Assessing the Larvicidal Properties of Endemic Campeche, Mexico Plant Piper cordoncillo var. apazoteanum (Piperaceae) against Aedes aegypti (Diptera: Culicidae) Mosquitoes.

The research aims to investigate the mortality effect of essential oil from Piper cordoncillo var. apazoteanum, an endemic plant from Campeche, Mexico, on early second-instar Aedes aegypti larvae; it also aims to identify the volatile compounds present in the fresh leaves of the plant. To test the effectiveness of the essential oil, we followed World Health Organization Standard Procedures. Larvae were observed for 17 consecutive days after treatment to determine the mortality and growth-inhibitory effect exerted by the essential oil. The results showed that the essential oil was effective in controlling mosquito populations. At a concentration of 800 ppm, the oil achieved an effectiveness rate of 70.00 ± 8.16% after 24 h, increasing to 100.00 ± 0.01% mortality after 72 h. With a concentration of 400 ppm, the effectiveness was 98.33 ± 0.17% by the end of the experiment. Furthermore, the obtained results demonstrated that the LC50 value was 61.84 ± 6.79 ppm, while the LC90 value was 167.20 ± 11.49 ppm. Essential oil concentrations inhibited the growth of immature insect stages, with concentrations between 800-100 ppm demonstrating very high inhibitory activity, and the lowest concentration of 50 ppm showing high inhibitory activity. The study also identified 24 chemical compounds representing 86.71% of the volatile compound composition of the fresh leaves of P. cordoncillo; the most abundant compounds were Safrole, Caryophyllene oxide, E-Nerolidol, and Calarene epoxide. The method used to extract the volatile compounds, solvent-free microwave extraction (SFME), is a promising alternative to traditional methods that avoids the use of potentially harmful solvents, making it more ecologically friendly and potentially safer for professionals handling the extracted compounds. Overall, the study demonstrates the potential of P. cordoncillo essential oil as an effective means of controlling mosquito populations, and provides valuable information on the chemical composition of the plant.Moreover, our study is the first to report on the biological activity and chemical composition of P. cordoncillo worldwide.

Growth of the Black Soldier Fly Hermetia illucens (Diptera: Stratiomyidae) on Organic-Waste Residues and Its Application as Supplementary Diet for Nile Tilapia Oreochromis niloticus (Perciformes: Cichlidae).

The black soldier fly, Hermetia illucens (BSF, Diptera: Stratiomyidae) is an insect with high protein value and a potential feed agent for animals aimed for human consumption. The growth parameters of BSF larvae reared on four substrates-restaurant-waste, fruit-waste, fish-waste, and commercial tilapia food-for 41 days before processing for inclusion into Oreochromis niloticus (Perciformes: Cichlidae, Nile tilapia) commercial fry diets at 30% (70:30) were determined. On fly larvae, the food substrate based on restaurant waste yielded the greatest larval weight and length. BSF larvae fed a fish-waste diet showed the shortest developmental time. The fruit-waste diet induced the lowest weight and length in the fly larvae/pre-pupae (immature stage). The pre-pupal protein values were similar to commercial food. On fry-fish, the diets with pre-pupae grown on fish waste showed the greatest yields regarding weight (biomass), length, and nutritional content. These results suggest the BSF has the potential to be used in fish feed and provides an alternative for commercial cultivation.

Clinical study of Maggot therapy for Fournier's gangrene.

Fournier's Gangrene is a fulminating necrotizing fasciitis of the perineum and genitalia. Standard treatment involves immediate excision of all necrotic tissue, aggressive antibiotic coverage, and supportive medical care. Still, the infection is commonly fatal or disfiguring. Wound treatment with disinfected blowfly larvae (maggot debridement therapy or MDT) has been shown to be highly effective, with multiple studies demonstrating effective debridement, disinfection, and promotion of granulation tissue. MDT also has been associated with preservation of viable tissue and minimised blood loss. This report describes a prospective clinical study of MDT for Fournier's gangrene aimed to test the hypothesis that early use of maggots could decrease the number of surgical treatments required to treat Fournier's gangrene. Subjects were provided with one initial surgical excision, followed by debridement using only medical grade Lucilia sericata larvae. Only two subjects were enrolled, both diabetic men. Intensive care and culture-directed antimicrobial coverage were administered as usual. Maggot debridement was associated with the disappearance of necrotic tissue, control of infection and granulation tissue growth. In both subjects, wounds healed without requiring further surgical resection or anatomical reconstruction. Maggot therapy decreased the number of surgical procedures that otherwise would have been necessary, and led to favourable outcomes.

Asian Tiger Mosquito in Yucatan Peninsula: First Record of Aedes (Stegomyia) albopictus (Diptera: Culicidae) in Campeche, Mexico.

This report describes the presence of Aedes albopictus Skuse (Diptera: Culicidae) in Yucatan Peninsula and represents the first record of the Asian tiger invasive mosquito in Campeche State, southeastern Mexico. We collected specimens using 11,326 ovitraps put into houses of urban and rural areas, as part of the entomological surveillance by the local Ministry of Health from January 2019 to February 2020. We found Ae. albopictus in five of the 12 municipalities of Campeche (San Francisco de Campeche, Tenabo, Hecelchakán, Calkíni and Escárcega). We record 68 positive ovitraps and 226 Ae. albopictus larvae. This finding increases the number of mosquito species recorded in Campeche, Mexico, and possibly the potential for 22 arbovirus transmission.

Bactericidal Activity of Chrysomya rufifacies and Cochliomyia macellaria (Diptera: Calliphoridae) Larval Excretions-Secretions Against Staphylococcus aureus (Bacillales: Staphylococcaceae).

The inhibitory effect of Chrysomya rufifacies (Macquart) and Cochliomyia macellaria (Fabricius) larval excretions-secretions (ES) on Staphylococcus aureus was determined using a portable colorimetric method without the need for any dedicated spectral instrument. Polystyrene 96 well microplates were used and 100 µl of the bacterial inoculum (5 × 105 CFU/ml) plus 100 µl of the dipteran exosecretions at different concentrations were added to each well. Subsequently, 50 µl of a 1% solution of the triphenyl tetrazolium chloride stain was added to each well to determine the bacterial viability. The color development in each well was measured with the ImageJ software S. aureus was exposed to different concentrations of the ES of both species individually. At a concentration of 800 ppm ES of C. rufifacies or Co. macellaria, bacterial growth was inhibited 97.45 ± 1.70% and 82.21 ± 1.88%, respectively. As expected, exposure to a lower concentration (i.e., 50 ppm) was less inhibitory (C. rufifacies ES, 77.65 ± 4.25% and Co. macellaria ES, 43.54 ± 4.63%). This study demonstrates for the first time the bactericidal activity of C. rufifacies and Co. macellaria ES against S. aureus. This finding is promising as it could result in the identification and synthesis of proteins capable of suppressing pathogen development in wounds. Additionally, the proposed method can simplify the use of expensive laboratory instruments for antimicrobial activity determination.

Efficacy of the mermithid nematode, Romanomermis iyengari, for the biocontrol of Anopheles gambiae, the major malaria vector in sub-Saharan Africa.

BACKGROUND: The intensive use of chemical insecticides against mosquitoes has led to the development of widespread insecticide resistance. Control of Anopheles mosquitoes in malaria endemic areas of sub-Saharan Africa has become increasingly difficult. There is an urgent need for malaria control programmes to adopt more integrated mosquito management approaches that include sustainable, nonchemical solutions. The mermithid nematode Romanomermis iyengari is one of several natural control alternatives to synthetic pesticides for mosquito suppression. This study evaluated the effectiveness of the nematode R. iyengari for control of Anopheles gambiae. METHODS: The nematode R. iyengari was mass-produced, and pre-parasitic stage (J2) were used for laboratory and field experiments. In laboratory experiments, two concentrations of pre-parasitics (5 and 10 J2 per larva) were tested against first- (L1), second- (L2) and third-instar (L3) larvae of An. gambiae. Infected larvae were observed daily to determine their mortality rate and the number of post-parasitic nematodes emerging from dead larvae. In field experiments, 3500, 4000 and 5000 J2/m2 were sprayed in separate natural Anopheles breeding sites. After treatment, the larval mosquito density in the breeding sites was assessed every 5-7 days. RESULTS: Laboratory results showed that larval An. gambiae is susceptible to nematode infection: 100% L1 larvae died within 24 hours post-treatment, and 100% of both L2 and L3 larvae died within 7 days, regardless of nematode concentrations. The average number of post-parasitic nematodes emerging per larva increased with increasing nematode concentration. In field experiments, the monthly applications of 3500 to 5000 pre-parasitic nematodes per m2 eliminated larval mosquito development in Anopheles- and mixed breeding sites. Larval mosquito density dramatically decreased five days after the first treatment in all treated sites and was maintained at a very low level during the whole experimental period. Basically, only early instar larva were detected in treated sites throughout the test period. The average number of post-parasitic nematodes emerging per larva collected in treated sites was 1.45, 2, and 5.7 respectively for sites treated with 3500, 4000, and 5000 J2/m2. CONCLUSIONS: Malaria mosquito larvae is susceptible to R. iyengari infection in West Africa. Parasitism intensity depends on tested nematode concentrations. Monthly application of 3500 J2/ m2 was enough to control effectively larval An. gambiae in wetlands and floodable locations in West Africa.

Larvicidal effect of Clinopodium macrostemum essential oil extracted by microwave-assisted hydrodistillation against Culex quinquefasciatus (Diptera: Culicidae).

INTRODUCTION: In the present study, we determined the chemical composition of Clinopodium macrostemum essential oil obtained by microwave-assisted hydrodistillation and its effect on the growth and development of Culex quinquefasciatus mosquito larvae. METHODS: The essential oil compounds were identified by gas chromatography-mass spectrometry analysis, and bioassays were conducted to evaluate the influence on the developmental stages of early second instar larvae of Cx. quinquefasciatus until the emergence of adults, using essential oil concentrations of 50, 100, 200, 400, and 800mg/L. RESULTS: The gas chromatography-mass spectrometry analyses revealed that the leaf essential oil of C. macrostemum contained 32 compounds and the major chemical compounds identified were linalool (55.4%), nerol (6.4%), caryophyllene (6.25%), menthone (5.8%), geraniol acetate (4.1%), terpineol (3.7%), and pulegone (2.8%). The essential oil yield obtained by microwave-assisted hydrodistillation was 0.8% at 20 min. The treatments showed lethal concentrations (LC50 and LC90) of 22.49 and 833.35mg/L, respectively, after the final measurement of the total number of dead larvae (second, third, and fourth instars), and LC50 and LC90 of 6.62 and 693.35mg/L, respectively, at the end of the experimental period. The essential oil inhibited the growth and development of the mosquito larvae by 32% (relative growth index = 0.68) at 50mg/L, and up to 47% (relative growth index = 0.53) at 800mg/L. CONCLUSION: The present study demonstrated the larvicidal effect of C. macrostemum essential oil on Cx. quinquefasciatus, which can be attributed to the oxygenate compounds obtained by the extraction method.

Larvicidal effect of Clinopodium macrostemum essential oil extracted by microwave-assisted hydrodistillation against Culex quinquefasciatus (Diptera: Culicidae)

Abstract INTRODUCTION: In the present study, we determined the chemical composition of Clinopodium macrostemum essential oil obtained by microwave-assisted hydrodistillation and its effect on the growth and development of Culex quinquefasciatus mosquito larvae. METHODS: The essential oil compounds were identified by gas chromatography-mass spectrometry analysis, and bioassays were conducted to evaluate the influence on the developmental stages of early second instar larvae of Cx. quinquefasciatus until the emergence of adults, using essential oil concentrations of 50, 100, 200, 400, and 800mg/L. RESULTS: The gas chromatography-mass spectrometry analyses revealed that the leaf essential oil of C. macrostemum contained 32 compounds and the major chemical compounds identified were linalool (55.4%), nerol (6.4%), caryophyllene (6.25%), menthone (5.8%), geraniol acetate (4.1%), terpineol (3.7%), and pulegone (2.8%). The essential oil yield obtained by microwave-assisted hydrodistillation was 0.8% at 20 min. The treatments showed lethal concentrations (LC50 and LC90) of 22.49 and 833.35mg/L, respectively, after the final measurement of the total number of dead larvae (second, third, and fourth instars), and LC50 and LC90 of 6.62 and 693.35mg/L, respectively, at the end of the experimental period. The essential oil inhibited the growth and development of the mosquito larvae by 32% (relative growth index = 0.68) at 50mg/L, and up to 47% (relative growth index = 0.53) at 800mg/L. CONCLUSION: The present study demonstrated the larvicidal effect of C. macrostemum essential oil on Cx. quinquefasciatus, which can be attributed to the oxygenate compounds obtained by the extraction method.

Large-scale production of the malaria vector biocontrol agent Romanomermis iyengari (Nematoda: Mermithidae) in Benin, West Africa.

Background: The mermithid nematode Romanomermis iyengari is one of several natural control alternatives to synthetic pesticides for mosquito suppression. The commonly used mass rearing procedure of R. iyengari involves the use of coarse sand as a substrate for nematode maturation and oviposition. The coarse sand technique gives excellent nematode productivity in North America. However, under West African climatic conditions, this technique generates relatively lesser amounts of infectious worms. We evaluated coconut coir fibres as a replacement for coarse sand to improve yields in large-scale production of R. iyengari in Benin, West Africa. Materials and Methods: Culex quinquefasciatus was the host for the nematodes, and mosquitoes were blood-fed on chickens. Four days after blood feeding, egg rafts were collected and transferred into trays, each containing 2 l of water. The mosquito larvae were fed with fish food. When the mosquito larvae reached the second instar, preparasites (J2) were added (3 J2/larva) to the incubation trays. Eight days after infection, post-parasitic juveniles were separated from the water containing dead mosquito larvae and other debris using sieves and needles; 2 g of them were deposited in containers with coarse sand or coconut coir fibres and water. Three hours later, the water was drained, the jars covered and stored for eight weeks, after which J2 abundance was determined, using a total of 320 containers for each substrate. The abundance of J2 preparasites was also assessed 3-5 months after storage to determine the impact of long-term storage on the J2 yield. Results: After 2 months storage, 2 g of post-parasites (~457 females and 583 males) yielded an average of 559,300±6094 J2 and 155,818±4427 J2 per container for coconut fibres and for coarse sand, respectively. During long-term storage, yields of J2 on coconut fibres substrate slowly decreased from 442,180±9322 J2 (3 months storage) to 163,632±12,416 J2 per container (5 months storage). On coarse sand substrate, the yield was relatively low and decreased from 49,812±1200 J2 at 3 months storage to 3046±229 J2 at 5 months storage. Conclusion: Under West African climatic conditions, coconut coir fibres gave significantly higher preparasitic nematode yields than the coarse sand technique.

Inhibition of the growth and development of mosquito larvae of Culex quinquefasciatus (Diptera: Culicidae) treated with extract from leaves of Pseudocalymma alliaceum (Bignonaceae).

OBJECTIVE: To determine larvicidal activity of the essential oil, hydrolat and botanical extracts derived from leaves of Pseudocalymma alliaceum on mosquito larvae of Culex quinquefasciatus. METHODS: Groups of twenty larvae were used in the larvicidal assays. The mortality, relative growth rate, the larval and pupal duration and viability was estimated. The essential oil was analyzed by solid phase microextraction using gas chromatography coupled to mass spectrometry. RESULTS: Essential oil at 800 ppm showed larvicidal activity at 24 h with lethal values of LC50 and LC90 of 267.33 and 493.63 ppm. The hydrolat at 20% and 10% on 2nd stage larvae showed 100% effectiveness after 24 h. The aqueous extract at 10% had a relative growth index of 0.58, while the ethanolic and methanolic extract obtained values of 0.76 and 0.70 and control reached 0.99. Larvae treated with 10% of methanol, ethanol and aqueous extract showed a reduction in larval duration of 5.00, 2.20 and 4.35 days; ethanol extract at 1% provoke decrease of 2.40 days in the development and exhibited an increment of 3.30 days when treated with 0.01%. Aqueous, ethanol and methanol extracts at 10% reduced in 6.15, 3.42 and 5.57 days pupal development. The main compounds were diallyl disulfide (50.05%), diallyl sulfide (11.77%) and trisulfide di-2-propenyl (10.37%). CONCLUSIONS: The study demonstrated for the first time, the larvicidal activity of the essential oil and hydrolat of Pseudocalymma alliaceum; aqueous, ethanol and methanol extracts inhibited the normal growth and development of mosquito larvae, prolonging and delaying larval and pupal duration.

Efecto patogénico de 3 nematodos parásitos en larvas de Aedes aegypti en condiciones de laboratorio, en Cuba / Pathogenic effect of 3 parasitic nematodes in Aedes aegypti larvae under laboratory conditions in Cuba

Se evaluó el efecto patogénico de 3 nematodos parásitos Romanomermis culicivorax Ross y Smith, 1976, Romanomermis iyengari Welch, 1964 y Strelkovimermis spiculatus Poinar y Camino, 1986, a diferentes dosis de aplicación, en larvas de Aedes aegypti Linnaeus, 1762. Para cada unidad experimental se utilizaron 100 larvas de II estadio de este mosquito y se infestaron con nematodos preparasíticos de las 3 especies, en proporciones de 3:1, 5:1, 10:1, 15:1 y 20:1. Las medias de infestación y las tasas de parasitismo aumentaron en la medida en que se incrementaron las dosis. A bajas densidades de nemátodos (3 y 5 nemátodos/larva) R culicivorax resultó ser más efectivo al compararla con las otras especies, sin embargo con una proporción de 10:1 todos los nemátodos rovocaron 100 por ciento de mortalidad, siendo S spiculatus el nemátodo que provocó las medias de infestación más altas. Por esta razón, una proporción de 10:1 pudiera ser recomendada para que estos nematodos sean evaluados en condiciones naturales en recipientes artificiales no útiles como una alternativa biológica para el control de Aedes aegypti

Efecto patogénico de 3 nematodos parásitos en larvas de Aedes aegypti en condiciones de laboratorio, en Cuba / Pathogenic effect of 3 parasitic nematodes in Aedes aegypti larvae under laboratory conditions in Cuba

Se evaluó el efecto patogénico de 3 nematodos parásitos Romanomermis culicivorax Ross y Smith, 1976, Romanomermis iyengari Welch, 1964 y Strelkovimermis spiculatus Poinar y Camino, 1986, a diferentes dosis de aplicación, en larvas de Aedes aegypti Linnaeus, 1762. Para cada unidad experimental se utilizaron 100 larvas de II estadio de este mosquito y se infestaron con nematodos preparasíticos de las 3 especies, en proporciones de 3:1, 5:1, 10:1, 15:1 y 20:1. Las medias de infestación y las tasas de parasitismo aumentaron en la medida en que se incrementaron las dosis. A bajas densidades de nemátodos (3 y 5 nemátodos/larva) R culicivorax resultó ser más efectivo al compararla con las otras especies, sin embargo con una proporción de 10:1 todos los nemátodos rovocaron 100 por ciento de mortalidad, siendo S spiculatus el nemátodo que provocó las medias de infestación más altas. Por esta razón, una proporción de 10:1 pudiera ser recomendada para que estos nematodos sean evaluados en condiciones naturales en recipientes artificiales no útiles como una alternativa biológica para el control de Aedes aegypti(AU)

[Pathogenic effect of 3 parasitic nematodes in Aedes aegypti larvae under laboratory conditions in Cuba]. / Efecto patogénico de 3 nematodos parásitos en larvas de Aedes aegypti en condiciones de laboratorio, en Cuba.

The pathogenic effect of three parasitic nematodes, Romanomermis culicivorax Ross y Smith, 1976, Romanomermis iyengari Welch, 1964, and Strelkovimermis spiculatus Poinar and Camino, 1986, was evaluated at different application doses in larvae of Aedes aegypti. For each experimental unit, one hundred second instar larvae of this mosquitoe were infested with preparasites of the three nematode species in the following proportions: 3:1, 5:1, 10:1, 15:1 and 20:1. Both infestation mean and parasitism rate increased as the doses augmented. Romanomermis culicivorax proved to be more effective at low doses when compared to other species; however, with the 10:1 proportion, all the nematodes caused 100% of mortality. S. spiculatus showed the highest infestation rate. For this reason, a proportion of 10:1 could be recommended to evaluate these nematodes under natural conditions in useless artificial containers as a biological alternative for Aedes aegypti control.

Susceptibilidad de las larvas de Aedes aegypti al parasitismo por Romanomermis culicivorax en condiciones de laboratorio y de campo en Oaxaca, Mexico / Susceptibility of Aedes aegypti larvae to parasitism by Romanomermis culicivorax in laboratory and field conditions in Oaxaca, Mexico

En junio de 1996, en el Estado de Oaxaca, Mexico, se expusieron larvas de mosquito de la especie Aedes aegypti (Linneo) a los preparasitos infectivos del nematodo Romanomermis culicivorax, Ross y Smith, en condiciones de laboratorio y de campo. Para los experimentos de laboratorio se utilizaron larvas en estadio I-IV, colectadas en reservorios naturales. Los experimentos se realizaron por triplicado, con 100 larvas de cada estadio larvario por experimento, y se probaron tres dosis de aplicacion: 5:1, 10:1 y 15:1 (5, 10 o 15 preparasitos por larva de mosquito). Para los estudios de campo se tomaron 13 criaderos naturales de A. aegypti con larvas en estadio I-IV y se aplico una dosis de 15:1 por cada criadero. De acuerdo con los resultados obtenidos en los experimentos de laboratorio, se observo un aumento de la infestacion media de las larvas a medida que aumentaba la dosis de aplicacion desde 5:1 hasta 15:1. Para la dosis de 10:1, la tasa de parasitismo alcanzo valores de 100, 100, 85 y 74 por ciento en las larvas en estadio I, II, III y IV, respectivamente, y, para la dosis de 15:1, valores de 100, 100, 90 y 79 por ciento, respectivamente. Los resultados de las pruebas de campo con la aplicacion de una dosis de 15:1 en los 13 reservorios naturales proporcionaron elevadas tasas de parasitismo, con valores entre 80-98 por ciento, lo que demostro la susceptibilidad de esta especie de mosquito al parasitismo por R. culicivorax en el Estado de Oaxaca, Mexico

Susceptibilidad de las larvas de aedes aegypti al parasitismo por Romanomermis culivorax en condiciones de laboratorio y de campo en Oaxaca, México / Susceptibility of aedes aegypti larvae to parasitism by Romanomermis culicivorax in laboratory and field conditions in Oaxaca, Mexico

In June 1996 in the state of Oaxaca, Mexico, larvae of the mosquito species Aedes aegypti were exposed to infective preparasites of the nematode Romanomermis culicivorax, Ross and Smith, in the laboratory and in the field. For the laboratory experiments larvae in instars I­IV were used; they had been collected in natural reservoirs. The laboratory experiments were carried out in triplicate, with 100 larvae of each larval stage per experiment. Three preparasite application dosage ratios were tested: 5, 10, or 15 preparasites per mosquito larva. For the field studies 13 A. aegypti outdoor breeding sites were used, with larvae in instars I­IV and a 15:1 preparasite dosage ratio. With the laboratory experiments, an increase was observed in the average infestation of the larvae as the preparasite application ratio was increased from 5:1 to 15:1. With a 10:1 ratio, the rates of parasitism were 100%, 100%, 85%, and 74% in the larvae in instars I, II, III, and IV, respectively; for the 15:1 preparasite ratio, parasitism rates were 100%, 100%, 90%, and 79%, respectively. The field tests with the 15:1 preparasite dosage ratio in the 13 outdoor reservoirs produced parasitism rates of 80% to 98%, thus demonstrating the susceptibility of this species of mosquito to parasitism by R. culicivorax in Oaxaca, Mexico.

En junio de 1996, en el Estado de Oaxaca, México, se expusieron larvas de mosquito de la especie Aedes aegypti (Linneo) a los preparásitos infectivos del nemátodo Romanomermis culicivorax, Ross y Smith, en condiciones de laboratorio y de campo. Para los experimentos de laboratorio se utilizaron larvas en estadio I­IV, colectadas en reservorios naturales. Los experimentos se realizaron por triplicado, con 100 larvas de cada estadio larvario por experimento, y se probaron tres dosis de aplicación: 5:1, 10:1 y 15:1 (5, 10 ó 15 preparásitos por larva de mosquito). Para los estudios de campo se tomaron 13 criaderos naturales de A. aegypti con larvas en estadio I­IV y se aplicó una dosis de 15:1 por cada criadero. De acuerdo con los resultados obtenidos en los experimentos de laboratorio, se observó un aumento de la infestación media de las larvas a medida que aumentaba la dosis de aplicación desde 5:1 hasta 15:1. Para la dosis de 10:1, la tasa de parasitismo alcanzó valores de 100, 100, 85 y 74% en las larvas en estadio I, II, III y IV, respectivamente, y, para la dosis de 15:1, valores de 100, 100, 90 y 79%, respectivamente. Los resultados de las pruebas de campo con la aplicación de una dosis de 15:1 en los 13 reservorios naturales proporcionaron elevadas tasas de parasitismo, con valores entre 80­98%, lo que demostró la susceptibilidad de esta especie de mosquito al parasitismo por R. culicivorax en el Estado de Oaxaca, México

The Romanomermis iyengari parasite for Anopheles pseudopunctipennis suppression in natural habitats in Oaxaca State, Mexico

In September and November 1996 Romanomermis yengari Welch, a parasite of larval mosquitoes, was released in 44 natural larval habitat sites of Anopheles pseudopunctipennis Theobald in an attempt to reduce the larval populations of this important malaria vector. The selected treatment sites ranged in size from 5 to 500 m2. The study was carried out in Pochutla District of Oaxaca State, on the Pacific coast of Mexico. Chemical pesticides to reduce vector populations have been the principal tool in malaria supression campaigns. However, the excessive use of these chemiclas has created pesticide resistance and other serious collateral problems. Therefore, a biological control project using agents that are pathogens of Anopheles larvae was initiated in 1996. The principal objective was to establish mass rearing capacities for R. iyengari. Detailed methodology for rearing and introducing these nematodes into mosquito larval habitats was established at the National Polytechnic Institute of Oaxaca State. Before application of the parasites to larval habitats, site characterirstics were determined, including size, depth, aquatic vegetation, salinity, ph, conductivity, temperature, and pretreatment larval density. With a compressed air sprayer, infective mermithid parasites were released at rates of either 2 000 or 3 000/m2, and the parasites produced high levels of infection. Anopheles populations were sampled 72 h posttreatment, and the larvae obtained were taken to the laboratory and examined through microscopic dissection to determine infection levels and mean parasitism. Nematode parasitism ranged from 85 to 100 per cent at all the treatment sites, even though no previous information concerning field parasitism of An. pseudopunctipennis by R. iyengari has been reported. In addition, a significant reduction of mosquito larval density at the treatment sites was found five days after the nematode application. Levels of parasitism were indicative of the number of mosquito larvae killed by the treatment since infected larvae never progressed to the pupal stage. Results from sampling nine of the sites 2 months after the initial application of nematodes indicated that a high number of mosquito larvae were infected by parasites that had emerged from eggs previously deposited in the stratum. This work suggests the potential of this mermithid to reduce An. pseudopunctipennis populations in Oaxaca State

The Romanomermis iyengari parasite for Anopheles pseudopunctipennis suppression in natural habitats in Oaxaca State, Mexico / El parásito Romanomermis iyengari para la supresión de Anopheles pseudopunctipennis de sus hábitat naturales en el estado de Oaxaca, México

In September and November 1996 Romanomermis yengari Welch, a parasite of larval mosquitoes, was released in 44 natural larval habitat sites of Anopheles pseudopunctipennis Theobald in an attempt to reduce the larval populations of this important malaria vector. The selected treatment sites ranged in size from 5 to 500 m2. The study was carried out in Pochutla District of Oaxaca State, on the Pacific coast of Mexico. Chemical pesticides to reduce vector populations have been the principal tool in malaria supression campaigns. However, the excessive use of these chemiclas has created pesticide resistance and other serious collateral problems. Therefore, a biological control project using agents that are pathogens of Anopheles larvae was initiated in 1996. The principal objective was to establish mass rearing capacities for R. iyengari. Detailed methodology for rearing and introducing these nematodes into mosquito larval habitats was established at the National Polytechnic Institute of Oaxaca State. Before application of the parasites to larval habitats, site characterirstics were determined, including size, depth, aquatic vegetation, salinity, ph, conductivity, temperature, and pretreatment larval density. With a compressed air sprayer, infective mermithid parasites were released at rates of either 2 000 or 3 000/m2, and the parasites produced high levels of infection. Anopheles populations were sampled 72 h posttreatment, and the larvae obtained were taken to the laboratory and examined through microscopic dissection to determine infection levels and mean parasitism. Nematode parasitism ranged from 85 to 100 per cent at all the treatment sites, even though no previous information concerning field parasitism of An. pseudopunctipennis by R. iyengari has been reported. In addition, a significant reduction of mosquito larval density at the treatment sites was found five days after the nematode application. Levels of parasitism were indicative of the number of mosquito larvae killed by the treatment since infected larvae never progressed to the pupal stage. Results from sampling nine of the sites 2 months after the initial application of nematodes indicated that a high number of mosquito larvae were infected by parasites that had emerged from eggs previously deposited in the stratum. This work suggests the potential of this mermithid to reduce An. pseudopunctipennis populations in Oaxaca State

En septiembre y noviembre de 1996, Romanomermis iyengari Welch, parásito de larvas de mosquitos, fueron liberados en 44 lugares que servían de hábitat natural a larvas de Anopheles pseudopunctipennis Theobald con objeto de reducir las poblaciones larvarias de este importante vector de la malaria. Los lugares elegidos para el tratamiento variaron en tamaño de 5 a 500 m2. El estudio se llevó a cabo en el distrito de Pochutla en el Estado de Oaxaca, sobre la costa pacífica de México. Los plaguicidas químicos que reducen las poblaciones del vector han sido el instrumento principal en las campañas para la supresión de la malaria. No obstante, el uso excesivo de estas sustancias químicas ha dado origen a resistencia y a otros problemas serios. Por consiguiente, en 1996 se inició un proyecto de control biológico basado en el uso de agentes que son patógenos para las larvas de Anopheles. El objetivo principal fue establecer un sistema para criar R. iyengari en grandes cantidades. En el Instituto Politécnico Nacional del estado de Oaxaca se estableció un método detallado para criar estos nematodos e introducirlos en los hábitat de las larvas de mosquitos. Antes de colocar los parásitos dentro de los hábitat de las larvas, se determinaron las características de los lugares, entre ellas su tamaño, profundidad, vegetación acuática, salinidad, pH, conductividad, temperatura y densidad larvaria antes del tratamiento. Con un fumigador por compresión de aire se liberaron parásitos de los nematodos infectantes a razones de 2 000 ó 3 000 por m2 y los parásitos produjeron tasas de infestación elevadas. A las 72 horas de aplicarse el tratamiento se tomaron muestras de las poblaciones de Anopheles y las larvas así obtenidas se llevaron al laboratorio, donde se sometieron a disección y examen microscópico para determinar los niveles de infestación y la carga parasitaria promedio. La carga de parásitos osciló entre 85 y 100% en todos los lugares donde se aplicó el tratamiento, a pesar de que no se habían notificado datos previamente sobre la carga parasitaria de An. pseudopunctipennis por R. iyengari en campo abierto. En los lugares tratados también se detectó una notable reducción de la densidad de las larvas de mosquitos a los 5 días de aplicarse los nematodos. La carga parasitaria fue indicación del número de larvas de mosquitos que murieron como consecuencia del tratamiento, ya que las larvas infestadas nunca llegaron a formar crisálidas. A juzgar por los resultados del muestreo de nueve de los lugares tratados 2 meses después de la aplicación inicial de nematodos, un gran número de las larvas de mosquitos fueron infectadas por parásitos que habían nacido de huevos que ya estaban depositados en la tierra. Este trabajo sugiere que este nematodo puede reducir las poblaciones de An. pseudopuctipennis en el Estado de Oaxaca.