Changes in the immune system indicators serum hemagglutinating activity, complement levels, antibody titer, and lymphocyte number and in the plasma levels of cortisol and glucose in the gilthead sea bream (Sparus aurata) indicated that stress was induced when fish were chased daily for 8 min with a hand-held net for 16 days. Plasma levels of cortisol and glucose were elevated after 1 day and cortisol remained above prestress levels throughout the experiment. The immune system was altered as indicated by lymphocytopenia and decreases in hemolytic activity, agglutination capacity, and antibody titer. As these results show, for the first time, that the complement system is depressed after stress, a routine complement analysis is suggested as an additional technique for assessing the health status of fish.RCsumC : La rCponse de stress a Ct C m&surCe sur la dorade (Sparus aurata) aprks 16 jolmrs de poursuite rkgulikre (8 minijour). On a analysi le cortisol et la glucose plasmatiques et des rdponses immunologiques, comme 19activite hemagglutinante du sCrum, l'action himolysante du complkment, la titration des anticorps et le nombre de lymphocytes circulants. Les rCsultats montrent une augmentation du cortisol et de la glucose aprks Ie premier jour, laquelle continue pour le cortisol jusqu'i la fin de l'expdriment, ou on trouve l mne stabilisation. Toutes les r6powses immunologiques sont affeetCes. On trouve lymphocytopenie et une baisse de 19activitC hCmolitiqlme, de la capacite d'agglutination et de la titration des anticorps. Puisque ces aCsultats iwdiquent l'inhibition du systkme du complCment par le stress, on suggkre l'addition des analyses du compl6rnent B I'ensemble des autres indicateurs sanitaires des poissows.

Background Due to increased anthelmintic resistance, alternative methods to drugs are necessary to control gastrointestinal nematodes (GINs). Some of the most promising alternatives are based on the immune response of the host, such as the selection of genetically resistant breeds or the use of vaccines against these parasites. Given the limited information available on the immune response against GINs in goats, this study investigated the local immune response of goat kids of an indigenous Canary Islands breed (Majorera breed) experimentally infected with Teladorsagia circumcincta, one of the most pathogenic and prevalent GIN species. Methods For this purpose, the relationship between different parasitological (number of mature and immature worms, worm length, and number of intrauterine eggs) and immunological parameters at the local level (related to both the humoral and cellular immune response) was analyzed at early (1 week post-infection [wpi]) and late (8 wpi) stages of infection. Results Primary infection of goat kids with T. circumcincta infective larvae (L3) generated a complex immune response that could be defined as Th2 type, characterized by increased infiltration in abomasal tissues of several effector cells as well as a progressive presence of specific antibodies against parasitic antigens in the gastric mucus. Cellular responses were evidenced from 1 wpi onward, showing an increase in antigen-presenting cells and various lymphocyte subsets in the gastric mucosa. Conclusions The complexity of the host response was evidenced by statistically significant changes in the number of all these subpopulations (MHCII+, CD4+, CD8+, γδ+, CD45R+, IgA+, and IgG+), as well as in the evolution of the relative cytokine gene expression. From a functional point of view, negative associations were observed between the number of most of the immune cells (CD4, IgA, IgG, and CD45R cells) and parameters that could be related to the fecundity of worms, a phenomenon that was especially evident when the number of IgG and CD45R cells or the specific IgA levels of the gastric mucus were compared with parasitological parameters such as the female worm length or fecal egg counts at 8 wpi. Graphical Abstract

Due to increased anthelmintic resistance, alternative methods to drugs are necessary to control gastrointestinal nematodes (GIN). Some of the most promising alternatives for their sustainability are based on the immune response of the host, such as the selection of genetically resistant breeds or the use of vaccines against these parasites. Given the limited information available on the immune response against GIN in goats, this study was carried out on the local immune response of goat kids of a Canary Islands indigenous breed (Majorera breed) experimentally infected with Teladorsagia circumcincta, one of the most pathogenic and prevalent GIN species. For this purpose, the relationship between different parasitological and immunological parameters at local level (both related to the humoral and cellular immune responses) have been analyzed at early (1 week post-infection –wpi-) and late (8 wpi) stages of infection.Primoinfection of goat kids with T. circumcincta L3 generates a complex immune response that could be defined as Th2 type, characterized by an increase of infiltration in abomasal tissues of several effector cells as well as a progressive presence of specific antibodies against parasitic antigens in the gastric mucus. These cellular responses could be evidenced from 1 wpi onward, showing an increase in the gastric mucosa of antigen presenting cells and various lymphocyte subsets. The complexity of the responses developed is evidenced by the statistically significant changes in numbers of all these subpopulations, as well as in the evolution of the relative cytokine gene expression. From a functional point of view, negative associations were observed between the number of most of these cells (CD4, IgA, IgG, and CD45R cells) and parameters that could be related to the fecundity of worms, a phenomenon that was especially evident when the number of IgG or CD45R cells or the specific IgA levels of the mucus were compared with parasitological parameters such as the lenght of female worms or faecal egg counts at 8wpi.

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