E. Abollo et al., Hepatic coccidiosis of the blue whiting, Micromesistius poutassou (Risso),and horse mackerel, Trachurus trachurus (L.), from Galician waters, J FISH DIS, 24(6), 2001, pp. 335-343
The aetiology, epidemiology and pathology of coccidiosis in commercially-ex
ploited populations of Micromesistius poutassou and Trachurus trachurus fro
m Galician waters were investigated. Sporogonic stages of Goussia clupearum
and G. cruciata were found in the liver. Although the descriptive statisti
cs of Goussia infrapopulations and demographic infection values were always
higher in M. poutassou than in T. trachurus, parasite distribution was hig
hly skewed for both coccidian species. In both fish species, the number of
oocysts showed a similar cumulative effect as parasite counts increased wit
h increasing length and weight of fish, but did not change with host sex or
sexual maturity. Pathological changes in infected liver parenchyma of both
species were moderate (in T trachurus) to severe (in M. poutassou), with g
reatly reduced livers in the most heavily infected fish. Large areas of liv
er tissue were replaced with oocysts. Host response to infection included t
he formation of a fibrous capsule prior to infiltration by melanin and lymp
hocytes. Although post-recruit individuals of both fish species apparently
tolerate a severe infection, there was statistical evidence of a serious co
ntribution by the parasite to poor body condition in M. poutassou shown by
changes in the hepatosomatic and K-Fulton indices and in the length-to-weig
ht relationship.