Meningeal Worm (Parelaphostrongylus Tenuis) as a Cause of Mortality in the Restored Elk (Cervus Canadensis) Population in Missouri, Usa

Abstract

: Meningeal worm ( Parelaphostrongylus tenuis) is an important cause of mortality of elk ( Cervus canadensis) in populations in the eastern US and has been implicated in the failure of several restoration attempts. From 2011 to 2013, the Missouri Department of Conservation translocated 108 adult and yearling elk from Kentucky (US) to southern Missouri (US) to establish a free-ranging population. From release in spring 2011 through August 2015, we monitored 167 elk (adult, yearling, and calf) to determine causes of mortality. Of 78 mortalities, 26 (33%) were linked to meningeal worm based on necropsy results and/or observed behavior; this group included 19 elk with confirmed or suspected cases of meningeal worm infection that died of other proximate causes. Other important mortality sources included euthanasia ( n=11, 14%), emaciation ( n=7, 9%), and predation ( n=5, 6%). Eleven of the 26 (42%) meningeal worm-related mortalities were adults, and 22 (85%) were female. Meningeal worm was an important cause of mortality during the restoration of Missouri elk, potentially contributing to the loss of 16% of the monitored individuals. Greater mortality in adult female elk could reduce initial population growth by limiting reproductive output in the restored herd, especially given that females were disproportionately affected in Missouri. Because translocated Missouri elk undoubtedly were exposed to meningeal worm in Kentucky, our results could be explained by exposure to a different genetic strain of meningeal worm once in Missouri, loss of immune response due to translocation, increased dose of larval worms, or some unquantified factor.

Survival and cause‐specific mortality of elk Cervus canadensis in Kentucky, USA

“…Infection of P. tenuis was originally thought to be a serious concern for elk restoration efforts in the eastern USA (Larkin et al 2001(Larkin et al , 2003a, but it resulted in only 12 mortalities among our sample of Kentucky elk (5.1%; Table 1). In contrast, a total of 24.0% of mortalities in the recently reintroduced elk population in Missouri, USA resulted from P. tenuis infection (Chitwood et al 2018). This was more similar to what was reported in the Kentucky founder group, with 24.8% (36/145) of all mortalities being suspected from P. tenuis infection; although, only 5.5% (8/145) were confirmed (Larkin et al 2003a).…”

“…The presumed average density of deer in southeastern Kentucky is approximately 3.6 deer km -2 (KDFWR unpubl. ), whereas elk released into Missouri appear to inhabit an area with possibly greater deer density (Chitwood et al 2018). Thus, P. tenuis may not be a concern in established elk populations, but it could still impede reintroduction efforts, particularly in areas with moderate to high white-tailed deer densities.…”

Genetic analyses of the parasitic nematode,Parelaphostrongylus tenuis, in Missouri and Kentucky reveal unexpected levels of diversity and population differentiation

“…Further, we found that the previously published mtDNA haplotype of P. tenuis from Maryland, USA, differed at 30 or more bp from the majority of our Missouri and Kentucky haplotypes and that three haplotypes detected in Kentucky clustered with the Maryland haplotype. Taken as a whole, our results support previous suggestions that genetic differences among populations across the range of this parasite may have contributed to differences in susceptibility to infection between hosts that have acquired immunity to parasite lineages in their home ranges (Chitwood et al ., 2018). Translocation of such locally adapted individuals risked exposing them to strains to which they were immunologically naive.…”

“…When translocated from Kentucky to Missouri in the springs of 2011–2013 (Dent, 2014), elk experienced high morbidity and mortality due to P. tenuis infections (Chitwood et al ., 2018). In Kentucky, the persistence of some elk with P. tenuis and no clinical signs of disease (Larkin et al ., 2003), and the observation of decreased mortality from P. tenuis (Slabach et al ., 2018) suggest that the elk herd has become less susceptible to the local variant of P. tenuis .…”

Resource selection of a recently translocated elk population in Missouri

“…We censored relocations of all elk with <30 days of telemetry data during a season or year, and we censored relocations with obvious location error (e.g., relocation was in the wrong county). Because of aberrant behavior, we censored relocations of all elk suspected of infection with meningeal worm ( Parelaphostrongylus tenuis ; n = 13), an important cause of mortality during the restoration (Chitwood et al ). Finally, we censored relocations that occurred outside the extent of GIS layers, were recorded <4.5 hours after the previous relocation, or were recorded ≥24 hours apart.…”