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.     

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.     

A survey on Dictyocaulus viviparus antibodies in bulk milk of dairy herds in Northern Germany

Parasitic bronchitis caused by the bovine lungworm, Dictyocaulus viviparus, occurs worldwide in temperate areas. The parasite is found predominantly in calves and heifers, but dairy cattle can suffer from lungworms when they become infected for the first time or if they have lost immunity due to lack of exposure to lungworm larvae during the grazing season. The present study was performed to determine the D. viviparus bulk milk antibody prevalence in dairy herds in the East Frisian region of northwestern Germany, Lower Saxony, by analysing bulk milk samples collected in January (860 samples), September (866 samples) and November (860 samples) 2008, thereby representing 906 dairy farms. These samples were tested for antibodies against D. viviparus by a milk ELISA. This test detects patent infections only since it is based on recombinant major sperm protein as antigen. While in January 12.8% of dairy farms were positive for D. viviparus antibodies, the bulk milk samples collected in September and November revealed 6.9% and 6.6% positive dairy herds. From the 906 dairy farms included in the study, 191 (21.1%) tested positive at least once for antibodies against lungworm. From 810 dairy farms from which bulk milk samples were obtained during all three samplings, 146 (18.0%) farms were positive at one sampling date, 27 (3.3%) at two, and 4 (0.5%) on all three sampling dates. The majority of the farms represented in the study belonged to four districts of East Frisia, which showed no significant difference in the proportion of positive dairy farms.     

Seroepidemiological study of Neospora caninum infection in dogs found in dairy farms and urban areas of Aguascalientes, Mexico

The objective of this study was to describe the seroepidemiology of Neospora caninum infection in dogs in close contact with dairy cattle and dogs from urban areas of Aguascalientes, Mexico, as well as to estimate the possible association between age, gender and size of these groups and seroprevalence. Sera were obtained from samples of 152 dogs in dairy farms and 116 in the urban area, and were subjected to ELISA test. General seroprevalence reached 32%, while the seroprevalence in farm dogs (41%) was significantly higher than in dogs from the urban area (20%) (p<0.05). Regarding age groups, general seroprevalence was greater among dogs between 11 and 15 years of age (67%) remaining equal between males and females (32 and 31%, respectively). Nevertheless, females resident in farms had a higher seroprevalence (42%) than female resident in the urban area. Regarding size, large-sized animals had greater seroprevalence in farms (58%), while in the urban area medium-sized animals were those that had the highest seroprevalence (27%). It was found that dairy farm dogs had a higher risk of infection (OR=2.79; p=0.0004), and that in said group, the age range from <1 to 5 years of age was identified as a risk factor (OR=3.11, p=0.001).     

The value of a bulk-tank milk ELISA and individual serological and faecal examination for diagnosing (sub)clinical Dictyocaulus viviparus infection in dairy cows

To test the value of a recently developed bulk-tank milk (BTM) ELISA for diagnosing (sub)clinical Dictyocaulus viviparus infection in lactating dairy herds under field conditions, bulk milk samples were collected from farms with or without clinical symptoms suspected to be caused by lungworm infection. Results of the BTM ELISA were compared against individual examinations for lungworm larvae in faeces and lungworm antibodies in serum from up to 20 heifers (parity 1) and up to 20 cows (parity ≥ 2) on the same farms. This also allowed, for the first time, to examine the value of individual faecal and serological examinations in the diagnosis of (sub)clinical lungworm infections. In total, 33 farms participated. Of these, 16 reported clinical symptoms possibly related to lungworm infection (defined as a suspected positive clinical status or CS(+)) and 17 reported having no such symptoms (CS(-)). In total, 503 heifers and 649 cows were sampled. Of all faeces samples positive for lungworm larvae, 94 were from heifers (18.9% of all heifers) and 75 from cows (11.7% of all cows) (P<0.001). Of all sera positive for lungworm antibodies, 130 were from heifers (26.1% of all heifers) and 113 from cows (17.5% of all cows) (P<0.001). Of the CS(-) farms 41% had at least one heifer or cow shedding larvae and 71% had at least one seropositive heifer or cow. Of the CS(+) farms this was 81% and 94%, respectively. There were only 4 farms, all CS(-), where none of the animals were found shedding larvae and all animals tested seronegative. This implies that on 76% of the CS(-) farms lungworm infection circulated unnoticed. On all CS(+) farms the suspicion that lungworm caused the respiratory symptoms was confirmed by the individual faecal and serological examinations, whereas the BTM ELISA confirmed presence of lungworm on half of the CS(+) farms. The latter in particular occurred on farms with the more severe outbreaks. Overall, of 32 available BTM samples 10 tested positive (8 of 15 CS(+) and 2 of 17 CS(-) farms). For diagnosing suspected lungworm disease it was concluded that testing a BTM sample might suffice in case of moderate to severe outbreaks. However, in case of a mild outbreak with just a few animals coughing, examining individual animals has to be preferred over testing a BTM sample. The likelihood to detect lungworm infection is higher if heifers are sampled compared to cows. Sensitivity of the BTM ELISA was 35.7% if the presence of at least one seropositive and/or one larvae shedding animal in the herd was used to define lungworm positive farms. On average, at least 30% of the herd had to be seropositive before the BTM ELISA was found positive for lungworm antibodies. Results indicate that the BTM ELISA in its current form does not appear to be suitable for surveys on the prevalence of lungworm presence on farms. However, this BTM ELISA might be used in large-scale surveys to detect, for instance, annual changes in percentage positive farms, as long as it is recognized that positivity is more closely related to incidence of lungworm disease than to prevalence of lungworm infection.     

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

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

Preliminary investigation into the usefulness of the indirect haemagglutination

Summary

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

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

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

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

Failure to eradicate the lungworm Dictyocaulus viviparus on dairy farms by a single mass-treatment before turnout

On two dairy farms it was attempted to eradicate lungworm, Dictyocaulus viviparus, by means of a single mass-treatment of all cattle that had been grazed the previous year(s), before turnout in the spring. Both farms experienced two years of lungworm outbreaks in the adult dairy herd prior to this study. Following confirmation that both herds contained lungworm carriers, all animals older than approximately 6 months were treated with eprinomectin in March 2007. One week after treatment none of the animals were shedding lungworm larvae. Subsequently, animals were pastured according to normal farm routine. From August to November all first-calving heifers were coprologically and serologically monitored for lungworm infection. During 2007 both farms remained lungworm-negative and did not report any clinical sign indicative for a lungworm infection. The following year, on one of the farms replacements grazing on cow pastures, started showing signs of parasitic bronchitis which was serologically confirmed. The other herd remained free of parasitic bronchitis until at least the fourth year after the mass treatment, although some coughing was noticed in 2008 among first-lactation heifers. It was concluded that a single mass-treatment before the grazing season may be useful to break a series of annual lungworm outbreaks. However, it is not a secure method to prevent parasitic bronchitis for more than one year.     

Preliminary investigation into the usefulness of the indirect haemagglutination

Summary To give an impression of the usefulness of indirect haemagglutination (IHA) in the diagnosis of lungworm infections in cattle under practical conditions, five calves vaccinated against Dictyocaulus viviparus and five unvaccinated calves were periodically subjected to clinical, parasitological, and serological examinations over a period of seven months. All calves grazed on a lungworm-infected plot. 82% of the observations in unvaccinated calves, which were positive with respect to one or more of the used parameters, concerned IHA-positive animals which, however, showed negative results with the parasitic parameters. The titre variation of the serological examination was a further indication of the fact that the IHA detected antibodies against lungworm antigens. No indications of false positive reactions were obtained. An investigation carried out on 46 farms on the correlation between serological and clinical findings on lungworm infections revealed a positive correlation in 80% of the groups between results obtained with both methods. The authors consider that IHA offers good prospects for the diagnosis of lung-worm infections.     

Risk factors for canine neosporosis in farm and kennel dogs in southern Italy

Neosporosis by Neospora caninum causes losses to livestock production through abortion in cattle while, in dogs, it induces neuromuscolar disease. This study investigated neosporosis seroprevalence associated risk factors (including the seropositivity to leishmaniosis) in dogs of southern Italy, determined the prevalence of N. caninum oocyst shedding and examined the relationship between seroprevalence of neosporosis in farm dogs and cattle. Using an inhibition ELISA, 20.9% of 306 dogs had percent inhibition values >10 (indicative of exposure) and farm dogs had a significantly (p<0.001) higher seroprevalence than dogs in a rescue kennel. Whilst N. caninum seroprevalence was associated with increasing age in dogs (p< or =0.01) there was no association between seropositivity for N. caninum and for Leishmania infantum. Oocysts of N. caninum were not detected in faecal samples from 230 dogs including 160 farm dogs. The results indicated that neosporosis infection is common in southern Italy both in dogs and in cattle and that dogs at higher risk of exposure are free-ranging ones living in farms. The lack of correlation between canine seroprevalence for N. caninum and L. infantum assumes a particular significance in an endemic area for leishmaniosis.     

Sero-epidemiological survey of Dictyocaulus viviparus infections in first-season grazing calves in The Netherlands

A sero-epidemiological survey of Dictyocaulus viviparus infections in calves was carried out using an enzyme-linked immunosorbent assay. Infection level with D viviparus was correlated with farm, herd and management characteristics. At least 75 per cent of the herds were infected with D viviparus. Calves on zero-grazing farms were infected at a lower level than calves grazing pasture. No regional differences in infection rate were observed. On 15 per cent of the farms calves had clinical husk while 51 per cent of farms had experienced husk in the past. A higher level of infection was seen when calves were housed later in the autumn. The number of calves grazing together and the stocking rate had a significant positive influence on the level of infection. No significant difference in the occurrence of clinical husk was observed between calves vaccinated against lung-worm disease and calves not vaccinated against the disease.     

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.     

Dictyocaulus species: cross infection between cattle and red deer

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

Primary anthelminthic screening on the L4 and L5 developmental stages of the lungworm, Dictyocaulus viviparus, in guinea pigs

The study was aimed at expanding the primary anthelmintic screening to cover a model of the group of pulmonary nematodes; in this particular case to introduce the lungworm, D. viviparus, in laboratory animals. A method of primary screening for the fourth and fifth larval states of D. viviparus in guinea-pigs was worked out after the selection of a suitable laboratory host. In the primary screening, three well-known anthelmintics of the benzimidazol series, including fenbendazole, mebendazole and levamisol, were tested by the method of controlled test. The anthelmintics were administered at the recommended doses of 7.5 and 10.0 mg per kg of live weight for two days in succession. The effectiveness of the control of the 4th and 5th larval states of D. viviparus was 93.4% in fenbendazole, 89.0% in mebendazole, and 89.9% in levamisol. It is confirmed by the results of the trials that guinea-pigs can be used for the testing model of the lungworm, D. viviparus, in anthelmintic screening.     

An outbreak of dictyocaulosis in lactating cows on a dairy farm

CASE DESCRIPTION: The owner of a herd of 74 Holstein-Friesian cattle reported decreased milk production, weight loss, and coughing among lactating cows. Owner-initiated antimicrobial treatment was unsuccessful; 1 lactating cow died, and 50% of the lactating cows had clinical signs of respiratory distress, such as tachypnea and coughing. CLINICAL FINDINGS: On the basis of history, physical examination findings, and fecal examination results, affected animals were determined to have Dictyocaulus viviparus (lungworm) infestation. The disease history suggested that the herd contained cows with subclinical patent lungworm infestations; after introduction of susceptible heifers, the pastures had become heavily infested with D viviparus and clinical problems subsequently developed in both newly introduced and resident cows. TREATMENT AND OUTCOME: Affected and unaffected heifers and adult cows were treated with a pour-on formulation of eprinomectin (0.5 mg/kg [0.23 mg/lb]). One animal died, but 2 weeks after treatment, clinical signs among affected cattle were markedly improved. Ten weeks after treatment, milk production improved from 23 kg/cow/d (51 lb/cow/d) to 28 kg/cow/d (62 lb/cow/d). CLINICAL RELEVANCE: The outbreak provides additional evidence that dictyocaulosis is becoming more common among adult dairy cattle, rather than almost exclusively affecting young stock. This may be attributable to anthelmintic use and management practices on dairy farms. Combined with anecdotal reports of an increase in the incidence of dictyocaulosis among adult cattle in North America, D viviparus infestation should be included as a differential diagnosis for decreased milk production, weight loss, and coughing among adult dairy cattle.     

Management practices and use of anthelmintics on dairy cattle farms in The Netherlands: results of a questionnaire survey

In December 1996, a questionnaire about farm management and parasite control measures in calves was sent to 956 randomly chosen dairy cattle farmers in The Netherlands. Another 150 farmers in the vicinity of Deventer who had vaccinated their calves in 1995 against lungworm were approached with the same questions. Our objective was to investigate the consequences on worm control of the withdrawal of the lungworm vaccine from the market for reasons of possible BSE contamination of the vaccine. Of the returned questionnaires, 411 (43%) of the `at random' group and 89 (59.3%) of the `Deventer' group were valid. The most important data with regard to the farms of the `at random' group (411) were: mean area 31.6 ha, mean number of calves 23, heifers 23 and milking cows 53. Sheep (mean 37) were present on 18.3% of the farms. With regard to management: 74.5% of the farmers turned the calves in their first year onto pasture, 25.5% kept them indoors. The average time on pasture was ca. 5 months. Rotational grazing was practised on 81.4% of the farms, on 18.6% calves were set stocked. The first pasture of the calves was mown before turn-out on 72.9% of the farms. On 48.2% of these farms, calves were always moved to mown pastures. With regard to treatments: 33.8% of the farmers vaccinated their calves against lungworm in the years 1993, 1994 and 1995. Despite the withdrawal of the vaccine from the market in 1996, 7.2% of the farmers vaccinated their calves as recommended, with two doses, and 13.1% with a single dose. At turn-out, 41.5% of the farmers gave the calves a preventive anthelmintic treatment. Of these treatments, 66.9% were sustained of pulse release long acting devices. During the grazing season, 36.6% of the farmers treated their calves. After housing, 50.3% of the farmers gave a treatment. Signs of lungworm infection were noticed on 18.6% of the farms. Of the `Deventer' group (89 farmers), 96.6% turned the calves out. Of these farmers, 86.0% had used the lungworm vaccine in 1995. In 1996, 52.7% of the farmers had vaccinated the calves: 36.5% with a single dose and 16.2% with the double dose. Of the 35 farmers who did not vaccinate in 1996, 62.9% gave a preventive treatment at turn-out. Clinical signs of lungworm infection were not observed on the 12 farms which vaccinated the calves twice. On 11% of the farms which vaccinated once and on 14% of the farms which did not vaccinate, signs of lungworm infection were observed. It is concluded that more than 80% of Dutch dairy cattle farmers take appropriate measures to control gastrointestinal nematode and lungworm infections in calves in their first grazing season by grazing on aftermath, rotational grazing on mown pastures combined or not with preventive anthelmintic treatments. However, combinations of aftermath grazing and preventive treatment occurred on 30% of the farms. This may be overprotective and may prevent sufficient build up of immunity, causing worm problems at a later age. The withdrawal of the lungworm vaccine from the market did not cause a rise in lungworm problems. Some farmers did vaccinate, despite the withdrawal. The majority used other preventive treatment measures, mainly the application of long acting boli.     

Evaluation of the efficacy of doramectin against an artificial infection of Dictyocaulus viviparus in calves

Three groups of eight Friesian calves, reared parasite-free, were experimentally infected with 1000 infective larvae of Dictyocaulus viviparus. Two groups were injected subcutaneously with 1% doramectin at 0.2 mg/kg body weight, one group 5 days after infection and the other 25 days after infection. A third group served as untreated controls. Faecal samples were examined for lungworm larvae on days 28, 32, 33, 34 and 35 after infection; the calves were killed and necropsied 39 or 40 days after infection and any lungworms present recovered and counted. Doramectin proved 100% effective against both 5-day-old and mature D. viviparus infections.     

Dictyocaulus infection in farmed red deer (Cervus elaphus)

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

Validation of a Dictyocaulus viviparus MSP-ELISA and cut-off adjustment in a one-year longitudinal field study in dairy cattle herds

A one-year field study analysing lungworm seropositivity by use of the MSP-ELISA was performed (1) to investigate the antibody dynamics in individual milk samples following field (re-)infections of dairy cows with the bovine lungworm Dictyocaulus viviparus, (2) to investigate the correlation between individual and bulk tank milk (BTM) antibody titres and (3) to review the current individual as well as BTM cut-off value, which was extrapolated from dilution experiments (Fiedor et al., 2009). Over a one-year period individual and BTM samples were collected monthly on 15 dairy farms. Following a critical review of previous cut-off values, individual and BTM samples were subjected to different cut-off thresholds. Following Receiver-Operating-Characteristics (ROC) analysis, individual milk samples were assessed with the cut-off value 0.573, previously shown to be associated with each 100% sensitivity and specificity. In addition, the present study enabled BTM cut-off adjustment based on field data. To ensure reliable detection of herds with an in-herd prevalence of ≥20% the BTM cut-off was lowered from 0.493 to 0.410, corresponding to 100% sensitivity and 97.32% specificity. Regression analysis showed that the percentage of seropositive animals related to the corresponding BTM ODR correlated moderately (r=0.581, P<0.001), whereas a strong correlation (r=0.764, P<0.001) was found between mean individual and BTM ODR per herd and sampling month. Seasonal antibody pattern became obvious in a single-peaked antibody curve in late summer/early autumn for individual milk whilst BTM showed a two-peaked distribution with an additional spring peak besides the late summer/early autumn peak. This leads to the conclusion that the BTM-ELISA could be a useful tool to detect and control pasture contamination in the spring, following sexual maturation of hypobiotic lungworm larvae harboured by clinically asymptomatic carrier animals. In addition to the knowledge gained on antibody patterns in dairy herds and the relationship of individual and BTM, the present study enabled sensitivity and specificity calculations for the obsolete BTM cut-off value 0.493 to be performed.     

Lungworms (Dictyocaulus arnfieldi): prevalence in live equids in Kentucky

Prevalence of natural infections of the lungworm, Dictyocaulus arnfieldi, was investigated in Kentucky in 5,437 live equids (horses, ponies, and asses) on 91 farms by examination of fecal samples over a 15-month-period from January 28, 1983 to April 19, 1984. For the 91 farms investigated, asses only were examined on 1 farm; for the other 90 farms, examinations were made of horses on all of them, of ponies on 4 farms, and of asses on 9 farms. Larvae of D arnfieldi were found in fecal samples of 112 (2%) of 5,379 horses on the 90 farms of which 38% had greater than or equal to 1 infected animal; none of 19 ponies examined was infected. For 39 asses (donkeys and mules) examined, 21 (54%) were infected; infected asses were present on 80% of the 10 farms on which they were examined. The equids, excluding asses, that were examined and the percentage (in parentheses) infected with D arnfieldi included 4,329 (2%) Thoroughbreds, 684 (2%) Standardbreds, 78 (0%) American Saddle Horses, and 307 (3%) miscellaneous (other breeds or mixed breeds of horses and ponies). Equids were separated into 3 categories relative to previous treatment with ivermectin: A (no treatment), B (treatment), and C (treatment unknown).(ABSTRACT TRUNCATED AT 250 WORDS)