Transmission dynamics of an iridescent virus in an experimental mosquito population: the role of host density.

1. The transmission of insect pathogens cannot be adequately described by direct linear functions of host and pathogen density due to heterogeneity generated from behavioural or physiological traits, or from the spatial distribution of pathogen particles. Invertebrate iridescent viruses (IIVs) can cause patent and lethal infection or a covert sub-lethal infection in insects. Aedes aegypti larvae were exposed to suspensions of IIV type 6 at two densities. High larval density increased the prevalence of aggression resulting in potentially fatal wounding. 2. The overall prevalence of infection (patent + covert) was positively influenced by host density and increased with exposure time in both densities. The survival time of patently infected insects was extended by ≈ 5 days compared with non-infected insects. 3. Maximum likelihood models based on the binomial distribution were fitted to empirical results. A model incorporating heterogeneity in host susceptibility by inclusion of a pathogen-free refuge was a significantly better fit to data than an all-susceptible model, indicating that transmission is non-linear. The transmission coefficient (υ) did not differ with host density whereas the faction of the population that occupied the pathogen-free refuge (ΠR) was significantly reduced at high host density compared with the low density treatment. 4. The transmission of free-living infective stages of an IIV in Ae. aegypti larvae is non-linear, probably because of density-related changes in the frequency of aggressive encounters between hosts. This alters host susceptibility to infection and effectively reduces the proportion of hosts that occupy the pathogen-free refuge

Cultura y sociedad en movimiento

La presente compilación de textos, que aborda temáticas diversas sobre cultura y sociedad, es corolario de un esfuerzo compartido de profesores investigadores y alumnos de licenciatura y posgrado con el fin de dar a conocer resultados de las investigaciones que se están realizando en el organismo académico, incluyendo, por supuesto, otros trabajos llevados a cabo por colegas de instituciones y disciplinas afines; de esta manera se fortalecen los cuerpos académicos y se promueven las líneas de generación y aplicación del conocimiento de éstos, evidenciando algunos campos de conocimiento de la antropología.Como es manifiesto, la obra en su conjunto aborda distintos temas desde diversas perspectivas epistemológicas y teórico-conceptuales. Constituye un trabajo plural que articula la perspectiva antropológica, con otras lentes disciplinares. Cuerpo, agricultura, desigualdad y bienestar se entrelazan como ejes en principio divergentes, que hallan en lo sociocultural un elemento común de análisis. Así, los textos aquí englobados tienen la expectativa de aportar en la discusión contemporánea de viejos y nuevos derroteros de interés antropológico, y social en general

Evolving trends in the management of acute appendicitis during COVID-19 waves. The ACIE appy II study

Background: In 2020, ACIE Appy study showed that COVID-19 pandemic heavily affected the management of patients with acute appendicitis (AA) worldwide, with an increased rate of non-operative management (NOM) strategies and a trend toward open surgery due to concern of virus transmission by laparoscopy and controversial recommendations on this issue. The aim of this study was to survey again the same group of surgeons to assess if any difference in management attitudes of AA had occurred in the later stages of the outbreak. Methods: From August 15 to September 30, 2021, an online questionnaire was sent to all 709 participants of the ACIE Appy study. The questionnaire included questions on personal protective equipment (PPE), local policies and screening for SARS-CoV-2 infection, NOM, surgical approach and disease presentations in 2021. The results were compared with the results from the previous study. Results: A total of 476 answers were collected (response rate 67.1%). Screening policies were significatively improved with most patients screened regardless of symptoms (89.5% vs. 37.4%) with PCR and antigenic test as the preferred test (74.1% vs. 26.3%). More patients tested positive before surgery and commercial systems were the preferred ones to filter smoke plumes during laparoscopy. Laparoscopic appendicectomy was the first option in the treatment of AA, with a declined use of NOM. Conclusion: Management of AA has improved in the last waves of pandemic. Increased evidence regarding SARS-COV-2 infection along with a timely healthcare systems response has been translated into tailored attitudes and a better care for patients with AA worldwide

Biological variation in two Anopheles vestitipennis populations with different feeding preferences in Southern Mexico.

The lengths of gonotrophic cycle and egg development and survival rate were studied in Anopheles vestitipennis collected in horse and human-baited traps in southern Mexico. The gonotrophic cycle duration was estimated using cross-correlation analysis, whereas the survival rate was assessed using a vertical method. Daily changes of parity rates gave significant correlation indices at 3 and 4 days in the zoophilic and anthro-pophilic populations, respectively. The minimum time required to develop mature eggs after blood feeding was 54 and 60 h, and the survival rate was 0.93 and 0.88 in zoophilic and anthropophilic female mosquito populations, respectively. These biological differences provide additional support for the existence of subpopulations with distinctive feeding preferences within An. vestitipennis in southern Mexico

Adverse effects of covert iridovirus infection on life history and demographic parameters of Aedes aegypti.

Sublethal viral infections can cause changes in the body size and demography of insect vectors, with important consequences for population dynamics and the probability that individual mosquitoes will transmit disease. This study examined the effects of covert (sublethal) infection by Invertebrate iridescent virus 6 (IIV-6) on the demography of female Aedes aegypti and the relationship between key life history parameters in covertly infected female insects compared with healthy ( control) insects or non-infected mosquitoes that had survived exposure to virus inoculum without becoming infected. Of the female mosquitoes that emerged following exposure to virus inoculum and were offered blood meals, 29% (43/150) proved positive for covert IIV-6 infection. The net reproductive rate ( R 0) of covertly infected females was 50% lower for infected females compared to control mosquitoes, whereas non-infected exposed females had an R 0 approximately 15% lower than that of controls. Reproduction caused a significant decrease of about 13 days in mosquito longevity compared to females that did not reproduce (P < 0.001). Infected females lived 5-8 days less than non-infected exposed females or controls, respectively (P = 0.028). Infected females and non-infected exposed females both had significantly shorter wings than control insects ( P < 0.001). There was a significant positive correlation between wing length and longevity in covertly infected female mosquitoes but not in control or non-infected exposed mosquitoes. Longer lived females produced more eggs in all treatments. There were no significant correlations between body size and fecundity or the production of offspring. There was also no correlation between fecundity and fertility, suggesting that sperm inactivation was a more likely cause of decreased fertility in older mosquitoes than sperm depletion. We conclude that covert infection by iridescent virus is likely to reduce the vectorial capacity of this mosquito

Mark-recapture studies of host selection by Anopheles (Anopheles) vestitipennis.

We present herein the results of a series of mark-recapture experiments with female Anopheles vestitipennis. Theses experiments used human and animal hosts to assess the degree of anthropophily of field-caught specimens, originally collected on either host, and of their offspring. Fidelity of mosquitoes to particular hosts was estimated by recapturing marked host-seeking mosquitoes returning for a 2nd blood meal. Results indicated that mosquitoes seeking animal hosts were more faithful (80.48%; 33 of 41) in returning to their original host than were those seeking human hosts (63%; 49 of 78)