Anhydrobiosis in the infective juveniles of Trichostrongylus colubriformis (Nematoda: Trichostrongylidae)

The infective juveniles of Trichostrongylus colubriformis can survive exposure to 0% relative humidity after desiccation at higher relative humidities. During rehydration there is a lag phase before recovery. The infective juveniles are thus capable of anhydrobiosis. Removal of the sheath does not affect desiccation survival but does affect the duration of the lag phase. Morphological changes during the lag phase are described. The appearance of birefringence in the muscle cells during the anomalous shrinkage which occurs during the lag phase is considered to reflect physiological changes necessary for the recovery of normal muscle function.     

Revision of the genus Haemonchus Cobb, 1898 (Nematoda: Trichostrongylidae)

Summary Only nine species of the genus Haemonchus are considered valid, namely, H. contortus (Rudolphi, 1803) Cobb, 1898 (type), H. bedfordi Le Roux, 1929, H. dinniki Sach, Gibbons & Lweno, 1973, H. krugeri Ortlepp, 1964, H. lawrencei Sandground, 1933, H. longistipes Railliet & Henry, 1909, H. mitchelli Le Roux, 1929, H. similis Travassos, 1914 and H. vegliai Le Roux, 1929. These are redescribed. H. bispinosus Molin, 1860, H. placei Place, 1893, H. cervinus Baylis & Daubney, 1922, H. okapiae van den Berghe, 1937 (in part), H. tartaricus Evranova, 1940, H. contortus contortus Das & Whitlock, 1960, H. contortus cayugensis Das & Whitlock, 1960, H. contortus bangalorensis Rao & Rahman, 1967, H. contortus hispanicus Martínez Gómez, 1968, H. contortus kentuckiensis Sukhapesna, 1974 and H. contortus var. uktalensis Das & Whitlock, 1960 are considered synonyms of H. contortus (Rudolphi, 1803) Cobb, 1898.The synonymy of H. lunatus Travassos, 1914, H. atectus Lebedev, 1929, H. pseudocontortus Lebedev, 1929 and H. fuhrmanni Kamensky, 1929 with H. contortus is confirmed. H. okapiae van den Berghe, 1937 (in part) is considered a synonym of H. mitchelli Le Roux, 1929 and H. bubalis Chauhan & Pande, 1968 is considered a synonym of H. similis Travassos, 1914. H. bovis Bonelli, 1941 and H. contortus var. kashmirensis Fotedar & Bambroo, 1965 are considered species inquirendae. An illustrated key to the species of the genus is provided.Part of a thesis approved by the University of London for the award of the Ph.D. degree.Part of a thesis approved by the University of London for the award of the Ph.D. degree.     

Justice to Trichostrongylus longispicularis Gordon, 1933 (Nematoda: Trichostrongylidae)

Summary The literature on Trichostrongylus longispicularis Gordon, 1933 and T. lerouxi Biocca, Chabaud & Ghadirian, 1974 is critically reviewed. It is concluded that T. longispicularis is a valid species and that T. lerouxi is a synonym. T. longispicularis is defined and a neotype is designated.     

Observations on the routes of infection of Oswaldocruzia filiformis (Nematoda: Trichostrongylidae) in amphibia

The oral, percutaneous and subcutaneous routes of infection of Oswaldocruzia filiformis were investigated in amphibia. Tadpoles of Bufo bufo and Rana temporaria can be infected with O. filiformis when kept temporarily in a suspension of infective larvae in water. Larval stages and subadults were found in tadpoles. All stages of the parasite, including egg-producing females, were found after metamorphosis of the host. However, under natural circumstances infection of tadpoles seems unlikely. Oral infections in metamorphosed hosts of both species were successful in 97.5% of the host animals used. The first eggs appeared 29 days after infection in the faeces. The oral route seems to be normal for O. filiformis in amphibia. Experiments on percutaneous infections did not reveal actual penetration of larvae in or through the skin nor a subsequent migration through host tissues. Sometimes a few larvae were found in the stomach and intestine, but in these particular cases the experimental conditions did not totally exclude the possibility of oral infections. Consequently, the percutaneous route of infection is not plausible for O. filiformis. Subcutaneous inoculation of infective larvae seems to be a possible way of establishing experimental infections. Erratic localisation of the parasite in the enlarged gall bladder of the host was observed.     

Synlophe patterns of the Haemonchinae of ruminants (Nematoda: Trichostrongyloidea)

The pattern of longitudinal ridges (synlophe) on the external cuticular surface of trichostrongylid nematodes has been shown to be of value for distinguishing species and determining relationships among higher taxa. In the process of studying Mecistocirrus digitatus, the large stomach worm of bovids of Asia that has been imported and established in the Americas, we observed remarkably similar synlophe patterns to those described for 3 species of Haemonchus and to those we examined in a species of Ashworthius. In all 3 genera, the synlophe is absent from the posterior part of the body. Only in Haemonchus does the synlophe extend beyond midbody. In both M. digitatus and Ashworthius sidemi, the synlophe extends posteriorly only about 1/4 of body length. In all 3 genera, the synlophe consists of about 30 ridges in the region of the esophagus with variation among species in specific areas, including additional pairs of subventral and subdorsal ridges and different lengths of sublateral ridges. This information is useful for identifying species and determining relationships among these large stomach worm parasites of cattle, sheep, goats, and farmed and wild cervids.     

Similarities between species of the Ostertagiinae (Nematoda: Trichostrongyloidea) in relation to host-specificity and climatic environment

Multivariate analyses of similarities between species of the Ostertagiinae were performed on the data from 585 publications. The environmental factors were 12 climates and host-specificity in ruminants (40 species) for 16 species of ostertagiines. This approach can be a useful tool for distinguishing morphs from species. The following pairs (species and its possible morph) of ostertagiines are proposed: Ostertagia ostertagi — O. lyrata, O. leptospicularis — O. kolchida, O. gruehneri — O. arctica, Teladorsagia circumcincta — T. trifurcata, Marshallagia marshalli — M. occidentalis, Spiculopteragia boehmi — S. mathevossiani, and S. asymmetrica — S. quadrispiculata.     

Apparent absence of genetic differences among species of Teladorsagia (Nematoda: Trichostrongylidae)

The technique of allozyme electrophoresis was applied to three species of Teladorsagia present in sheep to determine the extent of genetic variation among species. Thirty-four enzyme loci were established of which 22 were invariant and 12 were shown to be polymorphic. No fixed allelic differences were detected among the species and the level of polymorphism was within the range found commonly between populations of a single species. Therefore, the genetic data support breeding data and existing morphological evidence that T. circumcincta, T. davtiani and T. trifurcata as currently recognized do in fact belong to a single species.     

Development of Immunity to Ostertagia ostertagi (Trichostrongylidae: Nematoda) in Pastured Young Cattle

This experiment comprised 3 groups of calves, (+P2), (−P2) and (−P1), which all started their first grazing season as parasite-free calves. The (+P2)- and (−P2)-group grazed 2 seasons. In the first season the (−P2)-group of calves was grazing a pasture with no detectable trichostrongyles and treated with anthelmintics every second week. The untreated (+P2)-group grazed an Ostertagia ostertagi contaminated pasture. During the second grazing season these 2 original groups grazed together with a new group of first-year grazing calves (−P1) on paddocks infected with O.ostertagi. Parasitological analyses showed that (+P2)-group had negligible egg excretions in the second year in comparison with (−P2) and (−P1). This indicated, that the egg output may be regulated through acquired immunity. The difference in egg excretions was not reflected in the serum pepsinogen levels, which were only slightly elevated for all groups in the second year. Post mortem examination at the end of the experiment showed that only the (−P1)-group harboured relatively high numbers of worms in the abomasa at that time. Antibodies of 3 immunoglobulin classes were investigated: IgA, IgG1 and IgG2. The IgA and IgGl responses correlated with the presence of developing and adult worms in the abomasa and they remained elevated in the (+P2)-group throughout the experiment, perhaps indicating an involvement of these antibodies in a protective immune response. In the (−P2)-group the IgA and IgG1 showed fast and sharp rises during the second season that most likely were age-related and as such a result of maturation of the immune system. The role of IgG2 is unclear as the IgG2 response was weak in all groups of calves and difficult to relate to the parasitological data.     

Haemonchus contortus (Nematoda: Trichostrongylidae) is much more sensitive than Caenorhabditis elegans (Nematoda: Rhabditidae) to the ovicidal action of thiabendazole

When eggs of the trichostrongylid nematode Haemonchus contortus were exposed to thiabendazole, the concentration required to prevent hatching in 90% of the eggs (MIC90) was found to be 0.1 microg/ml (using 1% dimethylsulfoxide [DMSO] as solvent). In contrast, eggs of the free-living rhabditid nematode Caenorhabditis elegans hatched at normal rates at a concentration 200 times higher, i.e., 20 microg/ml, and showed only a partial inhibitory effect at a concentration 1,200 times higher, i.e., 120 microg/ml (in 3% DMSO). Because solubility limitations precluded the testing of higher concentrations of thiabendazole, a more soluble derivative, 5-([1-methylethoxy]carbonylamino)-2-(4-thiazloyl)1H-++ +benzimidazolyliminoacetic acid N,N-diethylethanamine salt, was tested against C. elegans eggs. The MIC90 was found to be 400 microg/ml, and although the derivative was not tested against H. contortus eggs, this finding further suggests that C. elegans eggs have an exceptionally low degree of benzimidazole sensitivity.     

Nematodirus nemorhaedi sp. n. (Nematoda: Trichostrongylidae) from the Amur goral Nemorhaedus caudatus raddeanus]

Nematodirus nemorhaedi sp. n. is described. The new species was found in the small intestine in three long-tailed gorals from the Maritime Territory. The species differs from other species of the genus, parasites of ungulates, by very large (over 1.5 mm) spicules and characteristic structure of their distal end in males; by long (about 1 mm) ovijector in females and by a specific combination of characters of synloph, genital bursa in males, sizes of body, structure of vulva, sizes and shape of eggs and tail in females.     

Supplement to the description of Longistrongylus thalae (Troncy & Graber, 1973) Gibbons, 1981 (Nematoda: Ostertagiinae)

Longistrongylus thalae (Troncy & Graber, 1973) Gibbons, 1981 is briefly re-described. The synlophe, the spicules and the apical cephalic structures, previously either inadequately or not figured, are illustrated. The authors concur with Gibbons (1981) that this nematode belongs to the genus Longistrongylus Le Roux, 1931, but consider the degree of asymmetry of the ovejector, as depicted by Troncy & Graber (1973), as not being representative of the species.