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PubMed1975

Use of hot formaldehyde fixative in processing plant-parasitic nematodes for electron microscopy.

A preparative technique is formulated for processing plant-parasitic nematodes of the order Tylenchida for electron microscopy. A population of Dolichodorus heterocephalus is used as test objects. One and a half grams of paraformaldehyde are dissolved in 25 ml of water at 60 C. Five drops of 1 N sodium hydroxide are added to clear the solution, which is then cooled to room temperature. Two and a half milliliters of 25% glutaraldehyde are added with 23 ml 0.1 M phosphate buffer, pH 7.3, and 0.2 M with respect to sucrose. The final solution contains 3% formaldehyde and 1% glutaraldehyde and is pH 7.2. It is heated to 70 C, poured over specimens, and allowed to cool to 4 C in 2 hr. The nematodes are then incised in a fixative containing 2% glutaraldehyde and 5% dimethyl sulfoxide at 4 C for 16-24 hr. Five milliliters of 25% glutaraldehyde and 2.5 ml of dimethyl sulfoxide are combined in 17.5 ml of water. Twenty-five milliliters of phosphate buffer (supplemented as above) are added. The final pH is 7.2. The glutaraldehyde, aided by dimethyl sulfoxide, uniformly and permanently fixes the nematode tissues. The specimens are embedded in agar. Following a 30-min buffer wash (4 C) they are postfixed in buffered 2% osmium tetroxide for 2 hr at room temperature, washed, and dehydrated through an ethanol series and two acetone baths. Dehydration includes a 2-hr stop in 75% ethanol containing 2% uranyl acetate. After embedding in Spurr's epoxy resin, specimens are sectioned and poststained in 0.5% aqueous acetate for 6 min and saturated aqueous lead citrate 3--4 min. This technique reduces killing time to less than 2 sec, straightens specimens for easier orientation, and eliminates the typically high internal pressure of nematodes which causes displacement of internal structures observed with other fixation techniques.

Animals↗

PubMedDate not supplied

The immunological consequences of nematode infection.

Nematode infections in the gut induce a strong immune response which is rapidly detected parenterally. The response is thymus-dependent and long-lasting and involves both antibodies and cell-mediated reactions. The immunological response to unrelated antigens, tumours and other infectious organisms is altered in animals infected with nematodes. Both antibodies and sensitized lymphocytes participate in the immune response which affects the nematodes themselves, and characteristically the lymphocyte-dependent step cannot act in lactating animals and is neither induced nor able to act in young animals. Present evidence suggests that, despite their well-known association with helminth infections, parasite rejection from the gut does not require the participation of IgE antibodies, mast cells or eosinophils. Homing of lymphoblasts from the mesenteric lymph node or thoracic duct lymph to the small intestine is increased in rats and mice infected with Nippostrongylus brasiliensis or Trichinella spiralis and the increase is antigenically non-specific. In mice infected with T. spiralis this increase is represented mainly by thymus-derived lymphoblasts.

Animals↗

PubMed2024

The parasitic nematode Haemonchus contortus lacks molybdenum cofactor synthesis, leading to sulphite sensitivity and lethality in vitro.

Sulphite oxidase has an essential role in detoxifying environmental and endogenously generated sulphite into sulphate and requires the molybdenum cofactor (Moco) to function. Until recently it was believed that the synthesis pathway for Moco was so important for survival that it was conserved in all multicellular animals. Here we report the use of comparative genomics to identify the absence of the first enzyme involved in Moco synthesis in Haemonchus contortus, a highly pathogenic and economically important helminth of livestock that, similar to many parasitic nematode species, has proved difficult to maintain in vitro. We show that Moco deficiency in Haemonchus leads to a high sensitivity to environmental sulphite and limits the ability to maintain the early parasitic larval stages in vitro. Analogous losses in Moco synthesis in other recently sequenced nematode species are also identified. These findings may lead to improved culture methods for parasitic nematodes and to novel approaches for their control.

Animals↗

PubMed2026

A cooperative regulatory module between TAGL2 and JMJC1 activates specific defense genes against root-knot nematodes in tomato.

Plant-parasitic nematodes (PPNs) threaten global food security. Although epigenetic modifications are crucial for plant immunity, how histone modifiers contribute to root-knot nematodes (RKNs, Meloidogyne incognita) resistance remains unclear. Here, using genetic, molecular and biochemical approaches, we investigated the epigenetic and transcriptional mechanisms underlying RKN resistance mediated by the histone demethylase (HDM) JMJC1 and the MADS-box transcription factor TAGL2 in tomato (Solanum lycopersicum). We identified JMJC1 as an RKN-induced positive defense regulator targeting H3K9me3 and H3K27me3 histone marks. JMJC1 physically interacts with TAGL2, which also positively regulates RKN resistance. Transcriptomic analysis indicated that TAGL2 regulates multiple layers of the plant defense network, transcriptionally activating representative genes from distinct pathways (including PUB10, bHLH98, CCaMK, and SAUR3), which we validated as positive regulators of RKN resistance via virus-induced gene silencing (VIGS). At the chromatin level, TAGL2 and JMJC1 co-regulate these loci, associating with localized H3K9me3 and H3K27me3 reduction. Furthermore, TAGL2 directly activates JMJC1 transcription, establishing a positive feedback loop that amplifies immune signaling. Our findings reveal a cooperative model wherein a HDM and a transcription factor coordinate at specific loci to fine-tune multiple defense layers at both epigenetic and transcriptional levels, providing insights for breeding durable nematode-resistant plants.

Solanum lycopersicum↗

PubMed1979

Experimental transmission of gastro-intestinal nematodes between sheep (Ovis aries) and Thomson's gazelles (Gazella thomsonii).

Experimental cross-transmission of gastro-intestinal nematodes between Merino sheep (Ovis aries) and Thomson's gazelles (Gazella thomsonii) from similar but separate grazing habitats in Kenya was studied. Cross-transmission did occur with some species but the faecal egg counts of sheep were higher than the gazelles' following infection with larvae isolated from either sheep or gazelles. Of the 11 gastro-intestinal nematodes which became established in gazelles following infection with larvae cultured from nematodes in gazelles, only Haemonchus contortus, Trichostrongylus probolurus and Cooperia hungi were infective for sheep. Following infection with larvae of either sheep or gazelle origin, the H. contortus recovered from the sheep at necropsy were more numerous and had greater average weights, lengths and spicule lengths than those recovered from the gazelles. This would suggest that H. contortus is primarily a sheep parasite. It is concluded that Thomson's gazelles probably would not contribute significantly to the problem of haemonchosis in sheep in areas of shared grazing, unless efforts were being made to eradicate the parasite from sheep, in which case the gazelles would act as a continuing reservoir of infection.

Animals↗

PubMed1975

Seasonal variations in the gastro-intestinal nematode populations of Scottish hil sheep.

In each of two consecutive years, groups of breeding ewes were removed from a hill farm in the west of Scotland on four occasions, namely late pregnancy, early lactation, autumn and early winter. At slaughter the major nematode genus present in the alimentary tract was Ostertagia, with O circumcincta the predominant species but three species previously found in Scottish hill sheep, Bunostomum trigonocephalum, Strongyloides papillosis and Chabertia ovina were absent. An absolute increase in total nematode burden and faecal egg count was apparent in the ewes commencing in late pregnancy, reaching a maximum during lactation and falling again in autumn and early winter. This peri-parturient increase in the nematode population could not be solely attributed to the maturation of previously inhibited larval stages but was primarily the result of the development of recently ingested infection; the latter situation thought to be due to a temporary relaxation of immunological response by the ewe at parturition or early lactation. Serum pepsinogen values in ewes remained elevated throughout the grazing season and were always higher than those of their lambs, suggesting that the ewe, although allowing few parasites to become established, was under considerable challenge in the autumn. The worm burdens of the lambs were always low in autumn and early winter with Ostertagia spp being the major genus present during the autumn and Trichostrongylus spp being the predominant genus during the early winter.

Abomasum↗

PubMed1975

Relationship of pasture rotation to acquisition of gastrointestinal nematodes by sheep.

In a study of the relationship between pasture rotation in Illinois and acquisition of nematodes (mostly Haemonchus contortus) and body weight gains by lambs grazing with their ewes, 2 pasture rotation systems were tested. (1) Lambs and ewes were rotated through a series of 12 alfalfa-bromegrass-lespedeza pastures, each pasture being grazed for 3 to 4 days and rested for 5.5 weeks; 4 complete rotations were done during a 168-day grazing season. (2) Lambs and ewes were moved every 2 days, and 3 complete rotations of 50, 42, and 54 days, respectively, were done during the 146-day grazing season. The lambs under rotation had more nematodes and gained less weight than nonrotated control lambs, although rotation increased the amount of pasturage. Rotation is not recommended to control nematode parasitism of sheep in Illinois.

Animals↗

PubMed1979

Anthelmintic activities of B1a fraction of avermectin against gastrointestinal nematodes in calves.

Anthelmintic activities of the B1a fraction of avermectin were evaluated in a controlled experiment. Twenty 12-week-old calves artificially infected with gastrointestinal nematodes were allotted to four groups. Calves in group 1 were used as nonmedicated controls; other calves in groups 2, 3, and 4 were given (orally) B1a avermectin at dosage levels of 50, 100, and 200 microgram/kg of body weight, respectively. These treatments were given 35 days after calves were inoculated with infective nematode larvae. In groups 2, 3, and 4, overall reductions (based on geometric means) were 98.6%, 98.7%, and 98.4%, respectively. These reductions were highly significantly different (P less than 0.01) from the control calves. Nematodes in the calves were Haemonchus contortus. Ostertagia ostertagi, Trichostrongylus axei, T colubriformis, Cooperia oncophora, C punctata, and Oesophagostomum radiatum.

Animals↗

PubMed1977

Cryopreservation of the infective larvae of the common nematodes of ruminants.

Exsheathed infective larvae (L 3) of 19 species of nematodes were tested for infectivity in either sheep or cattle after they had been frozen in 0,9% NaCl solution, stored for a relatively short time in the gas phase of liquid nitrogen and subsequently thawed. In addition, 13 of these species were tested after similar storage for up to 18 months. In sheep, Haemonchus contortus, Ostertagia circumcincta, Trichostrongylus axei, Trichostrongylus colubriformis, Nematodirus spathiger and Oesophagostomum columbianum were viable after 2 years of cryopreservation, a mean of greater than 90% of the L 3 being alive when thawed after this period. Similar results were obtained with Chabertia ovina L 3 after 18 months and with Marshallagia marshalli, Trichostrongylus falculatus and Dictyocaulus filaria, after a short period of freezing. On the other hand, Gaigeria pachyscelis and Strongyloides papillosus survived freezing for up to 7 months but neither was viable at the end of this period, nor was exsheathed G. pachyscelis viable without freezing. Most of these infestations were established by inoculating the infective larvae into the abomasum and/or duodenum. M. marshalli, T. falculatus and C. ovina also proved infective after oral dosing. D. filaria, the only other species tested by this route, was not infective when dosed per os after thawing. The infective larvae of the bovine nematodes, Haemonchus placei, Ostertagia ostertagi, Nematodirus helvetianus, Oesophagostomum radiatum, Cooperia pectinata and Cooperia punctata survived freezing for a mean of 26 months, greater than 90% being alive on thawing, but infectivity was generally lower than with the same genera in sheep. Even when not frozen, exsheathed Bunostomum phlebotomum was non-infective. When Cooperia spp. after thawing were tested for infectivity by the oral route, more worms developed in one calf infested orally than in another infested by inoculation into the duodenum. Ova of H. contortus, M. marshalli, O. circumcincta, T. colubriformis, T. falculatus, N. spathiger, C. ovina, H. placei, O. ostertagi, Cooperia spp. and N. helvetianus were recovered from the faeces of animals infested with cryopreserved L 3. No ova of O. columbianum or O. radiatum were recovered from faeces, because differential larval counts were performed before they were patent. Nevertheless, gravid females were obtained post-mortem. Frozen L 3 of N. helvetianus were used to re-establish a pure strain in calves, 2,3 million ova being recovered from infestations with 10 670 L 3 frozen for 26 months. The infectivity of the progeny of frozen L 3 was tested with M. marshalli and C. ovina. In both instances infectivity was high and the worms which developed also produced ova, thus completing the cycle. This appears to be the first report of infective larvae of parasitic nematodes retaining their infectivity after being frozen in liquid nitrogen (gas phase) for longer than 2 years. This is also apparently the first time that M. marshalli T. colubriformis, T. falculatus, T. axei, N. spathiger, C...

Ancylostomatoidea↗

PubMed1978

Epidemiologic findings on canine and feline intestinal nematode infections from records of the Iowa state University Veterinary Clinic.

A wealth of data was available on intestinal nematode infections of dogs and cats in the Ames, Iowa, practice area served by the Iowa State University Veterinary Clinic. From July 1966 through June 1974, 8.5% of 33,594 dogs and 4.5% of 11,995 cats hospitalized for 1 or more days were recorded as infected with at least 1 type of intestinal nematode. For both dogs and cats, infection rates were generally higher in males than in females and in those that were sexually intact, compared with those that were neutered. The highest prevalence of hookworm infections in both dogs and cats was recorded in June and July, and the highest prevalence of ascarid infections in cats, but not in dogs, was in December. Seasonal patterns were not demonstrated for other nematode infections. Ascarid infections in dogs and cats and hookworms infections in dogs were most prevalent in 2-week-old to 2-month-old animals. Whipworm infections in dogs and hookworm infections in cats generally appeared at greater ages, reaching their highest prevalence in hosts 1 to 2 years old.

Animals↗

PubMed1978

Anthelmintic activity of fenbendazole against gastrointestinal nematodes in calves.

Anthelmintic activities of fenbendazole were evaluated in a controlled experiment. Forty calves artificially infected with gastrointestinal nematodes were allotted to 4 groups. Calves in group 1 were used as nonmedicated controls; the other calves were given (orally) fenbendazole at the dose level of 5 mg/kg in the forms of a suspension (group 2), medicated feed to individual calves (group 3), and medicated feed to the group (group 4). These treatments were given on day 35 after calves were inoculated with infective nematode larvae. In groups 2, 3, and 4, overall reductions (based on geometric means) were 99.5%, 99.7%, and 99.6%, respectively. These reductions were highly significantly different (P less than 0.01) from the control calves. Nematodes present in the calves were Haemonchus contortus, Ostertagia ostertagi, Trichostrongylus axei, T colubriformis, Cooperia onchophora, C punctata, and Oesophagostomum radiatum.

Animals↗

PubMed1976

Intestinal nematodes of white-tailed deer in southeastern United States.

The small intestine, large intestine, and cecum of 975 white-tailed deer (Odocoileus virginianus) from 83 localities in 13 southeastern states were examined for nematodes. In order of prevalence, the following parasites were found: Capillaria bovis, Eucyathostomum webbi, Monodontus louisianensis, Nematodirus odocoilei, Oesophagostomum venulosum, Trichuris sp, Cooperia punctata, Trichostrongylus longispicularis, Strongyloides sp, Cooperia oncophora, Cooperia spatulata, Cooperia sp, and Trichostrongylus calcaratus. Over one-half of the deer examined were free of intestinal nematodes, and most infected deer harbored few parasites. Of the most prevalent species, C bovis, N odocoilei, O venulosum, and Trichuris sp were widely distributed, whereas M louisianensis and E webbi were restricted in distribution. Severe pathogenicity was associated with only heavy Strongyloides sp infections in 2 penned deer. The findings of this study suggested that white-tailed deer of the Southeast are insignificant in the epizootiology of important intestinal nematodes of domestic livestock.

Animals↗

PubMed1975

Four endoparasitic nematode destroying fungi isolated from sand ridge state forest soil.

A survey to determine the endoparasitic nematode destroying fungi located within Sand Ridge State Forest of Illinois was conducted from 1 January to 3 April 1973. A total of seven nematode destroying fungal species were isolated from the collected soil samples. Harposporium helicoides, H. crassum, H. lilliputanum are endoparasitic nematophagous fungi that have been isolated previously from the forest soil. Acrostalagmus gonoides, A. obovatus, Cephalosporium balanoides, and Monacrosporium cionopagum are nematophagous fungal species that had not been isolated previously from Illinois soil. Soil pH's and soil nutrient levels were not important in the isolation frequency of the collected endoparasitic nematode destroying fungi.

Illinois↗

PubMed2024

A gene with a thousand alleles: The hyper-variable effectors of plant-parasitic nematodes.

Pathogens are engaged in a fierce evolutionary arms race with their host. The genes at the forefront of the engagement between kingdoms are often part of diverse and highly mutable gene families. Even in this context, we discovered unprecedented variation in the hyper-variable (HYP) effectors of plant-parasitic nematodes. HYP effectors are single-gene loci that potentially harbor thousands of alleles. Alleles vary in the organization, as well as the number, of motifs within a central hyper-variable domain (HVD). We dramatically expand the HYP repertoire of two plant-parasitic nematodes and define distinct species-specific "rules" underlying the apparently flawless genetic rearrangements. Finally, by analyzing the HYPs in 68 individual nematodes, we unexpectedly found that despite the huge number of alleles, most individuals are germline homozygous. These data support a mechanism of programmed genetic variation, termed HVD editing, where alterations are locus specific, strictly governed by rules, and theoretically produce thousands of variants without errors.

Animals↗

PubMed1977

Bacterial parasite of a plant nematode: morphology and ultrastructure.

The life cycle of a bacterial endoparasite of the plant-parasitic nematode Meloidogyne incognita was examined by scanning and transmission electron microscopy. The infective stage begins with the attachment of an endospore to the surface of the nematode. A germ tube then penetrates the cuticle, and mycelil colonies form in the pseudocoelom. Sporulation is initiated when terminal cells of the mycelium enlarge to form sporangia. A septum within each sporangium divides the forespore from the basal or parasporal portion of the cell. The forespore becomes enclosed by several laminar coats. The parasporal cell remains attached to the forespore and forms the parasporal microfibers. After the newly formed spores are released into the soil, these microfibers apparently enable a mature spore to attach to the nematode. These results indicate that the endoparasite is a procaryotic organism having structural features that are more common to members of Actinomycetales and to the bacterium Pasteuria ramosa than to the sporozoans or to the family Bacillaceae, as previous investigatios have concluded.

Actinomycetales↗

PubMed2026

Diversity at the HYP1 locus in potato cyst nematodes does not result from developmentally-programmed somatic mutations.

Most genetic diversity stems from spontaneous mutations, that is, errors in DNA repair or replication. But for dozens of organisms across the tree of life, mutations at specific loci are not spontaneous but developmentally programmed: effectively, some organisms edit their own DNA sequences. This is perhaps most common among pathogens and parasites, many of which use editing to diversify genes that produce important antigens. Plant-parasitic potato cyst nematodes are damaging agricultural pests that establish a lifelong feeding site inside the root of their host plant. We previously observed extensive diversity of rare alleles at HYP1, the most highly expressed gene that encodes a protein secreted by potato cyst nematodes during parasitism. Importantly, HYP1 alleles differ from each other by complex, in-frame rearrangements of short repeated sequence motifs within a single exon. Combining several lines of evidence, we previously hypothesized that potato cyst nematodes use developmentally-programmed mutations, or editing, to diversify HYP1 alleles in the soma. In the current work, we now test this hypothesis. We employ highly accurate long-read DNA sequencing of a simplified genetic system to identify potential rare edited alleles, we use a transgenic yeast system to describe large de novo mutations at HYP1, and we interpret our findings in light of key population genetic parameters as well as the genetic diversity surrounding HYP1 and across the genome.

Animals↗

PubMed1975

The metabolism of foreign compounds in the cestode, Moniezia expansa, and the nematode, Ascaris lumbricoides var suum.

1. The ability of the cestode Moniezia expansa and the nematode Ascaris lumbricoides var suum to metabolize foreign compounds has been assessed. 2. Both species were unable to oxidase aldrin, aniline, biphenyl, butylbenzene and nitrobenzene or to demethylate aminopyrine, and 4-nitroanisole. 3. M. expansa and A. lumbricoides var suum readily induced 4-nitroanisole, nitrobenzene, 4-nitrobenzoic acid and 4-nitrophenol to the corresponding amines. Azobenzene, dimethylaminoazobenzene, and 1,2-dimethyl-4-(4-carboxyphenylazo)-5-hydroxybenzene were also reduced. 4. Hydrolysis of esters, acetanilide, acetylsalicylic acid, aryl sulphates and aryl phosphates took place readily. However, beta-glucuronides were not hydrolysed. 5. The following reactions were not detected in either species: phosphate, sulphate, beta-glucuronide or beta-glycoside conjugation of phenolic compounds; acetylation of amino compounds, or the formation of glycine conjugates with 4-aminobenzoic acid or benzoic acid. 6. Male nematodes showed a higher rate of drug metabolism than female nematodes.

Acetanilides↗

PubMed1977

Nematodes in terrestrial gastropods from central Maine.

Seventeen-hundred terrestrial gastropods collected in central Maine were examined for Parelaphostrongylus tenuis and other nematodes. Prevalence of nematodes was 4 to 7% in most gastropod species, but was 19% in Pallifera spp. Cosmocercoides dukae and Rhabditis spp. were the most common nematodes recovered. Only four P. tenuis larvae (prevalence 0.1%) were found. Foci important for transmission of P. tenuis in Maine have not yet been found.

Animals↗