Patricia A Pilitt’s research while affiliated with United States Department of Agriculture and other places

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Publications (41)


Figure 1.   Maned wolf ( Chrysocyon brachyurus ), lung. A , wolf 1. Cut surface of a well-defined granuloma (arrow) with an intralesional adult Spirocerca lupi . B , wolf 2. Cross-sections of 3 adult S. lupi . Note prominent lateral chords (lc), coelomyarian musculature, pseudocoelom containing eosinophilic homogeneous material (ef ), large intestine with high columnar epithelium (i), and uterus filled with numerous ovoid eggs (e). Hematoxylin and eosin. Bar = 500 μm. 
Spirocerca lupi granulomatous pneumonia in two free-ranging maned wolves (Chrysocyon brachyurus) from central Brazil
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October 2014

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358 Reads

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9 Citations

Journal of veterinary diagnostic investigation: official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc

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Chris H Gardiner

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The current report describes granulomatous pneumonia due to Spirocerca lupi in 2 free-ranging maned wolves (Chrysocyon brachyurus). Both wolves had multiple, white, 1-1.5 cm in diameter, soft, encapsulated granulomas in the caudal lung lobes, which contained centrally placed parasites on cut sections. Microscopically, there was granulomatous inflammation with numerous intralesional sections of spirurid nematodes. Representative complete adult specimens of nematodes derived from these lesions were submitted for parasitological exam and identified as the spirurid S. lupi. To the authors' knowledge, there have been no published reports of S. lupi in maned wolves.

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Discovery and Description of a New Trichostrongyloid Species (Nematoda: Ostertagiinae), Abomasal Parasites in Mountain Goat, Oreamnos americanus, from the Western Cordillera of North America

February 2012

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124 Reads

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30 Citations

Journal of Parasitology

Marshallagia lichtenfelsi sp. n. is a dimorphic ostertagiine nematode occurring in the abomasum of mountain goats, Oreamnos americanus, from the Western Cordillera of North America. Major and minor morphotype males and females are characterized and distinguished relative to the morphologically similar Marshallagia marshalli / Marshallagia occidentalis from North America and Marshallagia dentispicularis, along with other congeners, from the Palearctic region. The configuration of the convoluted and irregular synlophe in the cervical region of males and females of M. lichtenfelsi is apparently unique, contrasting with a continuous and parallel system of ridges among those species of Marshallagia, including M. marshalli/M. occidentalis, which have been evaluated. Specimens of M. lichtenfelsi are further defined by the rectangular form of the accessory bursal membrane (width > length) in the major morphotype and by the trapezoidal Sjöberg's organ in the minor morphotype, in addition to specific attributes of the spicules and spicule tips. We regard 12 species, including the proposed new taxon, to be valid. Primary diagnostic characters are reviewed for Marshallagia and a framework is presented for standardization of future descriptions incorporating the synlophe in males and females and the structure of the spicules and genital cone in major and minor morphotype males. The center of diversity for species of Marshallagia is the mountain-steppe region of central Eurasia where 11 species (including the Holarctic M. marshalli) are recognized in association with Caprini, Rupicaprini, and Antelopinae; only 2 species occur in the Nearctic. In this assemblage, M. lichtenfelsi is endemic to North America and limited in host distribution to mountain goats. An intricate history for refugial isolation and population fragmentation demonstrated for mountain goats and wild sheep indicates the potential for considerable cryptic diversity for Marshallagia and other nematodes. Shifting patterns of contact and sympatry among assemblages of ungulates during the Pleistocene are consistent with geographic and host colonization as a process involved in diversification of these parasites.


Discovery and Description of the “Davtiani” Morphotype for Teladorsagia boreoarcticus (Trichostrongyloidea: Ostertagiinae) Abomasal Parasites In Muskoxen, Ovibos moschatus, and Caribou, Rangifer tarandus, from the North American Arctic: Implications for Parasite Faunal Diversity

September 2011

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60 Reads

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8 Citations

Journal of Parasitology

Collections to explore helminth diversity among free-ranging ungulates in the North American Arctic revealed the occurrence of a third male, or " davtiani ," morphotype for Teladorsagia boreoarcticus . Designated as T. boreoarcticus forma (f.) minor B, the males occurred with T. boreoarcticus f. major and T. borearcticus f. minor A in endemic populations of muskoxen (Ovibos moschatus wardi) and barrenground caribou (Rangifer tarandus groenlandicus) on Victoria Island, Nunavut, Canada, and in muskoxen and Peary caribou ( Rangifer tarandus pearyi ) on Banks Island, Northwest Territories, Canada. These specimens differ from conspecific morphotypes in the structure of the genital cone and Sjöberg's organ. Relative to T. boreoarcticus f. minor A, specimens of T. boreoarcticus f. minor B are consistently smaller, and mean dimensions for the bursa and spicules do not overlap. The robust spicules are similar in form, particularly in the relative length of the dorsal and ventral processes, but mean total length is substantially less in specimens of T. boreoarcticus f. minor B. Differences that distinguish the minor morphotypes of T. boreoarcticus parallel those demonstrated for the T. trifurcata and T. davtiani morphotypes in association with T. circumcincta sensu stricto. New host and geographic records include the 3 morphotypes of T. boreoarcticus in muskoxen and Peary caribou from Banks Island and in barrenground caribou from Victoria Island. Recognition of the ubiquitous nature of cryptic species emphasizes the need to effectively develop and use our collections-based resources and museum archives to build a robust understanding of the biosphere. Field inventory should include provisions for integrative approaches that preserve specimens suitable for comparative morphology, multi-faceted molecular investigations, and population genetics.


Synlophe Structure in Pseudomarshallagia elongata (Nematoda: Trichostrongyloidea), Abomasal Parasites Among Ethiopian Ungulates, with Consideration of Other Morphological Attributes and Differentiation Within the Ostertagiinae

April 2010

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340 Reads

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5 Citations

Journal of Parasitology

The independence of Pseudomarshallagia and its placement among the medium stomach worms of ungulates, Ostertagiinae, is confirmed based on comparative morphological studies of the synlophe and genital attributes among male and female specimens. An emended description of Pseudomarshallagia elongata is presented based on a series of specimens in sheep from northern Ethiopia. Pseudomarshallagia elongata is retained among the 15 genera of the Ostertagiinae based on presence of a prominent esophageal-intestinal valve, paired ‘‘0’’ papillae, a modified accessory bursal membrane containing the paired ‘‘7’’ papillae, and configuration of the copulatory bursa. The structure of the synlophe in males and females is also typical and within the range of variation demonstrated for Type II and Type A cervical patterns among other ostertagiines. We emphasize the importance of continued survey and inventory of parasite faunas to establish the limits of diversity on local, regional, and global scales. Consequently we strongly encourage routine deposition of voucher specimens from all survey activities designed to explore faunal diversity. Although this is particularly important in regions that remain poorly known, such as Africa, the principle certainly applies more broadly.


Synlophe Structure for Species of Longistrongylus (Nematoda: Trichostrongyloidea), Abomasal Parasites among Ungulates from Sub-Saharan Africa, with Comparisons to the Global Ostertagiine Fauna

December 2009

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13 Reads

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4 Citations

Journal of Parasitology

The synlophe, or system of longitudinal cuticular ridges characteristic of some trichostrongyloid nematodes, is examined in detail for 6 of 8 species in Longistrongylus (Ostertagiinae) that occur in ungulates across sub-Saharan Africa. Among the species of Longistrongylus examined, 5 are characterized by a tapering pattern laterally in the cervical zone (anterior to the esophageal-intestinal junction), which is largely consistent among multiple male and female specimens; in contrast, for Longistrongylus meyeri the lateral pattern is parallel. The synlophe is bilaterally symmetrical, with ridges extending from the base of the cephalic expansion to near the caudal extremity in males and females. Ridges are acutely pointed, with perpendicular orientation and absence of gradient as viewed in transverse section. Species-specific patterns in conjunction with the numbers of ridges may serve to augment an array of diagnostic characters for species of Longistrongylus and contribute to increasingly accurate identification of female specimens. Among 5 of 6 species examined in the current study, the numbers of ridges in males was equal to or exceeded that observed in females, a pattern seen only in Africanastrongylus among the 15 genera of the Ostertagiinae. The differential numbers of ridges in males and females may represent another character among the suite of attributes that in part diagnose the genus Longistrongylus.


A New Species of Trichostrongyloid in African Buffalo ( Syncerus caffer ) (Artiodactyla: Bovinae) from Uganda

October 2009

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17 Reads

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2 Citations

Journal of Parasitology

Africanastrongylus giganticus n. sp. is described based on large ostertagiine nematodes occurring in the abomasum of African buffalo, Syncerus caffer, from Uganda; this represents the second species recognized in the genus. Specimens of A. giganticus are characterized by large size (15-19 mm in total length), a strongly tapering synlophe in the cervical region, and a great number of ridges at all levels of the body (maximum 72 attained in the third quarter); numbers of ridges exceed that reported among any known genera and species of the Ostertagiinae. We refer A. giganticus to this genus based on a strongly tapering lateral synlophe, relatively large numbers of ridges at all levels of the body, miniscule cervical papillae, poorly demarcated divisions of the ovejector, absence of vulval cuticular inflations, and the presence of slightly protruding lips at the vulva. It is distinguished from its congener, Africanastrongylus buceros, in total length, maximum number of ridges (68-72 vs. 53, respectively), structure and disposition of the synlophe, presence of strongly spiraled ovarian tracks, and eggs that are distributed in 3 or more rows in the uterus. A superficial resemblance to Longistrongylus meyeri, the only other large ostertagiine in the African fauna, is evident; these species, however, are distinct based on the synlophe and other characters. Recognition of a second species of Africanastrongylus represented by nematodes of large size suggests that prior reports of L. meyeri in Syncerus caffer may be attributable to A. giganticus.


Further characterization of a cattle nematode population with demonstrated resistance to current anthelmintics

August 2009

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34 Reads

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80 Citations

Veterinary Parasitology

We previously documented the appearance of cattle nematode parasites resistant to avermectins, milbemycin, and a benzimidazole at the end of a grazing season in a backgrounding operation in the upper Midwestern US. To further characterize the pattern of drug resistance, we extended the study to (1) monitor the animals over the course of the grazing season; (2) increase the number of animals slaughtered at the end of the season to minimize the effect of potential outlying observations; (3) increase the time interval between treatment and slaughter to ensure sufficient time for drug action; (4) utilize repeated fecal sampling in the fecal egg reduction test to minimize procedural variation; (5) increase the number of drugs tested. The results of the present study were in agreement with those of the previous study and demonstrated that during the course of the grazing season the pastures harbored significant numbers of parasites that were refractory to avermectins, milbemycin, and a benzimidazole at the label recommended doses. As seen previously, Haemonchus contortus resistant to all these anthelmintics were present over the course of the study period. In contrast, Cooperia sp., mainly punctata, and Haemonchus placei were resistant only to the macrocyclic lactones. There was no apparent resistance against the older anthelmintic levamisole, which had not been used for >20 years in the operation. However, animals treated with this drug continued to harbor small but measurable numbers of Ostertagia ostertagi.


The Identification of Cattle Nematode Parasites Resistant to Multiple Classes of Anthelmintics in a Commercial Cattle Population in the US

August 2009

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126 Reads

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171 Citations

Veterinary Parasitology

Resistance to modern anthelmintics by ruminant nematode parasites is an increasing problem throughout the world. To date the problem has largely been reported in parasites of small ruminants, but there are increasing reports of such resistance in nematodes recovered from cattle. Until now there have been no published reports of drug resistant parasites from cattle in North America. In 2002 a producer in the upper Midwest who backgrounds young cattle acquired from the southeastern US experienced lower than expected weight gain as well as apparent parasitic gastroenteritis in his cattle during the fall. Fecal sample results supported the suspicion that decreased productivity and diarrhea were the result of GI nematode parasitism. The operation used intensive grazing management and practiced strategically timed deworming for >17 year. In 2003, all animals were dewormed the first week of May with Ivomec Plus, then with Dectomax Injectable on 4 June and 17 July. On 31 July, 10 randomly taken fecal samples showed EPG values from 0 to 55. To assess whether the apparent decreased drug efficacy was the result of drug resistance in the nematode population, on 18 August approximately 150 heads, previously strategic timed dewormed, of 9-11 month old cattle from one pasture were selected for study. The calves were randomly assigned to 1 of 6 treatment groups: untreated (U), ivermectin injectable (I), moxidectin pour-on (M), doramectin injectable (D), eprinomectin pour-on (E), albendazole oral (A). Cattle were weighed prior to treatment and the drug was dosed according to label directions. Seven days later, 3 calves from each group were slaughtered for worm recovery. Fecal samples taken from the remaining animals at 14 days after treatment showed that the reduction of mean fecal EPG value for each group was: U-46%, I-52%, M-72%, D-61%, E-8%, and A-68%. Worm recovery from the slaughter calves showed that all groups harbored significant numbers of Haemonchus placei and H. contortus. In addition, all avermectin-treated groups contained significant numbers of Cooperia punctata, and smaller numbers of C. oncophora and C. spatulata. These results imply that the pastures studied contain substantial numbers of H. contortus resistant to both avermectins and benzimidazoles, and H. placei and Cooperia sp. resistant to all the commonly used avermectin anthelmintics. This is the first report of anthelmintic resistance in American cattle parasites.


FIGURES 1–6. Labiostomum (Eugenuris) talkeetnaeuris and L. (Labiostomum) rauschi showing structure of the cephalic region (1–3) and vulva in female specimens (4–6); same scale bars for all figures. (1) Cephalic extremity, lateral view of allotype for L. (L.) coloradensis, USNPC 39443 in O. princeps showing tapering head without inflated capsule. (2) Cephalic extremity, dorsal view of voucher specimen of L. (E.) talkeetnaeuris, USNPC 101105 in O. princeps, showing tapering head with prominent cervical alae and without capsule. (3) Cephalic extremity of voucher specimen of L. (L.) rauschi, USNPC 101092 in O. princeps, showing well-developed capsule. (4) Vulva, lateral view in allotype for L. (L.) coloradensis, USNPC 39443, noting prominent beak-like structure. (5) Vulva, lateral view in syntype female of L. (E.) utahensis, USNPC 73259 in O. princeps, showing beak-like form and variation in size. (6) Vulva, lateral view in voucher specimen of L. (L.) rauschi, USNPC 101092, showing structure of small ventral flap.  
FIGURES 7–10. Labiostomum (Eugenuris) talkeetnaeuris and L. (Labiostomum) rauschi showing variation in structure of the vulva; same scale bars for all figures. (7) Vulva, lateral view in syntype female of L. (E.) utahensis, USNPC 73259 in O. princeps. (8) Vulva in lateral view of voucher of L. (E.) talkeetnaeuris, USNPC 101105 in O. princeps. (9) Vulva in lateral view of voucher of L. (E.) talkeetnaeuris, USNPC 101103 in O. collaris. (10) Vulva in latero-ventral view of voucher of L. (L.) rauschi, USNPC 101093 in O. collaris, noting prominent ventral flap.  
FIGURES 18–22. Labiostomum (Eugenuris) talkeetnaeuris and L. (Labiostomum) rauschi showing structure and distribution of caudal papillae in male specimens; drawn at same scale. Shown is ventral view at level of cloaca, bordered by body wall and lateral caudal alae. (18) Voucher specimen of L. (E.) talkeetnaeuris, USNPC 101103 in O. collaris showing 2 preanal pairs, 1 adanal pair with inflated bases, 3 postanal pairs, and massive double papillae forming ventral cushion on median line. (19) Holotype male for L. (L.) coloradensis, USNPC 39443 in O. princeps. (20) Syntype male of L. (E.) utahensis, USNPC 73259 in O. princeps. (21) Voucher specimen of L. (L.) rauschi, USNPC 101093 in O. collaris, showing 2 preanal pairs and 3 postanal pairs, and massive double papillae on midline forming ventral cushion posterior to cloaca. (22) Voucher specimen of L. (L.) rauschi, USNPC 101095 in O. princeps.  
FIGURES 11-13. Labiostomum (Eugenuris) talkeetnaeuris and L. (Labiostomum) rauschi showing structure of tail in female, in lateral view. (11) Allotype for L. (L.) coloradensis, USNPC 39443 in O. princeps showing elongate filiform tail. (12) Syntype female of L. (E.) utahensis, USNPC 73259 in O. princeps. (13) Voucher of L. (L.) rauschi, USNPC 101092 in O. princeps showing inflated tail.
FIGURES 14-17. Labiostomum (Eugenuris) talkeetnaeuris showing structure of male tail and distribution of caudal papillae. (14) Caudal extremity in syntype male of L. (E.) utahensis, USNPC 73259 in O. princeps. (15) Caudal papillae, ventral view, in syntype male of L. (E.) utahensis USNPC 73259 showing distribution of 6 paired papillae (1-6) and massive double papillae (dbl) on posterior margin of cloaca. (16) Caudal extremity of voucher specimen of L. (E.) talkeetnaeuris USNPC 101105 in O. princeps. (17) Caudal papillae, ventral view, in voucher specimen of L. (E.) talkeetnaeuris USNPC 101103 in O. collaris.
Why Museums Matter: A Tale of Pinworms (Oxyuroidea: Heteroxynematidae) Among Pikas (Ochotona princeps and O. collaris) in the American West

May 2009

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274 Reads

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65 Citations

Journal of Parasitology

Permanent and well-supported museum or natural history collections provide a solid foundation for the process of systematics research through creation of an empirical record which validates our understanding of the biosphere. We explore the role of museums in ongoing studies of the complex helminth fauna characteristic of pikas (Ochotona spp.) in the American west. These studies address the taxonomy for pinworms of the Labiostomatinae and the problems associated with the absence of adequate type series and vouchers and with misidentifications in original descriptions. We demonstrate that the types for Labiostomum (Labiostomum) coloradensis are identical to some specimens in the syntype series representing L. (Eugenuris) utahensis, although the published descriptions are in disagreement. Both are identical to L. (Eugenuris) talkeetnaeuris and, as a consequence, are reduced as junior synonyms. Only 2 species of large pinworms, namely L. (Labiostomum) rauschi and L. (Eugenuris) talkeetnaeuris, are widely distributed in Ochotona collaris and O. princeps. Although this serves to clarify the taxonomy for species in these genera, prior records remain confused, as representative voucher specimens from all major surveys in North America were never submitted to museum collections. We strongly suggest that type and voucher series should not be held in private or personal collections, where such are eventually lost, discarded, or destroyed through neglect due to inattention and the absence of curation. The potential to accumulate meaningful baselines for assessment of environmental change is jeopardized if materials from survey and inventory are not routinely submitted to museum collections. The capacity of museum repositories, as a focus for systematics, ecology, and evolutionary studies and for the development of resources for biodiversity informatics, continues to be undervalued and poorly utilized by a cadre of scientists who are dependant on accurate and definitive information that transcends specific disciplines.


Robustostrongylus aferensis gen. nov. et sp. nov. (Nematoda: Trichostrongyloidea) in Kob (Kobus kob) and Hartebeest (Alcelaphus buselaphus jacksoni) (Artiodactyla) from Sub-saharan Africa, with Further Ruminations on the Ostertagiinae

March 2009

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58 Reads

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7 Citations

Journal of Parasitology

Abomasal nematodes (Ostertagiinae: Trichostrongyloidea), representing a previously unrecognized genus and species, were discovered in kob (Kobus kob) and kongoni (hartebeest) (Alcelaphus buselaphus jacksoni) from Uganda during surveys of ungulate parasites in the 1960s. Robustostrongylus aferensis gen. nov. et sp. nov. is characterized by a ventriculus-like, bilobed valve at the junction of the esophagus and intestine, a synlophe with unusually robust ridges, cervical papillae and excretory pore situated posterior to the mid-length of the esophagus, a unique body form and large diameter in males and females, a relatively anterior position for the vulva, and strongly convoluted and spiraled ovarian tracks in females. Bursal structure is 2-1-2, with subequal Rays 2/3, strongly reduced and robust Rays 8, and relatively narrow Rays 9/10 contained within a reduced, laterally inflated dorsal lobe. Spicules are filamentous and tripartite; the gubernaculum is cryptic, alate, and heart-shaped in the anterior. Robustostrongylus aferensis, with narrow filamentous spicules that trifurcate distally near 80%, paired arcuate "0" papillae that terminate in bulbous expansions, and a reduced dorsal lobe and ray most closely resembles species of Longistrongylus. A suite of unique characters, consistent in males and females, however, unequivocally distinguishes specimens of R. aferensis from all ostertagiines with either a 2-1-2 or 2-2-1 bursal pattern. Among 15 genera of the Ostertagiinae in the global fauna, 5 are entirely limited in distribution to Africa, including Africanastrongylus, Hamulonema, Longistrongylus, Pseudomarshallagia, and Robustostrongylus gen. nov.; species among 5 additional genera, including Cervicaprastrongylus, Hyostrongylus, Marshallagia, Ostertagia, and Teladorsagia, also occur in Africa, but they are represented as mosaics, with diversity centered in Eurasia or the Holarctic.


Citations (37)


... Varying degrees of morphological variations within and between different species of Haemonchus were reported in the past, which made accurate species identification challenging as well as time consuming [22]. In case of adults of subfamily Haemonchinae, the most reliable differences are in the patterns of longitudinal cuticular ridges of the synlophe and in chromosomal morphology [22,27]. The observations pertaining to third stage larvae of H. contortus in the present study were in concordance to the findings of van Wyk and coauthors [28]. ...

Reference:

First Record of Molecular Confirmation, Phylogeny and Haplotype Diversity of Haemonchus contortus from Gaddi (breed) Goats of North India
Synlophe Patterns of the Haemonchinae of Ruminants (Nematoda: Trichostrongyloidea)
  • Citing Article
  • October 2000

Journal of Parasitology

... According to this key, it was observed that the nematodes isolated in the current study possessed most of the criteria characteristics for H. longistipes such as long females with a body length about 20 mm, the number of ridges composing synlophe at the level of oesophagealintestinal junction 36 or more, cuticular ridges in males and females terminated in the anterior half of the body, posterior termination of sublateral and subventral ridges at or near the posterior end of synlophe, the anterior origin of the first subventral and subdorsal ridges at the anterior half of the oesophageal region, lateral and sublateral ridges taller and thicker than dorsals and ventrals, asymmetric male spicules with barbs present on each spicule tip, and an asymmetric dorsal ray of the bursa and the tail of adult females with a short cone. The diagnosis as well as generic and specific levels of haemonchine members depends mainly on the number and arrangement of ridge systems and their gradient (19). The importance of this system in taxonomic identification of nematodes was firstly studied by Skrjabin et al. (28) and Durette-Desset (6) through sections at the worm mid-body (4). ...

Redescriptions of Haemonchus mitchelli and Haemonchus okapiae (Nematoda: Trichostrongyloidea) and Description of a Unique Synlophe for the Haemonchinae
  • Citing Article
  • October 2002

Journal of Parasitology

... For example, transverse sections at the level of the esophagealeintestinal junction reveal the presence of 30 ridges in H. contortus and 34 in H. placei . Specific patterns of distribution for ridges in the subventral and sublateral fields in the esophageal region of the body of adult nematodes are diagnostic, and provide a capacity for robust identification of individual males and females Lichtenfels et al., 1994Lichtenfels et al., , 2001Lichtenfels et al., , 2002. Concurrently, morphometric protocols linked to discriminant analysis for spicules provided an alternative means for rapid identification; however, such protocols are limited to males of H. contortus and other species in domesticated ruminants (Jacquiet et al., 1997). ...

Haemonchus horaki n. sp. (Nematoda: Trichostrongyloidea) from the Grey Rhebuck Pelea capreolus in South Africa
  • Citing Article
  • October 2001

Journal of Parasitology

... However, anterior morphogenesis was partially arrested in vitro compared with NSG mouse-derived larvae ( Figure 2C). In the dog, larvae complete the L3-L4 molt rapidly, the vast majority by 3 days post-infection (Lichtenfels et al., 1985). In our cultures, ∼50% of the day 14 L4 had completed molting, with cuticle casts evident in the culture media. ...

Morphogenesis of developmental stages of Dirofilaria immitis (Nematoda) in the dog
  • Citing Article
  • January 1985

... Two 5% (5 ml) subsample were taken from each aliquot and examined to quantify larvae. Adult nematodes were identified to species level according to published descriptions of morphological characteristics, including reproductive structures, synlophe and esophageal valve and quantified [39][40][41][42][43][44] . Identification of the larvae was not done to the developmental stage nor species taxonomic rank. ...

Cuticular ridge patterns of Marshallagia marshalli and Ostertagia occidentalis (Nematoda: Trichostrongyloidea) parasitic in ruminants of North America
  • Citing Article
  • January 1989

Proceedings of the Helminthological Society of Washington

... Morphological traits of Haemonchus worm populations of cattle and sheep origin often differ. However, they do show some phenotypic traits that are similar, making measurements crucial for the classification of individual worms (6,8). Therefore, proper identification and understanding of the epidemiology of H. placei are crucial for implementing sustainable control measures and minimizing the economic impact of the disease in Africa (9). ...

Spicule lengths of the ruminant stomach nematodes Haemonchus contortus, Haemonchus placei, and their hybrids
  • Citing Article
  • January 1988

Proceedings of the Helminthological Society of Washington

... These morphological characteristics are consistent with those reported in several studies that morphologically characterized H. contortus in goats (69)(70)(71). Importantly, the role played by SEM in detecting and characterizing Haemonchus spp. was documented in several studies (21,(72)(73)(74)(75)(76). In this study, SEM was used to identify and differentiate some ultrastructures that aid in the taxonomic differentiation of several Haemonchus spp. ...

Cuticular ridge patterns of Haemonchus contortus and Haemonchus placei (Nematoda: Trichostrongyloidea)
  • Citing Article
  • January 1986

Proceedings of the Helminthological Society of Washington

... Two 5% (5 ml) subsample were taken from each aliquot and examined to quantify larvae. Adult nematodes were identified to species level according to published descriptions of morphological characteristics, including reproductive structures, synlophe and esophageal valve and quantified [39][40][41][42][43][44] . Identification of the larvae was not done to the developmental stage nor species taxonomic rank. ...

Cuticular ridge patterns of seven species of Ostertagiinae (Nematoda) parasitic in domestic ruminants
  • Citing Article
  • January 1988

Proceedings of the Helminthological Society of Washington

... Species with a Type 2 lateral synlophe (i.e., three continuous and parallel ridges) had a long valve, while those with a Type 1 (i.e., only one continuous ridge in each lateral field) had a shorter valve. Other studies of the Ostertagiinae of domestic and sylvatic hosts have demonstrated the utility of the synlophe as a key in separating species [50][51][52]. Nonetheless, papers concerning the number of cuticular ridges of O. leptospicularis are limited, and are focused mainly on those at the midbody [13,18,19], which has been revealed herein as the most variable. This result is not consistent with further findings that suggest the number of ridges at the midbody to be constant. ...

Cuticular Ridge Pattern in Ostertagia gruehneri and Ostertagia arctica (Nematoda: Trichostrongyloidea) from Caribou, Rangifer tarandus</i
  • Citing Article
  • January 1990

Journal of the Helminthological Society of Washington

... Gut contents were first filtered through 150 µm sieve and then all contents were examined using a stereo microscope. Every parasite recovered from the gastrointestinal organs was cleaned with physiological saline, fixed in hot 70% alcohol, and identified morphologically (2,4,13,21,22) with a light microscope (Nikon Eclipse E 600). After identification, parasites were micro-photographed (Nikon DXM 1200 F camera) and preserved in ethanol-glycerin-formalin protective solution. ...

Cuticular Ridge Patterns of Nematodirus (Nematoda: Trichostrongyloidea) Parasitic in Domestic Ruminants of North America, with a Key to Species
  • Citing Article
  • January 1983

Proceedings of the Helminthological Society of Washington