The beaver stays the focus species of the DWHC in 2024

17 April 2024

As in 2023, the beaver (Castor fiber) is the focus species at DWHC in 2024. The choice for the beaver as the focus species is motivated by the desire to receive more dead beavers for research into their cause of death. This allows us to better investigate what health issues beavers may have and to gain more knowledge about certain diseases and pathogens, such as tularemia and toxoplasmosis. Beavers are aquatic rodents and can provide insight into the presence of pathogens in that environment. See also the more extensive background information in the article: Beaver DWHC focus animal of 2023.

Results first quarter of 2024

In the first quarter of 2024, two dead beavers were collected for post-mortem investigation: an adult female beaver from the province of Gelderland (village Druten) and an adult male beaver from the province of South Holland (village Spijkenisse).

The beaver from the village Druten died due to trauma but had an underlying moderate liver inflammation (cause not entirely clear, possibly due to a worm infection) and a mild intestinal inflammation caused by worms. The beaver from the village Spijkenisse was a traffic victim and had a severe brain inflammation, which increased its risk of trauma. The investigation into a possible cause for the inflammation is still ongoing.

Results 2023

In 2023, a total of eight dead beavers were collected for post-mortem investigation at the DWHC. These included four adult males, three adult females, and one subadult male. They were found in the province of North Brabant (municipalities of Waalre, Oss, Landerd), province of Gelderland (municipalities of Overbetuwe, Druten, Neder-Betuwe), province of Flevoland (municipality of Lelystad), and the province of Friesland (municipality of Ooststellingwerf).

Two of the eight cases stood out. The first involved a beaver that died from suffocation after getting trapped in a fence (see article https://dwhc.nl/en/2023/03/results-examinating-beavers-first-two-months-2023/). The necropsy showed superficial lung hemorrhages and multiple bleedings with edema in the back muscles. No underlying diseases were found in this animal. The owner of the fence immediately took measures and removed part of the fencing.

The other notable case in 2023 involved an adult female that died as a result of a bacterial middle ear infection and brain and meningeal inflammation. The inflammations were associated with the bacteria Clostridium sp., Streptococcus agalactiae, and three other bacteria. This animal had also choked during death (https://dwhc.nl/en/2023/10/beaver-with-meningitis-due-to-an-ear-infection/). The case was notable because in 2018 a severe illness due to middle ear infection had also been diagnosed in a beaver (https://dwhc.nl/en/2018/06/beaver-with-mid-ear-infection/).

Additionally, in January there was a beaver with lung and kidney inflammation, and another beaver with mild lung inflammation and an overfilled bladder. The causes could not be determined. Both had Stichorchis subtriquetrus flukes in the cecum, but without clinical problems. This worm uses the beaver as its final host and various snails as possible intermediate hosts (including Planorbis vertex, Lymnea ovata, Bithynia tentaculata, and Succinea putri). Under normal circumstances, the worm is not pathogenic for the beaver.

The intake policy for dead beavers was primarily aimed at collecting sick, euthanized, or freshly found dead beavers, but not obvious traffic victims. Nevertheless, in half of the examined beavers (4 out of 8), there were only signs of trauma (fractures, ruptures, and/or hemorrhages) consistent with a collision, without evidence of underlying diseases that would increase the risk of trauma. However, one animal showed signs of poor rib mineralization, and another had very mild lung inflammation due to a worm infection, but the species of worm could not be determined.

Which beavers are eligible for research?

An animal can only be examined at DWHC if they are ‘freshly’ dead. These can be sick animals that have been euthanized and dead animals that are known not to have been there the previous day. If in doubt, you can consult with the DWHC staff, who also consider, for example, weather conditions in their decision.

If an animal showed abnormal behavior before being euthanized, DWHC requests, if possible, a video of the behavior before they died. If the beaver was found dead, DWHC would like to receive a photo of the animal as they were found.