No abstract

Angiostrongylus vasorum and Crenosoma vulpis infect the pulmonary arteries and airways, respectively, of red foxes (Vulpes vulpes). Both are widespread in Europe, but within North America, A. vasorum occurs only on the island of Newfoundland. During 2000–2002, 366 red fox carcasses were examined from six regions of Newfoundland for the purpose of determining the distribution of both parasites, effects on the condition of their host, and whether infection with one affects that of the other. Crenosoma vulpis occurred island-wide with a prevalence of 87% and mean (±SE) intensity of 230 ± 20.8. Young-of-the-year red foxes had more C. vulpis (260 ± 39.4) than yearlings (91 ± 31.2) or adults (78 ± 41.1) (χ2 = 25.72, df = 2, p < 0.001), and numbers of adult worm were weakly related to fecal output of first-stage larvae (r2 = 0.20, p < 0.001) but not to host sex or body-fat index. Angiostrongylus vasorum occurred only in southeast Newfoundland where prevalence was 56% and mean intensity was 72 ± 7.6. Its distribution may be limited by cold, as it was absent from areas with mean winter temperatures below –4 °C. Intensity of adult A. vasorum was not related to host age, sex, larval output, or measures of body condition. Although referred to as a heartworm, 88% of adult worms were actually found in the pulmonary arteries rather than in the right ventricle. Furthermore, there was no apparent association between infections with the two parasites (Gc[1] = 0.10) even though 40% of red foxes had dual infections.

A major weakness of the Baermann funnel technique for extracting nematode larvae from feces is the funnel. As many as 67% of Parelaphostrongylus tenuis first-stage larvae lodged on the sloping surface of glass Baermann funnels. The number of larvae collected after 24 hr was not significantly correlated with total numbers in the samples, whether feces were supported over tissue paper or over window screening. Instead, we collected about 8 times as many larvae and achieved a significant relationship between larvae collected and the total numbers present when pelleted fecal material was submerged over screening in vertical-sided beakers. The methodology of this more efficient and more accurate way of estimating numbers of protostrongylid larvae is described. Most larvae were located on and in the mucous layer covering fecal pellets and readily left fresh pellets emersed in water; 72% of these larvae left after 6 min and only 11% remained after 1 hr. Larvae in water at room temperature sank as fast as 6 cm/min, but those close to a vertical glass surface sank more slowly (97% sank 18.5 cm in 105 min).

From May to October, 1966, gastropods from three different habitats on Navy Island, Ontario, were examined for larvae of Pneumostrongylus tenuis. Of 9940 examined individually, 4.2% contained larvae. A mean of 2.9 larvae was recovered from each infected gastropod. Deroceras laeve and Zonitoides nitidas were the most abundant and commonly infected species. The incidence of infective larvae in adult D. laeve from a wet forested area rose to 25% by late June but dropped to 1.5% during July, coinciding with the disappearance of adult slugs. The level of infection in Z. nitidus (4.3%) remained relatively constant. The wet forested habitat where gastropods were abundant, commonly infected, and active from May to October was probably most important for transmission. Experiments showed that snails already containing larvae can be reinfected and there is some evidence that they are repeatedly infected in nature. Larval development was retarded in aestivating snails. Numbers of larvae recovered and their rate of development differed in various species of experimentally infected gastropods. Snails of the family Polygyridae were the most suitable intermediate hosts studied. Larvae passed by deer were situated in the film of mucus covering faecal pellets. In this location, larvae may be dispersed by high spring water or heavy rainfall. Snails became infected when exposed to larvae in wet and dried soil. Larvae on pellets survived freezing at −15 to −20 °C for up to 306 days.

Woodland (Rangifer tarandus caribou) and barren ground (R. t. groenlandicum) caribou are reported for the first time as hosts of Parelaphostrongylus andersoni, greatly extending the known geographic range of this muscle nematode. Up to 56% of caribou in the Beverly herd, central Northwest Territories, passed dorsal-spined first-stage larvae in their feces. Animals less than 3 years old were more frequently infected and passed greater numbers of larvae than older animals. Larval output in winter and spring did not differ. Adults of the four elaphostrongyline nematodes known to occur in caribou are distinguished by their location in the host, the size of the worms, and the size and morphology of the male copulatory structures. There is an urgent need for tested and improved methods of differentiating larvae of P. andersoni and other elaphostrongyline nematodes from those of P. tenuis that cause neurologic disease in various North American cervids. Demonstration of the occurrence of P. andersoni in Rangifer sp. in North America raises the possibility that it originated in Eurasian cervids and may still occur in the Old World.

Molecular genetics was used to devise the first reliable diagnostic tool for differentiating morphologically indistinguishable dorsal-spined, first-stage larvae (L1's) and other stages of the nematode protostrongylid subfamily Elaphostrongylinae. A polymerase chain reaction (PCR) assay employing specifically designed primers was developed to selectively amplify DNA of the ITS-2 region of the ribosomal gene. Amplification of the entire ITS-2 region differentiated between larvae of the genera Elaphostrongylus and Parelaphostrongylus, based on the lengths of fragments produced. Three sets of primers were designed and used successfully to distinguish larvae at the species level. Although it was demonstrated that one primer set in a single PCR assay was capable of distinguishing each of the three Parelaphostrongylus spp., a second primer set would be required for confirmation in routine diagnostic use. Two of the three primer sets were capable of amplifying DNA from all six elaphostrongyline species and of identifying Elaphostrongylus alces and Parelaphostrongylus odocoilei. Although two separate fragments were produced from each Elaphostrongylus cervi and Elaphostrongylus rangiferi, it was not possible to distinguish these two parasites from each other based on the fragment size. The use of various nematodes, hosts, and fecal controls demonstrated the reliability of the primers for all developmental stages including L1's, third-stage larvae, and adult worms. These primers also have potential for identifying other lungworms as was shown by the amplification of Umingmakstrongylus pallikuukensis, the muskox protostrongylid, and Dictyocaulus sp. from white-tailed deer. Although this assay may benefit from further refinement, its present design provides researchers, wildlife managers, clinicians, and animal health regulators with a practical tool for the control, management, and study of meningeal and tissue worms and their close relatives.

No abstract

Elaphostrongylus cervi Cameron 1931 is identified for the first time in North America from woodland caribou (Rangifer tarandus caribou) in Newfoundland where up to 88% of animals were infected. First-stage nematode larvae identical to those of E. cervi occur in faeces of barren ground caribou (R. t. groenlandicus) of the Kaminuriak herd and of woodland caribou in northern Labrador, Ontario, and Manitoba, suggesting that the parasite is widespread in Rangifer in Canada.In clinically normal caribou, adult E. cervi were found beneath the skin and in fascia of the thoracic musculature. Verminous pneumonia caused by nematode eggs and larvae in the lungs and diffuse lymphocytic leptomeningitis over the brain and spinal cord were consistent aspects of infection. A 10-month-old caribou calf exhibiting neurologic signs had numerous E. cervi among thoracic and cervical muscles but none in the central nervous system. Accumulations of lymphocytes, eosinophils, and histiocytes in the subarachnoid and perineurium of lateral nerves in the posterior region of the spinal cord and destruction of axons in the cauda equina may explain the clinical signs observed.