Status 6 april 2020, conclusion
In total eight wild boars were submitted for post-mortem investigation. Six of them were found dead, two were shot because of their aberrant behaviour.
The cause of death of five of the six examined wild boar found dead, is still unclear. One died of a lung condition caused by Pasteurella multocida. Investigation of the two shot wild boar revealed that one boar had a lung condition caused by lungworm and an infection with Pasteurella multocida. The other shot wild boar had an inflammation of the spinal cord. The cause of this inflammation could not be retrieved. For the other five wild boar found death, could be concluded that no common pig diseases or toxins were found.
Status d.d. 2 juli 2019
Since the early part of 2019 there has been increased mortality among the wild boar at the Veluwe. Most of the dead wild boars were in good condition. It is not unusual to find dead wild boars, especially in nutrient-poor years or after a dry period. But in that case, the animals are mostly in poor condition. However until mid-June of this year more dead wild boars have been reported than on average in previous years. None of these boars were diagnosed with African swine fever or classical swine fever (CSF). Six wild boars have been extensively researched by the Dutch Wildlife Health Centre (DWHC). One boar died of bacterial pneumonia, but no cause of death was found for the other five wild boars. Various pig diseases and toxins could be excluded as a cause of death.
The Fauna Management unit Gelderland receives an average of 20 reports of wild boars found dead with an unknown cause of death. This year in mid-June around 60 reports were received. In the first three months of 2019, it was noticeable that it mainly concerned sows. The sows were pregnant or had recently given birth to piglets. In the following months, more adult males, juveniles, and piglets were found dead than sows.
Dead wild boar were mainly found in the Midden Veluwe, with a clear “concentration” at Hoog Buurlo, Deelerwoud and National Park de Hoge Veluwe, see map.
One of the reasons for the increased number of reported dead wild boars may be due to greater attention regarding African swine fever (ASF) in Belgium and Eastern Europe. As no special increase in mortality is reported from other provinces with wild boars, it is unlikely that the increase in reports can only be attributed to increased vigilance. Moreover, the way and location where most of the wild boar were found, was remarkable: for example in the middle of a path, as if they have fallen over, or lying in the middle of the moor, as if they are sleeping.
All wild boars found dead for which there is no other clear cause of death (e.g. traffic accident, bag (shooting), poaching) are considered as an ASF suspicion and are sampled, in accordance with the ASF protocol. So far all wild boars investigated have been tested negative (no virus detected) for ASF and Classical swine fever. As long as ASF is not ruled out in a specific area, animals cannot be examined further. If a “fresh” dead wild boar is found, the FBE Gelderland consults with the Dutch authority (NVWA) whether it can go to DWHC for further investigation.
In April a group of experts (pig specialists from the Faculty of Veterinary Medicine and from pig veterinary practices, and experts from the GD, DWHC, NVWA, WBVR, the Ministry of LNV, FBE-Gelderland and a number of fauna managers) discussed the outcomes of the post mortem examinations and negative test results. During this meeting, various diseases and signs were discussed that could provide a possible explanation for the increased mortality. Subsequently, further research on toxins was scheduled.
A possibility for the mortality could be botulism, caused by botulinum toxin. In this case, the animals die quickly and thus have a so-called negative post-mortem (there are no visible abnormalities). However, testing this is very complicated. Moreover, botulism is rare in pigs and if the cause of death were caused by these toxins, it is expected that increased mortality will also occur in other animal species, which is, as far as we know, not the case. That is why botulism toxin has not (yet) been tested.
Update dated 13-8-2019: The causative agent of botulism has not been detected.
The cause of death of five of the six animals investigated remains unclear. The cause of death of one wild boar is clear: pneumonia due to Pasteurella multocida infection. Concerning the other wild boars, there is no evidence of any of the known pig diseases or toxins being present in these animals.
ASF: African swine fever
DWHC: Dutch Wildlife Health Centre
GD: Royal GD, animal health
FBE: Fauna management unit
IAV (-S): Influenza A Virus (-swine)
CSF: Classical swine fever
LNV: Ministry of Agriculture, Nature and Food Quality
NVWA: Netherlands Food and Consumer Product Safety Authority
PRRS-virus: Porcine reproductive and respiratory syndrome-virus
PSS: Porcine Stress Syndrome
VHL: Dr. van Haeringen Laboratorium
VMDC: Veterinary Microbiological Diagnostic Center
VPDC: Veterinary Pathological Diagnostic Center
WBVR: Wageningen Bioveterinary Research
WFSR: Wageningen Food Safety Research
Photo banner Wild boar: Bas Worm