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A majority of Kudoa spp. infects the somatic muscle of fish establishing cysts. Previously, elevated humoral responses were detected in BALB/c mice immunised with Kudoa sp. pseudocyst extracts and in BALB/c mice orally inoculated with Kudoa sp. pseudocysts, as well as the presence of anti-Kudoa sp. antibodies in human sera by enzyme-linked immunosorbent assay. The objective of this work was to test Kudoa sp. pseudocyst extracts by the skin prick test. Fifteen patients with gastroallergic and/or allergic symptoms related to fish ingestion were examined. Kudoa sp. pseudocyst extracts were administered (1 mg/ml) on the volar forearm skin. Four of the 15 selected patients were positive to Kudoa sp. extracts. The saline solution negative control did not induce any reaction.

A majority of Kudoa species infect the somatic muscle of fish establishing cysts. Because there is no effective method to detect infected fish without destroying them, these parasitised fish reach the consumer. The elevated humoral responses detected previously by us in BALB/c mice immunised with Kudoa sp. pseudocyst extracts and the high IgG1 and IgE levels induced by the oral administration of Kudoa pseudocysts to BALB/c mice showed the possible immunopathological effects in man from the ingestion of Kudoa-infected fish. In this work, we investigated the seroprevalence of anti-Kudoa sp. antibodies in a Spanish healthy population and the possible association between the manifestation of allergic reactions after fish consumption and the humoral responses to Kudoa sp. antigens. Specific anti-Kudoa sp. antibody levels in sera of patients diagnosed with several digestive pathologies were also determined, studying their possible association with the alteration of analytic parameters in these patients.

The majority of Kudoa species infect the somatic muscle of fish, establishing cysts. Because there is no effective method to detect infected fish without destroying them, these parasitized fish reach the consumer. The elevated humoral responses detected previously by us in BALB/c mice immunized with Kudoa sp. pseudocyst extracts showed the possible immunopathological effects in man from the ingestion of Kudoa-infected fish. In this work, the high IgG1 and IgE levels induced by the oral administration of Kudoa pseudocysts to BALB/c mice confirmed the allergenic nature of some of their components. An alternative way of preparing the soluble extract by using a FastPrep' shaker indicated the inconvenience of using sonication to prepare the Kudoa sp. extract. IgG+M, IgG, IgG3 and IgA cross-reactions of Kudoa sp. with another myxosporean, Myxobolus aeglefini, were found.

Summary:The majority of Kudoa species infect the somatic muscle of fish establishing cysts. As there is no effective method to delect infected fish without destroying them, these parasited fish reach the consumer. We have developed this work to determine whether this parasite contains antigenic compounds capable of provoking an immune response in laboratory animals, in order to consider the possible immunopathological effects in man by the ingestion of Kudoa infected fish. BALB/c mice were injected by the subcutaneous route with the following extracts suspended in aluminium hydroxide: Group 1 (black Kudoa sp. pseudocyst extract), group 2 (white Kudoa sp. pseudocyst extract). Specific IgE levels were measured by ELISA. IgE detected in both groups 1 and 2 showed the possible allergenic nature of some of the components of the parasitic extracts.KEY WORDS : antigen, ELISA, IgE, Kudoa, Myxosporea, pseudocyst T he majority of Kudoa species infect the somatic muscle of marine and estuarine fish establishing cysts, which contain many spores. As the para site grows, it produces proteolytic enzymes (Patashnik et al., 1982; Tsuyuki et al., 1982) that break down the filaments of the muscle fibre (Stehr & Whitaker, 1986).While the parasite is within a muscle fibre, it is unde tected by the host's immunological system. It is during this stage when the parasite contains many developing and mature spores that the infected fibres have a white appearance. As the parasite grows, it breaks the sarcolemma and the host recognizes the presence of the parasite (Moran et al., 1999). Then, there is a rapid development of a fibroblast layer around the parasite (Morado & Sparks, 1986; Stehr & Whitaker, 1986) and the cyst, more properly, pseudocyst, quickly acquires a black appearance. However, the process of resorption is slower than that of the development of