Ex vivo effectiveness of French over-the-counter products against head lice (Pediculus humanus capitis De Geer, 1778)

Abstract

Head lice infestation is still a public health problem worldwide, with an intracountry and intercountry prevalence variation of 0.7 to 59%. There is a large variety of over-the-counter anti-louse products, but their efficacy is not always well assessed. Our objective was to test the pediculicidal and ovicidal efficacy of 21 over-the-counter head louse products, available in France during the period of 2008 to 2012. We tested children living in Tours City in central France and visiting preschools, primary schools, kindergarten, camps, and child care facilities, as well as children in their family houses, and were examined for the presence of lice. The products were collected from randomly selected pharmacies by covert investigators and then tested in the laboratory on an ex vivo sample of head lice and their eggs, collected from the hair of infested children. Living lice and unharmed eggs were collected from the scalps of 3-12 years old. The laboratory conditions for ex vivo testing mimicked the manufacturers' instructions for exposure time and application method. In 21 runs, 3919 living lice and 4321 undamaged living eggs were collected from the scalp of over 400 children. The 21 products were classified in three groups: 6 products in a group of potentially 100% pediculicidal activity and potentially 100% ovicidal activity, 8 products in a group of potentially 100% pediculicidal activity but insufficient ovicidal activity (including 2 products with claims of single application treatment), and 7 products in a group of insufficient pediculicidal activity and ovicidal activity. The pharmaceutical market for head lice products in France is swamped with poorly tested and ineffective products. Rigorous efficacy testing preregistration and periodic screening and testing of effectiveness in the post-registration period should be endorsed by the health authorities.

Novel polymeric micelles for insect pest control: encapsulation of essential oil monoterpenes inside a triblock copolymer shell for head lice control

“…The time for measurement of affected lice in a bioassay should consider the recovering of insects after the exposure treatment (Combescot-Lang et al, 2015). Thus, we considered 7 h after treatment as the observational reference period reliable to estimate pediculicidal effectiveness.…”

“…Criterion of affected insects was according to Combescot-Lang et al (2015). Briefly, a louse was considered alive if it showed no symptoms or some abnormal movements and having difficulties turning over.…”

International recommendations for an effective control of head louse infestations

“…Because of the emergence and spread of lice that are insensitive (resistant) to the active ingredient and/or formulation, existing pediculicides should be re‐evaluated every 5 years in ex vivo tests or clinical trials to document the actual level of efficacy they elicit 26 …”

Diversity of mitochondrial genes and predominance of Clade B in different head lice populations in the northwest of Iran

“…Various prevalence levels of pediculosis have been reported globally during the past two decades [ 2 , 6 , 14 , 28 – 30 ]. Recent studies on pediculosis have revealed that among Asian countries, the number of studies are overrepresented in Turkey and Iran.…”