Helminths of wild boar in the isolated population close to the northern border of its habitat area.

One hundred wild boars (Sus scrofa) from a geographically isolated population on the island Saaremaa of western Estonia were examined for visceral helminths. Seven helminth species, Metastrongylus pudendotectus, M. salmi, M. elongatus, Ascaris suum, Trichuris suis, Dicrocoelium dendriticum and Taenia hydatigena larva, were found. The predominant helminths discovered were lung nematodes (prevalence 82%, mean intensity 96.2 per animal). A significant negative correlation was observed between the weight of wild boars and the number of lungworms and helminth species. The number of helminth species found in the wild boar population on the island was lower compared to that of the adjacent mainland.

Helminthologic survey of the wolf (Canis lupus) in Estonia, with an emphasis on Echinococcus granulosus.

Carcasses of 26 wolves were collected during the 2000/2001 and 2003/2004 hunting seasons and examined for helminths. Thirteen helminth species were recorded: one trematode (Alaria alata), seven cestodes (Diphyllobothrium latum, Mesocestoides lineatus, Taenia hydatigena, Taenia multiceps, Taenia ovis, Taenia pisiformis, and Echinococcus granulosus), and five nematode species (Uncinaria stenocephala, Toxascaris leonina, Toxocara canis, Trichinella nativa, and Trichinella britovi). The most common species were A. alata and U. stenocephala. Mature Echinococcus granulosus was found and described for the first time in Estonia, and its identity verified using PCR-RFLP analysis. Sequencing a fragment of the mitochondrial DNA NADH dehydrogenase 1 (mtND1) gene showed that the E. granulosus strain from Estonia was identical to strain G10, recently characterized in reindeer and moose in Finland.

Helminth fauna of Eurasian lynx (Lynx lynx) in Estonia.

Thirty-seven carcasses of Eurasian lynx (Lynx lynx) collected and examined in Estonia during 1999-2001 had helminths. Parasites identified and their prevalence included Diphyllobothrium latum (5%), Taenia pisiformis (100%), Taenia laticollis (41%), Taenia hydatigena (3%), Taenia taeniaeformis (3%), Toxocara cati (68%), and Trichinella spp. (22%). The only significant relationships (P < or = 0.05) between occurrence of helminths and host age and sex were a greater number of T. pisiformis and T. laticollis in older than in youger male lynx, and older males had a greater number of species of helminth than did younger lynx. Sixty-one fecal samples collected during snow tracking of nine lynx were examined; eggs of T. cati were identified in 38 samples, and Capillaria spp were found in eight samples. This is the first systematic investigation of parasites of lynx in Estonia.

Development and infectivity of eggs and larvae derived from pigs trickle-infected with Oesophagostomum dentatum at different dose levels.

We examined the impact of different Oesophagostomum dentatum dose levels and durations of infection on the development and infectivity of the following generation. Pigs were trickle-infected with 200, 2,000 or 20,000 L3/week over 20 weeks. Egg hatch assays were performed at monthly intervals; however, no consistent differences were found between any of the dose groups in the development of eggs into first-stage larvae. To compare larval infectivity, larvae were derived from faecal cultures set up from the low- and the high-dose groups in the early and the late part of the experiment, and were inoculated into helminth-free pigs (5,000 L3/pig). Worm establishments were significantly higher (P<0.05) in the group of pigs receiving larvae derived early in the experiment from the low-dose group compared with the two groups receiving larvae from high-dose groups, thus indicating an adverse effect of high doses of trickle infection on the later infectivity of L3 larvae derived from excreted eggs.

Oesophagostomum spp. in pigs: resistance to reinfection.

For a study on the occurrence of resistance to reinfection with porcine nodular worm species, pigs were infected twice weekly with 1,000 infective larvae (L3) of Oesophagostomum quadrispinulatum for 8 weeks. All pigs, including noninfected controls, were then treated with fenbendazole. At 10 days after treatment, all pigs received a single challenge inoculation of 5,000 L3 of either O. dentatum or O. quadrispinulatum, respectively. Pigs were slaughtered at 6 weeks after the challenge infection for determination of their worm burdens. The pigs trickle- and challenge-infected with O. quadrispinulatum had significantly lower egg excretion levels (P < 0.01) and worm burdens (P < 0.05) than challenge control pigs, thus indicating some degree of host immunity against the homologous challenge infection. No resistance to reinfection was evident for the heterologous challenge infection. This study elucidates further aspects of the interaction between nodular worm species in the pig.

An in vivo dose-response study of fenbendazole against Oesophagostomum dentatum and Oesophagostomum quadrispinulatum in pigs.

A dose-response study using fenbendazole (FBZ) was carried out in pigs infected with O. dentatum and O. quadrispinulatum to determine the minimum effective dose rate of the drug. Thirty pigs were randomly divided into 6 groups of 5 pigs and infected with 5000 infective larvae each. The animals were re-infected 5 days before treatment (Day 30 after the first infection) with the same number of larvae. On Day 35 the pigs in groups 1-5 were treated with FBZ at the following dose rates: 2.5 mg kg-1 (i.e. 50% of the registered dose level), 1.0 mg kg-1 (20%), 0.25 mg kg-1 (5%), 0.1 mg kg-1 (2%) and 0.05 mg kg-1 (1%), respectively. Pigs in group 6 served as non-treated controls. Seven days after treatment (Day 42 after infection) the pigs were slaughtered, worms recovered from the large intestine and counted. The species and sex of adult worms was determined. A high faecal egg count reduction (FECR) after treatment was observed in groups 1, 2 and 3 (98%, 88% and 91%, respectively), while in groups 4 and 5 the egg counts were not affected by treatment. The mean worm count reduction was high in groups 1, 2 and 3 (100%, 99.9% and 98.6%, respectively), but declined in groups 4 and 5 (77% and 40%, respectively). FBZ showed a high efficacy against immature worms in groups 1 and 2, while in groups 3, 4 and 5 counts were not reduced. Species differentiation revealed a higher effect of FBZ against O. dentatum than against O. quadrispinulatum. Sex differentiation indicated a slightly higher (not significant) efficacy against females than males in both species. This study demonstrated a high efficacy of FBZ against the nodular worms in pigs, even at 5% of the currently registered dose level.

Prepatent periods of different Oesophagostomum spp. isolates in experimentally infected pigs.

To define prepatent periods of different Oesophagostomum spp. isolates we carried out two separate experiments, one using two monospecific laboratory isolates and another using laboratory isolates as well as isolates obtained from pig herds having different management systems and with different anthelmintic treatment histories. Pigs were inoculated with 1,000-2,000 infective larvae. Fecal samples were collected daily beginning on days 15 and 16 postinoculation (p.i.). Fecal cultures were set up at different times to yield larvae that could be identified by DNA analyses. All pigs started to excrete eggs on days 18-24 p.i. The mean prepatent period was 20.2 +/- 1.4 days, with no significant difference being observed between species and isolates. Prepatent periods of 17-19 days were found for the monospecific laboratory isolates of O. dentatum and O. quadrispinulatum. These findings conflict with parasitology textbooks; therefore, suggestions as to the possible reasons for the observed short prepatent periods are given.