Worm Control Research Articles

Estudo da atividade anti-helmíntica do extrato etanólico de Jatropha mollissima (Pohl) Baill. (Euphorbiaceae) sob Haemonchus contortus em ovinos no semiárido paraibano

Objetivou-se com o presente trabalho, avaliar o efeito anti-helmíntico de Jatropha mollissima por meio de experimentos in vitro e in vivo. Inicialmente foi investigada a concentração de extrato com efeito bioativo, pelo teste de evolução da toxicidade do extrato etanólico de J. mollissima sobre o microcrustáceo Artemia salina, obtendo uma CL50 de 660,80µg/ml, que foi testada em coproculturas contendo larvas infectantes de Haemonchus contortus e em animais para a verificação da redução do OPG. Para o teste in vivo o extrato foi dissolvido em água para se obter as concentrações 660,80µg/ml e 1321,6µg/ml, foram coletadas fezes semanalmente e sangue quinzenalmente. Como resultados dos testes in vitro, o extrato etanólico do caule de Jatropha mollissima mostrou-se tóxico sobre A. salina, com CL50 abaixo de 1000 µg/ml e inibiu a eclosão de ovos e o desenvolvimento de larvas de H. contortus, apresentando uma eficiência de 70,77%. O teste in vivo revelou que o extrato é também eficaz em ovinos, com redução significativa na contagem de OPG após 28 dias de experimento, 47 e 44% de redução nos grupos tratados com o extrato, 7,5% no grupo de animais não tratados e 40,6% com a ivermectina. Mesmo parasitados, os animais permaneceram clinicamente saudáveis e sem anemia. O extrato etanólico do caule de Jatropha mollissima pode representar uma alternativa ao controle da verminose ovina, pois retarda a resistência parasitária.

Anthelmintic resistance in ovine gastrointestinal nematodes in inland southern Queensland.

To establish the prevalence of anthelmintic resistance in ovine gastrointestinal nematodes in southern Queensland. An observational parasitological study using the faecal egg count reduction test. Sheep farms (n = 20) enrolled in this study met the twin criteria of using worm testing for drench decisions and having concerns about anthelmintic efficacy. On each farm, 105 sheep were randomly allocated to one of six treatment groups or an untreated control group. Faecal samples were collected on day 0 and days 10-14 for worm egg counts and larval differentiation. Single- and multi-combination anthelmintics, persistent and non-persistent, oral liquid or capsule, pour-on and injectable formulations were tested. Monepantel was not tested. Farmers also responded to a questionnaire on drenching practices. Haemonchus contortus was the predominant species. Efficacy <95% was recorded on 85% of farms for one or more anthelmintics and on 10% of farms for six anthelmintics. No resistance was identified on three farms. The 4-way combination product was efficacious (n = 4 farms). Napthalophos resistance was detected on one farm only. Resistance to levamisole (42% of farms), moxidectin injection (50% of farms) and the closantel/abamectin combination (67% of farms) was identified. Moxidectin oral was efficacious against Trichostrongylus colubriformis, which was predominant on only one farm. Of the farms tested, 55% ran meat breeds, 60% dosed more than the recommended dose rate and 70% always, mostly or when possible practised a 'drench and move' strategy. This level of anthelmintic resistance in southern Queensland will severely compromise worm control and force increased use of monepantel.

The parasitic phase of Ostertagia ostertagi: quantification of the main life history traits through systematic review and meta-analysis

Predictive models of parasite life cycles increase our understanding of how parasite epidemiology is influenced by global changes and can be used to support decisions for more targeted worm control. Estimates of parasite population dynamics are needed to parameterize such models. The aim of this study was to quantify the main life history traits of Ostertagia ostertagi, economically the most important nematode of cattle in temperate regions. The main parameters determining parasite density during the parasitic phase of O. ostertagi are (i) the larval establishment rate, (ii) hypobiosis rate, (iii) adult mortality and (iv) female fecundity (number of eggs laid per day per female). A systematic review was performed covering studies from 1962 to 2007, in which helminth-naïve calves were artificially infected with O. ostertagi. The database was further extended with results of unpublished trials conducted at the Laboratory for Parasitology of Ghent University, Belgium. Overall inverse variance weighted estimates were computed for each of the traits through random effects models. An average establishment rate (±S.E.) of 0.269±0.022 was calculated based on data of 27 studies (46 experiments). The establishment rate declined when infection dose increased and was lower in younger animals. An average proportion of larvae entering hypobiosis (±S.E.) of 0.041 (±0.009) was calculated based on 27 studies (54 experiments). The proportion of ingested larvae that went into hypobiosis was higher in animals that received concomitant infections with nematode species other than O. ostertagi (mixed infections). An average daily adult mortality (±S.E.) of 0.028 (±0.002) was computed based on data from 28 studies (70 experiments). Adult mortality was positively correlated with infection dose. A daily fecundity (±S.E.) of 284 (±45) eggs per female was found based on nine studies (10 experiments). The average female sex ratio of O. ostertagi based on individual animal data (n=75) from six different studies was estimated to be 0.55. We believe that this systematic review is the first to summarise the available data on the main life history traits of the parasitic phase of O. ostertagi. In conclusion, this meta-analysis provides novel estimates for the parameterization of life cycle-based transmission models, explicitly reports measures of variance around these estimates, gives evidence for density dependence of larval establishment and adult mortality, shows that host age affects larval establishment and, to our knowledge, provides the first evidence for O. ostertagi of a female-biased sex ratio.

Controlling endoparasites on equine stud farms

Resistance to all of the licensed classes of anthelmintics is now widespread and targeted worming strategies are advocated to reduce selection pressure and delay the onset of anthelmintic resistance. Targeted strategies of worm control are relatively straightforward in adult horses but where youngstock are present the situation becomes more complicated. Youngstock are more susceptible to infection and clinical disease and additional parasites have to be considered in control programmes. Despite the additional complexity, targeted worming strategies can be employed on breeding establishments, and indeed should be, as owners of young horses have the most to lose if anthelmintic resistance develops.

Avaliação da atividade anti-helmíntica de extratos brutos de plantas da Floresta Amazônica e Mata Atlântica brasileira sobre Haemonchus contortus

No mundo todo, as verminoses são causa de considerável prejuízo econômico na criação de ovinos. As perdas estão relacionadas ao retardo na produção, custos com tratamentos profiláticos e, em casos extremos, à morte dos animais. O objetivo deste trabalho foi verificar a ação anti-helmíntica de extratos vegetais sobre nematoides como alternativa terapêutica no tratamento da verminose em ovinos. Extratos orgânicos e aquosos foram obtidos de plantas nativas da Floresta Amazônica e Mata Atlântica, e foram testados na concentração de 100µg/mL em ensaios de toxicidade in vitro contra ovos de Haemonchus contortus e de 200µg/mL contra suas larvas. Na concentração estabelecida, apresentaram significante atividade relacionada à inibição de eclosão de ovos; em particular, o extrato orgânico de folhas e frutos de Trichilia sp. e o extrato aquoso dos órgãos aéreos de Phyllanthus attenuatus. Os resultados in vitro sugerem que extratos aquosos e orgânicos dessas plantas podem oferecer novas alternativas de controle da verminose em ovinos a partir de produtos naturais.

First Report of Helminth Parasites of Walia Ibex (&lt;em&gt;Capra walie&lt;/em&gt;) at Simen Mountains National Park, Natural World Heritage Site, Northern Ethiopia

Walia ibex (<em>Capra walie</em>) is critically endangered ungulate which is found in the Simen Mountains National Park (SMNP), northern Ethiopia. This study was conducted from February to August, 2011to determine the prevalence of helminth parasites of this animal. A total 167 faecal samples were collected and examined by floatation, sedimentation and Baermann techniques. The overall prevalence of helminth infection was 85.63% (143/167). Of this, 85.03% were nematodes and 7.18% cestodes. The eggs of trematode species (spp) were not encountered. The helminth parasites detected were strongyle spp. (78.44%), <em>Nematodirus</em> spp. (14.97%), Moniezia spp. (7.19%), <em>Strongyloides</em> spp. (5.39%), <em>Trichuris</em> spp. (4.19%), <em>Ascaris</em> spp (2.99%) and lungworms (26.35%). The genera of lungworms encountered were <em>Dictyocaulus</em>, <em>Muellerius</em> and <em>Protostrongylus</em>. Of all positive animals, 78.43% were infected with two or more type of parasites whereas 11.76% were harbouring only one parasitic species. The present results indicated that the infections caused by helminth pasites are significantly common in Walia ibex which necessitates further studies to design appropriate worm control strategies.

Beat resistance - a planned approach to worming

T he real and growing threat of worms becoming resistant to the chemical ingredients in wormers makes it extremely important to look at the bigger picture when it comes to effective and sustainable worm control. Last autumn, new legislation came in to play restricting the ways in which productspecific information on prescription-only animal medicines such as wormers can be communicated. This means it is now more important than ever to discuss a worming programme with a vet or a Suitably Qualified Person (SQP). With spring turnout onto new grass just around the corner, now is a key time plan the approach to worm control.

Spread and Control of Mobile Benign Worm Based on Two-Stage Repairing Mechanism

Both in traditional social network and in mobile network environment, the worm is a serious threat, and this threat is growing all the time. Mobile smartphones generally promote the development of mobile network. The traditional antivirus technologies have become powerless when facing mobile networks. The development of benign worms, especially active benign worms and passive benign worms, has become a new network security measure. In this paper, we focused on the spread of worm in mobile environment and proposed the benign worm control and repair mechanism. The control process of mobile benign worms is divided into two stages: the first stage is rapid repair control, which uses active benign worm to deal with malicious worm in the mobile network; when the network is relatively stable, it enters the second stage of postrepair and uses passive mode to optimize the environment for the purpose of controlling the mobile network. Considering whether the existence of benign worm, we simplified the model and analyzed the four situations. Finally, we use simulation to verify the model. This control mechanism for benign worm propagation is of guiding significance to control the network security.

English

Gastrointestinal nematodes are one of the rampant parasitic diseases constraining sheep farming in western Oromiya. A study aimed at assessing parasite control practices in use and to determine the efficacy of three brands of anthelmintics commonly used on the farms was conducted. Questionnaire survey and faecal egg count reduction tests (FECRT) were used to collect data. Majority of respondents (95.3%) indicated that anthelmintic treatment was the only method used to manage nematode infections in sheep. Many farmers (60.0%) followed prescription orders to determine dosage while others (40.0%) were reliant on visual appraisals. In most responses (38.7%) two treatments were given per year and more deworming can be done directed to animals exhibiting general syndromes such as emaciation, diarrhea and loss of production. Most of the treatments (49.3%) were performed on the farms by the owners. Efficacy tests showed a suspected resistance against albendazole by Haemonchus contortus and Trichostrongylus spp. whereas tetraclozan and ivermectin demonstrated high efficacy against all nematode genera isolated on the farms. Some worm control practices which are thought to enhance selection of resistant strains have been evident. These involved mainly risk of underdosing and continued use of one class of anthelmintics, irrespective of its efficacy status, which may accelerate selection dynamics. To preserve the efficacy of anthelmintics, targeted selective treatments traditionally practiced by farmers should be encouraged and supported by laboratory tests to identify animals in need of treatments. Anthelmintic efficacy evaluations should be part of the control strategies to monitor treatment failures in the study areas. Key words: Gastrointestinal nematode, parasite control, anthelmintic efficacy, questionnaire, horro sheep, Ethiopia.&nbsp

Sustainable worm control practices in South America

A high prevalence of nematodes, especially Haemonchus contortus and Trichostrongylus colubriformis, that exhibit multiple anthelmintics resistance has been reported in sheep in several South American countries. For this reason, the development of strategies that are less dependent on anthelmintic treatments is imperative for the prophylaxis of gastrointestinal nematode infections in small ruminants. Integrated grazing using cattle and sheep can be used for pasture decontamination with considerable reduction of H. contortus and T. colubriformis infective larvae after cattle grazing. Several breeds of sheep exhibit genetically related resistance against nematode infections, as is the case of “crioulo”, “native” or naturalised breeds of sheep. These breeds descend from livestock introduced by Portuguese and Spanish settlers and have been submitted to a long process of natural selection in various environmental conditions. In the South, the Crioula Lanada breed is more resistant to H. contortus than are Corriedale sheep. In tropical areas, where the minimum temperatures are usually higher than 20°C, hair sheep flourish, especially the Santa Ines breed, which also display a higher level of resistance to nematode infections compared with certain breeds of European origin. However, Santa Ines sheep have inferior carcass quality compared with other commercial breeds. Recent studies showed that the crossbreeding of Santa Ines ewes with sires of breeds with high potential for growth and meat production, results in crossbred animals with high productivity and a satisfactory degree of resistance against nematode infections. Several studies have indicated that improvement in nutrition has a beneficial effect on the development of resistance in lambs that were naturally or artificially infected with nematodes. Therefore, supplementary feeding and breeding strategies to improve resistance to nematodes are feasible options in the effort to reduce dependence on anthelmintic drugs to control worm infections in sheep.

Sustainable internal parasite control of sheep in Australia

Within Australia, sheep are managed under diverse conditions. Because of considerable differences between these areas, it is difficult to make universal recommendations about what constitutes a ‘sustainable’ worm control programme, although some broad principles apply. However, to be effective and profitable in the longer term programmes should cost-effectively prevent unacceptable production losses, but also avoid practices that encourage rapid selection for anthelmintic resistance. Recently, the practice of treating sheep with anthelmintics onto areas known to have low residual populations of worm larvae (low ‘refugia’) has been highlighted as a way of increasing selection for anthelmintic resistance. Consequently, a variety of strategies to increase refugia populations have been proposed. These strategies will vary considerably according to the patterns of infection, predominant parasites and distribution of rainfall in a given area, and key inputs to the farming system, such as the cost of labour.

Detection of benzimidazole resistance in gastrointestinal nematodes of sheep and goats of sub-Himalyan region of northern India using different tests

The present investigation was planned with the objective of studying the status of benzimidazole (BZ) resistance in gastrointestinal nematodes (GIN) of sheep and goats of different agro-climatic zones of sub-Himalyan region of northern India using in vivo faecal egg count reduction test (FECRT) and in vitro tests namely egg hatch assay (EHA) and larval development assay (LDA).Out of fourteen flocks, FECRT detected resistance in eight flocks (two sheep flocks and six goat flocks) with FECR% ranging from 54.95 to 90.86. Pre treatment coproculture contained predominantly Haemonchus contortus, followed by Trichostrongylus spp., Oesophagostomum and Strongyloides, while post treatment coproculture results showed that only H. contortus survived fenbendazole (FBZ) (in FECRT) or thiabendazole (TBZ) (in LDA) treatment except in three flocks of Tarai region {one sheep flock (Us1), and two goat flocks (Ug1 and Ug5)} where BZ resistant Trichostrongylus were also detected. The GIN of those eight farms which were found resistant by FECRT were also detected resistant by EHA. Arithmetic mean and range of ED50 value of susceptible group was found to be 0.059μg/ml and 0.037–0.096μg/ml, respectively, and the same for the resistant group were found to be 0.119μg/ml and 0.101–0.147μg/ml, respectively. With LDA, the arithmetic mean and range of LC50 value of susceptible group was found 0.0030μg/ml and 0.001–0.005μg/ml, respectively, and those of resistant group was found 0.0105μg/ml and 0.009–0.012μg/ml, respectively. The values of Spearman rank correlation coefficient indicated that negative correlation was found between FECR% and ED50 and between FECR% and LC50 while positive correlation existed between ED50 and LC50 value and the p-values indicated that these correlations were statistically highly significant. In the present study, FECRT and EHA gave comparable results with regard to detection of BZ resistance in GIN in sheep and goats. Although with LDA, the threshold LC50 value could not be established as for EHA but LDA indicated the presence of low level of resistance in GIN of both sheep and goats. For effective worm control, regular monitoring for anthelmintic resistance is important to know the status of anthelmintic efficacy in a particular agro-climatic zone. The baseline information thus generated will enable timely management of benzimidazoles resistance in GIN.

Considerations for control of helminths in stocker cattle

Many factors influence the spectrum and magnitude of helminth populations in stocker cattle. Calves are placed into stocker operations during all seasons, from all regions of the country, and with a broad range of prior parasite exposure and parasiticide treatment. This makes it unlikely that a generalized or generic parasite control program will be effective for all animals at receiving. Follow-up treatment recommendations are equally problematic, contingent upon the success of the treatment protocol utilized when cattle arrived at the stocker operation, residual activity of the anthelmintic(s) used at arrival, parasite challenge during the stocker phase, general animal health, and producer expectations. At the farm or ranch level, the more troublesome and conflicted considerations regarding parasite control are often ignored, and treatments are based on what appears to have worked in the past or the current cost of treatment options. This paper is not intended to make detailed recommendations about worm control, but is instead a discussion of factors at play in stocker cattle, including the species of the parasites, biology of the parasites, parasiticides, and the interaction and effect of these factors on the health and productivity of stocker cattle.

Epidemiology of parasitic gastroenteritis in beef suckler herds

Veterinary RecordVolume 172, Issue 18 p. 470-471 Research Epidemiology of parasitic gastroenteritis in beef suckler herds Andrew B. Forbes BVM&S, PhD, CBiol, MSB, DipEVPC, MRCVS, Corresponding Author Andrew B. Forbes...

Reduction in Greenhouse Gas Emissions Associated with Worm Control in Lambs

There are currently little or no data on the role of endemic disease control in reducing greenhouse gas (GHG) emissions from livestock. In the present study, we have used an Intergovernmental Panel on Climate Change (IPCC)-compliant model to calculate GHG emissions from naturally grazing lambs under four different anthelmintic drug treatment regimes over a 5-year study period. Treatments were either “monthly” (NST), “strategic” (SPT), “targeted” (TST) or based on “clinical signs” (MT). Commercial sheep farming practices were simulated, with lambs reaching a pre-selected target market weight (38 kg) removed from the analysis as they would no longer contribute to the GHG budget of the flock. Results showed there was a significant treatment effect over all years, with lambs in the MT group consistently taking longer to reach market weight, and an extra 10% emission of CO2e per kg of weight gain over the other treatments. There were no significant differences between the other three treatment strategies (NST, SPT and TST) in terms of production efficiency or cumulated GHG emissions over the experimental period. This study has shown that endemic disease control can contribute to a reduction in GHG emissions from animal agriculture and help reduce the carbon footprint of livestock farming.

Worms—A “license to kill”

Worm infections can cause severe harm and death to both humans and numerous domestic and wild animals. Despite the fact that there are many beneficial worm species, veterinarians, physicians and parasitologists have multiple reasons to combat parasitic worms. The pros and cons of various approaches for the discovery of new control methods are discussed, including novel anthelmintics, vaccines and genetic approaches to identify novel drug and vaccine targets. Currently, the mainstay of worm control remains chemotherapy and prophylaxis. The importance of knowledgeable and wise use of the available anthelmintics is highlighted.

Efeito do neem (Azadirachta Indica) no controle de nematódeos gastrintestinais em ovinos suplementados a pasto no período seco

The aim of this study was to evaluated the effect of Azadirachta indica (Neem) extracts upon the productive response and control of gastrointestinal nematodes in Santa Ines sheep during the dry season grazing. Twenty four sheep, were divided in three groups according to the following treatments: SP – Control (Animals receiving protein supplement); SP- Oil (Animals receiving protein supplement and Neem oil extract) and SP – Leaf (Animals receiving protein supplement and Neem dry leaves). The animals received daily protein supplement, while the oil and the dry leaves treatments were offered at interval of 15 days, a total of 4 doses ministred. Each day of supply of oil and leaves, feces samples were collected (day 0, 15, 30, 45, 60) for egg count per gram and subsequent larval cultivation for identifying genres. The protein supplement directly influenced the reduction of nematode eggs obtained per gram of feces (FEC) of sheep on quality grazing, consequently bringing benefits for the worms control. A indica present in the oil and leaves did not obtain any statistical difference between the treatments when compared to the animals receiving only protein supplement. The association of Neem derivatives with protein supplement have not been able to increase animal performance even after decreasing the rates of FEC, showing that protein supplement were more able to provide effects on internal parasites control, when compared with to Neem oil or Neem dry leaves treatments.

Investigation of sainfoin (Onobrychis viciifolia) cultivar differences on nitrogen balance and fecal egg count in artificially infected lambs1

Research in ruminant nutrition and helminth control with forages, which contain condensed tannins (CT), suggests that varying responses may depend not only on CT concentration but also on CT composition. An experiment was designed to test this by feeding 2 dried sainfoin cultivars (Visnovsky and Perly), which differed in CT properties, to lambs that were artificially infected with the abomasal blood-sucking nematode Haemonchus contortus. Twenty-four infected lambs received 1 of these 2 cultivars; the feeds were either untreated or treated with the CT-binding polyethylene glycol over 4 wk (n = 6). The 2 cultivars were also fed to 2 × 6 uninfected lambs. Nutrient digestibility, N balance, ADG, plasma urea, together with indicators of infection [fecal egg count (FEC), abomasal worm count, per capita female fecundity, erythrocytic indices, and serum protein], were determined. The specific effects of sainfoin cultivar, CT, and infection were evaluated by contrast analysis. Digestibility of both NDF and ADF were less (P < 0.001) with Perly compared with Visnovsky. The apparent nutrient digestibility was reduced (P < 0.001) by CT. However, no clear cultivar effects were evident on N excretion and retention. Condensed tannins reduced (P = 0.05) body N retention and shifted (P < 0.001) N excretion from urine to feces. Unlike cultivar and CT, infection decreased (P = 0.002) ADG. Plasma urea concentration was decreased (P = 0.007) in Perly- compared with Visnovsky-fed lambs and was decreased (P < 0.001) by CT. Plasma concentrations of essential and semiessential AA were increased (P < 0.001) by CT. The groups of infected lambs did not clearly differ in abomasal worm counts and erythrocytic indicators. In the last 2 to 3 wk of the experiment, FEC was decreased (P ≤ 0.01) when feeding CT. The lack of substantial cultivar effects suggests that the differences in CT properties may have been too small to result in nutritional and anthelmintic effects. The present results indicate that sainfoin CT had a mitigating effect on FEC and, consequently, pasture infectivity. However, the reduction was too small to expect any significant benefits in an Haemonchus-dominated system. Therefore, the use of sainfoin for controlling H. contortus should only be one component within an integrated worm control system.

Dung beetles (Coleoptera: Scarabaeoidea) in three landscapes in Mato Grosso do Sul, Brazil

Dung beetles (Coleoptera: Scarabaeoidea) in three landscapes in Mato Grosso do Sul, Brazil. Dung Beetles are important for biological control of intestinal worms and dipterans of economic importance to cattle, because they feed and breed in dung, killing parasites inside it. They are also very useful as bioindicators of species diversity in agricultural or natural environments. The aims of this paper were to study the species richness, and abundance of dung beetles, helping to answer the question: are there differences in the patterns of dung beetle diversity in three environments (pasture, agriculture and forest) in the municipality of Dourados, in the state of Mato Grosso do Sul. A total of 105 samplings were carried out weekly, from November 2005 to November 2007, using three pitfall traps in each environment. The traps were baited with fresh bovine dung, and 44,355 adult dung beetles from 54 species were captured: two from Hyborosidae and 52 from Scarabaeidae. Five species were constant, very abundant and dominant on the pasture, two in the agricultural environment, and two in the environment of Semideciduous forest. Most of the species were characterised as accessories, common and not-dominant. The species with higher abundance was Ataenius platensis Blanchard, 1844. The indexes of Shannon-Wiener diversity were: 2.90 in the pasture, 2.84 in the agricultural environment and 2.66 in the area of native forest. The medium positive presence of dung beetles in the traps in each environment were: 36.88, 42.73 and 20.18 individuals per trap, in the pasture, agricultural environment and in the native forest, respectively. The pasture environment presented a higher diversity index. The species diversity of dung beetles was superior where there was higher abundance and regularity of resource (bovine dung).

Grazing systems and worm control in sheep: a long-term case study involving three management systems with analysis of factors influencing faecal worm egg count

Managing infections of sheep with gastrointestinal nematode parasites (worms) and problems of resistance to anthelmintic treatments continue to be major challenges for graziers on the Northern Tablelands of New South Wales, Australia. The whole-farmlet study of grazing enterprises undertaken by the Cicerone Project tested the broad hypotheses that compared with typical management (farmlet B), internal parasites can be more effectively managed with improved nutrition (farmlet A) or by intensive rotational grazing (farmlet C). Further aims were to identify the major sources of variation in faecal worm egg count (WEC) over the 6-year period and to examine the efficacy of the various anthelmintic treatments used during the experiment. This paper describes the management of sheep worms at the whole-farmlet level during the experiment, and analyses data from the routine WEC monitoring (5644 records) and larval differentiation tests (322 records) carried out on behalf of the Cicerone Management Board and by a doctoral candidate. It complements more detailed investigations published elsewhere. Over the period from July 2000 to December 2006, worm infections in ewes, lambs, hoggets and wethers were, with some exceptions, successfully controlled on the farmlets through a combination of regular monitoring of WEC, treatment with a wide array of anthelmintics and grazing management. Farmlet C had lower mean WEC (444 epg) and annual anthelmintic treatment frequency (3.1 treatments/year) over the whole experimental period than farmlets B (1122 epg, 4.3 treatments/year) or A (1374 epg, 4.7 treatments/year). The main factors influencing WEC were the time since the last anthelmintic treatment, and the anthelmintic used at that treatment. The magnitude of these effects dwarfed those of climatic and management factors that might be expected to influence the epidemiology of gastrointestinal nematode infections via environmental or host-mediated mechanisms. Nevertheless management factors associated with stocking rate and grazed proportion (proportion of each farmlet grazed at any one time), and climatic indicators of both temperature and moisture availability had significant effects on WEC. The results show that, in a region with Haemonchus contortus as the major sheep nematode, improved host nutrition in a higher input system (farmlet A) did not provide more effective control of gastrointestinal nematodes than typical management (farmlet B); however, it was observed that gastrointestinal nematode control was no worse on farmlet A than on farmlet B in spite of farmlet A supporting a 48% higher stocking rate by later in the trial period (2005). The study provided strong support for the proposition that intensive rotational grazing (farmlet C) provides more effective control of gastrointestinal nematodes than typical management (farmlet B) as evidenced by significantly lower WEC counts and anthelmintic treatment frequency. Tactical worm control based on routine monitoring of WEC provided adequate control of worms on all three farmlets for much of the experimental period but failed to prevent significant spikes in WEC to values associated with significant production loss on multiple occasions, and significant ewe mortality on farmlets A and B on one occasion.