Susceptibility of Sphenarium purpurascens purpurascens (Orthoptera: Pyrgomorphidae) instars to a commercial strain of Metarhizium acridum (Hypocreales: Clavicipitaceae) in Michoacan, Mexico.

The objective of this study was to evaluate the performance of a commercial strain of the entomopathogenic fungi Metarhizium acridum, on the different instars of the grasshopper pest Sphenarium purpurascens purpurascens, as well as its sporulation via bioassays under laboratory conditions, in Michoacan, Mexico. The most susceptible instars were nymphs one, two and four, with an average survival time of less than 6.91 days. The least susceptible was the adult, with a survival time of 8.36 days. The instars with the highest post mortem sporulation were nymphs one, two and three. A moderate negative association was registered between S. p. purpurascens and the sporulation of M. acridum, in advanced instars (nymph 4 and adult), in which sporulation was lower compared to early instars. All instars showed survival rates below 5 %, so M. acridum can be considered to be a viable option for controlling this pest in the field

Primer registro de megaselia sp. (diptera: phoridae) como parasitoide de sphenarium purpurascens purpurascens (orthoptera: pyrgomorphidae)

The presence of a Megaselia species parasitizing Sphenarium purpurascens purpurascens is documented for the first time. Some data on its biology are included from specimens collected in maize agroecosystems in the municipality of Erongarícuaro, Michoacan, Mexico.RESUMEN. Se documenta por primera vez la presencia de especiesde Megaselia parasitando a Sphenarium purpurascens purpurascens. Se incluyen algunos datos de su biología desde especímenes colectados en agroecosistemas de maíz en la comunidad de Erongarícuaro, Michoacán, México.

CHICKEN COOPS, Triatoma dimidiata INFESTATION AND ITS INFECTION WITH Trypanosoma cruzi IN A RURAL VILLAGE OF YUCATAN, MEXICO

This study longitudinally investigated the association between Triatoma dimidiata infestation, triatomine infection with Trypanosoma cruzi and household/backyard environmental characteristics in 101 homesteads in Molas and Yucatan, Mexico, between November 2009 (rainy season) and May 2010 (dry season). Logistic regression models tested the associations between insect infestation/infection and potential household-level risk factors. A total of 200 T. dimidiata were collected from 35.6% of the homesteads, mostly (73%) from the peridomicile. Of all the insects collected, 48% were infected with T. cruzi. Infected insects were collected in 31.6% of the homesteads (54.1% and 45.9% intra- and peridomiciliary, respectively). Approximately 30% of all triatomines collected were found in chicken coops. The presence of a chicken coop in the backyard of a homestead was significantly associated with both the odds of finding T. dimidiata (OR = 4.10, CI 95% = 1.61-10.43, p = 0.003) and the presence of triatomines infected with T. cruzi (OR = 3.37, CI 95% = 1.36-8.33, p = 0.006). The results of this study emphasize the relevance of chicken coops as a putative source of T. dimidiata populations and a potential risk for T. cruzi transmission

Population and Environmental Correlates of Maize Yields in Mesoamerica: a Test of Boserup’s Hypothesis in the Milpa

Using a sample of 40 sources reporting milpa and mucuna-intercropped maize yields in Mesoamerica, we test Boserup’s (1965) prediction that fallow is reduced as a result of growing population density. We further examine direct and indirect effects of population density on yield. We find only mixed support for Boserupian intensification. Fallow periods decrease slightly with increasing population density in this sample, but the relationship is weak. Controlling for other covariates, fallow-unadjusted maize yields first rise then fall with population density. Fallow-adjusted maize yields peak at 390 kg/ha/yr for low population densities (8 persons / km2) and decline to around 280 kg/ha/yr for the highest population densities observed in our dataset. Fallow practices do not appear to mediate the relationship between population density and yield. The multi-level modeling methods we adopt allow for data clustering, accurate estimates of group-level variation, and they generate conditional predictions, all features essential to the comparative study of prehistoric and contemporary agricultural yields

Prevalence, abundance and intensity of eggs and oocysts of gastrointestinal parasites in the opossum Didelphis virginiana Kerr, 1792 in Yucatan, Mexico

Virginia opossum, Didelphis virginiana, is a synanthropic mammal associated with peridomestic areas of Yucatán, However, little is known about the gastrointestinal parasite infections of this species. The infection prevalence, mean abundance and mean intensity of eggs and oocysts of gastrointestinal parasites, in opossums captured in the peridomestic areas were estimated in six rural localities of Yucatán, Mexico. Eighty-four faecal samples were processed by flotation technique. McMaster test was used to estimate the number of helminth eggs and protozoa oocysts per gram of feces. Seven genera of gastrointestinal parasites were identified, and then infection prevalence was estimated as follows: Protozoa Eimeria sp. (51.9 %) and Sarcocystis sp. (1 %); nematodes Ancylostoma sp. (80.56 %), Cruzia sp. (62.04 %), Trichuris sp. (60.19 %), Capillaria sp. (29.63 %), Turgida sp. (23.15 %), Toxocara sp. (11.11 %), and Ascaris sp. (1.85 %); and one acanthocephalan: Oligacanthorhynchus sp. (14.81 %). This is the first study on the diversity of gastrointestinal parasites in Virginia opossums, and first evidence about the potential role of opossums in the transmission of zoonotic gastrointestinal parasites in peridomestic areas of Yucatán, 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 gltAand 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

The biology of three Mexican-American species of Triatominae (Hemiptera: Reduviidae): Triatoma recurva, Triatoma protracta and Triatoma rubida

The values of biological parameters related to hatching, lifespan, the number of blood meals between moults, mortality, time lapse before the beginning of feeding, feeding time and defecation delay for each instar of three Mexican-American species of Triatominae, Triatoma recurva, Triatoma protracta (former subspecies protracta) and Triatoma rubida (former subspecies uhleri), were evaluated and compared. No significant (p > 0.05) differences were recorded among the three species with respect to the average time required to hatch. This time was approximately 19 days. The average egg-to-adult development time was significantly (p < 0.05) shorter for T. rubida. The number of blood meals at each nymphal instar varied from one-five for each species. The mortality rates were higher for the first-instar nymphs of the three species studied. The mean time lapse before the beginning of feeding was between 0.3-3 min for most nymphs of all instars of each species studied. The mean feeding time was the longest for T. recurva, followed by T. protracta. The defecation delay was less than 10 min for T. recurva and T. rubida. Given these results, only T. rubida should be considered an important potential vector of Trypanosoma cruzi transmission to humans in areas of Mexico where these species exist, whereas T. recurva and T. protracta would be of secondary importance