The vicuna (Vicugna vicugna) as a natural host of Dictyocaulus filaria in Peru

Lungworm infection, or verminous pneumonia, is a parasitic disease that causes serious problems in small and large ruminants. Despite the fact that nematodes of the genus Dictyocaulus in cattle and sheep are the main cause of this disease, there are few studies on the natural infections of South American camelids. For this reason, this study aims to report the natural infection by Dictyocaulus filaria in vicunas (Vicugna vicugna) for the first time. During a shearing season (chaku) in Cuzco, Peru, two accidentally killed adult vicunas were submitted to the IVITA-Marangani research center in Cuzco for their respective necropsies. The tracheas of both vicunas had numerous nematodes, as seen during the necropsy. The nematodes were collected in 70% ethanol and were morphologically identified as D. filaria. Likewise, the DNA of six nematodes was extracted, and the ITS2 region and the 28S rRNA gene were amplified and sequenced. The nucleotide sequences of both genetic markers were up to 100% identical with previously reported D. filaria DNA sequences found in the goat yearlings from Turkey, sheep from Iran, Turkey, and India, and the argali from Uzbekistan, which confirmed the morphological diagnosis. This finding represents the first molecular confirmation of a natural D. filaria infection in a South American camelid. It will be necessary to carry out future studies to know the current situation of verminous pneumonia in domestic and wild South American camelids and to know the negative effects of the disease on them.

Morphological and molecular description of Dictyocaulus xanthopygus sp. nov. (Nematoda: Trichostrongyloidea) from the Manchurian wapiti Cervus elaphus xanthopygus

Dictyocaulus xanthopygus sp. nov. (Nematoda: Trichostrongyloidea) was isolated from the lungs of the Manchurian wapiti in Primorsky kray, Russia. The newly described species exhibits morphological characteristics of Dictyocaulus but is distinct from congeneric species based on morphological (lengths of body and esophagus, distances from the anterior end to nerve ring and to excretory pore, the thickness of the buccal capsule, etc.) and molecular features. High levels of genetic divergence as well as Bayesian phylogenetic analyses based on 18S rRNA nuclear and cox1 mitochondrial genes supported the independence of Dictyocaulus xanthopygus sp. nov. Secondary structures of helix 39 of 18S rRNA were identical, while ES9 adjacent to the helix has a unique conformation for newly described worms. Energy-efficient conformational rearrangements of rRNA secondary structures can be applicable in studies on the pathogenesis, epidemiology, taxonomy and evolutionary biology of parasites. Additionally, bracketed dichotomous keys to six valid species of Dictyocaulus were prepared.

Larvoscopic study on Dictyocaulus sp. in the faeces of beef cattle in northeastern Brazil

The lungworm Dictyocaulus viviparus has an important role in cattle health and productivity worldwide, since infections can lead to substantial economic losses. Despite its importance, few studies investigating the epidemiological aspects of infection by this parasite have been conducted. The aim of this study was to report the occurrence of lungworm infection in beef cattle herds reared in an area of livestock production in the northeastern region of Brazil. From September 2020 to August 2021, monthly fecal samples (n = 493) were collected from 46 beef cattle. Among all the animals assessed, lungworm larvae were detected in 8.7% (4/46). None of them presented any clinical sign suggestive of infection by lungworm parasites. Twenty larvae were retrieved, with the minimum number (n = 1) detected in October and December, and the maximum number (n = 13) in November. These presented a mean length of 363 μm (± 28.65 μm) and mean width of 19 μm (± 1.03 μm), and were morphologically similar to Dictyocaulus sp.. This study reports the occurrence of this parasite in this livestock production area. Lastly, local veterinarians need to be aware of inclusion of this parasite in the differential diagnosis of other respiratory infections in beef cattle.

[(IMPACT OF LUNGWORM INFESTATION ON THE BIOCHEMICAL PARAMETERS OF ANIMALS DURING COMBINATION TREATMENT WITH ALBENDAZOLE AND T- AND B-ACTIVIN)]

Lungworm infection is caused by a Dictyocaulus filaria nematode parasitizing the bronchi and bronchioles of sheep and goats. Various anthelmintics, including albendazole, levamisole, fenbendazole, ivermectins, and others, are used to treat the animals. The aim of this investigation was to study the impact of lungworm infestation on the biochemical parameters of animals during combination treatment with albendazole and T- and B-activin. Experiments were carried out in 20 uninfected mongrel lambs aged 4-5 months. Infectious D.filaria larvae were given with water to 15 lambs once orally at a dose of 1000 larvae per head. 5 uninfected lambs served as a control group. The time course of changes in serum bio- chemical parameters was studied in animals. Treatment with Albena in combination with T- and B-activin in lambs ex- perimentally infested with lungworm was found to restore their biochemical reactivity. After sheep treatment with Albena alone, biochemical parameters were noted to tend to normalize, but their normal full recovery did not take place.

Lungworm Infections in German dairy cattle herds--seroprevalence and GIS-supported risk factor analysis

In November 2008, a total of 19,910 bulk tank milk (BTM) samples were obtained from dairy farms from all over Germany, corresponding to about 20% of all German dairy herds, and analysed for antibodies against the bovine lungworm Dictyocaulus viviparus by use of the recombinant MSP-ELISA. A total number of 3,397 (17.1%; n = 19,910) BTM samples tested seropositive. The prevalences in individual German federal states varied between 0.0% and 31.2% positive herds. A geospatial map was drawn to show the distribution of seropositive and seronegative herds per postal code area. ELISA results were further analysed for associations with land-use and climate data. Bivariate statistical analysis was used to identify potential spatial risk factors for dictyocaulosis. Statistically significant positive associations were found between lungworm seropositive herds and the proportion of water bodies and grassed area per postal code area. Variables that showed a statistically significant association with a positive BTM test were included in a logistic regression model, which was further refined by controlled stepwise selection of variables. The low Pseudo R² values (0.08 for the full model and 0.06 for the final model) and further evaluation of the model by ROC analysis indicate that additional, unrecorded factors (e.g. management factors) or random effects may substantially contribute to lungworm infections in dairy cows. Veterinarians should include lungworms in the differential diagnosis of respiratory disease in dairy cattle, particularly those at pasture. Monitoring of herds through BTM screening for antibodies can help farmers and veterinarians plan and implement appropriate control measures.

Study on small ruminant lungworms and associated risk factors in northeastern Iran

OBJECTIVE

To determine the prevalence, identify the species involved and assess possible risk factors of lungworm infection in small ruminant slaughtered in abattoir of Mashhad in the northeast of Iran from October 2010-August 2011.

METHODS

Faecal and post mortem examination were conducted on 350 and 2 500 animals, respectively.

RESULTS

The overall prevalence of lungworm infection was 10.85% and 3.80% in coproscopic and post mortem examination respectively, and this difference was found to be significant. Higher prevalence of lungworm infection was recorded in post mortem examination in sheep (4.1%) than in goats (0.5%) (P< 0.05). The proportion of infection with Dictyocaulus filaria, Protostrongylus rufescens and mixed infection were 3.7%, 0.1% and 0.2% in sheep while in goats, the infection was reported with Dictyocaulus filaria (0.5%) only. The seasonal dynamics of lungworm infection showed that prevalence was highest in winter (7.8%) with a remarkable decline during the dry time (summer) (0.8%) which the difference was significant (P<0.001). The animals of less than one year old showed greater infection in post mortem examination than older animals significantly (P<0.001). Also, the infection rate between male and female animals showed significant difference (P<0.05) with prevalence rate of 4.6% and 2.0%, respectively.

CONCLUSIONS

Due to its impact on production, emphasis should be given for the control and prevention of lungworm infection in this area.

Biological aspects on Dictyocaulus arnfieldi

In the postmortem examination of 54 adult donkeys slaughtered for the carnivore animals in Kafr El-Sheikh Zoological Garden, Dictyocaulus arnfieldi (Cobbold, 1884) Railliet and Henry, 1907 was demonstrated in their lungs. The biological data of the different developmental stages were recorded and discussed, where the period required for maturation, hatching and development of 2nd and 3rd stage larvae was 84 hours, general discussion was given.

The application of mass spectrometry to identify immunogenic components of excretory/secretory products from adult Dictyocaulus viviparus

Proteomics has come to the forefront in the post-genomic era. The ability to compare and identify proteins expressed in a particular cell type under specific physiological or pathological states requires a range of technologies, including separation of complex protein or peptide mixtures, densitometry-based or isotope-coded methods for comparison of multiple proteomes, and mass spectrometric methods for identification of individual low abundance proteins. Although an emergent technology, thus far, proteomics has provided new perspectives on many problems in biomedical science. In parasitology, proteomics has been used to answer specific biological questions relating to survival and development, and also to identify candidates for vaccines. Here, we describe an ongoing research programme in which proteomics is being used to identify potential vaccine candidates for the bovine lungworm, Dictyocaulus viviparus. This work is focusing on antibody responses to the adult parasite excretory/secretory (ES) products, with selection of candidate antigens based on differential screening with serum from immune versus non-immune animals to simplify the proteome and the ensuing analytical challenges. Thus far, we have identified seven candidate proteins using this strategy. Of these, one protein showed significant identity to a previously cloned gene from D. viviparus, whilst the other six proteins have shown no significant identities. Isolation of further peptide sequences is now warranted to facilitate cloning of the genes encoding these antigens.

A transcriptomic analysis of the adult stage of the bovine lungworm, Dictyocaulus viviparus

Background

Lungworms of the genus Dictyocaulus (family Dictyocaulidae) are parasitic nematodes of major economic importance. They cause pathological effects and clinical disease in various ruminant hosts, particularly in young animals. Dictyocaulus viviparus, called the bovine lungworm, is a major pathogen of cattle, with severe infections being fatal. In this study, we provide first insights into the transcriptome of the adult stage of D. viviparus through the analysis of expressed sequence tags (ESTs).

Results

Using our EST analysis pipeline, we estimate that the present dataset of 4436 ESTs is derived from 2258 genes based on cluster and comparative genomic analyses of the ESTs. Of the 2258 representative ESTs, 1159 (51.3%) had homologues in the free-living nematode C. elegans, 1174 (51.9%) in parasitic nematodes, 827 (36.6%) in organisms other than nematodes, and 863 (38%) had no significant match to any sequence in the current databases. Of the C. elegans homologues, 569 had observed 'non-wildtype' RNAi phenotypes, including embryonic lethality, maternal sterility, sterility in progeny, larval arrest and slow growth. We could functionally classify 776 (35%) sequences using the Gene Ontologies (GO) and established pathway associations to 696 (31%) sequences in Kyoto Encyclopedia of Genes and Genomes (KEGG). In addition, we predicted 85 secreted proteins which could represent potential candidates for developing novel anthelmintics or vaccines.

Conclusion

The bioinformatic analyses of ESTs data for D. viviparus has elucidated sets of relatively conserved and potentially novel genes. The genes discovered in this study should assist research toward a better understanding of the basic molecular biology of D. viviparus, which could lead, in the longer term, to novel intervention strategies. The characterization of the D. viviparus transcriptome also provides a foundation for whole genome sequence analysis and future comparative transcriptomic analyses.

First report of bovine lungworm disease in South-East Asia

This paper presents investigation of lungworm disease outbreaks that is based on retrospective examination of cases recorded between 1994 and 2000 on a government beef cattle breeding centre in the state of Pahang, peninsular Malaysia. The breed of cattle on the centre was Nelore and the mean population over a 7-year period (from 1994 to 2000) was 1612. All animals were allowed to graze on pasture and mixed grazing was practiced on the farm. The routine de-worming programme was performed using levamisole and ivermectin from 1994 to 1998 and abamectin in 1999 and 2000 on 1 to 3-month-old calves and an annual dose given to the adult cattle. Nelore was introduced into the farm in 1991, three years before the first outbreak from Brazil where Dictyocaulus viviparus infection had been reported. No lungworm infection had been observed in the farm prior to the animal introduction. Within the 7-year period, 36 fatalities occurred and the annual mortality rate due to lungworm infection was 0.31%. The highest rate was recorded in 1997. Among the total 36 deaths, about 75% of deaths occurred in calves aged between 6 months and 12 months, 67% were males and 33% were female cattle. The highest number of deaths (19%) occurred in the month of November. In conclusion, D. viviparus infection may have been introduced into a tropical climate along with consignments of cattle from lungworm endemic areas resulting in fatal disease outbreaks for a few years following the animal's initial introduction.

Study on small ruminant lungworms in northeastern Ethiopia

A cross-sectional study of lungworm infection was carried out with the aim of determining the prevalence of lungworm infection of small ruminants and identifying the species of the respiratory helminthes circulating in six districts of northeastern Ethiopia: Debresina, Legambo, Habru, Kalu, Chaffa-Dawi and Artumana-Fersejelle. Faecal and postmortem examination were conducted from 1162 and 104 animals, respectively. An overall infection rate of 53.6% and 66.3% was found by faecal and postmortem examinations, respectively. Significant difference (p<0.05) was found between areas of different altitude with an infection rate of 30.4%, 32.5% and 71.3% at low, medium and high altitude areas, respectively. Prevalence on the different months was insignificant (p>0.05). The prevalence of Dictyocaulus filaria and Muellerius capillaris infection showed a significant difference (p<0.05) between young, adult and old age groups. The prevalence of D. filaria decreases and that of M. capillaris increase with increasing age of the animal. Animals under relatively good management system have been found less affected with significant difference (p>0.05) than their counterparts at relatively poor management system. The infection rate between male and female animals showed significant difference (p<0.05) with prevalence rate of 44.4% and 59.3%, respectively. A significant difference between sheep and goats was also noted with infection rate of 24.4% and 50.7%, respectively. Monthly worm burden of D. filaria infection showed significant difference (p>0.05) while it was insignificant in case of M. capillaris. Due to its impact on production, emphasis should be given for the control and prevention of lungworm infection in highland areas.

DifferentialN-glycan- and protein-directed immune responses inDictyocaulus viviparus-infected and vaccinated calves

Calves with naturally acquiredDictyocaulus viviparusinfection mount an effective immune response. In the search for protection-inducing antigens, we found that severalD. viviparusthird-stage larval (L3) and adult ES products carry N-glycans. Deglycosylation of the worm antigens using PNGase F resulted in reduced IgA, IgE, IgG1 and IgG2 (but not IgM) reactivities in sera of primary infected animals, suggesting that the carbohydrate moieties contained immunodominant epitopes. Challenge infection resulted in increased specific serum antibody levels against ES and L3 in the re-infected and challenge control groups. Testing of sera by enzyme-linked immunosorbent assay (ELISA) demonstrated a significant increase in IgG1 and IgE (but not IgA or IgG2) reactivity against the deglycosylated antigens in the re-infected group compared with the challenge control group. Sera from calves vaccinated with irradiated larvae showed a strong anti-N-glycan response, but no booster response against the protein backbone after challenge infection, consistent with the absence of a memory response. Together, our results suggest thatD. viviparusproteins carry immunodominant N-glycan moieties that elicit a strong but short-lived immune response during infection and after vaccination, whereas the protein backbones effectively induce a memory response which results in a long-lasting, potentially protective immune response in re-infected, but not in vaccinated calves.

Targeted selective treatment of lungworm infection in an organic dairy herd in Sweden

The effect of targeted selective anthelmintic treatment on the seroprevalence of the lungworm Dictyocaulus viviparus in cattle was investigated. The study was commenced on an organic dairy enterprise in Sweden in November 1998 after the observation of an outbreak dictyocaulosis in the herd, and then continued for almost 3 years. The first year sampling was conducted on a monthly basis and then biannually with the exception of between August and November 2000 when sampling was performed monthly following a second outbreak of dictyocaulosis. Throughout the study, blood samples were examined for specific IgG(1) levels from all animals in the herd that had been grazing for more than 3 months. At the first sampling occasion, 13% out of the 90 blood samples were seropositive. One month later, after targeted selective treatment with eprinomectin (Eprinex), Merial), the whole herd was seronegative. Seroprevalence then gradually increased and 1 year later it returned to levels similar to those observed at the start of the study. At turnout in April 2000, seroprevalence was 1.3% but it then rapidly increased to 28% and 30% in August and September, respectively. This increase was mainly due to an increase in FSG animals of which many were coughing. Consequently, all seropositive animals were injected with ivermectin (Ivomec), Merial) at 0.05 mg/kg body weight in late August 2000. Although all animals recovered, seroprevalence was only reduced to 12% 1 month later. The differences in seroprevalence after both of these anthelmintic treatments were probably attributed to the timing. The first deworming with eprinomectin was conducted in November when the infection already was transient, whereas ivermectin in connection with the second outbreak was injected in a more acute phase of the infection cycle. Infection levels in 2001 were low with seroprevalences of 2.3% and 5.6% in May and September, respectively. These results show that dictyocaulosis in Sweden can be effectively controlled by the use of macrocyclic lactones. However, the infection was not eradicated from the herd despite close monitoring of the seroprevalence and targeted selective treatment of every seropositive animal on two occasions.

Population genetics of the bovine/cattle lungworm (Dictyocaulus viviparus) based on mtDNA and AFLP marker techniques

Mitochondrial DNA (mtDNA) sequence data and amplified fragment length polymorphism (AFLP) patterns were compared for the lungworm Dictyocaulus viviparus, a nematode parasite of cattle. Eight individual D. viviparus samples from each of 8 herds in Sweden and 1 laboratory isolate were analysed, with the aim of describing the diversity and genetic structure in populations using different genetic markers on exactly the same DNA samples. There was qualitative agreement between the whole-genome AFLP data and the mtDNA sequence data, both indicating relatively strong genetic differentiation among the Swedish farms. However, the AFLP data detected much more genetic variation than did the mtDNA data, even after allowing for the different inheritance patterns of the markers, and indicated that there was much less differentiation among the populations. The mtDNA data therefore seemed to be more informative about the most recent history of the parasite populations, as the general patterns were less obscured by detailed inter-relationships among individual worms. The 4 mtDNA genes sequenced (1542 bp) showed consistent patterns, although there was more genetic variation in the protein-coding genes than in the structural RNA genes. Furthermore, there appeared to be at least 3 distinct genetic groups of D. viviparus infecting Swedish cattle, 1 of which was predominant and showed considerable differentiation between farms, but not necessarily within farms. Second, the 2 smaller genetic groups occurred on farms where the predominant group also occurred, suggesting that these farms have had multiple introductions of D. viviparus.

Mononuclear cell subsets in bronchoalveolar lavage fluid during Dictyocaulus viviparus infection of calves: a potential role for gamma/delta TCR-expressing cells in airway immune responses?

Mononuclear cell populations in the lungs of calves infected with Dictyocaulus viviparus were studied during primary infection and reinfection in order to identify cells involved in development of protective immunity to parasitic bronchitis. Three groups of calves were either inoculated with 500 third-stage larvae at both weeks 0 and 10 (n = 6), inoculated only at week 10 (n = 6), or remained uninfected (n = 3). The animals were monitored weekly by collection of bronchoalveolar lavage fluid (BALF), blood and faeces. Among mononuclear BALF-cell populations, the gamma/delta TCR-expressing cells showed a pronounced transient increase in proportion as well as in relative cell size 2 weeks post primary infection, whereas CD4-, CD8-, Ig- and CD14-expressing cells showed no significant differences related to the infection. The increase in gamma/delta TCR-expressing cells coincided with significantly increased proportions of eosinophils and recovery of adult worms in BALF. After reinfection, gamma/delta TCR-expressing cells increased again, but not until week 3 post inoculation, whereas eosinophils were increased by week 2 and reached higher levels than after primary infection. After reinfection, establishment of D. viviparus was less successful than after primary infection. In conclusion, these results indicate a role for gamma/delta TCR-expressing lymphocytes in the pathogenesis of D. viviparus infection.

Local cytokine responses in Dictyocaulus viviparus infection

The high degree of immunity induced by the bovine lungworm, Dictyocaulus viviparus, makes it an ideal model in which to study nematode-induced protective immune responses. Here, cytokine responses were measured over the course of an experimental infection of D. viviparus. Local cytokine messenger RNA (mRNA) transcripts were measured in lung parenchyma, tracheal rings and draining lymph nodes using semi-quantitative reverse transcriptase-polymerase chain reaction. Responses were measured in animals necropsied at 15, 22 and 43 days post-infection (DPI). The responses elicited at these time points were compared with cytokine levels observed in uninfected animals. Interleukin (IL)-4, IL-5, IL-10, IL-12p35, IL-13 and interferon gamma (IFNgamma) mRNA levels were measured in duplicate at each site. By 42 DPI, very few parasites were recovered, either from faeces or lungs. Transcripts of all cytokines increased in the lung parenchyma, tracheal rings and caudal mesenteric lymph nodes by 15 DPI. The response was rapid and peaked during the time of larval migration through the lungs. By 42 DPI, expression levels of most cytokines were reduced to levels similar to, or below, base line values measured in uninfected animals. Highest levels of IL-10, IL-12p35, IL-13 and IFNgamma transcript were measured in the bronchial lymph nodes of uninfected animals. IgG1 levels were negatively correlated with expression levels of all cytokines. The results demonstrate that a mixed cytokine response occurs over the course of a primary infection during which the parasites were eliminated by day 43 DPI. These results agree with those obtained for other helminths in cattle and challenge the hypothesis that polarised Th2 responses are essential for protection against nematodes in this species. These observations are important in the development of recombinant vaccines, particularly when considering adjuvant choice.

The health of wild red and sika deer in Scotland: an analysis of key endoparasites and recommendations for monitoring disease

Monitoring the health of wildlife populations is important for understanding and controlling the risk of infections to livestock, humans and/or other wildlife. In this paper, we analyse the results of surveys of parasites and non-specific signs of diseases carried out on organs from 638 red and 107 sika deer culled in four regions of Scotland between 1991 and 1997. Infections of the lung by Elaphostrongylus spp. were significantly greater in red than sika deer. Older animals were more heavily infected with Elaphostrongylus spp. and Sarcocystis spp., and infections with Sarcocystis spp. tended to be heavier in more recent years. The results suggest that a combination of key indicator parasite species and non-specific signs of disease may be useful for monitoring the health of wildlife populations at a national scale. However, they also demonstrate that such monitoring needs to be long-term, carried out according to standard protocols and at an appropriate resolution to enable integration with data on other potentially influential environmental factors.

Acute phase proteins in response to Dictyocaulus viviparus infection in calves

Three experiments were carried out to examine the acute phase response, as measured by the acute phase proteins (APP) haptoglobin, serum amyloid A (SAA) and fibrinogen, in calves infected with lungworm, Dictyocaulus vivparus. In addition, eosinophil counts were analysed. Three different dose models were used in 3 separate experiments: I) 250 D. viviparus infective third stage larvae (L3) once daily for 2 consecutive days, II) 100 D. viviparus L3 once daily for 5 consecutive days, and III) 2000 L3 once. All 3 dose regimes induced elevated levels of haptoglobin, SAA and fibrinogen, although there was considerable variation both between and within experiments. A significant increase was observed in all 3 APP at one or several time points in experiment I and III, whereas in experiment II, the only significant elevation was observed for fibrinogen at one occasion. The eosinophil numbers were significantly elevated in all 3 experiments. The results show that lungworm infection can induce an acute phase response, which can be monitored by the selected APP. Elevated APP levels in combination with high numbers of eosinophils in an animal with respiratory disease may be used as an indicator of lung worm infection, and help the clinician to decide on treatment. However, high numbers of eosinophils and low levels of APP do not exclude a diagnosis of lungworm. Thus, lungworm infection may not be detected if measurements of APP are used to assess calf health in herds or individual animals.

Seroprevalence of Dictyocaulus viviparus in first grazing season calves in Sweden

A serological survey was carried out to determine the prevalence and geographical distribution of Dictyocaulus viviparus in calves after their first grazing season in Sweden. A total of 754 animals from 76 randomly selected herds in seven geographical regions were examined between September 24 and December 19, 2001. To get an indication about the geographical distribution of the infection 41 herds with beef-suckler calves were investigated. On each farm, blood was collected from 8 to 10 animals after an average of 26 +/- 24 days post-housing to determine specific IgG1 levels against a possible lungworm sperm antigen that is highly specific against patent infections of D. viviparus. We also investigated the seroprevalence of lungworm infection in relation to cattle management. In one region additional samples were analysed from 35 herds either with: (a) beef-suckling calves that were dewormed at housing, (b) untreated organically raised dairy calves, and finally from conventionally raised dairy calves either, (c) with or, (d) without a prophylactic anthelmintic treatment programme against gastrointestinal parasites on pasture. A questionnaire was used to obtain information about herd size and management, including measures to control nematode parasites on the farm. A total of 86 (11.8%) out of 754 animals had antibodies against D. viviparus, and at least one infected individual was detected in 30 (39.5%) of the 76 herds examined. Lungworm infected animals were found throughout the country and there was no significant differences between regions, although in southern and southwestern Sweden 70.0% of the herds were infected. Furthermore, there were no major differences in the seroprevalence in relation to management. Between 40.0 and 44.4% of the herds were infected irrespective of management, with the exception of calves from organic herds where no seropositive samples were found (0%). This result is in contrast to previous findings of lungworms in Sweden, and indicates that the parasite status on organic farms is diverse.

Genetic diversity assessed by amplified fragment length polymorphism analysis of the parasitic nematode Dictyocaulus viviparus the lungworm of cattle

We have examined the population genetic structure in a collection of nine isolates of the parasitic lungworm Dictyocaulus viviparus. Eight of the isolates were sampled from cattle in geographically separated farms throughout south-central Sweden, and one isolate was a laboratory strain that has been maintained in experimentally infected calves for almost four decades. A total of 72 worms were examined, with eight individual worms from the same individual host representing each isolate. The genetic variation as revealed by amplified fragment length polymorphism analysis using four selective primer combinations was high. Depending on the primer combination a total of 66-79 restriction fragments were amplified, with 26-44 peaks of similar complexity from each of the isolates. The heterozygosity within populations was relatively small, as were the population mutation and immigration rates, which seemed to be in neutral equilibrium. The genetic diversity was therefore reasonably well structured in the field; and the laboratory isolate was quite distinct from the field samples. There was no relationship between the patterns of genetic diversity and the geographical proximity of the farms. The estimates of heterozygosity were much larger and more consistent than those previously estimated for this nematode species using mitochondrial sequencing, and the genetic structuring was thus much less pronounced and the gene flow greater. We attribute these differences in estimation to the broader sampling of loci available using amplified fragment length polymorphism markers, which may therefore constitute a superior technique for the study of patterns of lungworm diversity. Furthermore, the data estimating gene flow for D. viviparus was less than previously reported for closely related species in North America. This might be related to different rates of movements of infected hosts. It seems likely that lungworm infections are rather persistent on different farms, and the sudden outbreaks of disease that can be observed with host movements are most likely to be related to the introduction of susceptible stock.

Effects of condensed tannins and crude sesquiterpene lactones extracted from chicory on the motility of larvae of deer lungworm and gastrointestinal nematodes

The objective of this study was to determine the effects of condensed tannins (CT) and an extract containing crude sesquiterpene lactones (CSL) from chicory (Cichorium intybus) on the motility of the first-(L1) and third-stage (L3) larvae of deer lungworm Dictyocaulus viviparus and the L3 larvae of gastrointestinal nematodes in vitro, using the larval migration inhibition (LMI) assay. The CT and CSL had a profound effect on the motility of the larvae displayed by their ability to inhibit larval passage through nylon mesh sieves. Incubation of lungworm L1 larvae in rumen fluid (collected from deer fed pasture) containing 100, 400 and 1000 microg CT/ml, inhibited 12, 28 and 41% of the larvae from passing through the sieves, respectively, while the incubation of L3 larvae with rumen fluid (pH 6.6) containing the same concentrations inhibited 26, 37 and 67% of L3 larvae from passing through the sieves, respectively. Gastrointestinal larvae seem more susceptible to CT than lungworm larvae especially at higher concentrations. CT inhibited 27, 56 and 73% of gastrointestinal larvae from passing through the sieves when used at a concentration of 100, 400 and 1000 microg/ml, respectively. CT were more effective (P<0.001) at reducing the motility of lungworm L1 and L3 larvae when added to the rumen fluid than when added to the abomasal fluid (pH 3.0). Addition of 2 microg polyethylene glycol/microg CT eliminated the inhibitory effect of CT against L1 and L3 larvae especially during incubation in rumen fluid, confirming the effect as due to CT. The CSL extract also showed similar inhibitory activity against L1 and L3 lungworm and L3 gastrointestinal larvae in both fluids, indicating that this extract was not affected by the pH of the fluid, and was more effective against L3 than L1 lungworm larvae. Condensed tannins appeared to be more effective than CSL at inactivating L1 and L3 lungworm and L3 gastrointestinal larvae in rumen fluid, but CSL were particularly effective against L3 lungworm larvae in abomasal fluid. Activity of these secondary compounds explains the reduced parasite problem of young deer grazing chicory.

Effects of grazing undrenched weaner deer on chicory or perennial ryegrass/white clover pasture on the viability of gastrointestinal nematodes and lungworms

This study determined the in vitro effects on the viability of internal parasites of grazing undrenched weaner deer on either chicory (Cichorium intybus) or perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pasture. One experiment investigated the hatching and development of gastrointestinal nematode eggs and larvae, and the development and motility of L1 lungworm (Dictyocaulus eckerti) larvae, and a second experiment used larval migration inhibition assays to test the viability of L1 lungworm larvae extracted from the faeces of weaner deer grazed on either chicory or pasture when they were incubated with rumen and abomasal fluids from fistulated deer also grazing on chicory or pasture. The incubations were undertaken with and without added condensed tannins purified from chicory and with or without polyethylene glycol (PEG) to bind the tannins. Chicory had no effect on the hatching and development of gastrointestinal nematode eggs and larvae. Grazing chicory reduced the number of lungworm larvae developing to the L3 stage, and L1 lungworm larvae from the faeces of chicory-grazed deer were less viable in rumen and abomasal fluid than larvae from pasture-grazed animals. Abomasal fluid was significantly (P < 0.001) less inhibitory to the migration of L1 lungworms than rumen fluid. When the larvae were incubated in rumen and abomasal fluids from chicory-grazed deer, their passage through sieves was significantly (P < 0.001) reduced in comparison with when they were incubated in the fluids from pasture-grazed deer Adding condensed tannins to rumen fluid increased the inhibition of the migration of L1 lungworm larvae but PEG removed this inhibition; this effect was not observed with abomasal fluid.

Dictyocaulus viviparus: re-emerging or never been away?

For over 40 years a highly effective vaccine against the bovine lungworm has been commercially available. The use of it successfully reduced the number of outbreaks in calves. However, the past decade has seen a dramatic increase in lungworm outbreaks in adult cows in the UK. This might indicate that Dictyocaulus viviparus is re-emerging as a significant parasite in the dairy cattle industry. Much is still unknown, and here the most important aspects requiring urgent attention are put into perspective.

Protection against and establishment of Dictyocaulus viviparus following primary infection at different dose levels

In two experiments, calves were primary infected with 1 of 12 (Experiment 1) or 6 (Experiment 2) different dose levels of Dictyocaulus viviparus infective larvae (L3), ranging from 5 to 2000 L3. To study the level of protection induced by the primary infection a challenge infection with 2000 L3 was given on day 10 (Experiment 1) or day 35 (Experiment 2). In both experiments, challenge control calves were included. Eleven days later, the challenge calves were necropsied for worm counts. Results were compared with predictions from a simulation model. Establishment of the primary infection was dose independent, lying on average in the range of 20-30%. The ratio female:male worms in the counts from the primary or from the challenge infection was consistently close to 1:1 irrespective of primary infection dose level or protection having developed in some of the calves. Level of early protection (10 days after a primary infection-Experiment 1) against establishment of the challenge infection depended significantly on primary infection dose level (P<0.01). At 10 days, after a primary infection, low dose levels did not result in protection against a challenge infection. In contrast, similarly low dose levels did result in partial protection, 35 days after the primary infection. Results confirmed that our provisional simulation model satisfactorily predicts primary infection outcomes, but that it does not accurately predict levels of protection and immunity against re-infections.

Dictyocaulus capreolus n. sp. (Nematoda: Trichostrongyloidea) from roe deer, Capreolus capreolus and moose, Alces alces in Sweden

Dictyocaulus capreolus n. sp. recovered from roe deer, Capreolus capreolus and moose, Alces alces in Sweden is described and figured. Morphological studies revealed the new species to be closest to D. eckerti and D. africanus on the basis of mouth shape, all three species having an elongate mouth opening. The other species of the genus, including D. viviparus, all have a circular to oval mouth opening. Dictyocaulus capreolus n. sp. can be distinguished from D. eckerti and D. africanus on the basis of the morphology of the buccal capsule and the bursa. These morphological studies support earlier evidence of the presence of a new species of Dictyocaulus in roe deer and moose that could be distinguished from D. eckerti and D. viviparus using either a PCR-linked hybridization assay or image analysis software to study the dimensions of the buccal capsule.

Heterologous transmission with Dictyocaulus capreolus from roe deer (Capreolus capreolus) to cattle (Bos taurus)

Eight Swedish Red Breed cattle, about 2 months old, were experimentally infected with a Swedish isolate of Dictyocaulus viviparus (Dviv-Se) from cattle and D. capreolus from roe deer. The aims were to determine whether the roe deer lungworm is infective to cattle or if it can induce seroconversion in cattle against D. viviparus as measured with an ELISA. Four calves which were given 500 Dviv-Se infective larvae (L3) each by larval dosing for two successive days developed patent infection between days 23 and 25 post-inoculation (PI). Larval output varied among the calves and during the patent period. However, maximum recovery occurred between 28 and 56 days PI with peak shedding on day 37 PI. Shedding ceased at day 58 PI and adult worms were recovered from one calf at necropsy (day 67 PI). No immature worms were recovered from the lungs at necropsy. Seroconversion was detected on days 35-42 PI. One Dviv-Se infected calf became seronegative on day 67 PI whereas the other calves still remained seropositive during this period. Prepatency and patency periods of D. viviparus and serological findings in this study basically conform to previous studies. Each calf that was infected with 400 L3 of D. capreolus for two successive days, and about 800 L3 of the same species about 8 weeks later, did not develop to patency based on faecal and post-mortem examinations. Consequently, under the conditions of this study, D. capreolus was not infective to cattle. Two of the four calves that were infected with L3 from roe deer were challenged with L3 cultured from faeces of the Dviv-Se-infected calves. This infection did not develop to patency. Whether this was due to cross-protection as a result of the prior priming with L3 from roe deer is not clear. However, if it is so, it opens up the possibility of using D. capreolus L3 for preventing bovine dictyocauliasis.

Serum immunoglobulin E response in calves infected with the lungworm Dictyocaulus viviparus and its correlation with protection

Protection of a primary Dictyocaulus viviparus infection was measured against a homologueous challenge infection in two independent experiments and this was correlated with serum immunoglobulin IgE responses. A primary infection of 30 third stage larvae (L3) of D. viviparus on day 0 protects calves for 70% against a challenge infection of 2000 L3 on day 35 compared to calves with no primary infection. The variation in post mortem worm counts within this group (n = 6) was very large with mean worm counts of 145 (range 3-446) lungworms. Parasite specific IgA, IgE, IgG1 and IgG2 and total IgE levels in serum were measured by ELISA. Parasite specific IgA, IgG1 and IgG2 were elevated after infection, but correlation with protection was only found with IgG1 levels on day 42 and with IgG2 levels on day 70. IgE was measured in a sandwich ELISA using antisheep IgE that cross-reacts with cattle IgE. No parasite specific IgE could be detected. However, total serum IgE was elevated after infection and total serum IgE levels before and on the day of challenge correlated with protection (P < 0.05). Total serum IgE also correlates with peripheral eosinophil counts between days 14 and 28 after primary infection. Western blots with three different parasite antigen preparations, L1, excretory/secretory products and crude worm adult antigens, were used to detect parasite specific IgE in sera depleted of IgG and IgM. These depleted sera from protected calves contained parasite specific IgE, while sera from nonprotected calves were negative. A band of approximately 100 kDa was recognized in all three antigens. In a second experiment, primary doses of 30, 60, 120, 240, 480 and 960 L3 of D. viviparus were used and necropsy was 11 days after challenge. This experiment confirmed the correlation between protection and total IgE levels before and on the day of challenge. The rapid and strong IgE responses in protected animals after such a low infection might be caused by the specific characteristics of the lungworm antigens or by the somatic migration of the worm and might be involved in the rapid development of protection against lungworm reinfections in cattle.

Immunity in calves against Dictyocaulus viviparus following a low primary infection

Thirty Holstein Friesian heifer calves, 3 months of age, were used to evaluate whether a low primary infection with Dictyocaulus viviparus would result in immunity against challenge infection 5 or 12 weeks later. Fifteen calves were experimentally infected with 30 larvae at day 0, while the other calves remained as uninfected controls. On day thirty-five 6 primary infected (G1) and 6 non-infected calves (G2) were challenged with 2000 larvae. These groups were necropsied on day 70. On day 84 the remaining 9 primary infected (G3) and 9 non-infected (G4) calves were similarly challenged and necropsied on day 119. Respiratory signs developed in most calves from approximately 2 weeks after challenge, but signs were more severe in G2 and G4 than in G1 and G3. The low primary infection resulted in significantly reduced faecal larval excretion (> 80%) and worm burdens (> 70%). In the primary infected groups the proportion of female worms in the worm burden was increased, suggesting that part of the developed immunity affected survival of the worms after their establishment in the host. Worm lengths and worm fecundity were also significantly reduced. All observed effects were stronger following challenge on day 84 than on day 35, but the effect of the duration of a primary infection (contrast between G1 and G3) was only statistically significant in the case of mean faecal larval excretion on the day of necropsy (P < 0.05) and fecundity (P < 0.05).

[Phospholipid and fatty acid content of the blood of sheep infected with the nematode Dictyocaulus filaria]

The results of analysis of phospholipids (PL) and fatty acid content in the blood of sheep infected with the nematodes Dictyocaulus filaria are displayed. A significant increase of lysophosphatidylcholine and arachidonic acid as well as a decrease of docozagexaenic acid in PL of infected sheep have been recorded. That points out to structural and functional disorders of cellular membranes during the infection. These disorder could be used as a metabolic criterion to estimate the relationships within the host-parasite system examined.

Immunisation of cattle with recombinant acetylcholinesterase from Dictyocaulus viviparus and with adult worm ES products

Dictyocaulus viviparus causes a serious lung disease of cattle. For over 30 years, a radiation-attenuated larval vaccine has been used with success; however, this vaccine has several disadvantages. A more stable vaccine against D. viviparus, capable of stimulating prolonged protective immunity, would be beneficial. Recent research has been directed at adult worm ES components that may be involved in parasite survival in the host. One component is the secreted enzyme, acetylcholinesterase (AChE), a target for circulating antibody in infected calves. Here, we describe a study where protection was investigated in calves immunised with either native adult ES products or a recombinant parasite AChE. These antigens were administered twice with Freund's incomplete adjuvant. Subsequently, all calves were challenged with 700 L3 and their worm burdens and immune responses compared with those in calves that received an anthelmintic-abbreviated infection and challenge control calves. Significant levels of protection were not obtained in the immunised groups but significant immunity was achieved in the calves that received the anthelmintic abbreviated infection. Antibody responses amongst the groups were different, with significantly higher IgG1 responses in the immune, infected group and in adult ES recipients. Significantly higher IgG2 responses were found in the latter group. Following challenge, the groups that received the abbreviated infection and the fusion protein produced specific antibody that bound the native enzyme. No differences were observed between groups in peripheral blood mononuclear cell responsiveness to either antigen. However, adult ES products appeared to have a mitogenic effect on these cells, whilst the fusion protein exhibited an inhibitory effect. These results suggest that in this form, AChE is not a potential vaccine candidate and that adult ES products, in contrast to previous experiments in guinea pigs, do not contain protective components.

[Infection of red deer with lung nematodes in Polish and Belorussian parts of Białowieza Forest]

Fecal samples from red deer from polish and belorussian parts of Białowieza Forest were examined by Baermann method. First stage larvae of three species of lung nematodes were found. In polish part in 100% of samples were larvae of E. cervi, in 50% V. sagittatus and in 21% D. noerneri, and in belorussian the level of infection was lower and larvae were in 92%, 36% and 12% of samples respectively. In significant part of samples were met mixtured invasion of two or three species. Finding of larvae of E. cervi is the first registration of this species in belorussian part of Białowieza Forest, and V. sagittatus is a new species for the fauna of Byelorussia. Nematodes E. cervi are dangerous for domestic ruminants.

Potential for cross-transmission of Dictyocaulus viviparus between cattle and white-tailed deer

Development of an in vitro culture system for infectious Dictyocaulus viviparus larvae made it possible to study the potential cross-transmission of D. viviparus between white-tailed deer (Odocoileus virginianus) and cattle (Bos taurus). Between 26 September 1995-29 February 1996, six parasite-free bull calves were individually inoculated with 15 to 50 infective third stage larvae (L3)/kg of body weight cultured from adult D. viviparus collected from white-tailed deer. Three bull calves were simultaneously inoculated with 45 L3/kg of body weight recovered from cattle either by the Baermann technique or by in vitro culture as above. All three calves inoculated with the homologous cattle strain became patently infected while all six calves inoculated with the heterologous deer strain remained negative for the presence of D. viviparus in the feces and in the lungs upon necropsy.

Simulating Dictyocaulus viviparus infection in calves: the parasitic phase

A model simulating Dictyocaulus viviparus infection in calves is described. The present paper only deals with the parasitic phase of the life-cycle. Descriptions are given for establishment, development rate of juvenile stages, mortality rates of both juvenile and adult stages, and fecundity. Literature data were used to to develop parameter functions and to estimate initial values for constants. Development of acquired immunity, defined as the proportional ability of the host to reduce the number of parasite individuals in some stage or about to move into a next stage, against establishment (protection) or affecting mortality rates of juvenile or adult parasite stages has been included. The effect of immunity on one parameter or process is viewed as distinctly separate from the effect on another. Preliminary comparisons between model prediction and observations gives encouraging results, indicating that the model simulates experimental D. viviparus infection in calves reasonably well. Some quantitative discrepancies between prediction and observation make clear however, that not all parts of the model are accurate. Further experimentation is needed to re-evaluate current model description and to improve model simulation.

Effect of forage legumes containing condensed tannins on lungworm (Dictyocaulus sp.) and gastrointestinal parasitism in young red deer (Cervus elaphus)

To investigate the effect of feeding forage legumes containing condensed tannins (CT) on internal parasitism, red deer calves were fed either lucerne (Medicago sativa; 0.1 per cent CT), birdsfoot trefoil (Lotus corniculatus; 1.9 per cent CT) or sulla (Hedysarum coronarium; 3.5 per cent CT) and trickle-infected with deer-origin gastrointestinal nematode and lungworm (Dictyocaulus sp.) larvae for 5 weeks, then slaughtered at 7 weeks. There was a significant negative linear relationship between dietary CT concentration and abomasal nematode burdens. No significant differences in faecal egg counts, lungworm burdens or voluntary feed intake were found. Deer fed sulla had higher liveweight gain, carcass weight and carcass dressing-out percentage, higher serum total protein and albumin concentration and lower serum gastrin concentration and faecal lungworm larval count, compared with lucerne-fed deer. Inclusion of sulla in diets for young red deer may reduce the impact of internal parasites and/or reduce the dependence on anthelmintic treatment.

A model for study of lungworm (Dictyocaulus sp.) and gastrointestinal nematode infection in young red deer (Cervus elaphus)

A model of sub-clinical parasitism in young red deer, using concurrent trickle infections of lungworm (Dictyocaulus sp.) and mixed gastro-intestinal (GI) nematodes of deer-origin was evaluated. 20 parasite-free deer calves were artificially reared indoors from 4 days of age. A further five calves were naturally reared on pasture with their dams, treated with anthelmintic and brought indoors at 3-4 months. At 4-4.5 months of age they were individually housed and allocated to five groups (n=5). Groups were dosed 3 x per week, for 9 weeks with 0, 100 and 500, 200 and 1000 (2 groups), 400 and 2000 infective larvae of lungworm and mixed GI nematodes, respectively, cultured from deer faeces. Liveweight and voluntary feed intake measurements and faecal and blood samples were taken weekly. In the fourth week following cessation of trickle infection, deer were euthanased and lung and GI nematodes recovered. Both lungworm and GI nematode infections became patent at Week 4 of infection. Maximum group arithmetic mean faecal egg counts were 100-190 epg. Maximum group arithmetic mean faecal lungworm larval counts were 58-123 lpg. Group arithmetic mean nematode counts at slaughter ranged from 439-806 for GI nematodes and 31-73 for lungworm, respectively. Despite low nematode counts, reduced liveweight gain, voluntary feed intake and serum albumin concentration, elevated serum pepsinogen, gastrin and globulin concentrations and elevated peripheral eosinophil counts and slight haemoconcentration, but no clinical signs, were observed. The reduction in liveweight gain was related to the reduction in voluntary feed intake (r2=0.83; p<0.088). Naturally-reared deer had similar liveweight gains, voluntary feed intake and nematode counts to artificially-reared deer. Thus, methods of infection to produce concurrent sub-clinical lungworm and GI nematode burdens for study of sub-clinical parasitism in young deer have been defined.

Morphology of inhibited larvae of the bovine lungworm Dictyocaulus viviparus

Some morphological features of inhibited fourth stage (L4) and fourth moult larvae (4M) of the bovine lungworm Dictyocaulus viviparus are described. Inhibition was induced by maintaining the third stage larvae (L3) for 6 weeks at 4 degrees C. Inhibited fourth stage (L4) and fourth moult larvae (4M) were collected by perfusion of the lungs of experimentally infected calves after necropsy at 15 and 68 days post infection (d.p.i.), respectively. Inhibited 4M, isolated at 68 d.p.i., were about ten times larger than inhibited L4 isolated at 15 d.p.i.

Comparative evaluation of two emigration/sedimentation techniques for the recovery of dictyocaulid and protostrongylid larvae from faeces

A comparison between the performance of a flask and a funnel method in recovering dictyocaulid and protostrongylid larvae from faeces revealed the clear superiority of the former. On an average, 137% (p<0.01) more Dictyocaulus viviparus, 175% (p<0.05) more Muellerius capillaris and 1709% (p < 0.01) more Elaphostrongylus cervi larvae were recovered from samples processed by flask rather than funnel. Attempts to further improve the flask method by substituting cloth stockinette for paper tissue, tended to result in the recovery of more faecal debris but no more larvae. In addition to its greater sensitivity, it is suggested that the flask method offers advantages over the funnel system both in terms of time-saving and in lessening the likelihood of cross-contamination.

Interpreting comparative experiments on parasite burdens in animals using randomization and canonical variates

Comparative experiments on parasite burdens present difficulties for modelling and interpretation: data tend to have highly skewed distributions, some standard methods of testing for effects have low power, and there is a need to make allowance for dependencies among the various measurements. Randomization testing and canonical variates analysis are advocated as a means of minimising these problems.

Differences in a ribosomal DNA sequence of lungworm species (Nematoda:Dictyocaulidae) from fallow deer, cattle, sheep and donkeys

The second internal transcribed spacer (ITS2)* of the ribosomal DNA of Dictyocaulus viviparus from cattle, D eckerti from fallow deer. D filaria from sheep and D arnfieldi from donkeys has been sequenced to investigate the genetic relationships among lungworm species, especially between D viviparus and D eckerti, because the latter is not generally accepted as a separate species. The length of the ITS2 varied between 403 and 481 bases, and its GC content ranged from 25 to 33 per cent. Intraspecific variations in D viviparus (0 to 1.5 per cent) and D eckerti (0.6 to 3.3 per cent) were slight; sequence homology between the species ranged from 50.3 to 76.7 per cent. Some sequence differences occurred at restriction sites of endonucleases leading to characteristic restriction fragment length patterns. The interspecific differences between D viviparus and D eckerti far exceeded the intraspecific variation, thus providing additional evidence that the two species are genetically distinct.

Cross-infections between fallow deer and domestic ruminants with large lungworms (Dictyocaulus spp.)

Groups of four deer each were experimentally infected with larvae of Dictyocaulus (D.) eckerti (from fallow deer) or D. viviparus (from cattle) or D. filaria (from sheep), groups of four cattle each with D. viviparus or D. eckerti and groups of 4 lambs each with D. filaria or D. eckerti. The animals were daily examined coprologically following the 16th day post infectionem. The animals were slaughtered at different times and the lungs were dissected. With the exception of the infection of the sheep with D. eckerti from fallow deer, the mutual infections of the different hosts with the lungworm species became patent. Lungworms could be isolated. Fallow deer proved to be more susceptible to an infection with D. viviparus than cattle to an infection with D. eckerti. The large lungworms which naturally infest fallow deer and cattle, D. eckerti and D. viviparus respectively, can be distinguished according to the morphology of their mouth capsules, especially in the structure of the buccal ring. These features were also present after infection of the heterologous hosts.

[Comparative molecular biologic characterization of Dictyocaulus viviparus and Dictyocaulus eckerti]

For a comparative characterization of the lungworm species D. viviparus and D. eckerti which is not generally accepted as a separate species, the restriction fragment length polymorphism (RFLP) of the PCR amplified ribosomal second internal transcribed spacer (ITS2) and their sequences of both species have been examined. Ribosomal ITS2 DNA was amplified from genomic DNA of individual worms using primer that correspond to the conserved 3' and 5' ends of the ITS2 flanking 5.8S and 28S regions of Caenorhabditis elegans. PCR products were digested with restriction endonucleases AluI, NspI, SspI, BclI and MseI and separated electrophoretically on a 1% agarose gel. Each restriction enzyme produced a species specific fragment length pattern. PCR products were cloned into pCRII and sequenced. The length of the ITS2 varied between 403 (D. viviparus) and 481 bases (D. eckerti) with a GC content ranged from 25 to 33%. Intraspecific variations were low (0-1.5%). Interspecific differences occur at 112 bases. The sequence homology between D. viviparus and D. eckerti was found with 76.7%. ITS2 sequence differences between D. viviparus and D. eckerti by far exceeded intraspecific variations. Therefore both methods showed distinct differences between the lungworm species examined, thus proving that D. eckerti is correctly described as a separate species. Both species occur in deer and specific primers have been designed for both species that will be used in prevalence studies to investigate the actual role of deer in the transmission of D. viviparus to cattle.

[The interrelation of the phospholipid composition of the lungs in sheep and of the nematode Dictyocaulus filaria]

The effect of nematodes Dictyocaulus (D) filaria on phospholipid (PL) composition in the homogenate of sheep lungs has been demonstrated. The comparative analysis has shown no differences in the content and composition of PL in the lungs of healthy sheep and in nematodes. Infection of sheep by helminths was found to result in changes in the PL composition of sheep lungs. Thus, it is possible to conclude that D. filaria affecting structural and functional systems of the host causes changes in its PL content.

Use of an ivermectin bolus against gastrointestinal nematode and lungworm infections in first-year grazing calves

Two groups of first-year grazing cattle each were either left untreated as controls (group 1) or treated with an ivermectin bolus at turnout (group 2). Whereas group 1 suffered from dictyocaulosis, the bolus treated calves remained healthy. Shedding of lungworm larvae was completed prevented and gastrointestinal nematode egg output effectively reduced. During the 154 day grazing season the ivermectin bolus provided a season-long protection against parasitic gastroenteritis and bronchitis.

Malic dehydrogenase isoenzymatic pattern in lung-nematode parasite species

The malic dehydrogenase (MDH) isoenzymatic pattern of Dictyocaulus viviparus, Protostrongylus rufescens, and Slovakian and Spanish isolates of D. filaria was studied. The MDH isoenzymatic pattern in both isolates of D. filaria was characterized by the presence of three phenotypes: (1) a single, slow anodic band; (2) a single, fast anodic band; and (3) a large spot matching its migration with bands 1 and 2. These three phenotypes may be explained as the existence of only one gene locus for the MDH in D. filaria. Allelic frequencies and the Hardy-Weinberg test were determined for Slovakian and Spanish isolates of D. filaria. This test indicated that the population was not in Hardy-Weinberg equilibrium. The MDH isoenzymatic pattern of D. viviparus displayed the same phenotypes 1 and 2 observed in D. filaria. Furthermore, the MDH isoenzymatic pattern of P. rufescens was characterized by the presence of two bands with anodic and cathodic migration. The isoenzyme with anodic migration appeared more intensively stained than did that with cathodic migration. This last isoenzyme was not observed when the samples had been stored for 1 month.

Protective immunisation of guinea pigs against Dictyocaulus viviparus using excretory/secretory products of adult parasites

Parasite preparations were examined for their ability to induce protective immunity against Dictyocaulus viviparus in guinea pigs. Dunkin-Hartley strain guinea pigs were immunised with somatic extracts of adult parasites, somatic extracts of third stage larvae or excretory/secretory (ES) products from adult parasites. The groups were immunised twice with Freund's adjuvant four weeks apart and challenged with 6000 infective L3. Significant levels of protective immunity were observed only in the adult ES-immunised animals. The antibody responses of the different groups were compared following analysis by ELISA and immunoprecipitation. To examine the protective role of antibody, guinea pigs were passively immunised with serum from animals immunised with adult ES products or serum from guinea pigs exposed to experimental D. viviparus infection. Following challenge with infective L3, lung-worm burdens of these groups were significantly lower than in guinea pigs which received normal sera. The results suggest that D. viviparus adult ES products contain protective antigens and that antibody-mediated mechanisms contribute to immune protection.

Field evaluation of the efficacy of the fenbendazole slow-release bolus in the control of gastrointestinal nematodes of first-season grazing cattle

The ability of fenbendazole slow release bolus (Panacur SR Bolus, Hoechst) to control gastrointestinal parasitism in calves during their first grazing season at pasture was evaluated in two field trials. The infection level on both investigated farms was low and the control animals did not develop parasitic gastroenteritis. However, it was possible to demonstrate significant differences in the parasitological and biochemical parameters between the control and treated groups during the grazing season. Faecal egg counts and blood pepsinogen levels in the control cattle at both trials sites were significantly higher than those of the bolus-treated cattle.

An experimental field study on the build up of lungworm infections in cattle

The build up of lungworm infections was studied in four groups of calves. Calves of Group 1 were infected experimentally with 6 x 10 larvae during the first 3 weeks after turnout. The pasture of Group 2 was contaminated with approximately 35,000 larvae in June and the pasture of Group 3 with approximately 1.3 million larvae in August. Group 4 served as the helminth free control group for challenge infections with 5,000 larvae in October. In Group 1 faecal larval counts increased 5 weeks after the beginning of patency and decreased after another 3 weeks, indicating the development of immunity after the second lungworm generation. In contrast, the development of immunity in Groups 2 and 3 occurred after the first lungworm generation as maximal faecal larval counts were seen within 3.5 weeks after the beginning of patency. Infection levels were highest in Group 3 which was the only group showing clinical signs. These signs became worse after oxfendazole treatment.

The prevalence of patent lungworm infections in herds of dairy cows in The Netherlands

The results of a survey on the prevalence of patent lungworm infections in herds of dairy cows in the Netherlands are presented. Low patent infections were recorded in February-March on six out of 40 farms in at least one out of 40 cows. Between mid-April and mid-June low patent infections were detected on 28 out of 39 of these farms in one to four of 40 cows. Two farms on which cows were positive in the first round were negative in the second round. One to three positive cows were found on six out of a total of 15 farms revisited in July-August. These results show that lungworm infections are cycled within herds of dairy cows in the Netherlands at a low level. This indicates that dairy cows are important as carriers for lungworm, particularly in spring. The increased patency of lungworm in cows from winter to spring may be explained by maturation of inhibited larvae.

Further evaluation of a perfusion technique for the recovery of Dictyocaulus viviparus from bovine lungs

A further modification of a lung perfusion technique was evaluated by examining the recovery rate of 14-day-old Dictyocaulus viviparus worms from the excised lungs of 15 dead bovine calves. Up to 89% of the total number of worms found in 12 l of perfused fluid was recovered in the first 4 l collected. The application of this observation will increase the efficiency of the routine laboratory diagnosis of D. viviparus infection.