Efficacy against sheep lice (Bovicola ovis) and fleece wetting of six shower dip preparations

Combined toxic effects of polyethylene microplastics and lambda-cyhalothrin on gut of zebrafish (Danio rerio)

Microplastics (MPs), which are prevalent and increasingly accumulating in aquatic environments. Other pollutants coexist with MPs in the water, such as pesticides, and may be carried or transferred to aquatic organisms, posing unpredictable ecological risks. This study sought to assess the adsorption of lambda-cyhalothrin (LCT) by virgin and aged polyethylene MPs (VPE and APE, respectively), and to examine their influence on LCT's toxicity in zebrafish, specifically regarding acute toxicity, oxidative stress, gut microbiota and immunity. The adsorption results showed that VPE and APE could adsorb LCT, with adsorption capacities of 34.4 mg∙g-1 and 39.0 mg∙g-1, respectively. Compared with LCT exposure alone, VPE and APE increased the acute toxicity of LCT to zebrafish. Additionally, exposure to LCT and PE-MPs alone can induce oxidative stress in the zebrafish gut, while combined exposure can exacerbate the oxidative stress response and intensify intestinal lipid peroxidation. Moreover, exposure to LCT or PE-MPs alone promotes inflammation, and combined exposure leads to downregulation of the myd88-nf-κb related gene expression, thus impacting intestinal immunity. Furthermore, exposure to APE increased LCT toxicity to zebrafish more than VPE. Meanwhile, exposure to PE-MPs and LCT alone or in combination has the potential to affect gut microbiota function and alter the abundance and diversity of the zebrafish gut flora. Collectively, the presence of PE-MPs may affect the toxicity of pesticides in zebrafish. The findings emphasize the importance of studying the interaction between MPs and pesticides in the aquatic environment.

Lambda-cyhalothrin affects swimming activity and physiological responses of Daphnia magna

λ-cyhalotrin is a pyrethroid pesticide used for protection of crops against various insect pests. Knowledge on behavioural and physiological responses of non-target organisms such as cladocerans is very limited. Daphnia is a sensitive organism commonly used in determination of ecotoxicological risk for various substances introduced to aquatic environment, however the main experimental endpoints used such as mortality or immobilisation may not be sufficient to evaluate subtle alterations in zooplankton. The aim of the present study was to evaluate swimming behaviour and physiological parameters of Daphnia magna exposed to λ-cyhalothrin (Karate Zeon 050 CS) at concentrations of 0.05, 0.5, 5 and 50 μg L^-1 for 2, 24 and 48 h. The results showed that λ-cyhalothrin affected D. magna swimming behaviour inducing a concentration-dependent inhibition of swimming track density, speed and turning ability. Depression of physiological parameters such as heart rate and thoracic limb activity was also noted. The results suggest that in natural conditions swimming behaviour and physiological endpoints of D. magna may be disturbed by environmental concentrations of λ-cyhalothrin leading to ecological consequences.

A field study on the efficacy of ivermectin via subcutaneous route against chewing lice (Bovicola caprae) infestation in naturally infested goats

Caprine pediculosis is an ectoparasitic disease of great concern among goat farmers in India. It may be caused by either sucking lice or chewing lice; the latter one results in severe skin lesions, leading to production loss. This study evaluated the effectiveness of the macrocytic lactone drug, ivermectin, administered via subcutaneous injection, against chewing lice Bovicola (Damalinia) caprae infestation in naturally infested goats. The study was conducted on 20 goats with severe B. caprae infestation. Animals of group A (n = 10) were treated using a single dose of ivermectin (200 µg/kg body weight) subcutaneously and animals of group B (n = 10) underwent placebo therapy using normal saline. The animals were examined on days 0, 3, 7, 14, 21, 28, 42 and 56 for lice counts. There was 100% elimination of lice in all animals of group A and effective protection from re-infection remained at least for 21 days. Considerable improvement in haematological parameters was also observed by day 21. Based on this study, ivermectin injected via a subcutaneous route can be used effectively for the therapeutic and prophylactic management of chewing lice infestation in goats maintained under an extensive grazing system.

Lice induced immuno-oxidative wreckage of goats

The present study aimed to evaluate the immuno-oxidative patho-biology of lice infestation in goats. Sixty goats were divided into five groups; sucking lice (Linognathus africanus) infested (Group 1, n=12), chewing lice (Bovicola caprae) infested-mild (Group 2, n=12), chewing lice (B. caprae) infested-moderate (Group 3, n=12), chewing lice (B. caprae) infested-severe (Group 4, n=12) and healthy control (Group 5, n=12). To assess the pathological changes, markers of oxidative stress (lipid peroxidation-LPO, reduced glutathione-GSH, superoxide dismutase-SOD, Catalase-CAT and total antioxidant capacity-TAC), the markers of immune status (Tumour necrosis factor alpha- TNF-α, Interleukin-10- IL-10, Transforming growth factor beta 1- TGF-β1, ratios of TNF-α/IL-10 and TNF-α/TGF-β1) and hemato-biochemical status were evaluated. Significant anemia, hypoglycemia, hypoproteinemia and hypoalbuminemia were observed in caprine pediculosis irrespective of the type of lice infested. Remarkably increased oxidative stress was observed in chewing lice infested goats and no significant changes in oxidative stress markers were observed in sucking lice infested goats. TGF-β mediated suppression of Th1 and Th2 immune responses was observed in sucking lice infested goats; whereas, a Th2 cytokine dominant inflammatory response was observed in chewing lice infested goats. From the present study, it may be concluded that sucking lice infestation produces remarkable immunosuppression and chewing lice infestation produces significant oxidative stress and inflammatory responses in goats.

Efficacy of flumethrin pour-on against Damalinia caprae of goats (Capra hircus)

Goats naturally infested with Damalinia caprae lice were used to evaluate the efficacy of flumethrin pour-on. The maximum load of lice infestation was detected in the neck region. The LC50 value of flumethrin pour-on against D. caprae was found to be 119.35 ppm and the 95% confidence limits were calculated to be 104.10 and 136.85 ppm. Flumethrin at the rate of 1 mg/kg body weight by pour-on application along the mid-dorsal line was found to be 100% effective in treating lice-infested goats compared with the control goats. The residual action of flumethrin was found to be at least 42 days during which period no apparent signs of any local or general adverse effects were observed. Based on these studies, it is suggested that flumethrin pour-on may be successfully used for both the prophylaxis and treatment of D. caprae infestation in goats and it is necessary to repeat the treatment after 42 days. The method of application is highly advantageous as it can be conveniently applied, even in animals with thick hair coat and during the winter months.

Further evidence that zinc sulphate compromises the efficacy of dipping treatments using diazinon to control sheep lice (Bovicola ovis)

OBJECTIVE

To compare the wettability and efficacy of diazinon dip wash made with and without the addition of zinc sulphate.

DESIGN

Field experiments using a shower and a plunge dip complemented by in-vitro wettability experiments.

PROCEDURE

A flock of infested sheep was divided into groups and treated in a shower dip with clear or cloudy dam water plus up to 1.5% zinc sulphate. Another infested line of sheep was treated using a plunge dip with nil or 1% zinc sulphate. In both experiments, wetting was assessed after dipping and louse counts were conducted for 9 months after treatment. Five in-vitro experiments compared the wettability of dip wash containing diazinon with up to 1.5% zinc sulphate added.

RESULTS

In the shower dipping experiment, live lice were found at 1 month after dipping in the cloudy water groups with 0.75%, 1.0% and 1.5% zinc sulphate and at 2 months in the 0.75% zinc sulphate group. No lice were found at subsequent inspections or at any time in the groups that were plunge dipped. Zinc sulphate decreased the amount of dip wash retained by wool staples in all in-vitro experiments (P < 0.05).

CONCLUSION

Zinc sulphate should be considered as a risk factor that could cause failure to eradicate a lice infestation. The risk can be overcome by ensuring that all sheep are saturated at dipping and that the dip wash, and any holding tanks, are agitated throughout the dipping event.

Settling of insecticide from dip wash mixed with dam water and zinc sulphate and used to control sheep lice (Bovicola ovis)

Insecticidal dipping fluid emulsions, mixed in vitro in dam water containing suspended clay particles and 1% w/v zinc sulphate, were analysed to determine rates of settling of diazinon, cyhalothrin and cypermethrin. Fifteen minutes after mixing, the concentration of the insecticides 5 cm below the surface had declined by 72.5%, 72.8% and 89.4%, respectively. On remixing, the concentration of insecticide in suspension was close to or greater than the initial concentration. In 2 trials, lice were eradicated from sheep showered with dip wash mixed in cloudy dam water to which 1% w/v of zinc sulphate was added. In 12 flock treatments in which 1000 to 2000 sheep were dipped with added zinc sulphate, the concentration of insecticide remained above the minimum lethal for susceptible strains of lice. However, lice were still present 6 months later in 8 of these flocks. When zinc sulphate is added to dip wash, agitation is needed to maintain the insecticide in suspension.