Abstract
BackgroundThe mite Psoroptes cuniculi is a common worldwide ectoparasite and the most frequently found in rabbit farms. It causes significant economic losses on commercial rabbit breeding associated with poor leather quality, reduced conception rates, weight loss, poor growth and death. Several strategies have been proposed for the treatment of mange caused by this mite, ranging from the use of acaricides, entomopathogenic fungi, essential oils and vaccines. However, therapy and control of both human scabies and animal mange are still based mainly on the use of drugs and chemicals such as ivermectin, which involves disadvantages including genotoxic and cytotoxic effects, resistance and environmental damage. Bacillus thuringiensis is a bacterium, innocuous for human being, domestic animals and plants that produces highly biodegradable proteins, and has been used worldwide for biological control. The aim of this work was to find an alternative treatment based on biological control for scabies caused by Psoroptes cuniculi, using protein extracts from strains of Bacillus thuringiensis.MethodsP. cuniculi mites were obtained from naturally infected New Zealand rabbits, and different doses of protein from B. thuringiensis were added to the mites. We measured mortality and obtained the median lethal concentration and median lethal times. For histological analysis, the mites were fixed in 10 % formalin, processed according to the paraffin embedded tissue technique. Sections were stained with hematoxylin-eosin to observe the general histological structure.ResultsWe report here for the first time evidence about the in vitro acaricidal effect caused by the strain GP532 of B. thuringiensis on the mite Psoroptes cuniculi, with an LC50 of 1.3 mg/ml and a LT50 of 68 h. Histological alterations caused by B. thuringiensis on this mite, included the presence of dilated intercellular spaces in the basal membrane, membrane detachment of the peritrophic matrix and morphological alterations in columnar cells of the intestine.ConclusionsSince this mite is an obligate ectoparasite that affects rabbits, goats, horses, cows and sheep, B. thuringiensis protein extracts are proposed as a potential treatment for biological control of mange in farm animals.
Highlights
The mite Psoroptes cuniculi is a common worldwide ectoparasite and the most frequently found in rabbit farms
We report that the acaricidal effect of B. thuringiensis protein extracts is by producing histological alterations on the gut of the mite
Production of spore-crystal proteins and in vitro bioassays To analyze the acaricidal effect of total protein extracts obtained from 13 strains of B. thuringiensis, we soaked P. cuniculi mites in a solution with 1 mg/mL of total protein for 60 s (Fig. 1)
Summary
The mite Psoroptes cuniculi is a common worldwide ectoparasite and the most frequently found in rabbit farms It causes significant economic losses on commercial rabbit breeding associated with poor leather quality, reduced conception rates, weight loss, poor growth and death. Therapy and control of both human scabies and animal mange are still based mainly on the use of drugs and chemicals such as ivermectin, which involves disadvantages including genotoxic and cytotoxic effects, resistance and environmental damage. P. cuniculi infestation can cause considerable weight loss, less favorable feed conversion rates, vestibular dysfunction, and meningitis, frequently complicated by secondary bacterial infections [2] It causes significant economic losses associated with poor leather quality, reduced conception rates, weight loss, poor growth and death [3]. These facts associated with the interest in the consumption of products ensuring good sanitary quality, hygiene, and proper handling have lead research efforts to discover new effective compounds
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