Ascarid infestation in captive Siberian tigers in China.

The Siberian tiger is endangered and is listed by the International Union for the Conservation of Nature; the captive environment is utilized to maintain Siberian tiger numbers. Little information regarding the prevalence of parasites in Siberian tigers is available. A total of 277 fecal samples of Siberian tigers were analyzed in this study. The microscopic analysis indicated the presence of ascarid eggs of Toxascaris leonina and Toxocara cati. The ascarid infection rate was 67.5% in Siberian tigers. The internal transcribed spacer-1 (ITS-1) phylogenetic analysis indicated that T. leonina belonged to Toxascaris and that Toxo. cati belonged to Toxocara. The infestation rate and intensity of T. leonina were higher than those of Toxo. cati. One-way analysis of variance showed that the presence of T. leonina was significantly associated with age (P<0.05). Temperature changes also influenced T. leonina and Toxo. cati infestation, and a rise in temperature caused an increase in the number of T. leonina and Toxo. cati eggs. This study provides a better understanding of ascarid infestation among the captive Siberian tigers and is helpful for the prevention of the spread of infectious parasitic diseases among other tigers in the zoo.

Further studies on Toxascaris leonina (Linstow, 1902) (Ascaridida: Ascarididae) from Felis lynx (Linnaeus) and Panthera leo (Linnaeus) (Carnivora: Felidae).

Toxascaris leonina (Linstow, 1902) is a most common intestinal parasite of various animals in Felidae and Canidae. In the present paper, light and scanning electron microscopy (SEM) were used to study the morphological aspects of adult worms of this nematode in detail, based on the material collected from Panthera leo (Linnaeus) and Felis lynx (Linnaeus) (Carnivora: Felidae) in China. The results showed that there were some morphometric differences between the present material and the previous studies, including the body size, the width and length of cervical alae, the number of denticles on each lip and the tail length of the female. Previously unreported morphological features were also revealed. These supplementary morphological and morphometric data contributed to a more accurate identification of this worldwide distributed ascarid nematode.

Diagnostic morphology of four larval ascaridoid nematodes that may cause visceral larva migrans: Toxascaris leonina, Baylisascaris procyonis, Lagochilascaris sprenti, and Hexametra leidyi.

The gross and histological morphology of the larvae of 4 ascaridoid nematodes, Toxascaris leonina, Baylisascaris procyonis, Lagochilascaris sprenti, and Hexametra leidyi, are described. The larvae of T. leonina, B. procyonis, and L. sprenti were recovered from experimentally infected mice at 32, 14, and 75 days of infection, respectively. Hexametra leidyi larvae used for morphological study were collected on day 159 postinfection from a rhesus monkey, Macaca mulatta, while H. leidyi larvae used for histological study were collected from mice when they had reached the same size as those found in the monkey, i.e., at 23 days postinfection. Larvae for morphological study were collected by pepsin digestion, fixed in glacial acetic acid, and cleared in glycerin. Tissues for histological study were fixed in 10% formalin or Bouin's fixative. All sections were stained with hematoxylin and eosin. The differences in the morphology of the larvae of these 4 species were found to be length of the body, shape of the anterior end, and shape of the tail. The major differences in the histological anatomy of these larvae were found to be the body diameter, form of lateral alae when present, presence or absence of internal cuticular bars, shape and internal patterns of the excretory columns, and size and number of intestinal cells. These 4 larvae are differentiated from other described species of ascaridoid larvae that may cause visceral larva migrans, and keys have been devised to aid in the making of a diagnosis.