Efficacy of ethyl-4-bromophenyl carbamate on different Rhipicephalus microplus stages implanted in cattle.

The effect of ethyl-4-bromophenyl carbamate on different Rhipicephalus microplus stages implanted in cattle was evaluated using the pen test with infestation chambers. Twelve steers were distributed into four groups (n = 3), each with four chambers (12 chambers per group), where approximately 1,000 R. microplus larvae were placed in each chamber. The chambers of the first group were sprayed with a solution of ethyl-4-bromophenyl carbamate (0.668 mg/mL) on day 2 post-infestation (PI) (exposed larvae). The chambers of the second group were sprayed with the same solution on day 8 PI (exposed nymphs), and the chambers of the third group were sprayed on day 16 PI (exposed adults) with the same solution. The chambers of the fourth group were used as controls. The percentages of engorged females, egg laying, egg production and egg hatching were evaluated in all groups. The percentage of cumulative reduction of hatched larvae was 98.3, 96.1 and 94.4% when larvae, nymph and adult stages were treated, respectively. The average cumulative reduction of hatched larvae, considering the three treated stages, was 96.3%, whereby the reproductive potential of this tick was drastically reduced. In conclusion, ethyl-4-bromophenyl carbamate acted as an ixodicide (lethal effect) when larval stages were sprayed and as a growth regulator when nymphal and adult stages were sprayed. The sum of these effects had a direct impact on the efficacy of the product in the pen test, and future studies will indicate the potential use of this product for tick control.

Subclinical experimental infection with Taenia hydatigena in sheep is associated with production losses.

The effect of experimental infection by Taenia hydatigena metacestodes on different productive parameters in sheep was evaluated. Seventeen male Columbia lambs distributed in three groups were used. The lambs of the first group (n = 5) were orally inoculated with 1000 T. hydatigena eggs (low dose). The lambs of the second group (n = 5) were inoculated orally with all the eggs of the last proglottid of an adult cestode (high dose). The lambs of the third group (n = 7) only received a placebo and were used as a control group. All lambs were humanely euthanized at week 13 postinfection, and carcass yield and conformation were evaluated. The infection rates of the lambs from the high-dose infected group and the low-dose infected group were 100% and 40%, respectively, with a mean of 2.4 ± 0.6 and 1 ± 0.7 metacestodes of T. hydatigena in the abdominal cavity, respectively. In a first multivariate study (MANOVA) considering the under the curve (AUC) values of body condition, weight gain, and feed consumption, as well as the final feed conversion values, showed a highly significant (p < 0.0001) group effect (high dose/low dose/uninfected). In a second multivariate study (MANOVA) considering the AUC values of eosinophils blood count, packed cell volume and alkaline phosphatase showed a highly significant (p < 0.0001) group effect (high dose/low dose/uninfected). The increase in serum ALP is a consequence of liver damage that had a strong negative correlation (r = -0.63, p < 0.007) with the body condition of the lambs. Despite these findings, we did not observe obvious clinical manifestations in any of the infected lambs. In general, no differences (p > 0.1) were observed between the lambs of the control group and the lambs of the low-dose infected group in the parameters evaluated. The results of this study show that the infection of T. hydatigena metacestodes subclinically produces a decrease in productive efficiency, alterations of some hematological and biochemical values, and a slight deterioration in the general appearance of the infected lambs. The above aspects are rarely detected by most farmers, but they have a negative impact on the productivity of infected lambs.