Bionomics of larvae of Parelaphostrongylus odocoilei (Nematoda: Protostrongylidae) in experimentally infected gastropod intermediate hosts

Parelaphostrongylus odocoilei is a protostrongylid parasite that has recently been recognized at several locations in sub-Arctic, but not Arctic, North America. We investigated factors that may determine the distribution of P. odocoilei, including suitable gastropod intermediate hosts, temperature requirements for larval development in gastropods, and larval emergence facilitating overwinter transmission. We collected and experimentally infected gastropods from a site in the sub-Arctic where P. odocoilei is at the northern limit of its distribution. Deroceras laeve, Catinella sp., and Euconulus cf fulvus, but not members of the Pupillidae, were suitable intermediate hosts. We describe bionomics of larvae of P. odocoilei in D. laeve and Catinella sp. Infective larvae emerged from all slugs (D. laeve) and 60% of Catinella sp. snails, and emergence from D. laeve was intensity dependent. Emerged infective larvae survived up to 6 mo under conditions approximating that of the subnivean environment. In D. laeve, there was a direct relationship between temperature and development rate of larvae of P. odocoilei. Larvae of P. odocoilei did not develop to infective stage below the theoretical threshold (8.5 C), and required a minimum of 163 degree days to complete development. These developmental parameters can be incorporated into a model to predict larval development in the field. Knowledge of the factors influencing larval bionomics provides the foundation for predicting temporal and spatial patterns of parasite distribution, abundance, and transmission.     

Parelaphostrongylus odocoilei (Nematoda: Protostrongylidae) and a protostrongylid nematode in woodland caribou (Rangifer tarandus caribou) of Alberta, Canada

Two size-groups of dorsal-spined, first-stage, nematode larvae were found in feces of woodland caribou, Rangifer tarandus caribou (Gmelin), in Alberta from 1976-1982. Larvae from caribou feces in northeastern Alberta were 451 +/- 17 micrograms in length, while those from west-central Alberta were 362 +/- 18 micrograms in length. Larvae collected from west-central Alberta developed to the infective stage, experimentally, in the terrestrial gastropod Triodopsis multilineata (Say) and were infective to captive mule deer fawns, Odocoileus H. hemionus (Rafinesque). Adult nematodes, identified as Parelaphostrongylus odocoilei (Hobmaier and Hobmaier, 1934), were recovered from the skeletal muscles of the mule deer.     

Parelaphostrongylus andersoni (Nematoda: Protostrongylidae) in white-tailed deer from Michigan

Dorsal-spined larvae in fecal samples from free-ranging white-tailed deer (Odocoileus virginianus) in Michigan and Pennsylvania were used as a source of larvae to infect a hand-raised white-tailed deer fawn. The fawn receive 200 third-stage larvae and passed dorsal-spined larvae in feces 66 days later. Muscleworm (Parelaphostrongylus andersoni), and meningeal worm (Parelaphostrongylus tenuis) were recovered at necropsy. Two white-tailed deer and seven wapiti (Cervus elaphus) exposed to larvae of the source from Pennsylvania harbored only P. tenuis. This is the first report of P. andersoni in the midwestern United States and extends the known range of this muscleworm in free-ranging white-tailed deer. Concurrent infections of P. andersoni and P. tenuis have not been established previously in experimentally infected fawns.     

Caudal polymorphism and cephalic morphology among first-stage larvae of Parelaphostrongylus odocoilei (Protostrongylidae: Elaphostrongylinae) in Dall's sheep from the Mackenzie Mountains, Canada

We demonstrate polymorphism in the structure of the tail among first-stage larvae of Parelaphostrongylus odocoilei (Protostrongylidae). Two distinct larvae, both with a characteristic dorsal spine, include (1) a morphotype with a kinked conical tail marked by 3 distinct transverse folds or joints and a symmetrical terminal tail spike and (2) a morphotype with a digitate terminal region lacking folds or joints and with an asymmetrical, subterminal tail spike. These divergent larval forms had been postulated as perhaps representing distinct species of elaphostrongyline nematodes. Application of a multilocus approach using ITS-2 sequences from the nuclear genome and COX-II sequences from the mitochondrial genome confirmed the identity of these larvae as P. odocoilei. Additionally, based on scanning electron microscopy (low-temperature field emission), the cephalic region of these larvae consisted of a cuticular triradiate stoma surrounded by 6 single circumoral papillae of the inner circle, 10 papillae of the outer circle (4 paired and 2 single), and 2 lateral amphids. Our's is the first demonstration of structural polymorphism among larval conspecifics in the Metastrongyloidea and Strongylida. The basis for this polymorphism remains undetermined, but such phenomena, if discovered to be more widespread, may contribute to continued confusion in discriminating among first-stage larvae for species, genera, and subfamilies within Protostrongylidae.     

A re-evaluation of the phylogeny of Parelaphostrongylus Boev & Schulz, 1950 (Nematoda: Protostrongylidae)

The phylogeny of the genus Parelaphostrongylus was reconstructed using Elaphostrongylus rangiferi as an outgroup. Parelaphostrongylus is monophyletic and divided into two clades, one containing the meningeal worm, P. tenuis of white-tailed deer, and the other consisting of two muscle-inhabiting forms, P. andersoni and P. odocoilei of white-tailed and mule deer, respectively. Differences in biological features, including tissue migration route and prepatent period, are mapped onto the cladogram and discussed. Phylogenetic relationships among the host group, the Cervidae, are reviewed. It is suggested that E. rangiferi evolved in a Palaearctic cervid. Parelaphostrongylus probably co-speciated with Nearctic deer, Odocoileus spp. Host-switching from O. virginianus may explain the widespread occurrence of P. andersoni in Rangifer in North America.     

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.     

Development and pathogenesis of Parelaphostrongylus odocoilei (nematoda: protostrongylidae) in experimentally infected thinhorn sheep (Ovis dalli )

Recently, the protostrongylid nematode Parelaphostrongylus odocoilei has been reported in a new host species, thinhorn sheep (Ovis dalli). For the first time, we completed the life cycle of P. odocoilei in three Stone's sheep (O. dalli stonei) and two thinhorn hybrids (O. dalli stonei x O. dalli dalli), each infected with 200 third-stage larvae from slugs (Deroceras laeve). The prepatent period ranged from 68 days to 74 days, and shedding of first-stage larvae (L1) peaked at >10,000 L1 per gram of feces between 90 and 110 days postinfection. A total of 75, 27, and 14 adult P. odocoilei were recovered from skeletal muscles of three Stone's sheep. Starting in the prepatent period, all infected sheep lost weight and developed peripheral eosinophilia. At 2 wk before patency, two thinhorn hybrids developed neurologic signs (hind end ataxia, loss of conscious proprioception, and hyperesthesia) that resolved at patency. Eosinophilic pleocytosis and antibody to Parelaphostrongylus spp. were detected in the cerebrospinal fluid of the affected sheep, suggesting that the migration route of the "muscleworm" P. odocoilei may involve the central nervous system. Twenty days after treatment with ivermectin, neurologic signs recurred and larval shedding ceased in one infected thinhorn hybrid, whereas multiple treatments transiently suppressed but did not eliminate larval shedding in the other. During patency, two Stone's sheep with numerous eggs and larvae of P. odocoilei in the lungs died of respiratory failure following anesthesia or exertion. Parelaphostrongylus odocoilei has widespread geographic distribution, high prevalence, the possibility of causing neurologic and respiratory disease, resistance to treatment, and may constitute a significant emerging disease risk for thinhorn sheep.     

Apodemus sylvaticus, a new host for Acanthocheilonema viteae (Nematoda: filarioidea)

Susceptibility of Apodemus sylvaticus and A. agrarius to infection with Acanthocheilonema viteae was compared with that of hamsters and jirds. Microfilaremia in A. sylvaticus was first noted on day 52 post-infection (p.i.) and lasted during the course of the study (up to day 150 p.i.). Maximum microfilaremic levels (female worm basis) of A. sylvaticus [mean +/- S.D. (n) = 690 +/- 1288(6)] were considerably higher than those of hamsters [16 +/- 18(6)] and jirds [51 +/- 25(5)]. Adult worm recovery in A. sylvaticus ranged from 2 to 40% of the number of infective larvae inoculated. Worm development in A. sylvaticus resembled that in hamsters and jirds. In contrast, microfilaremia was not detected in, nor adult worms recovered from A. agrarius throughout the study.     

Experimental infections of free-ranging Rocky Mountain bighorn sheep with lungworms (Protostrongylus spp.; Nematoda: Protostrongylidae)

Twelve free-ranging Rocky Mountain bighorn lambs (Ovis canadensis canadensis), each exposed experimentally to 125-1,000 infective third-stage larvae of Protostrongylus stilesi and P. rushi, shed significantly more first-stage larvae in their feces than did control lambs, but showed no clinical signs of illness and had equivalent summer and overwinter survival as control lambs. Two adult ewes, each exposed to 925 infective larvae, showed no increase in numbers of first-stage larvae in their feces; both survived at least 14 mo postexposure. Experimentally exposed lambs did not differ from control lambs in numbers of larvae in their feces in the following summer. Three experimental lambs had 313-402 adult P. stilesi and 0-97 adult P. rushi on necropsy; two control lambs had 255 and 270 P. stilesi and no P. rushi. The presence of these numbers of lungworms did not appear to be sufficient to precipitate lungworm pneumonia in bighorn lambs under the conditions of this study.     

A second record of adult Ascarops strongylina (Rudolphi, 1819) (Nematoda: Spirocercidae) in a rodent host

Mature adults of Ascarops strongylina (Nematoda: Spirocercidae) were collected from a Manchurian zokor, Myospalax psilurus (Rodentia: Cricetidae), in Mongolia. This is the second record of adult A. strongylina from wild rodents and the first for M. psilurus as a definitive host of this nematode. Remnants of ground crustaceans (Porcellio sp.) and a dung beetle (Onthophagus sp.) were also found in the stomach of the zokor.     

Helicotylenchus vulgaris Yuen, 1964 (Nematoda: Hoplolaimidae): A new record for New Zealand

Abstract

Helicotylenchus vulgaris Yuen, 1964 was extracted in large numbers from soil around grass roots in an ap ple orchard at Kurow, North Otago. This is the first time the species is recorded in New Zealand. The material is described and illustrated.     

Muellerius capillaris (Mueller, 1889) (Nematoda: Protostrongylidae): an unusual finding in Rocky Mountain bighorn sheep (Ovis canadensis canadensis Shaw) in South Dakota

Lungs and fecal samples from nine hunter-killed Rocky Mountain bighorn sheep were examined for lungworms. All samples contained adults and/or larvae of Muellerius capillaris (Mueller, 1889). Protostrongylus spp., the lungworms commonly reported from bighorn sheep, were not present in any samples. Larvae of M. capillaris bear a spine on the dorsal side of the posterior end and are shorter than dorsal-spined larvae of other lungworms recorded from North American ungulates. Larvae similar in shape but longer than those of Muellerius were found in free-ranging bighorn sheep in Alberta and British Columbia. In addition, dorsal-spined larvae have been found in bighorn sheep in Montana, North Dakota, and Washington. The identity of the dorsal-spined larvae is known only from sheep in South Dakota. Thus, caution must be taken when diagnosing lungworm infections in Rocky Mountain bighorn sheep.     

Purification of first-stage larvae of Elaphostrongylus cervi (Nematoda: Protostrongylidae) from feces

Parasites are often found in a milieu that requires extensive preparation and labor-intensive cleaning before they are suitable for use in analytical procedures. Application of modern techniques in immunology and molecular biology demands pure yields of parasites. To purify first-stage (L1) larvae of Elaphostrongylus cervi, fecal suspensions from an infected red deer were processed by the Baermann method and embedded in a gel matrix with the objective of selectively trapping fecal debris. About half the number (50.9%) of embedded larvae migrated out of the gel within a 24-hr period and were collected as clean parasite suspensions, virtually free from fecal debris. The numbers of L1 emigrating from gels were inversely proportional to the fecal debris content and the thickness of the gel. Removal of fecal debris from Baermann fluid by sieving prior to gel embedment enhanced the yield of pure L1.     

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.