We analyse a scattering problem of electromagnetic waves by a bounded chiral conductive obstacle, which is surrounded by a dielectric, via the quasi-stationary approximation for the Maxwell equations. We prove the reciprocity relations for incident plane and spherical electric waves upon the scatterer. Mixed reciprocity relations have also been proved for a plane wave and a spherical wave. In the case of spherical waves, the point sources are located either inside or outside the scatterer. These relations are used to study the inverse scattering problems.

The extent of periparturient relaxation of immunity (PPRI) to gastrointestinal nematode parasites is sensitive to metabolisable protein (MP) scarcity but also varies between breeds of sheep (Houdijk, 2008). For example, under ad libitum feeding, Scottish Blackface ewes had a lower extent of PPRI than Greyface ewes (Zaralis et al., 2008). Such between-breed variation in PPRI may not necessarily be associated with genetic resistance per se but could arise from a higher nutrient demand of the more productive Greyface ewes (Houdijk, 2008). This experiment was designed to test the hypothesis that if the extent of PPRI has only a nutritional basis, then the sensitivity of PPRI to MP scarcity will not differ between the breeds when MP feeding is adjusted for between-breed differences in MP demand.

The consumption of plants rich in plant secondary metabolites has been associated with improved resilience of parasitised hosts, i.e. their ability to perform under parasitic infection, compared to animals fed conventional feeds (Athanasiadou et al., 2007). Furthermore, such bio-active plants can improve host resistance, which refers to the host ability to regulate gastrointestinal nematode establishment, development, fecundity and survival (Athanasiadou et. al. 2008). Chichorium intybus L. (chicory) is such a bio-active forage and its potential anthelmintic activity is currently investigated as an alternative means to control parasitism in sheep production systems. In the present study we employed an in vitro assay to study a possible mechanism of anti-parasitic action arising from chicory, and to test whether this anthelmintic activity is affected by the vegetative stage of the plant.

The effect of sainfoin (Onobrychis viciifolia) hay consumption on the pathophysiology and local cellular responses of growing lambs during infection with Trichostrongylus colubriformis was investigated. Thirty-two lambs, 16 weeks of age, were allocated to 1 of 4 treatment groups (n=8) that were offered either grass (G) or sainfoin (S) hay while concurrently either infected (+), or not (−) with 12 000 L3 T. colubriformis larvae per week for 6 weeks. Liveweight gains were affected by diet (P=0·002) and reduced by infection (P<0·005). Faecal egg count was reduced in S+ compared to G+from days 35 to 42 (P=0·001); however, total egg output, worm burdens at day 42 and worm fecundity were similar between diets (P>0·05). Feeding sainfoin appeared to enhance immune cell development with tissue eosinophils, mast cells and pan T cells present in greater concentrations in S+ than in G+ animals. However, further studies are required to determine if the enhanced immune cell development is a consequence of a greater nutrient supply or a direct influence of sainfoin metabolites on local inflammatory responses to the gastrointestinal nematode T. colubriformis.

Metabolizable protein (MP) supplementation can reduce faecal egg count (FEC) in periparturient ewes, thus reducing pasture contamination for their lambs (Houdijk et al. 2006). In addition, lambs grazing on bioactive forage (chicory) had lower FEC than lambs grazing grass/clover (Athanasiadou et al. 2007). Both periparturient MP nutrition and grazing on chicory increase lamb performance but these approaches have been developed and investigated independently. The objective of this experiment was to assess their interactive effects on lamb parasitic status and performance. It was hypothesised that, although beneficial effects of maternal nutrition will be augmented with subsequent grazing on bioactive forage, the magnitude of the latter effect will be higher for lambs from unsupplemented ewes.

Nematode egg excretion by periparturient ewes is the main source of infection for their immunologically naïve lambs. It has been shown that periparturient metabolizable protein (MP) supplementation can reduce nematode egg excretion (Houdijk et al, 2003). The latter experiment used a single moderate level of infection, but effects of MP supply on periparturient parasitism may depend on the level of infection. The objective of this study was to investigate the effects of MP supplementation on parasite control, ewe and lamb performance in ewes trickle infected with the abomasal nematode Teladorsagia circumcincta at three different infection levels. We hypothesised that the magnitude of beneficial effects of MP supplementation will be higher at the highest level of infection due to the expected nutrient drain on the host.

The use of medicinal plants for the prevention and treatment of gastro-intestinal parasitism has its origin in ethnoveterinary medicine. Although until recently the majority of the evidence on the antiparasitic activity of medicinal plants was anecdotal and lacked scientific validity, there is currently an increasing number of controlled experimental studies that aim to verify and quantify such plant activity. There are indeed a large number of plants whose anthelmintic activity has been demonstrated under controlled experimentation, either through feeding the whole plant or administering plant extracts to parasitised hosts. However, contrary to traditional expectation, there are also a great number of plants with purported antiparasitic properties, which have not been reproduced under experimental conditions. In this paper, we discuss the source of such inconsistencies between ethnoveterinary wisdom and scientific experimentation. We focus on the strengths and weaknesses of the existing methodologies used in the controlled studies to determine the activity of antiparasitic plants. We discuss issues like the seasonal and environmental variability of the plant composition, and how this can affect their antiparasitic properties and highlight the importance of identifying the mechanisms of action of such plants and the target parasite species. In addition to their antiparasitic properties, medicinal plants may also have anti-nutritional properties, which can affect animal performance and behaviour. For this reason, we emphasise the need for considering additional dimensions when evaluating medicinal plants. We also question whether using similar criteria as those used for the evaluation of anthelmintics is the way forward. We propose that a holistic approach is required to evaluate the potential of medicinal plants in parasite control and maximise their benefits on parasitised hosts.

The aim of the present study was to investigate the potential benefits of grazing lactating ewes and their lambs on chicory (Cichorium intybus). Fifty-six certified organic twin-rearing ewes were either drenched with an anthelmintic or not, within 2 days after parturition and were grazed upon either grass/clover or chicory pastures. Around 12 weeks after parturition a subset of 12 lambs per treatment was slaughtered for worm number and parasite species determination. The faecal egg counts of lambs from undrenched ewes grazing on chicory were significantly lower than those of lambs from undrenched ewes grazing on grass. Lambs grazing on chicory had similar abomasal worm counts as those grazing on grass at 12 weeks of age; the predominant species was Teladorsagia circumcincta. There was no difference between the intestinal worm counts in lambs grazing on grass or chicory, with Trichostrongylus vitrinus being the predominant species. Liveweight gains over the 126-day experimental period were significantly higher in lambs from drenched than those from undrenched ewes. Lambs from undrenched ewes grazing on chicory had higher liveweight gains compared to those from undrenched ewes grazing on grass. Although chicory grazing did not affect ewe nematode egg excretion, it resulted in lower egg counts in lambs and improved their liveweight gains to the same level as those deriving from drenched ewes.

The health and welfare of organically-farmed livestock are of concern due to restrictions on the use of veterinary medicines. Non-organic systems control nematodes using prophylactic treatment with anthelmintics. Routine drenching is banned within organic agriculture, and farmers are encouraged to find alternative methods of control, for example grazing management practices. This study investigated the level of nematode parasitism in organic and non-organic dairy herds around Scotland.

Sainfoin is a leguminous, highly nutritive plant with bloat free characteristics, suitable for growing lambs. In addition, sainfoin has been tested for its anthelmintic properties in goats and sheep, because of its high content of plant secondary metabolites (PSM), specifically condensed tannins. However, Athanasiadou et al. (2005) compared the effect of sainfoin vs lucerne on sheep and the animals showed poor performance, manifested as a lower intake and liveweight gain. But on the other hand, the intake of sainfoin resulted in lower daily parasite egg output. The hypotheses of the present study were: (1) The consumption of sainfoin hay in lambs continuously infected with T. colubriformis will result in negative effects on the parasites, measured through levels of faecal egg counts (FEC). (2) The parasite infection will affect grass hay intake more than sainfoin hay intake, because the PSM content will allow animals to cope better with the parasitic infection. (3) The use of an adaptation period to sainfoin hay prior to infection is expected to improve the parasite control of growing lambs continuously infected with T. colubriformis, through the establishment of a hostile environment for the incoming larvae and also will ameliorate the possible negative effects of PSM contained in sainfoin on the performance of the sheep.

Plant secondary metabolites (PSM) are widely known for their antinutritional properties; their excessive consumption can detrimentally affect herbivore health and, in some cases, survival. However, a growing body of evidence is suggesting that some classes of PSM may also have some positive effects on herbivores. Such positive effects include the antiparasitic properties of certain PSM and their beneficial consequences on the herbivore's fitness. One of the better-exploited classes of PSM that have been reported with anthelmintic properties is that of the condensed tannins. The consumption of moderate concentrations of condensed tannins has resulted in reduced level of parasitism in sheep and other ruminants. In this paper we discuss the conditions that should be met in order for the positive anthelmintic properties of PSM, and condensed tannins in particular, to be beneficial for parasitised sheep. We also examine whether PSM could have a role in controlling parasitism in ruminants and point out the future research needed to achieve an efficient use of PSM for parasite control.

The aim of this study was to investigate the effects of grazing different bioactive forages on acquired immunity against Teladorsagia circumcinta infection. The development of immunity was assessed by following the response of trickle-infected lambs grazing chicory (Cichorium intybus; IC), sulla (Hedysarum coronarium; IS) or grass/clover (Lolium perenne/Trifolium repens; IGC), to a single challenge infection. Parasite-naive lambs, grazing grass/clover, were also challenged with the single infection dose providing the uninfected control (UGC) group. Trickle infection significantly reduced worm establishment, inhibited larval development and increased mucosal mast cell (MMC) and globule leucocyte (GL) cells. Grazing treatment (chicory, sulla or grass/clover) significantly affected adult worm (P<0·05), late-L4 (P<0·01) and mid-L4 (P<0·01) larval-stage recoveries of the trickle-infected lambs, with IGC group always carrying higher worm burdens than either IC or IS lambs. MMC and GL cells of trickle-infected lambs were positively correlated with the proportion of early-L4 worms recovered and negatively correlated with both the proportion of adult worms recovered and the total worm establishment, suggesting that the observed effects were due to an enhanced immune response. The results suggest elevated immune responses against T. circumcincta infections in growing lambs grazing on either sulla or chicory compared to those grazing on grass/clover, probably due to differences in forage nutritional values.

The potential antiparasitic effects of chicory (Cichorium intybus ) are currently investigated as an alternative means to control parasitism in organic sheep production systems. Previous studies showed that parasitised lambs grazing on parasite-clean chicory swards had improved growth and lower faecal egg counts (FEC) compared to those grazing on parasite-clean grass pastures (Athanasiadou et al, 2004). The objective of this experiment was to investigate whether chicory can have a role as a potential means to control parasitism in lactating ewes and their lambs grazing on previously parasite contaminated pastures.