Development of a milk and serum ELISA test for the detection of Teladorsagia circumcincta antibodies in goats using experimentally and naturally infected animals.

Teladorsagia circumcincta is among the most important gastrointestinal parasites in small ruminants and the predominant species in Southern European goats. Parasite control is largely based on metaphylactic/preventative treatments, which is often seen as non-sustainable anymore. The reasons are increased consumer demand to reduce chemicals in livestock production and anthelmintic resistance against the common drugs. This study aimed at the development of a T. circumcincta-enzyme-linked immunosorbent assay (ELISA) specifically for goats. Samples were obtained from goats raised parasite-free or infected experimentally. Sampling continued during the following pasture season and housing period. The sensitivity for the use in bulk milk samples as an indicator of T. circumcincta infection levels in grazing goats was examined. The ELISA enables clear differentiation of negative and positive animals. With a specificity of 100% negative cut-off values for serum and milk were 0.294 and 0.228 (sensitivity, 95%). Positive cut-off values (sensitivity, 90%) were 0.606 (serum) and 0.419 (milk), while a sensitivity of 95% resulted in 0.509 and 0.363, respectively. The grey-zone between negative/positive cut-offs was introduced to deal with animals in pre-patency and decreasing antibody levels after infection. There was no cross reactivity for Trichostrongylus colubriformis and Cooperia oncophora while for Haemonchus contortus and Fasciola hepatica it cannot be fully excluded currently. In bulk milk samples, 5% of the milk had to be contributed from animals infected with T. circumcincta to be detected as positive. The results derived from experimentally and naturally infected as well as parasite naïve animals indicate the potential of the ELISA to be used in targeted anthelmintic treatment regimes in goats.

Evaluation of the Egg Hatch Assay and the Larval Migration Inhibition Assay to detect anthelmintic resistance in cattle parasitic nematodes on farms.

Resistance to anthelmintic drugs, particularly to the widely used benzimidazoles (BZs) and macrocyclic lactones (MLs) is an increasing problem in cattle industries worldwide. Reliable methods for the assessment of anthelmintic efficacy in the field are required in order to react before resistance becomes an obvious problem on individual properties. The ability of the Egg Hatch Assay (EHA) and the Larval Migration Inhibition Assay (LMIA) to detect anthelmintic resistance under field conditions was evaluated on cattle farms in Northern Germany. As published previously Faecal Egg Count Reduction Test (FECRT) was performed using oral albendazole (Valbazen®) or injectable ivermectin (Ivomec®). Herein the FECRT results described earlier were compared with data from EHAs or LMIAs, respectively, performed with eggs from fresh faeces or larvae from faecal cultures of the tested animals before and after treatment. The obtained EC(50) values allowed the assessment of efficacy of albendazole and ivermectin on farm level. The results of the FECRTs and the results of both in vitro assays were comparable. In comparison to the FECRT the in vitro assays are less time, labour and cost intensive and are able to assess the susceptibility status of a worm population without treatment. Therefore both are beneficial alternatives for the reliable detection of reduced efficacy of these two drug classes on farms.

[Experiences with the FAMACHA-Eye-Colour-Chart for identifying sheep and goats for targeted anthelmintic treatment]. / Erfahrungen mit der FAMACHA- Eye-Colour-Karte zur Identifizierung von Schafen und Ziegen für die gezielte anthelminthische Behandlung.

The bloodsuckling abomasal parasite Haemonchus contortus is the most pathogenic worm in sheep and goats. High prevalences of anthelmintic-resistant isolates make H. contortus difficult to control. Detecting the most anaemic animals could support a targeted selective treatment approach. Leaving the rest of the flock untreated would generate a refuge for anthelmintic-sensitive parasites. South-African researchers tried the FAMACHA-Eye-Colour-Chart for anaemic sheep and goats with good success. Field studies, carried out in Northern Germany on naturally infected sheep and goats showed, that at a comparatively low prevalence of H. contortus the FAMACHA-test proved not being sufficient in detecting all animals with high fecal egg counts. Under these conditions there was no satisfying reliability to identify small ruminants for selective deworming only based on the FAMACHAEye-Colour-Test. But if not working hours are the limiting factor, the repeated score could support the selection of pale animals in need to be treated.