Faecal Worm Egg Counts Research Articles

Genetic and environmental influences on faecal worm egg counts following natural infection in Barbari goats

Genetic and environmental influences on faecal worm egg counts following natural infection in Barbari goats

Supplementation of Acacia dealbata versus Acacia mearnsii leaf-meal has potential to maintain growth performance of lambs grazing low-quality communal rangelands in South Africa

Supplementing livestock grazing communal rangelands with leaf-meals from Acacia trees, which are currently considered as problematic invasive alien plants globally, may be a sustainable way of exploiting their desirable nutritional and anthelmintic properties. The current study evaluated worm burdens and growth performance of lambs grazing low-quality communal rangelands supplemented with leaf-meals prepared from the invasive alien plant species; Acacia mearnsii or A. dealbata. Forty, three-month-old ewe lambs weighing an average of 18.9 ± 0.60 kg were randomly allocated to four supplementary diets: (1) rangeland hay only (control), (2) commercial protein supplement plus rangeland hay, (3) A. mearnsii leaf-meal plus rangeland hay and (4) A. dealbata leaf-meal plus rangeland hay. All the supplementary diets were formulated to meet the lambs’ minimum maintenance requirements for protein. All the lambs were grazed on communal rangelands daily from 0800 to 1400 after which they were penned to allow them access to their respective supplementary diets until 08:00 the following morning. The respective supplementary diets were offered at the rate of 400 g ewe− 1 day− 1 for 60 days. Lambs fed the commercial protein supplement had the highest dry matter intake followed by those fed the Acacia leaf-meals and the control diet, respectively (P ≤ 0.05). Relative to the other supplementary diets, lambs fed the commercial protein supplement and A. dealbata leaf-meal had higher (P ≤ 0.05) final body weight and average daily gains. Dietary supplementation did not affect lamb faecal worm egg counts over the study period (P > 0.05). There was no association between supplementary diets and lamb FAMACHA© scores (P > 0.05). It was concluded that supplementation of Acacia dealbata versus Acacia mearnsii has the potential to emulate commercial protein in maintaining growth performance of lambs grazing communal rangelands in the dry season.

Field testing of recombinant subunit vaccines against Teladorsagia circumcincta in lambing ewes demonstrates a lack of efficacy in the face of a multi-species parasite challenge

IntroductionWe previously demonstrated efficacy of an 8-antigen recombinant subunit vaccine against a single species homologous Teladorsagia circumcincta challenge in lambs and in lambing ewes in pen trials. We subsequently demonstrated efficacy of a simplified, 2-antigen, version of this vaccine in lambs in pen trials. Here, we test both vaccines in lambing ewes in a field setting.MethodsIn the work presented here, 12 adjacent plots were seeded with a mixed infection of several common species of parasitic nematodes of sheep in temperate regions, including T. circumcincta. Ewes (n = 144), in groups of 12, grazed for 2 years on these plots and, in the first year, six of these groups of ewes were vaccinated with a 2-antigen prototype vaccine against T. circumcincta prior to mating and then again prior to lambing. In the following year these ewes were immunised again, this time with the 8-antigen prototype vaccine against T. circumcincta prior to mating and then prior to lambing. Throughout both seasons antigen-specific serum antibody levels in ewes and faecal worm egg counts (FEC) in ewes and their lambs were monitored, along with nematode species diversity at lambing.ResultsImmunised ewes produced elevated serum antibody levels to each of the vaccine antigens following immunisation but their FEC levels were not statistically significantly impacted by vaccination with either vaccine. FEC levels were also not impacted in lambs co-grazing the pastures with these immunised ewes. Nematode species diversity was not significantly impacted by vaccination in either year.DiscussionThe immunosuppressive effects of co-infecting gastrointestinal nematodes, the absence of vaccine cross-protection against co-infecting species and the influence of the periparturient relaxation in immunity probably all contributed to the inability of either vaccine to protect against T. circumcincta infection in field trials in the work presented here.

Putative SNPs in Ovar-DRB1 and GALNTL6 Genes Conferring Susceptibility to Natural Infection of Haemonchus Contortus in Southern Indian Sheep.

To explore associations between phenotypic traits and polymorphisms in the DRB1 and GALNT6 gene in Nellore, Deccani and Kenguri sheep naturally infected with Haemonchus contortus. Blood and faecal samples were collected to evaluate fecal worm egg counts (FEC), packed cell volume (PCV), hemoglobin (Hb), eosinophilia and for DNA isolation. Animals were grouped into susceptible and resistant groups based on EPG counts. FEC and circulating eosinophilia were higher in a susceptible group. Log FEC was negatively correlated (P < 0.01) with PCV, and Hb estimates. The second exon of DRB1 and intron variant of GALNTL6 genes were amplified from DNA samples of resistant and susceptible sheep. Characterization of Ovar-DRB1 amplicon by RFLP revealed two genotypes ('bb' and 'ab'). The genotype frequencies differed significantly between both groups (P < 0.05). The 'bb' genotypes had higher (P < 0.05) log FEC value than 'ab' genotypes and 'b' allele was linked with susceptibility to haemonchosis in sheep. The mean FEC of Nellore sheep was high indicating susceptibility of the breed and also in which the frequency of 'b' allele was more compared to the other two breeds. OVAR-DRB1 genotypes associated with FEC did not affect PCV and Hb. PCR-RFLP assay developed to determine the genotypes with respect to SNP rs424521894 of GALNTL6 revealed monomorphic nature at the locus in the breeds studied. MHC polymorphism could be used as a genetic marker for the selection of sheep resistant to H. contortus. However, a more intensive study, involving controlled infections and other GALNTL6 SNPs may be enforced to make any decisive assertion.

Haemato-biochemical responses, worm burdens and Haemonchus contortus ultrastructural changes in lambs fed diets containing graded inclusion levels of sericea lespedeza

Context Globally, sheep productivity is constrained by scarcity of high-quality feed and haemonchosis. These challenges may simultaneously be addressed by valorisation of nutraceutical forage legumes such as sericea lespedeza (SL) into sheep diets. Aim The current study determined the effects of feeding diets containing increasing inclusion levels of SL (0%, 6.25%, 12.5%, 18.75% and 25%) as replacement for lucerne on haematological, biochemical, and parasitological parameters in Haemonchus contortus-infected and non-infected lambs. Methods Bodyweights, body condition scores (BCS), FAMACHA© scores, faecal worm egg counts (FWEC), and haematological and biochemical parameters were recorded from 80 Dohne Merino intact male lambs assigned to diet-by-infection status-based treatments in a completely randomised design, with a 5 × 2 factorial arrangement of treatments comprising of eight lambs per treatment during a 42-day feeding trial. Adult worms were collected, enumerated, and their ultra-structure was evaluated using scanning electron microscopy after slaughter. Results Diet, and diet × infection status had no effects on red blood-cell parameters of the lambs (P &gt; 0.05). Eosinophils were affected by diet × infection status, being highest in non-infected lambs fed the control diet and lowest in infected lambs fed the 25% SL diet (P ≤ 0.05). Serum albumin, calcium and body condition scores declined (P ≤ 0.05) with increasing inclusion levels of SL in the diet. There was no influence of diet on lamb bodyweights, FAMACHA© scores, FWEC, and worm burdens. Dietary increments of SL disrupted the structural integrity of the head (χ2 = 28.43; ϕc = 0.493; P ≤ 0.05) of adult worms. Conclusions Sericea lespedeza may replace lucerne up to 25% in lamb feedlot diets, with minor negative effects on haematological and biochemical parameters, but offers little benefits for modulating Haemonchus contortus infection. Implications Beneficiation of biologically active alternative feed resources such as sericea lespedeza could help farmers adapt better to market changes through the development of enhanced livestock feed and pharmaceutical products, which could help alleviate losses associated with impoverished nutrition and gastrointestinal health of lambs.

Benchmarking Australian sheep parasite control: Changes in gastrointestinal nematode control practices reported from surveys between 2003 and 2019.

Cross-sectional surveys of sheep parasite control practices in Australia were conducted in 2004, 2012 and 2019 to document parasite problems, control practices and measure change over time. This article reports the results pertaining to gastrointestinal nematode infection; comparisons between years are mostly descriptive and not based on statistical inference. There was a general increase in the use of grazing management to prepare clean pastures for sheep to control gastrointestinal nematode infections with the largest increases in the use of: cropping, long acting anthelmintics to prepare clean pastures, feeding strategies, selecting rams for resistance to nematodes, and leaving some sheep untreated. The proportion of respondents using faecal worm egg count monitoring (WEC) and the number of WEC monitors per year were similar in 2003 (weaners: 3.0 WEC/year, adult ewes: 2.6 WEC/year) and 2018 (lambs and weaners and adult ewes both 3.1 WEC/year) but lower in 2011(lambs and weaners: 2.0 WEC/year, adult ewes: 2.9 WEC/year), whilst there was a higher number of anthelmintic treatments given in 2011 than 2003 and 2018 which were similar. There was an increase in the proportion of respondents carrying out WEC monitors themselves from 2011 (21%) to 2018 (30%) and a corresponding reduction in the use of private laboratories, government laboratories and veterinarians with regional differences in who carried out WECs. The top three anthelmintic groups used did not differ between the three survey years with macrocyclic lactones the most used followed by benzimidazoles (BZ) and levamisole (LEV) although the percentage of MLs used in 2011 and 2018 was lower than in 2003 with higher proportions of respondents using BZ and LEV groups in the latter two survey years. Moxidectin was in the most commonly used active in all survey years. There was an increase in the use of combination of anthelmintics from different groups, especially for a combination of three anthelmintics (2003: 4.4%, 2011: 19.1%, 2018: 21.5%), with lower use of single anthelmintics in 2011 (57.0%) and 2018 (55.4%) compared with 2003 (74.5%). The use of testing for anthelmintic resistance was generally low across the survey years with a lower proportion of respondents using tests in 2011 and 2018 than in 2003 (2003:48%, 2011: 29%, 2018: 37%). Time of year, results from WEC and seasonal weather condition were the most important factors when deciding when to apply anthelmintic treatment.

Autumn de-worming

Autumn is traditionally a time when most horses are de-wormed with one or more products that are effective against tapeworms and both adult and larval roundworms. However, the increasing prevalence of resistance and availability of diagnostics should prompt scrutiny of whether blanket de-worming at this time of year is appropriate. If management is good and horses are at low-risk of clinical disease, then there may be no need to use anthelmintics. Serology provides a means of assessing exposure to both cyathostomins and tapeworms, but it has its limitations and does not provide a validated means of assessing the risk of parasitic disease. The results of serology, results of faecal worm egg counts performed in the population through the preceding grazing season, and knowledge of management practices in the population should all be considered when assessing whether the risk of the disease to the individual is such that it must take priority over the ever-increasing threat of resistance in the equine population.

Changes in Serum Thiol-Disulphide Homeostasis in Sheep with Gastrointestinal Nematodes.

Simple SummaryParasitism with gastrointestinal nematodes represents a significant risk to the health of livestock populations. Besides the local oxidative damage caused by the parasite, the host reacts by increasing the production of oxidants. The study of thiol-disulphide homeostasis can be of help in the evaluation of the oxidative status of sheep during this type of parasitism. In this study, the thiol-disulphide homeostasis, together with other biomarkers of oxidative stress and inflammation, were assessed in the serum of lambs infected with gastrointestinal nematodes and were evaluated after 70 days of integrated crop-livestock system and anthelmintic treatment. This study showed that the thiol-disulphide balance was impaired in the infected lambs and the changes were correlated with the parasite load, which therefore could indicate their potential use as a tool to evaluate and monitor the disease in sheep.This work aimed to evaluate the thiol-disulphide homeostasis in serum of lambs naturally infected by gastrointestinal nematodes presenting different levels of parasite load indirectly indicated by faecal worm egg counts (EPG). Furthermore, the possible changes in the thiol-disulphide dynamic after different procedures to reduce the parasitic charge, such as the integrated crop-livestock system or anthelmintic treatment, were assessed. The results were compared with a panel of various oxidative stress and inflammatory biomarkers. The lambs were divided into three groups: animals highly infected (EPG higher than 5000) and packed cell volume (PCV) lower than 24% (G1); animals highly infected (EPG higher than 5000) and normal PCV (>24%) (G2); and animals presenting EPG lower than 5000 and normal PCV (>24%) (G3). The highly infected lambs (G1 and G2) showed lower total thiol (TT) and native thiol (SH) (p ≤ 0.01) than those from G3. After treatment, TT and SH increased significantly in all groups (p ≤ 0.01), and the disulphide (SS)/TT and SS/SH ratios decreased significantly (p < 0.01) in G1 and G2. These results show that the thiol-disulphide balance was impaired in lambs infected by gastrointestinal nematodes and that it could be potentially used as a biomarker to monitor this disease.

Kangaroos at maximum capacity: health assessment of free-ranging eastern grey kangaroos on a coastal headland

Sprawling urban development is fragmenting the landscape and native wildlife habitats on the Australian east coast. The impact of this rapid urbanization on wildlife health is largely unknown. This study surveyed the health of a high-density (5.4 individuals per ha) population of eastern grey kangaroos (Macropus giganteus) affected by urban encroachment and prolonged drought. Blood parameters (hematological and serum protein), trace element and heavy metal concentrations, and parasite counts (fecal worm egg counts, ticks, and mites) are reported for a sample of ≤ 54 kangaroos at Look at Me Now Headland, New South Wales, Australia. These parameters were compared to lower density kangaroo populations from other sites in New South Wales. We found the health and welfare of this population to be severely compromised, with nonregenerative anemia and nutritional deficiencies evident. Our results indicate that high-density kangaroo populations isolated by urban encroachment are at significant health risk. To prevent further decline in this population’s health, we discuss management strategies that could be employed, concurrent with ongoing health and disease monitoring, to mitigate the poor health outcomes in this population. We conclude that it is essential to retain habitat connectivity when altering land use in areas with resident kangaroo populations if managers are to maintain healthy populations.

A comparison of Mini-FLOTAC and McMaster techniques in detecting gastrointestinal parasites in West Africa Dwarf sheep and goats and crossbreed rabbits

ABSTRACT McMaster (McM) method is one of the most widely used techniques for the assessment of faecal parasites shedding in veterinary practices because of its simplicity. However, due to its light sensitivity, recently, the Mini-FLOTAC (MF) has been introduced as a possible alternative for faecal worm egg counts. This study aims to compare the diagnosis performance of MF to McM technique. Faecal samples from 40 animals randomly selected in sheep, goats and rabbits’ farms were collected and examined individually using MF and McM techniques. A statistical difference (p < 0.001) in strongylida egg counts in small ruminants and oocyst of Eimeria spp counts in rabbits using both techniques was observed. However, strongylida eggs per gram of feces in sheep (MF: 202.01 vs McM: 174.75) goat (MF: 147.36 vs McM: 143.75) and oocysts of Eimeria spp per gram of feces in rabbits (MF: 130.75 vs McM: 130.5) revealed no significant difference (p > 0.05). MF showed better diagnostic performance in term of the prevalence (MF: 32.5–100% vs McM: 7.5–70%) and the precision values (MF: 85.52–90.44% vs McM: 49.52–63.07%). This study demonstrated that MF appears to be the more reliable alternative technique for veterinary practices.

Conjunctival mucous membrane colour as an indicator for the targeted selective treatment of haemonchosis and of the general health status of peri-urban smallholder goats in southern Malawi

The world’s growing population is becoming increasingly centred around large cities, affording opportunities for peri-urban food production. Goats are well-suited to conversion of resources that are available in peri-urban settings into meat and occasionally milk. Haemonchus contortus has been described as “the nemesis of small ruminant production systems in tropical and subtropical regions”; hence control of haemonchosis through planned animal health management affords a pragmatic first step in improving the production efficiency of peri-urban goats. This study of peri-urban goat production investigated the potential value of targeted selective treatment of haemonchosis. 452 peri-urban goat keepers in southern Malawi were visited during three seasonal periods with relevance to the epidemiology of haemonchosis. 622, 599 and 455 individually identified goats were clinically examined during the dry season, the rainy season, and shortly after the end of the rainy season, respectively. Data were recorded for sex, age, weight, conjunctival mucous membrane colour score (FAMACHA©), body condition score (BCS) and faecal worm egg count (FEC); and where possible for pregnancy and lactation status. Animals with pale ocular mucous membranes were treated with 10 mg/kg albendazole, then re-examined 14 days later. Animals with pink mucous membranes, but FECs ≥250 eggs per gram were also re-examined and treated 14 days later. The results show high variability in growth rates deduced from the ages and bodyweights of each of 999 goats at the time of their enrolment. FAMACHA© scores alone were a poor index for the targeted selective treatment of haemonchosis, because they failed to identify too many animals that would have required treatment at different times of year and using different FAMACHA© and FEC cut-offs. Combining the indices of FAMACHA© scores ≥4, body condition scores ≥2, and age >18 months was more reliable in identifying those animals requiring treatment when different epidemiologically-relevant FEC thresholds for different seasons were taken into account. Inclusion of late pregnancy or early lactation status would have resulted in very few animals requiring treatment being missed. The use of conjunctival mucous membrane colour scoring in this way provided a valuable insight of the general health status of the peri-urban goats, to create opportunities for planned animal health management to improve productivity. The efficacy of albendazole treatment was poor, putatively due to drug resistance, or poor drug bioavailability in goats. In summary, our study shows opportunities for better production efficiency in peri-urban goats, and demonstrates the value of simple clinical diagnostic indices as decision support tools in planned animal health management.

Benchmarking Australian sheep parasite control practices: a national online survey

Context The third Australian national survey on control practices for internal and external parasites of sheep, following similar surveys in 2003 and 2011. Aims To document current parasite control practices and attitudes, measure change and to provide a benchmark against which to assess future practices and attitudes. Methods An online survey emailed to 6460 sheep producers, with a paper version supplied on request. A follow up short survey was conducted to assess non-response bias. Analysis by region and key sheep enterprise. Key results There were 354 and 250 useable responses to the main and short surveys respectively. Mean reported rainfall of 407 mm in 2018 was 27% lower than the average for respondents and &amp;gt;200 mm lower than mean reported rainfall in the previous surveys. The top three methods for worm control over the past 5 years were preventative treatments (74%), preparing clean pastures by spelling paddocks (62%) and treatment on the basis of faecal worm egg count (WEC, 54%). The proportion of respondents using WEC monitoring in 2018 was 40.4%, with a mean frequency of 3.1/year, and this was unaffected by sheep class. The frequency of anthelmintic treatment for ewes and lambs and weaners was 2.1/year. Of the respondents, 36.7% had performed an anthelmintic resistance test in the previous 5 years. The most popular flystrike control methods were timing of crutching (76.4%), preventative chemical treatment (75.9%), timing of shearing (63.1%), mulesing (46.8%) and genetic selection (46.4%). Pain relief was widely used for mulesing ewes (86.6%) and wethers (90.9%). Only 17.3% used Australian Sheep Breeding Values for traits in rams. Most respondents reported ‘evidence of lice’ in the past 5 years (55.8%) and had treated for lice off shears (50.1%), short wool (16.6%) or long wool (6.6%), with only 26.7% having not treated at all in the period. Web-based sources of information on parasite control have become increasingly important. Conclusions Notable changes since the earlier surveys were high rates of pain relief when mulesing, an increase in the use of Australian Sheep Breeding Values for parasite-related traits, an increase in WEC monitoring since 2011 and an increased use of web-based resources. Implications Parasite control remains important for sheep producers and continues to evolve with new drugs and approaches. The surveys highlight the effectiveness of extension networks and identify where more attention is required.

In vivo Anthelminthic Activity of Ethanolic Leaf Extract of Senna italica on Rats with Hymenolepis diminuta Infection

In spite of the effectiveness of most anthelmintic agents in use, there is still need to identify more due to their unwanted side effects. Hence, the need to develop more that can be safe for all, cheap and available even in our localities. In the light of the current need for the use of traditional plants in the treatment of parasitic diseases, we have assessed the anthelmintic effect of Senna italica and aimed to investigate the therapeutic activity on Hymenolepis diminuta infection. We described in vivo studies evaluating the anthelmintic effects of the leaf extract at different concentrations in a murine infection model. Phytochemical analysis of the plant extract has shown the chemical components available in the compound. There was a significant (p&lt;0.05) reduction in mean egg/gram (EPG) in one of the treatment groups which was observed to be similar to that of the treatment using conventional anthelmintic agent (Albendazole). A fluctuating but insignificant faecal worm-egg count was observed in the other experimental groups. The results obtained suggest a likelihood of its future use as an anthelmintic agent. Our next plan is to establish animal experiments with different types of helminth infection in order to have the full anthelmintic coverage by the agent, hopefully, before it will be validated for use as a human therapeutic agent.

Histopathological Studies on the Effects of Ethanolic Leaf Extract of Senna italica Treatment of Rats Infected with Hymenolepis diminuta

Helminths infections are among the major ailments affecting humans and livestock in many tropical and sub-tropical regions of the world which necessitates the current need for the use of traditional plants in the treatment of parasitic diseases.The aim of this study was to determine the pathological effects of Senna italica leaves extract on Hymenolepis diminuta infection. Plant leaf were collected and processed using cold maceration method. Phytochemical composition of the plant extract was determined. Rats were grouped into five groups of five rats each for the experiment. Albendazole was used for treatment at 7.5 mg/kg as positive control, while different concentrations of 75, 150, 300 and 0.0 mg/kg of the plant extracts were used for treatment of rats in the other groups. Daily worm-egg counts from all the rats for all the groups were recorded for up to 7 days post infection. Histopathology of tissues from representative rats from all groups was conducted to determine any visible change due to the treatments. The findings have shown a significant (p&lt;0.05) reduction in mean egg/gram (EPG) in positive control after three days. Rats in group 2 (75 mg/kg) showed a fluctuating faecal worm-egg count throughout the period of the study, with no significant difference observed. Rats in group 3 (150 mg/kg) showed a slightly decreased mean worm-egg count with no significant difference observed at P&lt;0.05. Rats treated with 300 mg/kg of the extract have shown significant decreased of worm-egg count within three days of the treatment (P&lt;0.05) which was observed to be similar to the treatment with Albendazole. Histopathological studies of intestine, liver and lung tissues of the infected and treated rats have shown that the plant extract has no significant histopathological effects. Leaves of Senna italica have therapeutic effect against Hymenolepis diminuta infection with no observed pathology in an experimental animal model.

Temporal changes in circulatory blood cell parameters of sheep genetically different for faecal worm egg count and diarrhoea from late summer to spring in a Mediterranean environment

Differences in haematology traits were investigated in worm-resistant and worm-susceptible Merino sheep that were genetically prone or less prone to developing diarrhoea in a winter rainfall region. The experiment was a 2 × 2 × 2 × 5 design. Male and female sheep aged 8–9 months old identified as having high (H) or low (L) breeding values for dags (breech soiling) and for worm egg counts (WEC) were allocated to one of four genetic groups: HH, HL, LH and LL (the first letter refers to dags and the second to WEC). The animals were sampled five times from autumn through winter to spring, in March, May, June (ewes only), July (rams only), August and in September after exposure to a natural paddock infection dominated by Trichostrongylus, Teladorsagia, Chabertia and Oesophagostomum. Measurements were packed cell volume, haemoglobin, red blood cell count, differential white cell counts, WEC and faecal consistency score. At all sampling times, there were large (P &amp;lt; 0.01) differences between groups within sex for both the faecal consistency score and WEC. The genetic effect for WEC was large (P &amp;lt; 0.01), as worm-susceptible sheep shed 10- (ewes) and 6-fold (rams) as many worm eggs at their WEC peak as the worm-resistant sheep at the end of the experiment. In the high-dag groups, the faecal consistency score was ~0.5 units higher for rams and 0.4 units higher for ewes, throughout the experiment. The optimum time to measure dags and WEC in this environment appears to be 6–8 weeks after the start of the winter rain. No differences were found among any of the treatment groups for any haematology trait. The haematogram changed significantly throughout the experiment, but genetic selection for low-dag score (reduced diarrhoea) or low WEC did not provide an acceptable discriminator in circulatory haematology traits between these genetically distinct groups of Merino sheep. It was concluded that circulatory haematology traits do not offer opportunities to select against diarrhoea or increased worm resistance in sheep.

Rotational grazing approaches reduces external and internal parasite loads in cattle

We tested whether holistic planned grazing (HPG) and four-camp grazing (FCG) rotational grazing approaches influence beef cattle parasites counts compared with continuous, season-long (SLG) grazing. We expected that parasite counts would increase linearly with increasing camp occupancy by cattle from 1 d (70-camp, HPG) to 21–28 d (four-camp, FCG) to 180 d (one-camp per season, SLG). Tick and faecal egg counts were observed across seasons on 30 steers raised on a private farm in Cedarville, South Africa. Tick species identified were Rhipicephalus evertsi evertsi, Rhipicephalus (Boophilus) decoloratus, Hyalomma spp. and Amblyomma hebreaum with respective prevalences of 32%, 29%, 20% and 19%. Unidentified roundworms had the highest faecal worm egg counts (81.2%) followed by Coccidia (16.4%), Nematodirus (1.2%) and strongyles (1.2%). Overall, prevalence and mean counts for ticks and faecal worm eggs were highest in the hot wet season, with the SLG having greater (P ≤ 0.05) values than either of the rotational approaches. However, increasing camp number and animal densities above four camps did not reduce (P > 0.05) parasite loads compared with HPG. Current results suggest that rotational grazing is a potential strategy to reduce livestock losses caused by high tick and worm loads in cattle, especially in the hot wet season.

First detection of ivermectin resistance in oesophagostomum dentatum in pigs

In 2016 suspected reduced ivermectin (IVM) efficacy in Oesophagostomum species in pigs was reported in England. Following this initial report, APHA raised awareness amongst private pig veterinary practitioners of the need to monitor the efficacy of the worm control on pig units. In 2017 another veterinary practitioner highlighted a potential in-field lack of IVM efficacy in treating Oesophagostomum species in sows on another breeder-finisher unit. In this trial, the efficacy of IVM against Oesophagostomum species worms has been investigated to determine whether suspected reduced efficacy (52% reduction in mean faecal egg count 14 days post ivermectin administration) on a mixed indoor and outdoor breeder-finisher pig farm in England reflected true IVM resistance under controlled experimental conditions. On days 0 and 40 of the trial, twenty helminth-naive pigs were artificially infected per os with 5000 Oesophagostomum L3 obtained from the farm under investigation. The pigs were allocated to treatment or control groups (n = 10 per group). Treatment group pigs received IVM (0.3 mg kg body weight) by sub-cutaneous injection as per manufacturer’s instructions on day 44. Control group animals were left untreated. Faecal worm egg counts were monitored throughout the trial from day 15 post infection to determine time to patency. On day 50 all pigs were euthanased to assess the worm burdens. Resistance to IVM was confirmed in Oesophagostomum dentatum based on the results of a faecal egg count reduction test (FECRT) and a controlled efficacy test (CET). Efficacy based on mean reduction in faecal egg count of IVM-treated pigs compared to untreated control pigs was 86%. Mean reduction in IVM-treated pig worm burdens was 5% against an adult worm population and 94% against an L3/L4 population. The apparent discrepancy between FECRT and CET efficacy results appears to be due to egg development and/or oviposition suppression in IVM-treated female worms. The detection of IVM resistance in Oesophagostomum species worms for the first time in UK pigs is particularly important considering the global situation where resistance to pyrantel, levamisole and benzimidazole anthelmintics in Oesophagostomum species in pigs have already been reported. The results also provide an opportunity to discuss the wider issue of anthelmintic usage and efficacy on pig farms and highlight the need for wider surveillance for the occurrence of anthelmintic resistance in pigs.

Heritabilities of IgA and IgE activities against Teladorsagia and Trichostrongylus L3 larval antigens correlated with traits for faecal worm egg count, health and productivity in Merino sheep

Low faecal worm-egg count (FEC) has been used as a phenotypic trait for breeding sheep for resistance to nematode infection. Application of this trait has resulted in a major reduction in worm-egg output in faeces, but in certain environments some of the resistant sheep develop what is believed to be a hypersensitivity-associated diarrhoea, resulting in soiling of the breech area (dags). To avoid breeding sheep with a propensity to scour, it, therefore, seems logical to combine selection for low FEC with selection for a trait based on the immune response to worm infection. We, therefore, investigated the relationships between immunoglobulin A (IgA) and immunoglobulin E (IgE) activities against L3 larval antigens of Teladorsagia circumcincta and Trichostrongylus colubriformis and measured their inheritance and their genetic relationships with FEC, dag traits and measures of production. Total plasma IgE concentrations were also determined and included in the study. We used 762 progeny from 23 Merino sires selected for resistance to helminths (the ‘Rylington Flock’) and to breech flystrike. Total plasma IgE and IgE activities against T. circumcincta were negatively correlated with liveweight, longissimus dorsi muscle depth, and fleece weight, but positively correlated with severity of dags, softer faeces and back-fat depth. The IgA activity against T. circumcincta was negatively correlated with liveweight and clean fleece weight, but positively correlated with back-fat depth and faecal consistency score. The IgA activity against T. colubriformis was not correlated with any measure, except the breeding value for dags around yearling age. The heritability for the IgA activity against T. circumcincta and T. colubriformis was 0.13 and 0.08 respectively. The heritability for both IgE activity against T. circumcincta and total plasma IgE concentration was 0.39. We conclude that it is feasible to combine FEC and dag traits with an immune trait (in this case, helminth-specific IgE activity and total plasma IgE concentration) and, thus, genetically select sheep for resistance to both helminths and diarrhoea. However, under natural worm-challenge conditions, blood sampling protocols need to developed, on the basis of animal age, season and environment, for optimum estimation of the immune trait and its relationships with other traits.

Expression of worm resistance in sheep selected for low worm-egg counts fed at maintenance or above-maintenance level

The present study reports on changes in faecal worm-egg counts (WEC), larval composition, and the number of worms at different developmental stages in young sheep sourced from a flock selected for reduced faecal worm-egg counts over 15 years. The sheep were individually penned and fed a maintenance (1.0 M) or a 1.5 times maintenance (1.5 M) diet over two periods, namely, worm-free and infection phases. They were dosed weekly with 10000 Trichostrongylus colubriformis and 10000 Teladorsagia circumcincta L3 infective larvae for 11 weeks. Sheep on the 1.5 M diet had lower WEC and higher bodyweights than did sheep on the 1.0 M diet. A significant decline in the percentage T. colubriformis occurred during the experiment, but no concomitant change in T. circumcincta was noticed. Resistant sheep had significantly (P &amp;lt; 0.001) fewer worms at necropsy, and also shed significantly (P &amp;lt; 0.001) fewer worm eggs during the experiment. Restricted feeding reduced bodyweight significantly (P &amp;lt; 0.001) and had a small but significant (P &amp;lt; 0.04) effect on the faecal worm-egg output and on the number of T. colubriformis worms (P &amp;lt; 0.01) in both the control and resistant sheep. The study showed that sheep selected for low WEC resulted in significantly (P &amp;lt; 0.001) lower WEC than in an unselected control line fed at a maintenance (1.0 M) and at an above-maintenance (1.5 M) level. Restricted feeding reduced bodyweight and had a small negative, and inconsistent, effect on the faecal worm-egg output in both the control and resistant lines.

Genetic parameters for faecal worm egg count at different ages in Australian sheep under natural challenge

The data used in the present study consisted of 24535 worm egg count records on sheep observed from 63 to 560 days of age under conditions of the natural challenge of trichostrongylid species. Records were extracted from the Information Nucleus Flock database of the Australia Sheep Cooperative Research Centre program from 2007 to 2011. Records were observed at various ages and subdivided into weaning (W, ~3 months), post-weaning (P, ~4 months), yearling (Y, ~12 months) and hogget (H, ~18 months) age stages and were used to investigate genetic variation at different age stages in univariate analyses and estimate genetic correlations between age stages in multi-trait analyses. The full data were also analysed by random regression models to study how heritability and genetic correlations varied with age. Heritability estimates from univariate analyses were 0.20 ± 0.05, 0.15 ± 0.02, 0.36 ± 0.09, 0.22 ± 0.06 for W, P, Y and H age stages respectively. A similar trend of heritability over ages was found from random regression analyses, which decreased from 0.16 at 90 days to 0.09 at 120 days, following a steady increase to 0.32 at ~410 days, and then decreased afterwards to 0.24 at 520 days. Strong genetic correlations (&amp;gt;0.8) were found between W and P age stages, along with Y and H age stages. Sire by flock interaction effects were significant, and accounted for the reduced estimates of heritability and increased genetic correlations between age stages. The results indicated that a multiple-trait approach is required for genetic evaluation of worm egg count when measurements are at different ages, and the accuracy of evaluations would benefit from recording at least two separate age stages.