Calomys callosus: An Experimental Animal Model Applied to Parasitic Diseases Investigations of Public Health Concern

A simple and low-cost environmental enrichment program improves the welfare of Calomys callosus, a species that adapts to animal facilities

An environmental enrichment protocol is essential for testing experimental models because it upholds animal welfare, aligns with ethical principles in animal experimentation, and reduces the number of animals needed. Calomys callosus, a South American rodent from the Cricetidae family, is bred in rodent animal facilities for its ease of handling, longevity, prolificacy, and effectively mimicking diseases like Toxoplasmosis, Leishmaniasis, Chagas, and Schistosomiasis. There are no reports on environmental enrichments for this species or their impact on reproductive parameters. This study aimed to analyze the influence of the Environmental Enrichment Program (EEP) on the reproductive and zootechnical performance of C. callosus kept in the Rodents Animal Facilities Complex of Universidade Federal de Uberlândia (UFU). Two experimental groups were established: with environmental enrichment EE+ and without environmental enrichment EE-. The materials used in the experimental design were changed weekly and alternated between dietary, occupational, physical/cognitive, and non-enrichment items. After the inclusion of the EEP, an improvement in the reproductive indices of C. callosus was identified in the EE+ group. These improvements included increased female precocity, a decreased interbirth interval, and a higher number of pairs producing more offspring. The postpartum zootechnical indices were also better, such as the number of animals born alive, improved weaning rates, and a reduced average number of deaths from birth to weaning. After the inclusion of the EEP, the general health status of C. callosus improved, reducing cases of non-infectious lumbar alopecia. Therefore, EEP allows C. callosus to express natural reproductive behaviors and improves parental care.

Phylogenetic and biogeographical traits predict unrecognized hosts of zoonotic leishmaniasis

The spatio-temporal distribution of leishmaniasis, a parasitic vector-borne zoonotic disease, is significantly impacted by land-use change and climate warming in the Americas. However, predicting and containing outbreaks is challenging as the zoonotic Leishmania system is highly complex: leishmaniasis (visceral, cutaneous and muco-cutaneous) in humans is caused by up to 14 different Leishmania species, and the parasite is transmitted by dozens of sandfly species and is known to infect almost twice as many wildlife species. Despite the already broad known host range, new hosts are discovered almost annually and Leishmania transmission to humans occurs in absence of a known host. As such, the full range of Leishmania hosts is undetermined, inhibiting the use of ecological interventions to limit pathogen spread and the ability to accurately predict the impact of global change on disease risk. Here, we employed a machine learning approach to generate trait profiles of known zoonotic Leishmania wildlife hosts (mammals that are naturally exposed and susceptible to infection) and used trait-profiles of known hosts to identify potentially unrecognized hosts. We found that biogeography, phylogenetic distance, and study effort best predicted Leishmania host status. Traits associated with global change, such as agricultural land-cover, urban land-cover, and climate, were among the top predictors of host status. Most notably, our analysis suggested that zoonotic Leishmania hosts are significantly undersampled, as our model predicted just as many unrecognized hosts as unknown hosts. Overall, our analysis facilitates targeted surveillance strategies and improved understanding of the impact of environmental change on local transmission cycles.

The trophoblast giant cells of cricetid rodents

Giant cells are a prominent feature of placentation in cricetid rodents. Once thought to be maternal in origin, they are now known to be trophoblast giant cells (TGCs). The large size of cricetid TGCs and their nuclei reflects a high degree of polyploidy. While some TGCs are found at fixed locations, others migrate throughout the placenta and deep into the uterus where they sometimes survive postpartum. Herein, we review the distribution of TGCs in the placenta of cricetids, including our own data from the New World subfamily Sigmodontinae, and attempt a comparison between the TGCs of cricetid and murid rodents. In both families, parietal TGCs are found in the parietal yolk sac and as a layer between the junctional zone and decidua. In cricetids alone, large numbers of TGCs, likely from the same lineage, accumulate at the edge of the placental disk. Common to murids and cricetids is a haemotrichorial placental barrier where the maternal-facing layer consists of cytotrophoblasts characterized as sinusoidal TGCs. The maternal channels of the labyrinth are supplied by trophoblast-lined canals. Whereas in the mouse these are lined largely by canal TGCs, in cricetids canal TGCs are interspersed with syncytiotrophoblast. Transformation of the uterine spiral arteries occurs in both murids and cricetids and spiral artery TGCs line segments of the arteries that have lost their endothelium and smooth muscle. Since polyploidization of TGCs can amplify selective genomic regions required for specific functions, we argue that the TGCs of cricetids deserve further study and suggest avenues for future research.

Neuroprotective Treatments for Digestive Forms of Chagas Disease in Experimental Models: A Systematic Review

Chagas disease is an anthropozoonosis caused by the protozoan Trypanosoma cruzi and is characterized as a neglected disease. It is currently endemic in 21 countries on the Latin American continent, including Bolivia, Argentina, and Paraguay. Unfortunately, there are no optimally effective treatments that can reduce the damage caused in the digestive form of the disease, such as the neuronal destruction of the myenteric plexus of both the esophagus and the colon. Therefore, the objective of this systematic review was to report the possible pharmacological neuroprotective agents that were tested in murine models of the digestive form of Chagas disease. Inclusion criteria are in vivo experimental studies that used different murine models for digestive forms of Chagas disease related to pharmacological interventions with neuroprotective potential, without year and language restriction. On the other hand, the exclusion criteria were studies that did not approach murine models with the digestive form of the disease or did not use neuroprotective treatments, among others. The search in the PubMed, Web of Science, Embase, and LILACS databases was performed on September 4, 2021. In addition, a manual search was performed using the references of the included articles. The risk of bias assessment of the studies was performed based on the SYRCLE tool guidelines, and the data from the selected articles are presented in this review as a narrative description and in tables. Eight articles were included, 4 of which addressed treatment with acetylsalicylic acid, 3 with cyclophosphamide, and 1 with Lycopodium clavatum 13c. In view of the results of the studies, most of them show neuroprotective activity of the treatments, with the potential to reduce the number of damaged neurons, as well as positive changes in the structure of these cells. However, more studies are needed to understand the mechanisms triggered by each drug, as well as their safety and immunogenicity. Systematic review registration is as follows: PROSPERO database (CRD42022289746).