemic outbreak described has been, without a doubt, a circumstance that has favored its extension and severity. With fewer roe deer and in better health conditions, it is probable that the effect of the epidemic would have been less important, which is why we insist on reasonable management of this species, in order to prevent new relapses.

Likewise, and in order to avoid the extension of the process to distant territories, it is necessary to consider the adoption of some precautions in the transfer of the trophies obtained in the affected areas (boil the heads or freeze them).

The prevention and cure of these diseases is complicated, if not impossible, since they are transmitted by insects and roe deer are not sheep in a pen. So for the moment our efforts should be focused on continuing to improve knowledge of diseases to know when and why they occur.