Morphological and molecular characterization of Trichuris muris (Nematoda: Trichuridae): studies from two commensal rodent species.

In this paper we re-describe Trichuris muris based on morphological data following isolation from two commensal rodent species, Mus musculus from Mexico and Rattus rattus from Argentina. Furthermore, we provide a molecular characterization based on mitochondrial (cytochrome c oxidase subunit 1 mitochondrial gene) and nuclear (internal transcribed spacer 2 region) markers in order to support the taxonomic identification of the studied specimens of T. muris from M. musculus. We distinguished T. muris from 29 species of Trichuris found in American rodents based on morphological and biometrical features, such as the presence of a spicular tube, length of spicule, size of proximal and distal cloacal tube and non-protrusive vulva. We suggest that spicular tube patterns can be used to classify Trichuris species in three groups. Considering that the diagnosis among the species of this genus is mainly based on morphometry, this proposal represents a relevant contribution. We provide molecular studies on two markers, making this the first contribution for T. muris in the Americas. This study makes an important contribution to the integrative taxonomy of cosmopolitan nematode species, and its correct determination from the parasitological study of commensal rodents.

Patterns of helminth infections in Rattus rattus and Mus musculus from two Mayan communities in Mexico.

The black rat Rattus rattus and the house mouse Mus musculus are two commensal rodent species that harbour and shed zoonotic pathogens, including helminths. The aim of this survey was to study the helminth community and the patterns of infections in R. rattus and M. musculus from two Mayan communities in Mexico. Gastrointestinal helminths were isolated from 322 M. musculus and 124 R. rattus, including Gongylonema neoplasticum, Hassalstrongylus aduncus, Hassalstrongylus musculi, Hydatigera taeniaeformis metacestode, Hymenolepis diminuta, Nippostrongylus brasiliensis, Oligacanthorhynchidae gen. sp., Syphacia muris, Syphacia obvelata, Rodentolepis microstoma and Trichuris muris. The overall richness of helminths was seven in R. rattus and six in M. musculus. The results of generalized linear models showed that juvenile rodents had lower probabilities of being infected with G. neoplasticum, H. taeniaeformis and H. musculi than adult rodents. A positive association between the prevalence of S. muris and rat abundance was found. The intensity of infection with S. muris was higher in the rainy season than in the dry season; the opposite result was found for H. musculi infection. Male R. rattus harboured more S. muris specimens. The intensity of infection with T. muris was inversely associated with mouse abundance. The presence of the zoonotic H. diminuta, as well as H. taeniaeformis and R. microstoma in rodent populations indicates that there is risk of transmission, and that their entire life cycle occurs in the study area.

Discovering mental models and frames in learning of nursing ethics through simulations.

The acquisition of ethical competence is necessary in nursing. The aims of the study were to analyse students' perceptions of the process of learning ethics through simulations and to describe the underlying frames that inform the decision making process of nursing students. A qualitative study based on the analysis of simulated experiences and debriefings of six simulated scenarios with ethical content in three different groups of fourth-year nursing students (n = 30), was performed. The simulated situations were designed to contain ethical dilemmas. The students' perspective regarding their learning and acquisition of ethical competence through simulations was positive. A total of 15 mental models were identified that underlie the ethical decision making of the students. The student's opinions reinforce the use of simulations as a tool for learning ethics. Thus, the putting into practice the knowledge regarding the frames that guide ethical actions is a suitable pedagogical strategy.

Hymenolepis diminuta and Rodentolepis nana (Hymenolepididae: Cyclophyllidea) in urban rodents of Gran La Plata: association with socio-environmental conditions.

The aim of this survey was to study two Hymenolepididae species in urban rodents, Rattus rattus and Rattus norvegicus, and to analyse factors that favour their presence in the environment and pose a sanitary risk. Hymenolepis diminuta and Rodentolepis nana were found in R. rattus and R. norvegicus in different proportions. Values of prevalence, mean abundance and mean intensity were recorded, and new morphometric characters were described, adding to previously known information. No significant differences were found. However, the results revealed that there is a tendency for these parasites to develop in areas with deficient socio-structural conditions and in water bodies. This study thereby shows that certain areas on the periphery of the Gran La Plata favour the existence of rodents, which act as sentinels of zoonotic diseases, and stresses the need to take action to minimize them in order to avoid putting human and animal health at risk.

A survey of zoonotic pathogens carried by house mouse and black rat populations in Yucatan, Mexico.

The house mouse (Mus musculus) and the black rat (Rattus rattus) are reservoir hosts for zoonotic pathogens, several of which cause neglected tropical diseases (NTDs). Studies of the prevalence of these NTD-causing zoonotic pathogens, in house mice and black rats from tropical residential areas are scarce. Three hundred and two house mice and 161 black rats were trapped in 2013 from two urban neighbourhoods and a rural village in Yucatan, Mexico, and subsequently tested for Trypanosoma cruzi, Hymenolepis diminuta and Leptospira interrogans. Using the polymerase chain reaction we detected T. cruzi DNA in the hearts of 4·9% (8/165) and 6·2% (7/113) of house mice and black rats, respectively. We applied the sedimentation technique to detect eggs of H. diminuta in 0·5% (1/182) and 14·2% (15/106) of house mice and black rats, respectively. Through the immunofluorescent imprint method, L. interrogans was identified in 0·9% (1/106) of rat kidney impressions. Our results suggest that the black rat could be an important reservoir for T. cruzi and H. diminuta in the studied sites. Further studies examining seasonal and geographical patterns could increase our knowledge on the epidemiology of these pathogens in Mexico and the risk to public health posed by rodents.

Infection levels of intestinal helminths in two commensal rodent species from rural households in Yucatan, Mexico.

The aim of the present study was to calculate the prevalence and intensity of intestinal helminths in the house mouse (Mus musculus) and the black rat (Rattus rattus) trapped in rural households of Yucatan, Mexico. Sampling was conducted during the rainy season from October to December 2011 and the dry season from January to March 2012. A total of 154 M. musculus and 46 R. rattus were examined, with 84.2% of M. musculus being infected with helminths compared with a significantly lower prevalence of 52.2% in R. rattus (P< 0.01). Adult M. musculus were more likely to be infected with helminths (89%) than subadults (63%) (P< 0.01). Four helminth species were identified: Taenia taeniaeformis larvae, Nippostrongylus brasiliensis, Syphacia muris and Trichuris muris. Nippostrongylus brasiliensis was present more frequently in M. musculus than in R. rattus (P< 0.01) and in adult mice compared to subadults (P< 0.01). Trichuris muris was present only in adult mice. This is the first report of N. brasiliensis, S. muris and T. muris in Yucatan, Mexico, as well as the first to report the presence of N. brasiliensis in M. musculus from Mexico. The helminth fauna of commensal rodents present in households appears to constitute a low potential health risk to local inhabitants; however, it would be advisable to conduct further studies to better understand the public health risk posed by these rodent intestinal helminths.

Evidence of a direct projection of the vomeronasal organ to the medial preoptic nucleus and hypothalamus.

In rodents the vomeronasal system plays an important role in modulating the hypothalamic control of gonadotropin secretion. It is accepted that the anatomical pathways by which the vomeronasal organ influences the neuroendocrine aspects of the reproductive behavior involves a polysynaptic system, including the accessory olfactory bulb, the 'vomeronasal amygdala', the bed nucleus of the stria terminalis and medial preoptic and ventromedial hypothalamic nuclei. We found that 72 h after unilateral transection of the vomeronasal nerves of an ipsilateral orthograde degeneration is seen in the neuropil of the medial preoptic, ventromedial, and arcuate hypothalamic nuclei. This represents an anatomical evidence of a monosynaptic link between the vomeronasal neuroepithelium and the medial preoptic nucleus, and hypothalamus.