Persistent challenge with Trichostrongylus colubriformis and Haemonchus contortus larvae does not affect growth of meat-breed lambs suppressively treated with anthelmintics when grazing

Influence of seasonality and biological activity on infection by helminths in Cantabrian bear

This study aimed to investigate the variations of parasites in the feces of brown bears Ursus arctos inhabiting the Cantabrian Mountains (NW Spain). A total of 248 bear fecal samples were collected throughout one year, spanning from August 2018 to September 2019, at an approximate frequency of 20 samples per month. The results were analyzed in relation to both the season and the biological activity of the brown bears, i.e., hibernation, mating and hyperphagia. Among the examined samples, eggs of Dicrocoelium dendriticum (32.2%; 95% Confidence Interval: 26.4-38.1), Baylisascaris sp. (44.8%; 38.5-50.9), ancylostomatids (probably belonging to Uncinaria spp.) (16.5%; 11.9-21.1) and Trichuris sp. (1.2%; 0-2.6) were observed. Significant seasonal differences were noted for Baylisascaris and ancylostomatids (χ2 = 21.02, P = 0.001 and χ2 = 34.41, P = 0.001, respectively). Furthermore, the presence of helminth eggs was correlated with the activity phase of the brown bears. Dicrocoelium attained the highest prevalence during the mating phase, while Baylisascaris and ancylostomatids were more frequent during hyperphagia. Notably, the highest egg-output counts for Dicrocoelium and Baylisascaris sp. were recorded during the mating phase and hibernation, respectively, whereas ancylostomatids eggs peaked during hyperphagia. Additionally, variations in egg-output counts were significant for all helminths concerning the season, with the exception of Trichuris sp., and for Dicrocoelium and Baylisascaris sp. According to bear activity. It is concluded that infection by gastrointestinal helminths depends on the season and the biological activity of the bears from the Cantabrian Mountains, and their health status could result influenced.

Influence of targeted selective anthelmintic treatment on the productive performance of wool and hair lambs naturally infected with gastrointestinal nematodes in Brazil

Targeted selective treatment (TST) is an alternative method to reduce the use of anthelmintics and delay the development of resistant nematode populations. However, there is limited information on the actual effects of this type of treatment on livestock productivity. The objective of this study was to evaluate the production performance of Santa Ines (hair) and Ile de France (wool) lambs naturally infected with gastrointestinal nematodes (GIN) under TST based on packed cell volume (PCV) versus suppressive anthelmintic treatments. Thirty-eight lambs were divided into two treatment groups: Suppressive treatment, animals were drenched with monepantel every two weeks and TST, animals were treated with the same anthelmintic when they presented PCV ≤ 20%. Feces, blood, and weight were measured weekly to determine eggs per gram of feces, PCV, total plasma protein, and weight gain. After animals were slaughtered, carcasses were weighed to determine carcass yield. In the TST group, substantial productive losses of approximately 21.3% in the wool and 25.9% in the hair lambs were observed in body weight compared to their counterparts. Significant differences in hematological variables occurred over the experimental period, especially in the wool lambs under TST. Favorable environmental conditions enabled infective larvae to survive and thrive on pasture. Haemonchus contortus and intestinal nematodes were the most common parasites found in the Ile de France lambs and the Santa Ines lambs, respectively. Although TST prevented mortality, it did not prevent production losses. Both breeds showed a significant drop in production due to GIN parasitism.

Diarrhoea associated with gastrointestinal parasites in grazing sheep

Diarrhoea is a common, widespread and frustrating reality for sheep enterprises in most sheep producing regions globally and of particular concern in Australia as the major risk factor for breech flystrike. Parasitic disease has long been recognised as an important factor in diarrhoea in sheep, particularly the gastrointestinal nematodes (Trichostrongylus and Teladorsagia species). This review focuses on the role of parasitic infections in causing diarrhoea in sheep, with emphasis on the epidemiology of diarrhoea outbreaks related to worms and opportunities to manage the risk of diarrhoea outbreaks in sheep related to parasitic infections. Parasitic nematodes damage the gastrointestinal tract via a complex relationship between direct impacts from worms, such as physical changes to the gut mucosa, and indirect effects largely associated with the host response. Diarrhoea associated with large worm burdens is most efficiently managed through integrated parasite management programs. Despite some limitations, measuring faecal worm egg counts remains a mainstay for assessing the contribution of worms to outbreaks of diarrhoea in sheep. Larval hypersensitivity scouring is emerging as a significant cause of worm-related diarrhoea in sheep without large adult worm burdens in some geographic locations. The syndrome describes a heightened inflammatory response to the ingestion of trichostrongylid infective larvae seen in the gut of sheep with diarrhoea, and is most effectively addressed through selecting sheep for low breech soiling ('dag scores'), as worm resistant sheep may show an increased propensity for diarrhoea, even with low rates of larval challenge. Importantly, dag should be considered as a separate trait to WEC in breeding indexes. Outbreaks of diarrhoea in young sheep are often multifactorial, and co-infections with nematodes and other infectious agents associated with diarrhoea are common. This presents challenges for the field investigation of diarrhoea in grazing sheep.

Losses caused by gastrointestinal nematode infections in Dorper lambs under two nutritional status

The aim of this study was to evaluate the effect of two nutritional statuses on the productive performance of Dorper lambs naturally infected with gastrointestinal nematodes. Thirty-two lambs, grazing together on the same pasture, were allocated into four experimental groups: (G1) infected-supplemented diet, (G2) control-supplemented diet, (G3) infected-basal diet, and (G4) control-basal diet. Control animals received suppressive treatment with monepantel every two weeks, while precautionary anthelmintic treatments were given to all lambs of the infected groups with packed cell volume (PCV) <23%. There was reduction in the PCV means of all groups, which was more pronounced in the infected lambs that also presented reduction in total plasma protein values in comparison with the controls. Weight gain was affected by diet and infection status (P < 0.05). Daily body weight gain was 0.170 kg in the G1, 0.205 kg in the G2, 0.085 kg in the G3, and 0.116 kg in the G4. The cold carcass weight was 4.1% and 13.7% higher in controls in comparison with infected lambs, respectively, in the supplemented and basal diets. The infected groups, despite receiving precautionary anthelmintic treatments to prevent deaths due to haemonchosis, presented reduction in the production parameters in comparison with the controls.

Integrated parasite management improves control of gastrointestinal nematodes in lamb production systems in a high summer-rainfall region, on the Northern Tablelands, New South Wales

This experiment tested the hypothesis that integrated parasite management (IPM) programs would reduce the effects of gastrointestinal nematodes (GIN) in meat-breed lamb production systems on the Northern Tablelands of New South Wales. The experiment was a longitudinal experiment using twin-bearing Border Leicester × Merino ewes on farms managed in accordance to either regional WormBoss IPM programs (n = 3 farms) or typical (TYP) regional GIN control (n = 2 farms). Ewes on each farm were either GIN-suppressed (SUP; n = 120 ewes) or not (NSUP; n = 120 ewes) and were managed in two groups (n = 120/group) balanced for GIN control. Ewes lambed in September and at lamb marking, 120 lambs (Dorset sires) from each ewe GIN control group were enrolled in the experiment to investigate the effect of ewe GIN control on lamb performance up to weaning. Overall mean worm egg count (WEC) of ewes (P = 0.004) was lower with IPM (IPM 766 vs TYP 931 epg) and was achieved with fewer drenches (IPM 4.5 vs TYP 5.5/year). Despite lower WEC, GIN infection reduced liveweight (IPM –2.1 kg vs TYP –1.1 kg, P = 0.0006) and clean fleece weight (IPM –0.11 kg vs TYP –0.01 kg, P = 0.03) of ewes to a greater extent on IPM farms. The annual rate of apparent ewe mortality was 6.5% and this was unaffected by GIN infection. WEC of lambs at weaning was lower on IPM farms (IPM 159 epg vs TYP 322, P < 0.0001) but the difference in weaning weights of lambs reared by NSUP and SUP ewes was greater on IPM farms (IPM –1.1 kg vs TYP 0.2 kg, P < 0.0001). Overall, the production loss due to GIN infection in these sheep-meat production systems, on the Northern Tablelands of New South Wales, was small and treatment frequency can be reduced by IPM programs.

Growth is impeded by gastrointestinal nematodes in weaned rather than suckling meat-breed lambs in a high summer rainfall region, on the Northern Tablelands, New South Wales

The hypothesis tested in this experiment was that the effects of gastrointestinal nematodes (GIN) on growth of meat-breed lambs would be absent during the suckling period and greatest after weaning. The experiment was a single factor design conducted on five farms over 2012–2014, using meat-breed lambs (Poll Dorset × Border Leicester/Merino), which were either GIN-suppressed (SUP) or not (NSUP). The experiment commenced at lamb marking and continued for 5 months. SUP lambs were serially treated with short- and long-acting anthelmintics. NSUP lambs were not treated before weaning and at weaning received a short-acting multi-active drench with subsequent treatments varying between farms. Worm egg count (WEC) of NSUP lambs were significantly higher (P < 0.0001) than SUP lambs at weaning (1170 and 10 epg) and thereafter (P < 0.0001) reaching 920 epg 2 months after weaning. Haemonchus contortus was the predominant species present in NSUP lambs with smaller contributions from Trichostrongylus spp. There was no effect of GIN control on lamb growth during the pre-weaning period (SUP 17.2 kg vs NSUP 17.0 kg, P = 0.093), whereas GIN reduced growth of lambs by 0.5 kg (SUP 7.1 kg vs NSUP 6.6 kg, P = 0.002) in the last month of observation. There was no effect of GIN control on lamb mortality. GIN did not affect growth of suckling meat-breed lambs despite high WEC at weaning indicating resilience to GIN infection in lambs growing at 200 g/day. In contrast, post-weaning growth was reduced by GIN infection, despite effective treatment at weaning and movement to GIN ‘safe’ pastures. The susceptibility of weaned lambs to the effects of GIN infection highlights the importance of effective control measures at this time.