Oocyst shedding patterns of Eimeria species and their association with management and performance at ten rose veal starter farms in the Netherlands

Coccidiosis at rose veal starter farms is often diagnosed however, this was the first study performed considering this topic on this type of rearing unit. The objective of this study was to identify Eimeria species faecal shedding patterns at ten Dutch rose veal starter farms during rearing. Further objectives were to investigate associations with (gut) health, production and management decisions. Faecal samples from twelve randomly selected calves per farm were collected weekly during 9 consecutive weeks. Thereafter samples were pooled in a predetermined composition of six. These calves were clinically evaluated every sample visit and weighed at the first and last visit. Laboratory tests included a flotation test of the samples. If this yielded Eimeria oocysts, both oocysts per gram feces (OPG) and species differentiation were established using a modified McMaster method. Management parameters and technical herd results were identified after finalizing the study period using a questionnaire. Studied patterns in oocyst shedding included the pool's cumulated OPG, maximum OPG level and the number of sample days (SD) that OPG exceeded a confirmed level. Statistical analysis included univariate and multivariate analysis. Associated (p < 0.10) OPG patterns considering rumen fill, faecal consistency and average daily weight gain (ADG) were tested using a model with herd included as random effect. RESULTS: on all ten farms E. alabamensis, E.bovis and E. zuernii besides non-pathogenic species were identified, often as mixed infections. Peak OPG occurred predominately at SD 21 and 28 (E. alabamensis and E. bovis), and at SD 42 (E. zuernii). In 16 pools, OPG levels ≥500 for E. bovis or E. zuernii, were found. Significant correlation (p < 0.0001) showed between the log₁₀ OPG of pathogenic Eimeria and of all Eimeria species. Multivariate analysis showed significant correlation between cumulative faecal consistency scores and cumulative log₁₀ OPG of pathogenic Eimeria species (β = 0.16; p = 0.008). Pools exceeding 750 OPG for E. bovis showed 93 g lower ADG and pools experiencing ≥2 SD with >1000 OPG for E. alabamensis 141 g lower ADG. From the questionnaire we identified lower cumulated OPG of all Eimeria species except for E. bovis at farms where the units were cleaned before arrival of the calves. CONCLUSION: As a rule, on Dutch rose veal starter farms, mixed Eimeria infections occur, but shedding patterns differ between farms. Clinical and growth performance is related to OPG patterns found. Cleaning units before arrival of calves lowers oocyst shedding during the rearing period.

Pitfalls and opportunities of teaching veterinary parasitology within an integrated curriculum

The Faculty of Veterinary Medicine at Utrecht University has seen three major curriculum changes, in 1995, 2001 and 2007. The last change was made because of the European change to a Bachelor-Master system. Almost each time teaching hours tagged for veterinary parasitology have been reduced to currently a minimum of between 46 and 51.5 h, which is much less than the WAAVP-recommended minimum of 70-90 h. This results in a challenge to maintain a qualitatively adequate veterinary parasitology program in a curriculum. Following a brief historic account of previous curricula and implemented curriculum changes, experiences, limitations and opportunities are discussed, including the potential of introducing new teaching materials based, for example, on digital technologies and gaming.

Presence and species identity of rumen flukes in cattle and sheep in the Netherlands

The purpose of the study was to gain knowledge about the prevalence and identity of rumen flukes (RF) in cattle and sheep in the Netherlands. Routine faecal examinations of diagnostic submissions between May 2009 and September 2014 showed a mean annual herd or flock RF prevalence of 15.8% for cattle and 8.0% for sheep. Prevalence in cattle was higher after 2012 than before, which may reflect a change in detection method as well as an increase in true prevalence. During November and December 2014, an abattoir survey was conducted to allow for scoring of rumen fluke burden and to obtain specimens for molecular species characterization. Over 8 visits to 5 abattoirs in areas deemed to pose a high risk for trematode infection, 116 cows and 41 sheep from 27 herds and 10 flocks were examined. Prevalence of RF was higher in beef cattle than in dairy cattle and higher in cattle than in sheep. Median fluke burden was >100 specimens per animal for most positive animals. Using a semi-quantitative RF density score as a gold standard, sensitivity and specificity of a modified quantitative Dorsman egg counting method were estimated at 82.6% and 83.3%, respectively. Of 14 collected adult rumen flukes, twelve (8 bovine and 4 ovine specimens) were identified as Calicophoron daubneyi. The other two, of bovine origin, were identified as Paramphistomum leydeni, which was unexpected as in other European countries all recently collected rumen flukes in both cattle and sheep were identified as C. daubneyi. The findings implicate that multiple rumen fluke species, intermediate host species and transmission cycles may play a role in rumen fluke infections in the Netherlands.

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.

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.

[Prevalence of Tritrichomonas foetus among Dutch cats]

Prevalence of Tritrichomonas foetus among Dutch cats The aim of this study was to determine the prevalence of and risk factors for, Tritrichomonas foetus among cats in the Netherlands. A total of 154 faecal samples were collected from three groups of cats: cats with diarrhoea (n=53), cattery cats (n=47), and healthy pet cats (n=54). Faecal samples were examined with a T. foetus specific real-time PCR. All PCR-positive samples were run on gel electrophoresis for definitive diagnosis. The prevalence of T. foetus was 2% among cats with diarrhoea and 4% among cattery cats; T. foetus was not prevalent among pet cats (none of the samples tested positive). Questionnaires had been distributed to cat and cattery owners to determine risk factors for T. foetus, but the low prevalence precluded statistical analysis of the questionnaire results.

[Frequent deworming in horses; it usually does not do any good, but it often harms]

Due to excessive and inappropriate use of dewormers anthelmintic resistance has developed as a significant problem in horse parasites in the Netherlands. Since it is unlikely that new classes of anthelmintics against horse nematodes will be introduced in the near future, it is important to use the present drugs wisely. Veterinarians should advice horse owners about worm control programs with a more targeted approach. The number of anthelmintic treatments should be reduced and, through selective anthelmintic treatments, further development of anthelmintic resistance should be delayed. Preferably, horses with a low faecal egg count should not be treated at all to ascertain a reduction of the selection pressure for anthelmintic resistance. The propensity for low faecal egg counts is hereditary. This implies that mature horses with consistent low egg counts can be detected by faecal examination and that it is not necessary to repeat faecal examination each time in these animals. New horses on the farm should always be dewormed on arrival and should be introduced only after the efficacy of treatment has been determined. Anthelmintic resistance can also be introduced with the arrival of a new animal that is infected with drug-resistant parasites.