nitrophenols and Haemonchiasis

This paper describes an exceptional spectrum of multiple anthelmintic resistance in two strains of Haemonchus contortus in South Africa, one from Howick in KwaZulu-Natal, and the other from Badplaas, in Mpumalanga. Apparently for the first time, a helminth strain is described with resistance to compounds from all five of the modern anthelmintic groups used for nematode control in sheep; also, two strains of H. contortus show resistance to the two substituted phenols, dinitrophenol and nitroxynil. Only closantel at 5 mg kg-1 of nine compounds tested appears to have undiminished efficacy against the Howick strain, but even in the case of closantel, the residual activity and minimal effective level need to be tested before it can be concluded that its efficiency is unaffected. The exceptional resistance of the Howick strain is demonstrated by the fact that sequential daily drenching of sheep infected with the strain, with levamisole at 18 mg kg-1, oxfendazole at 20 mg kg-1, levamisole at 20 mg kg-1 and a mixture of fenbendazole at 10 mg kg-1 plus trichlorfon at 132 mg kg-1 on the fourth day, failed to clear sheep of the infection. There are strong indications that side-resistance occurs between dinitrophenol and nitroxynil, on the one hand, and the salicylanilides, on the other, and it is suggested that, before long, strains of H. contortus will be found with high levels of resistance to all the currently available anthelmintics.

Topics: Animals; Antinematodal Agents; Drug Resistance, Multiple; Female; Haemonchiasis; Haemonchus; Male; Nitrophenols; Nitroxinil; Salicylanilides; Sheep; Sheep Diseases; South Africa

Topics: Albendazole; Animals; Anthelmintics; Brazil; Drug Resistance, Multiple; Feces; Fenbendazole; Haemonchiasis; Haemonchus; Ivermectin; Levamisole; Nematoda; Nematode Infections; Nitrophenols; Parasite Egg Count; Salicylanilides; Sheep; Sheep Diseases; Trichostrongylosis; Trichostrongylus

Topics: Administration, Oral; Animals; Anthelmintics; Benzimidazoles; Drug Resistance; Feces; Fenbendazole; Haemonchiasis; Haemonchus; Injections, Subcutaneous; Ivermectin; Nitrophenols; Nitroxinil; Parasite Egg Count; Salicylamides; Salicylanilides; Sheep; Sheep Diseases; Time Factors; Trichostrongyloidea; Trichostrongyloidiasis

Topics: Animals; Benzimidazoles; Drug Resistance; Feces; Haemonchiasis; Haemonchus; Nitrophenols; Nitroxinil; Parasite Egg Count; Sheep; Sheep Diseases; Trichostrongyloidiasis

Sheep grazed on natural pastures heavily infested with infective larvae of Haemonchus contortus. Sixty-eight weaned Merinos were divided into 6 groups on Day 0 (23 November 1977), and on Day +14 (7 December) 79 Merinos were divided into 7 groups. There were 2 groups of undosed controls and other groups were either dosed with infective larvae of Trichostrongylus axei (bovine strain) only on Days 0 and +14, or in combination with H. contortus, or with subsequent doses of H. contortus, 28 days later. One group (Group 12) was dosed with T. axei and treated with a subcutaneous injection of di-iodonitrophenol (DNP) on Day +14. With the exception of 2 sheep, the sheep of the first 6 groups survived until slaughter in March and April 1978, while many sheep (43) of the latter 7 groups died or were killed in extremis from March-May. T. axei dosed on 23 November (Day 0) protected Group 2 by greater than 50% in greater than 50% of sheep. In the latter 7 groups the best results were achieved when DNP was combined with predosing with T. axei. The poor results were probably due either to delayed predosing with T. axei or a massive challenge in the wettest summer on record.

Topics: Animals; Cattle; Feces; Haemonchiasis; Haemonchus; Host-Parasite Interactions; Nitrophenols; Parasite Egg Count; Sheep; Sheep Diseases; Trichostrongyloidea; Trichostrongyloidiasis; Trichostrongylosis

A subcutaneous injection of 2,6-diiodo-4-nitrophenol (Disophenol) at 10 mg/kg sheep leaves a residue bound to serum albumin which is lethal to Haemonchus contortus for 3 months after treatment. In the larval anthelmintic test, susceptible worm free sheep are dosed so that either third stage larvae (L3), or fourth stage larvae (L4) or 5th and adult stages are present on the day of treatment but slaughter is delayed to allow these larval stages to develop to adults because the larger worms are more easily seen, identified and counted. The larval anthelmintic test in sheep had to be altered and sheep killed within a few days of treatment, because the residues may be more effective against subsequent stages of development. Disophenol was greater than 60% effective against L3 of Oesophagostomum columbianum and L4 of H. contortus in greater than 60% of sheep (Class B). It rose to greater than 80% effective against adult H. contortus in greater than 80% of sheep (Class A). Against H. contortus it maintained Class A for 32 days, fell to Class B from 45--76 days and Class C (greater than 50% effective in greater than 50% of sheep) at 91 days after treatment respectively. In the RSA a treatment in December followed by another in March would protect sheep adequately against H. contortus for the entire season.

Topics: Animals; Anthelmintics; Delayed-Action Preparations; Drug Evaluation; Feces; Haemonchiasis; Helminthiasis; Helminthiasis, Animal; Larva; Nitrophenols; Oesophagostomiasis; Parasite Egg Count; Sheep; Sheep Diseases

Two long-acting anthelmintics, closantel and disophenol, were tested by treatment 90, 60 and 30 days before challenge with a thiabendazole selected laboratory strain of Haemonchus contortus. The sheep were slaughtered 28 days after infection for total worm counts. A significant reduction in the number of adults remaining at autopsy was recorded after treatment with both anthelmintics 30 and 60 days before challenge but there was zero efficacy when the animals were treated 90 days before challenge. No significant difference was exhibited between the two compounds. Variability in response was recorded between animals on the 60 day period of treatment, which for disophenol may be dose related because animals receiving the lower volumes showed higher worm counts. For both anthelmintics a variability in the rate of metabolism may be responsible. The possibility offered by both anthelmintics for treating benzimidazole resistant strains of H contortus is discussed.

Topics: Animals; Anthelmintics; Drug Resistance; Haemonchiasis; Haemonchus; Nitrophenols; Salicylamides; Salicylanilides; Sheep; Sheep Diseases; Thiabendazole; Trichostrongyloidiasis

A group of 12 10-month-old, worm-free Merino lambs were given a single injection of disophenol at 10 mg/kg. This group and another group of 12 worm-free lambs were infested with infective larvae of Haemonchus contortus 1-3 times a week with a maximum dose of 4000/week from 0-91 days. From 95-168 days the dose was increased to a maximum of 6000/week. Every 7 days faeces were examined for worm eggs and blood samples for haematocrit (Ht). Worm egg counts in the controls rose from 21-56 days, fluctuated, and rose to another peak at 84 days, while the Ht fell from 28 days to rise again after 105 days. In the group treated with disophenol egg counts were negative until 161 days and Ht remained at normal values throughout.

Topics: Animals; Anthelmintics; Feces; Haemonchiasis; Hematocrit; Nitrophenols; Parasite Egg Count; Sheep; Sheep Diseases; Time Factors; Trichostrongyloidiasis

Topics: Acute Disease; Animals; Haemonchiasis; Nitrophenols; Parasite Egg Count; Rain; Seasons; Sheep; Sheep Diseases; Trichostrongyloidiasis

The result of a field trial investigating the anthelmintic effect of disophenol against H. contortus in sheep raised under Asian small farming practice is reported. it was clearly shown that a single injection of disophenol suppressed the numbers of H. contortus to very low levels for periods up to 3 months despite the presence of large populations of H. contortus infective larvae available on pasture and herbage grasses.

Topics: Animals; Anthelmintics; Feces; Female; Haemonchiasis; Haemonchus; Indonesia; Male; Nitrophenols; Parasite Egg Count; Sheep; Sheep Diseases; Trichostrongyloidiasis

Disphenol was administered to sheep infected with Haemonchus contortus in order to prevent the development of populations of adult worms, and studies were made of the pathogenicity of the arrested fourth-stage larvae which remained. The treated sheep showed elevated plasma pepsinogen and abomasal pH, predominantly negative dry-matter balance, and evidence of greater fluid loss, including plasma, into the gastro-intestinal tract. It was concluded that arrested larvae may cause damage to the abomasal mucosa.

Topics: Abomasum; Animals; Haemonchiasis; Haemonchus; Larva; Male; Nitrophenols; Pepsinogens; Sheep; Sheep Diseases; Trichostrongyloidea; Trichostrongyloidiasis

Topics: Ancylostoma; Ancylostomiasis; Animals; Anthelmintics; Cats; Cattle; Dogs; Fasciola hepatica; Fascioliasis; Haemonchiasis; Haemonchus; Horses; Liver; Mitochondria, Liver; Necator; Nitrophenols; Oxidative Phosphorylation Coupling Factors; Phrenic Nerve; Poultry; Poultry Diseases; Rats; Sheep; Strongylida Infections; Strongyloidea