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PubMed1981

[Immune response in sheep experimentally infected with Haemonchus contortus, Comparative study in male and female (author's transl)].

Merino breed sheep eight months old at the beginning of the experiment and carriers of hemaglobin A were used. They were infected one or more times with H. contortus larvae and then challenged with 500 or 5000 larvae L3. Self-cure was reproduced and animals were found immune after infectation. Self-cure was more evident in females than in males and immunity was also better and appeared earlier in females than in males.

Animals↗
PubMed1981

Studies on Haemonchus contortus. IV. The effect of Trichostrongylus axei and Ostertagia circumcincta on challenge with H. contortus.

Worm-free Merino yearlings were dosed with either a mixture of infective larvae of Trichostrongylus axei and Ostertagia circumcincta or with O. circumcincta only, and challenged 90-93 days later with infective larvae of Haemonchus contortus. Neither of these methods protected sheep against challenged and slight protection was afforded sheep predosed with T. axei and O. circumcincta and challenged with a trickle dose of H. contortus.

Animals↗
PubMed1981

Studies on Haemonchus contortus. V. Chemoprophylaxis and its effect on worm egg counts and the haematocrit.

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.

Animals↗
PubMed1980

Efficacy of albendazole and levamisole in sheep against Thysanosoma actinioides and Haemonchus contortus from the Edwards Plateau, Texas.

Lambs naturally infected with Thysanosoma actinioides and naturally and experimentally infected with Haemonchus contortus were used in a controlled experiment to determine the anthelmintic activity of albendazole as compared with levamisole. The lambs were given 10,000 H contortus larvae 25 to 35 days before treatment, were slaughtered 7 to 9 days after treatment, and were housed on concrete from the time of treatment until slaughter. In lambs given doses of 7.5 mg or 3.8 mg of albendazole/kg or 7.5 mg of levamisole/kg, reductions in numbers of H contortus were 99%, 85%, and 98%, respectively. Reductions in numbers of T actinioides were 98%, 45%, and 0% respectively, as compared with untreated controls.

Albendazole↗
PubMed1980

Efficacy of oxfendazole against Nematodirus battus and inhibited stages of sheep nematodes.

Oxfendazole administered at a dose rate of 5 mg/kg was 100 per cent effective against artificially acquired seven-day-old and 23-day-old infections of Nematodirus battus in lambs. At the same dose rate it was 100 per cent effective against naturally acquired infections of adult Trichostrongylus spp, adult and arrested early fourth stage larvae of Haemonchus contortus and Nematodirus spp. Efficacy against Ostertagia spp was 99 to 100 per cent against adults and 100 per cent against inhibited larvae, the predominant species of this genus being O circumcincta.

Animals↗
PubMed1980

Observations on epidemiological and clinical aspects of gastrointestinal helminthiasis of sheep in northern Nigeria during the rainy season.

During the rainy season of 1976 severe gastrointestinal helminthiasis was observed in Yankassa sheep grazing unimproved pasture in northern Nigeria. Until mid August high mortality from acute haemonchosis was mainly in lambs. Later, lambs and ewes died from haemonchosis combined with trichostrongylosis but the course of the disease was less rapid. Animals surviving until the end of October showed combined symptoms of chronic haemonchosis and of trichostrongylosis. A rapid turnover rate of adult and developing Haemonchus contortus resulted in a replacement of the blood sucking stages by arrested early fourth stage larvae from mid August onwards. Trichostrongylus spp had a lower turnover rate and only low levels of arrested development occurred, resulting in a gradual build up of Trichostrongylus spp populations during the rainy season. About three or four generations of trichostrongylids developed throughout the rainy season. The first and second generation caused primarily acute haemonchosis, while later generations caused chronic haemonchosis combined with trichostrongylosis.

Animals↗
PubMed1980

Studies on Haemonchus contortus. III. Titration of Trichostrongylus axei and explusion of H. contortus.

Groups of Merino weaners were dosed with infective larvae of Trichostrongylus axei in numbers ranging from 20 000-50 000 and challenged 3 months later with 50 000 infective larvae of Haemonchus contortus. When the dose of infective larvae of T. axei was given on Day 0 and the balance on Day + 14, efficacy against H. contortus was > 60% in > 60% of sheep (P < 0, 1). A single dose of 40 000 or 50 000 infective larvae of T. axei was > 80% effective against H. contortus in > 80% of sheep (P < 0, 01). Two doses of 20 000 infective larvae of T. axei followed by a challenge with H. contortus 31-33 days after the initial dose caused a reduction of > 50% in > 50% of sheep (P < 0, 1). This rose to > 60% in > 60% of sheep if the doses of 25 000 infective larvae of T. axei were followed by a challenge with H. contortus 45 days after the initial dose of T. axei. Most of the challenge doses of infective larvae of H. contortus were rejected within 3 days. Surviving worms were retarded in the 4th stage and only a few developed to the 5th or adult stage.

Animals↗
PubMed1980

Haemonchus contortus: attempts to immunise lambs with irradiated larvae.

Two doses of irradiated Haemonchus contortus larvae stimulated firm resistance to challenge in adult worm-free sheep but not in two-month-old lambs. Parenteral administration of larval antigens in adjuvant together with the two doses of irradiated larvae did not reduce the susceptibility of the lambs. However four doses of the attenuated larvae stimulated three of six lambs to resist the challenge. Similar concentrations of serum IgG and mucosal IgA and IgG antibodies were detected in the sheep which had been vaccinated with irradiated larvae only, regardless of their immune status. The lambs which had been injected with worm antigens had much higher levels of circulating and mucosal IgG antibodies, but mucosal IgA concentrations were similar to those in the other immunised groups. Histological examination of the abomasal mucosa did not reveal any differences between resistant and susceptible vaccinates.

Animals↗
PubMed1995

Persistent anthelmintic activity of ivermectin against gastrointestinal nematodes of cattle.

Two experiments were conducted to determine persistence of ivermectin (IVM) anthelmintic activity. In the first experiment, the injectable (INJ) formulation at a dosage of 200 micrograms/kg of body weight and pour-on (PO) formulation at a dosage of 500 micrograms/kg were compared in 5 groups of calves (n = 6/group). Calves were treated at 14 and 7 days prior to experimentally induced infection. Experimental groups were: 1--untreated, infected controls; 2--IVM PO, day -14; 3--IVM PO, day -7; 4--IVM INJ, day -14; and 5--IVM INJ, day -7. Calves were necropsied on days 28 and 29 after infection. Results of this experiment indicated a high degree of efficacy of IVM PO product (93.8%) for all nematodes up to 14 days, in contrast to poor activity for IVM INJ (26.3%) for all nematodes. Seven-day persistence was excellent for both IVM formulations against Ostertagia ostertagi and Cooperia spp, but a lower degree of efficacy (77.0% for PO and 88.5% for INJ) was observed against Haemonchus placei. In the second experiment, persistent efficacy of IVM PO in preventing establishment of O ostertagi inhibited larvae was observed. In 3 trials, groups of 4 treated and 4 untreated control calves were exposed to natural pasture infection at 0 to 7, 10 to 17, and 20 to 27 days after treatment. Calves were necropsied 15 to 16 days after removal from pasture. After the day 0 to day 7 infection exposure, IVM PO efficacy was 100% for all stages of O ostertagi, 3 adult male Cooperia spp, and Oesophagostomum radiatum; 94.9% for H placei; and 98.2% for Cooperia spp adult females.(ABSTRACT TRUNCATED AT 250 WORDS)

Abomasum↗
PubMed1978

In vitro and in vivo studies on the ovicidal activity of fenbendazole.

The in vitro ovicidal activity of fenbendazole against eggs of Ostertagia ostertagi, Haemonchus contortus and Trichostrongylus colubriformis was observed using different concentrations of active principle. The optimum concentration for ovicidal activity is evidently 0.5 ppm fenbendazole. A further increase in concentration results in a decrease in activity which is probably due to physical causes. Ovicidal activity of the product is assessed by the proportion of non embryonated eggs as well as embryonated eggs which are not capable of hatching. By this method of evaluation a higher ovicidal activity is recorded. Ten h after treating sheep with fenbendazole (dose 5 mg/kg) a large number of eggs whose development was inhibited, as well as atypical eggs were detectable in the faeces. Twelve h after treatment, the capacity for development of the eggs was largely suppressed.

Animals↗
PubMed1978

The efficacy of febantel on gastrointestinal nematodes in sheep.

Febantel (Bay h 5757, Rintal) is a broad-spectrum anthelmintic of a new type. A single oral dose of 5 mg/kg is fully effective against larval and adult stages of Haemonchus contortus, Trichostrongylus colubriformis, Oesophagostomum columbianum, Ostertagia circumcincta and Bunostomum trigonocephalum in sheep.

Acetanilides↗
PubMed1978

Physiological characteristics of free-living and parasitic stages of strains of Haemonchus contortus, susceptible or resistant to benzimidazole anthelmintics.

The effect of changes in genetic constitution (associated with developing benzimidazole resistance) on the physiological characteristics of Haemonchus contortus was investigated. Benzimidazole resistant H contortus were significantly more infective for sheep (20 per cent) than benzimidazole susceptible strains. Pathological changes were more severe in sheep infected with resistant H contortus as measured by packed cell volume, plasma protein concentration and haemoglobin levels. Faecal egg output was significantly higher for resistant strains as was the development and survival of eggs and free-living stages on pasture. Infective third stage larvae of benzimidazole resistant H contortus had a significantly faster exsheathment rate in rumenal fluid than did susceptible strains. These adaptive changes in response to continuing anthelmintic selection of resistant worm populations are discussed and the implications of these findings for worm control programmes indicated.

Animals↗
PubMed1978

Anthelmintic activity of albendazole in white-tailed deer.

Albendazole at dose rates of 11 to 54 mg/kg (mean of 25 +/- 11 SD) of body weight was highly effective (greater than 99%) against Haemonchus contortus, Ostertagia odocoilei, O mossi, Trichostrongylus askivali and Nematodirus odocoilei in 22 white tailed deer (Odocoileus virginianus) in southern Texas. It was 38% effective against mature and immature deer liver flukes (Fascioloides magna). Toxicoses associated with treatment were not observed. Large numbers of abomasal nematodes (mean of 2,949 +/- 3.147 SD) were recovered from 16 untreated control deer, indicating these may have had a potential impact on herd health and indicating the importance of treatment or other management alternatives.

Animals↗
PubMed1993

Protective immunity to Haemonchus contortus induced by immunoaffinity isolated antigens that share a phylogenetically conserved carbohydrate gut surface epitope.

Whole gut homogenates of the blood-sucking nematode Haemonchus contortus induce protective immunity in goats, and some of these gut Ag are conserved among related parasitic nematode species. To identify gut Ag that induce protective immunity and have phylogenetically conserved epitopes, mAb were made to gut-surface Ag of H. contortus. Forty-nine mAb reacted with microvilli of the parasite gut. Two of these mAb (42/10.6.1 and 42/53.3.5) were analyzed here. Both of the mAb bound to the microvillar surface of freshly isolated gut, and each mAb recognized carbohydrate epitopes, based on sensitivity to periodate oxidation. The 42/10.6.1 epitope occurred on at least 18 proteins in Western blots and in several H. contortus tissues. Proteins recognized by this mAb localized to membrane and excretory/secretory fractions of the worm. This epitope was also identified on the gut and other tissues and multiple proteins of related adult and larval nematodes, including larval Ancylostoma caninum and a mixed population of the free-living nematode Caenorhabditis elegans. In contrast, the 42/53.3.5 mAb bound to the gut surface and recognized proteins of 100 and 46 kDa from adult H. contortus gut. Four proteins of 100, 52, 46, and 30 kDa were isolated from the 42/53.3.5 immunoaffinity columns, and except for the 30-kDa protein, each was recognized by both the 42/10.6.1 and 42/53.3.5 mAb. Epitopes recognized by each mAb were distinct from one another and phosphorylcholine. When used to immunize goats, Ag isolated by both mAb induced protection that significantly (p < 0.05) reduced total worm counts after challenge infections compared with the control groups.

Animals↗