The effect of treatment with eprinomectin on lungworms at early patency on the development of immunity in young cattle.
An experiment was carried out to study the effect of topical application of eprinomectin at early patency on the build up of infection and development of protection against Dictyocaulus viviparus in young cattle. Three groups of six calves were used and parasitological and blood variables were monitored at weekly intervals throughout the trial. At the start of the experiment calves in groups A and B were experimentally inoculated with 100 D. viviparus infective third-stage larvae (L3) for five consecutive days, whereas calves in group C served as uninfected controls. The calves in group A were each treated with eprinomectin (0.5mg/kg bodyweight) in a pour-on formulation at early patency at day 24 post the first inoculation, whereas the calves in groups B and C were left untreated. Seven weeks following anthelmintic treatment all groups were challenged with 1500 L3. Another 4 weeks later the animals were sacrificed and established worms in the lungs were counted. Moderate transient signs of lungworm disease occurred both in groups A and B. However, group B calves were found to be about 8 times more resistant than those in group A, whereas the naive infection controls in Group C was found to be about 35 times more susceptible to infection. Also the ELISA values showed that the course of infection was different between experimental groups. The eosinophil counts prior to and at the time of slaughter indicate that immunity was involved in the protection and the response was correlated with previous exposure and worm load. Weight gains differed significantly, but only between groups A and C and between groups B and C that on an average were approximately 13kg heavier at the termination of the experiment. It was concluded that eprinomectin was effective against established adult lungworms. However, the untreated calves (group B) developed a more marked resistance to lungworms compared to those that were subjected to anthelmintic treatment at early patency (group A). On the other hand, the cumulative number of excreted larvae was on an average 43 times higher in group B as compared to group A. Consequently, infected calves that remain out on pasture should be treated. This will restrain transmission of the parasite despite the fact that immunity is deteriorated.
Höglund
Johan
J
Department of Parasitology (SWEPAR), National Veterinary Institute and Swedish University of Agricultural Sciences, 751 89, Uppsala, Sweden. johan.hoglund@sva.se
Gånheim
Charina
C
Alenius
Stefan
S
D000818:Animals; D000871:Anthelmintics / Q000494:pharmacology / Q000627:therapeutic use*; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy* / Q000276:immunology; D004021:Dictyocaulus / Q000187:drug effects / Q000254:growth & development / Q000276:immunology; D004022:Dictyocaulus Infections / Q000188:drug therapy* / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D004804:Eosinophils / Q000276:immunology; D005243:Feces / Q000469:parasitology; D007110:Immunity, Active / Q000187:drug effects; D007074:Immunoglobulin G / Q000097:blood; D007559:Ivermectin / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use*; D007814:Larva / Q000187:drug effects / Q000254:growth & development; D007958:Leukocyte Count / Q000662:veterinary; D008297:Male; D012008:Recurrence; D015430:Weight Gain
D000871:Anthelmintics; D007074:Immunoglobulin G; D007559:Ivermectin; C101434:eprinomectin