Prevalence of anthelmintic resistance on sheep farms in New Zealand

AIM: To establish the prevalence of anthelmintic resistance in parasitic nematodes on sheep farms in New Zealand.

METHODS: A cross-sectional prevalence study was conducted, using a standardised faecal nematode egg count (FEC) reduction (FECR) test (FECRT) for ivermectin, at a full (0.2 mg/kg) and half (0.1 mg/kg) dose rate, and albendazole, levamisole and albendazole-levamisole in combination, on 60 lambs (n=10 per group) on farms selected from throughout New Zealand. Farms that conformed with selection criteria were chosen at random (n=80) or with a history of suspected resistance to macrocy- clic lactone (ML) anthelmintics (n=32). Resistance to an an- thelmintic was inferred when there was <95% reduction in FEC 7-10 days after treatment. Larval cultures were performed for all control groups and for treated groups for which resistance was evident.

RESULTS: Of the farms randomly selected, 36% showed ≥95% FECR for all anthelmintics tested; resistance to ivermectin at 0.1 and 0.2 mg/kg liveweight was evident on 36% and 25% of these farms, respectively. Resistance to both ivermectin (0.2 mg/kg) and levamisole was evident on 8/80 (10%) farms, to ivermectin and albendazole on 10/80 (13%) farms, and to iver- mectin, levamisole and albendazole on 6/80 (8%) farms. The prevalence of resistance to a half dose of ivermectin tended to be more prevalent on farms with a history of suspected ML resistance (p=0.06). Resistance to albendazole was seen across all the main parasite genera, and to levamisole in Nematodirus, Ostertagia (= Teladorsagia) and Trichostrongylus species. Resistance to ivermectin was dominated by Ostertagia spp, although Cooperia, Nematodirus and Trichostrongylus species were also implicated.

CONCLUSION: Anthelmintic resistance in parasitic nema-todes of sheep is common in New Zealand. Not only was resistance to albendazole and levamisole common, but resistance to the ML, ivermectin, was at a higher prevalence than expected. Sheep farmers and advisors in New Zealand need to re-evaluate the way they manage parasites, and more research is urgently needed if the steady decline in anthelmintic susceptibility is to be halted.     

Acanthocephalan infection and sparganosis in a green tree snake (Dendrelaphis punctulata)

Acanthocephalan and spargana parasites were identified within a body wall mass during exploratory surgery in a wild green tree snake. Acanthocephalan parasites have not previously been reported in this species. Surgical excision, the treatment of choice, could not be achieved because of the extensive infiltration of the coelomic cavity.     

Probing the Local Effects of Magnetic Impurities on Superconductivity

The local effects of isolated magnetic adatoms on the electronic properties of the surface of a superconductor were studied with a low-temperature scanning tunneling microscope. Tunneling spectra obtained near magnetic adsorbates reveal the presence of excitations within the superconductor's energy gap that can be detected over a few atomic diameters around the impurity at the surface. These excitations are locally asymmetric with respect to tunneling of electrons and holes. A model calculation based on the Bogoliubov-de Gennes equations can be used to understand the details of the local tunneling spectra.     

Spontaneous formation of macroscopic chiral domains in a fluid smectic phase of achiral molecules

A smectic liquid-crystal phase made from achiral molecules with bent cores was found to have fluid layers that exhibit two spontaneous symmetry-breaking instabilities: polar molecular orientational ordering about the layer normal and molecular tilt. These instabilities combine to form a chiral layer structure with a handedness that depends on the sign of the tilt. The bulk states are either antiferroelectric-racemic, with the layer polar direction and handedness alternating in sign from layer to layer, or antiferroelectric-chiral, which is of uniform layer handedness. Both states exhibit an electric field-induced transition from antiferroelectric to ferroelectric.     

Organic Glasses: A New Class of Photorefractive Materials

The performance of amorphous organic photorefractive (PR) materials in applications such as optical data storage is generally limited by the concentration of active molecules (chromophores) that can be incorporated into the host without forming a crystalline material with poor optical quality. In polymeric PR systems described previously, performance has been limited by the necessity of devoting a large fraction of the material to inert polymer and plasticizing components in order to ensure compositional stability. A new class of organic PR materials composed of multifunctional glass-forming organic chromophores is described that have long-term stability and greatly improved PR properties.     

Nanofabrication of Small Copper Clusters on Gold(111) Electrodes by a Scanning Tunneling Microscope

The use of scanning tunneling microscopy in an electrochemical environment as a tool for the nanoscale modification of gold electrodes was demonstrated. Small copper clusters, typically two to four atomic layers in height, were precisely positioned on a gold(111) electrode by a process in which copper was first deposited onto the tip of the scanning tunneling microscope, which then acted as a reservoir from which copper could be transferred to the surface during an appropriate approach of the tip to the surface. Tip approach and position were controlled externally by a microprocessor unit, allowing the fabrication of various patterns, cluster arrays, and "conducting wires" in a very flexible and convenient manner.     

Congenital inguinal hernias associated with a rent in the common vaginal tunic in five foals

Five foals were admitted because of colic that developed within 24 hours after birth. Physical examination revealed swelling from the inguinal region to the cranial aspect of the prepuce. Through the skin overlying the swelling, distended loops of bowel could be palpated. The hernias could be reduced with the foals restrained in dorsal recumbency. Surgical exploration showed the swelling to be an inguinal hernia with small bowel herniation through a rent in the common vaginal tunic. Concurrent rupture of the vaginal tunic should be suspected when a congenital inguinal hernia is associated with colic, swelling that extends to the prepuce, or intestine that is easily palpated within the hernial swelling. Repeated manual reduction in these cases would be of little benefit and surgical intervention would be recommended.     

ULTRASONOGRAPHIC, GROSS, AND HISTOLOGIC EVALUATION OF A TENDINITIS DISEASE MODEL IN THE HORSE

Collagenase-induced lesions of the superficial digital flexor tendon were monitored using diagnostic ultrasound and subsequently compared with gross and microscopic findings. The postinjury sonograms demonstrated hypoechoic or anechoic areas corresponding to areas of hemorrhage and necrosis. The size of the lesion increased and the echogenicity decreased with increasing units of collagenase injected into the tendon. As postinjury time increased, echogenicity increased, which corresponded to fibrous-tissue invasion and collagen deposition. The extent of tendon injury produced correlated with the amount of collagenase injected into the tendon. Diagnostic ultrasound is useful in evaluating injury and healing in collagenase— induced tendinitis.     

Intestinal myxosarcoma in a thoroughbred mare.

A large fibrotic mass originating from the cecal base was discovered upon surgical exploration of the abdomen in a Thoroughbred mare with a history of chronic colic and weight loss. The mass protruded intraluminally resulting in partial obstruction. Surgical excision was not feasible due to the location of the mass and the inability to exteriorize it adequately from the abdominal cavity. The mass was fibrous with a shiny, gelatinous material present throughout the neoplasm. Histologically, large confluent spaces filled with mucopolysaccharides were identified by staining with Alcian blue. The diagnosis of myxosarcoma was based upon finding of atypical fibroblastic cells, mucinous stroma, local invasiveness, and metastasis to the regional lymph nodes. Myxomatous tumors have not previously been documented to occur in the equine intestinal tract.