The effect of sublethal concentrations of deltamethrin and alphacypermethrin on the fecundity and development of Ixodes ricinus (Acari: Ixodidae) eggs and larvae.

Two pyrethroids, deltamethrin (D) and alphacypermethrin (AC), have been used as commercial products for tick control worldwide. However, the effects of sublethal doses of these compounds on various tick species and their developmental stages have not been fully explored yet, although such knowledge could contribute to a more effective application of both pyrethroids and simultaneous reduction of their costs and undesirable side effects, including the harmful impact on other organisms and environmental contamination. This study investigates the effect of sublethal concentrations of D and AC applied to engorged females on the fecundity, development of eggs and larvae, and the number of offspring in the Ixodes ricinus (L.) tick, which is the most important vector of tick-borne diseases of humans in Europe. After detachment from rabbit's skin, fully engorged I. ricinus females were treated with 20 µl of pyrethroid solutions at five concentrations from 0.01562 to 0.25% and kept at 28 °C and 75% relative humidity. The impact of the pyrethroids on maturation and development of eggs as well as development of larvae was assessed based on parameters of the preoviposition and oviposition periods and the course of embryogenesis and egg hatch. The investigations have shown that both tested acaricides reduce the reproductive rate in I. ricinus females by inhibition of egg development and disturb embryonic development and larval hatch. Females did not lay eggs at concentrations higher than 0.0625% AC and 0.125% D. The lower concentrations of both pyrethroids disturbed or inhibited the embryogenesis and egg hatch in I. ricinus.

The toxic effect of permethrin and cypermethrin on engorged Ixodes ricinus females.

INTRODUCTION: Ixodes ricinus tick is of great medical and veterinary importance and has a wide range of geographical distribution. The study presents the effect of permethrin (Per) and cypermethrin (CM) on engorged I. ricinus females. MATERIALS AND METHOD: The effect of perythroids studied on engorged I. ricinus females was assessed on the basis of the pre-oviposition and oviposition period. Remote effects of Per and CM application were assessed by investigation of the length and course of embryonic development and larval hatching from eggs laid by pyrethroid-treated females. Per (Copex WP) was used at doses of 0.78125-25.0 µg/1 specimen, and CM (Kordon 10WP) was applied at 0.3125-10.0 µg/1 specimen. Immediately after the feeding period, I. ricinus females were sprayed with 20 µl of a pyrethroid solution and kept at 28 °C and 75%RH. RESULTS: The experiments demonstrated that CM exerted a stronger toxic effect on I. ricinus females than Per. The lowest doses of CM doubled the length of the pre-oviposition period while its highest doses prolonged the period nearly three times compared with the control. The pyrethroids applied reduced the number and weight of eggs and changed the parameters of the oviposition process. Application of the tested pyrethroid doses led to disturbances in the embryonic development of I. ricinus, i.e. the development was prolonged, few normal larvae hatched, numerous eggs and embryos at various developmental stages died, and larval hatch was inhibited. CONCLUSIONS: Knowledge about the sensitivity of engorged females to different doses of the tested pyrethroids and the remote effects of their action can be used in practice for tick control among livestock animals, and the reduction of tick population abundance in the environment.

Comparison of the toxic effect of pyrethroids on Ixodes ricinus and Dermacentor reticulatus females.

INTRODUCTION: Despite the increased rates of infestations with I. ricinus (Ir) and D. reticulatus (Dr) ticks observed over the last decade, no effective control methods have been developed so far. The present study was focused on assessment of the action of pyrethroids on these both tick species. MATERIALS AND METHOD: The different doses of four pyrethroids, i.e. deltamethrin - D (K-Othrine), permethrin - P (Copex WP), cypermethrin - C (Kordon 10WP), and alphacypermethrin - AC (Alfasekt 5SC) were tested. The LD50 for each tested compound was also determined for both tick species. Unengorged and engorged (maintained on rabbit skin) tick females were sprayed with 20 ml of 0.01563-0.50% solutions of the tested preparations. RESULTS: The investigations showed that sensitivity of Ir and Dr to the tested pyrethroids, but the effects exerted by the different doses varied between both tick species and between engorged and unengorged females in these species. The strongest toxic effect on unengorged and engorged Ir and Dr females was exerted by D, whereas the effect of AC was weaker. The LD 50 (in µg/1 g b.w.) of D, AC, C, and P for unengorged Ir and Dr females was, respectively, 55.4 and 25.5, 105.2 and 48.5, 225.9 and 197.7, and 553.8 and 380.8. In the case of engorged Ir and Dr females, the LD50 of AC, D, C, and P reached a value of 0.9453 and 0.2310, 1.0428 and 1.3533, 3.489 and 6.5662, and 8.3955 and 7.3940, respectively. CONCLUSIONS: The differences between the effects of the tested pyrethroids and their different doses on Ir and Dr highlight the necessity for development of a strategy for control of the tick species in different regions, based on investigations of their sensitivity to chemical compounds.

Sensitivity to permethrin in a Dermacentor reticulatus population from eastern Poland in laboratory study.

BACKGROUND: The action of chemical compounds on the Palaearctic tick D. reticulatus (Fabricius) (Acari: Amblyomminae) has been poorly investigated so far. Therefore, the effects of application of permethrin on engorged D. reticulatus females have been assessed, and the survival rate for the different developmental stages of the tick species in its non-parasitic phase of the life cycle was determined upon application of the pyrethroid. METHODS: Each engorged D. reticulatus female, egg batch, unfed larvae (50 specimens), or unfed nymphs (10 specimens) were sprayed with 20 µl of 0.015625%- 0.250% solutions of a Coopex WP preparation, which corresponded to 0.78125- 12.5 µg of permethrin, respectively. The effect of permethrin in the preoviposition and oviposition periods was assessed based on the length of the egg development period, number of females capable of laying eggs, number and weight of eggs laid by the females, and indicators of female reproductive rate. Delayed effects of the action of the various permethrin doses were determined by quantitative and qualitative analysis of the course of embryonic development and larval hatch. The effect of permethrin on survival of the different tick stages was assessed at a temperature of 25°C and 90% RH 48 hours after application of permethrin to one to three day-old D. reticulatus eggs, seven to ten-day-old unfed larvae and nymphs. RESULTS: The investigations demonstrated that at the doses applied permethrin decreased the reproductive rate of females, but only at the dose of 6.25 µg/1 specimen was the mean number of laid eggs drastically reduced, which may result in a decrease in tick abundance already in the first generation. The embryonic development of the eggs laid by the females treated with 6.25 and 12.5 µg of permethrin/1 specimen was highly disturbed. Irrespective of the permethrin dose applied, all eggs died within 48 hours after application. 100% of unfed D. reticulatus larvae and nymphs died within 48 hours after application of permethrin doses of 6.25 µg/50 specimens and 12.5 µg/10 specimens, respectively. CONCLUSIONS: Permethrin can be recommended for D. reticulatus control, particularly in the case of tick resistance to other chemical substances.

Evaluation of the effect of various concentrations of selected pyrethroids on the development of Dermacentor reticulatus eggs and larvae.

The Palearctic three-host species Dermacentor reticulatus contributes to the circulation of numerous pathogens in the environment. Reduction of its abundance may therefore decrease the risk of tick-borne diseases in a given area. The aim of the study is to determine the effect of various concentrations of three pyrethroids--(D), cypermethrin (C), and alpha-cypermethrin (AC) on the development of D. reticulatus eggs and larvae. 217 engorged D. reticulatus females were examined in the investigations. After the feeding period, they were sprayed with 0.015625%, 0.03125%, 0.0625%, and 0.125% solutions of D, C, and AC, and kept at a temperature of 25 o C and 90% relative humidity throughout the preoviposition and oviposition periods. Eggs laid by females were kept in the same conditions until larval hatch. Based on the results obtained, parameters of the course of maturation and oviposition, as well as parameters of embryonic development, were determined. The investigations showed that the pyrethroids tested prolonged the egg maturation period, reduced the number and weight of eggs, and caused disturbances in embryogenesis in D. reticulatus. Upon treatment with as little as 0.015625% AC, larvae did not develop and all eggs died 1-2 days after oviposition. C led to a decreased percentage of normal larval hatch--31.96%, 15.51% and 12.5%, respectively, after using three increasing concentrations (control 98.15%), and a high rate of egg and embryo mortality. The least detrimental effect on the D. reticulatus maturation and embryonic periods was exerted by deltamethrin (82.74%, 84.37% and 16.80% of normal larvae in treatment with the three concentrations). Morphological anomalies were observed in larvae during the experimental period. AC appeared to have the most toxic effect during the maturity and egg development periods, while C exhibited lower toxicity. Application of these pyrethroids in engorged D. reticulatus females exerts distant effects that lead to substantial reduction of tick offspring abundance.

Less invasive posterior surgical approach for hip joint replacement--complications and limitations.

BACKGROUND: We attempted to analyse the difficulties and risk of complications associated with total hip replacement using a limited posterior approach and standard instrumentation. MATERIAL AND METHODS: A series of 85 consecutive cases (47 females and 38 males; age range 22-87 years; mean age: 65.6 +/- 10.4) of total hip replacement using a modified Gibson approach were analyzed prospectively. Bilateral surgery was performed in 7 patients. There were 44 non-cemented arthroplasties. Body mass index varied from 22 to 36 (body weight 78-104 kg) and the length of the operative wound varied from 6.5 to 14 cm (mean 9.8 +/- 1.3 cm). The wound was 14 centimeters long in six subjects with a BMI of 35-36. The procedure was performed in a lateral decubitus position using an appropriately limited posterior approach. After careful coagulation of blood vessels surrounding the base of the femoral head posteriorly, the obturator and gemelli tendons and the posterior part of the joint capsule were cut through as close to the femoral attachment (T) as possible. This made it possible to dislocate the joint posteriorly. Further stages of the procedure were performed in a typical manner, with special attention paid to the preservation of the tendon of the piriformis muscle. Continuity of the muscle was re-examined following the reposition of the artificial joint. RESULTS: Two injuries to the piriform tendon were observed. Persistent bleeding from vessels surrounding the femoral neck base occurred in 5 patients while in four others there was transient paresis of the peroneal muscles and dorsal extensors of the ipsilateral foot, probably caused by extension of the sciatic nerve. There was one oblique fracture of the proximal femoral shaft. We did not observe significant errors in postoperative joint geometry. Mean intraoperative blood loss was 400 ml. We did not note postoperative dislocations or infections. CONCLUSIONS: On the basis of our observations of a series of 85 patients, minimizing the extent of the posterior surgical approach for hip joint replacement seems an attractive alternative to the classical extensive technique. Our material reveals a relatively high incidence of transient paresis of the peroneal part of the sciatic nerve. The introduction of appropriate instrumentation and the accumulation of experience will certainly decrease the risk of extension of the sciatic nerve in the operative wound.