Filling the knowledge gap of Middle American freshwater fish parasite biodiversity: metazoan parasite fauna of Nicaragua.

The heterogeneous landscape of Nicaragua harbours a large diversity of freshwater fishes. The great Nicaraguan lakes, Managua and Nicaragua, and several adjacent crater lakes harbour numerous endemic fish species. However, information about their parasite fauna is still fragmentary. Here, we surveyed the great Nicaraguan lakes and four crater lakes and provide data for 17 metazoan parasite taxa infecting seven fish host species. We also gathered all the published records from the literature on the parasites reported from Nicaraguan freshwater fishes, as well as those for Costa Rica and Panama to discuss the region of Lower Central America as a whole. With this information we built a parasite-host and a host-parasite checklist. With data from near 50% of the native and endemic freshwater fishes in Nicaragua, the parasite fauna comprises 101 taxa in 51 fish species allocated in 11 families. Cichlids are the most diverse group of fishes in this region and have been the most extensively surveyed for their metazoan parasites. Helminths are the best-represented groups of metazoan parasites, with 42 trematodes, five cestodes, 24 monogeneans, two acanthocephalans, 20 nematodes and one hirudinean. Additionally, freshwater fishes are parasitized by copepods, branchiurans and oribatid mites. Even though the inventory is not yet complete, the patterns of diversity uncovered revealed promising information about the origin, biogeography and evolutionary history of the Nicaraguan freshwater fish parasite fauna. More studies are necessary to complete our knowledge about the diversity, host association and distribution of metazoan parasites in Nicaragua and other Central American countries.

Diversity of Rhabdochona mexicana (Nematoda: Rhabdochonidae), a parasite of Astyanax spp. (Characidae) in Mexico and Guatemala, using mitochondrial and nuclear genes, with the description of a new species.

Among fish parasitic nematodes Rhabdochona is one of the most speciose genera, with c. 100 species. Twelve congeneric species occur in Mexican freshwater fishes, in a region located between the Nearctic and Neotropical biogeographical regions. Host association and biogeographical history have determined the high species richness of Rhabdochona in Mexico. One of these species, Rhabdochona mexicana, is highly specific to the characid genus Astyanax. Characids are a group of freshwater fish with Neotropical affinity. In this paper, we explore the genetic diversity of R. mexicana through samples obtained from populations of Astyanax spp. across river basins of Mexico and Guatemala. Sequences of one mitochondrial and two ribosomal genes were obtained from 38 individuals and analysed using Maximum Likelihood and Bayesian Inference analysis. Phylogenetic analyses using cox1, and a concatenated alignment of 18S + 28S + cox1 recovered two genetic lineages. One of them corresponded with R. mexicana sensu stricto; this lineage included three reciprocally monophyletic subgroups; the other lineage was highly divergent and represented a putative candidate species. A detailed morphological study was conducted to corroborate the molecular findings. We describe a new species herein and discuss the implications of using molecular tools to increase our knowledge about the diversity of a speciose genus such as Rhabdochona.

Microencapsulated feruloyl esterase-producing lactobacilli ameliorate lipid profile and glycaemia in high fat diet-induced obese mice.

The effect of oral administration of spray-dried microcapsules of feruloyl esterase (FE) producing Lactobacillus fermentum CRL1446 (Lf) and Lactobacillus johnsonii CRL1231 (Lj) on high fat diet-induced obese mice was investigated to evaluate whether these strains could be used as a biotherapeutic for obesity. Swiss albino mice were divided into a normal diet fed group receiving empty microcapsules (control), a high fat diet plus empty microcapsules (HFD group), HFD plus microcapsules with Lf (HFD-Lf group) and HDF plus microcapsules with Lj (HFD-Lj group). Microcapsules containing Lf or Lj at a dose of ~107 cells/day/mouse were given orally for 7 weeks. Body weight gain, adiposity index, plasma leptin, lipid profiles, glycaemia, insulinemia, oral glucose tolerance, intestinal FE, glutathione peroxidase and glutathione reductase (GR) activities were determined. Administration of lactobacilli (HFD-Lf and HFD-Lj groups) improved metabolic parameters (triglyceride, total cholesterol, low-density lipoprotein cholesterol levels) and cardiovascular risk indicators (37-46% decrease of atherogenic index), and reduced body weight gain (29-38%), adiposity index (42-62%), plasma leptin levels, liver weight and fat deposition in liver. Intestinal FE activities significantly increased in HFD-Lf (62%) and HFD-Lj group (48%), thus improving hepatic GR activity (42% increment) compared to HFD group. Moreover, L. johnsonii increased HDL-cholesterol and L. fermentum reduced blood glucose to levels similar to the control. These FE-producing lactobacilli have the potential to improve biomarkers involved in obesity by increasing intestinal FE activity.

Models for experimental infection of dogs fed with tissue from fetuses and neonatal cattle naturally infected with Neospora caninum.

Three models were designed to investigate the development and enteroepithelial phase of Neospora caninum in dogs, and to induce oocyst production by the parasite. In the first model, three dogs were fed raw fetal bovine tissue on two occasions. The bovine fetal tissue had been stored at 4 degrees C for 14 days and 16 days, respectively, and had tested positive for neosporosis using histopathology and immunohistochemistry. In the second model, nine dogs from the beginning of the experiment until euthanasia were fed portions of tissue from bovine fetuses that been stored at 4 degrees C for between 1 and 2 days. Three fetuses had tested positive for neosporosis using histopathology and immunohistochemistry. In the third model, three dogs were fed pieces of raw tissue from two neonatal calves that had not received colostrum, and which had tested positive for antibodies against N. caninum. The brains of these calves were positive for neosporosis by histopathology and immunohistochemistry. In all three models, none of the dogs excreted oocysts of N. caninum, developed intestinal parasites or seroconverted.