Analysis of mitochondrial DNA variability and genetic structure in populations of New World screwworm flies (Diptera: Calliphoridae) from Uruguay.

The New Word screwworm, Cochliomyia hominivorax (Coquerel 1858) (Diptera: Calliphoridae), is one of the most important insect pests of livestock in the Neotropical region. In this work, polymerase chain reaction-restriction fragment length polymorphism of mitochondrial DNA (mtDNA) was used to study the diversity and population structure of seven geographically distinct populations of C. hominivorax from most of the important livestock areas in Uruguay. The control region (A+T/12S) and subunits 1 and 2 of cytochrome oxidase (cox1/cox2) were amplified and digested with restriction endonucleases. Nine haplotypes were observed among the populations sampled. The mean nucleotide diversity and the haplotype diversity indicated high mtDNA variability in this species. The similarity index, average nucleotide divergence, and analysis of molecular variance results showed no evidence of subpopulation differentiation, indicating that the C. hominivorax populations of Uruguay form a single panmitic population. The distribution pattern of the genetic variation in natural populations of C. hominivorax and the implications of these results for establishing control program are discussed.

Humoral immune response against fasciola hepatica in bovines: primary characterization of protection induced by irradiated metacercariae

There is an increasing awareness of fasciolosis as an important human and veterinary disease. In order to study the humoral inmune response of bovines, 5-month old calves were experimentally inmunized using 1000 ç irradiated metacercariae per animal, and challenged six weeks later with 500 normal ones per calf. Profiles of antibody responses of non inmunized animals following challenge, measured by ELISA, using both excretion/secretion ans somatic antigens, showed a sharp increase in antibody titres in the first 3 weeks post-infection which were maintained throughout the infection. Animals which instead were inmunized with inactivated parasites had similar antibody responses, but the antibody titres were higher. No booster effect was observed when these inmunized animals were challenger. Result of western blot analysis are consistent with these observations: antibodies against high molecular weight parasite-specific bands, ranging from 72,5 to 40 KD, appeared in week 2 PI in inmunized animals, and were mantained throughout infection, importanfly, inmunization resulted in a 84,2 percent reduction in parasite burden, indicating that high circulating antibody titres against these antigens probably are involved in a protective response. The results presented here indicate that, irradiated metacercariae of fasciola hepatica can be used as useful tool to generate a normal antigenic stimulus for the development of circulation antibodies, and toidentify antigens invloved in triggering a protective inmune response