Control Of Parasitic Nematodes Research Articles

Strategic use of anthelmintics for parasitic nematodes in cattle and sheep.

Treatment regimes for the control of parasitic nematodes in cattle and sheep are reviewed. The advantages and disadvantages of each strategy are outlined and the veterinarian's judgement of the management and economic constraints involved when recommending a particular system to a client is emphasised.

Effect of strategic anthelmintic treatment and pasture management on productivity and control of nematode parasites in weaner-yearling beef cattle

Three groups of 17 beef calves were used to evaluate effects of strategic anthelmintic treatment on safe (group 1) and contaminated (group 2) pasture in comparison with minimal treatment at weaning and contaminated pasture (group 3). The investigation extended from weaning in November 1982 to the following August. Results of faecal egg counts, herbage larval counts, plasma pepsinogen and tracer calf worm counts in autumn and spring indicated minimal levels of infection on safe pastures provided in November and April (group 1). A decided weight gain advantage for group 1 was achieved from November to April, but the rate of gain was not consistent after April and transfer to the second safe pasture. Final average weights in late August were: group 1, 368 kg; group 2, 336 kg; group 3, 262 kg. All were significantly different (P less than 0.05). Worm counts from representative yearlings in September revealed low to moderate levels of Ostertagia ostertagi in group 1. In contrast group 2 cattle had large, almost exclusively O ostertagi infections; group 3 cattle had exceedingly high levels of Trichostrongylus axei infection and moderate to high levels of O ostertagi. Marginal evidence of type 2 ostertagiasis was observed in individual animals of group 2 and group 3.

Detection of benzimidazole resistance in trichostrongylid nematodes

Benzimidazole anthelmintics (Box 1) have an important role in the control of economically-important nematode parasites of sheep and other ruminants. But effective control and management strategies using such compounds require a clear appraisal of the resistance or susceptibility of the target worms. Currently available tests for benzimidozole resistance in trichostrongylid nematodes tend to be costly, time-consuming and technically-demanding — as a result, attention is now turning to biochemical assays.

Anthelmintic resistance and the future for roundworm control

Anthelmintic resistance has emerged as the most important problem confronting the successful control of nematode parasites of grazing animals. Although the significance of the problem varies between, and within, countries and farming enterprises, there is little likelihood that it will disappear of its own accord. On the contrary, it is reasonable to assume that it will increase if there is no change in traditional methods of parasite control. Although progress is being made in non-chemotherapeutic methods of control, these are unlikely to provide any practical alternatives in the short-term future. Nor can the pharmaceutical industry be expected to solve the problem because of the long period and the exceedingly high costs involved in bringing a completely new class of drug on to the market. The answer must lie in carefully husbanding the currently available anthelmintics, by providing farmers with programs which give good levels of parasite control and maintain high productivity in animals with fewer anthelmintic treatments. To be enthusiastically adopted by farmers, the programs require a commitment by both research and advisory workers. Such success can be achieved, as exemplified by the “Drenchplan” and “Wormkill” programs in Australia. It behoves workers in all countries which have a significant grazing livestock industry, not only those with an existing resistance problem, to consider how such schemes could be implemented.

Grazing management and nematode parasite control in cattle in the temperate climatic zone of Australia

Over 2 years, 1979 and 1981, yearling cattle were grazed from July to December/January on phalaris- or annual ryegrass-based pastures that had been previously grazed by either weaners, cows or cattle drenched every 2 weeks. All yearlings had previously been drenched at weaning in autumn, and from July were either set-stocked, or moved once or twice on to pastures previously grazed by cows. The experiment was conducted at Ginninderra. near Canberra. If a portion of the pasture was saved in winter for grazing in early spring, increased liveweight gains were observed while yearlings grazed the saved area. However, the greater gains during this period were not enough to compensate for previous weight losses or lower gains, so that saving pasture was no better than set-stocking over the total period. In 1979, a year of low rainfall and pasture growth, yearlings drenched 2-weekly gained no more weight than undrenched yearlings, despite much lower worm burdens. In 1981, with average pasture growth, yearlings drenched in July before moving on to pastures previously grazed by cows, and drenched again in September, gained as much weight as those drenched every 2 weeks and significantly more than those undrenched and set-stocked. It is recommended that weaners or yearlings should be moved in July on to improved pastures of low infectivity (obtained by previous grazing with cows or sheep). If combined with one or two drenches, this single move would be as effective for optimising weight gains as more complicated management schemes.

Comparison of Some Nematicides onVitis viniferacv. Sultana in Victoria, Australia

Five nematicides were tested in established Sultana vineyards on sands to sandy loams for control of parasitic nematodes and effects on growth and yield of the vines. Different formulations and application times and rates were used in four experiments between 1979 and 1983. Only 1,2-dibromo-3-chloropropane (DBCP) consistently reduced soil populations of <i>Meloidogyne javanica</i> (Treub) Chitwood and <i>Tylenchulus semipenetrans</i> Cobb, but aldicarb was effective against <i>M. javanica</i> over two years. Phytotoxicity symptoms were obvious on oxamyltreated vines in 1982, and yields and berry acidity were reduced. Fenamiphos reduced nematode numbers in two experiments and ethoprop in one, but no non-volatile nematicide increased vine growth or yield.

Nematode parasite control in weaner cattle on the Northern Tablelands of New South Wales

An indication of the extent to which parasite infection can limit production in yearling cattle was studied by comparing a monthly treatment with cambendazole with non-treated control cattle. In the same experiment the technique of limiting parasite infections by alternate grazing of pastures by sheep and cattle was studied. Growth rate of monthly treated cattle (0.667 kg day-1) was significantly (P &lt; 0.05) greater than for untreated cattle (0.421 kg day-1) over the 12-month period of the trial. The mortality of 12.5% in untreated animals was avoided by regular treatment. These two factors resulted in a marked financial advantage to monthly treated cattle. Ostertagia ostertagi, as the major nematode involved, produced production losses primarily in the spring and early summer periods. The alternation of sheep and cattle grazing gave an advantage over set stocked cattle in both liveweight gain and financial returns, but did not prevent mortalities in untreated cattle.

A New Approach to the Control of Toxocara Canis and other Parasitic Ova on Concrete-Floored Kennel Runs

SUMMARY The use of a horticultural flame-gun (Sheen Nottingham Ltd) was found to reduce the number of parasitic ova on the concrete floor of a kennel run in constant use. The results over a period of 12 months indicated that it was an effective means for control of parasitic nematodes.

In Vitro Study of Toxicity of Soluble Sulphides To Three Nematodes Parasitic On Rice in Senegal

Toxicity of sulphides to three species of nematodes parasitic on rice from Senegal (Hirschmanniella oryzae, H. spinicaudala and Tylenchorhynchus mashhoodi) was studied in vitro using three different methods. A Sulphide Time Unit (STU) was defined related to the average concentrations of sulphides and their variations during the tests. With hydrogen sulphide dissolved in water, the very low pH increased nematode mortality. When hydrogen sulphide was dissolved in a buffered medium used for bacterial culture, mortality was lower but a shock effect appeared due to sudden contact with high concentrations of sulphides and toxicity of some of the components of the medium. When hydrogen sulphide was produced by sulphate reducing bacteria a similar shock effect was still observed, but only when high concentrations were reached within 1 or 2 days: in such experiments nematodes were killed by low STU, and differences were observed in resistance of the three species. However, when sulphide accumulated more slowly, i.e., when lethal concentrations were reached in 3 or more days, the sensitivity of the three species was similar: 50% mortality was obtained at about 120-130 STU. The possibility of using sulphate reducing bacteria for biological control of parasitic nematodes of rice is discussed.

Control of nematode parasites by grazing management—I. Decontamination of cattle pastures by grazing with sheep

Between December and June, six paddocks that had been contaminated naturally with infective larvae of nematode parasites of cattle, were each subjected to one of six grazing treatments. The effects of these treatments on the infectivity of the pastures were assessed by slaughter and total worm counts of calves which subsequently grazed the paddocks, and by counts of larvae on pasture samples. Grazing by sheep during autumn resulted in reduced populations of Ostertagia ostertagi and Trichostrongylus axei, both in calves and on the pasture for up to 12 months after treatment. Similar effects were noted on pasture grazed by cattle repeatedly dosed with anthelmintics, and on ungrazed pasture. There was little effect of any treatment on numbers of Cooperia oncophora. It was concluded that the level of autumn contamination was of importance in determining the numbers of O. ostertagi in the following spring and summer.

Control of nematode parasites by grazing management—II. Decontamination of sheep and cattle pastures by varying periods of grazing with the alternate host

Commencing in December 1970, paddocks of a uniform series of sheep pastures were grazed for 6, 12 or 24 weeks by either yearling steers is or yearling ewes. Cattle pastures were treated similarly. All ewes and steers were pre-dosed with anthelmintic. At the conclusion of alternate grazing the effectiveness of the grazing treatments was evaluated by grazing each paddock for 1 month with either ten worm-free lambs (sheep pastures) or three wormfree calves (cattle pastures). The test animals were then slaughtered for total worm counts. The grazing of sheep pastures with cattle for 6, 12 or 24 weeks from December onwards resulted in reductions in numbers of Haemonchus contortus and Trichostrongylus colubriformis in test lambs. In comparison with continuous grazing by sheep, Nematodirus spp was only reduced after 24 weeks grazing by cattle. Cattle pastures grazed by sheep for 6 weeks showed no reduction in numbers of Ostertagia ostertagi or Cooperia oncophora in test calves. However after 12 weeks with sheep, numbers of O. ostertagi though not C. oncophora were reduced and after 24 weeks of alternate grazing both these species were reduced. Calves following the 6 week sheep treatments acquired both Haemonchus contortus and Trichostrongylus colubriformis and the calves from the 12 week sheep treatment paddock also carried H. contortus. For sheep the only evidence of cross-transmission was the occurrence of small numbers of Cooperia oncophora in test lambs from the 24 week cattle grazing treatment. The results provide evidence that sequential stocking with cattle and sheep in conjunction with anthelmintic treatment is an effective management strategy for preparing parasitologically safer pastures, but further information is required to determine the optimum timing of sequential stocking in farming situations.

Losses and frequency characteristics of piezoelectric receiving transducers : Grishchenko, E.K., 19 (September – October 1973) 114–117

The scale of the damage worldwide to human health, animal health and agricultural crops resulting from parasitic nematodes, together with the paucity of treatments and the threat of developing resistance to the limited set of widely-deployed chemical tools, underlines the urgent need to develop novel drugs and chemicals to control nematode parasites. Robust chemical screens which can be automated are a key part of that discovery process. Hitherto, the successful automation of nematode behaviours has been a bottleneck in the chemical discovery process. As the measurement of nematode motility can provide a direct scalar readout of the activity of the neuromuscular system and an indirect measure of the health of the animal, this omission is acute. Motility offers a useful assay for high-throughput, phenotypic drug/chemical screening and several recent developments have helped realise, at least in part, the potential of nematode-based drug screening. Here we review the challenges encountered in automating nematode motility and some important developments in the application of machine vision, statistical imaging and tracking approaches which enable the automated characterisation of nematode movement. Such developments facilitate automated screening for new drugs and chemicals aimed at controlling human and animal nematode parasites (anthelmintics) and plant nematode parasites (nematicides).

Control of Plant Parasitic Nematodes Associated with Cotton

Field trials with DD, DBCP, EDB, Nemaphos and VC-13 were laid out durind the winter seasons of 1965-68 on MCU 1 and MCU 3 cotton at the Agricultural College and Research Institute at Coimbatore for the control of nematode parasites of cotton. DD. EDB and VC-13 were applied a month beforo raising the crop, while, Nemaphos was applied 15 days after sowing. DBCP was tried as pre and post treatment nematicide in different concentrations. Though significant reduction was noticed population Immedi.. ately after application of nematicides, the population increased to a high level from post planting period in all the treatments and was significantly more In the case of DD followed by VC-13. Higher yield of kapas was realised in treated plots. The maximum yield was registered in DD followed by DBCP.

Response of Young Holstein-Friesian Heifers to Phenothiazine and Diethylstilbestrol

A 2×2 factorial experiment with 48 Holstein heifers was conducted over a 2-yr period to study the effects of adding 10mg diethylstilbestrol (DES); 1.5g phenothiazine; or 10mg DES and 1.5g phenothiazine to the daily ration of young heifers on growth response and control of internal nematode parasites. When phenothiazine alone was added to the control ration, rate of gain was lowered. When either 10mg DES or 10mg DES and 1.5g phenothiazine was added to the control ration, the increases in rate of gain were highly significant. Average daily rates of gain in pounds for the four groups were 1.73, 1.67, 2.07, and 2.05 for the control, phenothiazine, DES, and combination groups, respectively. Decreases in fecal egg counts as a result of feeding phenothiazine were highly significant.

PREDACEOUS FUNGI: A POSSIBLE METHOD OF BIOLOGICAL CONTROL OF PARASITIC NEMATODES.

A predaceous fungus, Acrostalagmus sp., was found attacking the larvae of Haemonchus contortus in cultures of sheep faeces. An attempt to propagate the fungus in maize meal and infect cultures of faeces was unsuccessful. Administration to sheep of material from faecal cultures containing the fungus gave inconclusive results. The possible use of fungi of this type, which attack their prey by penetration of the cuticle after spores have become adherent, as a means for biological control of nematode parasites is briefly discussed.