Characterization of development-related genes for the cestode Bothriocephalus acheilognathi

Differential gene expression of mature and immature Bothriocephalus acheilognathi cestodes was analyzed using the suppression subtractive hybridization technique. Five mature-associated cDNAs were isolated and characterized. Virtual Northern blot and RT-PCR analyses confirmed that four of the five genes were up-regulated in mature parasites. The sequence analysis revealed that one gene encoded the structural protein chorion precursor, and that three encoded functional proteins homologous to yolk ferritin, sodium/hydrogen exchanger and muscin-like protein. Another gene appeared to be specific to B. acheilognathi, encoding a putative metal-bound protein. Although results obtained in the present study are preliminary, the information about the five genes may provide clues for further investigation on the decline in parasite numbers during the maturation of B. acheilognathi.

Genetic differentiation in populations of the cestode Bothriocephalus acheilognathi (Cestoda, Pseudophyllidea) as revealed by eight microsatellite markers

The genetic structure of populations of the fish cestode, Bothriocephalus acheilognathi collected from Bailianhe Reservoir (BLH), Changshou (CSH) and Liangzi (LZH) Lakes was investigated by using 8 microsatellite loci. A total of 108 adult worms were genotyped at each of the 8 loci. For the 3 populations, the mean number of alleles per locus ranged from 2.38 to 5.5, and the mean expected heterozygosity ranged from 0.432 to 0.559. The average polymorphic information content (PIC) was from 0.384 to 0.492. The significant F-is values indicated non-random mating within LZH and BLH populations. On the other hand, when samples were further classified into subpopulations at the level of host fish species, no or little heterozygote deficiency was detected at most loci, showing that cross-fertilization, predominantly, but not exclusively, must have occurred within the subpopulations. Microsatellite markers also revealed an unexpected high level of genetic differentiation, as measured by R-st and N-m values or by deltau(2) genetic distance among subpopulations from different hosts. Factors influencing the population genetic structure and the parasite host specificity are discussed.

Antibody response of carp, Cyprinus carpio to the cestode, Bothriocephalus acheilognathi

The humoral antibody response and the number of pronephric antibody-secreting cells were examined in naturally Bothriocephalus acheilognathi-infected carp. Cyprinus carpio, and in those injected intraperitoneally with an extract of the cestode. In the extract-injected fish, specific antibody was detected 3 weeks after a second injection given 2 weeks after the primary injection, and antibody levels persisted for more than 200 days. A third injection also enhanced the antibody level in the extract-injected carp. The numbers of antibody-secreting cells were significantly higher in carp injected 3 times with the extract than in the control. In naturally-infected fish, the serum antibody levels and the number of pronephric antibody-secreting cells were higher in infected fish than in uninfected individuals although this difference was not statistically significant. The relevance of these results to immune protection against infection is discussed.

Effects of Bothriocephalus acheilognathi on the polarization response of pronephric leucocytes of carp, Cyprinus carpio

An in vitro assay was used to examine the effect of Bothriocephalus acheilognathi Yamaguti, 1934 (Cestoda: Pseudophyllidea) on the polarization response of pronephric leucocytes of carp, Cyprinus carpio. Leucocytes, isolated from naive, naturally-infected fish and carp injected intraperitoneally with cestode extracts, were exposed to parasite extracts (protein concentrations 0-10.0 mu g ml(-1)), for up to 24 h in the presence or absence of carp serum. In general, polarization responses of the pronephric leucocytes, primarily neutrophils and eosinophils, increased with incubation time although there was no significant difference in the response induced by the different protein concentrations. Differences in the polarization response were, however, observed in naive, naturally infected and injected fish and the cells responded differently in the presence and absence of carp serum. In the absence of carp serum the polarization response of pronephric leucocytes in vitro was significantly reduced with cells obtained from injected and naturally infected fish compared with those obtained from naive carp. This suppression of leucocyte migration was however reduced by the addition of carp serum to the in vitro system. The role of this interaction between the possible suppression of polarization induced by the parasite and stimulation by serum is discussed.

Occurrence of Bothriocephalus acheilognathi in cyprinid fish from three lakes in the flood plain of the Yangtze River, China

Cyprinid fish, Hemiculter leucisculus, Cultrichthys erythropterus and Culter dabryi, were sampled from Liangzi, Honghu and Tangxun lakes in the flood plain of the Yangtze River. The cestode Bothriocephalus acheilognathi Yamaguti, 1934 was found in the 3 lakes, but C. erythropterus sampled from Liangzi lake was found uninfected due probably to the small sample size. Findings of the cestode in the 3 lakes represent the first record of the parasite in the flood plain of the Yangtze River, indicating that B. acheilognathi may be distributed much wider in China than previously recognized.