Scanning electron microscopic observations of adult Baylisascaris procyonis (Nematoda)

Morphology and ASAP analysis of the important zoonotic nematode parasite Baylisascaris procyonis (Stefahski and Zarnowski, 1951), with molecular phylogenetic relationships of Baylisascaris species (Nematoda: Ascaridida)

Species of Baylisascaris (Nematoda: Ascarididae) are of great veterinary and zoonotic significance, owing to cause Baylisascariosis or Baylisascariasis in wildlife, captive animals and humans. However, the phylogenetic relationships of the current 10 Baylisascaris species remain unclear. Moreover, our current knowledge of the detailed morphology and morphometrics of the important zoonotic species B. procyonis is still insufficient. The taxonomical status of B. procyonis and B. columnaris remains under debate. In the present study, the detailed morphology of B. procyonis was studied using light and scanning electron microscopy based on newly collected specimens from the raccoon Procyon lotor (Linnaeus) in China. The results of the ASAP analysis and Bayesian inference (BI) using the 28S, ITS, cox1 and cox2 genetic markers did not support that B. procyonis and B. columnaris represent two distinct species. Integrative morphological and molecular assessment challenged the validity of B. procyonis, and suggested that B. procyonis seems to represent a synonym of B. columnaris. Molecular phylogenetic results indicated that the species of Baylisascaris were grouped into 4 clades according to their host specificity. The present study provided new insights into the taxonomic status of B. procyonis and preliminarily clarified the phylogenetic relationships of Baylisascaris species.

Prevalence of Baylisascaris procyonis in Raccoons Trapped in New Orleans, Louisiana, 2014-2017

Baylisascaris procyonis, the raccoon roundworm, is considered an emerging zoonotic disease in the United States after being identified in raccoons captured in different US regions and metropolitan areas. Humans can become infected with B. procyonis after ingesting mature roundworm eggs, sometimes resulting in fatal disease or severe sequelae in these patients. The first reported human Baylisascaris case in New Orleans raised concerns that very little was known about this zoonotic disease in the increasing urban raccoon population. Therefore, the study aim was to estimate the prevalence of Baylisascaris-infected raccoons in New Orleans, LA. Raccoons were trapped based on nuisance calls from the public and in areas where raccoons had been sighted. Necropsies were performed to identify B. procyonis adult worms in intestines and fecal samples were examined for roundworm ova. Study findings showed that 38.5% of New Orleans raccoons were infected with B. procyonis, defined by the presence of adult B. procyonis worms or Baylisascaris ova in their feces. Twenty-four of 65 raccoons (36.9%) had raccoon roundworms in their intestines and 31.7% of the fecal samples were positive for B. procyonis eggs. Mapping B. procyonis-infected raccoons by trapping location showed that infected raccoons were found throughout the city. In conclusion, the high prevalence rate of B. procyonis in New Orleans raccoons demonstrates the importance of educating the public and health care professionals about potential health risks and providing resources to prevent exposure to infective eggs from raccoon latrines. Furthermore, this emerging disease should be further studied to examine human risk of infection in increasing raccoon populations in metropolitan areas.

Baylisascaris potosis n. sp., a new ascarid nematode isolated from captive kinkajou, Potos flavus, from the Cooperative Republic of Guyana

We describe a new nematode species, Baylisascaris potosis n. sp., isolated from captive kinkajou, Potos flavus, from the Cooperative Republic of Guyana. The nematode was found in fecal specimens, identified morphologically, and confirmed genetically. The new species is similar to Baylisascaris procyonis, Baylisascaris columnaris, and other Baylisascaris species, but is distinguished by the position of the male phasmidial pole. Nuclear and mitochondrial DNA sequence analyses confirmed that the new species is phylogenetically distinct from all the members of the genus Baylisascaris, and groups with B. procyonis and B. columnaris. This nematode is the 10th species assigned to the genus Baylisascaris.

Ribosomal DNA and phylogeny of the Ascaridoidea (Nemata: Secernentea): implications for morphological evolution and classification

Nematodes of the superfamily Ascaridoidea are parasites of the alimentary tract of vertebrates and include species that are of medical and economic importance. Existing evolutionary hypotheses for these organisms have frequently been based on interpretation of one or few "key" structural or life history features. We used nuclear-encoded small (1764 characters) and large subunit (757 characters) ribosomal DNA sequences to estimate the phylogeny of representative taxa from this superfamily. Trees inferred by maximum parsimony and maximum likelihood methods strongly support clades that are primarily consistent with one recent classification of the group. In contrast, most previously proposed phylogenetic hypotheses were significantly worse when compared to the maximum likelihood tree by a statistical method. Hypotheses for the evolution of morphological and life history characters were explored by parsimony mapping these features on several tree topologies, including optimal molecular trees and alternative topologies reflecting traditional expectations deemed not worse in statistical tests. The results identify some consistent putative shared-derived morphological features, but also strongly suggest that some key features emphasized by previous workers represent ancestral states or highly homoplastic characters.