Alvin A. Gajadhar

Phylogenetic relationship of Sarcocystis neurona to other members of the family Sarcocystidae based on small subunit ribosomal RNA gene sequence

Sarcocystis neurona is a coccidial parasite that causes a neurologic disease of horses in North and South America. The natural host species are not known and classification is based on ultrastructural analysis. The small subunit ribosomal RNA (SSURNA) gene of S. neurona was amplified using polymerase chain reaction techniques and sequenced by Sanger sequencing reactions. The sequence was compared with partial sequences of S. muris, S. gigantea, S. tenella, S. cruzi, S. arieticanis, S. capracanis, Toxoplasma gondii, Eimeria tenella, and Cryptosporidium parvum. Alignments of available sites for all 10 species and alignments of the entire SSURNA sequence of S. neurona, S. muris, S. cruzi, T. gondii, and C. parvum were performed. Alignments were analyzed using maximum parsimony and maximum likelihood methods to determine relative phylogeny of these organisms. These analyses confirmed placement of S. neurona in the genus Sarcocystis and suggested a close relationship to S. muris, S. gigantea, and T. gondii. Molecular phylogeny suggests that Sarcocystis spp., which utilize the dog (Canis familiaris) as the definitive host, evolved from a common ancestor, whereas those species (including T. gondii) that utilize the cat (Felis domesticus) as the definitive host evolved from another common ancestor. This suggests a possible definitive host for S. neurona.

Susceptibility of mule deer (Odocoileus hemionus) and two species of North American molluscs to Elaphostrongylus cervi (Nematoda: Metastrongyloidea)

An experimental study was done to determine whether Elaphostrongylus cervi can be transmitted to common intermediate and definitive hosts indigenous to North America. First-stage larvae of E. cervi obtained from red deer (Cervus elaphus elaphus) in New Zealand developed to the infective third stage in snails (Triodopis multilineata) and slugs (Deroceros reticulatum). Two mule deer (Odocoileus hemionus) were inoculated orally with 102 or 406 third-stage larvae. One animal developed a patent infection on day 121 postinoculation (PI), and the other had numerous first-stage larvae in its lungs and colonic feces on 128 days PI when it was killed. A control red deer inoculated with 100 larvae began passing larvae on 119 days PI. Larval excretion was low and intermittent in the mule deer and during the first 4 wk of patency in the red deer. Both mule deer developed progressive neurological disease beginning on day 104 PI and had to be killed 4 or 7 wk later, respectively. The red deer remained clinically normal.

Description of the goose coccidium Eimeria stigmosa (Klimes, 1963), with evidence of intranuclear development

Oocysts of Eimeria stigmosa isolated from a wild juvenile lesser snow goose (Anser caerulescens caerulescens) were used in experimental infections of laboratory-reared geese. The structure of oocysts is described; a peculiar bumpy surface and a calyx-like thickening around the micropyle are illustrated by scanning electron microscopy. Experimentally infected geese had reduced feed intake and passed blood in their feces. Six days post-inoculation (p.i.) oocysts were passed for about 24 hr. Oocyst production was not increased in dexamethasone-treated geese. Complete sporulation of oocysts occurred after about 3.5 days. Developmental stages in lesser snow geese were occasionally present throughout the intestine, but were concentrated at Meckels diverticulum, and at foci in the ileum and colon. Meronts were found 2, 3 and 4 days p.i. and gamonts and developing oocysts were observed 4, 5 and 5.5 days p.i. All endogenous stages of E. stigmosa were present in the nucleoplasm of enterocytes, primarily at the apical half of villi. Nuclear hypertrophy occurred in infected cells and nuclei containing gamonts were enlarged up to 4 times their normal size. Mild lesions were observed in the intestine of infected geese. Patent infections were established in lesser snow, Canada (Branta canadensis) and domestic (Anser anser domesticus) geese, but oocysts were not passed by inoculated ducks.

Tongue has higher larval burden of Trichinella spp. than diaphragm in wolverines (Gulo gulo)

Trichinella is an important zoonotic parasite found in a range of wildlife species harvested for food and fur in Canada. We compared larval intensity from tongue and diaphragm, the best predilection sites in other animal species, from naturally infected, wild wolverines (Gulo gulo) (n = 95). Muscle larvae of Trichinella spp. were recovered by the pepsin/HCl artificial digestion method (gold standard) using double separatory funnels, and species were identified using multiplex PCR. Prevalence was 83% (79/95). Of those positive for Trichinella spp. (n = 79), 76 (96.2%) were detected in both tissues, 2 (2.5%) were positive only on diaphragm, and 1 (1.3%) only on tongue. A total of 62 of 79 wolverines (78.5%) had higher larval burden in tongue than in diaphragm, whereas 17 wolverines (21.5%) had higher larval burden in diaphragm. The predilection site (higher larval burden) of Trichinella spp. larvae did not vary significantly between juvenile and adult wolverines (P = 0.2), between male and female wolverines (P = 0.9), and among wolverines classified as having low and high larval intensities overall (P = 0.2). Trichinella T6 was the predominant genotype (63 of 79; 80%), followed by T. nativa (T2) (6 of 79; 8%). Mixed infections of T2 and T6 were observed in 9 of 79 (12%) wolverines. Larval intensity of Trichinella T6 was higher in tongues than diaphragms. No statement can be made for T2 due to insufficient T2 positive samples. In conclusion, tongues are a better site for sampling than diaphragms in future surveys of Trichinella larval intensity in wolverines; however, either tissue is suitable for prevalence studies.