Dictyocaulus species: cross infection between cattle and red deer

Aim: To discover whether cross infection between red deer (Cervus elaphus) and cattle is possible with either a bovine isolate of the cattle lungworm, Dictyocaulus viviparus, or with a cervine isolate of the lungworm, Dictyocaulus eckerti which is thought to be maintained primarily in deer. Method: Twelve cattle and 12 red deer were reared parasite-free from birth. At 3-4 months of age, half of each species (n=6) were experimentally infected with D. viviparus and the other half with D. eckerti. The course of infection was monitored for 34 days, after which the animals were slaughtered and the lungs removed to assess levels of infection. Results: Faecal larval counts demonstrated that patent Dictyocaulus infections occurred in all groups. At necropsy, adult worms were found in the lungs in all groups except the cattle that were infected with D. eckerti. The largest numbers of adult worms were found in the red deer infected with D. eckerti. Conclusion: It was demonstrated that both cattle and red deer could be infected with either D. viviparus or D. eckerti. However, D. eckerti larvae that originated from deer established more successfully in deer and D. viviparus larvae that originated from cattle established more successfully in cattle.     

Dictyocaulus infection in farmed red deer (Cervus elaphus)

Post mortem examination of red deer calves on a deer farm situated on hill ground in north-east Scotland revealed infection by a lungworm morphologically similar to Dictyocaulus viviparus. Trials were conducted to monitor the natural development of D viviparus infection in red deer, to investigate the value of a commercial lungworm vaccine and to evaluate methods of treating clinical cases. The findings indicate that the syndrome may be less apparent in red deer than it is in cattle, protection might be gained by vaccination and that housing and medication provide useful therapy. The extent of clinical disease is likely to depend on the general health, bodily condition and nutritional status of the animals versus the weight of infection acquired from the pasture. However, various factors can affect both sides in this confrontation.     

Efficacy trial of an irradiated cattle lungworm vaccine in red deer (Cervus elaphus)

Lungworm (Dictyocaulus sp.) is the parasite of most concern to the New Zealand deer industry. Although lungworm can be controlled by anthelmintics there is an increasing concern over excessive drenching programmes and reliance on chemicals for parasite control. A live irradiated larval vaccine developed for cattle has been available in Europe for the past 40 years but has never been evaluated in red deer in New Zealand. Four groups of red deer and two of cattle were hand reared from birth in parasite-free conditions. The cattle acted as a control group to ensure that the vaccine was still efficacious on arrival in New Zealand. Two groups of deer were vaccinated, and all four groups were challenged with either D. viviparus or deer origin Dictyocaulus, tentatively identified as D. eckerti. The vaccine provided excellent protection to cattle under New Zealand conditions, there was no larval output in the vaccinated cattle and no adults were found in their lungs at necropsy. In red deer, patency was delayed in the vaccinated groups regardless of challenge species and larval output was lower but was not prevented. Adult lungworms were found in the lungs of all deer at necropsy but fewer were recorded in the vaccinated deer. Although Huskvac provided a degree of protection for red deer it was not effective enough to recommend its use.     

Comparison by experimental infections in cattle of a Dictyocaulus species occurring naturally in red deer and a dictyocaulus of bovine origin

Dictyocaulus species larvae were obtained from young red deer which had become infected on pastures considered to be carrying the Dictyocaulus species indigenous to the red deer of Scotland. These larvae were cultured to third stage and transmitted to five bovine calves. Five other bovine calves were infected with third stage Dictyocaulus viviparus larvae of bovine origin. Microscopic appearances of both groups of larvae were indistinguishable and their lengths were similar. Results indicated that the Dictyocaulus species derived from deer induced milder though similar clinical and pathological responses in cattle than did the D viviparus derived from cattle. It was concluded that there are strains of different pathogenicity within the species D viviparus, that the deer derived Dictyocaulus species was a strain of D viviparus, and that the hazards to animal health associated with infection by D viviparus in farming systems where red deer and cattle may graze alternately are likely to be acceptable.     

A comparison of interactions between vaccination against Dictyocaulus viviparus and anthelmintic suppression in immunised and unimmunised yearling cattle

Twenty parasite-naive calves aged approximately four months were divided randomly into four groups of five. Two groups were treated with oral lungworm vaccine. One immunised group plus another non-immunised group were put out to graze on May 1 on a pasture known to be contaminated with Dictyocaulus viviparus infective larvae during the previous autumn. All the calves both indoor and outdoor were treated with ivermectin at three, eight and 13 weeks after the first groups started to graze and again at housing at the end of September. After the winter housing period on April 27 of the following year all the calves were given an artificial challenge of D viviparus infective larvae at the rate of 15 larvae per kg bodyweight, and the clinical and parasitological reactions monitored. All the calves which had been vaccinated or exposed to field infection during year 1 reacted strongly in ELISAs using antigen prepared from fourth stage D viviparus larvae but much less strongly in similar tests using adult derived antigen. Clinically those calves exposed to previous field infections were less severely affected than the housed calves, although parasitologically all three groups with prior exposure to D viviparus appeared to have a similar functional level of immunity to the challenge infection in comparison to the unexposed calves of the same age.     

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.     

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.     

A pilot study of the efficacy of topical ivermectin against lungworm in young red deer (Cervus elaphus)

Three groups of ten 4-month-old red deer (Cervus elaphus) calves naturally infected with lungworm (Dictyocaulus viviparus) were treated with either oral ivermectin (200 microg/kg), topical (pour-on) ivermectin (500 microg/kg) or oral oxfendazole (5 mg/kg). Faecal larval counts for lungworm were undetectable or very low for 14 days after treatment with oxfendazole, 28 days after treatment with oral ivermectin and for 49 days after treatment with topical ivermectin. This pilot study suggests that the topical formulation of ivermectin was very effective against lungworm and had a more persistent action than the oral ivermectin formulation in young red deer.     

Control of parasitic bronchitis and gastroenteritis in grazing cattle by strategic prophylaxis with ivermectin

In May 1985 four groups of 10 calves, aged between four and five months, were turned out on to separate, permanent pastures of equal area which had been seeded during the previous few days with larvae of Dictyocaulus viviparus. One group acted as a control, the second was vaccinated with lungworm vaccine before turnout and treated with thiabendazole three, eight and 13 weeks after turnout, while the third and fourth groups were given ivermectin three times (three, eight and 13 weeks after turnout) and twice (three and eight weeks after turnout), respectively. A severe outbreak of parasitic bronchitis resulted in the death of three control calves within five weeks of turnout and parasitic bronchitis and gastroenteritis affected the second group of calves after approximately four months at pasture. The calves given ivermectin excreted no lungworm larvae and remained free of clinical parasitism throughout the trial.     

Naturally occurring parasitic bronchitis in red deer: effect of vaccination using live bovine lungworm vaccine

Fifteen red deer calves were put to pasture in two groups, at the same set stocking rates, one group of 10 and one of five, in separate but adjoining enclosures likely to be carrying infective stage larvae of dictyocaulus naturally parasitising the red deer of Scotland. The group of 10 had been vaccinated with a live, bovine lungworm oral vaccine; the group of five had not. Results did not indicate any advantage to the vaccinated deer in weight gain or general health but they excreted fewer dictyocaulus larvae. The findings, although based on only a few animals, support the conclusion that vaccination of red deer would not give them increased protection against the establishment of naturally occurring dictyocaulus infection although it would enhance the suppression of larval production.     

Observations on the epidemiology of Dictyocaulus viviparus in north west England

A five year ley pasture was used as a source of natural infection with Dictyocaulus viviparus for cattle in anthelmintic trials. Pasture larval counts, faecal larval counts of permanently grazing calves and lungworm burdens harboured by tracer calves were monitored in three grazing seasons to assess the pattern of infection. Carrier calves were introduced at the beginning of the grazing season in the first two years of the study but not in the third. In the fourth year the pasture was subdivided into two paddocks where overwintered infection with and without carrier infection were compared. A control paddock exposed to carrier infection but no overwintered infection was also monitored. Pasture larvae survived the winter but carrier infection appeared to make a larger contribution to pasture larval counts and the onset of parasitic bronchitis in susceptible calves. In the absence of grazing cattle at the end of the grazing season the concentration of D viviparus larvae on the herbage fell rapidly to undetectable levels. Discrepancies between contamination of herbage by infective D viviparus larvae and infectivity of pasture for susceptible cattle occurred in all years but were particularly marked on the third year when natural immunity appeared to influence the number of lungworms accumulating in tracer calves. Failure to recover lung worms from tracer calves cannot be regarded as an accurate indication of lungworm free pasture. In the first three years the proportion of the lungworm population which was inhibited in tracer calves was higher early and late in the grazing season and negligible in mid season. This suggests that a predisposition to inhibition in larvae which have overwintered on pasture may influence the time of onset of parasitic bronchitis in the next grazing season, but results from the fourth year did not support this hypothesis.     

The efficacy of a pour-on formulation of moxidectin in young red and wapiti-hybrid deer

AIMS: To measure the efficacy of a pour-on formulation of moxidectin against lungworm and abomasal parasites in weaner wapiti x red deer and to compare this with its efficacy in weaner red deer. METHODS: Six red and six wapiti hybrid deer, naturally infected with lungworm and gastro-intestinal parasites, were treated with pour-on moxidectin at 500 microg/kg body weight and slaughtered 14 or 16 days later, along with six red and six wapiti hybrid untreated control deer. Total worm counts were performed on the lungs, abomasum and abomasal digest of each deer. RESULTS: The efficacy of moxidectin pour-on was 100% against adult and immature lungworms (Dictyocaulus viviparus) in red deer, and 100% and 99.7% effective against adult and immature lungworm in wapiti hybrid deer. The efficacy of moxidectin pour-on was 100, 100, 99.9 and 99.9% respectively against adult, fifth stage, late fourth stage and early fourth stage larvae of Ostertagia-type nematodes (assumed to be Ostertagia, Spiculopteragia, Skrjabinagia and Apteragia spp.) in both red and wapiti hybrid deer. CONCLUSIONS: The pour-on formulation of moxidectin, at 500 microg/kg body weight, is highly effective against mature and immature lungworms and abomasal nematodes in wapiti hybrid deer and equally effective in red deer.     

Comparison of vaccination and ivermectin treatment in the prevention of bovine lungworm

Three groups of calves were put out to graze on separate paddocks within a field known to be infected with Dictyocaulus viviparus and were also given a small initial trickle infection of the parasite. The first group were untreated controls, the second were immunised with live irradiated lungworm vaccine and the third were injected three times with ivermectin; the injections taking place after they had grazed for three, eight and 13 weeks. The subsequent infections of D viviparus were estimated by grazing a series of parasite-free tracer calves in the paddocks used by each group. The first group of such calves grazed from July 17 until August 7, the second from August 22 to September 29. During the first half of the grazing season all the untreated and three of the six immunised calves were observed to excrete D viviparus larvae, in contrast to none of the ivermectin-treated group. As a result all the tracer calves on the areas occupied by the untreated and immunised calves became infected with the parasite whereas only one worm was found in one of the 10 tracer calves grazing the area occupied by the ivermectin-treated calves.     

Identification and isolation of a specific antigen with diagnostic potential from Dictyocaulus viviparus.

The purpose of the investigation was to isolate and identify a specific antigen of Dictyocaulus viviparus that can be used to diagnose lungworm infections in cattle. Somatic, excretion and secretion antigens of adult D. viviparus and somatic antigens of L3 larvae were examined in an indirect enzyme-linked immunosorbent assay (ELISA) to determine whether they cross-reacted with sera collected from calves with mono-infections of Fasciola hepatica. Ostertagia ostertagi, Ascaris suum, or Cooperia oncophora. Serum samples containing antibodies directed against F. hepatica, A. suum, and O. ostertagi cross-reacted with somatic antigens of adult D. viviparus; these sera cross-reacted less with excretion and secretion antigens. When somatic antigens of adult D. viviparus were analysed in a Western blot, a 17-kDa protein that did not react with the heterologous sera was detected. This protein was isolated by ultrafiltration and anion chromatography. Sera collected from calves infected with D. viviparus was tested in indirect ELISAs with either somatic antigens of adult D. viviparus or with a low molecular antigen fraction of this preparation containing the 17-kDa protein. The extinction values that were measured in both assays correlated well. We conclude that the 17-kDa protein isolated from somatic antigens of adult D. viviparus may be useful in developing an improved immunoassay to diagnose lungworm infections in cattle.     

Clinical signs following experimental lungworm infection and natural bovine respiratory syncytial virus infection in calves

Similar clinical signs have been reported in calves infected either by Dictyocaulus viviparus or bovine respiratory syncytial virus. Three experiments were carried out to establish the clinical picture and the course of the disease in animals with these infections. The clinical signs of calves infected with lungworm included coughing, nasal discharge, tachypnoea, abdominal breathing and pyrexia, and auscultation of their lungs revealed increased bronchial sounds. Similar signs were also observed after infection with bovine respiratory syncytial virus, but the signs were more acute and resolved more rapidly than in animals infected with lungworm larvae. Calves infected with lungworm had more serious clinical signs after infection with bovine respiratory syncytial virus than calves, which were not infected with lungworm.     

Immunity of ivermectin treated cattle to challenge from helminth parasites in the following season

Two groups of yearling cattle which had been treated with ivermectin either three and eight, or three, eight and 13 weeks after turn out to trichostrongyle contaminated pasture in their first grazing season were exposed in the following season to natural challenge with helminth parasites. To assess their immunity to this challenge each group shared a pasture with parasite naive first season calves. No anthelmintic treatments were administered at any time during the year. Throughout the grazing period the yearlings showed normal respiratory rates, negative faecal lungworm larval counts, and, relative to the calves, low faecal trichostrongyle egg counts. All the first season calves developed patent lungworm infections and on one occasion the mean respiratory rates of each group of calves were significantly greater than those of the yearling cattle. At the end of the grazing period, from early May until late September or October 1986, the cattle were removed from pasture and together with parasite naive controls challenged with either 10 or 22 third stage larvae of Dictyocaulus viviparus/kg bodyweight and necropsied between 18 and 23 days later. Although the experimental challenge resulted in relatively heavy lungworm infection of the naive controls, none of the yearlings and only three of the 11 calves which had been at pasture were found to be infected. However, large numbers of arrested fourth stage larvae of Ostertagia ostertagi were present in all the naturally infected yearlings and calves.     

Chemoprophylaxis and immunity to parasitic bronchitis in cattle — a field experiment comparing topical ivermectin and an oxfendazole intraruminal device

Seeder calves infected with Dictyocaulus viviparus were used to contaminate a field divided into three similar paddocks. Twenty-four autumn-born calves were allocated to three matched groups; one group was given topical ivermectin treatments (0.5 mg/kg) at 3, 8 and 13 weeks after turnout (Day 0); each member of a second group was given an oxfendazole pulse-release intraruminal device (OPRB) at turnout; while a third group was kept as untreated controls to monitor the natural epidemiological pattern of events. Severe pasteurella pneumonia exacerbated by lungworm infection occurred in the controls after Day 24. Two died and repeated doses of antibiotic and anthelmintic therapy were necessary to save the remainder. Clinical signs were much milder in the ivermectin and OPRB groups and resolved with only a single dose of antibiotic. The OPRB group excreted some lungworm larvae at this time, but none was detected in the faeces of the ivermectin group during the grazing season. At housing, five calves from each group and four lungworm-naive calves were challenged with D. viviparus larvae. The infection became patent in all challenge-control calves, but no larvae were passed by any of the trial animals. Post-mortem worm-counts revealed percentage takes for the challenge controls, trial controls, ivermectin and OPRB groups of 16.7, 0.01, 0.9 and 0.2, respectively. All trial groups had therefore developed a substantial immunity.     

Preliminary investigation into the usefulness of the indirect haemagglutination

Summary

To give an impression of the usefulness of indirect haemagglutination (IHA) in the diagnosis of lungworm infections in cattle under practical conditions, five calves vaccinated against Dictyocaulus viviparus and five unvaccinated calves were periodically subjected to clinical, parasitological, and serological examinations over a period of seven months.

All calves grazed on a lungworm‐infected plot. 82% of the observations in unvaccinated calves, which were positive with respect to one or more of the used parameters, concerned IHA‐positive animals which, however, showed negative results with the parasitic parameters. The titre variation of the serological examination was a further indication of the fact that the IHA detected antibodies against lungworm antigens. No indications of false positive reactions were obtained.

An investigation carried out on 46 farms on the correlation between serological and clinical findings on lungworm infections revealed a positive correlation in 80% of the groups between results obtained with both methods.

The authors consider that IHA offers good prospects for the diagnosis of lung‐worm infections.     

Efficacy and pharmacokinetics of febantel and ivermectin in red deer (Cervus elaphus)

A trial was conducted to determine the efficacy and pharmacokinetics of fehantel and ivermectin in six month-old red deer calves (C. eluphus). Five calves received febantel by mouth at 7.5 mg/kg, five received a subcutaneous injection of ivermectin at 200 microg/kg and five were controls. All calves were killed seven days later and total lung and gastrointestinal worm counts carried out. Febantel was 85 and 99.8% efficient in removing immature and mature Dictyocaulus viviparus, respectively, and ivermectin was 100% efficient in both cases. There was no gastro-intestinal nematodes in any of the treated calves, compared to an average of 619 in the control calves. The metabolism of febantel resulted in plasma levels of fenbendazole, oxfendazole and sulphone for which the common curves fitted by compartmental model peaked at values (standard errors)-of 0.46 (0.03), 0.41 (0.02) and 1.73 (0.07) mg/l after approximately five, nine, and thirteen hours and were undetectable at 30,72 and 120 hours respectively. There was considerable variation among animals in response to ivermectin. The fitted common curve had a peak plasma level of 15.8 (0.08) microg/l at 20 hours after injection, which had dropped to 7.9 (1.1) microg/l seven days after injection. It was estimated that after 15 days plasma levels of ivermectin would not be detectable. It is concluded that the injectable form of ivermectin tested is a highly efficient anthelmintic in deer, and that plasma levels persist for over a week after subcutaneous injection. Fehantel is very efficient against mature D. viviparus in deer, but its reduced efficiency against immature D. viviparus may relate to the deer;s ability to metabolise and excrete benzimidazoles more quickly than sheep and cattle.     

Vaccination of dairy calves with bovine adenovirus type 3

A field study was undertaken to determine the efficacy of vaccinating dairy calves with a killed bovine adenovirus type 3 (BA3) vaccine in a herd where pneumonia associated with BA3 infection had been a severe problem. Calves were first vaccinated when they were less than one week old; a second dose was given 10-14 days later. Efficacy of the vaccine was evaluated following natural exposure to the virus by comparing prevalence of pneumonia in control (n = 21) and vaccinated (n = 21) calves. Seroconversion to BA3 was shown in 9 of 12 control calves that developed pneumonia, 4 of these calves subsequently died as a result of the disease. Four additional control calves had a subclinical infection with the virus. All calves in the vaccinated group developed virus-neutralizing antibodies which averaged 1:20 eight weeks after the second vaccination. The serologic response to vaccination was not inhibited in calves possessing low levels of colostral antibodies. Two vaccinated calves developed pneumonia but they did not succumb to the disease. The prevalence of pneumonia in vaccinated calves was significantly reduced (P less than 0.05) when compared to control calves.