Can Organophosphates and Carbamates Cause Synergisms by Inhibiting Esterases Responsible for Biotransformation of Pyrethroids?

Hydrolysis catalyzed by general esterases (GEs) is the most efficient route for hydrolyzation of pyrethroid insecticides. Organophosphate (OP) and carbamate (CB) insecticides are known to inhibit GEs in addition to acetylcholinesterase (AChE), which is their main target. We hypothesize that synergies can be induced by OPs and CBs when mixed with pyrethroids, due to their inhibition of GE-dependent detoxification of pyrethroids. To test this hypothesis, we conducted mixture toxicity experiments with Daphnia magna using α-cypermethrin (α-cyp) in combination with the noninsecticidal OP tetraisopropyl pyrophosphoramide (iso-OMPA) and five AChE inhibitors diazinon, chlorpyrifos, chlorfenviphos, parathion, and aldicarb. In addition, the in vivo GE activity inhibition was measured for all compounds. Up to 10-fold synergy was found between α-cyp and iso-OMPA, and the degree of synergy correlated linearly with the inhibition of the GE activity. No synergy, however, was found in any of the insecticide mixtures nor was the GE activity inhibited within the nonlethal concentration range tested. It was concluded that the effect of the insecticides on AChE occurred at lower concentrations than their effect on GEs, making the daphnids become immobilized before any synergistic effects on mortality could be observed. The implications of the findings are discussed from a risk assessment perspective.

El resfriado común: revisión de su manejo habitual en las consultas / Common cold: review of its usual management in Primary Care

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Miasis ocular: el misterio es microscópico / Ocular myiasis: the mystery is microscopic

La miasis ocular es la invasión del órgano ocular y anejos por larvas de insectos que produce dolor, ardor, picazón y enrojecimiento uniocular de inicio abrupto acompañado de sensación de cuerpo extraño en movimiento. Las larvas se acantonan y reproducen invadiendo el tejido progresivamente. Mediante un caso clínico, presentamos los procedimientos diagnósticos y terapéuticos a realizar. Se trata de un agricultor de 56 años que acude a urgencias por prurito y sensación de ocupación en el ojo derecho de 24 horas de evolución sin irritación conjuntival, ni alteraciones visuales, ni limitación motora y el test de fluoresceína fue negativo. Tras lavarlo se evidencian helmintos en el espacio palpebral que más tarde serán identificados como larvas de mosca. Con antibiótico local profiláctico, analgésico tópico y revisiones periódicas en Oftalmología para su arrastre manual se consiguió la recuperación completa. No precisó de tratamiento antiparasitario pues no se objetivó lesión o problema ocular. La miasis es una patología infrecuente que suele confundirse con una conjuntivitis alérgica o viral. Las medidas higiénicas son imprescindibles para prevenirlas como son la limpieza del entorno, la buena higiene personal, la provisión de saneamiento básico y educación sanitaria en el medio rural

Ocular myiasis is the infestation of the eye and adnexa by insect larvae that produces pain, burning, itching and uniocular redness of abrupt onset accompanied by a moving foreign body sensation. The larvae settle and reproduce invading the tissue progressively. Through a clinical case, we present the diagnostic and therapeutic procedures to be performed. This is the case of a 56-year-old farmer who goes to the emergency room for pruritus and foreign body sensation in the right eye for 24 hours after onset without conjunctival irritation, visual disturbances, or limited movement, and with negative fluorescein test. After washing, helminths are evident in the palpebral space, whichwill later be identified as fly larvae. With local prophylactic antibiotics, topical analgesics and periodic control visits to Ophthalmology for manual removal, complete recovery was achieved. He did not need antiparasitic treatment because no eye injury or problem was observed. Myiasis is an infrequent pathology that is often confused with allergic or viral conjunctivitis. Hygiene measures are essential to prevent them, such as cleaning the environment, a good personal hygiene, the provision of basic sanitation and health education in rural areas