Identification of dorsal-spined larvae from free-ranging wapiti (Cervus elaphus) in southwestern Manitoba, Canada

Dorsal-spined first-stage larvae recovered from feces of free-ranging wapiti (Cervus elaphus) were passaged through snails (Triodopsis multilineata) and two hand-raised white-tailed deer fawns (Odocoileus virginianus). A total of 74 adult Parelaphostrongylus tenuis were recovered from the fawns; no other protostrongylid nematodes were recovered. The study indicates that wapiti may be infected with natural infections of meningeal worm and pass larvae suitable for transmission to gastropod intermediate hosts. Wapiti from areas endemic with P. tenuis should not be translocated to areas currently free of the parasite.     

Muscleworms, Parelaphostrongylus andersoni (Nematoda: Protostrongylidae), discovered in Columbia white-tailed deer from Oregon and Washington: implications for biogeography and host associations

Parelaphostrongylus andersoni is considered a characteristic nematode infecting white-tailed deer (Odocoileus virginianus). Host and geographic distribution for this parasite, however, remain poorly defined in the region of western North America. Fecal samples collected from Columbia white-tailed deer (O. v. leucurus) in a restricted range endemic to Oregon and Washington, USA, were examined for dorsal-spined larvae characteristic of many protostrongylid nematodes. Multilocus DNA sequence data (internal transcribed spacer 2 and cytochrome c oxidase subunit 1) established the identity and a new record for P. andersoni in a subspecies of white-tailed deer previously unrecognized as hosts. Populations of P. andersoni are now recognized along the basin of the lower Columbia River in Oregon and Washington and from south-central Oregon on the North Umpqua River. Current data indicate a potentially broad zone of sympatry for P. andersoni and Parelaphostrongylus odocoilei in the western region of North America, although these elaphostrongylines seem to be segregated, respectively, in white-tailed deer or in black-tailed and mule deer (Odocoileus hemionus) at temperate latitudes. The geographic range for P. andersoni in white-tailed deer is extended substantially to the west of the currently defined limit in North America, and we confirm an apparently extensive range for this elpahostrongyline. These observations are explored in the broader context of host and geographic associations for P. andersoni and related elaphostrongylines in North American cervids.     

Meningeal worm in free-ranging deer in Nebraska

The meningeal worm (Parelaphostrongylus tenuis) was found in 22 (7%) of 300 white-tailed deer (Odocoileus virginianus) (257 adults, 43 fawns) examined from Nebraska (USA) during November 1996. None of 53 mule deer (Odocoileus hemionus) (47 adults and 6 fawns) examined were infected. Twenty-two white-tailed deer from 18 counties in eastern Nebraska were infected with Parelaphostrongylus tenuis. This is the first record of P. tenuis in white-tailed deer from this state.     

Mortality of fallow deer (Dama dama) experimentally-infected with meningeal worm, Parelaphostrongylus tenuis.

Six fallow deer (Dama dama) fawns died after receiving 25 to 150 infective larvae of Parelaphostrongylus tenuis. Fawns given higher doses usually died sooner (6 to 23 days) than those given lower doses (54 to 67 days). Early deaths were associated with severe acute peritonitis resulting from perforation of the intestinal wall; later deaths were associated with paralysis and inability to rise. Numerous adult P. tenuis were found within neural tissues of the brain and spinal cord in the three fawns with paralysis. One white-tailed deer (Odocoileus virginianus) exposed to infective larvae from the same source survived infection without exhibiting clinical signs and began passing larvae in feces 88 days post-exposure. At the doses used in this study, meningeal worm caused fatal infections in fallow deer. Results are compared to published observations of fallow deer naturally-infected with P. tenuis.     

Meningeal worm in deer from western Nebraska

One hundred seventy-eight white-tailed deer (Odocoileus virginianus) and 275 mule deer (Odocoileus hemionus) collected from locker plants in the western 2/3 of Nebraska (USA) in November 1997 were examined for the meningeal worm (Parelaphostrongylus tenuis). Parelaphostrongylus tenuis was identified in 17 (10%) of 168 white-tailed deer and in one (<1%) of 273 mule deer. This is the first naturally occurring infection of P. tenuis recorded in a mule deer.     

Gastropod availability and habitat utilization by wapiti and white-tailed deer sympatric on range enzootic for meningeal worm

Gastropod occurrence and the utilization of habitat by sympatric populations of wapiti (Cervus elephus) and white-tailed deer (Odocoileus virginianus) on range enzootic for meningeal worm (Parelaphostrongylus tenuis) were studied on Cookson Hills Wildlife Management Area (WMA) in eastern Oklahoma. Visual observations and fecal pellet group transect data indicated that wapiti spent the majority of their time in open fields and meadows where we recovered the least numbers of gastropods. Although deer were frequently observed in open areas, visual sightings and transect data indicated that they spent more time in forested areas where we recovered the most gastropods. Gastropods harbored low numbers of P. tenuis larvae (0.00 to 0.06 larvae/gastropod) in all habitat types with the greatest recovery from red oak white oak-hickory forests (0.34 larvae/gastropod). Our results indicate that the reason a viable wapiti herd exists on Cookson Hills WMA in a P. tenuis enzootic area is at least partially because of the habitat preference by wapiti and the reduced availability of infected gastropods in the selected areas prefered by the wapiti. We were not able to detect any free-ranging wapiti that were shedding P. tenuis larvae nor were we able to detect past or sub-clinical infections with P. tenuis in wapiti.     

Parelaphostrongylus tenuis in New Brunswick: the parasite in white-tailed deer (Odocoileus virginianus) and moose (Alces alces)

Research was initiated in 1983 to investigate the ecology of Parelaphostrongylus tenuis in New Brunswick. The objectives were to determine the prevalence and intensity of infection in white-tailed deer, and to determine whether or not moose feces contained first stage larvae, signifying the completion of the life cycle of P. tenuis in this host. Forty-nine percent of deer pellet samples were positive and 60% of deer heads contained adults of P. tenuis. None of the moose pellet samples contained first stage larvae.     

Repeated low-level infection of white-tailed deer with Parelaphostrongylus andersoni

Two white-tailed deer (Odocoileus virginianus) were given 5 infective larvae of Parelaphostrongylus andersoni each weekday for 13 weeks. At 23 weeks one of these deer and a control were challenged with single doses of 200 third-stage larvae. Repeated low-level infection of P. andersoni resulted in a sustained leukocytosis with an absolute eosinophilia which declined only after administration of larvae ceased, partial failure of worms to become established in the musculature, reduced numbers and reduced viability of eggs in the lungs, and an apparent active immunity which enabled the deer to resist challenge. The results of this study suggest that wild deer become infected with P. andersoni by isolated chance encounters with infected gastropods.     

Serological diagnosis of Parelaphostrongylus tenuis infection in white-tailed deer and identification of a potentially unique parasite antigen

Serological diagnosis of Parelaphostrongylus tenuis infection should offer many advantages over the currently used method of fecal analysis that relies on a patent infection. Toward this end, we investigated the presence of P. tenuis-specific antibodies in experimentally infected white-tailed deer (WTD) and of unique P. tenuis antigens that may be exploited for serodiagnosis. WTD infected with 6, 20 or 100-150 P. tenuis third-stage larvae (L3) had anti-parasite antibodies from as early as 21 days postinoculation (dpi) until the end of the experiment (147 dpi). Peak anti-P. tenuis enzyme-linked immunosorbent assay (ELISA) titers in individual animals ranged from 1:70 to 1:5,700. Serum from infected WTD reacted with 5 distinct P. tenuis L3 antigens (105, 45, 37, 32, and 19 kDa) as detected by the immunoblotting technique. Serum from caribou infected with Parelaphostrongylus andersoni or Elaphostrongylus rangiferi reacted with all antigens except the 37-kDa antigen of L3, indicating that it may be unique to P. tenuis and can serve as a serodiagnostic antigen. The 37-kDa antigen appears to be present in the adult P. tenuis but not adult E. rangiferi or E. cervi. The development of an ELISA utilizing the unique antigen of P. tenuis should lead to a reliable diagnostic assay for P. tenuis infection in WTD.     

A search for Parelaphostrongylus andersoni in white-tailed deer from Maine.

Longissimus dorsi muscles from 42 white-tailed deer (Odocoileus virginianus) from Maine (USA) were examined for the Parelaphostrongylus andersoni. No adult nematodes were found. Prevalence based on the Poisson approximation of a binomial distribution could have been between 0 and 9% (95% C.I.). However, based on prevalence documented elsewhere (10 to 18%), it is unlikely that P. andersoni occurs in white-tailed deer in central Maine.     

Meningeal worm is a long-lived parasitic nematode in white-tailed deer

A natural infection of the meningeal worm, Parelaphostrongylus tenuis, persisted for at least 3.7 yr in a white-tailed deer (Odocoileus virginianus). The deer was 5-7 yr old and was shedding dorsal-spined nematode larvae at the time of quarantine. Larvae were extracted from all fecal samples collected up to 730 days post-quarantine (dpq) and thereafter only at 862 dpq and at necropsy (1,350 dpq). Live adults of P. tenuis, one male and one female, were recovered from the cranium at necropsy. Parelaphostrongylus tenuis infections are long lived and latent periods may be extended. Our findings reaffirm the need for reliable antemortem diagnosis to identify non-patent P. tenuis infections to prevent inadvertent introduction of infected animals to non-endemic areas.     

Prevalence of Parelaphostrongylus tenuis in white-tailed deer in northern New York.

The prevalence and distribution of "brainworm" (Parelaphostrongylus tenuis) were examined in northern New York (USA) from 1986 to 1989. Sixty nine (46%) of 151 white-tailed deer (Odocoileus virginianus) heads examined, contained adult P. tenuis. The proportion of infected individuals was not significantly different between males and females. Prevalence was significantly greater in the adult age class as compared to the juvenile age class (P less than 0.01). Deer pellet samples were examined for prevalence of P. tenuis-like larvae. Pellet samples in New York had an overall prevalence of 60%. The effects of precipitation and host density on prevalence of P. tenuis in deer was not significant.     

Establishment of adult Parelaphostrongylus tenuis, patent infections, and acquired immunity after experimental infection of white-tailed deer (Odocoileus virginianus) and red deer (Cervus elaphus elaphus)

Experimental Parelaphostrongylus tenuis infections were established in white-tailed deer (Odocoileus virginianus) and an atypical host, red deer (Cervus elaphus elaphus). Groups of deer were fed 10, 25, or 100 third-stage larvae (L3) of P. tenuis and received a single equivalent challenge exposure at varying intervals. Infections were monitored up to 6 yr in white-tailed deer and up to 2.8 yr in red deer. The prepatent period in white-tailed deer varied from 91 to 1,072 days (381 +/- 374) and in red deer from 105 to 358 days (167 +/- 77). Adult worms lived for up to 6 yr in white-tailed deer. Although most had patent infections until necropsy, latent periods were observed regardless of season. Adult worms lived for up to 2.8 yr in red deer, and patent infections persisted for 20-363 days (152 +/- 106). Patent infections were correlated with the presence of adult worms in blood vessels and sinuses of both deer species. Worms were restricted to the subdural space in all deer with latent and occult infections. Adult worm recovery in white-tailed deer fed 10 or 25 L3 corresponded to the mean intensities reported in natural infections of white-tailed deer Recovery from deer fed 100 L3 was not typical of natural infection intensities. Adult P. tenuis established in all groups of red deer, but neurologic disease was restricted to animals fed 100 L3. Acute neurologic disease was associated with subdural hemorrhage and occurred at 11 mo postinfection in 2 red deer. The absence of postchallenge patent periods and the persistence of occult infections indicated that challenge exposures did not establish. These data indicate that acquired immunity to P. tenuis was established by 6 mo postinfection in both white-tailed and red deer. Latent periods in white-tailed deer and latent infections in red deer reinforce the need for a reliable diagnostic assay.     

Distribution and ecology of meningeal worm,Parelaphostrongylus tenuis (Nematoda), in northcentral North America

Meningeal worm (Parelaphostrongylus tenuis), a common nematode parasite in white-tailed deer (Odocoileus virginianus) and pathogenic for several species of ungulates in eastern North America, is not known to occur in the west. Heads of 1,902 white-tailed deer were examined for adult meningeal worm to determine geographic distribution of the parasite in Saskatchewan and Manitoba (Canada) and North Dakota (USA). Finding the parasite in a deer in eastern Saskatchewan near the Manitoba border established the current northern and western limits in Canada. Prevalence of infection was < 1, 18.6, and 8.2% in Saskatchewan, Manitoba, and North Dakota, respectively. Infected deer occurred throughout southern Manitoba and eastern North Dakota. Distribution appears to have changed little since the last published survey for P. tenuis in the region in 1972. We examined precipitation, temperature, deer density, and forest cover as likely correlates to prevalence and distribution of P. tenuis. Deer management units used for hunting purposes were the scale of analysis in the three jurisdictions. Presence of P. tenuis was positively correlated with precipitation during frost-free periods and deer density, and it was negatively correlated with winter and spring temperatures. Landscapes with > 25 and < 75% forest cover were most likely to have infected deer. Low rainfall and low density of white-tailed deer likely influence the westernmost limit of P. tenuis.     

Parasites, diseases, and health status of sympatric populations of fallow deer and white-tailed deer in Kentucky

In August 1983, a study on parasites, diseases, and health status was conducted on sympatric populations of fallow deer (Dama dama) and white-tailed deer (Odocoileus virginianus) from Land Between The Lakes, Lyon and Trigg counties, Kentucky. Five adult deer of each species were studied. White-tailed deer had antibodies to epizootic hemorrhagic disease (EHD) virus and Leptospira interogans serovariety icterohemorrhagiae, and fallow deer had antibodies to bluetongue and EHD viruses. Serologic tests for bovine virus diarrhea virus, infectious bovine rhinotracheitis virus, parainfluenza3 virus, and Brucella spp. were negative. One white-tailed deer had an infectious cutaneous fibroma, and one fallow deer had pulmonary mucormycosis. White-tailed deer harbored 16 species of parasites, all of which are considered typical of the parasite fauna of this host in the southeastern United States. Fallow deer harbored nine species of parasites, including eight species known to occur in white-tailed deer on the area and one species (Spiculopteragia assymmetrica) that is not. All fallow deer had inflammatory lesions in the spinal cord and/or brain that were attributed to prior infection with meningeal worm (Parelaphostrongylus tenuis), indicating that P. tenuis infections are not always fatal for this species. The apparent high rate of exposure of Land Between The Lakes fallow deer to P. tenuis without a resultant high rate of clinical cerebrospinal parelaphostrongylosis is hypothesized to be due to a low prevalence and intensity of P. tenuis, partial innate resistance of fallow deer, and acquired immunity.     

The potential for false-positive diagnosis of protostrongyliasis by extraction of larvae from feces

The potential of protostrongylid first-stage larvae (L1) to survive passage through the alimentary canal of non-infected mammals was investigated. Parelaphostrongylus tenuis L1 were collected from feces of an experimentally infected white-tailed deer (Odocoileus virginianus). We utilized two red deer (Cervus elaphus) and four laboratory rats (Rattus norvegicus) which were each fed the L1 of P. tenuis. Larvae were recovered, intact and alive, from the fecal samples of all six animals. Larvae of P. tenuis, and probably of other related species, can survive passage through the alimentary canal of uninfected mammals and they can be collected from feces using the Baermann technique and other related larval extraction methods. Rain water was found to be successful in the dispersal of P. tenuis L1 from the feces of infected animals. These findings raise the possibility of ingestion of L1 and their subsequent passage, by uninfected animals. This potential for false-positive diagnosis of infection in live animals necessitates accurate interpretation of a host's infection-status. Such findings reinforce the need for a reliable method of diagnosing infections in live animals.     

Distribution of meningeal worm (Parelaphostrongylus tenuis) in South Dakota

Heads of hunter-harvested deer (Odocoileus sp.) and elk (Cervus elaphus) were collected from meat processing plants throughout South Dakota (USA) from 1997 through 1999 to determine distribution of meningeal worm (Parelaphostrongylus tenuis) in eastern and western South Dakota. A total of 2,848 white-tailed deer (WTD) were examined for P. tenuis, of which 578 (20.3%) were infected with the parasite. Of 578 deer infected, 570 (98.6%) were harvested east of the Missouri River. Our results indicate that P. tenuis is widely distributed throughout eastern South Dakota and limited to the southcentral region of western South Dakota. Infected WTD were documented in 37 of 44 counties in eastern South Dakota and three of 22 counties in western South Dakota. No meningeal worms were found on the meninges or cranial surfaces of 215 mule deer ( Odocoileus hemionus) or 344 elk examined. These findings further define the distribution of the parasite throughout the state. We suggest that the Missouri River acts, in part, as a physical barrier to the westward expansion of P. tenuis to the grasslands of western South Dakota.     

Parelaphostrongyliasis in white-tailed deer in Missouri

The heads of 137 white-tailed deer (Odocoileus virginianus) were collected on the opening day of the 1996 Missouri (USA) fire-arms deer season and surveyed for the presence of meningeal worm (Parelaphostrongylus tenuis). Eighteen percent of the deer examined were infected. Mean intensity of infection was 2.0 (range 1-7). There were no significant differences of infection or mean intensity when deer were classified and compared according to sex or age class.     

Efficacy of ivermectin against Parelaphostrongylus andersoni (Nematoda, Metastrongyloidea) in white-tailed deer (Odocoileus virginianus)

Ivermectin was injected subcutaneously at 200 and 400 micrograms/kg of body weight into seven white-tailed deer (Odocoileus virginianus) in an attempt to control the muscle nematode Parelaphostrongylus andersoni. Counts of first-stage larvae in feces dropped to zero at 17 to 18 days posttreatment. Larvae reappeared in feces 1.5 to 6 wk later in six deer. Four deer were treated again approximately 9 wk after the first treatment; larval counts dropped to zero in 12 to 18 days. Larvae reappeared in low numbers 45 to 55 days after the second treatment. Because deer were held indoors on cement and the prepatent period of these worms is approximately 2 mo, the reappearance of larvae was not due to reinfection by accidental ingestion of gastropod intermediate hosts. Results suggest that ivermectin at dosages of 200 or 400 micrograms/kg of body weight suppressed larval production by adult female nematodes for several weeks or destroyed first-stage larvae in the lungs.