Fitness cost of malathion resistance in Egyptian Culex pipiens populations.

The extensive use of insecticides in agriculture and public health has resulted in the rapid development of insecticide resistance in mosquito populations. Therefore, in this study, we aimed to evaluate insecticide resistance costs on the fitness of Culex pipiens. Two Cx. pipiens field populations (Beheira malathion-resistant and Gharbia malathion-susceptible) were compared to the reference (sensitive) population. The biochemical composition and expression of four genes relevant to insecticide resistance were estimated in third instar larvae. Adult survival, female fecundity and egg hatchability were also determined. As per our findings, it was found that the total protein and carbohydrate contents in Beheira malathion-resistant larvae were significantly lower than that in the reference larvae. Beheira malathion-resistant larvae had higher phenoloxidase (PO) specific activity than the reference population. In terms of the relevant genes, only cytochrome P450 (CYP6F1) expression showed elevated levels in the Gharbia malathion-susceptible population compared to the Beheira malathion-resistant population. In esterases (Estα and Estß) and glutathione S-transferase, the tested populations did not show any significant differences. Compared to the reference mosquito population, Gharbia malathion-susceptible Cx. pipiens males exhibited significantly longer median survival. Female fecundity and hatchability showed nonsignificant differences among the populations tested. In conclusion, malathion resistance can induce lower protein and carbohydrate contents, but higher PO activity in larvae.

Assessment of the susceptibility status of Aedes aegypti (Diptera: Culicidae) populations to pyriproxyfen and malathion in a nation-wide monitoring of insecticide resistance performed in Brazil from 2017 to 2018.

BACKGROUND: Chemical mosquito control using malathion has been applied in Brazil since 1985. To obtain chemical control effectiveness, vector susceptibility insecticide monitoring is required. This study aimed to describe bioassay standardizations and determine the susceptibility profile of Ae. aegypti populations to malathion and pyriproxyfen, used on a national scale in Brazil between 2017 and 2018, and discuss the observed impacts in arbovirus control. METHODS: The diagnostic-doses (DD) of pyriproxyfen and malathion were determined as the double of adult emergence inhibition (EI) and lethal doses for 99% of the Rockefeller reference strain, respectively. To monitor natural populations, sampling was performed in 132 Brazilian cities, using egg traps. Colonies were raised in the laboratory for one or two generations (F1 or F2) and submitted to susceptibility tests, where larvae were exposed to the pyriproxyfen DD (0.03 µg/l) and adults, to the malathion DD determined in the present study (20 µg), in addition to the one established by the World Health Organization (WHO) DD (50 µg) in a bottle assay. Dose-response (DR) bioassays with pyriproxyfen were performed on populations that did not achieve 98% EI in the DD assays. RESULTS: Susceptibility alterations to pyriproxyfen were recorded in six (4.5%) Ae. aegypti populations from the states of Bahia and Ceará, with Resistance Ratios (RR95) ranging from 1.51 to 3.58. Concerning malathion, 73 (55.3%) populations distributed throughout the country were resistant when exposed to the local DD 20 µg/bottle. On the other hand, no population was resistant, and only 10 (7.6%) populations in eight states were considered as exhibiting decreased susceptibility (mortality ratios between 90 and 98%) when exposed to the WHO DD (50 µg/bottle). CONCLUSIONS: The feasibility of conducting an insecticide resistance monitoring action on a nation-wide scale was confirmed herein, employing standardized and strongly coordinated sampling methods and laboratory bioassays. Brazilian Ae. aegypti populations exhibiting decreased susceptibility to pyriproxyfen were identified. The local DD for malathion was more sensitive than the WHO DD for early decreased susceptibility detection.

Survey assessment on pediatricians' attitudes on head lice management.

BACKGROUND: Pediculosis capitis is a worldwide health problem. One of the most important factor in effective head lice eradication is to ensure that infestation is adequately recognized and treated. Our survey investigated the knowledge and practice among primary care Italian pediatricians regarding to the prevention and treatment of head lice. METHODS: The questionnaire was distributed to all the pediatricians registered at the Annual Congress of Practice in Pediatrics held in Florence, Italy, November 11-12, 2011. It includes 10 questions in a multiple choice format, and one answer for each question was provided. The questionnaire was conceived by pediatricians at the Infectious Disease Unit of the Department of Science for the Health of Woman and Child, University of Florence. Questions were designed according to the guidelines by the Italian Pediatric Society (SIP), and international guidelines, such as the Centers for Disease Control and Prevention (CDC), and the American Academy of Pediatrics (AAP). RESULTS: Overall, 364/600 pediatricians (60.7% of physicians registered to the Congress) returned the questionnaire. The majority of them (232/364; 63,7%) believe that parents consult their primary care pediatrician only after the failure of other "remedies". Mostly, they prescribe Malathion (116/364, 31,8%) as first line treatment. Two-hundred-fourty-three (66.7%) of participants consider creams, foams and gels the most effective formulations. Two-hundred-sixty-two of pediatricians interviewed (72.0%) suggest to repeat the treatment after one week, 37/364 (10.2%) after two weeks. The majority of the pediatricians interviewed reported that recurrences occur in less than 30% of cases (279/364; 76,6%). In their own opinion, most of recurrences are the consequence of a reinfestation in the community (259/264; 77%). Three-hundred-thirty-four (91.7%) of them have never prescribed oral therapy for the treatment of head lice. Finally, 289/364 (79.4%) pediatricians believe that no product is effective for prevention. CONCLUSIONS: This is the first study that investigates the clinical practice of family pediatricians about the management and treatment of head lice globally, the Italian pediatricians surveyed proved to be quite informed on the head lice management. However, even in a country where pediatric assistance is free for everybody, a considerable proportion of parents do not seek advice to their own family pediatrician. Therefore, educations of parents, other than continuous updating of pediatricians, may contribute to a better management of head lice in the community.

Assessment of susceptibility of the poultry red mite Dermanyssus gallinae (Acari: Dermanyssidae) to some acaricides using an adapted filter paper based bioassay.

A previously described bioassay was modified to assess the response of the poultry red mite, an important ectoparasite of fowl, to a selected group of acaricides. The adapted bioassay is simple to use, escape-proof and provides data that can be subjected to probit analysis. The reproducibility of the method was assessed by three tests with alpha-cypermethrin against a reference strain, which produced dose-response lines that did not differ significantly (chi(2)=1.39, 2 d.f., p=0.50), and had a derived common slope of 1.89. In addition, a limited evaluation study enabled assessment of response to commercial formulations of bifenthrin, bifenthrin+malathion and cypermethrin by field populations of the poultry red mite.