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.

Cattle respiratory disease in late summer and autumn

Increased diagnoses of husk in cattle are seen as summer turns into autumn. In this article, Arthur Otter of the APHA Cattle Expert Group discusses how the disease is diagnosed, and other respiratory diseases that it might be confused with.

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.

Lungworm of cattle in Malaysia

Bovine lungworm Dictyocaulus viviparus is highly endemic in temperate regions. However, the occurrence of the lungworm has not been reported in any South East Asian country. The main aim of the present study was to detect the presence of lungworm in cattle in peninsular Malaysia and to examine the morphology of the parasite. A cross-sectional study was carried out in which 602 animals from four large scale government cattle farms and one dairy smallholder farm were sampled. In addition, 283 lungs from 11 abattoirs around the country were examined. Faecal samples were examined using the Baermann technique while post-mortem examination was performed on the lungs. Approximately 5% of faecal samples and 1% of lungs were positive for lungworm. Based on the morphology of adult lungworm, eggs and first stage larvae, Malaysian bovine lungworms were D. viviparus.

Dynamics of infections with gastrointestinal parasites and Dictyocaulus viviparus in dairy and beef cattle from Costa Rica

A longitudinal survey was carried out to determine and describe the prevalence and intensity of gastrointestinal parasite infections and Dictyocaulus viviparus in a dairy and a beef cattle farm of two different ecological zones in Costa Rica. The influence of anthelmintic treatment, age and meteorological factors (rainfall, minimum and maximum temperatures) on gastrointestinal nematodes and D. viviparus counts was determined. Calves were subjected to monthly sampling of feces and blood between April 2002 and March 2003. Coprological techniques were used to detect gastrointestinal helminthes, protozoan and D. viviparus. Blood samples were analyzed for antibodies to D. viviparus by ELISA. The most prevalent gastrointestinal parasites detected on both farms (dairy cattle, A; beef cattle, B) were Eimeria spp. (94.7%, 93.7%), Strongylidae (75.0%, 81.4%), Buxtonella sulcata (38.0%, 21.6%) and Strongyloides papillosus (29.8%, 31.7%), whereas Moniezia benedeni (4.8%, 9.1%), Trichuris spp. (7.3%, 13.2%), Toxocara vitulorum (0.0%, 1.8%) and Entamoeba bovis (2.5%, 1.1%) were less prevalent. Mean fecal egg counts (FEC) showed highest values of Strongylidae in April, May and July (>335.3 eggs/g feces) on farm A, and April, May and August (>304.3 eggs/g feces) on farm B. S. papillosus presented low FEC throughout the year on farm A, on farm B the highest values were obtained in April (303.0 eggs/g feces). Trichuris spp. presented maximum FEC values in May (328.6 eggs/g feces) on farm A and in June (157.5 eggs/g feces) on farm B. Treatment and age had significant influence on infection intensity of Strongylidae (farms A and B), S. papillosus (farms A and B) and Trichuris spp. (farm A). Rainfall had significant effect on S. papillosus (farms A and B) and Trichuris spp. (farm B). Maximum temperature showed significant effect on S. papillosus (farm A) and Trichuris spp. (farms A and B). Minimum temperature had significant influence on Strongylidae (farm A), S. papillosus (farms A and B) and Trichuris spp. (farm B). Haemonchus spp. (57%, 66%) and Cooperia spp. (30.0%, 30.7%) were the most prevalent genera identified by coproculture on both farms, in contrast, Trichostrongylus spp. and Oesophagostomum spp. were less frequent. Patent lungworm infections were low on both farms (10.8%, 1.8%). On farm A, high prevalence of antibodies against D. viviparus was determined only at the beginning of the study, in contrast, on farm B the seroprevalence fluctuated throughout the year. Treatment, age and maximum temperature had significant effect on D. viviparus counts on farm A, but not on farm B.

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.

Prevalence of lungworm infection in sheep and cattle in the Kirikkale province

A slaughterhouse survey was performed for one year in order to determine the prevalence and intensity of lungworm infections in both sheep and cattle in the Kirikkale region. Thirty-four percent of 100 sheep examined were infected with lungworms and the species found in the infected lungs were Cystocaulus ocreatus (50.0%) and Dictyocaulus filaria (23.5%). Mixed infections were detected in 26.5% of the infected lungs. Worm nodules and brood nodules of C. ocreatus were observed in the lungs. The range of worm nodules was 1-116 (mean 19.7) and that of brood nodules, 1-5 (mean 2.8) per lung. D. filaria had a range that increased to a maximum of 45 worms (mean 11.5). Lungworms were observed in 14.0% of sheep fecal specimens. Larvae of C. ocreatus (52.4%) and D. filaria (28.6%) were found during examination of feces. Of the feces containing lungworms, 19% showed the presence of mixed infection. Lungworms were not found in cattle examined by autopsy and coprologic examination. C. ocreatus is the most prevalent lungworm species in Anatolia. D. filaria is another frequently seen lungworm species in Turkey while Dictyocaulus viviparus is very rarely reported in this country. It may be related to different humidity and temperature requirements for the development of free living larvae of the two Dictyocaulus species.

Relationship between bronchopulmonary nematode larvae and relative abundances of Spanish ibex (Capra pyrenaica hispanica) from Castilla-La Mancha, Spain

The excretion of bronchopulmonary nematode infective larvae was evaluated in 160 faecal samples of Spanish ibex (Capra pyrenaica hispanica) collected from 13 populations in Castilla-La Mancha, south-central Spain in September 2003. Intensities and prevalences were compared with pasture availability, abundances of wild and domestic ungulates at both levels, i.e. for populations and for faeces in a two-step procedure. Protostrongylid larvae showed similar infection rates (mean intensity: 1.56+/-0.12, n=94; mean prevalence: 25.62+/-6.86%, n=160) to Dictyocaulus spp. (mean intensity: 1.03+/-0.11, n=48; mean prevalence: 30.00+/-7.11%, n=160). At the population level, positive correlations were found between the prevalences of both bronchopulmonary taxa. The prevalence in both groups, but not intensity, also correlated positively with Spanish ibex abundance indexes both for the populations and individual faeces. These findings suggest that: (i) parasite spreading across Spanish ibex populations in Castilla-La Mancha could respond to host density-dependent processes; and (ii) these populations may have similar exposition and/or susceptibility to both bronchopulmonary taxa resulting in similar host-parasite patterns, despite their different life cycles. Bronchopulmonary outputs in the Spanish ibex from Castilla-La Mancha seems not to represent a health risk for this endemic wild ungulate but may be useful in any health surveillance scheme for the increasing populations of Spanish ibex.

Preventive vaccination of lactating and pregnant heifers against lungworm: safety and protection in three dairy herds

A study of the safety of a vaccine against lungworm was carried out with pregnant and lactating heifers from three dairy herds with a previous history of lungworm outbreaks in adult cows. Half of the heifers were vaccinated while the other half were not. A slight temporary cough following the vaccination was only observed in one herd. No adverse effects on pregnancy or milk production were seen. All heifers were serologically and coprologically examined before the first, before and after the second immunization, 3 months after introduction to pasture and at the end of the grazing season. Serological and faecal examination of the dairy cows before introduction into pasture confirmed the presence of at least one Dictyocaulus viviparus carrier in each herd. Lungworm infection occurred in all herds during the grazing season, most prominently in the herd with the highest number of heifers. In this herd, mild coughing associated with the lungworm infection was noticed, especially in the non vaccinated heifers. No other signs or symptoms were observed. It is concluded that a vaccine against D. viviparus can be used safely in heifers, before they are introduced into the adult herd, and that this vaccine can be used as a preventive measure against lungworm outbreaks in adult cattle.

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.

Non-invasive assessment of parasitic nematode species diversity in wild Soay sheep using molecular markers

Considerable effort has been put into detecting and identifying parasitic nematodes in live ruminants, but to date most studies are limited to a small group of nematodes and/or to experimentally infected sheep. In this study, a PCR-based assay using species-specific primer pairs, located in the second internal transcribed spacer ribosomal DNA, was developed to identify nine different species from six different families of parasitic nematodes in a wild, unmanaged and naturally infected population of sheep. Each primer pair was tested for its specificity and sensitivity and it exclusively amplified the species it was designed for and exhibited a high degree of sensitivity. The method was applied to eggs and cultured larvae to identify the parasitic nematodes present in a pooled faecal sample from several host individuals with unknown parasite burden. To test detection reliability, a faecal sample from an individual with known parasite burden (through post-mortem analysis) was also examined. All species present could be correctly identified by PCR, but detecting very low levels and/or early stages of infection proved to be difficult. The method was also tested for its applicability to high through-put screening of faecal samples.

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

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

[Lungworm disease in dairy cattle: symptoms, diagnosis, and pathogenesis on the basis of four case reports]

Clinical lungworm disease appears to occur frequently in Dutch dairy herds. Because the clinical diagnosis is difficult to make in adult cattle, the clinical diagnosis, laboratory diagnosis, differential diagnosis, therapy, and prevention are discussed in this article. In addition, four cases of lungworm disease in adult cattle are presented. The main clinical complaints were coughing, decreased milk production, and weight loss. Several lactating cows died in one herd. The disease history of four herds revealed that introduction of susceptible cows or heifers to herds with cows with subclinical patent lungworm infections had resulted in a pasture infection, leading to clinical problems in both the newly introduced and 'resident' cows of the herd. Further history analysis of the fourth herd revealed that re-introduction of lungworm infection by newly purchased cows in a lungworm free herd resulted in clinical lungworm problems in adult and young animals. The fourth case led to the conclusion that lungworm infection must have been re-introduced by cows purchased from another farm.

Molecular identification and prevalence of Dictyocaulus spp. (Trichostrongyloidea: Dictyocaulidae) in Swedish semi-domestic and free-living cervids

Lungs of 102 roe deer (Capreolus capreolus), 136 moose (Alces alces), 68 fallow deer (Dama dama), and six red deer (Cervus elaphus) were examined during hunting seasons from 16 September 1997 to 1 March 2000. The aim was to determine the species composition and prevalence of Dictyocaulus lungworms in these hosts in Sweden. Worms were identified following polymerase chain reaction (PCR) amplification of the internal transcribed spacer of ribosomal DNA (ITS2), followed by hybridization with four species-specific oligonucleotides. In addition, 50 lungworms from five reindeer (Rangifer tarandus) from Norway were similarly analyzed. A total of 399 worms were recovered and analyzed representing a range of 29-128 worms per host species. All specimens from roe deer were identified as Dictyocaulus capreolus, whereas those from red deer and reindeer were identical with D. eckerti. From moose, 73 (81.1%) of the worms were identified as D. capreolus whereas 17 (18.9%) were D. eckerti. The ITS2 sequence of fallow deer lungworms differed significantly when compared with the ITS2 of D. viviparus, D. capreolus, and D. eckerti. This indicated that fallow deer in Sweden may be infected with a new genotype of Dictyocaulus spp. Consequently, a specific probe designed for the ITS2 from this Dictyocaulus sp. hybridized exclusively with samples from lungworms of fallow deer. Interestingly, no D. viviparus were found in any of these hosts. The prevalence of infection in each host was as follows: D. capreolus in roe deer (14.7%) and moose (10.6%); D. eckerti in moose (0.7%) and red deer (33.3%); and Dictyocaulus sp. in fallow deer (10.3%). Regardless of lungworm species, the overall prevalence of Dictyocaulus spp. in these hosts was 12.2%. Prevalence between male and female animals and among the different age groups did not differ significantly. Finally an enzyme linked immunosorbent assay (ELISA) specific for patent D. viviparus infection in cattle was utilized to analyze lung tissue fluids from infected animals. All samples from roe deer, red deer, and fallow deer were negative in the ELISA. However, three out of twelve (25%) samples from moose and 17 of 40 (43%) samples from cattle were positive. This indicated that moose anti-D. capreolus antibodies recognized the D. viviparus antigen and that anti-cattle immunoglobulin cross-reacted with moose antibodies.

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.

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.

Bronchopulmonary helminths of roe deer (Capreolus capreolus) in the northwest of Spain

From 1993 to 1995, 148 hunter killed roe deer (Capreolus capreolus L.) from game reserves in Lugo (northwestern Spain) were examined for lungworm infection. The overall prevalence of infection was high (66.2%). Infections were comprised to two species, Varestrongylus capreoli and Dictyocaulus noerneri with a prevalence of 62.0 and 18.2%, respectively. Significant differences in the prevalence and larval burdens in lungs and faecal samples were observed between different locations. The highest overall prevalence of lungworm infection was observed in the large reserve at Ancares (78%) in comparison to that in smaller reserves (61.7%). Considering that the species recorded in this study are highly host-specific, it is unlikely that roe deer represent a significant reservoir of lungworm transmissible to domestic ruminants in northwestern Spain.

A field survey on the status of internal parasites in calves on organic dairy farms in southwestern Sweden

Infections with internal parasites are one of the most important causes of reduced productivity in first-grazing season cattle (FGSC). In conventional herds, nematode infections can be controlled by prophylactic anthelmintic treatments, but this is prohibited in organic production. The purpose of this investigation was to monitor the status of internal parasitism on 15 organic cattle enterprises in southwestern Sweden during the 1997 and 1998 grazing seasons, and to estimate the benefits of some management practices in parasite control. On each farm, the numbers of Eimeria alabamensis oocysts per gram of (opg) faeces were counted in seven fresh dung pats collected from the paddock 8-10 days after the turnout of FGSC. Faecal samples from 5 to 15 FGSC were also analysed for nematode eggs per gram (epg) faeces at four occasions during each grazing season. In addition, the FGSC and one group of second-grazing season cattle (SGSC) were weighed at turnout and housing and at the same time blood samples were collected, and analysed for serum pepsinogen concentration and antibodies against the lungworm, Dictyocaulus viviparus. On seven farms, 1-6 samples with more than 100000 opg were found, indicating considerable pasture contamination by E. alabamensis. However, clinical signs of coccidiosis were not observed. The highest outputs of nematode eggs were observed 45-55 days after turnout. More than 500 epg were only observed in 12 (2.2%) of the calves in 1997 and in three (0.6%) animals in 1998. Only 1% of the serum samples had pepsinogen values exceeding 3.6 U tyrosine, indicative of subclinical Ostertagia ostertagi infection. Lungworm infection was detected in five and nine herds in 1997 and 1998, respectively. The number of seropositive animals on these farms ranged between one (10%) and seven (70%). Clinical signs of dictyocaulosis were observed on two farms. The results indicate that dictyocaulosis is a problem in organic dairy herds in Sweden. On the other hand, the study shows that good management such as usage of parasite safe pastures and supplementary feeding may help control gastrointestinal parasites.

[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.

Susceptibility of elk to lungworms from cattle

Two studies were conducted to determine the infectivity of the lungworm, (Dictyocaulus viviparus) of cattle origin, in Rocky Mountain elk (Cervus elaphus nelsoni) or wapiti. In the first study, each of three 9-mo-old elk was administered 3,000 D. viviparus larvae from cattle using a nasogastric tube. In the second study, four 16-mo-old elk were each inoculated with 2,000 D. viviparus from cattle using a nasogastric tube. Elk were observed daily for signs of respiratory disease, and fecal samples were collected during the studies and evaluated for lungworm larvae using a modified Baermann technique. One elk was euthanatized during the patent period for recovery of adult lungworms, and three elk were euthanatized after larvae were no longer detected in feces. Lungworm larvae were not detected before inoculation in any of the 16-mo-old elk, but were detected 22 days after inoculation in one elk, 23 days after inoculation in two elk and 24 days after inoculation in all four elk. The prepatent period of this cattle isolate of D. viviparus in elk is therefore 22 to 24 days. The precise prepatent period was not determined in the three 9-mo-old elk, but larvae were detected in all three elk 25 days after inoculation. Numbers of larvae ranged from 1/ to 101/g feces with peak larval detection occurring 32 to 50 days after inoculation. Elk shed larvae from 22 to 83 days after inoculation, and patent periods of the parasite ranged from 24 to 62 days. Clinical signs of respiratory disease, with the exception of mild coughing after exercise, were not observed during the infections. Results from this experiment indicated that D. viviparus larvae of cattle origin can mature in elk and larvae can be passed in large numbers in feces, but this cattle isolate of D. viviparus was not highly pathogenic in elk.

Patterns of parasitic nematode infection and immunity in dairy heifers treated with ivermectin in a sustained-release bolus formulation either at turnout or in the middle of the grazing season

Twenty-eight Holstein-Friesian heifers, born the previous year and weighing between 130 and 310 kg, were allocated to one of two treatment groups by restricted randomisation, based on their initial weight. The heifers in group 1 were each treated with ivermectin in a sustained-release bolus formulation at turnout in April, and those in group 2 were each given an ivermectin bolus on July 10, 84 days after turnout. On that day the mean geometric worm egg counts of groups 1 and 2 were 0.4/g and 38.8/g, respectively, and they both had a mean plasma pepsinogen concentration of 0.59 iu/litre; in group 1, two of 14 faecal samples were positive for Dictyocaulus viviparus larvae, and in group 2 all 13 samples were positive; in group 1 eight calves were positive and three inconclusive for the presence of antibodies to D viviparus, and in group 2 the corresponding figures were 10 positive and two inconclusive; the mean liveweights of groups 1 and 2 were 274.4 kg and 262.8 kg, respectively. By December 4,231 days after turnout, the corresponding results were: mean geometric worm egg counts of 2.2/g and 0.5/g; one of 13 and none of 14 faecal samples positive for D viviparus larvae; 12 positive and two inconclusive and none positive and 10 inconclusive for the presence of antibodies to D viviparus; 214 days after turnout their mean liveweights were 361.1 kg and 358.3 kg. Although the patterns of parasitic nematode infection were different in the two groups during the grazing season, by the time they were housed both groups had achieved similar liveweights and showed evidence of an immune response to both D viviparus and gastrointestinal nematodes.

Nematode parasitism in adult dairy cows in Belgium

Over a period of 1 year, from November 1997 to October 1998, the abomasa, blood and faecal samples of 121 dairy cows in Belgium were collected and examined for nematode infections. Nematodes were present in the abomasa of 110 animals. Ostertagia was found in all 110, Trichostrongylus was seen in 65 and Haemonchus in 14 abomasa. Overall, 91% of all trichostrongyles recovered were Ostertagia. The geometric mean total number of Ostertagia was 2750, with an average of 74% inhibited early fourth stage larvae (EL4). Between November and February >90% of the Ostertagia worm burden were EL4 stages. The majority of the animals (56%) harboured a low Ostertagia burden (100-5000) and 15% had a high burden (>10,000). Sixty-four percent of the coprocultures were positive and the genera recovered were Ostertagia sp. (100%), Trichostrongylus sp. (42%), Oesophagostomum (32%), Haemonchus sp. (29%) and Cooperia sp. (16%). A seasonal pattern was evident for serum Ostertagia-specific antibodies and for serum pepsinogen concentration, with the highest levels during the summer, and low values during the winter. Dictyocaulus viviparus specific antibodies were detected in the serum of eight (7%) animals.

The efficacy of two isolates of the nematode-trapping fungus Duddingtonia flagrans against Dictyocaulus viviparus larvae in faeces

A series of experiments was carried out to examine the effects of two different isolates of the nematode-trapping fungus Duddingtonia flagrans to reduce the number of free-living larvae of the bovine lungworm, Dictyocaulus viviparus. A laboratory dose-titration assay showed that isolates CI3 and Troll A of D. flagrans significantly reduced (P < 0.05 to P < 0.001) the number of infective D. viviparus larvae in cultures at dose-levels of 6250 and 12,500 chlamydospores/g of faeces. The larval reduction capacity was significantly higher for Troll A compared to CI3 when lungworm larvae were mixed in faecal cultures with eggs of Cooperia oncophora or Ostertagia ostertagi and treated with 6250 chlamydospores/g of faeces. Both fungal isolates showed a stronger effect on gastrointestinal larvae than on lungworm larvae. Two plot trials conducted in 1996 and 1997 involved deposition of artificial faecal pats containing free-living stages of D. viviparus and C. oncophora on grass plots. Herbage around the pats was collected at regular intervals and infective larvae recovered, counted and identified. These experiments showed that both D. flagrans isolates reduced the number of gastrointestinal as well as lungworm larvae in faecal pats. During both plot trials, the transmission of C. oncophora larvae, but not D. viviparus, from faecal pats to the surrounding herbage was clearly affected by climatic conditions. After collection of faecal pats from the grass plots one month after deposition, the wet and dry weight of pats as well as organic matter content were determined. No differences were found between the fungus-treated and non-treated control pats. This indicated that the rate of degradation of faeces was not affected by the addition of the fungus.

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.

An attempt to control lungworm disease and parasitic gastroenteritis on commercial dairy farms by the use of an adaptation of Michel's dose-and-move system

On seven dairy farms an attempt was made to control lungworm disease in calves by turnout on a pasture grazed earlier by cows, followed by a move to aftermath and ivermectin treatment 2 months later. Transmission of lungworm was observed on all farms. Lungworm disease occurred on four farms at treatment. Coughing re-occurred on three of these farms in some animals 2 months later. Owing to poor performance between turnout and treatment, weight gain was below the norm on the farm with the highest infections and most severe respiratory signs. On the other farms respiratory signs did not result in poor weight gain. Gastrointestinal nematode infections remained low on all farms. The conclusion is that this dose and move scheme cannot be recommended for the control of lungworm.

Field evaluation of a fenbendazole slow release bolus in the control of nematode infections in first-season cattle

The efficacy of a fenbendazole slow release bolus in controlling nematode infections of first-season cattle was evaluated in a field study in northern Germany. Two groups, each of 11 male calves, were set-stocked on separate pastures from May until October 1989 (157 days). The animals of one group were given the bolus at turnout and the animals of the control group were treated with fenbendazole (7.5 mg/kg bodyweight) eight weeks after turnout. Clinical inspections and measurements of faecal egg and larval counts, herbage trichostrongyle larval counts, plasma pepsinogen concentrations and bodyweight were made throughout the study. All the animals were slaughtered for worm counts and the evaluation of carcase quality two weeks after housing. The pasture grazed by the control group showed a marked increase in trichostrongyle larvae from late August onwards and, as a result, the control calves had increasing faecal egg counts and increased plasma pepsinogen concentrations in the latter part of the grazing season, although no clinical signs of parasitic gastroenteritis were apparent. The fenbendazole slow release bolus suppressed the trichostrongyle infections during the grazing season, and larval counts on the pasture grazed by the bolus-treated group remained low throughout the study. Postmortem examination showed that the bolus-treated calves harboured significantly (P < 0.01) fewer trichostrongyle worms, including inhibited stages, than the controls. Because of an inadequate lungworm challenge during the grazing season it was not possible to evaluate the efficacy of the fenbendazole slow release bolus in preventing parasitic bronchitis. At slaughter, the bolus-treated animals weighed more than the controls and tended to have a better carcase quality.

The sensitivity of the Baermann method for the diagnosis of primary Dictyocaulus viviparus infections in calves

Data from calves infected experimentally with 20 larvae of Dictyocaulus viviparus demonstrate that the Baermann method, using 30 g of faeces per calf is extremely sensitive for diagnosis of patent infections in young cattle. Between 5 and 7 weeks after primary infection it is sensitive enough to diagnose the presence of one patent female worm.

Persistence of the efficacy of pour-on and injectable moxidectin against Ostertagia ostertagi and Dictyocaulus viviparus in experimentally infected cattle

The persistence of the efficacy of moxidectin 0.5 per cent pour-on and moxidectin 1 per cent injectable against Ostertagia ostertagi and Dictyocaulus viviparus in calves was studied in two experimental trials. In the first trial two groups of seven calves were treated with either the pour-on or the injectable formulation, while a third group remained untreated. All the animals were infected daily from Monday to Friday with infective stages of O ostertagi and D viviparus between the day of treatment (day 0) and day 33, and were necropsied for worm counts three days later. The experimental design of the second trial was similar to that of the first but the period of infection was from 28 to 45 days after the treatment, and the necropsy was five days after the last infection. In both trials both moxidectin formulations had very high efficacies (99.6 per cent) against adult and developing stages of O ostertagi and D viviparus. The higher efficacy of the moxidectin pour-on preparation against early fourth stage larvae in both trials suggested that its effect was more persistent. It was calculated that the efficacy of moxidectin against O ostertagi persisted for at least five weeks for the injectable formulation and six weeks for the pour-on. The efficacy of moxidectin against D viviparus lasted for at least six weeks for both formulations.

Nematode-trapping fungi in biological control of Dictyocaulus viviparus

Larvae of the cattle lungworm Dictyocaulus viviparus were cultured in experimental units of 200 g cattle faeces placed in semi-transparent trays in the laboratory. In each of 4 experimental series using this experimental unit, chlamydospores (chl) of the nematode-trapping fungus Duddingtonia flagrans were admixed to half of the faecal cultures in a concentration of 50.000 chl/g. In all 4 series there was a significant reduction in the development and subsequent release of infective lungworm larvae from faecal cultures containing chlamydospores. The average reduction in larval release, caused by fungal spores, was 86%.

Species-specific polymerase chain reaction for the differentiation of larvae from Dictyocaulus viviparus and Dictyocaulus eckerti

Using substantial interspecific differences between the second internal transcribed spacer (ITS2) region within the rDNA gene of Dictyocaulus eckerti and Dictyocaulus viviparus a species-specific PCR was developed to distinguish between lungworm larvae of the two species from fallow deer and cattle. It was found that the method of DNA extraction was crucial for the sensitivity of the PCR. With serial dilutions of DNA extracted from 10,000 larvae the ITS2 fragment could be amplified from all dilutions down to a calculated amount of DNA equivalent to one larva. Using lower numbers of larvae, DNA from at least 100 larvae was necessary for a successful amplification. From this extraction a species-specific polymerase chain reaction (PCR) product was generated with a calculated amount of DNA equivalent to 33 larvae, whereas amplification of further diluted DNA was not successful. However, in a direct PCR single larvae could be detected after direct PCR amplification without preceding DNA extraction.

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.

Prophylaxis of bovine trichostrongylidosis and dictyocaulosis in the alpine region: comparison of an early and late administration of the oxfendazole pulse release bolus to first year grazing calves

The effect of the oxfendazole pulse release bolus (OPRB) administered at turnout, in May, or in mid-July on the development of infections with gastrointestinal nematodes and lungworms in first year grazing calves was investigated with three groups of nine animals, all grazing the same pastures in the Swiss midland region. In the calves of Group A (OPRB on 21 May) less than 20 eggs per gram of faeces (e.p.g.) and less than three Dictyocaulus larvae per 10 g (1.p.10 g) of faeces were shed for a period of 126 and 140 days respectively. Towards the end of the grazing period calves of this group excreted significantly higher levels of lungworm larvae (P < 0.05) compared with the other groups. Prior to OPRB administration on 14 July, the calves of Group B developed subclinical infections with trichostrongyles and lungworms which were similar to the untreated control Group C. By 4 weeks after bolus-administration the excretion of trichostrongylid eggs and lungworm larvae declined to levels below 20 e.p.g. and six l.p.10 g respectively. Serum pepsinogen values of the calves of Groups A and B were significantly lower (P < 0.05) compared with the control animals on days 84 and 98 after turnout and reflected mainly subclinical infections. With the exception of one Group A calf developing clinical parasitic gastroenteritis (p.g.e.) at the end of the season, clinical disease was not observed in the treated calves, while seven out of nine control animals grazing on the same pastures exhibited clinical p.g.e. with mean serum pepsinogen values exceeding 4400 mU tyrosine. Calves of Groups A and B gained significantly more weight (P < 0.01) compared with Group C (+36 kg and +41 kg respectively); differences between Groups A and B were not significant. The results indicate that in mixed grazing systems of treated and untreated calves, which are often found in the alpine region, administration of the OPRB in May or July provided good results with respect to performance of the calves. However, late administration of the OPRB has the additional advantage of coverage of the period of higher infection risk with trichostrongyles and lungworms in the late season until stabling, and should therefore be recommended.

Comparison between fenbendazole and moxidectin applied in a dose and move system for the control of Dictyocaulus viviparus infections in calves

A grazing study was performed with the main objective to compare the effect of moxidectin (MDT) and fenbendazole (FBZ) in a 'dose and move' system on nematode infections in calves with special emphasis on Dictyocaulus viviparus. Three groups of six calves were grazed from May to October 1994. All groups grazed together until 9 weeks after turnout when they were moved to separate mowed pastures. One group (MM) was then treated with 0.5 mg kg-1 MDT pour-on, the second group (FM) was treated with 7.5 mg kg-1 FBZ drench and the third group served as untreated pasture control group (PC). Two calves from MM and two from FM were experimentally infected with 20 lungworm larvae at turnout in order to initiate low infections in the herd. Pairs of tracer calves grazing during the first 7, 8 or 9 weeks after turnout acquired mean burdens of 218, 255 and 1156 lungworms, respectively. MDT and FBZ treatment removed adult lungworms from MM and FM. In PC faecal larval counts increased until the end of July, when most animals were suffering from lungworm disease. No lungworm disease occurred in both dose and move groups. In FM larvae reappeared in the faeces of some of the calves from 1 month after treatment and low patent infections remained to be present in FM in some calves until the end of the experiment. No reappearance of larvae after treatment was observed in MM. The mean Optical Density (OD) values of the three groups on pasture closely followed the infection patterns. After housing in October all calves, and also a group of five permanently housed non-infected control calves (HC), were infected experimentally with 5000 D. viviparus larvae to evaluate development of immunity. The worm counts at necropsy showed that groups on pasture had developed immunity. However, the degree of immunity was lower in MM than in FM and PC.

Evaluation of the effect of the fenbendazole sustained-release intraruminal device on the immunity of calves to lungworm

Each of 10 set-stocked calves was given a fenbendazole sustained-release intraruminal bolus at turnout for the control of parasitic bronchitis while a group of 10 similar calves was left untreated. The respiratory rates of the control calves were not greatly increased during the grazing season, but persistent coughing was evident from early July when they all had patent lungworm infections. Only occasional coughing was reported from the bolus-treated calves except for a transient increase in its frequency in late September. In mid-August, one of the treated calves was passing lungworm larvae and when they were housed six of the 10 had patent infections. In August tracer calves picked up an average of 23.5 lungworms per day from the control paddock but only 2.1 from the paddock grazed by the treated calves. In September the corresponding figures were 7.6 and 19.2 lungworms per day, respectively, from the control and 'treated' paddocks. After housing, the post mortem worm counts after an experimental challenge with Dictyocaulus viviparus larvae were reduced by 99.2 and 98.7 per cent (P < 0.0001), respectively, for the control and bolus-treated calves in comparison with weight-matched parasite-naive calves. Thus, despite a relatively low level of challenge during the grazing season, the treated animals had developed a considerable degree of protective immunity.

Development of immunity to lungworm in vaccinated calves treated with an ivermectin sustained release bolus or an oxfendazole pulse release bolus at turnout

The ivermectin sustained release bolus (IVSRB), when used at turnout as recommended, will provide season-long control of parasitic bronchitis, thus obviating the need for use of a lungworm vaccine. However, some concerns have been expressed that calves treated with an IVSRB will receive so little exposure to Dictyocaulus viviparus that it will compromise their immunity in subsequent grazing seasons, which would be of particular importance in dairy herds. Although there is evidence that IVSRB-treated calves can develop immunity to D. viviparus when exposed to pasture infection, it was considered worthwhile to evaluate the compatibility of the IVSRB and lungworm vaccination to allow veterinary surgeons the option of using these products concurrently when they have particular concerns about the long term immune status of replacement dairy heifers. Thirty-two dairy replacement heifers were vaccinated with two doses of lungworm vaccine and, at turnout, half the calves received an IVSRB and the remainder an oxfendazole pulse release bolus (OPRB). At the end of the grazing season four replicate bolus treated pairs and four parasite-naive calves were challenged with 1000 D. viviparus infective larvae. At slaughter there was a 95% and 93% reduction in D. viviparus burdens in the IVSRB and OPRB treated calves respectively, compared with the unvaccinated, untreated controls. These results indicate that where it is considered necessary to use lungworm vaccination in addition to an IVSRB or an OPRB, the compatibility of these products with lungworm vaccine will allow development of a protective level of immunity to D. viviparus.

Response of cattle treated with a fenbendazole slow release bolus to challenge from nematodes the following season

Nematode infection of cattle treated in their first year at pasture with the fenbendazole slow release bolus ('Bolus group') was compared during the second year with that of untreated cattle. Ostertagia was the most prevalent parasite associated with Cooperia. Except for the Dictyocaulus spp. which caused clinical signs of bronchitis in the 'Bolus' group, the infection during the second year resulted in a moderate response of the cattle whatever the group. Rises in both pepsinogen and gastrin levels were correlated with the number of Ostertagia L3 on herbage. Damages in the abomasal mucosa were more frequent and severe in the 'Bolus' group where more inflammatory signs were observed in spite of a smaller number of worms. Nevertheless, the differences in total weight gains were not significant thanks to a compensatory effect during the second part of the grazing season in the 'Bolus' group. Hypotheses related to a minimum threshold of infection during the first year necessary to develop high enough protection during the second year are discussed. The pathological effects of gastrointestinal nematodes seem to vary more according to the inflammatory response than to the number of worms.

The combined effect of fenbendazole treatment and a move to aftermath 7 or 9 weeks after turnout on Dictyocaulus viviparus infections in calves

A grazing study was performed with the main objective of examining the effect of fenbendazole (FBZ) in a 'dose and move' system on nematode infections in calves with special emphasis on Dictyocaulus viviparus. Three groups of six calves were grazed from May to October 1993. One group (DM7) was treated with FBZ and moved to aftermath (pasture which had only been mown) 7 weeks after turnout. The second group (DM9) was similarly treated and moved 9 weeks after turnout and the third group served as untreated pasture control group (PC) and was moved to aftermath 9 weeks after turnout. FBZ treatment removed adult lungworms from DM7 and DM9. Tracer calves grazed during the first 7 or the first 9 weeks after turnout acquired mean burdens of 18 and 125 lungworms, respectively. In PC faecal larval counts increased until the end of August. Most of the animals in this group were then suffering from lungworm disease and emergency treatment with ivermectin was given. In both FBZ-treated groups, larvae reappeared in the faeces of some of the calves 4-5 weeks after treatment. Subsequent reinfection resulted in higher mean faecal larval counts in both groups 2 months after treatment, although variation in faecal larval counts was high. In DM7 values tended to be higher than in DM9. These higher larval counts were associated with mild signs of parasitic bronchitis in some calves of DM7, whereas no signs were seen in DM9. At the end of the experiment, all calves, and also a group of six permanently housed non-infected control calves (HC), were infected experimentally with 5000 D. viviparus larvae to evaluate development of immunity. The worm counts at necropsy showed that all calves on pasture had developed immunity.

An evaluation of abamectin given at turnout and six weeks after turnout for the control of nematode infections in calves

Two groups of 16 set-stocked calves were used to evaluate a new strategy for the prevention of parasitic bronchitis and parasitic gastroenteritis. One group was left untreated while the calves in the other were treated with abamectin at 0.2 mg/kg at turnout and again six weeks later. The treatment prevented the output of nematode eggs and lungworm larvae in faeces for at least 70 days. The number of infective larvae subsequently appearing on the pasture was reduced by 90.2 per cent and the infectivity of the pasture (as monitored by tracer calves) by 96.0 to 99.8 per cent in the case of Dictyocaulus viviparus, 88.2 to 99.2 per cent for Ostertagia ostertagi and 69.3 to 98.1 per cent for Cooperia oncophora. Parasitic bronchitis occurred in the control calves and both bronchitis and gastroenteritis in the tracer calves grazing the paddock grazed by the control calves, but no disease occurred either in any of the calves treated with abamectin or in the tracer calves grazing the paddock grazed by these calves.

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.

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.

Study on the causes of outbreaks of lungworm disease on commercial dairy farms in The Netherlands

The causes of outbreaks of lungworm disease were determined from the herd histories of 25 affected herds of young cattle. The results indicate that light pasture contamination by carriers and subsequent auto-infections are the most prominent cause of lungworm disease, followed by heavy pasture contamination by carriers. Overwintered pasture infections seem to play a minor role. Adult dairy cows seem to be the predominant carrier animal when light pasture infections are concerned. Heavy pasture infections are almost always caused by calves and yearlings.

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.