Anthelmintic resistance impact on tropical beef cattle productivity: effect on weight gain of weaned calves

An alkaloidal fraction of Annona tomentosa possesses anthelmintic activity and induces surface modifications in Haemonchus contortus

The nematode Haemonchus contortus is, as a parasite, responsible for most mortality of small ruminants, causing significant economic losses. Numerous plant-derived compounds have exhibited promising anthelmintic activities against this nematode. Notably, the Annona genus stands out for demonstrated anthelmintic effects by extracts from several of its species against different nematodes. This study aimed to assess the effect of an Annona tomentosa fraction, rich in alkaloids, on H. contortus. This fraction, named Alk.F, is derived from the methanolic extract of the plant's stem bark. Chemical characterization of Alk.F was performed by liquid chromatography coupled with mass spectrometry. Among the nine predominant peaks obtained, seven alkaloids were identified: reticuline, reticuline N-oxide, reticuline N-oxide isomer, cyclanoline, asimilobine, tetrahydropalmatine and anonaine. Alk.F inhibited the larval development of H. contortus with an IC50 of 0.026 mg/mL, inhibited larval exsheathment with an IC50 of 0.38 mg/mL, and displayed low hemolytic activity towards sheep erythrocytes. Furthermore, atomic force microscopy revealed that Alk.F altered adhesive forces and the height profile on the surface of H. contortus larvae. In conclusion, A. tomentosa alkaloids alter the cuticle structure of H. contortus, inhibiting larval development and exsheathment, thus offering possibilities for contributing to the development of new anthelmintic drugs.

Biomarkers of gastrointestinal nematodes in beef cattle raised in a tropical area

Biomarkers are specific molecular, histological, or physiological characteristics of normal or pathogenic biological processes and are promising in the diagnosis of gastrointestinal nematodes (GINs). Although some biomarkers have been validated for infection by Ostertagia sp. in cattle raised in temperate regions, there is a lack of information for tropical regions. The aim of this project was to assess potential biomarkers and validate the most promising. In the first study, 36 bovines (Nelore breed) naturally infected by GINs were distributed into two groups: infected (not treated with anthelmintic) and treated (treated with fenbendazole on days 0, 7, 14, 21, 28, 42, and 56). The variables of interest were live weight, fecal egg count, hemogram, serum biochemical markers, phosphorus, gastrin, and pepsinogen. In the second step, pepsinogen was assessed in cattle of the Nelore breed distributed among three groups: infected (not treated with anthelmintic), MOX (treated with moxidectin), and IVM + BZD (treated with ivermectin + albendazole). In the first study, no difference between groups was found for weight, albumin, hematocrit (corpuscular volume [CV]), erythrocytes, or hemoglobin. Negative correlations were found between pepsinogen and both CV and albumin, and albumin was negatively correlated with the percentage of Haemonchus sp. in the fecal culture. Among the biomarkers, only pepsinogen differentiated treated and infected (beginning with the 28th day of the study). In the second study, a reduction in pepsinogen was found after anthelmintic treatment. Therefore, pepsinogen is a promising biomarker of worms in cattle naturally infected by the genera Haemonchus and Cooperia in tropical areas.

The Economic Impact of Parasitism from Nematodes, Trematodes and Ticks on Beef Cattle Production

Global human population growth requires the consumption of more meat such as beef to meet human needs for protein intake. Cattle parasites are a constant and serious threat to the development of the beef cattle industry. Studies have shown that parasites not only reduce the performance of beef cattle, but also negatively affect the profitability of beef agriculture and have many other impacts, including contributing to the production of greenhouse gases. In addition, some zoonotic parasitic diseases may also threaten human health. Therefore, ongoing cattle parasite research is crucial for continual parasite control and the development of the beef cattle industry. Parasitism challenges profitable beef production by reducing feed efficiency, immune function, reproductive efficiency, liveweight, milk yield, calf yield and carcass weight, and leads to liver condemnations and disease transmission. Globally, beef cattle producers incur billions (US$) in losses due to parasitism annually, with gastrointestinal nematodes (GIN) and cattle ticks causing the greatest economic impact. The enormity of losses justifies parasitic control measures to protect profits and improve animal welfare. Geographical differences in production environment, management practices, climate, cattle age and genotype, parasite epidemiology and susceptibility to chemotherapies necessitate control methods customized for each farm. Appropriate use of anthelmintics, endectocides and acaricides have widely been shown to result in net positive return on investment. Implementing strategic parasite control measures, with thorough knowledge of parasite risk, prevalence, parasiticide resistance profiles and prices can result in positive economic returns for beef cattle farmers in all sectors.

Integration of ITS-2 rDNA nemabiome metabarcoding with Fecal Egg Count Reduction Testing (FECRT) reveals ivermectin resistance in multiple gastrointestinal nematode species, including hypobiotic Ostertagia ostertagi, in western Canadian beef cattle

A large-scale Fecal Egg Count Reduction Test (FECRT) was integrated with ITS-2 rDNA nemabiome metabarcoding to investigate anthelmintic resistance in gastrointestinal nematode (GIN) parasites in western Canadian beef cattle. The study was designed to detect anthelmintic resistance with the low fecal egg counts that typically occur in cattle in northern temperate regions. Two hundred and thirty-four auction market-derived, fall-weaned steer calves coming off pasture were randomized into three groups in feedlot pens: an untreated control group, an injectable ivermectin treatment group, and an injectable ivermectin/oral fenbendazole combination treatment group. Each group was divided into six replicate pens with 13 calves per pen. Individual fecal samples were taken pre-treatment, day 14 post-treatment, and at monthly intervals for six months for strongyle egg counting and metabarcoding. Ivermectin treatment resulted in an 82.4% mean strongyle-type fecal egg count reduction (95% CI 67.8-90.4) at 14 days post-treatment, while the combination treatment was 100% effective, confirming the existence of ivermectin-resistant GIN. Nemabiome metabarcoding of third-stage larvae from coprocultures revealed an increase in the relative abundance of Cooperia oncophora, Cooperia punctata, and Haemonchus placei at 14 days post-ivermectin treatment indicating ivermectin resistance in adult worms. In contrast, Ostertagia ostertagi third-stage larvae were almost completely absent from day 14 coprocultures, indicating that adult worms of this species were not ivermectin resistant. However, there was a recrudescence of O. ostertagi third stage larvae in coprocultures at three to six months post-ivermectin treatment, which indicated ivermectin resistance in hypobiotic larvae. The calves were recruited from the auction market and, therefore, derived from multiple sources in western Canada, suggesting that ivermectin-resistant parasites, including hypobiotic O. ostertagi larvae, are likely widespread in western Canadian beef herds. This work demonstrates the value of integrating ITS-2 rDNA metabarcoding with the FECRT to enhance anthelmintic resistance detection and provide GIN species- and stage-specific information.

Cost-benefit ratio of anthelmintic treatment and its comparative efficacy in commercial dairy farms

Intestinal parasitic infection is one of the major challenges in obtaining optimal production and maintaining the health and welfare of all animals including cattle and buffaloes. Anti-parasitic treatments appear to be a reliable countermeasure. However, the effectiveness and selection of suitable anthelmintics require situational assessments in a given locality. In the current study, the efficacy and impact of benzimidazole (albendazole) were assessed in a total of 400 (100 each) on the performance of buffaloes, buffalo-heifer, cattle, and cattle-heifers at two commercial dairy farms in the Province of Punjab, Pakistan. Additionally, the cost-benefit ratio was calculated by assessing the inputs (medication, feed, and labor cost) and outputs (milk and weight gain). The qualitative and quantitative examination of helminth eggs in each type of animal indicated a prevalence of 73.3, 78.3, 76.6, and 85.0% in cattle, cattle-heifers, buffaloes, and buffaloes-heifers, respectively. Specifically, a highest rate (10.0-13.3%) of Haemonchus sp. infection was only observed in cattle and heifers, while Fasciola sp. infections (10.0-11.6%) were the most often found species in buffaloes and heifers. The highest anthelmintic impacts (egg per gram of feces, p < 0.001) were observed on day 14 post-medication. Until 60 days of post-anthelmintic treatment, an average increase of 0.8 and 0.7 L in milk production per day in cattle and buffaloes, respectively while a total of 11.45 and 9.45 kg body weight were noticed in cattle-heifer and buffaloes-heifer, respectively. Cumulative cost-benefit analysis indicated a positive correlation between treated and non-treated animals. These findings reiterate the importance of anthelmintic drugs in reducing the impacts of parasites on the productivity, health, and well-being of an animal under high infection challenges.

Haemonchus contortus Parasitism in Intensively Managed Cross-Limousin Beef Calves: Effects on Feed Conversion and Carcass Characteristics and Potential Associations with Climatic Conditions

The objectives of the study were: (a) to study the effect of Haemonchus spp. on the growth performance characteristics of fattening calves, (b) to assess any potential effects on carcass characteristics and (c) to investigate the potential role of climatic conditions in the process of the infection. The study was conducted for 201 days in an intensively managed cross-Limousin herd. The animals were divided into two equal groups: those receiving anthelmintic treatment (AT) and the untreated (C) controls. The same nutritional regime was applied to both groups and the feed consumption was calculated daily. Standard parasitological examinations were performed at weekly intervals. At slaughter, carcasses were weighed and assessed for conformation and fat cover classes. Climatic variables were obtained for the location of the farm and a temperature-humidity index was calculated. Before anthelmintic treatment with ivermectin, there was no difference in parasitic burdens between the two groups: 544 (AT) vs. 554 (C) epg, whilst after it, counts were 0 and 450–700 epg, respectively, with over 96% of larvae identified as Haemonchus spp. and, later, confirmed as Haemonchus contortus. It was concluded that treated animals had a higher average total bodyweight gain, higher feed conversion ratio and carcass yield of superior quality than controls. There was a difference between the two groups in the pattern of reduction of dry matter intake as the temperature-humidity index increased.

Structure-based in silico design and in vitro acaricidal activity assessment of Acacia nilotica and Psidium guajava extracts against Sarcoptes scabiei var. cuniculi

Infestation by Sarcoptes scabiei var. cuniculi mite causes scabies in humans and mange in animals. Alternative methods for developing environmentally friendly and effective plant-based acaricides are now a priority. The purpose of this research was the in silico design and in vitro evaluation of the efficacy of ethanol extracts of Acacia nilotica and Psidium guajava plant leaves against S. scabiei. Chem-Draw ultra-software (v. 12.0.2.1076.2010) was used to draw 36 distinct compounds from these plants that were employed as ligands in docking tests against S. scabiei Aspartic protease (SsAP). With docking scores of - 6.50993 and - 6.16359, respectively, clionasterol (PubChem CID 457801) and mangiferin (PubChem CID 5281647) from A. nilotica inhibited the targeted protein SsAP, while only beta-sitosterol (PubChem CID 222284) from P. guajava interacted with the SsAP active site with a docking score of - 6.20532. Mortality in contact bioassay at concentrations of 0.25, 0.5, 1.0, and 2.0 g/ml was determined to calculate median lethal time (LT₅₀) and median lethal concentration (LC₅₀) values. Acacia nilotica extract had an LC₅₀ value of 0.218 g/ml compared to P. guajava extract, which had an LC₅₀ value of 0.829 g/ml at 6 h. These results suggest that A. nilotica extract is more effective in killing mites, and these plants may have novel acaricidal properties against S. scabiei. Further research should focus on A. nilotica as a potential substitute for clinically available acaricides against resistant mites.

Macrocyclic lactone resistance in nematodes of cattle in Brazil: Blame it to the ticks!

Strategic helminth control in adult cattle would hardly impose sufficient selection pressure to parasite populations but reports of resistance against macrocyclic lactone (ML) based-products have been confirmed worldwide. The objective of this study was to evaluate the scientific literature of ML resistance (< 90.0% efficiency) in helminths of cattle from 2001 (the first report) to 2020 in Brazil. Additional to the data, we studied the correlation of parasite control practices based on a questionnaire given to 32 farmers. The search returned 246 reports and 21 full articles were selected. From these, a Wordcloud and a Keyword Co-occurrence Network graph were created. The published data revealed that most of the studies (19/21) reported multi-species (Cooperia spp., Haemonchus sp., Oesophagostomum radiatum, Trichostrongylus sp.) resistance to ML. None of the reports described the treatment frequency in the tested farms. As for the questionnaire, the majority of farmers (> 70.0%) responded that they rotate products after treatment, animals are treated monthly or biweekly (58.0%), treatments are based on visual evaluation (coat condition, ectoparasite infestation), and that in 94.0% of the times farmers treat all animals. Moreover, farmers use ML in association with potent acaricides (cypermethrin, chlorpyriphos, fluazuron) in more than 90.0% of the times (15/16). It was observed that this regimen was used to prevent and control the cattle-tick Rhipicephalus microplus (90.0%) and the horn-fly, Haematobia irritans (30.0%) infestations. We conclude that the most important factor for nematode resistance was the high level of ML exposure of up to 16 times/year, in combination with acaricides to control ticks and to a lesser extent to control horn-flies. Therefore, selection of helminth populations in cattle in Brazil can be considered secondary to ectoparasite control. The present analysis is critical, as one the most widespread recommendations to avoid drug resistance is to reduce the use of long-acting compounds, due to their extended persistent periods, increasing parasite selection. Moreover, a more serious attitude must be taken regarding parasite control strategies for livestock, reinforcing that health protocols should be based on single acaricidal products whenever possible. Complementary, selective evaluations based on transient threshold population abundance must be enforced to reduce treatment frequency, reducing parasite selection and animal distress.

Moxidectin: A Viable Alternative for the Control of Ivermectin-Resistant Gastrointestinal Nematodes in Beef Cattle

The increasing prevalence of anthelmintic resistance in cattle especially for avermectins, is a challenge for controlling parasites in some herds. Thus, field studies demonstrating the increase in productivity by the use of anthelmintic formulations, even when a suboptimal treatment (efficacy below 95%), can contribute to the development of gastrointestinal nematodes control programs in beef cattle. The objective of the present study was to evaluate the anthelmintic efficacy and productive performance in pasture-raised beef calves, treated with macrocyclic lactones. A Split plot in time randomized block design was used to assess weight gain and reduction in fecal egg count (FECs) of treatments: 1% moxidectin (1% MOX), ivermectin (IVM) and abamectin (ABM) (2.25% IVM+1.25% ABM), 4% IVM, 3.15% IVM and placebo. For the evaluation of FECs and weight gain of the animals, individual samples were collected seven days before treatment and, +14, +30, +56, +91 and +118 days post-treatment (DPT). The efficacies in the 14th DPT were: 72.3% (1% MOX), 22.1% (4% IVM), 22% (2.25% IVM + 1.25% ABM) and 0% (3.15% ivermectin). 1% MOX was the only treatment that resulted in a significant increase in weight gain of the animals compared to the placebo group after 118 days of treatment, with a difference of 7.6 kg. Therefore, MOX remains a viable alternative for the control of helminths resistant to avermectins and still capable of resulting in significant productive gains, even with an efficacy below 95%.

Anthelmintic resistance in ruminants: challenges and solutions

Anthelmintic resistance (AR) is a growing concern for effective parasite control in farmed ruminants globally. Combatting AR will require intensified and integrated research efforts in the development of innovative diagnostic tests to detect helminth infections and AR, sustainable anthelmintic treatment strategies and the development of complementary control approaches such as vaccination and plant-based control. It will also require a better understanding of socio-economic drivers of anthelmintic treatment decisions, in order to support a behavioural shift and develop targeted communication strategies that promote the uptake of evidence-based sustainable solutions. Here, we review the state-of-the-art in these different fields of research activity related to AR in helminths of livestock ruminants in Europe and beyond. We conclude that in the advent of new challenges and solutions emerging from continuing spread of AR and intensified research efforts, respectively, there is a strong need for transnational multi-actor initiatives. These should involve all key stakeholders to develop indicators of infection and sustainable control, set targets and promote good practices to achieve them.

Effect of antihelminths with contrasting efficacy against gastrointestinal nematodes on the live-weight gain of young Nellore cattle

We estimated the losses caused by gastrointestinal nematode (GIN) infections in young Nellore cattle born in three consecutive calving seasons (Cycles I, II and III). Three groups of animals: Group 1 - free from GIN using 2.5 mg/kg of albendazole sulfoxide; Group II - free from Oesophagosomum radiatum using 0.2 mg/kg of ivermectin but infected with ivermectin-resistant Haemonchus placei and Cooperia spp.; and Group III - non-treated experimental control animals, infected with all GIN, were observed over a period of 12 months. Male and female calves were evaluated starting before weaning when the animals were an average of approximately four months of age. In Cycle I, only females were evaluated. All the animals continued to graze on pastures of Urochloa spp. (= Brachiaria). All the groups showed median faecal egg counts of fewer than 250 eggs per gram (EPG), and no clinical signs of parasitic gastroenteritis were observed. The blood variables were within the normal ranges, and no calf presented anaemia. In most of the samplings, the median EPGs were significantly lower (P < 0.05) in the group treated with albendazole. Throughout the experiment, the most prevalent parasite observed in the control group was Cooperia spp., followed in decreasing order by Haemonchus spp., O. radiatum and Trichostrongylus spp. All the groups of calves exhibited weight gain throughout the trials with control group displaying the lowest body weight gain. Body weight variables between the albendazole- and ivermectin-treated groups were not significantly different (P > 0.05). After weaning, females animals in albendazole and ivermectin treated groups exhibited higher body weights, 20.4% and 22.7%, respectively, than those of the control group. Likewise, males treated with albendazole and ivermectin exhibited 27.6% and 25.8%, respectively, more body weight gain than animals under control group. Because the main difference between the ivermectin and the control groups was the O. radiatum parasitism, most of the losses in the control group were possibly due to this nematode species. Nevertheless, the other nematodes species that occurred in relatively high intensities in control group could also have an additive effect in such losses.

Analysis of the immunomodulatory activity of excreted and secreted products from Haemonchus placei transition infective larvae (xL3)

The excretory/secretory (E/S) products released by infective transitory larvae (xL₃) of Haemonchus placei have an important biological function in stimulating immune mechanisms during the invasive process. Our objective was to analyse the modulatory activity of 15 and 70 kDa E/S products from H. placei xL₃. Both E/S products were collected from xL₃in vitro cultures at 24 and 72 h. Proteins were confirmed by SDS-PAGE, and the corresponding spots were elicited by gel isoelectrofocusing (IEF) and characterised by mass spectrometry. Additionally, flow cytometry of CD4⁺/γδ⁺ T cells and immune gene expression were performed by proliferation assays using each E/S product to stimulate lymphocyte and peripheral blood mononuclear cells (PBMCs) from non-infected calves. The IEF results displayed two spots of 7.0 and 5.7 pI for the 15 and 70 kDa products, respectively. Additionally, 29 and 17 peptides from the 15 and 70 kDa E/S products, respectively, were identified with the hypothetical neurotransmitter and enzymatic functions necessary for larval development. The relative expression displayed upregulation of IL4, 5, 6, 8, 10, 13, IFNγ, and FCεR1A genes (from 2.0- to 17.6-fold, p < 0.05) stimulated by the 15 and 70 kDa proteins, indicating specific genes against haemonchosis. Although the percentage of median florescence intensity (MFI%) of CD4⁺/γδ⁺ T cells did not change for both E/S products compared to the negative control and concanavalin-A stimulated cells as the positive control (p > 0.05), the 15-kDa protein reduced the levels of both T cells, and the 70-kDa proteins increased the γδ⁺ cells slightly. Additionally, there was increased PBMCs proliferation by the 70 kDa proteins (p < 0.05), denoting the biological role of other immune cells. The 15 and 70 kDa protein E/S products from H. placei xL₃ showed modulation of the immune response, and although more studies are required, they indicate important functions in the host/parasite interaction.

Haemonchus sp. in beef cattle in Brazil: species composition and frequency of benzimidazole resistance alleles

The aim of the present study was to investigate the occurrence of Haemonchus contortus and Haemonchus placei in beef cattle and the frequency of single nucleotide polymorphisms associated with benzimidazole (BZ)-resistance in Haemonchus spp. in Brazil. For such, fecal samples were collected from 61 beef cattle ranches in 11 Brazilian states. Third-stage larvae (L3) were produced for morphological species identification and DNA extraction. PCR was performed for the analysis of the isotype 1 β-tubulin gene and the products were sequenced to confirm the presence of H. placei and H. contortus. For each field population, pyrosequencing assays were performed to quantify the frequency of the F167Y, E198A and F200Y polymorphisms in the isotype-1 β-tubulin gene. The results of the morphometric analysis of 2345 larvae showed that H. placei was present on all ranches. The analysis of the isotype 1 β-tubulin gene confirmed 100% prevalence for H. placei and 23.7% for H. contortus. Pyrosequencing assays demonstrated single-nucleotide polymorphisms (SNPs) associated with BZ-resistance in all three codons (F167Y, E198A and F200Y) of the isotype 1 β-tubulin gene in H. placei field populations. Frequencies of resistance-associated alleles above background (≥ 15%) were found for at least one codon in 11.4% of the field isolates and maximum frequencies of 30, 21 and 29% were found for codons 167, 198 and 200, respectively, on individual ranches. This study confirms the presence of H. contortus in beef cattle in the major livestock farming states in Brazil and demonstrates that genotypes associated with BZ resistance are present in field populations of Haemonchus spp..

Gastrointestinal nematode infections do not hinder the development of Simmental X Nellore crossbred calves raised with a nutritionally enhanced diet

An evaluation was made of the effect of anthelmintic treatments on the performance of Simmental X Nellore crossbred calves before and after weaning. To this end, the calves were divided into three groups: (1) treated monthly with a low efficacy anthelmintic drug, ivermectin; (2) treated monthly with a highly effective anthelmintic drug, albendazole; and (3) untreated control group. All the groups in this experiment showed an average fecal egg count of less than 400 eggs per gram (EPG), and no clinical signs of parasitic gastroenteritis. The blood variables were within the normal range and no calf presented anemia. In most of the samplings, mean EPGs were significantly lower (P<0.05) in the group treated with albendazole. The calves received dietary supplementation before and after weaning, which enabled them to gain weight in every month of the experiment and reach a body weight of about 250 kg on the last sampling date, before turning one year old. The anthelmintic treatments did not affect body weight gain, leading to the conclusion that, when fed with suitable dietary supplements, Simmental X Nellore crossbred calves are not affected by gastrointestinal nematode parasites acquired by grazing.

Effects of long-term indiscriminate use of macrocyclic lactones in cattle: Parasite resistance, clinical helminthosis, and production losses

Our aims were to describe a case of clinical helminthosis caused by parasite resistance to macrocyclic lactones (MLs) after the long-term frequent use of these drugs in a cattle herd, and to evaluate the production losses prevented by the use of an effective anthelmintic treatment to control these resistant gastrointestinal nematodes (GINs). A case of clinical helminthosis culminating in the death of steers was investigated, the history of the antiparasitic treatments used during an 11-year period in the herd was assessed, and an efficacy test involving seven different drugs was performed. Thereafter, two groups of heifers naturally infected by ML-resistant GINs were formed and strategically treated with either a highly effective (levamisole) or less effective drug (doramectin) over a 9-month period. The heifers were evaluated monthly based on eggs per gram of feces (EPG) counts and liveweights. An evaluation of the history of parasite control in the farm revealed that MLs were used in 96.5% of the treatments aimed at controlling GINs, ticks, and myiasis in the herd. The efficacy test showed the presence of GINs resistance to all the MLs tested. However, levamisole and albendazole sulphoxide were highly effective against these parasites. Heifers treated with levamisole gained 12.1 kg more liveweight on average, compared to those treated with doramectin. Thus, we conclude that indiscriminate and long-term use of MLs in the studied herd led to the failure of GINs control, a critical situation resulting in significant production losses, and a surge of clinical helminthosis in young cattle. In addition, we showed increase in liveweight gain due to using a highly effective drug, in comparison to an ML, during a 9-month period, in heifers naturally infected by ML-resistant GINs.

Impact on beef cattle productivity of infection with anthelmintic-resistant nematodes

ABSTRACTAims: The main goal of the current study was to evaluate, on a commercial beef cattle farm, the impact of infection with gastrointestinal nematodes resistant to both ivermectin (IVM) and moxidectin (MXD) on the productivity of calves.Methods: Male Aberdeen Angus calves, aged 9-11 months, with faecal nematode egg counts (FEC) ≥200 epg and body weight ≥190 kg, were allocated to two herds. Herd A (n = 90) grazed a maize-winter forage crop rotation and Herd B (n = 90) grazed a 2-year-old Agropyrum pasture. On Day 0 in each herd, calves were randomly allocated into five groups (n = 18), which were treated with 0.2 mg/kg IVM; 0.2 mg/kg MXD; 3.75 mg/kg ricobendazole (RBZ), both IVM and RBZ, or remained untreated. Faecal samples collected on Days -1 and 19 were used to determine the percentage reduction in FEC, and genera of the nematodes were determined by the identification of the third-stage larvae recovered from faecal cultures. Total weight gain was determined from body weights recorded on Days -1 and 91.Results: Overall mean reduction in FEC was 42% for IVM, 67% for MXD, 97% for RBZ and 99% for IVM + RBZ. The reduction in FEC for Cooperia spp. was ≤78% for IVM and MXD, and for Haemonchus spp. was 0 and 36% for IVM and MXD, respectively, confirming the presence of parasites resistant to both anthelmintics. Only IVM + RBZ treatment resulted in 100% efficacy against Haemonchus spp. The overall estimated mean total weight gain for calves treated with IVM was 15.7 (95% CI = 11.9-19.7) kg and for calves treated with IVM + RBZ was 28.8 (95% CI = 25-32.5) kg (p < 0.001). Mean total weight gain for calves treated with MXD was 23.5 (95% CI = 19.7-27.2) kg.Conclusions and clinical relevance: In calves naturally infected with resistant nematodes, under the production system assessed here, weight gains were lower in calves treated with anthelmintics that were moderately or highly ineffective compared to those treated with highly effective anthelmintics. These results demonstrate to farmers and veterinarians the importance of a sustainable and effective nematode control under field conditions.

Economic losses caused by the use of low-efficacy anthelmintic drugs in growing heifers

The aim of this study was to compare the economic revenue related to the use of low- or high-efficacy anthelmintic drugs within suppressive or strategic schemes of treatment in growing heifers. Heifers raised in a semi-intensive grazing system in southern Brazil were used. Levamisole and ivermectin were selected as the high- and the low-efficacy drugs, respectively, based on a previous efficacy test. Subsequently, these drugs were used within strategic (Strat; four times per year) or suppressive (Supp; once a month) treatment regimens in the heifers, and their liveweight and eggs per gram of feces counts were monthly evaluated during a 13-month period. The total costs of the treatments and their cost-benefit ratio in regard to liveweight gain were calculated. Final mean liveweight gains (kg) observed were 126.7 (Strat-Low), 133.6 (Supp-Low), 141.3 (Strat-High), 142.9 (Supp-High), and 125.8 (Control). Treatments with a high-efficacy drug resulted in monetary gains of US$ 19.56 (Strat-High) and US$ 14.98 (Supp-High), but Supp-Low and Strat-Low treatments caused economic losses. Total cost of the efficacy test (US$ 374.79) could be paid by the additional liveweight gain of 20 heifers from the Strat-High group. These results showed that it would be preferable not to treat the heifers against GIN if compared with treating them with a low-efficacy drug. In addition, we showed that the use of four treatments per year with a high-efficacy drug-selected by efficacy test-resulted in a profitable management to control GIN in growing heifers raised in a semi-intensive gazing system in southern Brazil.

Discovery of potential ovicidal natural products using metabolomics

Plant extracts are a potential source of new compounds for nematode control and may be an excellent alternative for the control gastrointestinal nematodes that are resistant to conventional anthelmintics. However, research involving natural products is a complex process. The main challenge is the identification of bioactive compounds. Online analytical techniques with universal detectors, such as high-performance liquid chromatography-mass spectrometry (HPLC-MS), together with metabolomics could enable the fast, accurate evaluation of a massive amount of data, constituting a viable option for the identification of active compounds in plant extracts. This study focused on the evaluation of the ovicidal activity of ethanol extracts from 17 plants collected from the Pantanal wetland in the state of Mato Grosso do Sul, Brazil, against eggs of Haemonchus placei using the egg hatchability test. The ethanol extracts were obtained using accelerated solvent extraction. The data on ovicidal activity, mass spectrometry and metabolomics were evaluated using HPLC-DAD-MS, partial least squares regression analysis (PLS-DA) and a correlation map (univariate correlation analyses) to detect compounds that have a positive correlation with biological activity. Among the ten metabolites with the best correlation coefficients, six were phenylpropanoids, two were triterpene saponins, one was a brevipolide, and one was a flavonoid. Combinations of metabolites with high ovicidal action were also identified, such as phenylpropanoids combined with the triterpene saponins and the flavonoid, flavonoids combined with iridoid and phenylpropanoids, and saponins combined with phenylpropanoid. The positive correlation between classes of compounds in plants belonging to different genera and biological activity (as previously identified in the literature) reinforces the robustness of the statistical data and demonstrates the efficacy of this method for the selection of bioactive compounds without the need for isolation and reevaluation. The proposed method also enables the determination of synergism among the classes, which would be impracticable using traditional methods. The present investigation demonstrates that the metabolomic technique was efficient at detecting secondary metabolites with ovicidal activity against H. placei. Thus, the use of metabolomics can be a tool to accelerate and simplify bioprospecting research with plant extracts in veterinary parasitology.

The acaricidal activity and mechanism of eugenol on Psoroptes cuniculi

In this study, the acaricidal effect of eugenol was measured and its mechanism of action investigated. The results showed that eugenol possessed the effect of killing Psoroptes cuniculi, and could regulate the mRNA expression of glutathione S-transferase (GST), catechinic acid (Ca) and thioredoxin (Trx). PPAR, NF-kappa B, TNF, Rap 1 and Ras signaling pathways might be the main pathways that involved into the process of killing mites. These findings suggested that eugenol could be developed into a new kind of acaricide, and further expand current knowledge on the mechanisms of eugenol for killing Psoroptes cuniculi of eugenol.

Behavioural and productive response to experimental infection with stage 3 larvae of Haemonchus contortus in feedlot bull-calves

Haemonchus contortus is a nematode parasite that establishes in the abomasum of ruminants, it has a cosmopolitan distribution and is a worldwide health problem for livestock. As a first line of defence against parasites, behaviour can help to prevent or fight infection, and may even serve as a method of early presumptive diagnosis. Parasites can affect performance of cattle and cause significant economic losses. The aim of this study was to determine the behavioural and productive changes induced by an experimental infection with H. contortus L3 in bovines. We used 32 dewormed bull calves, randomly divided into two groups, 8 no inoculated controls and 24 that were inoculated with 4000 L3 of H. contortus. Inoculation did not influence haematocrit or haemoglobin values at 0, 28 and 42 days post infection (P> 0.20); however, an increase in the frequency of urination (P = 0.0001) and defecation (P = 0.0001), number of steps (P < 0.001) and self-grooming (P < 0.01) events were observed, even in inoculated animals in which not parasite eggs were found in faeces. During the first 28 days post-inoculation with H. contortus, feedlot performance was not affected (P = 0.16), but during the last 14 days (29-42) inoculated animals gained 15% less weight compared to controls (P = 0.04). Over 42 days, inoculated calves showed a 28% poorer feed efficiency during the 42 days post-inoculation than controls (P < 0.01). Across the experiment, calves inoculated with H. contortus obtained less net energy both for maintenance as for gain from diet (P < 0.01). It is concluded that both, performance and behaviour were modified in feedlot bull-calves parasitized by H. contortus, supporting the practice of deworming when eggs of this parasite are detected in the faeces even in low amounts.

Effect of gastrointestinal nematodes on serum copper and phosphorus of growing beef calves in northwestern Argentina

The aim of this work was to study the effect of gastrointestinal nematodes (GINs) on copper (Cu) and phosphorus (P) in blood of beef cattle in two ranches (R1 and R2) located in northwestern Argentina. In 2015-2016 (R1) and 2016-2017 (R2), in each ranch, 22 weaned female calves were divided into two groups: calves treated systematically with 200 mcg/kg moxidectin every 45-50 days (TG) and untreated calves (UTG). The following parameters were measured: number of fecal eggs (epg), fecal cultures, serum Cu and P levels, and live weight gain (LWG). Differences between groups were compared using analysis of variance and Tukey test. GIN infections in both ranches were subclinical and moderate, showing the highest epg (R1 = 907 ± 754; R2 = 1049 ± 1040) by mid-winter. Epg values of TG groups were always negligible (> 93% of moxidectin efficacy). The dominant nematode genera were Cooperia and Haemonchus. The average serum Cu values (μg/dl) indicated low (R1 = 49.7 ± 18) and severe (R2 = 27.2 ± 14) deficiency. The effect of treatments was evident in both ranches from late winter, with TG showing significantly (p < 0.01) higher serum levels in winter, spring, and early autumn (R1 = 65.1, 50.9, and 60.3; R2 = 48.0, 25.7, and 22.4) than UTG (R1 = 44.3, 33.9, and 32.9; R2 = 25.5, 18.2, and 16.4). There were no differences in serum P levels between groups. LWG of TG increased significantly (p < 0.008) (27.2% in R1 and 38.6% in R2), with respect to those of UTG. This study showed a negative effect of GIN on serum Cu values in moderately infected growing calves.

Prevalence of Gastrointestinal Parasitism Infections in Cattle of Bass Kabylie Area: Case of Bejaia Province, Algeria

The objective of this study was to determine the prevalence, identification of species and the dynamics of gastrointestinal (GI) parasites during humid and dry seasons in local cattle of different ages. The study was carried out in the Province of Bejaia, Algeria from December 2013 to June 2014. A total of 143 fecal samples were collected from different cattle herds. Fecal samples were visually examined then observed using flotation and sedimentation microscopic techniques. Eggs and worms were identified according to standard procedures. 63% of the cattle examined were found positive with one or more parasite species. Our results revealed that the eggs of Eimeria spp. are predominant (43.87%) followed by Strongylus spp. (30.32%) and Fasciola hepatica (12.25%). Eggs of Strongyloides papillosus, Moniezia benedeni, Paramphistomum daubneyi. and Toxocara vitulorum represent 1.29%, 1.93%, 1.93% and 6.45%, respectively. There is a significant difference between the sex of the animal and the prevalence rate of Strongyle spp. and Eimeria spp. (P< 0.01 ). As for the body condition score, there is a statically significant (P< 0.01 ) difference between the prevalence rate of GI parasite and the nutritional status of cattle. In conclusion, our preliminary investigation demonstrated highly prevalent and that abundance of the polyparasitism nature of the disease in Bass Kabylie area. Also, there was a relationship between the distribution of GI parasitism in cattle and the factors analyzed (body condition score, age and sex). Further studies are need for planning future research and to design rational and sustainable locally GI parasites control programmes.

Design, Bioactivity and structure-activity of 3-Arylpropionate Derivatives as Potential High-Efficient Acaricides against Psoroptes Cuniculi

A series of 3-aryl propionic esters and their analogues were designed and evaluated for acaricidal activity in vitro against Psoroptes cuniculi, a mange mite. The structure–activity relationship (SAR) was also discussed. The results showed that 6 compounds possessed the excellent activity (LC₅₀ = 0.17–0.24 mM, LT₅₀ = 1.5–2.9 h), superior to ivermectin (LC₅₀ = 0.28 mM, LT₅₀ = 8.9 h) (P < 0.05), a standard drug. Furthermore, 7 compounds showed the good activity (LC₅₀ = 0.25–0.37 mM, LT₅₀ < 3.9 h), slightly lower or close to that of ivermectin. One compound displayed super-fast acaricidal property, far superior to ivermectin. SAR analysis found that the ester group is vital for the activity and the small steric hindrance adjacent to the ester group is advantageous for the high activity. The <C4 linear alcohol esters can give the higher activity. The substituents on the 3-phenyl ring or replacement of the 3-phenyl with heterocyclic aryl generally decreases the activity. The position of the ester group in the ester chain also influences the activity, where the 3-phenyl propionate and the benzoate had the highest and lowest activity, respectively. Thus, 3-arylpropionates emerged as new and promising high-efficient acaricide candidates.

Bioactivity and structure-activity relationship of cinnamic acid derivatives and its heteroaromatic ring analogues as potential high-efficient acaricides against Psoroptes cuniculi

A series of cinnamic acid derivatives and its heteroaromatic ring analogues were synthesized and evaluated for acaricidal activity in vitro against Psoroptes cuniculi, a mange mite. Among them, eight compounds showed the higher activity with median lethal concentrations (LC₅₀) of 0.36-1.07mM (60.4-192.1µg/mL) and great potential for the development of novel acaricidal agent. Compound 40 showed both the lowest LC₅₀ value of 0.36mM (60.4µg/mL) and the smallest median lethal time (LT₅₀) of 2.6h at 4.5mM, comparable with ivermectin [LC₅₀=0.28mM (247.4µg/mL), LT₅₀=8.9h], an acaricidal drug standard. SAR analysis showed that the carbonyl group is crucial for the activity. The type and chain length of the alkoxy in the ester moiety and the steric hindrance near the ester group significantly influence the activity. The esters were more active than the corresponding thiol esters, amides, ketones or acids. Replacement of the phenyl group of cinnamic esters with α-pyridyl or α-furanyl significantly increase the activity. Thus, a series of cinnamic esters and its heteroaromatic ring analogues with excellent acaricidal activity emerged.

Doenças parasitárias em bovinos e ovinos no sul do Brasil: frequência e estimativa de perdas econômicas

RESUMO: Foi realizado um levantamento das doenças parasitárias de bovinos e ovinos diagnosticadas na região sul do Rio Grande do Sul, de janeiro de 1978 a dezembro de 2014 no Laboratório Regional de Diagnóstico da Universidade Federal de Pelotas. Em bovinos 10,1% de todos os diagnosticos tratavam-se de parasitoses, das quais a mais frequente foi a tristeza parasitária bovina, com 55,1% dos surtos. As parasitoses gastrintestinais mistas foram diagnosticadas em 22,35% dos casos, a hemoncose em 4,36%, a dictiocaulose em 3,52%, a fasciolose em 2,68% e a eimeriose em 1,84%. Em ovinos 33,6% dos diagnósticos realizados eram parasitoses, sendo as mais frequentes as parasitoses gastrintestinais mistas (42,7%), a hemoncose (35,4%), a coenurose (9,1%) e a fasciolose (4,4%). Estima-se que as perdas somente por mortalidade, decorrentes de doenças parasitárias em bovinos somam aproximadamente R$16.968.000/ano. Na espécie ovina as perdas econômicas causadas por mortalidade de origem parasitária são de aproximadamente R$2.016.000/ano na região sul do Rio Grande do Sul. Foi possível concluir que, em bovinos, na região sul do Rio Grande do Sul, os agentes da TPB são os principais causadores de perdas econômicas, seguidos pelas parasitoses mistas. Em ovinos a parasitose gastrintestinal mista e a hemoncose, juntas, representam mais de 70% dos diagnósticos realizados.

Three-year evaluation of best practice guidelines for nematode control on commercial sheep farms in the UK

Anthelmintics are commonly used on the majority of UK commercial sheep farms to reduce major economic losses associated with parasitic diseases. With increasing anthelmintic resistance worldwide, several countries have produced evidence-based, best practice guidelines with an example being the UK's Sustainable Control of Parasites in Sheep (SCOPS) initiative. In 2012, a pilot study demonstrated that SCOPS-managed farms used fewer anthelmintic treatments than traditionally managed farms, with no impact on lamb productivity and worm burden. Building on these results, we collected data for three consecutive years (2012-2014) with the following aims: (1) To compare the effects of traditional and SCOPS-based parasite management on lamb productivity and worm burden; (2) To evaluate the effect of region and farm type on lamb productivity and worm burden; (3) To compare the frequency and patterns of use of anthelmintic treatment on traditional and SCOPS-managed farms. The study was carried out on 16 farms located in the North east and the South west of England and Wales. Lamb productivity was assessed by quantifying birth, mid-season and finish weights and calculating daily live-weight gains and time to finish in a cohort of 40-50 lambs on each farm. Five annual faecal egg counts were carried out on each farm to assess worm burden. No differences in lamb productivity and worm burdens were found between farms that adopted SCOPS guidelines and traditional farms across the three years. However, mean infection levels increased for both the SCOPS and the traditional groups. Lamb production was not significantly different for farm type and region but the effect of region on infection was significant. For both ewes and lambs, SCOPS farms carried out significantly fewer anthelmintic treatments per year, and used fewer anthelmintic doses/animal than traditional farms. The data suggest a trend to increasing use of anthelmintics in ewes on traditional but not on the SCOPS farms and a decreasing use of anthelmintics in lambs on both SCOPS and traditional farms. Across time, an increasing number of SCOPS farmers left their ewes and lambs untreated and the reverse was true for traditional farmers. Overall, farms implementing SCOPS guidelines used less anthelmintic treatments and less frequently than traditionally managed farms, without loss of animal performance or increased worm burden. Implementing SCOPS guidelines might have economic benefits for farmers, help reduce development of anthelmintic resistance on farms and decrease any environmental impact of anthelmintics. Furthermore, these data suggest some important epidemiological trends that should be investigated in long-term studies.

Anthelmintic resistance in gastrointestinal nematodes of beef cattle in the state of Rio Grande do Sul, Brazil

Gastrointestinal nematodes resistant to anthelmintics have been reported in several regions of Brazil, and they may be associated with economic losses for the cattle industry. This study aimed to evaluate the resistance status of gastrointestinal nematodes from naturally infected beef cattle to several commercially available anthelmintics, as well as to test the efficacy of combinations of anthelmintics against multi-resistant gastrointestinal nematodes. Ten farms located in Rio Grande do Sul state were selected by: farmers' consent; extensive raising system; availability of calves aged from 7 to 9 months naturally infected by gastrointestinal nematodes; absence of anthelmintic treatment for 60 days before the study; and presence of 70-100 calves or more of both genders with ≥ 200 eggs per gram of feces (EPG) (sensitivity of 50 EPG). These calves were distributed into 10 groups (of 7-10 animals) per farm and treated with ivermectin, doramectin, eprinomectin, fenbendazole, closantel, nitroxynil, disophenol, levamisole, albendazole, or moxidectin. Feces were collected 2 days before treatment and 14 days after treatment. Additional groups of 7-10 calves were used to test six different two-drug combinations at four of the studied farms. In general terms, fenbendazole was the most effective drug, followed by levamisole, disophenol, and moxidectin. However, parasite resistance to multiple drugs was found in all herds, especially in the genera Cooperia spp., Trichostrongylus spp., and Haemonchus spp.. Some of the two-drug combinations were effective against nematode populations identified as resistant to the same compounds when used as single drugs. The most effective combinations were moxidectin + levamisole, doramectin + fenbendazole, and levamisole + closantel. In this study, parasites resistant to the main commercially available anthelmintics were found in all herds, and some combinations of two active components belonging to different chemical groups were effective against multi-drug resistant gastrointestinal nematodes.

Characterization of Haemonchus contortus P-glycoprotein-16 and its interaction with the macrocyclic lactone anthelmintics

Anthelmintic resistance in veterinary nematodes, including Haemonchus contortus, has become a limitation to maintaining high standards of animal health. Resistance in this parasite, to all drug families including the macrocyclic lactones (MLs) is a serious issue worldwide. Mechanisms of resistance to the MLs appear to be complex and to include the elimination of these compounds by ABC transporter-like proteins present in nematodes. In order to investigate the potential involvement of ABC transporters in ML resistance in H. contortus, we have characterized the functionality of the ABC transporter H. contortus P-glycoprotein-16 (Hco-PGP-16) expressed in mammalian cells. This has included a study of its interaction with different MLs, including the avermectins, abamectin (ABA) and ivermectin (IVM), and the milbemycin, moxidectin (MOX). Hco-PGP-16 transport activity was studied using the fluorophore Rhodamine 123 (Rho 123). Transfected cells expressing Hco-PGP-16 accumulated less than 50% of Rho 123 than control cells, suggesting an active transport of this tracer dye by Hco-PGP-16. The influence of the MLs on the Rho123 transport by Hco-PGP-16 was then investigated. A marked inhibition of Rho123 transport by ABA and IVM was observed. In contrast, MOX showed less effect on inhibition of Rho123 transport by Hco-PGP-16, and the inhibition was not saturable. The difference in the interaction of the avermectins and MOX with Hco-PGP-16 may help explain the slower rate of development of resistance to MOX compared with the avermectins in H. contortus.

Acaricidal effect and histological damage induced by Bacillus thuringiensis protein extracts on the mite Psoroptes cuniculi

BACKGROUND

The mite Psoroptes cuniculi is a common worldwide ectoparasite and the most frequently found in rabbit farms. It causes significant economic losses on commercial rabbit breeding associated with poor leather quality, reduced conception rates, weight loss, poor growth and death. Several strategies have been proposed for the treatment of mange caused by this mite, ranging from the use of acaricides, entomopathogenic fungi, essential oils and vaccines. However, therapy and control of both human scabies and animal mange are still based mainly on the use of drugs and chemicals such as ivermectin, which involves disadvantages including genotoxic and cytotoxic effects, resistance and environmental damage. Bacillus thuringiensis is a bacterium, innocuous for human being, domestic animals and plants that produces highly biodegradable proteins, and has been used worldwide for biological control. The aim of this work was to find an alternative treatment based on biological control for scabies caused by Psoroptes cuniculi, using protein extracts from strains of Bacillus thuringiensis.

METHODS

P. cuniculi mites were obtained from naturally infected New Zealand rabbits, and different doses of protein from B. thuringiensis were added to the mites. We measured mortality and obtained the median lethal concentration and median lethal times. For histological analysis, the mites were fixed in 10% formalin, processed according to the paraffin embedded tissue technique. Sections were stained with hematoxylin-eosin to observe the general histological structure.

RESULTS

We report here for the first time evidence about the in vitro acaricidal effect caused by the strain GP532 of B. thuringiensis on the mite Psoroptes cuniculi, with an LC50 of 1.3 mg/ml and a LT50 of 68 h. Histological alterations caused by B. thuringiensis on this mite, included the presence of dilated intercellular spaces in the basal membrane, membrane detachment of the peritrophic matrix and morphological alterations in columnar cells of the intestine.

CONCLUSIONS

Since this mite is an obligate ectoparasite that affects rabbits, goats, horses, cows and sheep, B. thuringiensis protein extracts are proposed as a potential treatment for biological control of mange in farm animals.

Acaricidal activity of extracts from Ligularia virgaurea against the Sarcoptes scabiei mite in vitro

The aim of the present study was to investigate the acaricidal activity of Ligularia virgaurea. An extract was prepared by refluxing with ethanol and steam distillation, and its toxic effect was tested in vitro against Sarcoptes scabiei. The data from the toxicity tests were analyzed using a complementary log-log (CLL) model. The ethanol extract exhibited strong acaricidal activity against these mites; at a concentration of 2 g/ml it killed all S. scabiei within 2 h and at 1 g/ml it killed all S. scabiei within 6 h. Similarly, 2, 1, 0.5 and 0.25 g/ml concentrations of the extract had strong toxicity against S. scabiei, with median lethal time (LT₅₀) values of 0.716, 1.741, 2.968 and 4.838 h, respectively. The median lethal concentration (LC₅₀) values were 1.388, 0.624, 0.310 and 0.213 g/ml for Scabies mite in 1, 2, 4 and 6 h, respectively. The results indicate that the L. virgaurea extract has strong acaricidal activity and may be exploited as a novel treatment for the effective control of acariasis in animals.

Clinical efficacy of 9-oxo-10, 11-dehydroageraphorone extracted from Eupatorium adenophorum against Psoroptes cuniculi in rabbits

BACKGROUND

Animal acariasis is one of the important veterinary skin diseases. Chemical drugs have been widely used to treat and control this kind of disease. But many chemicals control could increase resistance in target species, toxicity and environmental hazards. We found that the 9-oxo-10, 11-dehydroageraphorone (euptox A) extracted from E. adenophorum has strong toxicity against P. cuniculi in vitro, but the in vivo acaricidal actions of euptox A have yet to be investigated.

RESULTS

A 14-day experiment was performed using rabbits that were naturally infested with P. cuniculi on a farm. Rabbits were randomly divided into five groups; animals in groups A, B and C were treated in each ear topically with 4.0 ml of 2.0 and 1.0 g/L (w/v) euptox A, respectively. Animals in groups D and E were treated with ivermectin (by injection; positive controls) and glycerol with water only (by embrocation; negative controls), respectively. Each rabbit was treated twice with separate treatments on days 0 and 7. Rabbits were observed daily and detailed examinations were performed on days 0, 7 and 14, to inspect the presence or absence of mites and scabs/crusts. Seven days after the initial treatment, the mean clinical scores (presence of scabs/crusts) decreased from 3.48, 3.37, 3.43 and 3.45 to 0.37, 0.42, 0.78 and 0.38 in the ears of animals in groups A, B , C and D, respectively, which were similar to the observations recorded in the positive control rabbits. However, the clinical score for negative control rabbits did not increase significantly (P > 0.05) during the experiment, and this changed from 3.32 to 3.37 in the ears, and there were no significant differences in clinical efficacy between left and right ears. After two treatments (0 and 7 d), the rabbits in groups A, B, C and D had recovered completely 14 days after the last treatment and no recurrences of infection were observed.

CONCLUSIONS

These results indicate that euptox A was potent compounds for the effective control of animal P. cuniculi in vivo.

Acaricidal activity of 9-oxo-10,11-dehydroageraphorone extracted from Eupatorium adenophorum in vitro

The acaricidal activity of the 9-oxo-10,11-dehydroageraphorone (euptox A), a cadenine sesquiterpene from Eupatorium adenophorum (E. adenophorum) against Sarcoptes scabiei and Psoroptes cuniculi was tested in vitro. A complementary log-log (CLL) model was used to analyze the data of the toxicity tests in vitro. The results showed euptox A had strong toxicity against mites, killing all S. scabiei at 3 and 4 mg/ml (m/v) concentration, while 4 mg/ml euptox A was also found to kill all P. cuniculi within a 4 h period. Similarly, 2, 3 and 4 mg/ml concentration of euptox A had strong toxicity against S. scabiei, with median lethal time (LT50) values at 0.687, 0.526, 0.326 h, respectively. 3 mg/ml and 4 mg/ml showed strong acaricidal action against P. cuniculi; the LT50 values were 0.693 and 0.493 h, respectively. The median lethal concentration (LC50) values were 1.068 mg/ml for Scabies mite and 0.902 mg/ml for P. cuniculi in 2 h. The results indicate that euptox A has strong acaricidal activity and may exploit as novel drugs for the effective control of animal acariasis.

The management of anthelmintic resistance in grazing ruminants in Australasia--strategies and experiences

In many countries the presence of anthelmintic resistance in nematodes of small ruminants, and in some cases also in those infecting cattle and horses, has become the status quo rather than the exception. It is clear that consideration of anthelmintic resistance, and its management, should be an integral component of anthelmintic use regardless of country or host species. Many years of research into understanding the development and management of anthelmintic resistance in nematodes of small ruminants has resulted in an array of strategies for minimising selection for resistance and for dealing with it once it has developed. Importantly, many of these strategies are now supported by empirical science and some have been assessed and evaluated on commercial farms. In sheep the cost of resistance has been measured at about 10% of the value of the lamb at sale which means that losses due to undetected resistance far outweigh the cost of testing anthelmintic efficacy. Despite this many farmers still do not test for anthelmintic resistance on their farm. Many resistance management strategies have been developed and some of these have been tailored for specific environments and/or nematode species. However, in general, most strategies can be categorised as either; identify and mitigate high risk management practices, maintain an anthelmintic-susceptible population in refugia, choose the optimal anthelmintic (combinations and formulations), or prevent the introduction of resistant nematodes. Experiences with sheep farmers in both New Zealand and Australia indicate that acceptance and implementation of resistance management practices is relatively easy as long as the need to do so is clear and the recommended practices meet the farmer's criteria for practicality. A major difference between Australasia and many other countries is the availability and widespread acceptance of combination anthelmintics as a resistance management tool. The current situation in cattle and horses in many countries indicates a failure to learn the lessons from resistance development in small ruminants. The cattle and equine industries have, until quite recently, remained generally oblivious to the issue of anthelmintic resistance and the need to take pre-emptive action. In Australasia, as in other countries, a perception was held that resistance in cattle parasites would develop very slowly, if it developed at all. Such preconceptions are clearly incorrect and the challenge ahead for the cattle and equine industries will be to maximise the advantages for resistance management from the extensive body of research and experience gained in small ruminants.