Resistance to a triple-combination anthelmintic in Trichostrongylus spp. on a commercial sheep farm in New Zealand

Abstract

AIM: To evaluate resistance to anthelmintics containing abamectin, levamisole, and oxfendazole (AB-LEV-OX), derquantal and abamectin (DEQ-AB), moxidectin, and monepantel in naturally acquired gastrointestinal nematodes present on a sheep farm.

METHODS: Faecal nematode egg count reduction tests (FECRT) were carried out on lambs that were approximately 7 months-old and infected with naturally acquired nematodes. Lambs were randomly allocated to one of five groups (n=15 per group): treatment with 2?mg/kg derquantel and 0.2?mg/kg abamectin; 0.2?mg/kg abamectin, 8?mg/kg levamisole HCl and 4.5?mg/kg oxfendazole; 2.5?mg/kg monepantel; 0.2?mg/kg moxidectin, or no treatment. Post-treatment samples were collected 12 days later. Abomasa and small intestines were collected from two slaughtered lambs from each of the DEQ-AB, AB-LEV-OX, moxidectin and control groups 15 days after treatment, for nematode counting.

RESULTS: The FECRT demonstrated that efficacy was 90.3 (95% CI=84.2–94.1)% for AB-LEV-OX, 54.5 (95% CI=28.4–71.1)% for moxidectin, 99.2 (95% CI=97.4–99.8)% for DEQ-AB and 100% for monepantel, across all genera. For Trichostrongylus spp. efficacy was 85.5% for AB-LEV-OX and 46.7% for moxidectin. Haemonchus spp. were fully susceptible to all treatments. Post-treatment nematode counts indicated that the resistant Trichostrongylus spp. were from the small intestine.

CONCLUSIONS: Anthelmintic resistance to both AB-LEV-OX and moxidectin was present in the Trichostrongylus genus on a commercial sheep farm. Monepantel and DEQ-AB were both effective against Trichostrongylus spp. based on FECRT results.

CLINICAL RELEVANCE: This finding of resistance to an AB-LEV-OX triple-combination anthelmintic in the Trichostrongylus genus in sheep in New Zealand further limits anthelmintic treatment options available, and calls into question whether this combination is suitable for use as a quarantine treatment.     

Hybridization in Australian Freshwater Crayfish—Production of All-Male Progeny

Abstract.— In freshwater crayfish aquaculture high densities can result from uncontrolled reproduction. Hence some farmers manually sex yabbies Cherax albidus and stock only mate crayfish in farm dams or ponds. Although male-only yabby populations produce an estimated 70% increase in gross income, hand sexing is time consuming and prone to error. A hybridization experiment using freshwater crayfish from the yabby species complex, collected from geographically isolated regions throughout Australia, revealed a hybrid between Cherax rotundus females and C. albidus males which consistently produces only male progeny. This has been confirmed in nine crosses of the same two species. The reciprocal cross of C. albidus females × C. rotundus males produces both male and female progeny. The consistent production of only male progeny by hybridization has not been recorded previously for a crustacean.     

A pilot study to investigate the measurement of immunoglobulin A in Welsh Cob and Welsh Pony foals’ faeces and their dam’s milk

ABSTRACT

Aims: To determine if an ELISA for measurement of IgA in equine serum could be used to measure concentrations of IgA in foal faeces and to determine correlations with concentrations in the milk of the dam.

Methods: Faeces from 20 Welsh Cob and Welsh Pony foals and milk from their dams were collected within 12?hours (Day 0) and at 6 days after parturition (Day 6). On Day 6, faeces could not be collected from 2/20 foals, and milk samples could not be collected from 3/20 mares. An equine IgA ELISA validated for serum and plasma was used to measure concentrations of IgA in all samples in triplicate. The precision of the assay for each sample type was determined using modified CV.

Results: IgA was not detectable in 7/20 Day 0 faecal samples and in 2/18 Day 6 faecal samples. For samples with detectable IgA, the mean modified CV was 10.5 (95% CI?=?6.0–15.0)% for Day 0 faecal samples, and was 6.8 (95% CI?=?4.3–9.4)% for Day 6 faecal samples. Median concentrations of IgA in faeces on Day 0 were lower than concentrations on Day 6 (0.7?mg/g vs. 37?mg/g dry matter; p?=?0.003). Concentrations of IgA in milk and faeces on Day 6 were statistically correlated (r?=?0.59; p?=?0.006).

Conclusions and clinical relevance: The IgA ELISA showed acceptable precision when used to estimate concentrations of IgA in foal faeces during the first week of life, but IgA could not be detected in 37% of meconium samples collected on Day 0. This assay may be useful for investigation of the role of maternal milk IgA in the gastrointestinal tract of neonatal foals, but further assessment of both accuracy and precision of the ELISA is required.     

Scrotal circumference,bodyweight and semen characteristics in growing dairy-breed natural-service bulls in Tasmania,Australia

Aims: To provide herd managers with a set of decision rules allowing them to predict the likelihood that a juvenile bull is ready for Bull Breeding Soundness Evaluation (BBSE), or breeding, if bodyweight and scrotal circumference are known.

Methods: This was a longitudinal study following two groups of young pasture-fed Holstein and Jersey bulls from northwest Tasmania, Australia. Individual scrotal circumference, bodyweight and semen characteristics were recorded at 6–8 weekly intervals, from 6–18 months of age. Classification and regression tree analyses were used to predict the probability that a bull had ≥70% normal sperm morphology based on scrotal circumference and bodyweight measurements.

Results: Overall 1,661 scrotal circumference and bodyweight measurements were obtained, and 518 semen samples from 356 bulls were assessed for sperm morphology, from 16 examination sessions that took place between 29 May 2015 and 17 August 2016. Classification and regression tree analyses generated a decision tree for Holstein bulls with four node endpoints, and for Jersey bulls with three node endpoints. Diagnostic test performance showed that for Holstein bulls, using the node endpoints of scrotal circumference ≥27?cm and bodyweight ≥349?kg, 98% had ≥70% normal sperm (positive likelihood ratio 10.4; 95% CI?=?2.7–41), and using the node endpoints of scrotal circumference ≥27?cm and bodyweight between 282–349?kg, 89% had ≥70% normal sperm (positive likelihood ratio 1.6; 95% CI?=?0.9–2.6). For Jersey bulls, using the node endpoints of bodyweight ≥259?kg and scrotal circumference ≥29?cm, 88% had ≥70% normal sperm (positive likelihood ratio 3.4; 95% CI?=?1.6–7.0).

Conclusions: This study provides a set of relatively simple decision rules based on bodyweight and scrotal circumference measurements that allows herd managers to assess the likelihood that juvenile bulls are ready for BBSE or breeding.

Abbreviations: BBSE: Bull breeding soundness evaluation; BRT: Boosted regression tree     

Direct measurement of femtomoles of osmium and the 187Os/186Os ratio in seawater

Two depth profiles of the osmium concentration and the 187Os/186Os isotopic ratio in the Indian Ocean showed that the osmium concentration seems to be unaltered by chemical or biological processes occuring in seawater; accordingly, osmium is conservative. These data were obtained from an experimental method that eliminated the problems related to osmium preconcentration. This method led to a new evaluation of the concentration of osmium in seawater; the mean concentration of osmium and the 187Os/186Os ratio are equal to 10.86 +/- 0.07 picograms per kilogram and 8.80 +/- 0.07, respectively. The results suggest the existence of an organocomplex that dominates the speciation of osmium in seawater.