Lungworm Larvae Research Articles

Effect of nematode infections and management practices on growth performance of calves on commercial dairy farms

Live weightof calves on 86 dairy farms was measured at the end of the grazing season and related per herd to the level of exposure to nematode infection estimated in October and December. There were significant between-herd variations in all the serological infection parameters measured. On average 20.5 larvae per gram faeces (geometric mean) were found in October. Faecal samples of 20.5% of the herds contained lungworm larvae. Liveweight of calves deviated per herd from −59.8 kg to +52.2 kg from an age-adjusted population mean after their first grazing season. Growth performance was significantly related negatively to several serological and parasitological parameters. Data were fitted by means of both linear and segmented curvilinear regression. By combining infection parameters 19% of the variation in growth performance among herds could be explained. Infection parameters involved were antibody titre against Cooperia spp., egg output and lungworm larval count. It was found that antibody titres were significantly correlated positively to herd age, while pepsinogen values and egg output were negatively correlated to age. Combining supplementary feeding and anthelmintic treatment during the grazing season with the infection parameters into one model explained approximately 30% of the observed variation in growth performance among herds. It was shown that these findings were consistent with those of a similar study conducted on the same farms a year earlier, although there were clear differences between the years. Finally, significant positive relations were found between the levels of exposure to nematode parasites within farms between two consecutive years.

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.

Delay in timing of the oxfendazole pulse release bolus in calves in The Netherlands.

The efficacy of the oxfendazole pulse release bolus (OPRB) was tested in a grazing experiment at the University of Utrecht. Three groups of four OPRB-treated calves and one group of four untreated control calves were grazed on separate pastures between 18 May and 21 October 1987. Based on faecal egg counts for strongyle-type eggs and Nematodirus eggs, embryonation of Nematodirus eggs and faecal larval counts for lungworm, the first pulse of oxfendazole was released after 28 to 63 days, which was later than the period of approximately three weeks indicated by the manufacturer and others. As far as could be detected, the second to fifth pulses were not as delayed, but generally the three-week period was also exceeded. This delayed release of the pulse resulted in a build-up of pasture infectivity for gastrointestinal nematode larvae and lungworm larvae. Nevertheless, this did not result in clinical gastrointestinal helminthiasis and husk in the treated groups of calves, whereas severe husk and mild gastrointestinal helminthiasis were seen in the control group.

Diagnostic Parasitology

Diagnosis of parasitic infections in small animals is challenging, interesting, and fun, and involves the recognition of parasite stages based on size, morphology, color, and movement. Size and morphology are the major diagnostic parameters, and a calibrated microscope is the essential tool in the diagnostic laboratory. The fecal flotation technique is used routinely for the diagnosis of most parasites that reside within the gastrointestinal tract. The specific gravity and type of solution used often will influence the results obtained. A sugar flotation solution with a specific gravity of 1.27 is one that will float a majority of parasite stages with minimal distortion. Other techniques for diagnosis of specific gastrointestinal parasites include the direct smear and the merthiolate-iodine-formalin preservative method for diagnosis of Giardia sp, the Baermann technique for diagnosis of lungworm and other live larvae, the direct sedimentation technique for diagnosis of trematode eggs, the ether-formalin-sedimentation technique for diagnosis of trematode eggs and concentrating protozoan cysts from feces with high fat content, and the McMaster technique, a dilution modification of the fecal flotation technique. Techniques for evaluation of parasites in blood include the Knott's test, hematocrit method, and direct blood smear for diagnosis of microfilariae and thick and thin stained blood smears for diagnosis of Babesia sp, Haemobartonella sp, Cytauxzoon felis, Hepatozoon canis, and Trypanosoma cruzi. Tissue impression smears are used commonly for the diagnosis of Leishmania sp in dogs and biopsy specimens or aspirates are used for the diagnosis of Pneumocystis carinii. Diagnosis of acute toxoplasmosis can be accomplished with peritoneal and thoracic fluids, and organisms occasionally are detected in blood or spinal fluid. Serological tests for many parasitic diseases have been developed and often are used as supportive diagnostic tests.

Increased establishment of lungworms ( Dictyocaulus viviparus) in calves after previous infections with gastrointestinal nematodes ( Ostertagia ostertagi and Cooperia oncophora)

The influence of a priming infection with gastrointestinal nematodes on the subsequent establishment of lungworms was studied. Repeated inoculations of calves with Ostertagia ostertagi and Cooperia oncophora during 3, 5 or 7 weeks resulted in an establishment of lungworms that was 191% of the establishment found in naïve controls. The higher take was associated with a higher faecal output of lungworm larvae and with lower weight gains of calves. The effect was not significantly influenced by the duration of the primary infections or by the actual presence or absence of worms in the gastrointestinal tract.

Cryopreservation of parasites.

In this review, advances in cryopreservation of helminth parasites are reported. Our own studies demonstrate that metacestodes of Echinococcus multilocularis can be maintained in a viable state for at least 1-2 years by appropriate deep-freezing and storage in liquid nitrogen. Infective larvae of the nematode Toxocara canis cryopreserved for 1 week in liquid nitrogen were maintained after thawing in vitro in a chemically defined medium for 35 weeks. Although motility of previously deep-frozen larvae was reduced they produced secretory/excretory antigens of similar immunodiagnostic quality as those from unfrozen larvae. Whereas infective larvae of several species of trichostrongy-lids can be easily cryopreserved, the infective larvae of the cattle lungworm, Dictyocaulus viviparus, and muscle larvae of Trichinella spiralis are more sensitive to damage by subzero temperatures. Therefore, survival rates after cryopreservation are low, but improvement of the cooling schedules appears to be feasible. It is concluded that cryopreservation of certain stages of helminth and protozoan parasites is a useful technique for long-term storage of defined isolates, which can contribute considerably to reducing the number of experimental animals usually required for serial passages.

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.

Nursing behaviour of bighorn sheep: correlates of ewe age, parasitism, lamb age, birthdate and sex

The nursing behaviour of marked bighorn ewes, Ovis canadensis, and their lambs was observed in Alberta, Canada, for 2 years. Suckle duration decreased as lambs grew older. Nursing behaviour in midlactation was correlated with maternal condition; young ewes, ewes with high faecal counts of lungworm ( Protostrongylus spp.) larvae, and ewes whose lambs were born late allowed shorter suckles and were less likely to nuzzle their lamb's rump during a suckle. Sons did not appear to receive more milk than daughters. Suckle duration in mid-lactation was correlated with survival for female lambs but not for males. Lambs born late were disadvantaged, probably because nutritious forage was accessible to their mothers only in early lactation.

Epidemiological patterns of gastrointestinal and lung helminth infections in grazing calves in The Netherlands

The patterns of gastrointestinal and lung helminth infections in grazing calves were studied in two small grazing experiments carried out between May and October in 1985 and 1986, respectively, at Utrecht State University. For lungworm a very rapid translation of infective larvae was seen in both experiments, resulting in a rapid build-up of the worm burdens, and in July the second generation of Dictyocaulus caused husk. After the end of patency for lungworm, in the beginning of August, a rapid decrease in pasture infectivity, measured by pasture larval counts and worm counts of tracer calves, was observed. For the gastrointestinal nematodes the translation of infective larvae was much slower as a distinct ‘midsummer increase’ of pasture infectivity was not seen before the end of July. The worm counts of the tracer calves and the pasture larval counts showed that these larvae remained on pasture much longer than the lungworm larvae. As in Dictyocaulus, patency stopped in August-September 3n Nematodirus but not in Ostertagia and Cooperia, indicating a slower rate of development of immunity in both latter genera. In contrast to lungworm, the results indicate a clear and predictable seasonal pattern for gastrointestinal helminth infections.

Endocrine effects of a trickle infection with Dictyocaulus viviparus in the calf

Fox M.T., Pitt S.R., Gerrelli D., Jacobs D.E. and Simmonds A.D. 1988. Endocrine effects of a trickle infection with Dictyocaulus viviparus in the calf. International Journal for Parasitology 18: 549–551. Endocrine effects of a trickle infection with Dictyocaulus viviparus larvae were investigated in the calf. A small increase in plasma pepsinogen levels was recorded 10–14 days after the beginning of the experiment and related to the site of penetration of invading lungworm larvae. An increase in total thyroxine levels later in the study was due, in part at least, to the presence of autoantibodies interfering with the hormone assay. Free thyroxine levels remained unaltered.

Pilobolus species and rapid translation of Dictyocaulus viviparus from cattle faeces

In a series of five laboratory experiments observations were made on the role of Pilobolus in the translation of infective lungworm larvae from faeces of cattle. The results indicated that a substantial proportion of the lungworm larvae present in the faeces may be translated from the faeces by this fungus within eight days at a temperature of 15 degrees C. No clear relationship was observed between the numbers of Pilobolus and the translation of lungworm larvae. Further a longitudinal study on the occurrence of Pilobolus on faecal pats of grazing calves showed that between the beginning of July and the middle of September peak emergence of sporangia generally occurred within one week and most sporangia emerged within three weeks. From faecal pats which had been deposited at the end of September and the middle of October emergence of sporangia was lower and mainly occurred after two to four weeks.

Interactions between lungworms and gastrointestinal worms in calves

Interactons between gastrointestinal worms ( Ostertagia ostertagi, Cooperia oncophora) and lungworms ( Dictyocaulus viviparus) in calves were studied by assessing the effect of primary infections with either group of worms on the development of homologous or heterologous challenge infections. Primary infections with lungworms resulted in some degree of resistance to challenge with gastrointestinal worms, but this resistance was lower than that found after homologous infection. Primary infections with gastrointestinal worms did not confer any resistance to challenge with lungworms. On the contrary, an indication was found of some enhancing effect of previous gastrointestinal worm infection on the establishment of lungworms. The highest degree of resistance against lungworm challenge was found where calves have been primarily infected with lungworms. Lungworm infections produced some elevation of serum pepsinogen levels. Gastrointestinal worms evoked a rise in circulating eosinophils, although this rise was smaller and occured later than in lungworm-infected calves. Under the conditions of the experiment, the effect of 6000 infective lungworm larvae on weight gain was larger than the effect of 100 000 L3 of Ostertagia ostertagi and 100 000 L3 of Cooperia oncophora.

Spread of lungworm ( Dictyocaulus viviparus) infection by Pilobolus fungi among stabled calves

Pilobolus kleinii spores isolated from cattle faeces were administered daily by the oral route to two donor calves excreting Dictyocaulus viviparus larvae in their faeces. Faeces were collected at daily intervals from the donor calves, and on each day a pooled sample of 500 g was placed outside a pen containing two parasite-free experimental calves. A wire screen prevented the experimental calves from coming into contact with the artificially deposited faecal portions. Pilobolus kleinii fruit bodies were observed on the faecal surface in large numbers 5–10 days after deposition. Sporangial discharge was observed to be directed against a window which served as the only light source. Sporangia were found up to 110 cm away from the faeces, and it was estimated that at least 29% of them had been transmitted to a feeding trough placed close to the wire screen. Infective D. viviparus larvae were observed on some of the discharged sporangia. The experimental calves started excreting low numbers of D. viviparus larvae in their faeces 40–49 days after the first portions were deposited. These results indicate that P. kleinii was reponsible for the infection of the experimental calves with D. viviparus, through the discharge of sporangia carrying infective lungworm larvae.

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.

Anthelmintic activity of albendazole against adult Metastrongylus apri in artificially infected swine.

Three groups of five pigs experimentally infected with lungworm larvae (Metastrongylus apri) were treated with albendazole at 5, 7.5 or 10 mg/kg body weight at 35 days postinfection. The albendazole was administered in the feed. Anthelmintic efficacy, as determined by comparison of postmortem lungworm counts for the treated animals and five infected, untreated controls, was 32.6% at 5 mg/kg, 44.3% at 7.5 mg/kg and 60.7% at 10 mg/kg. The 60.7% reduction in lungworms was statistically different at the 5% level of significance. In a second experiment, three groups of five pigs experimentally infected with lungworm larvae (Metastrongylus apri) were treated continuously for 5 days with albendazole in the feed at 10, 20 or 30 ppm, starting at 35 days postinfection. The anthelmintic efficacy, again determined by comparison of postmortem lungworm counts for the treated pigs and five infected, untreated controls, was 99.2% at 10 ppm, 99.9% at 20 ppm and 100% at 30 ppm. These mean reductions from the control values were significant (P greater than .01).

Anthelmintic control of lungworm in donkeys.

A field study was designed to investigate the re-establishment of patent lungworm infections in donkeys following an anthelmintic treatment regime which was effective against Dictyocaulus arnfieldi. In April 1979 faecal samples from 259 donkeys were examined and each animal classified as a negative, low positive or high positive excretor of lungworm larvae. During the summer the control group of 126 donkeys showed an increase in the number of excretors from 80 per cent in April to 91 per cent in October. At the same time there was a rise in the faecal larval output of individual animals so that by October 59 per cent were classified as high positive compared with only 20 per cent in April. The treated group of 133 donkeys received 3.5 g mebendazole daily for 5 days during April and as a result the number of excretors fell from 66 per cent pretreatment to 23 per cent one month after treatment. Despite exposure to infected pastures throughout the summer this figure was maintained at a comparatively low level and by October patent infections had been re-established in only 15 per cent of the donkeys that were negative after treatment.

Bovine Dictyocaulosis

A combined epidemiology and control investigation was performed with parasite-free calves turned out in May on a permanent pasture naturally contaminated with lungworm larvae the previous year. Before the start the field was divided into two plots. One plot was grazed by 12 calves after the first week of May. The other plot was grazed by 12 calves turned out two weeks later. Both groups as well as the plots grazed by them were subdivided six weeks after turning out. Based on a predicted rise in the pasture larval contamination with infective lungworm larvae, one subgroup of each main group was given a tactical anthelmintic treatment six weeks and again eight weeks after their date of turning out. Patent infections from overwintered larvae were detected in both main groups after four weeks of grazing, but not in all individuals of the late turned-out group. The excreted larvae gave rise to pathogenic pasture larval contaminations on the two initial plots five to six weeks after turning out. In the control groups, early turning-out resulted in approx. 10 times higher larval recoveries in faeces and pasture compared to late turning-out. Seven to eight weeks after turning-out critical, severe parasitic bronchitis had developed in the early turned-out control group. In the late turned-out controls, clinical signs were obvious but not critical. Outbreaks were not observed in any of the experimental subgroups, and no larval excretion was observed among them within four to five weeks following treatments. Similarly, no larvae were recovered from their pastures two weeks after treatment and onwards. A third treatment was given to both experimental groups on the same date (August 21) to suppress gastrointestinal parasitism. However, the level of this infection, appeared moderate, probably due to comparatively low precipitation and extensive supplementary feeding given in late summer to compensate for scarcity of grass.

Epidemiology of bovine dictyocaulosis in Denmark

A field experiment was conducted over two grazing seaons with calves on a permanent pasture in order to follow the pattern of infection with Dictyocaulus viviparus. Infective larvae persisted during the first, but not during the second, winter of observation. By means of the agar-bile herbage technique, a moderate first peak of infection was demonstrated in the pasture 2–3 weeks before the appearance of respiratory signs in the calves. Fluctuations in faecal larval output were reflected in the herbage contamination with infective larvae close to faecal pats. This, as well as the horizontal dispersion of larvae in the pasture, took place in less than a week. The proportion of lungworm larvae recovered away from faeces was low during a period of dry and hot weather while herbage sampling at two-hour intervals during two days showed an increase in herbage contamination with lungworm larvae, but not with trichostrongyle larvae between 10 a.m. and 12 noon. The infectivity of the pasture was monitored by tracer calves and compared with the results of the pasture sampling. The general course of the infection in the calves and in the pasture was the results of interaction between them. In addition, the pasture infection was influenced by climate and the infection in the calves by the development of immunity. The course of infection in individuals appeared to have an influence on the general course of the infection through the contamination of the pasture.

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.

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...