Inconsistency of in vitro exsheathment triggers for gastrointestinal nematode parasites of sheep, cattle and deer.

Exsheathment is crucial in the transition from free-living to parasitic phase for most strongyle nematode species. A greater understanding of this process could help in developing new parasitic control methods. This study aimed to identify commonalities in response to exsheathment triggers (heat acclimation, CO and pH) in a wide range of species (Haemonchus contortus, Trichostrongylus spp.

Cross infection of Haemonchus contortus between calves and lambs.

Haemonchus contortus can frequently be found infecting pre-weaned beef calves on sheep and beef farms around the North Island of New Zealand. The purpose of this study was to determine whether parasites cycling in young cattle constitute a potentially important source of infection for sheep. A field isolate of H.

Simultaneous resistance to multiple anthelmintic classes in nematode parasites of cattle in New Zealand.

Resistance to the benzimidazole and macrocyclic lactone anthelmintics is widespread in Cooperia spp. on cattle farms in New Zealand. Since this was first documented in 2006 little has changed in cattle farming systems except for the widespread use of levamisole to control Cooperia spp.

Worms and welfare: Behavioural and physiological changes associated with gastrointestinal nematode parasitism in lambs.

Parasitism with gastrointestinal nematodes (GIN) is a worldwide issue impacting negatively on animal production, health, and welfare. Therefore, early diagnostic signs of parasitism are required to allow for timely interventions. The objective of this study was to evaluate the behavioural and physiological changes in lambs associated with GIN infection.

In vitro evaluation of fitness parameters for isolates of Teladorsagia circumcincta resistant and susceptible to multiple anthelmintic classes.

Anthelmintic resistance (AR) is an ever increasing problem for the sheep industry. Several studies worldwide have investigated reversing the trend of increasing AR and documented evidence for reversion toward susceptibility has been found. The hypothesis that resistance mutations compromise parasite fitness was drawn from this evidence.

The production costs of Haemonchus contortus and other nematode parasites in pre-weaned beef calves in New Zealand.

Haemonchus contortus can frequently be found infecting pre-weaned beef calves on sheep and beef farms around the North Island of New Zealand. The purpose of this study was to consider whether the presence of this parasite alone, or as part of a mixed infection, could be impacting growth rates of young animals, on three commercial farms in the North Island of New Zealand. Trials were conducted on commercial sheep and beef farms in each of the Northland, King Country and Gisborne regions, in late summer/autumn (February to April) of 2016 to measure the effect of treatment with narrow and broad spectrum anthelmintics on liveweight gain of spring-born calves pre-weaning.

Host effects on the free-living stages of Haemonchus contortus.

A group of 5 lambs (Host 1-5) was infected with the same batch of Haemonchus contortus and after patency individual faecal samples were collected, separately incubated at 23 °C for 14 days and third stage larvae collected through Baermannisation. Life-history traits were compared between larvae from different hosts: the length of the larvae was measured by microscope image analysis, larval survival in water at 35 °C, larval susceptibility to ivermectin (EC) in a migration assay, the proportion of larvae exsheathing in vitro and the proportion establishing to the adult stage in young lambs. For all traits there were significant differences between the host animals, with larvae from specific hosts following a consistent pattern of displaying the highest or lowest trait results.

Route of administration influences the concentration of ivermectin reaching nematode parasites in the gastrointestinal tract of cattle.

An animal trial was conducted to measure the concentrations of ivermectin occurring in abomasal and small intestinal contents and mucosa, and in the target parasites (Ostertagia ostertagi and Cooperia oncophora) following administration by subcutaneous, oral and pour-on routes. Twenty-five steers were infected with ivermectin-resistant isolates of O. ostertagi and C.

Monitoring equine ascarid and cyathostomin parasites: Evaluating health parameters under different treatment regimens.

Background: Strongylid and ascarid parasites are omnipresent in equine stud farms, and ever-increasing levels of anthelmintic resistance are challenging the industry with finding more sustainable and yet effective parasite control programs.

Objectives: To evaluate egg count levels, bodyweight and equine health under defined parasite control protocols in foals and mares at two Standardbred and two Thoroughbred stud farms.

Study Design: Longitudinal randomised field trial.

Abomasal nematode species differ in their in vitro response to exsheathment triggers.

A crucial step in the infection process of grazing ruminants by gastro-intestinal nematodes is the exsheathment of the infective third-stage larva following ingestion. Recently, heat shock was shown to play an important role in the carbon dioxide (CO)-dependent exsheathment response in Haemonchus contortus. The current in vitro study set out to evaluate the role of heat shock in other abomasal species.

Nematode parasites in young cattle: what role for unexpected species?

AIMS To investigate the timing of infection of beef calves with sheep nematode species on three sheep and beef farms, and to determine the prevalence of cross-infection in calves before weaning across a larger number of farms. METHODS Farms in the Far North, Gisborne and Tararua districts, in the North Island of New Zealand, were enrolled in 2014. Fresh faecal samples were collected from approximately 10 calves on each farm between birth and up to 5 months after weaning.

Carbon dioxide is an absolute requirement for exsheathment of some, but not all, abomasal nematode species.

The first step in the infection process of grazing ruminants by gastrointestinal nematodes is the exsheathment of the third-stage larva (L3). Exsheathment of various species can be achieved in vitro using carbon dioxide (CO) under the appropriate temperature and pH conditions. However, it remains unclear whether elevated CO levels are an absolute requirement for exsheathment.

Heat shock, but not temperature, is a biological trigger for the exsheathment of third-stage larvae of Haemonchus contortus.

Gastrointestinal parasites are an important health issue in grazing ruminants. Understanding the processes involved in the transition from the free living to the parasitic life stage of these nematodes is one avenue to identifying new targets amenable to future intervention. The transition to parasitism is initiated by exsheathment and is triggered by the sudden change in environment after ingestion of the infective larva by the host.

The effect on liveweight gain of using anthelmintics with incomplete efficacy against resistant Cooperia oncophora in cattle.

A replicated field trial was conducted to measure the effect on liveweight gain of failing to adequately control anthelmintic resistant populations of Cooperia oncophora and to determine whether populations, and hence production losses, increased with time. Eight mobs of 10 Friesian-Hereford calves were run on independent farmlets from January to December, over each of two years. All mobs were routinely treated with a pour-on formulation of eprinomectin every six weeks, which controlled parasites other than Cooperia.

Confirmation of ivermectin resistance in Ostertagia ostertagi in cattle in New Zealand.

Six suspected cases of ivermectin resistance in Ostertagia spp. in cattle were investigated after routine anthelmintic efficacy testing on commercial farms. On four farms a comprehensive faecal egg count reduction test (FECRT) was undertaken using oral formulations of ivermectin (0.

The efficacy and plasma profiles of abamectin plus levamisole combination anthelmintics administered as oral and pour-on formulations to cattle.

In phase I, faecal egg count reduction tests (FECRT) were conducted on six commercial cattle farms to compare the performance of two pour-on and one oral combination anthelmintic. Groups of 12-15 calves were sampled for faecal nematode egg count (FEC) before treatment with either abamectin oral, levamisole oral, an abamectin+levamisole oral combination or one of two abamectin+levamisole combination pour-ons. Samples were collected again 14days after treatment to calculate the percentage reduction in FEC.

Evidence for reversion towards anthelmintic susceptibility in Teladorsagia circumcincta in response to resistance management programmes.

Maintaining production and economic viability in the face of resistance to multiple anthelmintic actives is a challenge for farmers in many countries. In this situation, most farmers in New Zealand rely on the use of combination products, containing multiple actives with similar spectra of activity, in order to maintain control. However, there are concerns that use of combinations, once resistance has already developed to the individual actives, could rapidly lead to complete failure of all actives.

The distribution and anthelmintic resistance status of Trichostrongylus colubriformis, T. vitrinus and T. axei in lambs in New Zealand.

Aim: To determine the distribution of the three common Trichostrongylus spp. infecting sheep and their resistance status on farms throughout New Zealand, using PCR.

Methods: Cultures were prepared from faecal samples from 70 farms while conducting faecal egg count reduction tests (FECRT) in lambs between 2010 and 2012.

The in vitro response of field strains of sheep blowflies Lucilia sericata and L. cuprina (Calliphoridae) in New Zealand to dicyclanil and triflumuron.

Aim: To evaluate the in vitro efficacy of triflumuron and dicyclanil against field strains of Lucilia sericata and L. cuprina in New Zealand to establish whether anecdotal reports of declining protection periods afforded by dips containing these active ingredients had validity.

Methods: Strains of field-derived blowflies (Lucilia cuprina and L.

Managing anthelmintic resistance--use of a combination anthelmintic and leaving some lambs untreated to slow the development of resistance to ivermectin.

A field study was conducted to test the hypotheses that use of a combination anthelmintic and/or increasing the pool of unselected worms 'in refugia' by leaving a proportion of lambs untreated would slow the development of resistance to ivermectin. Twelve suites of four paddocks (farmlets) were seeded with a mixture of resistant and susceptible isolates of both Trichostrongylus colubriformis and Teladorsagia (Ostertagia) circumcincta calculated to yield a 95% reduction in faecal nematode egg count (FEC) after treatment with ivermectin. Each year for three years the farmlets were stocked in the spring with mobs of lambs which were treated five times at 28-day intervals with either ivermectin or an ivermectin+levamisole combination.

The production cost of anthelmintic resistance in lambs.

The economic impact of anthelmintic resistance was investigated in lambs by comparing productivity parameters in groups of animals treated either with a highly effective anthelmintic, or an anthelmintic to which three species of resistant worms were known to be present. Ten farmlets, each stocked with 30 lambs, were rotationally grazed for 5 months, with monthly treatments of either albendazole, to which resistance existed, or a new combination product containing derquantel and abamectin (DQL-ABA) to which there was no resistance. Stock on five farmlets were treated with each anthelmintic and productivity measures, including liveweights, body condition and faecal soiling were assessed throughout.

Dynamics of the free-living stages of sheep intestinal parasites on pasture in the North Island of New Zealand. 2. Weather variables associated with development.

Aim: To identify weather variables associated with the development of eggs of Teladorsagia (=Ostertagia) circumcincta, Trichostrongylus colubriformis and Haemonchus contortus to third-stage infective larvae (L3) under a range of climatic conditions on pasture in the North Island of New Zealand.

Methods: Sheep faeces containing known numbers of eggs of all three nematode species were deposited on, or buried in, pasture plots at three sites, viz coastal Manawatu, Upper Hutt Valley, and East Cape hill country. Development was measured by recovering L3 from faeces, herbage and soil 28-31 days after deposition, on 13-18 occasions between January 2005 until July 2006.

Dynamics of the free-living stages of sheep intestinal parasites on pasture in the North Island of New Zealand. 1. Patterns of seasonal development.

Aim: To describe the seasonal pattern of development of third-stage infective larvae (L3) from eggs of Teladorsagia (=Ostertagia) circumcincta, Trichostrongylus colubriformis and Haemonchus contortus on pasture in the North Island of New Zealand.

Methods: Sheep faeces containing known numbers of eggs of all three nematode species were deposited on, or buried in, pasture plots at three sites, viz coastal Manawatu, Upper Hutt Valley, and East Cape hill country. Development was measured by recovering L3 from faeces, herbage and soil 28-31 days after deposition on 13-18 occasions, between January 2005 and July 2006.

Development and spatial distribution of the free-living stages of Teladorsagia circumcincta and Trichostrongylus colubriformis on pasture: a pilot study.

Aims: To measure the development of Teladorsagia (=Ostertagia) circumcincta and Trichostrongylus colubriformis eggs to third-stage infective larvae (L3) at different times of the year. Also, to measure the spatial distribution of L3 across herbage, soil and faeces, in order to assess whether spatial issues could be important in larval dynamics on pasture.

Methods: Field plots were contaminated with sheep faeces containing approximately 20,000 eggs of each of T.