Giardia duodenalis stimulates partial maturation of bovine dendritic cells associated with altered cytokine secretion and induction of T-cell proliferation.

Giardia duodenalis is an important intestinal parasite in animals and humans. The role of dendritic cells (DC) in the initiation of the immune response against G. duodenalis is poorly documented. The aim of this study was to test the hypothesis that G. duodenalis interferes with bovine DC function. Therefore, the effect of trophozoites and excretion/secretion products on bovine monocyte-derived dendritic cells (MoDC) was investigated. We assessed MoDC maturation and cytokine production of G. duodenalis-stimulated MoDC and the ability of these MoDC to take up antigen and induce lymphocyte proliferation. Little or no upregulation of maturation markers CD40 and CD80 was measured, but MHCII expression was increased after stimulation with low parasite concentrations. A dose-dependent decrease in ovalbumin uptake was observed in G. duodenalis-stimulated MoDC. In addition, stimulated MoDC induced proliferation of CD3(-) , γδ-T-cells and TCRαß(+) CD4(+) and CD8(+) T-cells. Increased transcription of TGF-ß was shown in CD4(+) T cells, and increased TNF-α, TGF-ß, IL-10 and IL-4 were seen in γδ-T-cells. We found no evidence that G. duodenalis has a regulatory or inhibitory effect on bovine MoDC. MoDC stimulated with G. duodenalis are functionally active and able to induce proliferation of T cells that produce both pro- and anti-inflammatory cytokines.

Multilocus genotyping of Cryptosporidium and Giardia in non-outbreak related cases of diarrhoea in human patients in Belgium.

Stool samples from Belgian patients suffering from abdominal pain and/or diarrhoea were examined for Cryptosporidium and Giardia. Cryptosporidium-positive samples were genotyped using the 70 kDa heat shock protein and the 60 kDa glycoprotein (GP60) genes: C. hominis was identified in 54.2% and C. parvum in 45.8% of the samples. Sequencing at the GP60 locus indicated that subgenotype IbA10G2 of C. hominis and subgenotype IIaA15G2R1 of C. parvum were the most prevalent, although several other subgenotypes were identified. For Giardia, sequencing at the beta-giardin, triose phosphate isomerase (TPI) and glutamate dehydrogenase (GDH) genes revealed assemblage B as the most prevalent (74.4%) in human patients. A high degree of heterogeneity was found, especially on the beta-giardin gene, and to a lesser extent on the GDH gene. Furthermore, using a novel species-specific PCR based on the TPI gene, mixed infections with both assemblage A and B were detected in a large number (32.4%) of human patients, which might have important epidemiological implications.

Giardia and other intestinal parasites in different dog populations in Northern Belgium.

The objectives of this study were to obtain data on the prevalence of intestinal parasites in different dog populations in northern Belgium, to estimate the zoonotic risk associated with these infections and to identify potential risk factors. Between 2004 and 2007 a total of 1159 faecal samples were collected from 451 household dogs, 357 dogs from breeding kennels and 351 dogs with gastrointestinal disorders. The samples from dogs with gastrointestinal disorders were sent to the diagnostic Laboratory for Parasitology at Ghent University by veterinary practitioners. In household dogs the prevalence of intestinal parasites was relatively low. Giardia was the most commonly found parasite (9.3%, CI 5.5-13.1), followed by Toxocara canis (4.4%, CI 2.7-6.8). Much higher infection rates were observed in kennel dogs, especially for Giardia spp. (43.9%, CI 37.8-50.0); T. canis (26.3%, CI 21.8-31.2) and Cystoisospora spp. (26.3%, CI 21.8-31.2). Also in dogs with gastrointestinal problems, Giardia spp. (18.1%, CI 13.1-23.1), Cystoisospora spp. (8.8%, CI 6.1-12.3) and T. canis (7.4%, CI 4.9-10.7) were the most frequently detected parasites. In all dog populations pups were more frequently infected with Cystoisospora (P<0.0001 to P<0.05), Giardia (P<0.001 to P<0.05), and T. canis (P<0.0001 to P<0.001) than adult dogs, except for T. canis in household dogs, where this correlation was not significant. A significant association of anthelmintic treatment with T. canis infections was only observed within the household population. Household dogs with a higher number of treatments per year were more frequently infected with T. canis (P<0.05). There was a significant difference between the different breeding kennels for the occurrence of Cystoisospora, Giardia and T. canis (P<0.0001) and large kennels harboured relatively more infected animals than smaller breeding facilities (P<0.05). However, this was not significant for Giardia spp. Breed and gender did not affect the risk of an infection in any of the study populations. Toxocara and Giardia present a zoonotic risk, especially in household dogs, where the majority of Giardia positive samples (80%) belonged to the zoonotic assemblage A. In kennel dogs and clinically affected dogs the host-specific Giardia assemblages C and D were most prevalent (94% and 80%, respectively).

Mixed Giardia duodenalis assemblage A and E infections in calves.

A molecular epidemiological study was conducted on 100 dairy (499 calves) and 50 beef (333 calves) farms in Belgium to estimate the prevalence of different Giardia duodenalis assemblages in calves younger than 10 weeks of age. Positive samples from the epidemiological study and from a previous clinical study were selected and genotyped based on the amplification of the beta-giardin gene. To investigate the occurence of mixed assemblage A and E infections in calves, a novel assemblage-specific PCR was developed based on the triose-phosphate isomerase gene. The prevalence was 22% (95% Probability Interval (PI): 12-34%) in dairy calves and 45% (95% PI: 30-64%) in beef calves. In total, 120 Giardia-positive samples from dairy and beef calves collected in the epidemiological study and from clinically affected calves were identified based on the amplification of the beta-giardin gene. Overall G. duodenalis assemblage E was more prevalent (in 64% of the samples), although the majority (59%) of the dairy calves were infected with G. duodenalis assemblage A. Furthermore, mixed G. duodenalis assemblage A and E infections were identified in 31% of the calf samples (n=101) using the assemblage-specific PCR. We believe this is the first report of mixed infections in calves, and the results of the present study indicate that calves, although mainly infected with the host-specific G. duodenalis assemblage E, are frequently infected with the zoonotic assemblage A, either as a mixed or mono-infection, suggesting that calves might be underestimated as a potential zoonotic reservoir for human infections.

A Bayesian evaluation of three diagnostic assays for the detection of Giardia duodenalis in symptomatic and asymptomatic dogs.

A Bayesian approach was used to evaluate three commonly used diagnostic assays for the detection of Giardia duodenalis in dogs: microscopical examination (ME), a commercial immunofluorescence assay (IFA: MerifluorGiardia test) and a commercial immunochromatographic assay (SNAP: Idexx SNAPGiardia test). These assays were evaluated for use in two different settings: in a cross-sectional epidemiological survey in household dogs and in a clinical survey, both conducted in the northern part of Belgium. A total of 272 faecal samples from household dogs and 141 faecal samples from clinically affected dogs were examined using these three diagnostic assays. The Bayesian analysis indicated that all tests were highly specific (specificity above 90%), and that the IFA is more sensitive than SNAP and ME, both in an epidemiological and in a clinical setting. For all three tests, the estimated sensitivity values were higher in the clinical compared to the epidemiological survey, whereas the specificity values were comparable in both studies. The results of the present study indicate that IFA is a highly specific and sensitive technique for the detection of G. duodenalis cysts, both for use in an epidemiological or clinical survey. The SNAP is a specific and fairly sensitive technique for the diagnosis of Giardia in clinically affected dogs. Overall, the ME was found to be a specific diagnostic technique, although lacking sensitivity.

Parasitic infections in dairy cattle around Hanoi, northern Vietnam.

In northern Vietnam, dairy cattle are mainly managed in small-scale farms, where animals are kept confined and feeding occurs by cut and carry methods. In the present study the occurrence of parasitic infections was examined in five provinces around Hanoi. A total of 201 farms were visited, and 334 stool and 239 blood samples were collected from calves younger than 3 months, animals between 3 and 24 months and adult cows. Furthermore, 254 milk samples were collected from lactating animals. Coproscopical examination indicated a high prevalence of nematode eggs (Cooperia spp., Haemonchus and Oesophagostomum spp.) in animals (n=176) between 3 and 24 months (66%) and in adult cows (n=90; 54%). In these age groups the prevalence of Fasciola was 28% and 39%, respectively, and for Paramphistomum the prevalence was 78% and 82%, respectively. Fifty percent of the calves younger than 3 months (n=68) were positive for Giardia, and none for Cryptosporidium. Most Giardia isolates were identified as the non-zoonotic G. duodenalis assemblage E on the beta-giardin gene. The blood samples were examined with commercially available Svanovir((R))Elisa's for the presence of Anaplasma marginale and Babesia bigemina specific antibodies, and a prevalence of 28% and 54% was found, respectively. In the milk samples Neospora caninum specific antibodies (Svanovir((R))Elisa) were detected in 30% of the lactating animals. The present study demonstrates that parasitic infections occur frequently in dairy cattle around Hanoi although animals are mainly kept confined, and indicates that further research on the economic impact of these infections is needed.

Mind the gaps in research on the control of gastrointestinal nematodes of farmed ruminants and pigs.

Gastrointestinal (GI) nematode control has an important role to play in increasing livestock production from a limited natural resource base and to improve animal health and welfare. In this synthetic review, we identify key research priorities for GI nematode control in farmed ruminants and pigs, to support the development of roadmaps and strategic research agendas by governments, industry and policymakers. These priorities were derived from the DISCONTOOLS gap analysis for nematodes and follow-up discussions within the recently formed Livestock Helminth Research Alliance (LiHRA). In the face of ongoing spread of anthelmintic resistance (AR), we are increasingly faced with a failure of existing control methods against GI nematodes. Effective vaccines against GI nematodes are generally not available, and anthelmintic treatment will therefore remain a cornerstone for their effective control. At the same time, consumers and producers are increasingly concerned with environmental issues associated with chemical parasite control. To address current challenges in GI nematode control, it is crucial to deepen our insights into diverse aspects of epidemiology, AR, host immune mechanisms and the socio-psychological aspects of nematode control. This will enhance the development, and subsequent uptake, of the new diagnostics, vaccines, pharma-/nutraceuticals, control methods and decision support tools required to respond to the spread of AR and the shifting epidemiology of GI nematodes in response to climatic, land-use and farm husbandry changes. More emphasis needs to be placed on the upfront evaluation of the economic value of these innovations as well as the socio-psychological aspects to prioritize research and facilitate uptake of innovations in practice. Finally, targeted regulatory guidance is needed to create an innovation-supportive environment for industries and to accelerate the access to market of new control tools.

The efficacy of an oral treatment with paromomycin against an experimental infection with Giardia in calves.

A controlled and blinded study was conducted to evaluate the efficacy and safety of a treatment with paromomycin sulphate against an experimental Giardia infection in calves. Animals were infected with 10(5)Giardia cysts of cattle origin and were either treated 11 days later with 25, 50 or 75 mg paromomycin/(kg body weight per day) during 5 consecutive days or not treated (control group). Efficacy was evaluated based on reduction in cyst excretion. Furthermore weight gain and diarrhea scores were monitored. In the group treated with 75 mg/kg per day there was a 100% reduction in cyst excretion until 9 days after the start of the treatment (D9) and a very high reduction (> or =98%) until D13. There was a high reduction (> or =93%) until D9 and D13 in the groups treated with 25 and 50 mg/kg, respectively. The cumulative cyst excretion on D13 was significantly (P<0.05) lower in the groups treated with 75 and 50 mg/kg compared to the control group. Although there was a trend towards higher weight gain and less diarrhea in the treated groups, differences between groups were not significant. No adverse reactions to the paromomycin treatment were recorded. Furthermore, the need for reliable parameters for evaluation of treatments against protozoal infections is emphasised.

Prevalence and genotyping of Cryptosporidium in three cattle husbandry systems in Zambia.

To estimate the prevalence of Cryptosporidium spp. in three different husbandry systems in Zambia, faecal samples were collected from calves up to the age of 3 months. Faecal consistency was scored for correlation with infection. Additionally, 45 positive samples were selected for genotyping by amplification of the 70-kDa heat shock protein (HSP-70) and the 18S rRNA gene. A total of 37 dairy, 25 beef and 92 traditional husbandry farms were visited: 250 samples were collected on dairy farms, 238 on beef farms and 256 on traditional husbandry farms. All samples were analysed using a commercial copro-antigen ELISA (Techlab)(Cryptospridium test). The calf prevalence in dairy, beef and traditional husbandry systems was 42.8%, 8.0% and 6.3%, respectively. Furthermore, 75.7% of the dairy farms, 44.0% of the beef farms and 15.2% of the traditional husbandry farms had at least one positive calf at the time of visit. Subsequently, there was a significantly higher Cryptosporidium parvum prevalence on dairy farms compared to beef or traditional farms (chi(2), P<0.001). On dairy farms low faecal consistency was correlated with C. parvum infection (chi(2), P<0.05). Both C. parvum and C. bovis were identified, although in one beef calf C. suis was found.

Development and Bayesian evaluation of an ELISA to detect specific antibodies to Sarcoptes scabiei var suis in the meat juice of pigs.

Samples of ear scrapings, serum and diaphragmatic muscle were collected from 271 fattening pigs at the slaughterhouse. The scrapings were examined for the presence of mites, and tests for specific antibodies to Sarcoptes scabiei var suis in the serum and meat juice were made with an experimental ELISA. The cut-off value for the meat-juice ELISA was estimated at an optical density of 0.5 by receiver operating characteristic curve analysis, on the basis of the cut-off value for the serum ELISA of 0.4. The results of the three tests were used in a Bayesian model to estimate the characteristics of each test. The specificity of the tests of the ear scrapings was considered to be 1 and their sensitivity was estimated by Bayesian analysis to be 0.86, with a 95 per cent confidence interval (CI) of 0.73 to 0.99. The sensitivity of the meat juice ELISA (0.71, 95 per cent CI 0.6 to 0.8) and its specificity (0.77, 95 per cent CI 0.66 to 0.89) were comparable with the sensitivity (0.73, 95 per cent CI 0.6 to 0.8) and specificity (0.81, 95 per cent CI 0.69 to 0.95) of the serum ELISA.

Semi-quantitative differentiation of cyathostomin larval cultures by reverse line blot.

Cyathostomins are the most prevalent horse nematodes worldwide and over 50 species are described. The eggs and the infective larvae (L3) can easily be obtained or cultured from infected horses, but cannot be differentiated morphologically at species level. A reverse line blot (RLB) method based on the hybridization of a PCR fragment with a species specific probe, has previously been developed for the differentiation of individual eggs and/or L3s, but is too labor intensive for large scale studies. In the present study a RLB method on multiple pooled L3s for the semi-quantitative differentiation of cyathostomin larval cultures was developed and validated. First, the probability of the presence of a certain species within a pool was calculated as function of the frequency and the number of L3s within a pool. Ten L3s per pool were found to be optimal. Next, the probability, the chance of occurrence was calculated when 4 pools per culture were used. The probability distributions for 0, 1, 2, 3 or 4 positive pools were transformed into the corresponding median frequency of the cumulative probability: 0.014, 0.04, 0.08, 0.16 and 0.59, respectively. Based on these calculated probabilities, RLB on 10 L3s per pool and 4 pools per sample was validated by estimating the cross-hybridization, precision and accuracy in 3 groups of horses. First, absence of cross-hybridization was confirmed by differentiation of the same L3s (160 L3s from the 4 horses from group 1) in the RLB on individual as well as on pooled L3s. Cross-hybridization was excluded for 9 of the most common cyathostomins. Next, the precision and accuracy were determined by the differentiation of 10 replicates of 3 cultures from 3 horses from group 2 (1200 L3s). The coefficient of variation (CV) was between 0 and 0.90 and the accuracy was between 0.42 and 1.73. A Monte Carlo simulation based on the observed scores and associated probability distributions gave similar results as the use of a fixed median frequency. The LPGs obtained from 276 larval culture counts from a larger cohort (23 horses, group 3) were not significantly different from the LPGs obtained from summation of the LPG per species found by RLB on pooled L3s. The RLB on pooled L3s was found therefore an useful semi-quantitative method for the differentiation of the most common cyathostomin L3, with a workload of approximately one tenth of that of the RLB on individual L3s.

Species composition of larvae cultured after anthelmintic treatment indicates reduced moxidectin susceptibility of immature Cylicocyclus species in horses.

For the control of cyathostomins in horses, the macrocyclic lactones (MLs), moxidectin (MOX) and ivermectin (IVM) are the most commonly used anthelmintics. However, reduced activity, observed as shortening of the egg reappearance period (ERP) has been described. Shortening of the ERP may be caused by a decreased susceptibility of immature worms for MLs. Alternatively, immature worms may develop faster into egg producing adults as a result of repeated ML treatments. The species composition of the larval cultures obtained shortly after ML and pyrantel (PYR) treatment can confirm the hypothesis of decreased ML susceptibility, as this is often class-specific, whereas faster development would also occur after treatment with anthelmintics with a different mode of action. From 3 farms with a known history of shortened ERP, 8 horses per farm were selected and divided into 2 groups. The MOX-PYR-MOX group was treated twice with MOX (day 0 and 126) and once with PYR (day 84) and the IVM-PYR-IVM group was treated twice with IVM (day 0 and 98) and once with PYR (day 56). Cultured infective larvae (L3s) were counted and differentiated with the reverse line blot on pooled samples. Per cyathostomin species, the number of larvae per gram was calculated. The efficacy of all ML treatments was 100% and a shortened ERP was found on all 3 farms. The species composition of the larval cultures after ML treatment did not differ significantly from that after PYR treatment in the IVM-PYR-IVM group, but it did differ in the MOX-PYR-MOX group. The larval cultures obtained after MOX treatment consisted mostly of Cylicocyclus nassatus, while after PYR treatment Cylicostephanus longibursatus was the most abundant species. In the cultures from 42days after MOX treatment 6 cyathostomin species from 3 genera were found on the farm with the lowest activity (farm 1), while on the farm with the highest activity (farm 3) only 3 species from one genus were found in the same number of examined L3s. The high numbers of L3s of Cylicocyclus species 42days after MOX treatment and the low numbers 42days after PYR treatment can be explained by reduced susceptibility of the immature worms to MOX, but not by a faster development. In conclusion, shortening of the ERP following MOX treatment is most likely a process in which an increasing number of immature worms from an increasing number of species is becoming less susceptible to the active compound.

Protection studies with a globin-enriched protein fraction of Ostertagia ostertagi.

The protective capacity of an adult stage Ostertagia ostertagi globin antigen was tested in four vaccination experiments in cattle. In a preliminary experiment, calves were vaccinated three times intraperitoneally with 250 microg globin in Freund's adjuvant and challenged with a trickled infection of 25,000 infective larvae. In three subsequent field studies, calves were vaccinated twice or three times intramuscularly with 80-100 microg globin in Quil A and challenged with a natural gastrointestinal nematode infection on pasture. Higher globin-specific antibody levels were detected in the vaccinated calves than in the control animals in all vaccine trials. In the preliminary experiment, geometric mean cumulative egg counts in the globin group were reduced by 52% and total worm burdens were reduced by 28%, compared to the controls. In the first field trial cumulative faecal egg counts were reduced by 63% in the vaccinated calves. However, the reduction in faecal egg output in these two experiments was not statistically significant and no reduction in faecal egg counts was observed in the vaccinated animals in the two last field trials. In conclusion, vaccination of calves with O. ostertagi globin resulted in highly variable protection levels after challenge infection.

[Protozoan infection causes diarrhea in calves]. / Protozoaire infecties als oorzaak van diarree bij jonge kalveren.

The role of protozoan parasites in the etiology of diarrhea in calves is highlighted with emphasis on correct diagnosis. In neonatal calves, Cryptosporidium parvum is isolated in more than 44% of the faeces of diarrhetic calves. In calves older than one month, both Eimeria bovis and E. zuernii, and Giardia duodenalis are associated with diarrhea and poor growth. Clinical diagnosis has to be confirmed by examination of host faecal material. Both for C. parvum and G. duodenalis immunological assays are available. Control measures must aim to reduce or prevent oocyst or cyst transmission, by combining management measures, desinfection and chemotherapeutic treatment.

Resistance of gastrointestinal nematodes to the most commonly used anthelmintics in sheep, cattle and horses in Spain.

The objective of this study was to evaluate the status of anthelmintic resistance (AR) in ruminants and horses in Spain. The efficacy of commonly used macrocyclic lactones (MLs) - ivermectin (IVM) and moxidectin (MOX) - was measured in sheep, cattle and horses. In addition, albendazole (ABZ) and levamisole (LEV) were evaluated in sheep and oxibendazole (OXI) and pyrantel (PYR) in horses. Efficacy was evaluated based on the difference between the arithmetic mean pre- and post-treatment faecal egg count (in cattle and horses), or compared to an untreated control group (in sheep). AR was present when the percentage reduction in egg count was <95% and the lower 95% confidence interval (CI) was <90%; if only one of these two criteria was met, the finding was recorded as suspected AR (SAR). In horses, AR-PYR and OXI was considered when the percentage reduction in egg count was ≤ 90% and the lower 95% CI was ≤ 80%. For each animal species, at least 10 study sites were selected. AR to at least one of the drugs was detected in all 10 sheep flocks; the main parasite identified after treatment was Teladorsagia circumcincta. Moreover, in 5 flocks multidrug resistance was identified, on 4 farms to drugs from different families, on one farm to both MOX and IVM and on another farm to all drugs tested. In cattle, the efficacy of both MOX and IVM was 100% on 4 and 3 farms, respectively, and therefore 60% of these farms were considered to have AR or SAR to both MLs. The most frequent parasite identified after treatment was Trichostrongylus spp., although Ostertagia ostertagi was also identified after treatment on one farm. In contrast to ruminants, the 4 drugs evaluated in horses were highly efficacious against strongyles, with efficacies for the MLs and OXI between 95 and 100% and between 94 and 100% for PYR, although 3 herds were SAR against PYR. In conclusion, AR to at least one of the commonly used drugs was identified on all sheep flocks investigated in the northwest of Spain. The occurrence of AR to MLs in cattle was higher than expected but consistent with what was observed in sheep. In horses, all currently used drugs were confirmed as effective against strongyles.

The occurrence and genetic characterization of Cryptosporidium and Giardia species in foals in Belgium, The Netherlands, Germany and Greece.

Faecal samples were collected from foals between the age of 1 week and 6 months in Belgium, The Netherlands, Germany and Greece. A quantitative direct immunofluorescence assay based on the commercial MERIFLUOR Cryptosporidium/Giardia kit was performed to evaluate the presence of (oo) cysts. Parasite positive samples were genotyped, based on the 18S ribosomal DNA gene and the heat shock protein (HSP70) gene for Cryptosporidium and on the ß-giardin gene and the triose phosphate isomerase (TPI) gene for Giardia. In total, 134 foals from Belgium, 44 foals from The Netherlands, 30 foals from Germany and 190 foals from Greece were examined. No Cryptosporidium oocysts were identified in faecal samples from foals in Germany and The Netherlands. In Belgium and Greece, 4.5% and 1.1% of the foals examined were Cryptosporidium positive, respectively, all with a low oocyst excretion ranging from 100 to 2450 oocysts per gram of faeces. For Giardia, 14.2%, 11.4%, 10.0% and 11.6% of the foals in Belgium, The Netherlands, Germany and Greece, respectively, were found to excrete cysts, with a range of 50 up to 4,000,000 cysts per gram of faeces. Younger animals secreted significantly more Giardia cysts than older horses (p<0.05), but no significant correlation between Giardia infection and diarrhoea was observed. Most Giardia positive samples belonged to assemblage AI and/or BIV, but also assemblage E was detected in two samples. Together with the identification of Cryptosporidium horse genotype, this suggests only a low risk for zoonotic transmission.

Estimation of diagnostic test characteristics and prevalence of Giardia duodenalis in dairy calves in Belgium using a Bayesian approach.

A Bayesian approach was used to determine both the test properties of three diagnostic test procedures and the prevalence of Giardia duodenalis in dairy calves in Belgium. A cross-sectional survey was conducted in the province of East Flanders, Belgium. Between September 2001 and December 2003, a total of 100 farms were visited and faecal samples were obtained rectally from 499 calves aged from newborn to 70 days. Because there is no gold standard for the diagnosis of a G. duodenalis infection in dairy calves, a subset of 235 samples obtained on the first 50 farms, was examined using three different assays: microscopical examination, an immunofluorescence assay (IFA) and an antigen detecting Elisa (ELISA). Based on the results of these three tests, Bayesian analysis indicated that the prevalence of G. duodenalis in dairy calves was 0.19 (95% Confidence Interval: 0.11-0.28) and that ELISA (Sensitivity (Se) 0.89 and Specificity (Sp): 0.90) and IFA (Se: 0.77 and Sp: 0.95) were both sensitive and specific diagnostic techniques, whereas microscopical examination was less sensitive (Se: 0.56 and Sp: 0.87). The proportion of positive farms was estimated as 0.42 (0.24-0.62). The prevalence and the cyst excretion in calves from different age categories were based on data obtained by IFA on all 499 samples. The prevalence was highest among four to five week old calves and remained high among older calves up to 10 weeks, but was lower among calves before the age of two weeks. The number of excreted cysts was estimated by IFA and ranged from 100 to 1,040,000 cysts per gram faeces, with a mean of 3516 cysts per gram faeces. The intensity of excretion peaked among four-week-old calves and remained high among calves up to the age of eight weeks. This is the first known study to use Bayesian analysis to estimate the prevalence of G. duodenalis in the faeces of dairy calves and to estimate test characteristics of diagnostic assays used for the detection of G. duodenalis.

Evaluation of the chemoprophylactic efficacy of 10% long acting injectable moxidectin against gastrointestinal nematode infections in calves in Belgium.

The chemoprophylactic efficacy of a single dose of the 10% long acting (LA) injectable formulation of moxidectin on nematode infections in calves, was evaluated. Two similar groups of 11 female, first grazing season Holstein calves were turned out in early May on separate plots of a single, naturally infected pasture. Until 56 days post-treatment (pt), the percentage reduction in faecal egg output was 100%, remaining above 90% during the entire trial, except for day 126 pt. More than 90% of the larvae in the treated group were identified as Cooperia until 140 days after treatment and more than 70% during the rest of the trial, whereas in the control group Cooperia was the most abundant species until day 84 pt and Ostertagia from 126 days pt onwards. The reduction in faecal egg output in the treated group was reflected in the mean pepsinogen levels being below the pathogenic threshold at the end of the grazing season (1.8 units of tysrosine (U tyr)) and the absence of diarrhoea during the second half of the grazing season. In the control group pepsinogen levels remained high (mean: 5.5 U tyr) and prolonged diarrhoea occurred in the second half of the grazing season. Furthermore, the weight gain for the treated group at the end of the grazing season was 41.9 kg higher than for the control group. At necropsy, the reduction in O. ostertagi worm burden in the treated group was 97.5% compared to the control group, while the reduction in C. oncophora worm burden was 57%. An additional benefit of the long acting parasitological control, was reduced pasture contamination.

Production benefit of treatment with a dual active oral formulation of derquantel-abamectin in slaughter lambs.

Gastrointestinal nematodes have a negative impact on the productivity of grazing sheep. Control of these infections has relied for decades on the use of anthelminics, leading to anthelmintic resistance (AR) worldwide, including the UK. The use of combination anthelmintics has been advocated as one of the tools in managing AR and decreasing the economic losses associated with AR. In this study, the benefit of a new combination (derquantel plus abamectin; DQL+ABA: Startect(®) Dual Active Oral Solution for Sheep, Zoetis, at 1 mL/5 kg bodyweight) was evaluated on a farm with suspected AR to benzimidazoles, by incorporating it into the existing treatment regime. In total 100 lambs were selected and allocated to one of two treatment groups, which were treated either with DQL+ABA or fenbendazole/levamisole at monthly intervals. All lambs were co-grazing the same pasture. Weight gain and carcass quality was evaluated, as well as treatment efficacy. The efficacy of DQL+ABA was high throughout the grazing season, whereas the efficacy of the fenbendazole/levamisole treatment regime was below the threshold for anthelmintic efficacy. The high efficacy of a monthly treatment with DQL+ABA resulted in a significantly higher average daily weight gain and shorter time to reach slaughter.