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Several factors influence the structure of parasite communities, which are important components of the biodiversity of various ecosystems. Some of these factors may be related to the environment and/or to the host. The present study evaluated the influence of host size and season on the structure of the metazoan parasite community of the brown-spotted grouper, Epinephelus chlorostigma. One hundred thirty-two fish were collected between March 2018 to February 2019 from the Red Sea, Saudi coast, Southern Saudi Arabia. Eight parasite species were recorded: one copepod (Sarcotaces sp.), one isopod (Argathona rhinoceros), two monogeneans (Pseudorhabdosynochus epinepheli and Megalocotyloides epinepheli), three digeneans (Prosorhynchus epinepheli, Helicometrina nimia, and Erilepturus hamati), and one nematode (Cucullanus epinepheli). The overall prevalence was 43.2% Digeneans were the most frequent parasite species and represented (50.55%) followed by monogeneans (45.05%), crustacean (3.42%), and nematode (0.98%) of the total individual parasites collected from 57 infected fish. Parasite community structure and species composition varied significantly among host size. Positive associations were found between infection parameters of parasite species and host size. Our results suggest that parasite infection parameters were affected by host size and season. Further long-term research is required to conclude the factors determining the structuring of the parasite community of E. chlorostigma.

The mosquito Aedes aegypti (Linnaeus) (Diptera: Culicidae) is a vector for several pathogens that affect human health worldwide. Therefore, mosquito control is the best approach to prevent disease outbreaks. In this milieu, it is preferable to evaluate the effectiveness of chemical pesticides at regular intervals to identify the most effective ones and use them during the outbreaks of diseases and spread of pests. Here, we aimed to study the toxicity of six pesticides, which are classified under two groups, namely pyrethroids and organophosphates, against A. aegypti mosquitoes to improve disease control in Saudi Arabia. Hortak was the most effective in larval mosquito control (LC50 = 0.0031 ppm), followed by Aquapal Super 20 EW (LC50 = 0.0389 ppm), whereas Solfac was the least effective (LC50 = 0.1119 ppm). In addition, the sensitivity of the tested larvae to Safrotin and Keen 600 EC was 8.1 and 58.9 times higher than that to Resfin-5, which was the least effective, respectively. Hortak and Safrotin exhibited the highest toxicity against the larvae of A. aegypti. Our findings confirm that the tested pesticides can be used in mosquito-control programs during epidemic outbreaks and emergency.

The house fly, Musca domestica (L.) has a worldwide distribution and acts as a source of nuisance and a common vector for several diseases in humans and livestock. The present study aimed to investigate the biological activity of plant extracts (Juniperus procera and Ficus palmata) along with their synthesized silver nanoparticle (AgNP) solutions against the second larval stage of house flies. Larval bioassay experiments were conducted using feeding and dipping methods at various concentrations. The synthesized silver nanoparticles were characterized by visual observation, UV–visible and FTIR spectroscopy. The results showed biochemical effects of the tested extracts on the treated larvae and different growth stages of the house fly. Using the feeding and dipping methods, the concentration required to inhibit 50% of the adult fly emergence (IC50 value) was 2.62% and 4.19% with J. procera and 0.71% and 1.29% with F. palmata, respectively. The crude extracts mixed with silver nanoparticles showed significantly decreased IC50 values at 1.09% and 1.23% for J. procera and 0.32% and 0.45% for F. palmata using the feeding and dipping methods, respectively. Further, the feeding method with both crude extracts showed about 1.60 and 1.80 times more effective control against the larval stages compared to that in case of the dipping method. In addition, the F. palmata extract was about 3.66 and 3.20‐fold more effective against flies compared to J. procera using the feeding and dipping method, respectively. Overall, this study suggests using of the tested extracts of plants as promising biological agents and safe options for sustainable pest management.

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