Economic assessment of Ostertagia ostertagi and Fasciola hepatica infections in dairy cattle herds in Germany using Paracalc®.

The aim of the current study was to estimate economic costs of Ostertagia ostertagi and Fasciola hepatica infections in dairy cattle herds in Germany using the online calculation programme Paracalc®. Following a questionnaire, survey data were available from 464 farms in 14 federal states. On those farms bulk tank milk (BTM) samples and additionally up to six serum samples collected from first season grazing calves were analysed, using a commercially available ELISA (Boehringer Ingelheim SVANOVA Biotech AB, Uppsala, Sweden), an in-house ELISA (F. hepatica) and an in-house serum pepsinogen test. In total, samples obtained from 344 farms were included in the analysis since those were the only farms with complete questionnaires. Median costs per farm and year were estimated for gastrointestinal (GI) nematode infections (€721.38) and F. hepatica infection (€565.61). Decreases in milk yield in multiparous cows were the major reason for annual production losses due to GI nematodes (€13.33 per cow) and F. hepatica infections (€7.95 per cow), which was followed by annual costs for anthelmintic treatment against GI nematode infections in adult cows (€10.00 per cow) and F. hepatica infection associated annual costs due to repeated artificial insemination (€10.13 per cow) and prolonged calving intervals (€9.40 per cow). The study demonstrated that if all required information is provided, the Paracalc® tool can assist to identify productions losses in dairy cattle herds due to helminth infections and to optimise farm economics in Germany.

Ostertagia spp., rumen fluke and liver fluke single- and poly-infections in cattle: An abattoir study of prevalence and production impacts in England and Wales.

This study aims at investigating the occurrence, risk factors and production impacts on beef carcass parameters of three of the most important cattle helminth infections in England and Wales. Abomasa, reticulorumens and livers from healthy cattle were collected and examined post-mortem quarterly over a one year period in an abattoir in South-West England. Specific viscera from 974 cattle were collected, examined and scored for Ostertagia spp., adult rumen fluke and liver fluke lesions/presence. A total of 89%, 25% and 29% of the carcasses had lesions/presence of Ostertagia spp., rumen fluke and liver fluke, respectively, and 39% had presence of helminth co-infection. Animal demographic and carcass parameters associated with helminth infections were investigated using multilevel multinomial and multilevel linear mixed models respectively. After adjusting for other factors, significant differences in the distribution of helminth infections were observed among cattle by type of breed, animal category (cow, heifer, steer and young bull), age, season and concurrent helminth infections. Compared to carcasses free of helminths, carcasses presenting solely Ostertagia Spp. lesions or adult rumen fluke had significantly lower cold carcass weight (coef.: -30.58 [-50.92;-10.24] and -50.34 [-88.50;-12.18]) and fat coverage (coef.: -3.28 [-5.56;-1.00] and -5.49 [-10.28;-0.69]) and carcasses presenting solely liver fluke lesions had significantly lower conformation grade (coef.: -3.65 [-6.98;-0.32]). Presence of helminth poly-infections was negatively associated with cold carcass weight.

Associations between anti-Fasciola hepatica antibody levels in bulk-tank milk samples and production parameters in dairy herds.

Our primary objective was to determine the relationships between Fasciola-specific antibody levels in bulk-tank milk and measures of productivity to estimate economic losses that are associated with Fasciola infections. A bulk-tank milk sample was collected in March 2004 from 1105 dairy herds in Flanders and the antibody levels against Fasciola hepatica (ODRf) and Ostertagia ostertagi (ODRo) were determined. The association of ODRf with four production parameters (milk yield, milk-protein %, milk-fat % and inter-calving interval) was assessed by multivariable linear-regression models. Production data were available for 463 out of the 1105 herds sampled. An increase in ODRf from the 25% quantile (0.428) to the 75% quantile (1.064) was associated with a decrease in the annual average milk yield of 0.7kg/(cowday) (P=0.002), with a decrease in the average milk-fat % of 0.06% (P<0.001) and with an increase of the mean inter-calving interval of 4.7 days (P=0.03). No significant relationship was found with the average milk-protein %. When the relationships of ODRf and ODRo with milk yield were tested simultaneously, we saw an additive rather than synergistic effect of concurrent infections.

Current research and future prospects in the development of vaccines against gastrointestinal nematodes in cattle.

Vaccination is being considered as the most feasible alternative for anthelmintic drugs to control gastrointestinal nematode infections in cattle. However, despite the identification of several candidate protective antigens, no vaccines against gastrointestinal nematode parasites are currently available. The main problems that hamper the development of nematode vaccines in ruminants are that vaccination with recombinant nematode proteins produced in bacterial or eukaryotic expression systems did not induce a protective immune response and no suitable antigen delivery system is available for presentation of protective worm antigens to the bovine mucosal immune system. The present review will focus on recent advances and remaining obstacles in vaccine development against gastrointestinal nematodes in cattle, in particular against the abomasal parasite Ostertagia ostertagi.

The economics of parasite control: obstacles to creating reliable models.

Models of the population biology and transmission of helminth parasites of domestic ruminants do not generally include any explicit reference to production because that would require the identification of a systematic relationship between parasitism and production loss. This is difficult because (1) the relationship between parasitism and production loss (in so far as we can identify one) is non-linear, (2) it is by no means clear which index of parasitism we should use in defining the nature of the relationship and (3) time delays in the system and the multicausal nature of production losses make it difficult to tease out those components of the loss that are attributable to parasitism.

Economic benefits of parasite control in cattle.

The economic losses often associated with parasitism in cattle are universally accepted. The degree of economic significance related to these losses, the burdens of parasites required to cause such losses, and the specific control measures needed to avoid these losses are, however, topics of serious debate and outright disagreement among parasitologists and veterinarians. This is because most cattle have parasite burdens that are truly subclinical, with no obvious signs of parasitism but significant losses in potential production. These losses are often very insidious in nature and often difficult to prove statistically in a consistent manner. This discussion focuses on the need to: (1) define the benefits related to parasite control in cattle; (2) develop clear and effective parasite control recommendations that will allow the producer to realize these benefits; (3) effectively transfer this information to the cattleman.

Mathematical models of the population biology of Ostertagia ostertagi and Teladorsagia circumcincta, and the economic evaluation of disease control strategies.

The construction and use of mathematical models of the population biology of Ostertagia ostertagi and Teladorsagia circumcincta is discussed. Simulated field trials implemented by deterministic mathematical models currently share with actual field trials the disadvantage that they convey no information concerning the risk associated with the net return demonstrated by the trial. This has important implications when it is necessary to rank disease control strategies in order of usefulness.

Economics of deworming beef cattle.

From the practitioner level and for the producer, there is far too much confusion concerning internal parasites in cattle and the justification of control measures. By coordinating research efforts between parasitologists and other scientists, awareness of internal parasites will be raised and the total impact of parasitism can better be evaluated.