Insects are viewed by most as little nuisances that are sometimes associated with disgust and even fear. In Chapman University’s 2018 Survey on American Fears, almost 23% of respondents said that they were “afraid” or “very afraid” of insects and/or spiders (Chapman University, 2018). That is more than the number of people who feared being murdered by someone whom they know and is only slightly less than those who feared death.
Historically, there has been a lack of interest in entomotherapy—the use of insects as medicine—by the pharmaceutical industry. This is likely due to a variety of reasons, including negative public perception, high production costs, and inadequate bioengineering technology to turn low-volume insect products into wide-scale modern medicines. In reality, entomotherapy has been practiced around the world for thousands of years; for example, physicians have treated arthritis with ant venom, removed warts with the defensive secretions from the blister beetle, and utilized anticlotting agents from horsefly salivary glands (Tang et al, 2014; Puerto Galvis et al, 2013; Ratcliff et al, 2011). However, a recent entomotherapy review paper reported that more than 100 small-molecule isolates with bioactivity have been discovered in insects over the past several years (Yan et al, 2018). This might be the beginning of a paradigm shift as we continue to see a rise in antibiotic-resistant bacteria and fewer ways to treat them.
One commonly studied medicinal insect happens to be of the larvae of Lucilia sericata, otherwise known as the maggot. When you first think of these squirmy, slimy, white creatures, your mind likely goes straight to horror movies and gore flicks. But, although it may sound like ancient care, maggot biotherapy has been used for thousands of years and is still being used to treat non-healing diabetic foot wounds and chronic ulcers (Ratcliff et al, 2011). Maggots are known to possess many functional properties, including necrotic tissue debridement; anti-microbial, anti-inflammatory, anti-tumor, and anti-atherosclerosis activities; biofilm disruption; angiogenesis promotion; and tissue repair via extracellular matrix remodeling and induction of fibroblast migration and proliferation (Ratcliff et al, 2014).
Ocular Surface Treatment
So what do maggots have to do with the ocular surface? Researchers from the University of Houston College of Optometry and Northumbria University in the United Kingdom are seeking to answer whether medicinal maggot secretions can someday be used therapeutically to treat ocular surface disease (McDermott et al, 2019). They collected secretions from the Phaenicia sericata larvae for in-vitro scratch assay experiments. They found that maggot secretions enhanced wound closure of telomerase-modified human corneal epithelial cells compared to controls after only 24 hours. Interestingly, when cells were treated with agents that promoted expression of inflammatory cytokines (including IL-8), maggot secretions reduced expression in pre-treatment, co-treatment, and post-treatment conditions. Even more notably, in-vivo experiments were conducted in which 12 of 13 mouse corneas healed within 24 hours compared to only 50% of vehicle-treated mice.
Although there is a long way to go, accumulating evidence that maggot secretions can enhance the entire wound healing process and kill bacteria, including antibiotic-resistant strains such as methicillin-resistant Staphylococcus aureus (MRSA) (Bexfield et al, 2004), and recent studies indicating potential ophthalmic use, there might just be a possible future for maggots in the treatment of ocular surface disease. CLS
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