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PubMedDate not supplied

The immunological consequences of nematode infection.

Nematode infections in the gut induce a strong immune response which is rapidly detected parenterally. The response is thymus-dependent and long-lasting and involves both antibodies and cell-mediated reactions. The immunological response to unrelated antigens, tumours and other infectious organisms is altered in animals infected with nematodes. Both antibodies and sensitized lymphocytes participate in the immune response which affects the nematodes themselves, and characteristically the lymphocyte-dependent step cannot act in lactating animals and is neither induced nor able to act in young animals. Present evidence suggests that, despite their well-known association with helminth infections, parasite rejection from the gut does not require the participation of IgE antibodies, mast cells or eosinophils. Homing of lymphoblasts from the mesenteric lymph node or thoracic duct lymph to the small intestine is increased in rats and mice infected with Nippostrongylus brasiliensis or Trichinella spiralis and the increase is antigenically non-specific. In mice infected with T. spiralis this increase is represented mainly by thymus-derived lymphoblasts.

Animals↗

PubMed1978

Anthelminthic effect of oxantel and oxantel-pyrantel in intestinal nematode infections.

704 patients with intestinal nematode infestation were treated with oxantel and oxantel-pyrantel in either liquid or tablet form, at doses from 10 to 25mg/kg. All were given the drug or drugs as a single dose. In 699 patients with trichuriasis cure rates between 64 and 93% were obtained and there were egg reduction rates of between 90 and 100%. The best results were obtained using oxantel, either alone or in combination with pyrantel, at 15 to 20mg/kg. Only 2 of 152 patients with ascariasis were not cured after a single dose of pyrantel (given as oxantel-pyrantel) of 10, 15 or 20mg/kg, and both these patients were from the group given the lowest dose. Only mild side-effects were noted. The combination, oxantel-pyrantel is a safe and effective treatment for multiple intestinal nematode infection.

Adolescent↗

PubMed1978

Forecasting the peak of gastrointestinal nematode infection in lambs.

The pattern of sheep nematode infective larvae on pasture shows a marked midsummer peak arising largely from the ewe peri-parturient egg output. Records of larval pattern over a nine-year period were examined in relation to meteorological data, and a correlation was demonstrated between the time of the summer peak and cumulative rainfall. A "wet score" was allocated to 12-hourly rainfall figures, and a "critical index" of 440 units of wetness was shown to be necessary before the larval peak was reached. A "warning index" of 350 to 380 wetness units is suggested which would allow a prediction to be made of the onset of major infection in lambs.

Animals↗

PubMed1978

Epidemiologic findings on canine and feline intestinal nematode infections from records of the Iowa state University Veterinary Clinic.

A wealth of data was available on intestinal nematode infections of dogs and cats in the Ames, Iowa, practice area served by the Iowa State University Veterinary Clinic. From July 1966 through June 1974, 8.5% of 33,594 dogs and 4.5% of 11,995 cats hospitalized for 1 or more days were recorded as infected with at least 1 type of intestinal nematode. For both dogs and cats, infection rates were generally higher in males than in females and in those that were sexually intact, compared with those that were neutered. The highest prevalence of hookworm infections in both dogs and cats was recorded in June and July, and the highest prevalence of ascarid infections in cats, but not in dogs, was in December. Seasonal patterns were not demonstrated for other nematode infections. Ascarid infections in dogs and cats and hookworms infections in dogs were most prevalent in 2-week-old to 2-month-old animals. Whipworm infections in dogs and hookworm infections in cats generally appeared at greater ages, reaching their highest prevalence in hosts 1 to 2 years old.

Animals↗

PubMed1979

Efficacy of albendazole for treatment of naturally acquired nematode infections in Washington cattle.

Albendazole, methyl 5-propylthio-1H-benzimidazol-2-yl carbamate, was given as a bolus (7.68 to 8.18 mg/kg of body weight) to cattle naturally infected with gastrointestinal nematodes and lungworms in a controlled trial. Over 99% of adult Ostertagia ostertagi, Trichostrongylus longispicularis, Cooperia oncophora, Nematodirus helvetianus, and Dictyocaulus viviparus were removed by the treatment. Efficacy against immature O ostertagi, early fourth-stage O ostertagi, and Oesophagostomum radiatum was 95.2%, 86.6%, and 96.7%, respectively. In a field trial, the same compound administered in a paste formulation (at approximately 7.5 mg/kg) eliminated over 99% of strongylin and Moniezia eggs from feces of treated cattle.

Animals↗

PubMed1992

Epidemiology of nematode infections of Soay sheep (Ovis aries L.) on St Kilda.

The epidemiology of nematode infections of Soay sheep on the island of St Kilda over a period of 2 years (August 1988-August 1990) spanning a host population crash is described. Infective larvae (L3) levels on pasture were high (2422 +/- 365 L3/kg D.M. grass in midsummer 1988) when host population density was high, decreasing after the sheep population declined by 70% in early 1989 (601 +/- 14 L3/kg D.M. in midsummer 1989). The availability of infective larvae to sheep increased during the winter of 1988-1989, probably as a result of concentration of existing larvae on grass as vegetation was destroyed by bad weather and overgrazing. Increased availability of pre-parasitic stages was accompanied by a marked increased in faecal egg counts from sheep of all ages and both sexes. Prevalence and intensity of infection (faecal egg counts) were higher in males than females throughout the 2-year study (chi 2 = 208.3, P < 0.005 and F1, 2000 = 304, P < 0.001 respectively), except during the lambing periods, and decreased with age in both sexes. Changes in prevalence and intensity of strongyle infections were associated with changes in host population density. Prevalence and intensity of Dictyocaulus filaria larvae in faeces increased during the host population crash. Infection intensity decreased with age (F1, 203 = 44.02, P < 0.001) and was higher in males than females (F1, 203 = 13.45, P < 0.001).

Analysis of Variance↗

PubMed1992

Efficacy of moxidectin against naturally acquired nematode infections in cattle.

The efficacy of moxidectin, a new endectocide against natural nematode infections, was evaluated. Twenty-five calves were divided into two groups of eight calves each and a third group of nine calves. Moxidectin was administered s.c. to two groups (I, 0.2 mg kg-1 body weight (BW); II, 0.3 mg kg-1 BW) and the third group (III) received the vehicle (placebo) s.c. Two pre-treatment and one post-treatment faecal nematode egg count determinations were made from all calves, and they were necropsied 2 weeks after treatment for the identification and enumeration of nematode parasites. Group III calves, which received the drug-free vehicle, harboured eight species of nematodes (Ostertagia ostertagi, Trichostrongylus axei, Cooperia oncophora, Cooperia punctata, Nematodirus helvetianus, Trichuris discolor, Oesophagostomum radiatum and Dictyocaulus viviparus). The mean total worm burden for this group was 8935. There was a significant reduction in the numbers of many species of nematodes (Ostertagia, Trichostrongylus, Cooperia and Nematodirus) in both treated groups. Cooperia oncophora was reduced by 94% in Group I and by 96% in Group II, while all other nematode species were reduced by 99%. Immature stages of Ostertagia and Nematodirus were significantly reduced in the two treated groups. Two weeks after treatment, the mean faecal egg counts of both treated groups were reduced by more than 98%. There was no significant difference in mean total worm burdens or egg counts between the two treated groups.

Animals↗

PubMed1992

Epidemiology and effects of nematode infections on beef cow-calf systems of Argentina's western pampas.

The epidemiology and the effects of nematode infections on cow-calf systems were followed from 3 weeks before calving to 7 months afterwards. Two groups, each of 15 cow-calf pairs grazed on separate lucerne pastures. Group I (GI) were treated monthly with oxfendazole (4.5 mg kg-1), cows being dosed from calving and calves starting 45 days later. Animals in Group II (GII) were not treated. The egg output of the cows was very low. An increase was recorded 2 months after parturition, consisting mainly of Ostertagia spp. The egg output and worm burdens of calves remained low until late summer and reached a peak in autumn. Ostertagia, Cooperia and Haemonchus were the main genera recovered from slaughtered calves. The pasture contamination and tracer calf worm counts remained consistently low until autumn when they began to increase. Inhibited early fourth stage larvae of Ostertagia were recovered during spring. After calving, the live-weight gains (LWG) of treated GI cows were significantly higher (P less than 0.004) than those of GII cows, whereas the LWG of GI calves were significantly higher during December (P less than 0.037) and March (P less than 0.029) than those of GII calves. There were significant (P less than 0.04) cumulative LWG responses between GI and GII calves with no differences in cow cumulative LWG at the end of the trial. For spring-born calves, these results suggest that strategic deworming programs in cow-calf systems may produce benefits.

Animals↗

PubMed1992

Prevalence of gastro-intestinal nematode infection in the dromedary camel (Camelus dromedarius) in the Butana plains, Sudan.

The prevalence and intensity of gastro-intestinal nematode infection in their relation to season and rainfall were investigated from 429 female dromedary camels at Tambul market in the Butana plains (Sudan), during 1985-1986. The investigation revealed a similar seasonal pattern in the prevalence as well as the intensity of egg output. The seasonality is mainly brought about by Haemonchus spp. and Impalaia spp. while Trichostrongylus spp. seem to be present as adults throughout the year. There is a good correlation between high egg counts and rainfall ensuring optimal development of preparasitic stages.

Animals↗

PubMed1992

The population dynamics of nematode infections of ruminants: the effect of seasonality in the free-living stages.

A previously published differential equation model for the dynamics of nematode infections of ruminants is modified to allow for time-dependent development and loss rates in the free-living stages. This converts the nonlinear autonomous system to one with periodic coefficients. Fourier transform methods are used to analyse the response of the modified system to these forced oscillations. For biologically reasonable parameter values, the annual pattern of parasitism is determined for the nonautonomous system, and compared with that for the autonomous system with periodic perturbations, and a system incorporating both effects. It is found that, whereas periodic perturbations due to management intervention determine the qualitative annual patterns of larval abundance and host infection, the seasonal dynamics of the larval stages change the magnitude of the adult worm burden.

Animals↗

PubMed1978

Treatment of soil-transmitted nematode infections in children with mebendazole.

Treatment of soil-transmitted nematodes with mebendazole was carried out in 137 children aged 6--15 years in Thailand. There were 100 cases of hookworm infection, 37 of ascariasis, 16 of trichuriasis and 32 of strongyloidiasis. Mebendazole was given at 100 mg twice daily for three consecutive days irrespective of age or weight. The reduction rates as seen by mean egg counts four weeks after treatment were 94.9% for hookworm infection, 100% for ascariasis and 93.9% for trichuriasis; the reduction rates of the mean larval count in 15 cases of strongyloidiasis was 82.1%. No side-effects were observed. Mebendazole was thus confirmed as effective and safe in the treatment of soil-transmitted nematode infections in children in Thailand.

Adolescent↗

PubMed1977

Studies on nematode infections of beef cattle in New South Wales.

The occurrence and seasonal trends of nematode parasite infections in beef cattle on the Tablelands and North Coast regions of New South Wales are described, based on worm counts from 627 spring-born steers slaughtered at 2-monthly intervals from 6 to 24 months of age. The predominant parasites were Ostertagia ostertagi, Trichostrongylus axei and Cooperia spp. Large burdens of adult Ostertagia were seen in 12-month-old animals in late winter and early spring, and later in 18- to 20-month-old cattle in the following late summer and autumn. These infections often resulted in outbreaks of clinical parasitism. Massive numbers of inhibited early fourth stage larvae (EL4) also accumulated in the yearlings during their first spring, reached peaks in mid-summer and then declined. The possibility of their resumption of development to mature worms in the late summer and autumn period is discussed. Adult T. axei showed a similar seasonal trend to Ostertagia and may have increased the severity of outbreaks of clinical disease. Cooperia populations of EL4 and adult worms were highest in weaners during winter, but lower numbers thereafter indicated a strong resistance to re-infection. In addition, Haemonchus placei occurred frequently on the North Coast both as EL4 and adults in cattle of all ages up to 20 months. Of the other cattle nematodes, Oesophagostomum radiatum and Trichuris spp occurred in low numbers, mainly in weaners. Bunstomum phlebotomum and H. contortus occurred sporadically on the North Coast and Tablelands respectively. Intestinal Trichostronglyus spp, Oesophagostomum venulosum and Dictyocaulus viviparus were seen occasionally and Nematodirus spp were not seen. There was a poor relationship between worm counts and faecal egg counts. Cooperia spp dominated the egg counts, while those for other genera were generally low and did not reflect the relative abundance or seasonal changes in worm numbers.

Animals↗

PubMed1976

Basophil leucocytes in cutaneous hypersensitivity reactions in nematode-infected guinea-pigs.

Cutaneous hypersensitivity reactions were elicited in guinea-pigs infected with the parasitic nematode Trichostrongylus colubriformis by injecting them with a crude extract of T. colubriformis fourth-stage larvae. The reaction was characterized by early oedema and pronounced cellular infiltration, initially with neutrophils but later with mononuclear cells, basophils and variable numbers of eosinophils. Because basophils have been implicated as effector cells in the protective immune response of guinea-pigs to this nematode, the capacity to elicit a basophil-rich cellular infiltrate in infected animals might be a useful assay for T. colubriformis protective antigen(s).

Animals↗

PubMed1976

[The effect of dehelminthizations performed during the year on the seasonal dynamics of natural nematode infections in sheep].

In four sheep flocks of two age categories dynamics of natural infections by pulmonary and gastrointestinal nematodes was studied; sheep were kept on a farm in Western Bohemia. Dehelminthizations were performed in different intervals during the grazing period on the basis of the results of quantitative coprologic examinations. Total effectiveness of 80--100% intenseffectiveness (IE) was obtained as a result of single peroral or intraruminal dehelminthization with the following preparations: pyrantel hydrochloricum (Spofa), helmatac (SKF) and nilverm (ICI); the effectiveness concerned gastrointestinal nematodes of the genus Haemonchus, Cooperia, Ostertagia, Trichostrongylus, Bunostomum, Chabertia, Nematodirus, Strongyloides, Oesophagostomum and Trichocephalus. The effectiveness of nilverm on lungworms of D. filaria and P. kochi reached 100%; the preparation was less effective and ineffective on M. capillaris. Dehelminthization practices during three years were more successful as to lowering of incidence of lungworm infections of D. filaria and P. kochi than in gastrointestinal nematodes. If sping dehelminthizations had been postponed till the second half of May or June, the climax of the elimination of ova from summer re-infection was put off till November, with an initial significant increase in September. The third dehelminthization, applied in August, did not result in the increased elimination of ova in autumn, while there was no usual autumnal climax following September dehelminthization. Effective dehelminthization performed at the end of November in all three years maintained low levels of infections during winter housing and significantly influenced the health conditions of ewes before lambing. Dynamics of the elimination of ova after dehelminthization was affected by nematodes with the migration phase in organs and tissues -- S. papillosus, Oesophagostomum sp. and Ostertagia sp.; the same effect was observed, during pasture, in nematodes with relatively short exogenous development of the genus Haemonchus, Ostertagia, Trichostrongylus and Nematodirus. In spite of these dehelminthization practices, the elimination of ova and larvae corresponded to the course of temperatures and rainfall in spring and autumn climaxes every year.

Animals↗

PubMed1976