Effect of different times of administration of the nematophagous fungus Duddingtonia flagrans on the transmission of ovine parasitic nematodes on pasture--a plot study

Investigations were made into the timing of administration of Duddingtonia flagrans as a biological control agent against ovine parasitic nematodes including stongylid and Nematodirus spp. Faeces from 3-4 months old male lambs were deposited onto pasture plots that had never been grazed by sheep. The trial was conducted over two consecutive years (1998 and 1999). For both years, the following three plot types were involved: Sim plots had faeces containing nematode eggs and Duddingtonia flagrans spores deposited simultaneously; Post plots had faeces containing nematode eggs followed 2 weeks later by faeces containing D. flagrans spores alone; Control plots had faeces containing only nematode eggs; Prior plots (included in 1999) had faeces containing D. flagrans spores alone followed 2 weeks later by faeces containing nematode eggs. In each year, two deposition periods were involved: July and August in 1998 and June and July in 1999. During the first year pasture samples were collected at 2, 4, 6, 8 and 12 weeks after initial deposition. In 1999, additional samples were collected at 10, 16 and 20 weeks. Larvae were extracted from the pasture samples and counts performed to estimate the number and species of infective third-stage (L(3), larvae) present. The number of third-stage strongylid larvae on pasture was significantly lower on Sim plots compared to the remaining plot types for both years at all deposition times (P<0.001). This was also the case for the number of Nematodirus infective larvae in August deposition plots in 1998 (P<0. 02). There was no significant difference between treatments in both deposition times in 1999 and July deposition plots in 1998 for the Nematodirus data. These results suggest that D. flagrans, if deposited at the same time as parasite eggs prevents transmission of third-stage larvae from the faecal deposit onto pasture, including occasionally Nematodirus species, but does not have an effect on third-stage parasitic nematode larvae in the surrounding soil.     

A new approach in the prevention of gastrointestinal parasitic infections in cattle

The efficacy of a morantel long-acting device in preventing parasitic gastroenteric infections throughout a whole year was evaluated in heifers and steer calves in south central Québec. Thirty-two calves, comprising nine Hereford steers, one Hereford heifer, fourteen Holstein crossbred steers and eight Holstein crossbred heifers, were allotted into two treatment groups and maintained throughout the grazing season on adjacent pastures resulting from equivalently dividing one original pasture. One morantel long-acting device was administered to each animal in one group at the time of turnout onto the pasture in the spring while the calves in the other group remained as nonmedicated controls. The parasitic infections incurred during the pasture season were primarily Ostertagia, Trichostrongylus, Cooperia and Nematodirus.

The following fall, after twelve calves were necropsied for worm counts, the twenty remaining ones were brought into the barn where they were kept throughout the winter with access to an outside yard. They received good quality hay and rolled barley (1 kg/head/day) up until the following May, at which time they were weighed and had fecal samples taken for egg counts. In contrast to the results observed among controls, the morantel long-acting device treatment group had an 87% reduction in fecal worm egg excretion and a 67.3 kg per calf increased weight gain after one year.

     

Relative importance of winter survival of larval nematodes in pasture and infected carrier calves in a study of parasitic gastroenteritis in calves.

A study was done in Maine to determine the relative importance of winter survival of nematode larvae in pasture and infected carrier animals as sources of infection for susceptible calves. Under the conditions of the experiment, it appeared that winter survivals in pasture of the infective stages of the genera Ostertagia, Cooperia, Nematodirus, and Trichostrongylus were of greater importance than carrier animals as sources of infection for susceptible calves. While animals in plots infected the previous summer and simultaneously allowed to graze alongside infected carrier animals did show more worms than those grazed only in infected plots, these differences were not statistically significant. Both groups had significantly (P greater than 0.01) more worms than did calves grazed only with carrier animals for the period of the experiment (8 weeks). It was also observed that carrier calves with low fecal egg counts (less than 200 eggs/g of feces) introduced in early spring to uncontaminated pasture could produce enough parasitic contamination by early fall to cause fulminating infections in susceptible calves grazing the pasture at the same time. Infected animals that survived clinical disease during their 1st summer developed a strong immunity which limited their acquisition of further infections when they were exposed to severe pasture contamination the following year.     

Nematodirus infection in lambs on an alternate grazing system of husbandry

The epidemiology of Nematodirus battus infection under a husbandry system based on an annual alternation of sheep and cattle was studied from 1983 to 1985. Pasture larval levels and sheep and cattle worm egg outputs were monitored from April to September each year. The level of N battus contamination on the sheep pasture and the number of clinically affected lambs increased over the three years despite grazing with cattle in the intervening year. Examination of cattle faeces demonstrated that six-month-old calves excreted moderate numbers of N battus eggs in June and July, thus contaminating next season's sheep grazing.     

Detection of antibodies to Hypoderma lineatum in cattle by Western blotting with recombinant hypodermin C antigen

A study was conducted to evaluate the therapeutic efficacy of doramectin administered intramuscularly at a dose rate of 200 microg/kg to sheep harbouring naturally acquired infections of gastrointestinal nematodes and Oestrus ovis in the southwestern region of France. On day 0, 24 sheep were selected on the basis of positive faecal egg counts (>100 EPG) and positive assessment of O. ovis infection (including positive O. ovis antibody level and positive clinical score). The sheep were randomly allocated to a non-medicated control group (T1) or a doramectin-treated group (T2) of 12 animals each. On day 0, sheep in group T2 received a single intramuscular injection of doramectin (200 microg/kg), whereas those in group T1 received an intramuscular injection of saline solution (sodium chloride, 0.02ml/kg). Individual faecal egg counts were performed on days 0, 1, 2, 3, 4, 5, 6, 7, and 14. Between days 14 and 16, all sheep were slaughtered, and worm and O. ovis burdens were determined. In doramectin-treated sheep, faecal egg counts had decreased to zero by day 4 for all recovered types of nematode eggs: strongyles, Nematodirus sp., Trichuris sp., and Rhabditidae sp. For strongyles, Nematodirus sp., and Rhabditidae, the percentage reductions in faecal egg counts (geometric means) of doramectin-treated sheep, compared to the non-medicated control sheep were 100% from days 4-7. For Trichuris sp., they were 100, 99.7, 99.9, and 100% on days 4, 5, 6, and 7, respectively. On day 14, percentage reductions were 100% for Nematodirus sp. and Rhabditidae, and 99.8 and 99.1% for strongyles and Trichuris sp., respectively. At necropsy, only adult nematodes and mainly first-stage O. ovis larvae were recovered. Doramectin was highly efficacious against the adult stages of Teladorsagia circumcincta (100%), Nematodirus battus (100%), Nematodirus filicollis (99.9%), Oesophagostomum venulosum (99.8%), and Trichuris sp. (99.3%). It was also 100% efficacious against first-stage larvae of O. ovis. No abnormal clinical signs or adverse reactions in any of the sheep treated with doramectin were observed.     

A report on the prevalence of gastrointestinal parasites in yaks (<Emphasis Type="Italic">Bos poephagus</Emphasis>) in the cold desert area of North Sikkim,India

Faecal samples were collected from 348 yaks(Bos poephagus) in and around Gurudogmer Plateau, a cold desert area in North Sikkim, India. The prevalence of gastrointestinal parasitic infection was recorded at 10.05% in both the organized and traditionally managed farms of yak. The pattern of infection was either single (2.58%) or mixed (7.47%) with a faecal egg count range of 100–200 eggs per gram of faeces in positive animals. Among the helminths, Haemonchus spp. infection was predominant (6.89%) followed by Nematodirus spp. (1.72%), Cooperia spp. (1.43%) and Dicrocoelium spp. (0.29%).     

Equine strongyles II. Occurrence of anthelmintic resistance in Switzerland

The occurrence of anthelmintic resistance in strongyles was investigated in 440 horses on 90 farms in Switzerland. The egg hatch assay suggested that benzimidazole (BZ)-resistance was present in 40 of 82 farms (49%). Faecal egg count reduction after pyrantel-treatment was above 96% in 14 of 15 farms. In the remaining farm the efficacy was only 80%. Ivermectin efficacy was investigated on 5 farms and the efficacy was recorded at 98-100%. Faecal cultures undertaken after treatment revealed almost exclusively larvae of the family Cyathostominae. Data about management practices, pasture hygiene and anthelmintic usage were obtained with a questionnaire. Horses were treated on average 3.5 times per year. In 75% of the farms BZ were a component of the seasonal treatment schedule. Only the use of BZ had a significant correlation with the presence of BZ-resistance (P < 0.01). Recommendations for the control of equine strongyles should include measures that minimize the risk of resistance developing against remaining effective anthelmintics.     

Nematode control practices and anthelmintic resistance in dairy calves in the south west of England.

A postal survey of worming practices on West Country dairy farms was undertaken and farmers were requested to send faecal samples for nematode egg counts. The majority of the farmers who responded had a nematode control policy which was based on a mixture of anthelmintics and pasture rotation. Sixty-five per cent turned out calves on to the same paddock each year and 57 per cent treated their stock with anthelmintics during the second year. Ninety farms submitted samples for analysis but only 16 samples contained sufficient eggs to justify repeat egg counts and only eight of these produced enough eggs for in vitro tests. The small number of positive samples, even into the latter part of the year suggests a heavy use of anthelmintics with relatively clean pasture. One Somerset farm had larvae which developed in high concentrations of ivermectin, and eggs were still being passed after two treatments with ivermectin at the manufacturer's recommended dose seven days apart. Of 100 male nematodes isolated from two of the calves, 88 were Cooperia species and 12 were Nematodirus species. A controlled trial with this isolate in eight Friesian male calves showed a 44 per cent reduction in egg counts at day 7 but no significant reduction in worm burden postmortem. This is the first reported case of ivermectin-resistant Cooperia species in cattle in the United Kingdom.     

Feasibility of genus-specific real-time PCR for the differentiation of larvae from gastrointestinal nematodes of naturally infected sheep

Results of real-time PCR analysis of coproculture third stage larvae (L3) using genus specific TaqMan minor groove binder probes were compared with the results of morphological differentiation of L3 after coprocultured and direct morphological worm differentiation from gastrointestinal samples of eight sheep with naturally acquired nematodes infections. Faecal egg counts prior to postmortem confirmed infections with trichostrongyles with a geometric mean count of 4828 eggs per gram for all sheep. Individual egg counts correlated positively with total worm counts (correlation coefficient 0.794). Five different nematode species and one genus were found in the abomasi and small intestines: Cooperia curticei, Haemonchus contortus, Nematodirus spp., Teladorsagia (Ostertagia) circumcincta, Trichostrongylus axei and Trichostrongylus colubriformis. Coproculture of faecal eggs yielded five of these, Cooperia spp., Haemonchus spp., Ostertagia/Teladorsagia spp. and Trichostrongylus spp. Comparison between morphological L3 and worm differentiation data showed high congruence (94%). The agreement between PCR analysis of L3 after coproculture and direct morphological worm differentiation was 84%. Thus, real-time PCR was found to be suitable as a speedy and reliable diagnostic tool for the assessment of gastrointestinal nematode infections of ruminants in the field.     

Epidemiological study of parasite infection in a cow-calf beef herd in Quebec.

The patterns of gastrointestinal and pulmonary nematode infections in a previously untreated Aberdeen Angus cow-calf herd were observed between May 1988 and December 1990. The cow-calf herd and replacement heifers were on separate pastures. The relatively high mean faecal egg counts of cows and heifers at the time of turnout were mainly owing to the maturation of hypobiotic worms. The strongyle egg counts of calves began to rise soon after turnout onto pasture and reached peak levels at the end of the grazing season. The number of infective larvae on pasture was highest during September/October. Ostertagia, Cooperia and Nematodirus were the most prevalent genera found at necropsy and on pasture. Larvae of these nematodes were able to overwinter on pasture and Ostertagia larvae, additionally, were able to overwinter in the host as arrested early fourth stage larvae. The high egg output of cows at the time of turnout may serve as a source of infection for their calves and be responsible for the late-season rise in pasture larval counts.     

Prevalence and geographical distribution of Giardia spp. and Cryptosporidium spp. in dairy farms in Québec.

Giardiasis and cryptosporidiosis are parasitic infections of humans, domestic animals, and wildlife. In cattle, direct transmission through the contamination of barns and/or pasture appears to be the principal mode of infection. In Canada there is only one study reported in the literature on the prevalence of giardiasis and one study on the prevalence of cryptosporidiosis. These studies were done in Alberta and Manitoba, respectively. The purpose of this study was to determine the prevalence of Giardia spp. and Cryptosporidium spp. infections in dairy farms in Québec. Calves were sampled from 505 dairy farms. We are reporting that 45.7% of the farms were found to be positive for Giardia spp. and 88.7% were infected with Cryptosporidium spp.     

Fecundity of gastrointestinal trichostrongylid nematodes of sheep in the field

Twenty-two Dorset Rambouillet lambs were moved to contaminated pasture on Apr 1, 1987. At regular intervals thereafter, pairs of lambs were withdrawn and euthanatized. Gastrointestinal parasites in the abomasum, small intestine, cecum, and large intestine were removed and counted. The last pair of lambs was euthanatized 8 months after original placement on the contaminated pasture. Fecal samples were taken at 3- to 4-week intervals throughout the grazing season and the fecal egg counts were used to estimate parasite fecundity (output of eggs per female parasite per day). The principal parasite genera found included Haemonchus spp, Trichostrongylus spp, and Nematodirus spp. In each of the genera examined, parasite fecundity remained the same irrespective of the intensity or duration of infection. Estimated average fecundities (eggs/female/day) were as follows: Haemonchus contortus, 6,582; Trichostrongylus spp, 262; Nematodirus spp, 40; and Oesophagostomum venulosum, 11,098.     

Cow-calf herds in eastern Germany: status quo of some parasite species and a comparison of chemoprophylaxis and pasture management in the control of gastrointestinal nematodes.

Infections with gastrointestinal parasites (Eimeria spp., Cryptosporidium spp., Buxtonella sulcata, Fasciola hepatica, Moniezia spp. and trichostrongyles) and lungworms were monitored in five cow-calf herds in the north German lowlands. Estimated prevalences of infections with Eimeria spp. (predominantly Eimeria bovis) ranged between approximately 2 and 48%. The highest prevalences were found during late summer and autumn. On one farm Cryptosporidium spp. were detected in July and August (prevalence: 8.5 +/- 2.7% and 6.7 < 2.0%). The latter finding coincided with diarrhoea in many calves. Buxtonella sulcata was found during the entire study period in highly variable estimated prevalences ranging between zero and 73%, but without any obvious association with clinical disease. Fasciola hepatica was detected on four out of five farms at estimated prevalences of approximately 1-20%. Lungworm infections played a minor role in at least three of five study herds. The estimated prevalence of trichostrongyle infections rose from August until November whereas the intensity of infection did not change significantly. No difference in the intensity of infection could be detected between one farm on which infections with gastrointestinal nematodes were controlled only by moving the animals to an uninfected pasture in July, and three other herds on which strategic anthelmintic control was in place.     

Epidemiology of trichostrongylidosis in cattle: development of infective larvae in the second part of the grazing period and their contribution to infections in the same year.

A grazing experiment was performed in the Swiss midland region with 22 first-season calves which were grazed together from May to mid July when they were allocated to two equal groups, one receiving a morantel sustained-release trilaminate bolus (Paratect Flex) bolus, Pfizer, Zurich, Switzerland) and the other one remaining as an untreated control. Each group was moved to a clean pasture on 21 July. The larval contamination on the pasture with the control animals reached 4652 third stage larvae (L3) per kilogram of dry matter (L3 kg-1 DM) after 10 weeks. Parasitic gastroenteritis was observed in two calves of the control group in August, and mean serum pepsinogen levels exceeded 4000 mU tyrosine in this group in September. Eggs from Ostertagia sp. and Cooperia sp. that were excreted by the animals at the beginning of July and the end of August showed similar hatching rates of 94% and 99%, respectively. In the calves of the bolus group the egg output was reduced by 95% within 14 days of administration of the bolus. Larval contamination on the pasture of the bolus group was zero until the beginning of September when a slight increase occurred, reaching 793 L3 kg-1 DM in October. At the end of the trial the bolus-treated calves had a mean weight gain advantage of 18 kg (P < 0.05) compared with the controls. The results confirm that a second generation of larvae developed on pasture in August and September and caused parasitic gastroenteritis in first-year grazing calves in late summer. The relevance of the results for the prophylaxis of parasitic gastroenteritis in calves in mixed grazing systems with calves and older cattle is discussed.     

The possibilities and limitations of evasive grazing as a control measure for parasitic gastroenteritis in small ruminants in temperate climates

Between 1999 and 2003 studies were done at Utrecht University on the population dynamics of gastrointestinal nematodes and the potential to use evasive grazing for the control of nematode infections in small ruminants. On most pastures grazed in May and June it took at least 3 weeks before high pasture infectivity levels for Haemonchus contortus developed while it took at least 2 weeks on pastures grazed in July, August and September. Occasionally, larvae emerged earlier on pasture when high temperatures coincided with rain. Pasture infectivity levels for H. contortus subsequently increased and the highest levels were found between 5 and 9 weeks on pastures grazed in May-June and between 3 and 9 weeks on pastures grazed in July, August and September. Pasture infectivity usually had decreased again to low levels after approximately 3 months. Larvae of the other trichostrongylids emerged later on pasture. However, patterns of Teladorsagia circumcincta, Trichostrongylus spp. and Cooperia curticei were basically similar to H. contortus. Strongyloides papillosus larvae emerge within 2 weeks on pasture and survival is short. On the other hand Nematodirus larvae took a lot longer to emerge on pasture than the other trichostrongylids. The results imply that only on a small proportion of farms (mixed dairy cattle/sheep farms; some organic dairy goat farms) evasive grazing can be recommended as only control measure for parasitic gastroenteritis. However, the present data offer possibilities to combine evasive grazing with other methods in an integrated control scheme.     

Risk factors for high endoparasitic burden and the efficiency of a single anthelmintic treatment of Danish horses

A questionnaire survey regarding endoparasite control practices in Danish horse herds was carried out in 1995. The participating veterinarians and herd owners were sampled using convenience and purposive sampling. In the analysis of risk factors for development of a high endoparasitic burden (> 200 eggs per gram faeces) 903 horses were sampled and the analysis of the efficiency of a single anthelmintic treatment was based on 605 horses. The following factors had a significant effect on the endoparasitic burden: herd type, age of the horses, use of pasture rotation, anthelmintic treatment of horses visiting the herd, use of an adviser in the planning of endoparasite control and advice regarding pasture rotation. An interaction between pasture rotation and advice regarding pasture rotation was found, but due to high colinearity this was not reported. The factors influencing significantly on the reduction of the faecal egg count after a single anthelmintic treatment were the type of herd, the age of the horse, the drug used, and the anthelmintic-resistance-status of the herd. A negative effect of permanent pastures was observed. If pasture hygiene was performed on the advice of the veterinarian, the effect of a single anthelmintic treatment was less compared to a single anthelmintic treatment without any advice. An interaction between the treatment group and the resistance-status of the herd was found. Additional factors, normally accounted for, when endoparasites and anthelmintic resistance is discussed, were investigated, but not found significant in this study.     

An assessment of residual ovine nematodes on pasture under maritime conditions.

Residual ovine nematode pasture infections were assessed by grazing groups of ewes and their lambs on permanent sheep and cattle pastures and by the use of tracer lambs. Ostertagia spp., Cooperia oncophora, Nematodirus spp., Chabertia ovina and Trichuris spp. eggs and/or larvae survived on pastures overwinter. Second generation Ostertagia larvae were present in greatest numbers on pasture during the latter part of August and early September. The failure of a significant build-up of Cooperia oncophora was attributed to negligible worm egg output of this species in sheep. A build-up of Nematodirus spp. on pasture was not detected in this study.     

Effect of vitamin E supplementation on naturally acquired parasitic infection in lambs

Gastrointestinal nematode infections cause substantial economic losses in pasture-based sheep farming worldwide. Host nutritional status has been identified as a key component of immune function. While vitamin E supplementation is known to have broad-spectrum effects on immune function in livestock, to our knowledge, there are no reports on the effect of vitamin E supplementation on trichostrongylid parasite infections in lambs. This study evaluated the effect of parenteral vitamin E supplementation on naturally acquired parasite infection in lambs. Twenty-seven spring lambs were sequentially assigned to receive injections of vitamin E (15 or 30 IU D-α-tocopherol/kg body weight (BW) or placebo, every two weeks, from birth to 28 weeks of age. Blood was collected at weeks 0, 2, 4, 8, 12, 16, 20, 24, and 28 to determine serum α-tocopherol concentration. Once the youngest animal reached 15 weeks of age all lambs were dewormed and grazed together on a pasture known to be contaminated with trichostrongylid larvae. Fecal egg count and blood packed cell volume (%) were determined on each lamb immediately prior to deworming and for the first seven weeks of pasture infection. Lambs were euthanized when they reached 28 weeks of age for determination of parasite worm burdens. Vitamin E supplementation at 30 IU/kg BW increased serum α-tocopherol over that of placebo (P<0.001) however, there was no effect of vitamin E supplementation on liver (P=0.804) or muscle (P=0.16) α-tocopherol content. There was no effect of vitamin E supplementation on fecal egg counts, packed cell volume, worm burden or nematode species distribution. Nematode genera identified were Haemonchus (30%), Trichostrongylus (42%), Nematodirus (27%), Strongyloides sp. (<1%), and Aonchotheca sp. (<1%). These results indicate that biweekly injections of vitamin E at 15 and 30 IU d-α-tocopherol/kg BW, had no effect on parasitological parameters used in the study to assess gastrointestinal nematode infection.     

Cysteine proteinases Fas1 and Fas2 are diagnostic markers for Fasciola hepatica infection in alpacas (Lama pacos)

Circulating antibody against Fasciola hepatica antigens was determined by enzyme-linked immunosorbent assay (ELISA) and immunoelectrophoresis in alpacas naturally exposed to F. hepatica. Serological assay parameters were established by using sera from eight infected animals and seven controls with no record of this parasitic infection. Excretory--secretory (ES-) products, Fas1- and Fas2-ELISA were used to survey 307 alpacas from a F. hepatica endemic area in the Peruvian Andes. Seroprevalence of F. hepatica infection varied from 56.7, 64.8 and 66.8% measured by Fas1-, Fas2- and ES-ELISA, respectively. The sensitivity for ES-ELISA was 95%, corresponding Fas1- and Fas2-ELISA sensitivity values were 90 and 95%. In this population, 7% of animals were positive for F. hepatica eggs in faeces, other parasites detected were Trichuris sp. (40%), Nematodirus sp. (34.6%), Lamanema sp. (12.8%) and Eimeria sp. (11.8%). The results show that F. hepatica infected animals elicit circulating antibodies against ES, Fas1 and Fas2. Fas2-ELISA may be proposed as a sensitive assay for the immunodiagnosis of fasciolosis in alpacas.     

Epidemiology of subclinical dairy cow nematode infections on five farms in England in 2002 and a comparison with results from 1978 to 1979

A detailed study of the epidemiology of subclinical nematode infections in adult dairy cows was conducted on five well-managed English dairy farms during the 2002 grazing season. These same farms had also participated in a similar study in 1978-1979 and thus provided a unique opportunity to compare the epidemiological findings after an interval of over two decades. Common factors, including the prevalence of infection, faecal worm egg output, pasture larval count and nematode genera present, and estimated daily larval intake at pasture, were compared between the two studies. Subclinical roundworm burdens, as judged by faecal egg counts, were widespread in dairy cows in 2002, but the prevalence of animals with patent infections and the magnitude of the worm egg output were significantly lower than in 1978-1979. Both the prevalence of infection and mean faecal worm egg output exhibited a marked seasonal peak during the summer months in 2002. Pasture larval numbers were, however, nearly three times higher in 2002 with Ostertagia dominating the nematode genera to which cows were exposed at pasture in both surveys. Factors considered likely to account for differences in parasite epidemiology include the marked increase in herd productivity over the intervening period, the increased proportion of Holstein genetics with the consequent increase in milk yield and feed intake, changes in grassland management and increased stocking rate seen on the majority of farms.