Critical and controlled tests of activity of a macrocyclic lactone (compound F28249-alpha) against natural infections in internal parasites of equids

Thirteen critical tests (n = 11 horses and 2 ponies) and 4 controlled tests (n = 4 donkeys and 6 horses) were performed to evaluate the activity of the experimental macrocyclic lactone compound F28249-alpha against internal parasites of equids. In the critical tests, activity was determined mainly against the large parasites, but 1 critical test also included benzimidazole-resistant small strongyles. In the controlled tests, evaluation of drug activity included large parasites and stomach worms in all 4 tests, and lungworms in 2 tests. The period between treatment and euthanasia was 6 to 9 days for the critical tests and 14, 17, or 52 days for the controlled tests. The compound was administered by stomach tube at dose rates of 1, 2, 3, 3.5, or 4 mg/kg of body weight. In the critical tests, removal at all 5 dose rates was 100% for Gasterophilus nasalis (2nd and 3rd instars), Parascaris equorum (mature), Strongylus vulgaris, and Strongulus edentatus from the gastrointestinal tract. For Gasterophilus intestinalis in the stomach, mean removals of 2nd instars were 88% at the rate of 2 mg/kg and 93% to 100% at rates greater than or equal to 3 mg/kg. For 3rd instars, mean removals were 7% at 1 mg/kg, 77% at 2 mg/kg, 90% at 3 mg/kg, and 98% at 3.5 mg/kg. Discharge of G intestinalis in feces was typically a slow, prolonged process and probably higher removal values, especially at lower dose rates, would have attended a longer interval after treatment before necropsy examination.(ABSTRACT TRUNCATED AT 250 WORDS)     

An evaluation of an oral formulation of moxidectin against selected anthelmintic-resistant and -susceptible strains of nematodes in lambs

The efficacy of an oral formulation of the newly developed parasiticide, moxidectin, was tested against benzimidazole-resistant Haemonchus contortus, Trichostrongylus colubriformis, and Nematodirus spathiger, levamisole-resistant Ostertagia circumcincta, and susceptible Cooperia curticei infections in weaned lambs. Thirty-two lambs were experimentally infected with mixed doses of the above strains of nematodes. They were allocated into four treatment groups by stratified randomisation using liveweights and faecal egg counts 28 days later. One group received moxidectin at 0.2 mg/kg liveweight, one group oxfendazole at 4.5 mg/kg liveweight, one group levamisole at 7.5 mg/kg liveweight and the last group remained untreated as the control. Worm burdens in the lambs at slaughter 10 days after oral treatment confirmed the resistance status of the nematode strains used, and showed that moxidectin had a greater than 99.9% efficacy (p<0.01) against all of them. No adverse effects due to treatment with moxidectin were observed in any of the animals.     

Experimental determinations of factors affecting the sink rates of baited hooks to minimize seabird mortality in pelagic longline fisheries

• 1. An experiment was conducted in Australia's pelagic longline fishery to establish a scientific basis for the introduction of line weighting to reduce seabird mortality. The experiment examined the effects of different bait species (blue mackerel, yellow‐tail mackerel and squid), bait life status (dead or alive), weight of leaded swivels (60 g, 100 g and 160 g) and leader length (distance between leaded swivel and hooks: 2 m, 3 m and 4 m) on the sink rates of baited hooks from 0–6 m deep.
• 2. On average, live bait sank much more slowly than dead bait. The sink rates of individual live bait were highly variable: many were <2 m underwater 18 s after deployment, including some on the heaviest swivels, and some were <10 m deep after 120 s.
• 3. Within the dead bait group, all three swivel weights on 3 m and 4 m leaders sank at similar rates. Initial sink rates (e.g. 0–2 m) were 2–3 times slower than final rates (e.g. 4–6 m) for all combinations of swivel weight and leader length. The fastest initial and final sink rates were associated with heavy swivels placed close to hooks.
• 4. The results show that (a) compared with dead bait, live bait greatly increases the exposure of baited hooks to seabirds; (b) initial sink rates of dead bait are increased by placing leaded swivels close to hooks and final rates by increasing the weight of the swivels; (c) adding weight to long leaders makes little difference to sink rates; and (d) the small (incremental) changes to swivel weights and leader lengths typically preferred by industry will be difficult to detect at sea and unlikely to substantially reduce seabird mortality.
• 5. We suggest that experiments designed to reduce seabird mortality from that associated with 60 g swivels and ～3.5 m leaders (the preferred option by industry) should aim to expedite the initial sink rates as well as rates to deeper depths. This objective could be achieved by including branch lines with ≥120 g swivels ≤2 m in comparative assessments of the effectiveness of line weighting regimes in reducing seabird mortality. Copyright © 2010 John Wiley & Sons, Ltd.

     

Current prevalence of adult Uncinaria spp. in northern fur seal (Callorhinus ursinus) and California sea lion (Zalophus californianus) pups on San Miguel Island, California, with notes on the biology of these hookworms

A prevalence survey for hookworms (Uncinaria spp.) was done in northern fur seal (Callorhinus ursinus) and California sea lion (Zalophus californianus) pups on San Miguel Island, CA, in 2000. Intestines of dead pups were examined for adult hookworms in July. These parasites were found in 95% of 20 fur seal pups and 100% of 31 sea lion pups. The number of hookworms varied from 4 to 2142 (mean = 760) in fur seal pups and from 20 to 2634 (mean = 612) in sea lion pups. A direct relationship was evident between body condition and number of hookworms in the pups; that is, pups in poor condition had fewer hookworms than those in good condition. There was a decline in the number of hookworms in sea lion pups in 2000 compared to collections in 1996. Eggs of Uncinaria spp. were found in rectal feces (collected in late September and early October) of none of 35 (0%) live fur seal pups and 41 of 48 (85%) live sea lion pups. Packed cell volume values, determined for most of the same live pups, were essentially normal for C. ursinus but were much lower than normal for most Z. californianus. Hookworm larvae were not found in blubber of fur seal and sea lion pups or in rookery sand in July. Rookery sand, positive for live hookworm larvae when put in a refrigerator, was negative at removal 2.5 years later. The average number of eggs in utero of female hookworms was 285 for three specimens from a fur seal pup and 281 from three specimens from a sea lion pup. One hookworm larva was recovered from milk stripped from the teats of a stranded Z. californianus female at The Marine Mammal Center, Sausalito, CA.     

Poor anchorage and growth of spur ‘Red Delicious’ apple trees with deep crown roots

Spur ‘Red Delicious’ apple Malus domestica (Bork.) trees on MM 111 and seedlings that had been blown over by high winds had greater depth to first root and had thinner trunks than adjacent undamaged trees.     

Seminal vesicle growth induced by Ascaris suum infection

This study was designed to determine the effect of Ascaris suum infection upon growth of mouse vesicular glands. Mice were infected with varying dosages of A. suum eggs and killed after six weeks. Results indicated a dose dependent increase in seminal vesicle weight, independent of total body weight.     

Use of oxibendazole for control of cambendazole-resistant small strongyles in a band of ponies: a six-year study

Oxibendazole (OBZ; 10 mg/kg of body weight) was administered to ponies at 8-week intervals to control strongylosis in a breeding band of Shetland-type ponies (n = 29 to 50) from October 1978 through September 1984. A similar use of cambendazole (CBZ; 20 mg/kg of body weight) in this band of ponies during the preceding 4-year period resulted in the survival of a CBZ-resistant population (S) of small strongyles. Effectiveness of OBZ treatments was monitored by pre- and posttreatment counts of the number of strongyle eggs per gram of feces (epg) and of the number of strongyle larvae per gram of feces (lpg). For the first 4 years of the 6-year period, epg and lpg counts were determined for 3 to 5 of the OBZ treatments; during the last 2 years, counts were determined for each treatment. For the 1st year, the mean reduction in epg was 96%. During the 2nd and 3rd years, mean reductions in epg were 80% and 81%, respectively. For the 4th and 5th years, mean reductions in epg were 69% and 43%, respectively. For the 6th year, the mean reduction in epg was 37%. Statistical analyses of the epg data, using the linear plateau method, indicated a significant increase in residual (surviving) strongyle infections after the periodic OBZ treatments, with a mean annual increase in survival of 10.3% for the 6 years. Changes in lpg were variable, but an overall loss of effectiveness of the OBZ treatments was evident. Only infective larvae of small strongyles were observed in the cultures; larvae of 2 species of large strongyles, Strongylus vulgaris and Strongylus edentatus, were conspicuously absent.(ABSTRACT TRUNCATED AT 250 WORDS)