Morphological and Chromatic Variation in Four Populations of Triatoma mexicana (Hemiptera: Reduviidae).

Triatoma mexicana is an endemic species of Mexico and is distributed in the states of Hidalgo, Queretaro, Guanajuato, and San Luis Potosi, being naturally infected with Trypanosoma cruzi, which increases its importance in the region. The species description was made in 1848, but there are only a few studies on its morphology, biology, and behavior. The present manuscript shows the presence of morphological and chromatic variations among populations of T. mexicana from the states of Hidalgo (Valle del Mezquital and Meztitlan), Guanajuato and Queretaro. The study employed 136 specimens collected in four locations. Scanning electron microscopy was used to study the morphological characteristics of the head, pronotum, and scutellum; also, we measured the width of the abdomen and the total length in the specimens of each population. The morphometric analysis considered 19 variables in the previous structures. Significant differences were found in the dimensions of the head and pronotum, but not in the scutellum; there is clear discrimination among the four proposed populations. The chromatic patterns observed in the connexivum go from yellow to brown and show some significant differences related to geographical origin. The set of evaluated characters showed a higher degree of difference in the population of Guanajuato, clearly separating from the rest of the populations, indicating the possibility of a divergence process. The characteristics observed in the remaining populations could be adaptive responses to their habitat.

Oviposition Deterrent and Larvicidal and Pupaecidal Activity of Seven Essential Oils and their Major Components against Culex quinquefasciatus Say (Diptera: Culicidae): Synergism-antagonism Effects.

The larvicidal activity of essential oils cinnamon (Cinnamomumverum J. Presl), Mexican lime (Citrusaurantifolia Swingle) cumin (Cuminumcyminum Linnaeus), clove (Syzygiumaromaticum (L.) Merr. & L.M.Perry), laurel (Laurusnobilis Linnaeus), Mexican oregano (Lippiaberlandieri Schauer) and anise (Pimpinellaanisum Linnaeus)) and their major components are tested against larvae and pupae of Culexquinquefasciatus Say. Third instar larvae and pupae are used for determination of lethality and mortality. Essential oils with more than 90% mortality after a 30-min treatment are evaluated at different time intervals. Of the essential oils tested, anise and Mexican oregano are effective against larvae, with a median lethal concentration (LC50) of 4.7 and 6.5 µg/mL, respectively. Anise essential oil and t-anethole are effective against pupae, with LC50 values of 102 and 48.7 µg/mL, respectively. Oregano essential oil and carvacrol also have relevant activities. A kinetic analysis of the larvicidal activity, the oviposition deterrent effect and assays of the effects of the binary mixtures of chemical components are undertaken. Results show that anethole has synergistic effects with other constituents. This same effect is observed for carvacrol and thymol. Limonene shows antagonistic effect with ß-pinene. The high larvicidal and pupaecidal activities of essential oils and its components demonstrate that they can be potential substitutes for chemical compounds used in mosquitoes control programs.

Essential oils and their components as an alternative in the control of mosquito vectors of disease.

More than half of the human population is exposed to mosquito-borne infections. Climate change and the emergence of strains resistant to traditionally used insecticides have motivated the search of new agents for mosquito population control. Essential oils have been effective repellents and larvicidal agents.The aim of this work was to review research studies conducted in recent years on the larvicidal activity of essential oils and their components against Aedes, Anopheles and Culex mosquitoes, as well as the latest reports about their possible mechanism of action.

External female genitalia of six species of the genus Meccus (Hemiptera: Reduviidae: Triatominae).

Triatomine classification is based on morphological characteristics. Studies have been conducted to improve their identification by observing many characteristics. However, there are problems of differentiating among highly interrelated species and new criteria are required. The purpose of this study was to determine the morphological differences in the external female genitalia of M. pallidipennis, M. longipennis, M. picturatus, M. bassolsae, M. mazzottii, and M. phyllosomus in order to distinguish among species using scanning electron microscopy. Observations were made of the dorsal, posterior, lateral, and ventral views of the female external genitalia for each species. In the six species we studied, relevant differences were observed in the dorsal view of the X segment, as well as the IX, VIII, and VII tergites. In the posterior and lateral view, the most visible differences were registered in the gonocoxite size of the segments VIII, IX, and X. Finally, in the ventral view of the VII sternite, differences among species were observed in the size of the inflection in the top and upper corner. Our results show that it was possible to differentiate among the triatominae species for each of the four views by using a scanning electron microscope to analyze morphological characteristics of the VII, VIII, IX, and X abdomen segments.

Morphological and morphometric analysis of scutella of six species and two subspecies of Triatoma (Hemiptera: Reduviidae) in Mexico.

Morphological characters can be used to distinguish the vast majority of triatomine species, but the existence of high levels of phenotypic plasticity and recently diverged species can lead to erroneous determinations. To approach this problem, we analyzed the male and female morphologies of the scutella of Triatoma barberi, T. dimidiata, T. lecticularia, T. mexicana, T. recurva, T. rubida, and two sub-species, T. protracta protracta and T. protracta nahuatlae. Scutellum samples were observed by scanning electron microscopy and subjected to morphological analysis and morphometric investigation using a canonical discriminant analysis. The results revealed differences primarily in central depression shape, posterior process, and vestiture. We observed clear dimension-based differences in scutellum morphometry in all the taxa under study, providing sound evidence for species and subspecies differentiation. On the other hand, there is no difference between sexes in T. lecticularia, T. protracta protracta, and T. protracta nahuatlae. Our methodology can be implemented to differentiate species of the genus Triatoma.

Prevalence of Human Papillomavirus in Women from the State of Michoacan, Mexico, Showed High Frequency of Unusual Virus Genotypes.

BACKGROUND: Human papillomaviruses (HPVs), the leading cause of cervical cancer, are distributed worldwide, with high prevalence in developing countries. OBJECTIVE: The objective of the study is to know the prevalence and genotypes of HPV in women from the state of Michoacán and the Women's Hospital in Morelia, Michoacán. MATERIALS AND METHODS: Cervical smear samples (159,288) were subjected to HPV detection by hybrid capture 2. A subsample of 484 patients from the Women's Hospital was studied by Papanicolaou test and linear array HPV genotyping, and when positive, patients were also examined by colposcopy and histopathology. RESULTS: The overall prevalence for HPV in Michoacán State was 7.74%; 7.11% in 2009, 6.46% in 2010, 9.58% in 2011, and 8.43% in 2012. The highest prevalence was found in the age groups < 25 and 25-34 years. The prevalence at the Women's Hospital was 8.51%. Cytological examination revealed normal cytology in 64.44% of samples, 26.66 % with low-grade and 8.88 % with high-grade squamous intraepithelial lesion (HSIL). However, by colposcopy, normal tissue appearance was found only in 26.66%; 51% were reclassified as low-grade squamous intraepithelial lesion, 17.77% as HSIL, and in 4.4% atrophy was observed. The most prevalent genotype in single infections was HPV59, followed by HPV51 and HPV45. Double infections occurred with the following genotypes: 52-53, 51-59, 61-67, 66-11, 16-62, 53-62, 59-CP6108, 45-66, and 45-51. Triple infections were identified as: 6-31-39, 51-59-62, 51-62-81, 54-55-59, 16-58-71, and 16-59-62. CONCLUSIONS: The prevalent genotype found among women from Michoacán, HPV59, was different to the rest of the country. The high prevalence of HPV59 could be due to cases imported to Michoacán by agricultural workers migrating to the USA or may be associated to ethnicity differences. Implications of this finding for immunization programs should be explored.

Aceites esenciales y sus componentes como una alternativa en el control de mosquitos vectores de enfermedades / Essential oils and their components as an alternative in the control of mosquito vectors of disease

Resumen Más de la mitad de la población humana está expuesta a contraer infecciones transmitidas por mosquitos. El cambio climático y la aparición de cepas resistentes a los insecticidas tradicionalmente utilizados han motivado la búsqueda de nuevos agentes capaces de controlar las poblaciones de mosquitos. Los aceites esenciales han resultado ser eficaces agentes repelentes y larvicidas. El objetivo de este trabajo fue revisar las investigaciones llevadas a cabo en los últimos años sobre la actividad larvicida de los aceites esenciales y sus componentes contra mosquitos de los géneros Aedes, Anopheles y Culex, así como los últimos reportes sobre su posible mecanismo de acción.

Abstract More than half of the human population is exposed to mosquito-borne infections. Climate change and the emergence of strains resistant to traditionally used insecticides have motivated the search of new agents for mosquito population control. Essential oils have been effective repellents and larvicidal agents. The aim of this work was to review research studies conducted in recent years on the larvicidal activity of essential oils and their components against Aedes, Anopheles and Culex mosquitoes, as well as the latest reports about their possible mechanism of action.

Comparative egg morphology of six Meccus species and Triatoma recurva (Stål, 1868) Hemiptera: Reduviidae.

We investigated the morphology and morphometry of eggs from the colonies of the Entomology Laboratory at ENCB-IPN belonging to six species of the genus Meccus and Triatoma recurva, using both light and scanning electron microscopy. Egg ornamentation is an important parameter to consider in the differentiation of species. Samples were observed under a scanning electron microscope. Measurements of fifty eggs per species included length, width, and opercular diameter, which were used for the morphometric analysis. The results showed that the seven species display a polygonal ornamentation dominated by hexagons; the operculum shows also a polygonal ornamental characteristic in each species. Morphometry provided valuable information for discriminating between closely related species of the genus Meccus and Triatoma recurva, a species akin to this group, thereby facilitating the complete discrimination of these species.

BmVDAC upregulation in the midgut of Rhipicephalus microplus, during infection with Babesia bigemina.

The molecular mechanisms involved during the infection of Rhipicephalus microplus midgut cells by Babesia bigemina are of great relevance and currently unknown. In a previous study, we found a voltage-dependent anion channel (VDAC)-like protein (BmVDAC) that may participate during parasite invasion of midgut cells. In this work, we investigated BmVDAC expression at both mRNA and protein levels and examined BmVDAC localization in midgut cells of ticks infected with B. bigemina at different times post-repletion. Based on the RT-PCR results, Bmvdac expression levels were significantly higher in infected ticks compared to uninfected ones, reaching their highest values at 24h post-repletion (p<0.0001). Similar results were obtained at the protein level (p<0.0001). Interestingly, BmVDAC immunolocalization showed that there was an important differential expression and redistribution of BmVDAC protein between the midgut cells of infected and uninfected ticks, which was more evident 24h post-repletion of infected ticks. This is the first report of BmVDAC upregulation and immunolocalization in R. microplus midgut cells during B. bigemina infection. Further studies regarding the function of BmVDAC during the infection may provide new insights into the molecular mechanisms between B. bigemina and its tick vector and could result in its use as an anti-tick and transmission-blocking vaccine candidate.

Detection of Paragonimus mexicanus (Trematoda) metacercariae in crabs from Oaxaca, Mexico.

Metacercariae of Paragonimus mexicanus were collected in crabs Tehuana guerreroensis (Rathbun, 1933) in the municipality of Putla, Oaxaca, Mexico. Metacercariae were found in 20.8% of the crabs collected, with an average of 1.9 metacercarie per crab. Stained metacercariae showed the specific characteristics of P. mexicanus by morphology and sequencing a fragment of the 28S ribosomal gene obtained by PCR. These findings reveal that T. guerreroensis is an intermediate host for P. mexicanus; this new report is relevant considering the potential risk of transmission in the states of Oaxaca and Guerrero, Mexico.

Morphology and morphometry of the scutellum of six species in the genus Meccus (Hemiptera: Triatominae).

We studied the morphology and morphometry of scutella from six species of the hemipteran genus Meccus to identify new tools to help solve taxonomic problems in closely related insect species of epidemiological relevance. Scutellum samples were observed by scanning electron microscopy and were subjected to morphometric analysis. The results mainly show differences in central depression shape, posterior process, and vestiture. We found significant dimensional differences in scutellum morphometry and a clear sexual dimorphism among species. A combination of morphology and morphometry can be used to differentiate among species of the genus Meccus.

Morphological study of eggs from five Mexican species and two morphotypes in the genus Triatoma (Laporte, 1832).

We describe and compare the morphology and morphometry of the egg exochorion for five species and two morphotypes of Mexican triatomines with scanning electron microscopy. The results show differences in egg ornamentation for each species, including between morphotypes. Polygonal ornamentation was observed in each species, including pentagons, octagons and, in certain cases, a majority of hexagons. We observed small perforations in T. protracta protracta, small spheres on the T. lecticularia polygons, a crown with festoons in T. barberi, and less complex ornamentation in T. mexicana. Through morphometric analysis, significant differences in egg dimensions were determined for the studied species.

Larvicidal activity of micronized aqueous suspension of calcium hydroxide against Aedes aegypti and Culex quinquefasciatus (Diptera: Culicidae).

In the search of alternatives for the control of mosquitoes of medical importance, we evaluated the larvicidal activity of micronized suspensions of calcium hydroxide [Ca(OH)2] against Aedes aegypti and Culex quinquefasciatus. Tests conducted under laboratory conditions determined a LC50 = 0.027% (LC90 = 0.096%) for A. aegypti and a LC50 = 0.092% (LC90 = 0.2%) for C. quinquefasciatus, at 24 h post-treatment. Considering that the LC50 for the less susceptible species killed 100% of larvae for both species at 48 h post-treatment, we decided to use the diagnostic concentration of 0.1% which eliminated 100% of larvae at 48 h under a simulated field trial. There was a residual effect for up to 84 and 70 days for A. aegypti and C. quinquefasciatus, respectively. Evaluation of Ca(OH)2 on breeding sites showed a larvicidal activity of 100% for up to 56 days. When the micronized Ca(OH)2 was incorporated at concentrations from 0.02% (w/v), a superficial film was formed which killed 100% of the larvae of both species after 24 h of contact, and the activity remains until the film broke apart due to stirring. The fact that Ca(OH)2 is cheap and the people in rural areas of Mexico and other countries know the handling procedures for this compound led us to consider that 0.1% suspensions of Ca(OH)2 could be used for mosquito control in deposits of water placed in human premises both in urban and rural areas.

Effect of ectoparasitic Pimeliaphilus plumifer mites (Acari: Pterygosomatidae) on Meccus pallidipennis (Hemiptera: Reduviidae) and several other Chagas' disease vectors under laboratory conditions.

Several biological parameters were evaluated to determine the capacity of Pimeliaphilus plumifer as biological control agent of Triatominae bugs. When P. plumifer and bugs of a variety of triatomine species were forced together in cages in the laboratory, the incidence of mite infestation was the following: Meccus pallidipennis > M. bassolsae > Triatoma rubida > M. longipennis > M. picturatus, and practically no mites were found on T. infestans and Rhodnius prolixus. Adults and hexapod larvae of P. plumifer were the only stages found to parasitize on M. pallidipennis. Fourth and fifth instar nymphs of this bug appeared most susceptible to mite infestation. P. plumifer mites located preferably on the coxae, ventral abdomen and pronotum of M. pallidipennis bugs. The number of blood meals, amount of ingested blood, and resistance to starvation of M. pallidipennis were similar in both the control and the mite infested groups. On the other hand, mite infection reduced molting rate in nymphs and longevity in adults, increased mortality in third-fifth instar nymphs, and fewer viable eggs were laid by females infected with P. plumifer. These effects could be related with nutritional deficiencies. Our results support the use of P. plumifer mites as control agents of host Triatominae species.

Development of genital plates in nymphs of Triatoma pallidipennis, Stål 1872, (Hemiptera: Reduviidae) and its application as sexing method.

Searching for morphometric differences between sexes in immature forms, the development of genital plates in the exuviae of Triatoma pallidipennis Stål 1872 nymphs was studied. Differences were found in the form and size of the 9th genital urosternite, it is larger and wider in males as compared to females. This difference is reported in several South American Triatoma species. From our results it is possible to sex early stages from microscopic observation of genital plates in whole insects.

Development of genital plates in nymphs of Triatoma pallidipennis, StÖl 1872, (Hemiptera: Reduviidae) and its application as sexing method

Searching for morphometric differences between sexes in immature forms, the development of genital plates in the exuviae of Triatoma pallidipennis StÖl 1872nymphs was studied. Differences were found in the form and size of the 9th genital urosternite, it is larger and wider in males as compared to females. This difference is reported in several South American Triatoma species. From our results it is possible to sex early stages from microscopic observation of genital plates in whole insects