Dictyocaulus Viviparus Larvae Research Articles

The residual effect of treatment with ivermectin after experimental reinfection with nematodes in calves.

The residual effect of treatment with ivermectin after experimental reinfection in calves was tested. Twenty-four calves were divided into 6 groups of 4 calves each. All calves received a primary infection of 50,000 larvae of both Ostertagia ostertagi and Cooperia oncophora and 1000 Dictyocaulus viviparus larvae. Calves of group 1 remained untreated, and all other calves were treated 21 days after primary infection (0.2 mg/kg injected subcutaneously). Calves of groups 1 and 2 were slaughtered 7 days later. Calves of groups 3-6 were reinfected with the same number of larvae 3 days, 1, 3 and 6 weeks after treatment respectively. Slaughter was 21 days after reinfection. Based on post-mortem worm counts the efficacy of ivermectin after primary infection was 99.7% for O. ostertagi, 95.1% for C. oncophora and 100% for D. viviparus. A residual effect was present for at least one week, but could not be observed 3 weeks after treatment.

Viability and pattern of emergence of Dictyocaulus viviparus larvae in sporangia of the fungus Pilobolus kleinii

Recoveries of third stage Dicytocaulus viviparus larvae (L3) from Pilobolus species sporangia ranged from 23 per cent at 21 days to 3 per cent after 90 days for sporangia attached to polythene discs positioned on pasture. There was a continuous release of L3 for up to 16 days from sporangia which were placed under conditions simulating those occurring on pasture.

Dispersal of Dictyocaulus viviparus larvae from bovine faeces in Ireland.

An involvement of Pilobolus species fungus in the dispersal of Dictyocaulus viviparus third stage larvae from dung to surrounding herbage under Irish conditions was investigated. The presence of Pilobolus kleinii on artificial dung pats containing first stage larvae of D viviparus was associated with a 19-fold increase (P less than 0.05) in numbers of third stage larvae recovered from the surrounding herbage. A subjective examination of natural dung pats showed that the presence of Pilobolus species was significantly correlated with hours of bright sunshine (r = -0.5, P less than 0.01), total rainfall (r = 0.41, P less than 0.05) and the height of herbage surrounding the pats (r = 0.31, P less than 0.001). A multiple regression analysis showed that meteorological parameters and the height of surrounding herbage accounted for 38 per cent of the variation in growth of Pilobolus species on dung pats. The incidence of extensive damage to natural dung pats within five days of deposition, caused by biotic factors, another possible cause of D viviparus third stage larvae dispersal, varied from 0 to 92 per cent of the pats depending on their degree of dryness.

Efficacy of low doses of fenbendazole and its administration via drinking water in the prophylaxis of nematodiasis in grazing calves.

Under experimental conditions, fenbendazole given at doses of 0.4 and 1.0 mg/kg body weight suppressed calves' faecal output of Ostertagia and Cooperia species eggs and Dictyocaulus viviparus larvae. Both dose levels were given in the form of small daily drenches and the higher level showed greater efficacy. In a grazing experiment, medication with fenbendazole at 1.0 mg/kg/day administered intermittently to calves using an automatic dose dispenser almost completely suppressed the output of trichostrongylid eggs. As a result, infection on the pasture and in the calves remained at a low level throughout the grazing season. By contrast, control pasture and control calves showed rather heavy infection from mid-August onwards with significantly lower weight gains and widespread signs of parasitic gastroenteritis. At post mortem examination of representative calves from each group in November, the medicated animals had 99 per cent less Ostertagia species, whether adults or larvae arrested at the early fourth stage, and 95 per cent less Cooperia species compared with controls. Medication in the drinking water suppressed the faecal output of D viviparus larvae for most of the grazing season by comparison with the controls but the medicated calves became infected with this parasite towards the end of the season. Until this problem is overcome, precautions against parasitic bronchitis are advised when this system of medication is adopted.

Survey of internal parasitism and anthelmintic use in farmed deer

Faecal samples and questionnaires from 115 and 130 farms respectively were used to survey the internal parasite status of the national deer herd and examine current drenching practices. The survey included farms with red deer and wapiti-red deer crosses (Cervus elaphus), and fallow deer (Dama dama). Gastrointestinal nematode eggs were recorded from 84% of all farms, Dictyocaulus viviparus larvae from 85% of all farms, and Elaphostrongylus cervi larvae from 35% of the farms with C. elaphus. Faecal egg and larval counts were generally low. There was a significant relationship between the presence of Elaphostrongylus and the introduction of deer from Southland/Fiordland. Fenbendazole, oxfendazole and albendazole were the most frequently used anthelmintics of the 14 reported. Drenching programmes were extremely varied.

Studies on the interaction between an irradiated bovine lungworm vaccine and a morantel sustained release bolus.

The interaction of the morantel sustained release bolus with the development of immunity in calves vaccinated with two doses of gamma irradiated (40 Kr) Dictyocaulus viviparus larvae was investigated under laboratory conditions. A total of 37 helminth-naive calves were used. Eight calves were used in the first part of the study to test the efficacy of a larval vaccine prepared by using gamma rays delivered from a cobalt source. In the second part of the study, four groups of four groups of four calves each were vaccinated and of these, all the animals in two groups each received a bolus. The remaining three groups (two groups of four and one group of five calves each) remained nonvaccinated with each animal in one group receiving a bolus. All the calves were challenged with approximately 2000 lungworm larvae four months postvaccination. In order to simulate possible field conditions, two of the vaccinated groups and two of the nonvaccinated groups were given a trickle infection of 800 lungworm larvae over a four-week period, three months prior to challenge. Based on a comparison of clinical signs, pathology and lungworm burdens at necropsy, the vaccination of the calves conferred a significant degree of protection (P less than 0.001) to a subsequent challenge compared with controls. The introduction of a morantel sustained release bolus and/or a trickle infection had no effect on the high degree of protection engendered by the vaccination. Nonvaccinated calves given a trickle infection, with or without a bolus, were also highly immune to challenge.

Grazing study in Ireland using the morantel sustained release bolus for controlling nematodiasis in calves.

The morantel sustained release bolus was administered at turnout to first-season grazing calves in order to assess its efficacy in the seasonal control of infection by nematode parasites in Ireland. The pastures grazed by control calves showed a marked increase in gastrointestinal trichostrongylid infective larvae by September, while numbers of infective larvae on pasture grazed by bolus-treated calves remained at a low level throughout the grazing season. In consequence, the controls showed significantly higher worm egg counts in late season and significantly higher worm burdens (mainly Ostertagia spp) at necropsy carried out in November on representative number of principal animals selected from each group. These reduced worm burdens were attributed to the suppression of egg output during the early part of the season as a result of treatment with the morantel sustained release bolus at turnout in the spring. Pasture contamination with Dictyocaulus viviparus larvae was present on all treatment pastures. The bolus-treated calves however were subjected to an increase in D. viviparus infection which occurred on their pasture in late season after the active life of the bolus had expired. It was concluded that bolus treatment delayed (rather than prevented) the buildup of D. viviparus infection on the pasture by 60-90 days.

Reactivation and shedding of bovine herpesvirus 1 following Dictyocaulus viviparus infection

Three groups of 4 bullocks which had recovered from infectious bovine rhinotracheitis (IBR) were infected 5 months later with Dictyocaulus viviparus larvae. Bovine herpesvirus 1 was recovered from days 7 to 21 post-infection from the nasal secretions of the group given 50 larvae per kilogram and on one occasion from those given 1000 larvae per animal (<5 L 3 per kg). Virus was not isolated from the animals given 1000 irradiated larvae. Typical clinical signs and lesions of IBR developed in the group from which the virus was isolated regularly.

Effect of repeated doses of levamisole on grazing cattle infected with Dictyocaulus viviparus

Seventy-one worm-free Friesian calves were allocated by weight to three trial groups (1, 3 and 4) of 18 and a control group (2) of 17 animals. Calves in group 1 were vaccinated with a bovine lungworm oral vaccine on days 0 and 28, and on day 42 all groups were turned out to graze together on pasture known to be infected with Dictyocaulus viviparus larvae. Twenty-eight days after first exposure to infection one control calf died of parasitic bronchitis. Anthelmintic medication consisting of two doses of levamisole (7 . 5 mg/kg) at 14 day intervals was promptly administered to group 3 calves and three doses at the same intervals to group 4 calves. All calves were challenged with 20,000 infective D viviparus larvae on day 147. Calves were weighed every 14 days throughout the trial which ended 42 days after challenge. Pasture contamination and infectivity were monitored by pasture larval counts and tracer calves. Statistically there was no significant difference between the performances of treated and vaccinated groups before challenge but all were significantly superior to the control group. After challenge the productivity of all experimental groups was temporarily depressed but the levamisole treated cattle recovered more rapidly becoming significantly heavier than the vaccinates at the end of the trial. The mean group weight gains over the trial period were 89 . 92, 63 . 87, 88 . 67 and 98 . 70 kg in groups 1, 2, 3 and 4 respectively.

Spread of infective Dictyocaulus viviparus larvae in pasture and to grazing cattle: experimental evidence of the role of Pilobolus fungi.

Four calves experimentally infected with Dictyocaulus viviparus were made Pilobolus-free by hygienic measures and by feeding them irradiation sterilized feed. Two of the calves were only administered laboratory cultured Pilobous sporangia daily. As a result, the faeces from one pair contained D. viviparus larvae and Pilobolus sores, and the faeces from the other one pair contained D. viviparus larvae, but no Pilobolus spores. Two identical plots were used for deposition of the two kinds of faeces, and one of them remained free of Pilobolus fructification. Herbage sampling and the use of tracer calves revealed that on this plot the larval contamination and the infectivity of the pasture were greatly reduced. A mean larval count of 1321 near the faecal pats (0-5 cm) in the plot where Pilobolus was observed was reduced to 69 per kg of herbage on the Pilobolus-free plot. At a distance of 100 cm from the pats, a reduction from 99 to 3 larvae per kg herbage was found. Each plot was grazed by four parasite-free tracer calves for 3 days. During the subsequent stabling period of these calves, the lungworm larval excretion of those from the Pilobolus-free plot was reduced by 90% and the clinical symptoms were milder than those which grazed the plot which contained the fungus. The mean post mortem worm counts after 4 weeks of stabling showed a reduction from 167 to 25 worms. A more marked effect of Pilobolus fungi on the transmission of D. viviparus infection is to be expected under field conditions where calves are grazing more selectively than in the present study.

Cell adherence to larvae of Dictyocaulus viviparus in vitro

Bovine eosinophils survived for up to 48 hours in vitro in a medium of undiluted bovine serum and became adherent to the surface of Dictyocaulus viviparus larvae earlier than other cells found in peripheral blood. Cell adherence was associated with a heat labile factor in normal bovine serum and a heat stable factor in hyperimmune serum. A factor associated with leucocytes in vitro appeared to cause larval immobility. Cells from calves treated with levamisole behaved identically to those from other sources. It is suggested that eosinophils are an important element in host defence against D viviparus infection.

Survival of Dictyocaulus viviparus infection in earthworms

Dictyocaulus viviparus larvae were isolated from earthworms and shown to be infective to one oui of two susceptible calves. It is suggested thai Iransmission by earthworms may explain the movement ofD viviparus larvae from the reservoir of larvae in soil back onto herbage.

Identification of Infective Dictyo-Caulus Viviparus Larvae Isolated from Herbage By the Bile-Agar Technique

A morphological description was given of the infective stage of the cattle lungworm Dictyocaulus viviparus. The larvae were stained with iodine and examined under an ordinary microscope after isolation with the bileagar technique used for processing herbage samples. Under these conditions the internal structures appeared of limited value to the identification. The larvae were characterized by their measurements as well as by their shape and profile. A comparison between larvae isolated from the field and larvae harvested from faecal cultures revealed that field larvae were smaller and more uniform in size. Of the reported characteristics the typical profile, the comparatively small size (range 305–400 µm), and the retaining of iodine stain were found most useful in routine recognition of D. viviparus infective larvae in isolates from herbage samples containing free living nematode species as well as infective stages of parasitic species.

Dictyocaulus viviparus: Migration in agar of larvae subjected to a variety of physicochemical exposures

Dictyocaulus viviparus larvae were exposed to ox bile and CO 2 at intervals during their cultivation to the infective stage. Preinfective and young infective larvae were stimulated by CO 2. Bile slightly inhibited preinfective larvae, but stimulated the infective stage. Old coiled, resting infective larvae were stimulated by bile down to a concentration of 10 ppm of bile dry matter, by vertebrate biles of pig, sheep, newborn calf, cow, guinea pig, dog, and chicken, as well as by defatted bile dry matter and by glyco-, tauro-, glycodeoxy-, and taurodeoxycholates. Continuous bile exposure appeared necessary to maintain high larval activity. A high pCO 2 as well as a low redox potential potentiated the effect of bile, but had no effect alone. Exposure to pepsin-HCl and to trypsin had only a minor stimulatory effect.

Studies on the epidemiology of bovine parasitic bronchitis

In the West of Scotland the epidemiology of parasitic bronchitis in grazing calves was studied over a two year period with the aid of tracer calves and herbage examinations for Dictyocaulus viviparus larvae. The observations of both years emphasised the importance of overwintered lungworm larvae as a source of disease. In the first year it was shown that the ingestion and development of these overwintered larvae were, by themselves, directly responsible for severe morbidity, high faecal larval counts and deaths. In the second year it was shown that pasture ungrazed during the winter and spring and from which a hay crop was removed in mid-summer was still capable of producing clinical parasitic bronchitis in susceptible calves within three to four weeks of their introduction in later summer. In both years there was some evidence that the outbreaks appeared to be associated with the sudden availability of infective larvae on the herbage. The possibility that such larvae may have survived for many months in the soil is discussed. Despite the heavy challenge with lungworm larvae experienced by the grazing calves in the first year those vaccinated with lungworm vaccine survived, their clinical signs were mild and of short duration and their faecal larval output was greatly reduced.

Low Level Feed Administration of Morantel Tartrate in the Prophylaxis of Experimental Nematode Infections in Lambs and Calves

SUMMARY In Experiment 1 three groups of worm-free lambs were given 5 000 Trichostrongylus colubriformis larvae daily for 23 days. Two groups were medicated in the food for 28 days with either 1.0 or 1.25 mg/kg/day morantel tartrate. The third group remained unmedicated as control. Post-mortem worm counts showed a reduction of 73% ( P In Experiment 2 three groups of worm-free calves were given 1000 Ostertagia ostertagi and 50 Dictyocaulus viviparus larvae daily for 63 days. Two groups were medicated in the food for the whole period with either 1.0 or 1.5 mg/kg/day morantel tartrate. The third group remained unmedicated as control. Faecal egg counts showed a significant reduction in cumulative Ostertagia egg excretion of 67% ( P P Dictyocaulus larval excretion of 50 and 80% compared with controls for the 1.0 and 1.5 mg/kg/day dose levels respectively.

牛肺虫汚染草地の清浄化試験

牛肺虫汚染草地の清浄化試験

Treatment and control of Dictyocaulus viviparus in captive black-tailed deer.

An outbreak of dictyocauliasis among a captive herd of black-tailed deer fawns (Odocoileus hemionus columbianus) occurred in January, 1971. A transient decrease in output of Dictyocaulus viviparus larvae in feces occurred after treatment with levamisole hydrochloride given as a drench at the rate of 16 mg/kg of body weight. Lungworm larvae were not recovered in feces 6 days after cambendazole, 2-(4-thiazolyl)-5-isopropoxycarbonylaminobenzimidazole, was given as a drench at 40 and 50 mg/kg of body weight. Larvae were again recovered in feces from these fawns between post-treatment days 15 and 23. Output of larvae in feces increased when fawns were confined on a contaminated grass pasture that was intensively grazed. Deteriorating physical condition of the fawns necessitated additional treatment with cambendazole and movement to a woodlot where reinfection by ingestion of larvae was probably minimized. A noninfected deer was placed on the contaminated pasture 75 days after the infected herd was removed. Aft...

Immunity to Dictyocaulus viviparus in Calves: I. Exposure of Larvae to Triethylene Melamine (TEM) and Preliminary Vaccination Experiments

Infective Dictyocaulus viviparus larvae were exposed for 1hr. at 26°C. to concentrations of triethylene melamine (TEM) varying from 0.25 to 0.7%. Reduction in numbers and size of treated larvae after development in calves was related to the TEM concentration. At the optimum concentration of 0.7% TEM the numbers of worms recovered from calves killed at various times up to 28 days of infection were reduced by 87 to 95% compared with normal larvae and the size of worms reduced by 5 to 22%. The infection did not become patent and respiratory rates were only marginally above normal. Lower concentrations of TEM allowed worms to develop fully and larvae appeared in the faeces. Preliminary vaccination experiments in which pairs of calves were given 2 doses of 1,000 normal larvae or larvae attenuated with 0.7, 0.8 or 0.9% TEM showed that a high degree of immunity to experimental challenge was present as measured by faecal larval excretion, respiratory rate and weight gains.

Determination of Viability and Infectivity of Dictyocaulus viviparus Larvae after Storage

Infective third stage Dictyocaulus viviparus larvae were tested for viability by direct microscopic examination, ability to exsheath in pepsin HCl solution and ability to infect guinea-pigs, at intervals during storage for 12 weeks at 4°C. The percentage of larvae judged to be alive by visual examination remained high throughout the experiment. The ability to exsheath fell gradually, but only slightly, during the latter half of the period and was still 75% at 12 weeks. The ability to infect guinea-pigs, however, began to fall between 2 and 4 weeks and fell rapidly after 4 weeks, remaining at about 20% during the third month.