Influence of sustained deworming pressure on the anthelmintic resistance status in strongyles of sheep under field conditions.

Anthelmintic resistance (AR) status in Madras Red sheep from selected field flocks of a government funded scheme, covered by regular, sustained anthelmintic treatment for more than 10 years was determined. Parameters such as fecal egg count reduction test (FECRT), larval paralysis assay (LPA), and allele-specific-PCR (AS-PCR) were used to test the efficacy of fenbendazole, tetramisole, and ivermectin at recommended doses, in two seasons. Sheep belonging to non-beneficiary farmers were used as controls. Mean FECRT values of beneficiary group during winter and summer seasons were 77.77 and 76.04, 93.65 and 92.12, and 95.37 and 98.06 %, respectively, for fenbendazole, tetramisole, and ivermectin. In the non-beneficiary groups, the corresponding values were 74.82 and 81.09 %, 96.05 and 97.40 %, and 97.26 and 98.23 %, respectively. The results revealed resistance to fenbendazole, suspect resistance to tetramisole and susceptibility to ivermectin in beneficiary flock. In non-beneficiary flock, while resistance was noticed against fenbendazole, both tetramisole and ivermectin were effective. FECR values were found to be significantly different between beneficiary and non-beneficiary groups against tetramisole. The results of LPA confirmed this finding, as 50 % of the Haemonchus contortus larvae were paralyzed at the concentration of 0.0156 µg/ml in the beneficiary group, while those of non-beneficiary groups required lower concentrations of 0.0078 µg/ml. AS-PCR revealed the predominance of heterozygous susceptible population of H. contortus in the beneficiary group. In this study, resistance to fenbendazole was confirmed in both the beneficiary and non-beneficiary groups and this could be attributed to frequent use of benzimidazoles as seen from the deworming records. Emergence of tetramisole resistance was detected in the beneficiary group, where the drug was used continuously for 4 years. Ivermectin was found to be effective in all the flocks. It is recommended that the practice of routine deworming of three to four times a year should be avoided, as it can lead to emergence of anthelmintic resistance.

Efficacy of tetramisole and dichloroxylenol against Syngamus trachea in pheasants and turkeys.

Two water soluble products currently recommended for the treatment of syngamiasis were tested in pheasants and turkeys. Dichloroxylenol (Rotgape; Adams & Moulson), was found to have no efficacy. Although tetramisole (Game Bird Wormer; ICI) administered in drinking water had a moderate efficacy against three- and four-day-old larvae (47 to 71 per cent), its level of efficacy against infections associated with disease, those of seven days and older, was poor (5 to 29 per cent). It is concluded that neither product is likely to be of value in field outbreaks of syngamiasis.

Influence of anthelmintic treatment on the liveweight of outwintered ewe hoggs.

Three systems of outwintering ewe hoggs are normally practised on Scottish hill farms. A series of field trials involving some 2000 different animals was conducted to determine the response in liveweight from anthelmintic treatment for roundworms. The results suggest that, under field conditions, a strategic dosing programme using a modern anthelmintic can prevent liveweight loss in ewe hoggs wintered either on the hill or "inbye". The best response may be expected from a two dose regime--one in early winter (mid October to mid November) and the other in winter (mid January to mid February). In away-wintered hoggs, the kinder climate, better pssture, and, in the vast majority of cases, less contaminated ground, appear to outweigh the advantages of dosing after the late autumn.

[Tetramisol, piperazine, and metrifonate treatment of experimental invasion by Ascaridia galli in chickens of differents ages]. / Lécba umelé invaze Ascaridia galli u ruzne starých kurat tetramisolem, piperazinem a metrifonátem

The authors studied the anthelminthic effectiveness of a single peroral application of tetramisol (40 mg per 1 kg 1. w.), piperazine (500 mg per 1 kg 1. w.) and metriphonate (50 mg per 1 kg 1.w.) in the artificial invasion by Ascaridia galli. A set of 118 chickens of the White Leghorn breed were subjected to a single invasion by 3000 or 1500 invasive eggs at the age of 6, 36, and 48 days. The inteseffectiveness and extenseffectiveness of the treatment with the tested preparations were examined on the fifteenth day after invasion; the examination was based on the findings of ascarids in the helminthological dissection performed 48 hours on the findings of ascarids in the melminthological dissection performed 48 hours after therapy. The numbers of ascarids in the tested animals were compared with those in the controls. A histological examination was carried out to study the tissue reaction in the intestine, liver, spleen, kidneys, heart, and brain. Tetramisol showed the highest effectiveness. The intenseffectiveness of this substance reached 89-100% in young as well as older chickens. Piperazine had a good effectiveness in older chickens (61-83%); in young chickens it was entirely ineffective. The intenseffectiveness percentage of metriphonate was almost at a zero level. The extenseffectiveness of tetramisol ranged between 20 and 100% (the low values are characteristic of a severe course of invasion). Piperazine showed an extenseffectiveness ranging from 17 to 67% only in older chickens in cases of a mild invasion; otherwise it was equal to zero. Metriphonate was entirely ineffective. The reflection of ascaridiasis in the tissue reaction of the host manifested itself as granulomatous changes in intestinal mucous membrane, as multiplied histiocytic elements and plasma cells, and inflammatory lymphocytic infiltrates in the liver parenchyma.

[Pathological changes in the tissues of the helminth Thominx phasianina after the single administration of tetramisole]. / Patologicheskie izmeneniia tkanei gel'minta Thominx phasianina posle odnokratnogo vvedeniia tetramizola.

A single dose (0.2 g/kg) of 20% tetramisole granulate to pheasants infected with Thominx phasianina resulted in intestinal helminth elimination in 72 hours. Structural injuries of the helminth cutaneomuscular sac, digestive and sexual system were detected, manifesting 6 h after the injection and reaching their peak 24 h after it. The mitochondria and endoplasmic reticulum of middle intestinal wall, uterus, oviduct epitheliocytes, oogonia, and oocytes of nematodes were found the most sensitive to the drug.

[Toxicity of "Farmakhim" tetramisole in laboratory and farm animals]. / Prouchvaniia vurkhu toksichnostta na tetramizol "Farmakhim" pri laboratorni i selskostopanski zhivotni.

Tetramisole produced by ICI, England, and Tetramisole Pharmachim, Bulgaria, were comparatively studied in terms of their acute and subchronic toxicity, and the local and general tolerance and antinematode activity. No differences were found in their acute toxicity (LD50) for albino mice at oral, subcutaneous, and venous application, the index of resorption being 6.3. The same was true so far as the tolerance in calves, sheep, goats, and pigs was concerned. Orally at the rate of 45 mg/kg in sheep and over 30/kg with calves (3, resp., 2 times as high as the therapeutic dose) tetramisole produced nervous and locomotor excitement, tremor, salivation, higher respiration and pulse rate, frequent urination and defecation. Following the tenfold oral administration at intervals, of 3 days at rates of 15 and 45 mg/kg tetramisole Pharmachim did not affect unfavourably the appetite, behaviour, general status, and the clinical and biochemical composition of the blood as well as the structural pattern of the viscera in sheep. Tetramisole Pharmachim was shown to be well tolerated with regard to the conjunctivae at concentrations of up to 5 per cent, the subcutaneous tissues and muscles at conc. of up to 3 per cent, and mucous membranes of the stomach and intestines at conc. of up to 10 per cent.

Treatment of Nippostrongylus brasiliensis in normal and SPF rats using tetramisole loaded into zeolite.

Administration to rats of tetramisole loaded into zeolite was more successful in killing adults of Nippostrongylus brasiliensis than the administration of tetramisole alone. The most successful treatment occurred in SPF (Specific Pathogen Free) rats dosed with tetramisole loaded into zeolite and no worms were present in this group at autopsy eight days post-infection. It is concluded that the slow release of drug from the zeolite matrix improved its efficacy, especially in removing worms from low-grade infections.

Effect of periodic deworming on nutritional status of ascaris-infested preschool children receiving supplementary food.

The weight for age of 154 undernourished preschool children in an ascaris-infested community receiving supplementary food was monitored for a year. 74 children were given tetramisole every 4 months, while 80 controls were given placebo. The prevalence of ascaris (roundworm) infection and the severity of protein-energy malnutrition were the same in the two groups at the onset of the study. Stool-positive rates for ascariasis came down significantly in the experimental group during the year, but eradication of the worm was not possible owing to constant re-exposure. Nutritional status remained unaltered in the controls but improved strikingly in the treated children 8 and 12 months after the start of the study. Periodic deworming should form a part of the supplementary feeding programme if malnutrition is associated with ascariasis in the community.

Stimulation of anti-Brucella vaccination in mice by tetramisole, a phenyl-imidothiazole salt.

The effect of tetramisole (hydrochloride of racemic 2, 3, 5, 6,-tetrahydro-6-phenyl-imidazo [2, 1-b] thiazole) on immunization was investigated in mice vaccinated by killed Brucella melitensis cells suspended in incomplete adjuvant. Immunity to Brucella abortus challenge was estimated by the reduction in number of B. abortus colonies per gram of spleen in those mice which escaped full immunization and also by calculation of mean infective doses for each group of mice. All tetramisole treatments significantly reduced the number of B. abortus live cells in spleen from infected mice. Tetramisole, injected twice (at the time of vaccination and 48 h later), induced a significant 3.5-fold increase of the protection brought about by Brucella vaccine alone. A single injection of 1.25 mg/kg at the time of vaccination resulted also in a significant increase of the immunity given by vaccination. No modifications of the vaccine potency were observed if tetramisole administration preceded vaccination. In such a mouse assay, tetramisole-induced stimulation was not accompanied by specific antibody increases, although measured by three serological tests.

Anticancer activity of isomers of 6-phenyl-2,3,5,6-tetrahydroimidazo[2,1-b]thiazole.

Three phenylimidazothiazole isomers, L-(-)-form (levamisole), D-(+)-form (dexamisole), and DL-(+/-)-form (tetramisole), modulate mouse and rat immune responsiveness. They depress the relapse of urinary bladder cancer, BC-47, when they are used with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) for treatment of rats bearing BC-47. Levamisole was the most effective isomer. Effectiveness of the isomers is expressed by their ability to enhance the number of plaque-forming cells to sheep red blood cells. They also stimulate the DNA synthesis of murine lymphocytes in vitro.

Comparative anthelmintic activity of strategic sustained low-level administration of albendazole in feed pellets compared to single doses of closantel and tetramisole against natural ovine parasitic gastroenteritis.

The strategic use of single therapeutic doses of closantel, tetramisole or sustained low-level administration of albendazole in feed pellets in controlling naturally acquired parasitic gastroenteritis in sheep was investigated on a farm in semi-arid Rajasthan, India. A total of 303 5- to 6-month-old sheep were divided into three groups. Two groups were dosed with single therapeutic doses of closantel and tetramisole and the third group was given a low-level medication with albendazole through feed pellets for 30 days. Faecal egg counts revealed significantly lower counts (p<0.001) in the group treated with closantel compared to the other two groups. The faecal egg counts in the group receiving sustained low-level albendazole rose after withdrawal of the medication but remained significantly lower than those in the group treated with tetramisole up to 7 weeks after treatment (p<0.05). On the other hand, in the group treated with tetramisole, the mean faecal egg count rose from 3 weeks after treatment and remained continuously higher than those in any other group up to 12 weeks after treatment. The closantel-treated group gained more body weight but the first six-monthly greasy fleece yield was greater in the group treated with medicated pellets. During the first 3 months of the experiment, three animals in the group treated with tetramisole died of parasitic gastroenteritis. Following sustained low-level administration of albendazole in feed pellets, the plasma disposition curve of both the sulphoxide and sulphone metabolites reached its plateau level by day 5 and remained almost constant thereafter. The comparative cost-effectiveness of the three treatment regimes during the first 3 months of treatment was best for the group treated with closantel followed by the group treated with medicated feed pellets.