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Key words: VKM, risk assessment, Norwegian Scientific Committee for Food and
Environment, Norwegian Food Safety Authority, biological control, Nematodes,
Phasmarhabditis californica, Moraxella osloensis.
Parasitic nematodes and associated bacteria are increasingly being used for biocontrol of
molluscs. Functionally, it is the bacteria that kill and thus control the targeted pests, but the
function of the bacteria is dependent on the nematodes, which should be regarded as
vectors of biocontrol. Although the nematodes and the bacteria have a symbiotic relationship
within such biocontrol formulations, it should be noted that they are not dependent on each
other in the wild, but can establish separate populations which can be free-living or hosted
by other organisms.
The biocontrol product Nemaslug 2.0 contains the nematode Phasmarhabditis californica
(strain P19D) and the bacterial symbiont Moraxella osloensis (unknown strain). The
nematode was first described in 2016 and has never been reported in Norway. The lack of
reports suggests that it is absent from Norway, but this conclusion comes with a high degree
of uncertainty since there have been limited search efforts. The climatic thresholds of the
nematode are not known, but its current distribution, spanning widely varying climates,
suggests that it could survive and establish in Norway. Natural spread from currently known
areas of establishment to natural habitats in Norway is ruled out due to the nematode’s
limited dispersal capacity. However, human-assisted spread (e.g. via the use of biocontrol
products) and establishment would be likely if Nemaslug 2.0 is allowed for use in open fields
in Norway. Use of Nemaslug 2.0 in greenhouses and other enclosed areas is not likely to
facilitate spread to natural habitats in Norway provided that residues are properly handled.
However, deposition of product residues from greenhouses to outdoor areas may result in
local establishment of the nematode in the vicinity of the deposition.
Phasmarhabditis californica has a broad host range and may parasitize both rare/endangered
and common mollusc species. However, there is no scientific evidence suggesting that the
nematode can affect natural populations of molluscs in wild habitats, or otherwise have
negative effects on biodiversity. The nematodes’ association with the bacteria Moraxella
osloensis is most likely lost, or at least weakened, in natural habitats, suggesting that the
nematode becomes less capable of killing its hosts in the wild. Phasmarhabditis californica is
not capable of harming or infecting humans.
The bacterial species Moraxella osloensis is already present in Norway in a few locations and
at a low abundance, and it may be native to Norway. Little is known regarding its distribution
in natural environments, but the literature shows that it can infect humans and other
mammals. In humans with immunodeficiency or other comorbidities, M. osloensis can cause
meningitis, vaginitis, sinusitis, bacteremia, endocarditis, and septic arthritis. The risk of
infection in people handling Nemaslug 2.0 can probably be substantially reduced by protective clothing and appropriate handling. We are not aware of any reported health issues
arising from use of the previous version of Nemaslug, which also contains M. osloensis.
Different strains of M. osloensis are known to vary in their sensitivity to antibiotics, and likely
in other traits too. Thus, the lack of information provided about the strain identity and
specific characteristics of the strain used in Nemaslug 2.0 generates a high degree of
uncertainty regarding its pathogenicity, climate tolerance, sensitivity to antibiotics etc.
