Organochlorine Pesticides Residues in Blood of Peridomestic Populations of Virginia Opossum (Didelphis virginiana) from Ex-Henequen Rural Localities of Yucatan, Mexico.

Organochlorine pesticides (OCPs) have been used for many decades, both for the control of pests in agriculture and for the control of vectors of human and animal diseases. Several recent studies have reported significant concentrations of these compounds in multiple environmental substrates due to their persistence, as well as the effect they have on ecosystem health, human health, and wildlife populations. In the present study, organochlorine pesticide residues were determined and quantified in 260 blood samples from different populations of the Virginia opossum (Didelphis virginiana) from 11 rural ex-henequen sites of the state of Yucatan, Mexico. The organochlorine groups detected, following an order of predominance and concentration, were: ΣDienes (0.0557 ppm) > ΣDDTs (0.0481 ppm) > ΣEndosulfans (0.0376 ppm) > and ΣHCHs (0.0319 ppm). The highest levels of OCPs were recorded in the opossums captured in the towns of Chicxulub and Cacalchen. In 6 of the 11 localities, the OCPs detected in the opossums showed significant differences in concentration, whereas the opossums in 4 of the 11 localities did not present this difference. The results confirm the presence and persistence of OCPs in the rural environmental of Yucatan due to both the misuse and abuse of the OCPs by rural populations. In addition, the synanthropic characteristics and abundant populations of D. virginiana in the Yucatecan region make it a good candidate to serve as a biomonitor of environmental pollution in the Yucatan Peninsula. This could aid in assessing the effects exposure to pesticides and other contaminants have on the health of the Yucatecan population, whether short, medium, or long term.

Biomonitoring Organochlorine Pesticides in Didelphis virginiana from Yucatan, Mexico by GC-ECD.

The aim of the present work was to apply a validated methodology for the detection of organochlorine pesticides in Didelphis virginiana (Virginia opossum) serum samples collected in Yucatan, Mexico. Recent studies performed to investigate the presence of Organochlorines (OCLs) in water, human blood and milk, and animal tissues from Yucatan have shown that the OCLs concentrations are high and can be associated with potential human health risk. Since opossum is considered an important synanthropic species in Yucatan, 40 opossum serum samples were analyzed by gas chromatography with electron capture detector. The most common OCLs found in opossum sera were lindanes, chlordanes, drines, and endosulfan. Heptachlor, heptachlor epoxide, and lindanes were found at the highest concentrations, while dichlorodiphenyl trichloroethane and its metabolites were found at the lowest concentrations in the samples. The good linearity, precision, and accuracy obtained in the evaluated parameters in the extraction and chromatographic methods support its application for the monitoring of OCLs pesticides in populations of opossums and other wild species in Yucatan.

Transcriptomic analysis of skin pigmentation variation in the Virginia opossum (Didelphis virginiana).

Skin pigmentation and coat pigmentation are two of the best-studied examples of traits under natural selection given their quantifiable fitness interactions with the environment (e.g., camouflage) and signalling with other organisms (e.g., warning coloration). Previous morphological studies have found that skin pigmentation variation in the Virginia opossum (Didelphis virginiana) is associated with variation in precipitation and temperatures across its distribution range following Gloger's rule (lighter pigmentation in temperate environments). To investigate the molecular mechanism associated with skin pigmentation variation, we used RNA-Seq and quantified gene expression of wild opossums from tropical and temperate populations. Using differential expression analysis and a co-expression network approach, we found that expression variation in genes with melanocytic and immune functions is significantly associated with the degree of skin pigmentation variation and may be underlying this phenotypic difference. We also found evidence suggesting that the Wnt/ß-catenin signalling pathway might be regulating the depigmentation observed in temperate populations. Based on our study results, we present several alternative hypotheses that may explain Gloger's rule pattern of skin pigmentation variation in opossum, including changes in pathogen diversity supporting a pathogen-resistant hypothesis, thermal stress associated with temperate environments, and pleiotropic and epistatic interactions between melanocytic and immune genes.

PHYSIOLOGICAL BASAL PARAMETERS OF FREE-RANGING OPOSSUMS ( DIDELPHIS VIRGINIANA) IN THE YUCATAN PENINSULA, MEXICO.

The aim of the present study is to determine the basal parameters in opossums ( Didelphis virginiana) during physical examination in Yucatan, Mexico. Sixty-six opossums were captured and manually handled for physical examinations. Sex, age, cardiac and respiratory rate, body temperature, pulse, mucous membranes, capillary refill time, hydration, size of superficial lymph nodes, mental status, and body condition were evaluated. Also, comparisons between rectal and auricular temperatures were performed. The means of physiological parameters obtained were: cardiac frequency 146 beats per minute (95% confidence interval [CI]: 138.91-155.24), respiratory frequency 27.33 breaths per minute (95% CI: 25.15-29.64), and body temperature 34.01°C (95% CI: 33.71-34.31). In 54% of animals, a sinus arrhythmia was present. A significant difference was found between rectal and auricular temperature measurements. A variation of -1.64 to 1.14°C was obtained via the auricular thermometer compared with the rectal device.

Spatial distribution of Triatoma dimidiata peridomestic colonies modulated by distance between susceptible microhabitat patches.

Triatoma dimidiata is a vector of the hemoparasite Trypanosoma cruzi, the causal agent of Chagas disease. It settles reproductive colonies in the peridomicile of the premises. The peridomicile is comprised of a random set of artificial and natural features that overlap and assemble a network of microenvironmental suitable sites (patches) that interact with each other and favor the structure and proliferation of T. dimidiata colonies. The heterogeneity of patch characteristics hinders the understanding and identification of sites susceptible to colonization. In this study, a classification system using a random forest algorithm was used to identify peridomiciles susceptible to colonization to describe the spatial distribution of these sites and their relationship with the colonies of T. dimidiata in ten localities of Yucatan. From 1,000 peridomiciles reviewed, the classification showed that 13.9 % (139) of the patches were highly susceptible (HSP), and 86.1 % (861) were less susceptible (LSP). All localities had at least one HSP. The occupancy by patch type showed that the percentage of total occupancy and by colonies was higher in the HSP, while the occupancy by adult T. dimidiata without evidence of nymphs or exuviae (propagules) was higher in the LSP. A generalized additive model (GAM) revealed that the percentage of occupied patches increases as the abundance of individuals in the localities increases however, the percentage of occupied patches in LSP is lower than occupied in HSP. Distance analyses revealed that colonies and propagules were located significantly closer (approximately 200 m) to a colony in a HSP than any colony in a LSP. The distribution of T. dimidiata in the localities was defined by the distribution of patch type; as the occupancy in these patches increased, a network of peridomestic populations was configured, which may be promoted by a greater abundance of insects inside the localities. These results reveal that the spatial distribution of T. dimidiata individuals and colonies in the peridomicile at the locality scale corresponds to a metapopulation pattern within the localities through a system of patches mediated by distance and level of the vectors' occupancy.

Cutaneous Leishmaniasis Emergence in Southeastern Mexico: The Case of the State of Yucatan.

Environmental changes triggered by deforestation, urban expansion and climate change are present-day drivers of the emergence and reemergence of leishmaniasis. This review describes the current epidemiological scenario and the feasible influence of environmental changes on disease occurrence in the state of Yucatan, Mexico. Relevant literature was accessed through different databases, including PubMed, Scopus, Google, and Mexican official morbidity databases. Recent LCL autochthonous cases, potential vector sandflies and mammal hosts/reservoirs also have been reported in several localities of Yucatan without previous historical records of the disease. The impact of deforestation, urban expansion and projections on climate change have been documented. The current evidence of the relationships between the components of the transmission cycle, the disease occurrence, and the environmental changes on the leishmaniasis emergence in the state shows the need for strength and an update to the intervention and control strategies through a One Health perspective.

Urban ecology of hosts and vectors of Rickettsia in a rickettsiosis-endemic city of the Yucatan peninsula, Mexico.

Rickettsioses are vector-borne zoonotic diseases that occur in urban environments. Currently, they are associated with the presence of domestic and synanthropic animals, the ectoparasites that they harbor, and their local habitat. The implementation of prevention actions relies on the understanding of the local ecology of interactions between hosts, vector species, and the etiologic agents. In this context, this study aimed to explore and describe the occurrence of infected mammals and their ectoparasites in human urban dwellings, and those characteristics of urban dwellings associated to the presence of Rickettsia infected animals in groups of households where at least one human case of rickettsiosis has occurred in the previous year of the study. Briefly, blood-samples and ectoparasites from synanthropic and domestic animals, were obtained from groups of households from different areas of an urban settlement. Serologic and molecular diagnostics helped to identify Spotted Fever Group (SFG) and TG (Typhus Group) Rickettsia in animal and ectoparasite samples. A total of 99 mammals were sampled, 29 opossums (Didelphis virginiana), 13 house mice (Mus musculus), seven black rats (Rattus rattus) and 50 dogs. Infection occurrence in opossums was 8.3% of SFG, 50% for TG, and 4.2% of undetermined group. For house mice 46.2% for SFG and 30.8% were undetermined. Black rats 28.6% of SFG and 57.1% undetermined. Finally, dogs were 19.1% of SFG, 57.4% to TG, and 23.4% belonged to undetermined group. A total of 424 ectoparasites were collected from the mammals. In opossums occurred the ticks Ambyomma sp., Ornithodoros (Alecterobius) nr. talaje, and the flea Ctenocephalides felis. In dogs we found the ticks Rhipicephalus sanguineus s. l., Amblyomma sp., O. (A.) nr. talaje, and the flea Ct. felis. No ectoparasites were collected from rodents. The occurrence of infected animals was associated primarily with the material of the backyard floor, the type of sanitary system in the household, the presence of garbage in the backyard, presence of firewood storage, stored polyethylene terephthalate (PET) containers for sale to recyclers, and the store of construction supplies in the backyard. Nonetheless a generalized linear model showed that the household with a backyard with a dirt floor or other non-concrete material has more chances of harboring infected animals (RR= 1.74, 95% CI= 1.07-2.84 and RR= 1.03, 95% CI= 0.39-2.32 respectively). In contrast, when the house has a sanitary system of urban sewer system or a latrine outside de house, the chances of having infected animals decreased significantly (RR= 0.39, 95% CI= 0.12-0.94 and RR= 0.46, 95% CI= 0.03-2.22). We conclude that both SFG and TG rickettsioses occur in animals and their ectoparasites in peridomiciles of urban households were at least one human rickettsiosis case had occurred.

Ectoparasites of Didelphis virginiana From Yucatan, Mexico.

A faunal study is presented to determine the species of ectoparasites found in the opossum Didelphis virginiana (Kerr) (Marsupialia: Didelphidae). For this, Tomahawk traps were placed in the peridomiciles of a rural town in Yucatán, to capture individuals of this marsupial and proceed to the collection of their ectoparasites. A total of 3,023 arthropods were collected from 145 opossums. The most frequent ectoparasites were the acarines Ornithodoros (Alectorobius) nr. talaje (64.8%) (Argasidae); Ornithonyssus wernecki Fonseca (53.8%) (Macronyssidae) and Didelphilicus serrifer Fain (25.5%) (Atopomelidae); the ticks Amblyomma parvum Aragão (8.3%) and A. mixtum Koch (10.3%) (Ixodidae); and the fleas Ctenocephalides felis (Bouché) (20.7%) and Pulex simulans Baker (8.3%) (Pulicidae). It is concluded that the ectoparasite fauna of this marsupial is mainly composed of euryxenous organisms, which have been documented as vectors of diseases caused by rickettsial bacteria. Since D. virginiana is widely adapted to the peridomiciliary environment in the region, this study allows recognizing those that represent a potential risk for the transmission of vector-borne zoonotic diseases.

Redescription of Periglischrus herrerai (Acari: Spinturnicidae) Associated to Desmodus rotundus (Chiroptera: Phyllostomidae: Desmodontinae), With a Description of Adult Female Heteromorphism and an Analysis of its Variability Throughout the Neotropics.

A redescription, with a discussion of new features and illustrations, for all life stages is presented for the parasitic mite Periglischrus herrerai Machado-Allison associated with the common vampire bat Desmodus rotundus (Geoffoy), including a description of the heteromorphic female and the first description of its female deutonymph. In addition, the morphological variation of P. herrerai is evaluated by morphometric analysis of the adults, concluding that there is an evident geographic variation throughout the neotropics. This study was possible by using type material of P. herrerai from the Machado-Allison collection, and voucher specimens from other collections, and specimens from an extensive surveying of hematophagous bats in some localities of the Pacific and Atlantic versants, and central Mexico.

INFECTION BY Rickettsia felis IN OPOSSUMS (Didelphis sp.) FROM YUCATAN, MEXICO.

Rickettsia felis is an emergent pathogen and the causative agent of a typhus-like rickettsiosis in the Americas. Its transmission cycle involves fleas as biological vectors (mainly Ctenocephalides felis) and multiple domestic and synanthropic mammal hosts. Nonetheless, the role of mammals in the cycle of R. felis is not well understood and many efforts are ongoing in different countries of America to clarify it. The present study describes for the first time in Mexico the infection of two species of opossum (Didelphis virginiana and D. marsupialis) by R. felis. A diagnosis was carried out from blood samples by molecular methods through the gltA and 17 kDa genes and sequence determination. Eighty-seven opossum samples were analyzed and 28 were found to be infected (32.1%) from five out of the six studied localities of Yucatan. These findings enable recognition of the potential epidemiological implications for public health of the presence of infected synanthropic Didelphis in households.

La investigación participativa en niños como herramienta en la promoción de la salud para la prevención de la Enfermedad de Chagas en Yucatán, México / Participatory research on child's as a tool in the health promotion for the prevention of chagas disease in Yucatán, México

Resumen Introducción La Investigación Participativa (IP), es una herramienta que puede abordarse para el análisis y mejoramiento de procesos socioculturales, medioambientales, y de salud pública. La participación de niños en edad escolar en la apropiación del conocimiento sobre la Enfermedad de Chagas (EC), puede romper el ciclo de transmisión. La EC es un problema de salud pública que afecta principalmente a comunidades rurales endémicas de países en desarrollo. Objetivo Desarrollar una estrategia para la adquisición y transferencia de nuevos conocimientos en niños y niñas, debido a la falta de información acerca del ciclo de transmisión de la EC . Material y Métodos Estudio socioambiental, realizado con un grupo de 48 niños y niñas de una comunidad en pobreza extrema en Yucatán, México. Mediante herramientas de IP y con el apoyo de las familias, autoridades ejidales y escolares, se impartieron talleres educativos a niños y niñas de educación básica para conocer el ciclo de transmisión de la EC y ayudar a prevenirla, debido a la abundancia del vector en el área de estudio. Se implementó un programa denominado "Pequeños Investigadores", para iniciar procesos de apropiación y socialización del conocimiento en la comunidad. Resultados El nuevo conocimiento adquirido por el grupo de niñas y niños fue aprovechado y compartido a sus familias, compañeros de escuela, y círculos sociales, fomentando la prevención de la enfermedad. Fueron recolectados 182 triatomas a nivel domiciliar y peri domiciliar. Conclusiones Los nuevos conocimientos, actitudes y prácticas adquiridos por los niños y las niñas bajo esquemas de participación, resulta benéfico para la prevención de la EC. Se recomienda al sector oficial la participación en la promoción de la salud en niños y niñas bajo el esquema del presente estudio en países en desarrollo.

Abstract Introduction Participatory Research (PR) is a tool that can be approached for the analysis of sociocultural, environmental, and public health processes. The participation of school-age childrens in the appropriation of knowledge for the prevention of Chagas' Disease (CD) can break the cycle of transmission. CD is a public health problem that mainly affects rural endemic communities of developing countries. Objective To develop a strategy for the acquisition and transfer of new knowledge in childs, due to the lack of information about the transmission cycle of the EC. Materials and Methods A cross-sectional study was carried out with a group of 48 childrens from a community in extreme poverty in Yucatan, Mexico. Through PR tools and with the support of parents, ejidal and school authorities, educational workshops were given to children of the basic education to know the cycle of transmission, and to prevent CD due to the abundance of the vector in the study area. A program called "Small Investigators" was implemented to initiate processes of appropriation and socialization of knowledge in the community. Results The new knowledge acquired by the group of children was used and disseminated to their families, partners, and social circles, promoting the prevention of the disease. 182 triatomas were collected at home and peri domicile. Conclusions The new knowledge, attitudes and practices acquired by children under participation schemes is beneficial for the prevention of the Chagas Disease. The official sector is recommended to design the promotion health programs in children under the scheme of the present study in developing countries.

The opossum Didelphis virginiana as a synanthropic reservoir of Trypanosoma cruzi in Dzidzilché, Yucatán, México.

In México, the role of mammals in the transmission cycle of Trypanosoma cruzi is poorly known. In the State of Yucatán, an endemic area of Chagas disease, both Didelphis virginiana and D. marsupialis occur sympatrically. However, until now, only the former species had been found infected with T. cruzi. To evaluate the role of D. virginiana in a peridomestic transmission, nine periods of capture-recapture were performed around the village of Dzidzilché, Yucatán. The sex, age, reproductive status, location, and presence of infection with T. cruzi were recorded for each opossum. The chromosome morphology was used to identify the opossum species. T. cruzi was identified by the presence of pseudocysts of amastigotes in cardiac muscle fibers of Balb/c mice inoculated with strains isolated from opossums. However, xenodiagnosis was the best diagnostic method. Triatoma dimidiata, the vector, were collected in and around the opossums' nests, and human dwellings; and were checked for T. cruzi. From 102 blood samples of D. virginiana examined 55 (53.9%) were positive to T. cruzi, the only two D. marsupialis captured were negative. Significant differences were found between infection, and both sex and reproductive condition. Eight out of 14 triatomines collected in peridomestic nests (57.1%), and 32 of 197 captured inside houses (16.3%) were found infected, suggesting a peridomestic transmission. The statistically high abundance of infected opossums and triatomines during the dry season (March to May) suggested the existence of a seasonality in the peridomestic transmission of T. cruzi in Dzidzilché.

The opossum Didelphis virginiana as a synanthropic reservoir of Trypanosoma cruzi in Dzidzilché, Yucatán, México

In México, the role of mammals in the transmission cycle of Trypanosoma cruzi is poorly known. In the State of Yucatán, an endemic area of Chagas disease, both Didelphis virginiana and D. marsupialis occur sympatrically. However, until now, only the former species had been found infected with T. cruzi. To evaluate the role of D. virginiana in a peridomestic transmission, nine periods of capture-recapture were performed around the village of Dzidzilché, Yucatán. The sex, age, reproductive status, location, and presence of infection with T. cruzi were recorded for each opossum. The chromosome morphology was used to identify the opossum species. T. cruzi was identified by the presence of pseudocysts of amastigotes in cardiac muscle fibers of Balb/c mice inoculated with strains isolated from opossums. However, xenodiagnosis was the best diagnostic method. Triatoma dimidiata, the vector, were collected in and around the opossums' nests, and human dwellings; and were checked for T. cruzi. From 102 blood samples of D. virginiana examined 55 (53.9 percent) were positive to T. cruzi, the only two D. marsupialis captured were negative. Significant differences were found between infection, and both sex and reproductive condition. Eight out of 14 triatomines collected in peridomestic nests (57.1 percent), and 32 of 197 captured inside houses (16.3 percent) were found infected, suggesting a peridomestic transmission. The statistically high abundance of infected opossums and triatomines during the dry season (March to May) suggested the existence of a seasonality in the peridomestic transmission of T. cruzi in Dzidzilché