Grazing cattle can be infected with a variety of gastrointestinal nematode species. In temperate regions, the most common of these species are considered to be the abomasal parasite, Ostertagia ostertagi, and the small intestinal dwelling nematode, Cooperia oncophora. Control of these nematodes is largely reliant upon the use of three anthelmintic classes: the benzimidazoles, imidazothiazoles and the macrocyclic lactones (ML). Worldwide, reports of anthelmintic resistance in cattle nematodes have increased in recent years; however, little information is available regarding this issue in farmed cattle in the UK. Knowledge is also lacking regarding anthelmintic usage practices, and whether or not the current methods used to detect anthelmintic resistance in cattle nematodes are robust and accurate. In this thesis, a number of approaches were taken to investigate these issues. A questionnaire study was conducted to evaluate anthelmintic usage and nematode control practices on a cohort of UK cattle farms. Descriptive analysis of the responses revealed that first season grazing calves were administered with anthelmintics, on average, twice per year (ranging between once and four times per year). It was also found that farmers depended heavily on ML products, with 80% of respondents administering a ML product in the previous 12 months and only 55% of respondents employing a quarantine treatment for cattle brought onto their farm. Faecal egg count reduction tests (FECRT) were then performed on 20 of the respondents’ farms, using injectable ivermectin (IVM). Two types of faecal egg count (FEC) methodology (a double centrifugation salt flotation method sensitive to one egg per gram and a McMaster method sensitive to 50 eggs per gram) were compared to investigate their utility in determining anthelmintic sensitivity of the derived nematode populations. A number of different statistical analyses were also performed to determine the optimum method of analysis for determining anthelmintic efficacy taking into account the effect of using arithmetic or geometric means, sensitivity of the FEC method and the effect of parametric bootstrapping. Of the 20 farms tested, 13 showed indications of inefficacy of IVM. Genus identification analysis of larvae derived from faecal samples obtained from the FECRT cohort indicated a minimum of 95% Cooperia spp. larvae in the post-treatment samples. Logistic regression analysis was also used to determine associations between management strategy on beef and dairy cattle enterprises and risk factors for IVM resistance. Farmers with dairy cattle were significantly less likely to use FEC (P = 0.013) or isolate new animals at quarantine (P = 0.013) compared to beef cattle farmers. Farmers who routinely monitored FEC were significantly less likely to use anthelmintics than those who did not monitor FEC (P = 0.042) and farmers who sought advice from their veterinary surgeons were less likely to administer anthelmintics according to the average weight of the herd (P = 0.02). Nematodes from two of the farms on which IVM resistance was indicated by the field FECRT were then further passaged and both isolates subjected to a controlled efficacy test (CET). Results from the CET confirmed the presence of IVM resistant C. oncophora (using two different application methods: injectable and pour-on administration), as well as the presence of moxidectin-resistant C. oncophora, the first confirmation in the UK. Analysis of phenotypic parameters was conducted on 679 female C. oncophora recovered at necropsy from all treatment groups. For both isolates, nematodes recovered from calves administered with moxidectin (MOX) pour-on anthelmintic were found to be significantly shorter than nematodes surviving IVM administration and nematodes from untreated control calves. Oviposition was also examined; with no eggs in utero found in any of the nematodes surviving MOX administration. Differences in the numbers of eggs in utero surviving IVM application were observed between the two isolates and also between application methods. Subsequently, analysis of a small section of a glutamate-gated chloride channel (glc-6) gene was conducted to investigate the presence of a single nucleotide polymorphism (SNP) in the glc-6 gene that had been previously proposed to be associated with ML resistance. This was achieved by comparing sequences derived from male and female C. oncophora (from both isolates) obtained from untreated calves with sequences from nematodes that had survived IVM administration. The SNP was not identified in any of the parasites analysed. Due to time and labour costs for conducting FECRTs for detecting anthelmintic resistance, a migration inhibition test was examined for its utility in assessing IVM sensitivity of third stage larvae (L3) derived from populations that had been demonstrated to have varying IVM sensitivity in vivo. Following optimisation, dose response curves and effective concentration (EC50) estimates were generated for all populations, including single species laboratory isolates of O. ostertagi and C. oncophora and mixed species isolates derived from the field studies above. The data failed to correlate with the previously obtained in vivo anthelmintic sensitivity classification for each isolate. Overall, O. ostertagi appeared to be less sensitive to IVM in the LMIT compared to C. oncophora, regardless of the ML sensitivity status of the isolate under study. Thus, these experiments indicated that the LMIT may have limited utility for assessing ML sensitivity of mixed species nematode isolates generated from field samples. In summary, the work in this thesis has found that UK cattle farmers heavily rely upon ML anthelmintics and there are clear differences in parasite control practices between farmers in the dairy and beef sectors, which may influence the development of anthelmintic resistance. As it is unclear when new classes of anthelmintics will become available for cattle, it is imperative to prolong the effectiveness of the current effective classes and to detect anthelmintic resistance as it emerges. This thesis has explored some currently available tools for the detection of ML resistance, with a view to improving them with appropriate best practice advice to help protect the health and welfare of cattle.

No description available.

A cross-sectional survey was conducted in four areas in the communal area of Gweru District in the Midlands Province, Zimbabwe. The study was conducted at Mkoba, Mangwande, Chiwundura and Nsukamini. The objective of the study was to determine the prevalence of nematode infection in communal goats in Gweru District, and whether or not the prevalence was related to age, sex, breed or the season. The study was important as it would help in evaluating current strategies used in nematode control and designing low cost control strategies. One hundred and ninety-eight (198) communal goats made up of 49 males and 149 females ranging in age from one month to over twelve months were sampled. Of these, 100 were sampled during the wet season and the remaining 98 during the dry season. One hundred and fifteen (115) or 58% had significant egg counts per gram (epg) of faeces. Among the goats that had significant epg, 31 were males and 84 were females. All age groups were affected. The most common parasites encountered were Haemonchus, Trichostrongylus, Teladorsagia and Oesophagostomum. Haemonchus was the dominant species during the wet season. The proportion of goats that had a significant EPG during the wet season was significantly higher than during the dry season (X2=5.311; P≤0.05). There was no statistical significant difference in prevalence among the different age groups (X2=1.270; P≤0.05) and between males and females (X2=0.696; P≤0.05). Copyright / Dissertation (MSc (Veterinary Tropical Diseases))--University of Pretoria, 2009. / Veterinary Tropical Diseases / unrestricted

Reniform nematode, Rotylenchulus reniformis is a semi-endoparasitic nematode infecting over 300 plant species including important fiber crops like cotton. Introgression of reniform nematode resistance from a distantly-related resistant species Gossypium longicalyx into cultivated upland species Gossypium hirsutum has been a challenge. An approach towards achieving nematode resistance in crop plants has been to identify candidate parasitism genes expressed in the nematode facilitating infection of host plant species, and silencing the same through reverse genetic approaches like RNAi. A cDNA library constructed from the sedentary female stage of reniform nematode revealed an EST coding for C-type lectins and occurring in high frequency. Identification and characterization of C-type lectins in reniform nematode is important in understanding the immune system of nematode and in planning strategies for the development of reniform nematode resistant cotton varieties. A total of 11 C-type lectin gene family members were identified across six life stages of reniform nematode, with each member expected to play a significant role in the development and parasitic establishment with the host plant. Conserved sites characteristic of C-type lectins found in other organisms have been identified in the C-type lectin genes in reniform nematode for binding of Ca+2 and mannose. The highest level of expression of C-type lectins was observed in the sedentary female stage indicating it to be possibly the most sensitive stage to microbial infection and so a likely stage to target for its management. The site of secretion of C-type lectins in the sedentary female stage could be identified by in situ hybridization as the hypodermal region of the exposed posterior body region which is not inserted into the host root tissue. Phylogenetic analyses of C-type lectin domains of various nematode groups placed the plant-parasitic nematodes in one group indicating the possibility of co-evolution and probably carrying out a similar function aiding in the establishment of parasitism with host plants. Our findings now extend the spectrum of known nematode C-type lectin genes and suggest that lectin activity might be a more general feature of parasitism which could be explored in better understanding the interactions occurring at the host-nematode and nematode-pathogen interfaces.

No description available.

No description available.

Rotylenchulus reniformis (RN) nematode infection has been identified as a major biotic factor limiting cotton yield (~8%) in Mississippi. Cotton researchers are striving to develop resistance to RN and develop management practices to mitigate the problem. Reniform nematode and soil nitrogen (N) directly affect cotton growth and physiology, however, responses to RN and N may vary across a wide genetic background. The overall objective of this research was to determine the role that host plant resistance to reniform nematode and soil nitrogen plays in cotton growth, physiology, and yield and controlling RN populations. In experiment 1, the effect of RN on resistant (Gossypium barbadense introgressions; 08SS110-NE06.OP and 08SS100) along with a susceptible genetic standard (Deltapine 16) and a commercially, susceptible cultivar (PHY 490 W3FE) was studied based on growth, development, and yield characteristics under field conditions. In experiment 2, the effect of N application rates, ranging from 0-150%, with 100% being recommended rate, on early season morphological and physiological traits of the resistant and susceptible genotypes were studied in the presence and absence of RN under greenhouse conditions. In the field project, agronomic traits varied among genotypes at a given sampling time but growth rates, described by three-parameter sigmoidal function (r2 = 0.95 to 0.99), were not different among genotypes. Further, genotypes exhibited higher agronomic and physiological traits, including plant height, main stem nodes, leaf area, net photosynthetic rates, and hand-picked lint yields in 2018 than 2017. In the greenhouse study, 08SS110-NE06.OP performed physiologically better across RN environments than other genotypes, but growth rates with respect to soil N treatments, described by linear or quadratic function (r2 = 0.72 to 0.99), were not different among genotypes. No interactions between soil N treatments and RN based on physiological and growth traits were observed at the time of harvesting. In both projects, resistant genotypes suppressed reniform nematode population at the time of harvesting. RN resistant lines have no biological significant effect on plant growth, development, or yield but do suppress RN populations.

Thesis (M. Agric. (Plant Protection)) -- University of Limpopo, 2019 / Damage and significant losses of potato cultivar due to Meloidogyne incognita has become a serious challenge, after the withdrawal of synthetic chemical nematicides due to their environment-unfriendliness. Various alternatives have been investigated each with a wide range of drawbacks. Most phytonematicides were highly phytotoxic to crops, while their effects on nematode suppression were highly variable. The use of Nemarioc-AG phytonematicide at pre- and post-emergence would help in determining the level that is effective in supressing M. incognita without being phytotoxic. The objective of this study was to determine whether Nemarioc-AG phytonematicide could serve as pre- and post-emergent phytonematicide without inducing phytotoxicity while suppressing population densities of M. incognita. For achieving this objective, treatments, namely, 0, 2, 4, 8 and 16 g of Nemarioc-AG phytonematicide, were arranged in a randomised complete block design (RCBD), with 7 replicates. Potato seed tubers were sown into 20 cm pots, Nemarioc-AG phytonematicide placed above the tubers and covered with soil, after initiation of treatments 5 000 eggs and second stage juveniles (J2) of M. incognita per plant were inoculated. For post-emergent, treatments, replications and design were the same as in pre-emergent. Potato seed tubers were sown and inoculated with 5000 eggs and second-stage juveniles (J2) of M. incognita per plant after 100% emergence. Nemarioc-AG phytonematicide were applied 7 days after inoculation. Trials were conducted in autumn (February-April) 2017 (Experiment 1) and repeated in autumn 2018 (Experiment 2). Plant growth variables and selected nutrient elements were collected and analysed using the Curve Fitting Allelochemical Response Data (CARD) model and lines of best fit, respectively. In pre-emergent application, Experiment 1, MCSP was established at 1.95 g, with the overall xii sensitivity (∑k) being equal to zero. Therefore, in Experiment 1 and Experiment 2, all nutrient elements to increasing concentration of Nemarioc-AG phytonematicide exhibited negative quadratic relations. In both Experiments, nematode variables over increasing concentration of Nemarioc-AG phytonematicide on potato exhibited negative quadratic relations, except in Experiment 1, where J2 in roots exhibited positive quadratic relations, with models ranging between 72 to 99%. In post emergent, Experiment 1, MCSP was established at 1.57 g, with the overall sensitivity (∑k) being equal to 2. In Experiment 1 and Experiment 2, nutrient elements over increasing concentration of Nemarioc-AG phytonematicide exhibited positive and negative quadratic relations, with models ranging from 89 to 97%. In Experiment 1, nematode variables over increasing concentration of Nemarioc-AG phytonematicide exhibited negative quadratic relations, with models ranging between 92 and 98%. Positive and negative relations suggested that the product stimulated and inhibited plant growth or accumulation of selected essential nutrient elements, respectively. Increasing concentration of Nemarioc-AG phytonematicide had stimulated certain plant variables and inhibited population densities of M. incognita in pre- and post emergent application; therefore, this product was suitable for use as pre- and post emergent in management of nematodes on the test crop.

Upland cotton (Gossypium hirsutum ) is an important fiber crop grown throughout the southern United States. Plant-pathogenic nematodes are worm-like animals that feed on the roots of most agronomic crops, including cotton. The southern root-knot nematode (Meloidogyne incognita, RKN) and the reniform nematode (Rotylenchulus reniformis, RN) cause significant yield losses in cotton every year. Current sources of resistance are effective but limited, therefore historical screenings of cotton accessions were revisited in search for novel resistance sources. None were identified but many of the screened accessions possessed markers of known root-knot nematode and reniform nematode resistance. The emerging guava root-knot nematode (Meloidogyne enterolobii, GRKN) is a risk for upland cotton production, and identifying host plant resistance would greatly reduce the yield losses for growers. Assays were conducted on the currently available RN and RKN resistance sources inoculated with GRKN. No known nematode resistance gene suppressed GRKN infection, indicating that work must be done to protect crops from the eventual discovery of GRKN in Mississippi fields. Using the same resistance sources, tests were conducted to determine if the currently available resistances to RKN and RN offer any suppression of secondary infection of non-target nematode species for resistance. This is referred to as systemic acquired resistance, which is the induction of non-specific plant defense. Assays found that early inoculation with the nematode targeted by resistance did not effect infection by a secondary nematode species.

No description available.