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The objective of the present study was to compare Soay- and Texel lamb regarding potential resilience/resistance against the natural infection with gastrointestinal nematodes by determining the parameters: live weight, FAMACHA© Anaemia guide, faecal egg count, blood packed cell volume, species determination of third-stage larvae after larval culture of pooled faecal samples, determination of species-specific antibodies of sera against T. circumcincta and H. contortus and the number of adult helminths in section and to determine the prevalence of gastrointestinal nematodes in the Tierpark Arche Warder e.V. in Schleswig-Holstein. For this study 14 Texel (9 female/5 male) and 11 Soay lambs (4 female/7 male) in 2009 and 12 Texel (9 female/5 male) and 17 Soay lambs (6 female/11 male) in 2010 were kept together in the same stable after lambing and on the same pasture until the end of the pasture season (November).
The first investigation of lambs was carried out in stable and then subsequently from June 2009/July 2010 initially in a three-weekly interval and after an faecal egg count value >300 in a two-weekly interval on pasture. At every sampling occasion the lambs were clinically examined, weighted, blood (EDTA/serum) and faecal samples were taken and sick animals were treated. Additionally individual faecal and oocyst egg counts were determined using a modified McMaster technique (detection limit 2009:100, 2010:50) and the packed cell volume obtained using the standard microhematocrit-method. In 2010 faecal samples of all animals of the same breed were pooled, mixed for larval culture, incubated 7 days and third stage larvae were extracted by modified larval migration (Baermann-Wetzel) technique. In the laboratory (Institute of Parasitology and Tropical Veterinary Medicine, FU Berlin) third stage larvae were used for species determination by qualitative genus-specific PCR. An already established ELISA for the detection of specific antibodies against T. circumcincta total (crude) worm antigen in goats of the institute was used as basis for the establishment of an ELISA for the detection of specific antibodies against T. circumcincta total (crude) worm antigen in sheep. For the detection of specific antibodies against the 24 kDa excretorysecretory protein of H. contortus (HcES24), the HcES24 protein was produced recombinant for the use in ELISA. At the end of the investigation three lambs were selected randomly, were euthanasied and the gastrointestinal tract was investigated for presence of adult helminths.
The statistical analysis was carried out with program Microsoft® Excel® 2008 for Mac Version 12.2.0 (090605) and R Version 2.12.2 ((2011-02-25), ©2011 The R Foundation for Statistical Computing). Mean body weight (Texel sheep: 32.47 kg, Soay sheep: 13.93 kg; t-test, pvalue: ≤0.001***) and mean hematocrit value (Soay sheep: 33.6 %, Texel sheep: 30.1 %; ttest, p-value: ≤0.001***) of both breeds and for both investigation years were significantly different, and only in Soay sheep a significant gender-specific difference of the mean body weight was found (mean female body weight: ca. 13.29 kg, mean male body weight: ca. 14.29 kg; t-test, p-value: 0.04*). The hematocrit deviance had a significant effect on the body weight change (LMM; p-Wert: 0.0377*): The higher hematocrit deviance the higher body weight change. The mean hematocrit deviance for both breeds were by trend more negative in 2009 than in 2010 (2009: S:-0.21, T:-0.82, 2010: S: +0.3, T:-0.01) and Texel sheep had a more negative mean hematocrit value than Soay sheep in 2009. For both breeds FAMACHA© Anaemia guide category was higher in 2010 than in 2009 (LMM: p-value: 0.000415***) and Texel sheep had by trend a higher FAMACHA© Anaemia guide category than Soay sheep in both investigation years. In 2009 and 2010 no MDS-eggs and lung worm larvae, but sporadically S. papillosus- and Coccidia-oocysts were found in faecal samples of both sheep breeds prior to turnout. The prevalence of gastrointestinal nematode eggs in the faecal samples for both breeds and years were ca. 59 % (MDS), ca. 37 % (S. papillosus), ca. 82 % (Coccidia spp.), ca. 4 % (Moniezia spp.) and ca. 3.1 % (Nematodirus spp.).
In 2009, intensitiy (LMM: p-value: 0.01*) and frequency (GLMM: p-value: 0.0012**) of MDS egg excretion of Texel sheep were significantly increased compared to those of Soay sheep. In 2010 Soay sheep had by trend a higher (p-value: 0.426) and more frequently (pvalue: 0,523) MDS egg excretion than Texel sheep. The intensity of MDS egg excretion of Texel sheep was high significantly (p-value: <0,001***) higher in 2009 compared to those of 2010, while the intensity of MDS egg excretion of Soay sheep was significantly higher in 2010 (p-value: 0.034*) compared to those of 2009.
Texel sheep had a higher S. papillosus egg excretion frequency than Soay sheep (GLMM: pvalue: 0.00512**). In 2010 S. papillosus egg excretion intensity was lower than 2009 (LMM: p-value: 0.0023**). Concerning the Coccidia oocyst excretion no significant influence of any parameter was found.
The qualitative genus-specific PCR revealed that animals of both breeds were most frequently infected with Tr. colubriformis: (S:1/T:0.8) followed by H. contortus: (S:0.8/T:0.8) and T. circumcincta: (S:0.8/T:0.4). In 2010 Teladorsagia spp. dominated, followed by H. contortus in the abomasum and in the small intestine most frequently Trichostrongylus spp., followed by Nematodirus spp. were found in sectioned animals. The results of coproscopical analyses, PCR and section in 2009 and 2010 also indicated a mixed infection in sheep of both breeds with Trichostrongylus spp., Nematodirus spp., Teladorsagia spp., H. contortus, Moniezia spp., Eimeria spp. and S. papillosus in Tierpark Arche Warder e.V.
The procedure of ELISA had been cancelled, because there could not be determined an adequate distribution between the provided H. contortus- and T. circumcincta-antibody negative and positive sera. However the recombinant production of 24 kDa excretorysecretory protein of H. contortus was successfull.
Regarding interpretation of the results both investigation years were considered separately due to the deviation in the infection process of following the accidental deworming of sheep in May 2010 (which was inconsistent with the experimental plan). The significantly higher excretion of MDS-eggs in Texel sheep could be seen as a potential evidence for the increased resilience/resistance of Soay sheep against MDS-infection. However, the initial hypothesis, Soay sheep would be more resilient/resistant against MDS-infection than Texel sheep, could not be clearly corroborated. Accordingly, additional studies including comparison and reinfection between these breeds are necessary provide better insight regarding potential resilience/resistance against gastrointestinal nematode infection of one of the investigated breeds and to verify the interesting results of 2009 in this study.