Protostrongylid Larvae Research Articles

Occurrence of faecal endoparasites in reindeer (Rangifer tarandus) in two grazing areas in northern Norway

BackgroundSemi-domesticated reindeer represent an important livestock industry and livelihood for a proportion of the human population in northern Fennoscandia. Reindeer husbandry is considered an extensive animal husbandry, where the animals are kept mostly on natural pastures, although sometimes kept in fenced areas for shorter periods. These reindeer may harbour a variety of parasites that may affect animal health and production. The relatively limited close contact between herds and owners gives limited opportunities for diagnosis and treatment of diseases in general. Furthermore, the effects of subclinical parasitism in livestock are commonly expressed as a reduction in productivity rather than clinical disease and mortality. Thus, specific knowledge of endoparasites and parasitic infections in these herds is scarce. This study investigated the occurrence of various endoparasites in reindeer by analysis of a total of 114 faecal samples from winter-slaughtered reindeer from two different grazing areas in Troms and Finnmark, Norway.ResultsUsing a McMaster method, a Baermann technique, and a direct immunofluorescent antibody test, the following parasites were identified in the faecal samples with the occurrence data given as percentages: Strongylid eggs (62%), Nematodirinae spp. eggs (24%), Capillaria sp. eggs (42%) and Moniezia spp. eggs (17%), Dictyocaulus spp. larvae (14%) protostrongylid larvae (40%), Eimera spp. oocysts (23%), and Giardia duodenalis cysts (5%). Cryptosporidium oocysts were not detected. Parasite eggs, oocysts, and cysts were quantified.Molecular analysis revealed G. duodenalis sub-assemblage AI, a potentially zoonotic genotype not previously reported in reindeer from this region. Morphological analyses of Eimeria oocysts identified two species, Eimeria mayeri and Eimeria rangiferis, and molecular analyses of the cytochrome C oxidase I (coi) gene and 18 s rRNA (18SSU) gene of Eimeria confirmed the presence of Eimeria species that are specific to reindeer.ConclusionsA high prevalence, but low burden, of endoparasites was detected in samples from these semi-domesticated reindeer. The samples were collected during winter, when adult gastrointestinal parasites usually produce only low numbers of transmission stages. Therefore, together with the low number of samples, detailed and definitive conclusions regarding parasite status of semi-domesticated reindeer are avoided. Nevertheless, these data provide a snapshot overview of parasite occurrence in a semi-domesticated animal group vulnerable to the various environmental changes to which they are exposed.

Patterns of parasite eggs, oocysts and larvae shedding by moose in the Biebrza marshland (NE Poland).

The study analyses patterns of endoparasite eggs, oocysts and larvae shedding by moose from the relict population in the Biebrza marshland, NE Poland, which has grown to be one of the largest in Central Europe since the ban on hunting imposed in 2001. The analysis identified 10 species or groups of parasites among 230 faecal moose samples collected over 16 consequent months. The most prevalent were the eggs of Trichostrongylidae, Trichuris spp., Nematodirella alcidis, Parafasciolopsis fasciolaemorpha and the larvae of Elaphostrongylus sp. Four parasite species were more prevalent in males, indicating male-biased parasitism, and the studied moose population exhibited a female-skewed sex ratio. Nematodirella alcidis eggs and Protostrongylid larvae were more prevalent during winter, which indicated their resistance to harsh weather conditions. The prevalence of Eimeria alces and Aonchotheca sp. increased during the growing season, as did the number of eggs per gram of faeces (EPG) of P. fasciolaemorpha, possibly due to the availability of water sources. Higher mean monthly temperature was also found to have a positive effect on the excretion of Trichostrongylidae and Moniezia spp. eggs. In addition, the time of infection and the specificity of the parasite life cycle, being sensitive to certain climatic conditions, also appeared to have a strong influence on eggs, oocysts and larvae shedding in this non-harvested moose population.

GASTROINTESTINAL PARASITIC INFECTIONS IN DEAD OR DEBILITATED MOOSE ( ALCES ALCES) IN SWEDEN.

: Our objectives were to determine prevalence and intensity of gastrointestinal parasites of dead or euthanized emaciated moose in central and southern Sweden ( n=50) and to assess parasite intensity as a major contributing factor in the poor condition of these moose. All animals were infected and most had gastrointestinal nematodes. Seven parasite species were found in the abomasa and 10 species were found in the small intestine. Coinfections were commonly found in the abomasum ( Ostertagia antipini and Mazamastrongylus dagestanica) and in the small intestine ( Nematodirella alcidis and Trichostrongylus capricola). Moose had many nematodes; the highest numbers were 224,400 and 11,760, in the abomasum and in the small intestine, respectively. Fourteen moose had more than 40,000 gastrointestinal nematodes (excluding large intestine nematodes represented by Trichuris spp. and Oesophagostomum venulosum). Additionally, a moderate prevalence (36%) of protostrongylid larvae (dorsal spine larvae) and a low prevalence (2-4%) of protozoal infections were identified at microscopic examination of feces. Adult moose had significantly more parasites than did subadults. The results did not show parasite load as a single or a major cause of the moose mortality, but they provided an update on the species composition of helminth parasites in moose in Sweden and illustrated the extreme infection intensities that free-ranging moose can have.

Морфологическая и молекулярная характеристика некоторых видов нематод семейства Protostrongylidae Leiper, 1926

Objective of research: conducting morphological and molecular-genetic identification and studying phylogenetic relations between protostrongylids. Materials and methods: helminthological material was collected from wild (Capra sibirica, C. falconeri, Ovis vignei and O. ammon) and domestic hollow horned ruminants (C. hircus and O. aries), and land mollusks of the family Xeropicta in the piedmont and mountain area of Uzbekisan. The morphology of protostrongylids was studied using the methods of Boev (1975) and Anderson (1978). To identify the nematode type we used temporary preparations treated with glycerol. The first-stage larvae were investigated by examination of fecal samples from animals taking into account the length, tail form and body size. To study the morphology of the third-stage protostrongylid larvae the feet of infected mollusks Xeropicta candaсharica were separated and placed into the artificial gastric juice where the cap was destroyed and the infected larvae were eliminated. After determination of species belonging of mature and larval nematodes the material was stored in separate test-tubes with distilled water under the low temperature (- 20 ºС) or in 70 % Ethanol for the molecular analysis. We used microscopes ML 2000 with a digital camera and Olympus CX3. DNA extraction, amplification and sequencing were performed with an automated sequencer. Phylogenetic analysis was conducted using the software Clustal X 2.0. Phylogenetic trees were created by the Neighbor–Joining method. Nucleotide sequences ITS-2 regions of species Protostrongylus rufescens (EU018485), P. shiozawai (AB478249), Ortostrongylus macrotis (EU018483), Cystocaulus ocreatus (EU018481) and Umingmakstrongylus pallikuukensis (AY648409) received from the NCBI GenBank were used in phylogenetic analysis. Results and discussion: Four species of adult protostrongylid nematodes: Protostrongylus rufescens, P. hobmaieri, Spiculocaulus leuckarti and Cystocaulus ocreatus were determined. DNA from four species of mature protostrongylids and larvae was amplified by using ITS-2 regions. Amplificate dimension of nematodes P. rufescens and P. hobmaieri was 380 base pairs (b.p.), S. leuckarti – 388, C. ocreatus – 399 b.p. According to the results of phylogenetic analysis and comparison of nucleotide sequences, five protostrongylid species were found in animals of the Caprinae subfamily: P. rufescens, P. hobmaieri, Protostrongylus sp., S. leuckarti and C. ocreatus. The morphological and molecular-genetic analysis of detected nematodes enables the precise identification.

Endoparasites in a Norwegian moose (Alces alces) population - Faunal diversity, abundance and body condition.

Many health surveillance programs for wild cervids do not include routine parasite screening despite evidence that gastrointestinal parasites can affect wildlife population dynamics by influencing host fecundity and survival. Slaughter weights of moose in some regions of Norway have been decreasing over recent decades but any role of parasites has not yet been considered. We investigated parasite faunal diversity of moose in Hedmark, SE Norway, by faecal analysis and identification of adult abomasal and caecal nematodes during the autumn hunting season. We related parasite prevalence and abundance to estimates of body condition, gender and age. We identified 11 parasite groups. Moose had high abomasal gastrointestinal nematode (GIN) burdens and all individuals were infected. Ostertagia antipini and Spiculopteragia alcis were the most prevalent abomasal GINs identified. O. leptospicularis and Telodorsagia circumcincta were also identified in the abomasa while a range of other GIN and Moniezia sp. eggs, and coccidia, Dictyocaulus sp. and Protostrongylid larvae were found in faeces. Female moose had higher mean abomasal nematode counts than males, particularly among adults. However, adult males had higher faecal egg counts than adult females which may reflect reduction in faecal volume with concentration of eggs among males during the rut. We found no strong evidence for the development of acquired immunity to abomasal nematodes with age, although there was a higher Protostrongylid and Moniezia infection prevalence in younger animals. High burdens of several parasites were associated with poor body condition in terms of slaughter weight relative to skeletal size but unrelated to visually evaluated fat reserves. Given findings from earlier experimental studies, our results imply sub-clinical effects of GI parasite infection on host condition. Managers should be aware that autumn faecal egg counts and field assessments of fat reserves may not be reliable indicators of parasitism and may underestimate impacts on wildlife populations.

Sentinels in a climatic outpost: Endoparasites in the introduced muskox (Ovibos moschatus wardi) population of Dovrefjell, Norway.

We assessed the occurrence of endoparasite eggs, cysts, oocysts and larvae in the muskox population of Dovrefjell, Norway, during June and August 2012. This population originates from 13 calves translocated from Eastern Greenland during the 1950s. A total of 167 faecal samples were collected, of which 49% came from identified individuals: 165 were examined by the Baermann and 95 by McMaster techniques and 167 by immunofluorescence antibody test (IFAT). Lungworm larvae recovered in the Baermanns were identified as Protostrongylidae (82%) and Dictyocaulus sp. (76%) based on morphology. Further molecular analyses of the ITS-2 region of two protostrongylid larvae from two muskoxen as Muellerius capillaris. Larval prevalence and intensity differed significantly between samples collected from the different age groups in June and August, with increasing prevalence and intensity in calves during the course of their first summer, whereas intensity decreased in adults from June to August. McMaster test and IFAT were used to determine the occurrence of infections with intestinal strongyles (84%), Moniezia spp. (24%), Nematodirus sp. (2%), Eimeria spp. (98%), Cryptosporidium sp. (14%) and Giardia duodenalis (7%). Molecular analyses of three isolates of Cryptosporidium and Giardia were identified as Cryptosporidium xiaoi and G. duodenalis assemblage A. Although infection intensity of all these intestinal parasites tended to be low, the high level of polyparasitism, together with the other challenges faced by this population living at the edge of their climatic range, means that these infections should not be ignored. The potential that M. capillaris, Cryptosporidium and Giardia infections derive from other sympatric host species (sheep and reindeer) is discussed.

Evaluation of the use of pooled fecal samples for the diagnosis of protostrongylid infections in sheep

The Baermann–Wetzel method is the recommended test for the diagnosis of lungworm infections. The objective of this study was to evaluate the use of pooled fecal samples for the diagnosis of protostrongylid infections in sheep flocks and to investigate the sensitivity of the pooled Baermann–Wetzel technique in relation to individual analysis, which is time consuming and expensive. Fecal samples were taken from 10 sheep flocks positive for protostrongylids located in northwestern Spain. Ten pools composed of 6 individual fecal samples, chosen at random from the entire flock sampling, were performed for each flock at the same time as individual analyses. Protostrongylid larvae were detected in 56 pools, with a 56% flock sensitivity. Flock sensitivity was positively associated with the within-flock prevalence (P<0.001), but not with the mean larvae output. A high sensitivity (78.3%) has been observed in flocks with medium or high prevalence, so pooled fecal samples can be used in those flocks that require an effective treatment regimen against these nematodes.

Protostrongylid infection in meat sheep from Northwestern Spain: Prevalence and risk factors

2093 Faecal samples from 74 commercial meat ovine flocks were collected and examined by the Baermann–Wetzel method for protostrongylid infection. The risk of being infected by lungworms was evaluated with a data mining classification tree (CHAID), and the intensity of infection with a general linear model (GLM). 242 out of 2093 faecal samples examined were positive for protostrongylid infection (11.6%; 95% CI 10.2–12.9). Only two species were found, Muellerius capillaris (97.9%) and Neostrongylus linearis (5.4%). 50 out of 74 farms presented at least one animal shedding protostrongylid larvae in faeces. All of them held animals infected by M. capillaris and seven presented mixed infections with N. linearis. Average larval output in infected sheep was 11.9 (SD 30.91). This study showed that protostrongylid prevalence in sheep for meat production was determined mainly by a positive interaction with Dictyocaulus filaria infection; other factors that have influenced over protostrongylid infection were age, introducing external animals in the flocks, mixed management with goats and animal density in pastures. Treatment effects on prevalence were only observed in flocks that did not introduce ewes. The lowest protostrongylid prevalence has been reported in flocks without D. filaria infection and without contact with goats.

Molecular Confirmation of Parelaphostrongylus tenuis Infection in a Horse With Verminous Encephalitis

>> Editor: Advances in molecular diagnostic technology have enabled us to identify and confirm an etiologic agent that was not possible when we published a case report of verminous encephalitis in a colt in Veterinary Pathology. 2 Although we presumed that the cause of the encephalitis was Parelaphostrongylus tenuis—a meningeal helminth that commonly parasitizes white-tailed deer (Odocoileus virginianus)—we could identify only the parasites as members of the family Protostrongylidae. We recently applied a polymerase chain reaction–(PCR) based approach to the DNA isolated from archival paraffin blocks. Using genus-specific primers and sequence analysis, we confirmed the infection specifically as P tenuis. Thin sections of formalin-fixed, paraffin-embedded brain tissue containing protostrongylid larvae were processed for DNA extraction with a QIAamp 1 DNA Mini Kit (Qiagen, Valencia, CA) according to the manufacturer’s instructions. The Parelaphostrongylus spp–specific primers used for PCR were described previously (PTP1, 5 0 -CCGTCGAATACATGT CATCC-3 0 ; PTP2, 5 0 -TCGTCAAGACGATGATTCCC-3 0 ). 1 Specificity of these primers for Parelaphostrongylus spp was confirmed by BLAST comparison with nonredundant sequences in the BLASTn database (National Center for Biotechnology Information). These primers amplify a 248–base pair product covering a portion of the second internal transcribed spacer of the ribosomal RNA gene in Parelaphostrongylus spp. The PCR reaction mixture included 10mM Tris-HCl (pH 9.0), 50mM KCl, 0.1% Triton X-100, 1.5mM MgCl2, 250mM deoxynucleotide triphosphates, 0.5mM of each primer, and 1 U of Taq DNA polymerase (Promega, Madison, WI). Cycling parameters included denaturation at 94 � Cf or 3 minutes, followed by 40 cycles of denaturation at 94 � Cf or 1 minute, annealing at 60 � C for 1 minute, and extension at 72 � C for 1 minute. Reaction products were examined by electrophoresis in a 1% agarose gel and were subsequently purified with a QIAquick 1 Gel Extraction Kit (Qiagen) according to

PROTOSTRONGYLID PARASITES AND PNEUMONIA IN CAPTIVE AND WILD THINHORN SHEEP (OVIS DALLI)

We describe health significance of protostrongylid parasites (Parelaphostrongylus odocoilei and Protostrongylus stilesi) and other respiratory pathogens in more than 50 naturally infected Dall's sheep (Ovis dalli dalli) from the Mackenzie Mountains, Northwest Territories (1998-2002) as well as in three Stone's sheep (O. d. stonei) experimentally infected with P. odocoilei (2000-2002). Histological lesions in the brain and distribution of P. odocoilei in the muscles of experimentally and naturally infected sheep were consistent with a previously hypothesized "central nervous system to muscle" pattern of migration for P. odocoilei. Dimensions of granulomas associated with eggs of P. odocoilei and density of protostrongylid eggs and larvae in the cranial lung correlated with intensity of larvae in feces, and all varied with season of collection. Prevalence of P. stilesi based on the presence of larvae in feces underestimated true prevalence (based on examination of lungs) in wild Dall's sheep collected in summer and fall. Similarly, counts of both types of protostrongylid larvae in feces were unreliable indicators of parasitic infection in wild Dall's sheep with concomitant bacterial pneumonia associated with Arcanobacterium pyogenes, Pasteurella sp., and Mannheimia sp. Diffuse, interstitial pneumonia due to P. odocoilei led to fatal pulmonary hemorrhage and edema after exertion in one experimentally infected Stone's sheep and one naturally infected Dall's sheep. Bacterial and verminous pneumonia associated with pathogens endemic in wild Dall's sheep in the Mackenzie Mountains caused sporadic mortalities. There was no evidence of respiratory viruses or bacterial strains associated with domestic ruminants, from which this population of wild sheep has been historically isolated.

Larvae of Elaphostrongylus cervi in a Population of Free-living Red Deer in Italy

Hunter-killed red deer (n = 68; Cervus elaphus) harvested from the Italian provinces of Bologna (Emilia Romagna) and Pistoia (Tuscany) (44 degrees 00'N 11 degrees 00'E) from October 2001 to January 2002 were examined for protostrongylid larvae. Twenty-eight animals (41%) had protostrongylid larvae in feces, lungs, and inguinal and iliac lymph nodes. Of these 28 animals, 20 were adults (71%), four were yearlings (14%), and four were calves (14%). Shape, length, width, and the location to the nematodes were consistent with Elaphostrongylus cervi, which has not been previously reported in Italy.

Efficacy of in-feed-administered ivermectin on Elaphostrongylus cervi first-stage excretion in red deer (Cervus elaphus)

Elaphostrongylus cervi (Nematoda, Metastrongyloidea) is an extrapulmonary lungworm of red deer (Cervus elaphus), which has a wide natural distribution in Eurasia. The presence and seasonal pattern of excretion of large spiny-tailed protostrongylid larvae comparable to the descriptions of first-stage E. cervi in fecal samples (prevalence of 66.47%) from southern and central Spain were recently reported for the first time (Vicente and Gortazar 2001; Vicente et al. 2005). Although individual anthelmintic treatment allows administrating precise drug dosage, such a manipulation would be highly stressful for wild animals. Moreover, it would require the involvement of many people. Management problems could be overcome by using in-feed drug formulations. Only drugs known to be safe and having a broad therapeutic spectrum should be used (Rajkovic-Janje et al. 2004). Ivermectin is a semisynthetic derivative of avermectin characterized by an exceptional potency and wide spectrum of activity against many parasitic nematodes and arthropods. This compound has stimulated interest in its application in the treatment and prevention of parasitic problems common to free-ranging species of wildlife (Kocan 1985 ; Fernandez de Mera et al. 2004). The control of diseases in hunting-managed animals is of concern (Peterson 1991). In particular, E. cervi has considerable pathological consequences for other wild and domestic ungulates, thus being of importance for wildlife managers, livestock breeders and sanitary authorities (Gajadhar and Tessaro 1995; Pusterla 1998). The aim of this study was to assess the efficacy of a treatment usually employed in sanitary programs of semi-extensive red deer hunting ranges: the use of an in-feed 0.6% ivermectin premix formulation under field conditions. A simple case-control study was designed. Naturally infected adult hinds (n=132) fromMontes de Toledo (Ciudad Real province, Spain) were captured from the wild. During May–June 2004, the control group (n=20) and the treated group (n=112) were separately kept in two fenced grounds of similar characteristics. Oral in-feed ivermectin (Ivomec Premix 0.6% Merial Sharp & Dohme, The Netherlands) was mixed with commercial deer feed at a concentration of 7.5 ppm and administrated ad libitum during 7 days. The control group was fed with untreated deer feed. We employed fecal examination as a useful indicator of relative parasite abundance (Todd et al. 1970; Mason 1989). We collected fresh fecal pellet groups (11–22) on day 0 (prior to treatment) and then fortnightly until the end of the study. Protostrongylid larvae were extracted by coprological analysis in less than 24 h from 8–10 g of feces collected using the beaker extraction method as described by Forrester and Lankester (1997). The larvae were quantified in a Favatti counting chamber and expressed as the number of L1 per gram of feces. The terms prevalence and intensity of excretion are used as in Margolis et al. (1982). L1 counts were log10+1-transformed and Mann–Whitney’s nonparametric test (Siegel 1990) was employed to compare treatment effectiveness on L1 excretion intensity between (1) treatment groups throughout the different sampling dates and between (2) pretreatment and post-treatment prevalence separately for each group. Similarly, chi-square tests were employed to test for differences in prevalence. The significance level was established at P 0.05; ZM-W=0.75, P>0.05, respectively, I. G. Fernandez de Mera . J. Vicente (*) . C. Gortazar Instituto de Investigacion en Recursos Cinegeticos IREC (CSIC-UCLM-JCCM), Ronda de Toledo s/n, 13005 Ciudad Real, Spain e-mail: jvicente@irec.uclm.es Tel.: +34-926-225450 Fax: +34-926-225451

Relationship between bronchopulmonary nematode larvae and relative abundances of Spanish ibex (Capra pyrenaica hispanica) from Castilla-La Mancha, Spain

The excretion of bronchopulmonary nematode infective larvae was evaluated in 160 faecal samples of Spanish ibex (Capra pyrenaica hispanica) collected from 13 populations in Castilla-La Mancha, south-central Spain in September 2003. Intensities and prevalences were compared with pasture availability, abundances of wild and domestic ungulates at both levels, i.e. for populations and for faeces in a two-step procedure. Protostrongylid larvae showed similar infection rates (mean intensity: 1.56+/-0.12, n=94; mean prevalence: 25.62+/-6.86%, n=160) to Dictyocaulus spp. (mean intensity: 1.03+/-0.11, n=48; mean prevalence: 30.00+/-7.11%, n=160). At the population level, positive correlations were found between the prevalences of both bronchopulmonary taxa. The prevalence in both groups, but not intensity, also correlated positively with Spanish ibex abundance indexes both for the populations and individual faeces. These findings suggest that: (i) parasite spreading across Spanish ibex populations in Castilla-La Mancha could respond to host density-dependent processes; and (ii) these populations may have similar exposition and/or susceptibility to both bronchopulmonary taxa resulting in similar host-parasite patterns, despite their different life cycles. Bronchopulmonary outputs in the Spanish ibex from Castilla-La Mancha seems not to represent a health risk for this endemic wild ungulate but may be useful in any health surveillance scheme for the increasing populations of Spanish ibex.

Umingmakstrongylus pallikuukensis (Nematoda: Protostrongylidae) in gastropods: larval morphology, morphometrics, and development rates.

Morphological and morphometric aspects of larval development of Umingmakstrongylus pallikuukensis in Deroceras laeve and the effects of temperature on development rates in D. laeve and Deroceras reticulatum were investigated in the laboratory. Larval stages were best differentiated by separation of cuticular sheaths, tail structure, and viability following digestion. Growth in body and esophagus width was observed during the first-stage within the intermediate host, but the major increases in body length and width occurred immediately following the second molt. Larval development in D. laeve and D. reticulatum occurred more rapidly at warmer temperatures. The calculated threshold temperatures were 8.5 and 9.5 C in D. laeve and D. reticulatum, respectively, and 167 degree-days were required for development to third-stage larvae (L3) in both hosts. These thresholds are higher than those calculated from published data for the closely related Muellerius capillaris (4.2 C) but are similar to those for the more distantly related northern protostrongylid, Elaphostrongylus rangiferi (8.3-10.3 C). Conversely, degree-days required for development to infective L3 were more similar among the Muelleriinae than between this group and the Elaphostrongylinae. Developmental parameters for protostrongylid larvae may be influenced both by the environment and by features of the parasites and the intermediate hosts, including phylogeny.

High prevalence of large spiny-tailed protostrongylid larvae in Iberian red deer

The prevalence and abundance of protostrongylid larvae (Nematoda: Protostrongylidae) in 173 fecal samples of Iberian red deer ( Cervus elaphus hispanicus Erxleben, 1777) are presented. Large (401(365–425)±24 μm) spiny-tailed larvae, comparable to the descriptions of first stage Elaphostrongylus cervi larvae were found in 66.47±0.7% of the samples (range 6.8–100%, depending on the locality). The overall abundance of larvae in faces was overdispersed with an average of 24.94±96.23 (range 0–1202) larvae per gram, and ranged between sampling sites from 0.11±0.43 to 96±75 larvae per gram. This is the first report of large spiny-tailed protostrongylid larvae in deer from the western Mediterranean.

Comparative evaluation of two emigration/sedimentation techniques for the recovery of dictyocaulid and protostrongylid larvae from faeces

A comparison between the performance of a flask and a funnel method in recovering dictyocaulid and protostrongylid larvae from faeces revealed the clear superiority of the former. On an average, 137% ( p < 0.01) more Dictyocaulus viviparus, 175% ( p < 0.05) more Muellerius capillaris and 1709% ( p < 0.01) more Elaphostrongylus cervi larvae were recovered from samples processed by flask rather than funnel. Attempts to further improve the flask method by substituting cloth stockinette for paper tissue, tended to result in the recovery of more faecal debris but no more larvae. In addition to its greater sensitivity, it is suggested that the flask method offers advantages over the funnel system both in terms of time-saving and in lessening the likelihood of cross-contamination.

Protostrongylid nematodes in caribou (Rangifer tarandus caribou) and moose (Alces alces) of Newfoundland

Two species of protostrongylid nematodes with dorsal-spined, first-stage larvae, are present in caribou and moose of Newfoundland. Elaphostrongyius rangiferi Mitskevich, 1958, a parasite introduced from Scandinavia, causes periodic epizootics of a severe neurological disease in caribou. Sick animals exhibiting signs of cerebrospinal elaphostrongylosis (CSE) were particularly noticeable in central Newfoundland each winter between 1981 and 1985. Those collected for examinarion were mostly male calves. The disease again became prominent in caribou on the Avalon Peninsula in the winters of 1996 and 1997; it may have spread to that isolated part of the province as recently as 1990. E. rangiferi was also found in moose but no cases of neurologic disease have been reported in this host. Parelapbostrongylus andersoni Prestwood, 1972, was found in caribou, both in central Newfoundland and on the Avalon Peninsula. Moose may also be infected. Of 1407 terrestrial gastropod intermediate hosts examined, 9 (0.6%) contained infective, third-stage, protostrongylid larvae resembling those of E. rangiferi and P. andersoni which are indistinguishable. The small dark slug, Deroceras laeve, dominated gastropod collections and was the only species infected.

Extracting protostrongylid nematode larvae from ungulate feces.

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).

Dynamics of gastropod infection by first-stage larvae of protostrongylid nematodes--a model.

For the description of the dynamics of snail infection by the 1st-stage larvae of protostrongylid nematodes, Skorping (1988) used the miracidia-snail model (Anderson, 1978). Here it is shown that, in contrast to miracidia, in protostrongylids the instantaneous rate of infection, alpha, is strongly dependent on the experimental design (factors like host size and size of the experimental arena). With respect to this, Anderson's model is modified by incorporation of the experimental design. The parameter alpha in its new sense as the rate of penetration (probability that the infective larva will penetrate into the host during a time unit) is shown to remain dependent, although much less so, on the experimental design. Only the inclusion of the assumed effect of mucus, which decreases the rate of penetration, yields a parameter alpha 0 (the initial rate of penetration), which is completely independent of the design of the experiment, is species-specific, and also gives the best fit to the empirical data. As the above-mentioned factors can strongly influence the value of the instantaneous rate of infection in the laboratory experiments, alpha 0 is more suitable as a measure of either the larval infectivity for the snail or snail susceptibility to infection by the protostrongylid larvae.

The development of Fasciola hepatica parthenitae in Lymnaea truncatula by modification of Muellerius capillaris infection

Adult and juvenile Lymnaea truncatula (height 4 and 1 mm, respectively) were subjected to a dual infection with either Fasciola hepatica and Muellerius capillaris, or with M. capillaris and F. hepatica at 4-h, 7-, 14- and 30-day intervals between the two exposures. The results were compared with those of snails which had been infected with a single parasite species. In dually infected snails, there was a high mortality at the second exposure to both parasite species, and it was strongly increased by each reinfection. The interexposure time had a significant influence on these mortality rates. Histological examination demonstrated a decreased number of rediae (50% or greater) in dually infected snails beginning with the 4-h interval in adults and the 7-day interval in juveniles. The exposure order and the time interval between exposures had a significant influence on the number of rediae: the number of parasites per snail decreased as the time interval lengthened. Delayed maturity occurred in live free rediae in snails infected by F. hepatica and M. capillaris at the 14- and 30-day intervals. In those infected by M. capillaris and F. hepatica, time to reach maturity was not modified compared to that in snails infected with a single species. Protostrongylid larvae were clearly less numerous in dually infected adult snails than in corresponding mono-infected snails. Third-stage larvae were found in the 14- and 30-day groups, regardless of exposure order and were absent in mono-infected snails.