Macrocyclic Lactone Research Articles

COVID-19 Excess Deaths in Peru's 25 States in 2020: Nationwide Trends, Confounding Factors, and Correlations With the Extent of Ivermectin Treatment by State.

Introduction In 2020, nations hastened to contain an emerging COVID-19 pandemic by deploying diverse public health approaches, but conclusive appraisals of the efficacy of these approaches are elusive in most cases. One of the medicines deployed, ivermectin (IVM), a macrocyclic lactone having biochemical activity against SARS-CoV-2 through competitive binding to its spike protein, has yielded mixed results in randomized clinical trials (RCTs) for COVID-19 treatments. In Peru, an opportunity to track the efficacy of IVM with a close consideration of confounding factors was provided through data for excess deaths as correlated with IVM use in 2020, under semi-autonomous policies in its 25 states. Methods To evaluate possible IVM treatment effects, excess deaths as determined from Peruvian national health data were analyzed by state for ages ≥60 in Peru's 25 states. These data were compared with monthly summary data for excess deaths in Peru for the period 2020-2021 as published by the WHO in 2022. To identify potential confounding factors, Google mobility data, population densities, SARS-CoV-2 genetic variations, and seropositivity rates were also examined. Results Reductions in excess deaths over a period of 30 days after peak deaths averaged 74% in the 10 states with the most intensive IVM use. As determined across all 25 states, these reductions in excess deaths correlated closely with the extent of IVM use (p<0.002). During four months of IVM use in 2020, before a new president of Peru restricted its use, there was a 14-fold reduction in nationwide excess deaths and then a 13-fold increase in the two months following the restriction of IVM use. Notably, these trends in nationwide excess deaths align with WHO summary data for the same period in Peru. Conclusions The natural experiment that was put into motion with the authorization of IVM use for COVID-19 in Peru in May 2020, as analyzed using data on excess deaths by locality and by state from Peruvian national health sources, resulted in strong evidence for the drug's effectiveness. Several potential confounding factors, including effects of a social isolation mandate imposed in May 2020, variations in the genetic makeup of the SARS-CoV-2 virus, and differences in seropositivity rates and population densities across the 25 states, were considered but did not appear to have significantly influenced these outcomes.

Assessment of gastrointestinal nematode anthelmintic resistance and acaricidal efficacy of fluazuron-flumethrin on sheep and goat ticks in the North West province of South Africa.

Anthelmintic resistance (AR) and acaricide resistance (ACR) pose great economic threat to communal livestock raised by rural communities, limiting sustainable production. This study was conducted to assess the occurrence of AR and ACR against nematodes and ticks that infest small ruminants (sheep and goats) from small-scale farming communities in the North West Province of South Africa, as well as document the associated risk factors. The study was conducted on small-scale farming locations in two districts of the North West Province, namely, Dr. Ruth Segomotsi Mompati district and Dr. Kenneth Kaunda district, from November 2019 to March 2020. A questionnaire survey based specifically on antiparasitic treatment and related management practices was administered to 86 small-scale farmers. A fecal egg count reduction test (FECRT) was used to determine in vivo AR in small ruminants against benzimidazole (BZD), levamisole, and macrocyclic lactone on nine ruminant farms. Then, deoxyribonucleic acid was extracted from L3 larvae and resistant nematodes were identified using a polymerase chain reaction, targeting the internal transcribed spacer 2 gene. An egg hatch assay (EHA) and a larval mortality assay (LMA) were used to determine in vitro AR against thiabendazole (TBZ and BZD) in the same farms. Acaricide resistance against fluazuron-flumethrin (Drastic Deadline eXtreme) pour-on was assessed using an adult immersion test (AIT) on Rhipicephalus evertsi. Questionnaire results indicated that most farmers (89%) relied solely on anthelmintics. Farmers used visual appraisal to estimate the dosage, which is the primary cause of resistance. The FECRT revealed AR in all the farms. Egg hatch assay results revealed AR development against TBZ in all districts, with >95% of the eggs hatching at variable doses. Larval mortality assay results revealed the development of resistance against BZD, with 50% of L3 larvae surviving at different doses in all farms. Adult immersion test results indicated that fluazuron-flumethrin (>99%) exhibited high acaricidal efficacy against R. evertsi by inhibiting tick oviposition. This investigation found that sheep and goats in the studied areas are developing AR to gastrointestinal parasites. The findings of in vivo tests showed resistance with fecal egg count reduction percentage of <95% or lower confidence limit of <90%. The results of EHA and LMA revealed no evidence of inhibition of egg development and larval mortality, indicating the development of resistance. Acaricide resistance was not detected against fluazuron-flumethrin, which is commonly used in the study areas. Thus, developing management methods for these economically significant livestock nematodes, including teaching small-scale farmers how to properly administer anthelmintics and acaricides to their livestock, is urgently needed.

Efficacy of a fixed-dose combination injectable (0.2 mg/kg doramectin + 6.0 mg/kg levamisole hydrochloride) in New Zealand cattle against naturally acquired gastrointestinal nematode populations with demonstrated resistance to doramectin

Intensive farming practices and heavy reliance on anthelmintics have contributed significantly to the problem of macrocyclic lactone (ML) resistance in New Zealand. Farmers now have few options for effectively controlling cattle gastrointestinal nematodes (GINs) and regularly experience sub-optimal efficacy against economically important species. We present a novel fixed-dose combination injectable (FDCI) that simultaneously delivers 0.2 mg/kg doramectin and 6 mg/kg levamisole hydrochloride (HCl) to target a broad spectrum of cattle GINs in a single dose, providing an additional solution to endoparasite control in an environment of anthelmintic resistance. A dose confirmation study was conducted using naturally acquired infections of GINs in beef cattle in New Zealand. Cattle with GIN infections confirmed by fecal egg count (FEC) were randomly allocated (n = 12 per group) to the control (saline-treated), FDCI-treated or doramectin-treated group. On Day 0, cattle were weighed and administered a single subcutaneous injection of saline or endectocide. Rectal fecal samples were collected from each animal on Day 7 for individual duplicate fecal egg count (FEC) analysis, and coprocultures were conducted on pooled fecal samples within each treatment group. All animals were euthanized and necropsied for worm recovery on Days 14 through 16. Treatment efficacy was calculated based on reduction in FECs and worm burdens. All enrolled cattle were positive for GINs based on Day −5 FECs, with geometric mean (GM) FECs ranging from 337 to 521 eggs per gram (EPG). All saline-treated cattle remained positive for GIN infections for the study duration (Day 7 GM FEC = 427 EPG). Necropsy and worm recoveries revealed the presence of doramectin-resistant Cooperia oncophora, C. surnabada and Trichostrongylus longispicularis, as evidenced by ≤ 72.3 % efficacy of doramectin against these species. The new FDCI was ≥ 99.8 % effective against all GIN species, including ML-resistant C. oncophora, C. surnabada and T. longispicularis, providing broad-spectrum efficacy and eliminating economically important cattle GINs, including ML-resistant populations.

Efficacy in US cattle of a novel fixed-dose combination injectable (0.2 mg/kg doramectin + 6.0 mg/kg levamisole hydrochloride) against naturally acquired gastrointestinal nematode infections

Reports of macrocyclic lactone (ML) loss of efficacy suggest ML resistance in gastrointestinal nematodes (GINs) is a growing problem in the US cattle industry. Empirical and modeling data support combining an ML and second anthelmintic from a different drug class to help ML resistance development while effectively treating existing resistant parasite populations. Here, we present a novel fixed-dose combination injectable (FDCI) solution for cattle that delivers 0.2 mg of doramectin and 6.0 mg of levamisole hydrochloride (HCl) per kg of body weight. Field studies were conducted at six sites across the Midwest United States to investigate the efficacy of a single administration of the FDCI in treating common cattle GINs. Cattle (n = 425) with GIN infections confirmed by fecal egg count (FEC) on Day −10( ± 2) were randomly allocated to the control (saline) or treatment (FDCI) group. On Day 0, pre-treatment fecal samples were collected, and cattle were administered a single subcutaneous injection of saline (n = 106) or FDCI (n = 319). Post-treatment fecal samples were collected on Day 14. Fecal egg count reduction tests (FECRTs) were conducted using Day 0 and Day 14 FECs. Efficacy was evaluated using Day 14 FECs (FDCI-treated versus saline-treated). Within treatment, samples collected on Days 0 and 14 with ≥ 20 eggs per gram (EPG) were cultured for nematode larvae recovery and identification. Day −10 FECs for enrolled animals were similar between treatment groups. Coprocultures from cattle with FEC ≥ 20 EPG (n = 68 saline; n = 211, FDCI) on Day 0 showed the presence of Cooperia punctata, Ostertagia spp., Haemonchus spp., C. oncophora, Oesophagostomum spp. and Trichostrongylus spp. Day 14 FECs for FDCI-treated cattle were significantly reduced (0–3 EPG) compared to saline-treated cattle (0–1252 EPG) (p ≤ 0.0042). At all study sites, the efficacy of the new FDCI was ≥ 99.4% and the FECR was 0.99 or 1.00. Day 14 coprocultures from control cattle showed infections of common GIN genera, confirming the efficacy of the FDCI against GINs in the field. A single administration of the doramectin + levamisole HCl combination injectable effectively treats common and economically important cattle GINs.

Avermectin B1a Shows Potential Anti-Proliferative and Anticancer Effects in HCT-116 Cells via Enhancing the Stability of Microtubules.

Avermectins are a group of macrocyclic lactones that are commonly used as pesticides to treat pests and parasitic worms. Some members of the avermectin family, such as ivermectin, have been found to exhibit anti-proliferative activity toward cancer cells. This study aimed to investigate the potential anti-cancer activities of avermectin B1a using the HCT-116 colon cancer cell line. The MTT assay was used to calculate the IC50 by incubating cells with increasing doses of avermectin B1a for 24, 48, and 72 h. Flow cytometry was used to evaluate apoptosis following the 24 h incubation of cells. The migration capacity of the HCT-116 cells in the absence or presence of avermectin B1a was also investigated. Finally, tubulin polymerization in the presence of avermectin B1a was evaluated. Avermectin B1a presented anti-proliferative activity with an IC50 value of 30 μM. Avermectin B1a was found to promote tubulin polymerization at 30 μM. In addition, avermectin B1a induced apoptosis in HCT-116 cells and substantially diminished their ability to migrate. Avermectin B1a exhibits significant anti-cancer activity and enhances tubulin polymerization, suggesting that it can be used as a promising microtubule-targeting agent for the development of future anticancer drugs.

Droplet digital PCR as a tool to detect resistant isolates of Dirofilaria immitis

Prevention of canine heartworm disease, caused by Dirofilaria immitis, relies on macrocyclic lactones for which drug resistance is now a concern. Although genetic polymorphisms have been associated with resistance in D. immitis populations, the mechanism is still not well understood. The lack of reliable in vitro assays to detect resistance is a limitation for confirming resistance. Ten single nucleotide polymorphisms (SNPs) were previously clinically validated in D. immitis resistant isolates, using the MiSeq platform. This technique although useful for research studies is expensive and does not facilitate rapid detection of these markers in small numbers of clinical samples. We developed a droplet digital PCR protocol for detecting SNPs correlating with ML resistance. Specific primers and hydrolysis probes encompassing the wildtype and mutant alleles were designed to amplify the SNP targets from genomic DNA of different D. immitis isolates. Allele frequencies were determined and the suitability of the ddPCR assay was assessed and compared with MiSeq data. The ddPCR assay accurately detected and quantified alternate nucleotides in two isolates of reference, the ML-susceptible Missouri (MO) and ML-resistant JYD-34, at the previously identified SNP positions. The presence of the SNPs was also determined in additional isolates with known or putative susceptible or resistant phenotypes. We observed SNP1 and SNP2 are more predictive markers and appear suitable for rapid detection and monitoring of drug resistance. Our results suggested that ddPCR could be employed to distinguish infection due to actual genetic resistance from infection with susceptible parasites and also for rapid detection of isolates not only with ML susceptible and resistant genotypes but also mixed genotypes that correspond to heterogeneous isolates containing a mixed population of ML susceptible and resistant parasites. DdPCR may be a useful tool for conducting surveys, or assessments of individual isolates, for genetic evidence of resistance or developing resistance.

Synthesis of lactones from fatty acids by ring-closing metathesis and their biological evaluation

The present study involves the synthesis of macrocyclic lactones by the esterification of unsaturated fatty acids (oleic acid, undecenoic acid, and erucic acid) with unsaturated alcohols (allyl alcohol, prop-2-ene-1-ol, oleyl alcohol, and undecenol) followed by a ring closing metathesis reaction employing Grubbs' second generation catalyst (1.0-1.5 mmol). The structure of the compounds was confirmed by 1H NMR, 13C NMR, FT-IR, and ESI-Mass spectral studies. The antibacterial activity of the synthesised lactones was evaluated. The larger ring-sized lactone, namely, erucic acid lactone, exhibited excellent antibacterial activity against three bacterial cell lines, namely, Staphylococcus aureus, Staphylococcus epidermidis, and Bacillus subtilis. Undecenoic acid-based lactones exhibited excellent antibacterial activity selectively against only Staphylococcus epidermidis. The assay of macrolactones for their in vitro anticancer activity was carried out by MTT for different cancer cell lines, namely, human prostate epithelial cancer cells (ATCC HTB-81), HepG2 derived from hepatic cancer cells (ATCC HB-8065), SKOV3 derived from human ovarian cancer cells (ATCC HTB-77), MDAMB-231 derived from human breast cancer cells (ATCC HTB-26) and Chinese hamster ovarian (CHO-K1) cell lines. The molecules selectively exhibited anticancer activity against Chinese hamster ovarian (CHO-K1) cell lines. Among macrolactones, (E)-oxacyclotridec-11-en-2-one (MALUN) was more active and its activity was much higher compared to others and on par with the reference standard Mitomycin C. This was followed by (E)-oxacyclotricos-14-en-2-one (MOLER) and (E)-oxacyclononadec-10-en-2-one (MOLOH). The fatty acid-based cyclic lactones with selective antibacterial and anticancer activities can be further explored for a variety of pharmaceutical formulations.

Zearalenone in feed, urine and meat from three pig farms in Croatia

Zearalenone (ZEN) is a mycotoxin of the genus Fusarium which belongs to the group of macrocyclic lactones. ZEN contamination occurs during cereal harvest or in the early phase of storage if drying was insufficient. The aim of this study was to determine the level of ZEN in feed mixtures given to pigs during the fattening period at three different farms in the Republic of Croatia, as also to determine ZEN levels in urine and meat taken from the same animals. The study also examined correlation between ZEN concentrations in urine and meat with the estimation of ZEN intake in the human body through meat consumption, expressed as a percentage of the Tolerable Daily Intake (TDI). In total, 9 feed mixtures (3 samples per farm), 45 urine and 45 meat samples (from 15 animals per farm) were taken during 2021 from three pig farms located in eastern and central Croatia. ZEN concentrations were determined by the competitive enzyme ELISA method. All values in feed from all three farms were within maximum recommended limit (MRL) given in EU Recommendation, i.e., 250 μg/kg, though at one far, the levels recorded were just under the MRL. Monitoring of ZEN levels in urine can be used as an indicator for the detection of feed contamination with this mycotoxin. Although pigs were fed with feed with near the MRL level of contamination, a negligible percentage of TDI value was obtained for this mycotoxin for humans through meat consumption. However, since meat is just one component of the human diet, and in view of the fact that ZEN can be present in a number of foodstuffs, especially cereals, its total intake could be significantly higher than estimated herein.

A rapid and simple multi-residue methodology for quantification of anthelmintic macrocyclic lactones in cow, sheep and goat milk by HPLC: development, validation and application for the real samples

Anthelmintic macrocyclic lactones (MLs) [ivermectin (IVM), abamectin (ABA), doramectin (DRM), eprinomectin (EPR) and moxidectin (MXD)] are used worldwide for the treatment of parasitic infections in large and small ruminants because of their low mammalian toxicity and higher efficacy against internal and external parasites at low dose levels. A rapid, simple and sensitive HPLC and a modified QuEChERS extraction method were developed and validated for the analysis of five anthelmintic MLs residues in cow, sheep and goat milk. The analytes were extracted from milk samples by acetonitrile deproteinization, followed by the addition of sodium sulphate and sodium chloride to generate a phase partition. HPLC separation was conducted at 50⁰C using a C18 analytical column (Zorbax, Eclipse Plus, 250 mm × 4,6 mm, 5µ). The mobile phase consisted of a mixture of acetonitrile: methanol: water (58:38:4, v/v/v), delivered by an isocratic program at the flow rate of 1.3 ml/min. The elution of five analytes was completed within 11 min. The fluorescence detector (FLD) was set at an excitation wavelength of 375 nm and an emission wavelength of 470 nm. Recoveries ranged between 78.44% and 92.66%. The quantification limits (LOQ) of anthelmintic MLs in the milk samples from 3 different ruminant species ranged between 2.01 and 3.10 ng/g. The developed method was validated in accordance with the criteria of Commission Decision 2002/657/EC. Linearity, decision limit, detection and quantification limits, recovery, accuracy, precision, sensitivity and selectivity were determined, and satisfactory results were obtained. This developed and validated method is rapid, simple, sensitive and environmentally friendly, and can be used for multiple residue analyses of anthelmintic MLs in cow, sheep and goat milk for human consumption. The quantification limits for all drugs were below the maximum residue limits (MRLs), making the method appropriate for routine testing. Finally, the application of this method was assessed using real samples of cow, sheep and goat milk. The presence of MLs was confirmed in 8 out of 70 tested milk samples, which shows the method can be successfully used to determine the residue of anthelmintic MLs in three types of milk.

Atmospheric transport of particulate matter and particulate-bound agrochemicals from beef cattle feedlots: Human health implications for downwind agricultural communities

Beef cattle feedlot particulate matter (PM) is a complex mixture of dust, animal waste, agrochemicals, and bioaerosols. However, no empirical data exist quantifying downwind residential exposure to PM or PM-bound agrochemicals. In the current study, authors investigated transport of PM and co-occurring insecticides and anthelmintics downwind of three feedlots in the Southern Great Plains (SGP) of North America from May–August 2022. PM collected on total suspended particulate (TSP) filters was analyzed via UHPLC-MS/MS for six pyrethroids and five macrocyclic lactones (MLs). Downwind TSP concentrations rapidly declined from 0.01 to ≤1.6 km (Monte Carlo mean ± SEM; 5049 ± 96.1 μg/m3) and stabilized >1.6–12.4 km (1791 ± 9.9; μg/m3). Distance decay >1.6 km indicated downwind PM exceeded levels of safe human exposure during diurnal peak periods. Pyrethroids and MLs were detected >LOQ in 96.2 and 98.1 % of downwind samples. Screening-level cumulative residential exposure indicates elevated pyrethroid risk (LOC = 1; RI = 0.173) to rural children (1–2 yrs) living near cropland operations in the SGP, with disproportionate co-exposure to feedlot PM and legacy pollution in low-income, Hispanic and Latino communities. Frequent occurrence and sustained transport of pyrethroids downwind of feedlots facilitate residue accumulation in outdoor residential areas that must also be quantified to assess the magnitude of daily average and lifetime-adjusted oral and dermal exposure in surrounding communities. Results significantly expand the known distribution of feedlot-derived PM and agrochemicals and highlight human exposure pathways unrecognized in residential human health assessments supporting pesticide registration and feedlot risk evaluation.

Shortened strongylid egg reappearance periods in horses following macrocyclic lactone administration – The impact on parasite dynamics

Over the past three decades, equine strongylid egg reappearance periods (ERPs) have shortened substantially for macrocyclic lactone anthelmintics. The ERPs of ivermectin and moxidectin were originally reported in the 8–10 and 12–16 week ranges, respectively, but several recent studies have found them to be around 4–5 weeks for both actives. This loss of several weeks of suppressed strongylid egg output could have substantial implications for parasite control. This study made use of a computer simulation model to evaluate the impact of shortened ERPs on the anthelmintic performance of ivermectin and moxidectin against equine cyathostomins. The original ERPs were set to 7.1 and 15.4 weeks for ivermectin and moxidectin, respectively, while the reduced ERP was set to 4.6 weeks for both actives. Simulations were set to compare model outputs between original and reduced ERP scenarios and results expressed as percent increase in strongylid egg output, infective third stage larvae on herbage (L3h), and encysted early third stage larvae (EL3). For each drug, simulations were evaluated for two different treatment scenarios (2 and 4 treatments annually), two different age groups (yearlings and adults), and for four different climates (cold humid continental, temperate oceanic, humid subtropical, and hot/cold semi-arid). Across all simulations, there was a substantial increase of the three evaluated parameters. With the ivermectin simulations, all three parameters increased in the 100–300% range across climates, age groups and treatment intensities. The moxidectin simulations displayed a wider range of results with parameters increasing from a few hundred to several thousand percent. The increases were most pronounced for L3h in the two cooler climates, reaching as high as 6727%. Overall, the loss of anthelmintic performance was at a magnitude of 10 times larger for moxidectin compared to ivermectin. This performance loss was climate dependent, and was also affected by treatment intensity, but not by horse age. This is the first study to evaluate consequences of shortened ERPs in horses and demonstrated a substantial loss in anthelmintic performance resulting from this development. The results illustrate that anthelmintic efficacy is more than the percent reduction of fecal egg counts at 14 days post treatment, and that substantial anthelmintic performance can be lost despite FECRTs remaining at 100%.

NOVEL STRATEGIES FOR THE CONTROL OF GASTROINTESTINAL NEMATODES IN SHEEP

Gastrointestinal nematodes are very important parasites of domestic animals, especially in small ruminants. In sheep, diseases usually have a subclinical form with a decrease in body weight and production, and sometimes there can be visible clinical symptoms such as anorexia, anemia, severe diarrhea and protein loss, all of which together can lead to death. Commercial drugs such as benzimidazole and macrocyclic lactones have been successfully used for decades to control these parasites. However, the irrational application of these drugs has led to the development of anthelmintic resistance, a decrease in their effectiveness and consequent economic losses that threaten the sustainability of sheep breeding. In addition, the use of commercial preparations is also associated with the residues in animal products and the environment, and there is also an increase in the price of these preparations. For this reason, novel strategies for controlling of these parasites are actively seeking, with the goal of establishing an integrated approach that involves the application of several different strategies. On the one hand, these include strategies for the rational application of commercial preparations based on refugia (targeted treatments, targeted selective treatments), as well as the combination and rotation of anthelmintics from different chemical groups. On the other hand, an integrated approach implies the use of different alternative strategies such as genetic selection of animals naturally resistant to nematodes, rational management of pastures, balanced nutrition with supplementary nutrients, biological control (use of fungi, bacteria, etc.), development of vaccines as well as the use of botanical preparations (plants and their products such as extracts and essential oils). Various studies have proven the effectiveness of the mentioned strategies in the control of gastrointestinal nematodes of sheep, whereby the best results are achieved by their combined application. Thus, it is possible to slow down the development and spread of anthelmintic resistance, as well as achieve sustainable control of these parasites and reduce economic losses.

Effects of abamectin and fipronil insecticides on the brain and compound eyes of the embryo of Heteracris littoralis (Rambur) (Orthoptera: Acrididae)

Chemical pesticides are essentially hazardous. The risks differ from compound to compound, and much of the information on their actions on insect development remains to be captured. The toxicity of abamectin (a macrocyclic lactone, acting on glutamate-gated chloride channels of insects), and fipronil (a phenylpyrazole, disrupting the GABA receptors) was given on embryos of the short-horned grasshopper Heteracris littoralis (Rambur, 1838) for the first time. Abamectin is 66 times more fatal than fipronil. Treated eggs with a sublethal dose gave a reduction up to 51% in hatchability as compared with normal eggs; yet, without any effect on the incubation period. Many embryos have stopped developing at certain developmental stages. The disruptive effects of both the tested chemicals on the brain and the compound eyes were described. The brain and the compound eyes were severely disrupted. The optic lobes appear small in size, and this led to the malformed compound eyes and optic nerves. The brain cells appeared loose and perhaps few in number. The neurosecretory materials carried in the neurosecretory cells were not clear. The neuropil was wide in the normal brain rather than in treated ones. Treated embryos suffered a shrinkage in ommatidia size and number, they are also irregular. Perhaps continued and precise studies should be made to minimize resistance, usually low doses enhance. Continuing studies on the tested pesticides may provide novel insights on their actions for more effective insect control strategies.

Macrocyclic lactone residues in cattle dung result in a sharp decline in the population of dung beetles in the rangelands of northern China

Dung beetles perform important ecosystem functions including livestock dung removal, nutrient recycling and parasite control. However, more research is being done on the effects of veterinary drug residues on dung beetles due to the widespread usage of macrocyclic lactone (ML). While a number of research on this topic have been published in Europe, Africa and America, few have been in Asia. In the past decade, standard veterinary antibiotics administration in livestock grazing systems in the rangelands of northern China has included ML. In the present study, the abundance, species richness, diversity, and evenness of dung beetles in the rangelands of northern China in 2020 were examined and compared to the reference data from 2010, when parasiticide had never been used, to better understand the changes in dung beetle communities after the long-term use of parasiticides. The abundance and diversity of dung beetle populations in the current three rangelands in northern China were first investigated using a baited-trap experiment. The findings revealed a 67.3 % decrease in dung beetle abundance and a shift in the dominant species from Aphodiidae to Staphylinidae. Cattle dung on the three studied rangelands included high ML residues ranging from 22.7 ppb to 130.1 ppb. According to the results of the correlation analysis, the beetle abundance and ML residues in cattle dung were negatively correlated. In the meantime, the findings of a field examination of undecomposed cattle dung on 34 rangelands in northern China revealed that the coverage rate of dried cattle dung pats ranged from 2 % to 6 % on 24 rangelands and reached above 10 % on four rangelands. According to the current findings, the decrease in cattle dung beetles would slow down the decomposition of cattle dung pats and decrease the available grazing area. Therefore, the dung beetle community in the rangelands of northern China would be negatively impacted by the frequent administration of ML to cattle. This would result in significant changes to the biogeochemical cycle of rangeland and had a negative impact on the development of local husbandry. During rangeland management, more attention should be given to the dynamic changes of coprovorous insects and the application of veterinary antibiotics.

Long-term evaluation of viability of microfilariae and intravenously transplanted adult Dirofilaria immitis in microfilaremic dogs treated with low-dose, short- and long-treatment regimens of doxycycline and ivermectin

BackgroundMicrofilarial (mf) counts were monitored over 21.3 months for any rebound that might occur in counts, and adulticidal efficacy was assessed following administration of low dosage with short- and long-treatment regimens of doxycycline and ivermectin to heartworm-microfilaremic dogs.MethodsTwelve heartworm-naïve beagles infected with 10 pairs of adult Dirofilaria immitis by intravenous transplantation were randomly allocated to three groups of four dogs. All treatments started on day 0. On day 0, Group 1 (short-treatment regimen) received doxycycline orally at 10 mg/kg once daily for 30 days plus ivermectin orally (minimum, 6 mcg/kg) on days 0 and 30. Group 2 (long-treatment regimen) received doxycycline orally at 10 mg/kg once daily until individual dogs became mf-negative (72–98 days) and ivermectin every other week until individual dogs became mf-negative (6–7 doses). Group 3 was the untreated control. Mf counts and antigen (Ag) tests were conducted. Dogs were necropsied for recovery and enumeration of heartworms on day 647.ResultsDay −1 mean mf counts were 15,613, 23,950, and 15,513 mf/ml for groups 1, 2, and 3, respectively. Mean counts for Groups 1 and 2 declined until days 239 and 97, respectively, when all were negative. Group 3 had high mf counts throughout the study. There was not a rebound in mf counts in any of the treated dogs after they became amicrofilaremic. All dogs in group 1 and group 3 were Ag-positive throughout the study and had at least one live female worm at necropsy. All dogs in treated Group 2 were positive for Ag through day 154, but were antigen-negative on days 644 and 647, as all had only male worms. Mean live adult worm recoveries for Groups 1, 2, and 3 were 6.8 (range, 5–8), 3.3 (range, 1–6), and 16.0 (range, 14–17), respectively, with a percent reduction in adult worm counts of 57.5% for Group 1 and 79.3% for Group 2.ConclusionsThese data lend support to the use of the American Heartworm Society Canine Guidelines for adulticide therapy recommending the initiation of doxycycline plus a macrocyclic lactone (ML) at the time of the heartworm-positive diagnosis.Graphical

Evaluation of renal values during treatment for heartworm disease in 27 client-owned dogs

BackgroundCanine heartworm disease (CHD) caused by Dirofilaria immitis remains a common preventable disease with increasing incidence in some parts of the USA. The treatment guidelines of the American Heartworm Society (AHS) currently recommend monthly macrocyclic lactone administration, 28 days of doxycycline given orally every 12 h and three injections of melarsomine dihydrochloride (1 injection on day 2 of treatment followed 30 days later by 2 injections 24 h apart). Minocycline has also been utilized when doxycycline is unavailable. The systemic effects of CHD, which particularly impact cardiac and renal function, have been described, with infected dogs often experiencing renal damage characterized by an increase in serum concentrations of renal biomarkers. Although the AHS treatment protocol for CHD has been shown to be safe and effective in most cases, the potential for complications remains. No study as of yet has evaluated changes in symmetric dimethylarginine (SDMA), a sensitive marker of renal function, during treatment for CHD. The purpose of the present study was to evaluate renal function in dogs by measuring serum creatinine and SDMA concentrations during the adulticide treatment period.MethodsSerum creatinine and SDMA concentrations were measured in 27 client-owned dogs affected by CHD at the following time points: prior to starting doxycycline or minocycline therapy (baseline), during doxycycline or minocycline therapy (interim), at the time of the first dose of melarsomine (first dose), at the time of the second dose of melarsomine (second dose) and at the dog’s follow-up visit after treatment, occurring between 1 and 6 months after completion of therapy (post-treatment). Concentrations of creatinine and SDMA were compared between time points using a mixed effects linear model.ResultsMean SDMA concentrations following the second dose of melarsomine were significantly lower (−1.80 ug/dL, t-test, df = 99.067, t = −2.694, P-Value = 0.00829) than baseline concentrations. There were no other statistically significant differences in the concentration of either biomarker between the baseline and the other time points in CHD dogs undergoing treatment.ConclusionsThe results suggest that the current AHS protocol may not have a substantial impact on renal function.Graphical

Challenges in the diagnosis and management of skin diseases in alpacas, goats, pigs, and sheep.

The primary aim of this article is to provide an overview of several selected skin conditions in livestock species. Topics include ectoparasites in alpacas, antler velvet in reindeer, immune-mediated disease in goats, ectoparasites in pigs, Culicoides allergic dermatitis and parapox infection in sheep. When dealing with skin disease in livestock, it is important to collect a detailed history and undertake a thorough clinical examination to include the axilla, groin, limbs and feet. While the diagnosis will often be anticipated from the history and presentation, it is important to consider a differential diagnosis list and appropriate diagnostic testing before embarking on a poly-pharmacy approach to "rule out" causes of disease. This is particularly important where morbidity is high and the livestock of perceived high value to the keeper/owner, such as goats and small-breed pigs, or when the skin condition is long standing/chronic. Ideally, the management plan should sequentially clarify the role of microbial infection and then ectoparasites before considering less common allergic and autoimmune conditions. Skin cytology is an invaluable in-house diagnostic method that can support the findings of culture. Taking skin samples for histopathology and possibly culture may prove valuable once other diagnostic methods have been explored. Given the need to protect the use of parenteral antimicrobials, topical antimicrobial therapies can be deployed successfully. The repeated use of macrocyclic lactones (avermectins) must be balanced in terms of the risks of promoting anthelmintic resistance versus controlling or eradicating the ectoparasites that have, ideally, been specifically identified.

O71 | Pharmacokinetics of macrocyclic lactones endectocide in indigenous zebu cattle and its insecticidal efficacy on Anopheles arabiensis

Journal of Veterinary Pharmacology and TherapeuticsVolume 46, Issue S1 p. 63-63 ORAL PRESENTATIONS O71 | Pharmacokinetics of macrocyclic lactones endectocide in indigenous zebu cattle and its insecticidal efficacy on Anopheles arabiensis First published: 11 June 2023 https://doi.org/10.1111/jvp.13237Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. Volume46, IssueS1Special Issue: 15th International Congress of the European Association for Veterinary Pharmacology and Toxicology held Bruges, Belgium, July 2–5, 2023June 2023Pages 63-63 RelatedInformation

Investigation of transformation products of selected veterinary drugs generated by electrochemistry, microsomal assays, hydrolysis &amp; photolysis

The knowledge of transformation pathways and transformation products of veterinary drugs is important for health, food and environmental matters. Residues (original veterinary drug and transformation products) are found in food products of animal origin and also in the environment (e.g., soil or surface water). Several transformation processes can alter the original veterinary drug, ranging from biotransformation in living organism to environmental degradation processes like photolysis, hydrolysis, or microbial processes. In this thesis, four veterinary drugs were investigated, three ionophore antibiotics Monensin, Salinomycin and Lasalocid and the macrocyclic lactone Moxidectin. Ionophore antibiotics are mainly used to cure and prevent coccidiosis in poultry especially prophylactic in broiler farming. Moxidectin is an antiparasitic drug and is used for the treatment of internal and external parasites in food‐ producing and companion animals. The main objective of this work was the usage of different laboratory approaches to generate and identify transformation products. The identification was conducted using high‐resolution mass spectrometry (HR‐MS). A major focus was put on the application of electrochemistry for simulation of transformation processes. The electrochemical reactor, equipped with a three‐electrode flow‐through cell, enabled the oxidation or reduction by applying a potential. Derived transformation products were analyzed by online coupling of the electrochemical reactor and a HR‐MS and offline by liquid chromatography (LC) combined with HR‐MS. The main modification reaction of the identified transformation products was different for each investigated veterinary drug. Monensin was showing decarboxylation and demethylation as main modification reactions, for Salinomycin mostly decarbonylation was occurring and for Lasalocid methylation was prevalent. For Moxidectin I observed oxidation (hydroxylation) reaction and adduct formation with solvent. In general, for salinomycin and Lasalocid more transient transformation products (online measurement) than stable transformation products (offline measurements) were detected. In contrast, the number of transformation products using online and offline measurements were identical for monensin and moxidectin. As a complementary approach, metabolism tests with rat or human liver microsomes were made for the ionophore antibiotics. Monensin was investigated by using rat liver microsomes and identified transformation products were based on decarboxylation and demethylation. Salinomycin and Lasalocid were converted by human and rat liver microsomes. For both substances were more transformation products found by using human liver microsomes. The transformation products of the rat liver microsome conversion were redundant, the transformation products were also found at the human liver microsome assay. Oxidation (hydroxylation) was found to be the main modification reaction for both. In addition, a frequent ion‐exchange between sodium and potassium was identified. The last two experiments were performed for one substance each, the hydrolysis of monensin and the photolysis of moxidectin was investigated. The transformation products of the pH‐ dependent hydrolysis were based on ring‐opening and dehydration. Moxidectin formed several transformation products by irradiation with UV‐C light and main modification reactions were isomeric changes, (de‐)hydration and changes of the methoxime moiety. In summary, transformation products of the four investigated veterinary drugs were generated by the different laboratory approaches. Most of the identified transformation products were identified for the first time. The resulting findings provide an understanding for clarifying the transformation behavior.

Comparison of the efficacy of macrocyclic lactone anthelmintics, either singly or in combination with other anthelmintic(s), in nine beef herds in southern NSW.

Anthelmintic resistance (AR) is a well-recognized challenge in farmed ruminants. The use of anthelmintics in combination is one of the strategies recommended to slow the rate of AR development. Two studies were undertaken in 2017 and 2019 to assess the efficacy of single-dose macrocyclic lactone (ML) anthelmintic and ML combination drenches. In total, 11 Faecal Egg Count Reduction Trials (FECRTs) were set up in 10 different beef herds, with results available from 10 of those FECRTs (9 herds). AR to a single ML anthelmintic was detected in all 9 herds, with resistance to Cooperia and Haemonchus spp on 9 farms, and resistance to Ostertagia and Trichostrongylus spp on 2 farms. In contrast, for the ML combination anthelmintics, all FECRTs resulted in efficacies of 99%-100%. The results suggest that cattle producers should strongly consider using combination drenches in their herds in preference to single actives.