BackgroundFasciola hepatica is a helminth parasite of global importance in livestock, with major economic impact. However information on F. hepatica infections in Irish pasture-based dairy herds is limited. Therefore this study was conducted in order to determine the prevalence, seasonality and management factors associated with F. hepatica. A total of 319 Irish dairy herds were selected for this study. Bulk tank milk (BTM) samples were collected from 290 dairy farms on a quarter year basis, while from a further 29 dairy farms BTM samples were collected on a monthly basis to provide a more detailed pattern of F. hepatica exposure in Irish herds. BTM samples were analysed using a commercially available F. hepatica antibody detection ELISA. Furthermore, within-herd prevalence of F. hepatica was assessed in a subset of these 29 herds (n = 17); both individual serum samples and bulk tank milk samples were collected.ResultsA within-herd prevalence of ≤ 50 % was found for herds with negative bulk tank milk samples. The mean prevalence of the 290 study herds was 75.4 % (Range 52 %–75.1 %), with the highest prevalence being observed in November (75.1 %). The seasonal pattern of F. hepatica shows elevated antibodies as the grazing season progressed, reaching a peak in January. A significant association was found between F. hepatica and age at first calving.ConclusionThis study demonstrates that F. hepatica is present in a large proportion of Irish dairy herds and provides a basis on which control practices, particularly in adult dairy cows, can be reviewed.
Completion of the F. hepatica lifecycle is dependent on suitable climatic conditions for development of immature stages of the parasite, and its snail intermediate host. Few investigations have been conducted regarding temporal variations in F. hepatica status in Irish dairy herds. The current study aimed to conduct a longitudinal study examining annual and seasonal trends in bulk milk seropositivity over six years, while also investigating associations with soil temperature, rainfall and flukicide treatment. Monthly bulk milk samples (BTM) were submitted by 28 herds between March 2009 and December 2014. In all, 1337 samples were analysed using a Cathepsin L1 ELISA. Soil temperature, rainfall and management data were obtained for general estimating equation and regression analyses. A general decrease in milk seropositivity was observed over the six year study period and was associated with an increased likelihood of treating for liver fluke (OR range=2.73-6.96). Annual and seasonal analyses of rainfall and F. hepatica BTM status yielded conflicting results. Higher annual rainfall (>1150mm) yielded a lower likelihood of being BTM positive than annual rainfall of <1000mm (OR=0.47; P=0.036). This was most likely due to farmers being more proactive in treating for F. hepatica in wetter years, although a 'wash effect' by high rainfall of the free living stages and snails cannot be ruled out. Higher seasonal rainfall (>120mm), however, was associated with increased ELISA S/P% values (Coefficient=9.63S/P%; P=0.001). Soil temperature was not found to influence F. hepatica to the same extent as rainfall and may reflect the lack of severe temperature fluctuations in Ireland. Flukicides active against both immature and mature F. hepatica were approximately half as likely to record a positive F. hepatica herd BTM status than a flukicide active against only the mature stage of the parasite (OR≅0.45; P<0.01). This study highlights the importance of examining both annual and seasonal F. hepatica data, which can vary significantly. Additionally, it highlights the progress that can be achieved in fluke control by application of a continuous BTM monitoring program.
Triclabendazole is a flukicide used in the treatment of liver fluke in cattle. However, its use in the treatment of liver fluke is prohibited in dairy cows. In this work, two independent studies were designed to investigate the persistence of triclabendazole residues in milk following the administration of 10% Fasinex® as dry-cow and lactating-cow treatments. In the dry-cow study, 36 in-calf dairy cows were treated with a commercial product, 10% Fasinex(®), at drying-off and three triclabendazole residues (triclabendazole, triclabendazole sulphoxide and triclabendazole sulphone) were monitored in the milk following calving, approximately 60 days post-treatment. No residues were measurable in the milk of the 36 cows tested - the LOQ of the method was 1.00 µg kg(-1). In the lactating-cow study, the persistence of four triclabendazole residues was investigated in the milk of six dairy cows. The highest levels of triclabendazole, triclabendazole sulphoxide, triclabendazole sulphone and keto-triclabendazole residues measured in individual milk samples were 244, 525, 1710 and 16 μg kg(-1), respectively. Residues of triclabendazole, triclabendazole sulphoxide, triclabendazole sulphone and keto-triclabendazole were detectable in milk for up to 5.5, 15.5, 20 and 5 days post-treatment, respectively. Triclabendazole sulphone was found to be the most important residue, accounting for >87% of marker residues at ≥3.5 days following drug administration. These results indicate that following treatment at drying-off, triclabendazole residues in milk post-calving are well below the current MRL. Therefore, triclabendazole is a suitable flukicide for use during the dry period.
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