Dinotefuran-induced morphophysiological changes in semi-engorged females Rhipicephalus sanguineus Latreille, 1806 (Acari: Ixodidae) ticks: Ultra-structural evaluation

Histopathological effects of the fruit extract of Citrullus colocynthis on the ovary of the tick Hyalomma dromedarii

Hyalomma dromedarii is the predominant tick species parasitizing camels in Egypt which leads to mortalities in young animals that result in economic losses. It can transmit a lot of pathogens to animals and humans, such as the Crimean-Congo hemorrhagic fever virus, the Dhori virus, Kadam virus, Theileria annulata and spotted fever rickettsia. The continuous use of chemical acaricides has negative impact on the environment and almost led to acaricidal resistance, and hence the plant extracts represent alternative methods for controlling ticks. The present study was carried out to assess the histopathological effects on the ovary of fed female Hyalomma dromedarii following immersion in the ethanolic extract of fruits of Citrullus colocynthis (100 mg/mL). Light, scanning and transmission electron microscopy observations provided evidence that Citrullus colocynthis caused extensive damage to oocytes. Destruction of the internal organelles of oocytes, along with delay and/or inhibition of vitellogenesis were demonstrated. This is the first histological study that points to damage in H. dromedarii ovaries following treatment with the ethanolic extract of fruits of C. colocynthis. The data presented suggest that the plant extract affects the ovary either directly by entering the oocytes and/or indirectly by damaging the gut cells and digestion of blood that interfere with the development of oocytes, so it can be used as a promising agent for tick control.

Acaricidal and pathogenic effects of the entomopathogenic fungus Beauveria bassiana on engorged females of the fowl tick, Argas persicus (Argasidae)

This study examined the acaricidal, histopathological and genotoxic effects of the entomopathogenic fungus Beauveria bassiana on engorged females of the fowl tick, Argas persicus. The acaricidal effect of B. bassiana (at 10⁶-10¹⁰ conidia/mL) was concentration- and time-dependent. At 10⁶ conidia/mL, the accumulated mortality of treated females ranged from 3.33 ± 3.3 to 13.33 ± 3.3% over 21 days. However, the mortality was remarkably increased after the application of 10¹⁰ conidia/mL, ranging from 6.67 ± 3.3 to 80 ± 5.8%. Females treated with various conidial concentrations exhibited complete inhibition of oviposition. Light and electron microscopic examination of the ovary of engorged female ticks at 3, 6 and 9 days after treatment with 10⁷ conidia/mL revealed that the oocytes exhibited drastic changes that affected their growth and development. The overall damage observed in the ovary included loss of grape-like appearance, distortion of oocytes, cytoplasmic vacuolation, degeneration of organelles and myelin figure formation. Previtellogenic oocyte progression was completely inhibited as the vitellogenic phase was not observed. Random amplified polymorphic DNA (RAPD-PCR) and inter simple sequence repeat (ISSR) methods were used to assess the genotoxic effects of B. bassiana at 10⁷ conidia/mL on engorged female A. persicus over 3 weeks. The lowest percentage of genomic template stability was recorded in paralyzed ticks after 3 weeks. The study demonstrated the efficacy of B. bassiana as a biocontrol agent against A. persicus as it interfered with its reproduction, movement and viability and disrupted its normal tissue and DNA integrity.

Morphophysiological analysis of the salivary glands of Rhipicephalus sanguineus sensu lato (Acari: Ixodidae) exposed to ozonated water: A control strategy

The tick Rhipicephalus sanguineus sensu lato has great medical and veterinary importance, mainly because the ability to transmit many diseases, causing harm to pets but also risks to public health. The blood spoliation and transmission of pathogens occur because of the immunosuppressive action of these ticks' saliva, a potent mixture of bioactive substances that is secreted by the salivary glands, one of the organs responsible for their biological success, and hence the target of studies for their control. Ozone has promise for use as an alternative acaricide, due to its proven efficiency in controlling agricultural and food pests, besides posing no risk of environmental contamination or to animal and human health. Therefore, this study evaluated the acaricidal potential of exposure of females of R. sanguineus s.l. to ozonated water at many concentrations and analysed the morphophysiological alterations of the salivary glands, employing histological and light microscopic techniques. The results demonstrated that the ozonated water at the concentrations investigated caused severe alterations in the salivary glands, bringing a new perspective for control of R. sanguineus s.l., through an ecologically correct method due to the absence of harm to non-target organisms and the environment.