Toxic caterpillars pose a greater health risk

Poisonous caterpillars of the oak processionary spinners are spreading

23/04/2012

The spread of oak processionary spinners in Germany has widened significantly in recent years. This is accompanied by a significant health risk from the poisonous hair of the caterpillars. The dry and warm spring weather offers ideal conditions for the propagation of the oak processionary moths. Recreation and settlement areas are increasingly being affected, reports the Julius Kühn Institute (JKI), warning of the health risks posed by the larvae of the oak processionary moths.

Oak Processionary Spinner Plant and health pest
According to the Julius-Kühn-Institut, the mild dry spring offers excellent propagation conditions for the oak processionary moths, so that again this year many caterpillars can be expected. According to the JKI, this has a negative impact on both plant life and humans. On the one hand, the caterpillars of the oak processionary spider are plant pests, which can eat whole tree areas bald and on the other hand threaten the humans in contact with the burning hairs of the caterpillar considerable health consequences - the oak processionary spinners are also considered as health pest. The growing spread of the animals is therefore viewed with concern by the health authorities. In a total of ten states, the oak processionary spinners are now widespread, with Baden-Württemberg, Berlin, Brandenburg, Saxony-Anhalt, North Rhine-Westphalia and Bavaria are the hardest hit, reports the JKI.

The hair of caterpillars causes allergic reactions
The fine stinging hairs of the oak processionary moth larvae can cause severe allergic reactions on contact with the skin or when inhaled and can become a considerable health risk. The human pathogenic potential of oak processionary moths is based on the so-called burning hairs, „which are formed from the third instar“, reported JKI. Until the caterpillars reach the sixth and final larval stage, „increases the number and length of stinging hair with each skinning“, so the JKI on. The stinging hairs are due to the nettle poison thaumetopoein contained there a danger to human health. At the end of April and the beginning of May, according to JKI, the „Caterpillars of the nondescript gray moth“ and undergo six larval stages until pupation around June. During this time, the oak processioners pose a significant health risk. In the affected areas „health effects on forest visitors must be feared“, so the latest communication from the JKI.

Difficulty breathing, eye irritation, skin irritation and pseudoallergic reactions
However, the endangerment of the caterpillars of the caterpillars persists even after the slippage of the oak processionary moths. In the old webs of the larvae, the stinging hairs are present in high concentration and are preserved there for a long time, so that the old caterpillar nests represent a permanent source of danger. „The risk of contact remains for years in the infected areas“, explained the JKI. Actually, the burning hairs serve the caterpillars for protection against natural enemies. But even in humans, they can cause severe health problems such as difficulty breathing, eye irritation, skin irritation and pseudoallergic reactions. In addition to the health risks and the „Moreover, the heat-loving and oak-specialized species of butterflies pose massive problems for forestry“, reports the JKI, which as a Federal Research Center for Cultivated Plants in Germany has also committed itself to monitoring plant and health pests. Often the caterpillars are responsible for the so-called nettle fever.

Climate change favors the spread of oak processionary spinners
According to the experts, climate change is making a significant contribution to the growing popularity of oak processionary spinners. The dry, warm weather conditions in the spring create an ideal condition for the spread of health-threatening animals. Thus, the oak processionary spinners have been able to multiply considerably in Germany in recent years, and have moved further and further northwards. The oak processionary spinners have recently reached Lower Saxony and Mecklenburg-Vorpommern. Experts are therefore looking for strategies that will allow effective control of the oak processionary spinners without harming the health of the population or the plants. At the beginning of March, representatives of the relevant institutions (for example JKI, Federal Ministry of Agriculture, Federal Institute for Risk Assessment, Federal Environmental Agency, representatives of forestry research institutes, official plant protection services and public health authorities) had an expert discussion on the topic „Processional spinners: facts, consequences, strategies“ met in Berlin and discussed there about possible approaches to combat the oak processions.

Avoid contact with the caterpillars and webs
In order to avoid health risks from the stinging hairs of the oak processionary spinners, the contact with the animals and in particular with the nests should urgently be avoided. However, the fine hairs can also be transported by air, so that in some circumstances, the proximity to a nest is sufficient to cause the health problems. At the latest after the hatching of the larvae, the webs should be removed by a specialist in order to avoid long-term health hazards. (Fp)

Image: Caterpillar dermatitis (Lepidopterism) by oak processionary moth (Thaumetopoea processionea) Photo: Daniel Ullrich.