Faecal Egg Output Research Articles

PSII-5 Evaluating Haemonchus Contortus Resistance in Hair Sheep Lambs Under Divergent Selection for Reduced Fecal Egg Count

Abstract The gastrointestinal nematode (GIN) Haemonchus contortus is a major threat to global sheep production, a problem exacerbated by increasing levels of anthelmintic resistance. Genetic selection of sheep for reduced fecal egg count (FEC) is hypothesized to improve parasite resistance. This study measured the biological response and worm burden of Dorper x White Dorper (DWD) with high (average = +37.8) or low (average = -12.0) post-weaning FEC estimated breeding values (EBV) and Barbados Blackbelly x Mouflon (BBM) following oral inoculation with 10,000 H. contortus larvae. Lambs (aged 8 months) were grouped by breed and EBV (DWD+, DWD-, BBM) and treatment (inoculated or non-inoculated control) into 6 groups (n = 4/grp). At d 0 and 21, blood samples were collected to measure packed-cell volume (PCV) and serum IgG via enzyme linked immunosorbent assay and at d 21 FEC were additionally recorded. Lambs were subsequently harvested and adult H. contortus counts for each lamb were captured from the abomasum. Data analysis was performed in SAS v 9.4 and significance was set at P < 0.05. In the inoculated lambs, no difference was observed in PCV at d 21, but DWD+ had a greater mean FEC (1,400 + 297 epg) than both DWD- (263 + 167; P = 0.0157) and BBM (50 + 21; P = 0.004). Total serum IgG (ug/mL) was greater in DWD- than DWD+ lambs at both d 0 (686.37 + 50.7 v. 486.15 + 51.25; P = 0.0321) and d 21 (287.16 + 14.33 v. 197.24 + 12.82; P = 0.0034). In BBM, there was no difference in IgG from d 0 (172.80 + 22.44) to d 21 (185.08 ± 4.25). While BBM had reduced IgG at d 0 than both DWD groups, there was no difference between BBM and DWD+ at d 21 (P = 0.4026). Following harvest, inoculated DWD+ had greater worm burden than DWD- (1,330 + 76 v. 818 + 165; P = 0.0308) and both DWD groups were greater than BBM (263 + 120; P = 0.0003). These data confirm previous findings that BBM are more resistant to H. contortus than DWD, and selection for decreased FEC EBV decreased fecal egg output and worm burden within the DWD breed. Future studies will include RNA-sequencing of abomasal epithelial tissue from inoculated and control lambs in an effort to elucidate gene expression differences between divergently selected DWD and BBM sheep infected with H. contortus.

Application of Urine and Copro Antigen Assays after Primary Infection and Drug Treatment in an Experimental Opisthorchiasis Animal Model.

Infection by Opisthorchis viverrini causes significant health problems, including cholangiocarcinoma (CCA); thus control and elimination of this trematode is an important strategy for the reduction of CCA. Currently, urine and copro antigen detection is more sensitive than parasitological examination of the feces for the diagnosis of opisthorchiasis. Given limitations in human studies, we used an animal model to quantify the parasite antigen profiles in urine and feces in O. viverrine-infected hamsters, and postdrug treatment. The positive detections of O. viverrini antigen began from week 1 in urine and week 2 in feces after infection until week 28 of the study. The recoveries of O. viverrini worms were detected starting from week 1 and eggs of O. viverrini were detected in feces from week 3 after infection and remained detectable throughout the study period. There was a significant positive correlation of urine and copro antigen levels with the number of fecal egg counts (P < 0.01) and worm recovery (P < 0.01). In the drug-treatment experiment, treatment of infected hamsters with praziquantel significantly reduced worm burden, fecal egg output, and antigen in urine and feces compared with the untreated controls (P < 0.001). At 4 weeks posttreatment, the egg and worm reduction rates were 100% and 95.5%, respectively. The positive antigen detections in urine and feces corresponded with partial worm clearance from praziquantel treatment. This study demonstrated a direct link of urine and copro antigen tests with worms infecting the liver thereby reaffirming the reliability of urine and copro antigen assay in opisthorchiasis diagnosis.

A model for the development of the free-living stages of Ostertagia leptospicularis, used in conjunction with on-farm egg count data, to estimate sources of pasture contamination on New Zealand red deer (Cervus elaphus) farms

Farmed red deer face challenges from nematode parasites, primarily the pulmonary species Dictyocaulus eckerti and the complex of Ostertagiinae nematodes in the abomasum. Previous investigations on New Zealand deer farms identified limited seasonality in faecal egg and larval output in all stock classes, however, this does not indicate the key times of year those eggs develop into infective-stage larvae, and subsequently contribute to infection risk. A simple temperature-driven model was developed for the free-living stages of a representative deer-specific Ostertagiinae species; Ostertagia leptospicularis. The model was then validated using development data generated from seasonal plot trials. Using faecal egg counts and animal numbers from the previous monitoring study, and local weather data from each of the sampling farms, the relative contribution of each stock class to infective third-stage larvae population on pasture was estimated for each month of the year (2018–2019). The mixed-age adult females were the primary source of infective larvae on most of the sampled farms, principally due to their numerical dominance (i.e., venison breeding farms). The frequent anthelmintic use in the youngest stock class (< 12 months old) on some farms limited their output of eggs and hence their contribution to pasture infestation with infective larvae. However, the trends of larval development on pasture differed between the farms (due to local climate), and between the sampling years (2018–2019). Therefore, calendar-based application of anthelmintics to older stock is not recommended, as contribution to pasture contamination is multifactorial. The study provides a better understanding of deer parasite epidemiology on which to base improved management practices.

Investigating parasite dynamics of migratory ungulates for sustaining healthy populations: Application to critically-endangered saiga antelopes Saiga tatarica

Contact between wild and domestic ungulates is increasing across rangelands, enabling disease co-transmission. Disease management is difficult given uncertainties in complex system behavior, limited empirical data, and logistical obstacles to interventions. We studied gastrointestinal nematode (GIN) transmission in a rangeland shared by both livestock and the critically-endangered migratory saiga antelope, Saiga tatarica, in order to model infection dynamics under current and plausible future scenarios of increasing livestock numbers, climate change and anti-helminth treatments. Our model was parameterised for trichostrongylid GIN – a cause of mortality and morbidity in ungulates globally - using data on observed faecal nematode egg output and host numbers and distribution. Results showed that seasonal saiga migration leads to asymmetry in parasite transmission, with the majority of GIN acquired by saigas in their autumn and winter range through prior pasture contamination from livestock. Consequently, reducing parasite burdens in livestock early in the season in these areas could disproportionately reduce cross-transmission to saigas. Early-season GIN suppression in livestock in the saiga's spring and summer range was predicted to have weaker effect on parasite transmission to saigas but reduces infections during the calving period, potentially increasing population health and resilience at this critical time. Optimally timed treatments could offset the effects of increasing livestock numbers on GIN infection pressure, while climate warming had only marginal impacts on GIN transmission under all scenarios. Our findings could support better understanding and mitigation of factors affecting saiga health and rural livelihoods. Our approach is transferable to other systems, particularly those with migratory hosts.

Effects of lambing season on nematode faecal egg output in ewes.

In this study, we assessed the occurrence of a periparturient rise (PPR) in winter and spring lambing ewes in Sweden and where nematode egg excretion patterns were investigated mainly for diagnostic purposes. Gastrointestinal nematodes and Haemonchus contortus presence were monitored in parallel in all animals in each experimental group on four farms in samples that were collected mainly when the animals were stabled. Faecal examinations of the same animals were conducted on four sampling occasions between January and June 2018 Each group consisted of 12 crossbreed ewes of similar genotype. One group's peak lambing was in January or February (early), and the other in March or early May (late). The first (S1) and third samples (S3) were from approximately one to two weeks before parturition in the early (winter lambing) and late (spring lambing) group respectively, whereas the second (S2) and fourth samples (S4) were collected approximately three to five weeks post-parturition in the same groups. During the course of the study, there was a significant rise in faecal egg counts (FEC) in both groups on all farms. On three farms with a substantial amount of Haemonchus, we observed a difference in the egg excretion patterns between the two groups of ewes as revealed by a significant interaction between the sampling point and lambing period. Also, when samples corresponding to each other in relation to the number of weeks that had elapsed post-parturition (three to five weeks post-parturition, S2 for early and S4 for late) were compared, FEC were significantly lower in the early group lambing in winter than the late group lambing in spring. This indicates that besides lambing, the rise in nematode egg count is also influenced by other factors unrelated to the lambing period, such as the increased daylight in spring. Due to study limitations, we cannot provide a more detailed explanation for this, but only state that the rise appeared to be more closely linked to season than physiology as measured by day relative to parturition. Still, our results suggests that when turned out, winter lambing ewes contribute to pasture contamination to a lesser extent than those lambing in spring. These results will be used in stipulating evidence-based advice to farmers in their flock management to reduce use of anthelmintics, and at the same time efficiently produce prime lambs.

Evaluation of Immunogenicity and Efficacy of Fasciola hepatica Tetraspanin 2 (TSP2) Fused to E. coli Heat-Labile Enterotoxin B Subunit LTB Adjuvant Following Intranasal Vaccination of Cattle.

Fasciolosis, caused by the liver flukes Fasciola hepatica and F. gigantica, is an economically important and globally distributed zoonotic disease. Liver fluke infections in livestock cause significant losses in production and are of particular concern to regions where drug resistance is emerging. Antigens of the F. hepatica surface tegument represent promising vaccine candidates for controlling this disease. Tetraspanins are integral tegumental antigens that have shown partial protection as vaccine candidates against other trematode species. The Escherichia coli heat-labile enterotoxin’s B subunit (LTB) is a potent mucosal adjuvant capable of inducing an immune response to fused antigens. This study investigates the potential of F. hepatica tetraspanin 2 extracellular loop 2 (rFhTSP2) as a protective vaccine antigen and determines if fusion of FhTSP2 to LTB can enhance protection in cattle. Cattle were immunised subcutaneously with rFhTSP2 mixed in the Freund’s adjuvant and intranasally with rLTB-FhTSP2 in saline, accounting for equal molar ratios of tetraspanin in both groups. Vaccination with rFhTSP2 stimulated a strong specific serum IgG response, whereas there was no significant serum IgG response following rLTB-FhTSP2 intranasal vaccination. There was no substantial antigen specific serum IgA generated in all groups across the trial. Contrastingly, after the fluke challenge, a rise in antigen specific saliva IgA was observed in both vaccination groups on Day 42, with the rLTB-FhTSP2 vaccination group showing significant mucosal IgA production at Day 84. However, neither vaccine group showed a significant reduction of fluke burden nor faecal egg output. These results suggest that intranasal vaccination with rLTB-FhTSP2 does elicit a humoral mucosal response but further work is needed to evaluate if mucosal delivery of liver fluke antigens fused to LTB is a viable vaccine strategy.

Advances in vaccine development for human trichuriasis.

Trichuriasis known as whipworm infection caused by Trichuris trichiura, is a highly prevalent soil-transmitted helminthiasis in low- and middle-income countries located in tropical and subtropical areas and affecting approximately 360 million people. Children typically harbour the largest burden of T. trichiura and they are usually co-infected with other soil-transmitted helminth (STH), including Ascaris lumbricoides and hookworm. The consequences of trichuriasis, such as malnutrition and physical and cognitive growth restriction, lead to a massive health burden in endemic regions. Despite the implementation of mass drug administration of anthelminthic treatment to school-age children, T. trichiura infection remains challenging to control due to the low efficacy of current drugs as well as high rates of post-treatment re-infection. Thus, the development of a vaccine that would induce protective immunity and reduce infection rate or community faecal egg output is essential. Hurdles for human whipworm vaccine development include the lack of suitable vaccine antigen targets and animal models for human T. trichiura infection. Instead, rodent whipworm T. muris infected mouse models serve as a major surrogate for testing immunogenicity and efficacy of vaccine candidates. In this review, we summarize recent advances in animal models for T. trichiura antigen discovery and testing of vaccine candidates, while providing an overall view of the current status of T. trichiura vaccine development.

A 4 year observation of gastrointestinal nematode egg counts, nemabiomes and the benzimidazole resistance genotypes of Teladorsagia circumcincta on a Scottish sheep farm

Anthelmintic resistance threatens the sustainability of sheep production globally. Advice regarding strategies to reduce the development of anthelmintic resistance incorporates the outcomes of modelling exercises. Further understanding of gastrointestinal nematode species diversity, and population dynamics and genetics (which may vary between species) is required to refine these models; and field studies combining faecal egg outputs, species composition and resistance genetics are needed to calibrate them. In this study, faecal samples were taken from ewes and lambs on a commercial farm in south-eastern Scotland at approximately 3 t-4 week intervals between spring and autumn over a period of 4 years. Faecal egg counts were performed on these samples, and L3 were collected from pooled coprocultures. Deep amplicon sequencing was used to determine both the species composition of these L3 and the proportions of benzimidazole-resistant single nucleotide polymorphisms in the isotype-1 β-tubulin locus of the predominant species, Teladorsagia circumcincta L3. Despite consistent management throughout the study, the results show variation in gastrointestinal nematode species composition with time and between age groups, that was potentially associated with weather conditions. The F200Y benzimidazole resistance mutation is close to genetic fixation in the T. circumcincta population on this farm. There was no evidence of variation in isotype-1 β-tubulin single nucleotide polymorphisms frequency between age groups, and no genetic evidence of reversion to benzimidazole susceptibility, despite targeted benzimidazole usage. This study highlights the need to include speciation when investigating gastrointestinal nematode epidemiology and anthelmintic resistance, and serves as an example of how genetic data may be analysed alongside species diversity and faecal egg counts, when markers for other anthelmintic classes are identified.

1 A survey of anthelmintic resistance in Angus bulls participating in centralized performance tests in Appalachia

Abstract Parasitism in weaned calves and anthelmintic resistance can negatively impact performance and reduce profitability. To better understand anthelmintic resistance, bulls were evaluated for fecal egg count (FEC) at performance test facilities in Virginia and West Virginia. Over a two-year period, 532 Angus bull calves were tested at bull development facilities in Wardensville, WV (n = 274), Culpeper, VA (n = 167), and Wytheville, VA (n = 91). Fecal samples were collected upon arrival and 14 d later, representing the warm-up or transition period. At arrival, bulls were treated with either albendazole (Wardensville) or moxidectin (both VA tests). Data were analyzed via the general linear model of SAS with fixed effects of station and year. Correlation analysis of arrival FEC and transition ADG was analyzed using the correlation procedure in SAS. The average FEC reduction (FECR) in bulls at Wardensville was 98%; whereas, FECR at Culpeper and Wytheville was 46% and 16% respectively. Average FEC of bulls at Wytheville, Culpeper and Wardensville were different (P &amp;lt; 0.05) after treatment and had a FEC of 133, 51, 3 eggs/g, respectively. Transition ADG favored bulls from Wardensville and Culpeper (2.43 and 2.31 kg/d; P &amp;gt; 0.05) where bulls at Wytheville had lower ADG compared to either station (1.03 kg/d; P &amp;lt; 0.01). Correlation between arrival FEC and transition ADG was negative for bulls in Wardensville (-0.22; P = 0.0003). This same response was not observed at other stations. Lack of a correlation was most likely due to infection level being so low that abundant feed resources masked effects of parasitism, or parasitism was so great that all cattle transitioned poorly. Nonetheless, these data clearly demonstrate the efficacy of albendazole in significantly reducing fecal egg output in bull calves and identify potential resistance to moxidectin.

Nematode parasite eggs in pasture soils and pigs on organic farms in Sweden

The EU regulation for organic pig production requires outdoor access to promote the animal welfare. This may increase the risk of infection of the common pig parasites, Ascaris suum and Trichuris suis, because their eggs can survive for many years in the soil. The egg contamination of these parasites in outdoor areas with different managements and the faecal egg output from the pigs was investigated on 11 Swedish organic pig farms in 2008. We found eggs of A. suum and, to a minor extent, T. suis in the soil from outdoor areas, which had previously been used for pig rearing and/or for spreading of pig manure. Piglets and their dams were turned out on pastures included in a crop rotation, and these areas had a mean of 2500 A. suum and 40 T. suis eggs per kilogram soil. When the pigs were 12-week-old, the faecal egg counts (FECs) of A. suum were positively correlated with the egg concentration in pasture soils before pig turnout. The areas used by dry sows had a mean of 11,700 A. suum and 220 T. suis eggs per kilogram soil. The highest egg concentrations in the soil were found in areas, frequently used by pigs in the most recent years. To minimise pasture contamination with parasite eggs, it is advised to have a crop rotation system and to inactivate parasite eggs in pig manure before spreading it. Parasite control needs further development to protect suckling piglets from infections due to environmental parasite egg contamination.

Recombinant Opisthorchis viverrini tetraspanin expressed in Pichia pastoris as a potential vaccine candidate for opisthorchiasis.

Opisthorchiasis affects millions of people in Southeast Asia and has been strongly associated with bile duct cancer. Current strategic control approaches such as chemotherapy and health education are not sustainable, and a prophylactic vaccine would be a major advance in the prevention of the disease. Tetraspanins are transmembrane proteins previously described as potential vaccine candidates for other helminth infections and are also found in the membranes of the tegument and extracellular vesicles of O. viverrini. Here, we investigated the potential of a recombinant protein encoding for the large extracellular loop of O. viverrini tetraspanin-2 (rOv-LEL-TSP-2) in a hamster vaccination model. Hamsters were vaccinated with 50 and 100 μg of rOv-LEL-TSP-2 produced from Pichia pastoris yeast combined with alum CpG adjuvant via the intraperitoneal route. The number of worms recovered from hamsters vaccinated with rOv-LEL-TSP-2 was significantly reduced compared to adjuvant control groups. Fecal egg output was also significantly reduced in vaccinated animals, and the average length of worms recovered from vaccinated animals was significantly shorter than that of the control group. Vaccinated animals showed significantly increased levels of anti-rOv-TSP-2 IgG in the sera after three immunizations, as well as increased levels of several T helper type 1 cytokines in the spleen including IFN-γ and IL-6 but not the Th2/regulatory cytokines IL-4 or IL-10. These results suggest that rOv-TSP-2 could be a potential vaccine against opisthorchiasis and warrants further exploration.

Superimposed visceral leishmanial infection aggravates response to Heligmosomoides polygyrus

BackgroundPolyparasitism is the rule in all animal species, including humans, and has an important role in pathogenicity, diagnosis and control measures. Among them, co-infections by gastrointestinal helminths and protists are very prevalent under natural conditions but experimental infections are relatively scarce. Thus, despite the frequent association of visceral Leishmania infections and intestinal helminth parasitism the experimental co-infection has not been addressed. Heligmosomoides polygyrus, an intestinal nematode of mice, is related to other helminths causing important pathologies and is a model species for immunological studies. Mice are valuable experimental model for visceral leishmaniasis.MethodsBALB/c mice infected with H. polygyrus (200 third-stage larvae, L3) were subsequently infected seven days later with Leishmania infantum (107 promastigotes) with the aim of determining the effect of the overinfection on the host response to the primary infection with the helminth.ResultsOverinfection with the protist did not affect the establishment rate of the nematode but induced a higher fecal egg output. Helminth burdens in co-infected animals were significant at the end of the experiment. Early unspecific immune suppression induced by the nematode in mesenteric lymph nodes was not switched by L. infantum infection. Co-infection elicited a higher serum antibody (IgG1) response against the helminth.ConclusionsVisceral leishmanial overinfection aggravated the early host response against primary infections with the intestinal helminth. This effect was evidenced by an increased longevity and higher production of non-protective antibodies.

Vaccination of lambs against Haemonchus contortus with the recombinant rHc23. Effect of adjuvant and antigen dose.

Haemonchus contortus is the most pathogenic gastrointestinal helminth of small ruminants. Natural or experimental repeated infections and several native antigens confer a partially protective immune response but vaccination with subunit antigens has been elusive. Promising results have been obtained with a recombinant form of a somatic antigen (rHc23). In this paper we present the results obtained in vaccination trials in lambs using two dosages of rHc23 and standard adjuvants. Six-months old Manchego females lambs were vaccinated with rHc23 (50 or 200 μg/dose) adjuvanted with 1mL aluminum hydroxide on days -42, -28 and -14 or with 200 μg/dose rHc23 and 5 mg Quil A on days -49, -28 and -7. Control lambs were kept receiving only the adjuvants the same days or no treatment. Moreover one group did not receive any treatment or infection. On day 0 vaccinated lambs, untreated animals and those receiving the adjuvant were infected per os with a monospecific single infection of 4000 L3 of H. contortus. Infection was kept for 58 days and follow-up included the determination of serum specific antibody response (ELISA, WB), hematological parameters (eosinophil counts, hematocrit) and fecal egg counts (epg). Absence of hematocrit alterations, reduction of helminth’s eggs output and abomasal parasite burden at the end of the experiment were the efficacy criteria of vaccination with the recombinant. Immunization with both adjuvants and antigen dosages elicited strong antibody responses particularly with Quil A. Vaccinated groups showed significant reduction of fecal egg excretion and abomasal helminth burdens. Highest protection of lambs against challenge was achieved with aluminum hydroxide and 200 μg/dose rHc23 with a reduction of over 70% of the abomasal burden and over 80% of fecal egg output. Results suggest that rHc23 could be a valuable recombinant candidate for vaccination against haemonchosis. No clear relationship was found between antibody levels and protection this pointing towards involvement of both humoral and cellular components in the protective response elicited by rHc23.

Evaluation of the anthelminthic potential of Duranta erecta L. (Verbenaceae) fruits used in Nigerian ethnomedicine as a vermifuge

Ethnopharmacological relevanceDuranta erecta L. fruits have been reported to have in vitro anthelminthic properties. People living in the tropical South-Eastern part of Nigeria use the plant in folk medicine for the treatment of malaria, abscesses and as a vermifuge. Although there are a few reports about its in vitro anthelminthic activity against different worm categories, scientific reports regarding its in vivo anthelminthic activity are limited. Aim of the studyThis study was designed with the aim of determining the potential of the plant as an anthelminthic and to verify the claims made by its local users. Materials and methodsAcute toxicity of the plant extract was determined using Lorke's method. Anthelminthic activity was investigated using adult male albino mice experimentally infected with Heligmosomoides bakeri infective L3. Graded ascending doses of the plant extract and Albendazole respectively were orally administered to the mice in the infected groups. Corprological and haematological parameters were recorded within the study period. Twenty-eight (28) days post-infection, all infected mice were humanely sacrificed and the Post-Mortem Adult Worm Burden (WB) was estimated and recorded. ResultsThe results showed that the extract had an LD50 greater than 5000 mg/kg BW and therefore was not acutely toxic for oral use. It also showed that the plant extract was unable to eliminate the faecal egg output or adult worms in the gastrointestinal tract of infected animals even at the high doses used in the study. This was in contrast to Albendazole which significantly (p < .05) reduced faecal egg counts and worm burdens by 71% and 92% respectively in treated mice. Following infection, there was anaemia in all infected groups seen from results of erythrocytic parameters. Treatment with the plant extract, regardless of the dose, was unable to effectively reverse the effect of parasite infection on erythrocytic parameters. However, treatment with Albendazole positively reversed the anaemia, restoring the mice to pre-infection values by the end of the experiment. The results showed significant (p < .05) increase in WBC counts across all groups following infection with the parasite. Treatment with the plant extract and Albendazole respectively, significantly (p < .05) reduced the WBC counts to near pre-infection values in most treatment groups. ConclusionAs a result of the poor anthelminthic effects recorded in the study, it is therefore recommended that Duranta erecta L. fruits be explored for its other useful effects rather than as an anthelminthic.

Effect of providing pellets enriched with spores of parasiticide fungi to grazing cattle on the dynamics of faecal trematode egg-output

Effect of providing pellets enriched with spores of parasiticide fungi to grazing cattle on the dynamics of faecal trematode egg-output

Immune protection conferred by recombinant MRLC (myosin regulatory light chain) antigen in TiterMax Gold® adjuvant against experimental fasciolosis in rats

Protection against experimental fasciolosis in rats immunized with recombinant myosin regulatory light chain (MRLC) in TiterMax Gold® adjuvant was assessed. The experimental trial consisted of four groups of 15 animals; group 1 was unimmunized and infected, group 2 was immunized with MRLC in adjuvant and infected, group 3 was infected and immunized with adjuvant only and group 4 was unimmunized and uninfected. Immunization with MRLC in TiterMax Gold® adjuvant (group 2) induced a reduction in fluke burdens of 51.0% (p<0.001) when compared with the adjuvant control group, and 61.5% (p<0.001) when compared with the unimmunized infected controls. There was a reduction in fecal egg output in group 2 of 44.8% and 37.3% compared with group 1 and group 3, respectively; although this difference was not statistically significant. Measurement of cytokine levels revealed higher levels of TNF-alpha and IL-2 as well as lower levels of IL-4 in group 2 during the chronic stage of infection (p<0.05), along with higher levels of IFN-gamma during early stages of infection (p<0.05). These results suggest a mixed Th1/Th2 phenotype immune response; however predominance of Th1 cytokines was observed. Levels of anti-MRLC serum IgG in group 2 were significantly higher than controls at the time of euthanasia (p<0.05). This is the first report of immunization with recombinant MRLC in rats, demonstrating that this antigen significantly reduces fluke burdens, increases the Th1 immune response and encourages further studies to improve the vaccine’s efficacy.

Anthelmintic resistance status of gastrointestinal nematodes of sheep to the single or combined administration of benzimidazoles and closantel in three localities in Mexico

Veterinaria Mexico OA ISSN: 2448-6760 Cite this as: Alcala Canto Y, Sumano Lopez HS, Ocampo Camberos L, Gutierrez L. Anthelmintic resistance status of gastrointestinal nematodes of sheep to the single or combined administration of benzimidazoles and closantel in three localities in Mexico. Veterinaria Mexico OA. 2016;3(4). doi: 10.21753/vmoa.3.4.374 Sheep production requires the constant assessment of parasitic burden and the efficacy of existing treatments for proper management. In this study, the administration of five different treatments was evaluated for the reduction of the percentage of eggs per gram of feces (EPG) shed by gastrointestinal nematodes (GIN) from sheep on three different sheep-breeding farms in Mexico (Texcoco, Estado de Mexico; Hueytamalco, Puebla; and Tlaltizapan de Zapata, Morelos). In these farms, ivermectin and benzimidazole derivatives had been routinely administered for two consecutive years. To determine whether drugs with different pharmacological properties decreased GIN fecal egg excretion, the treatments closantel (CLOS), albendazole (ABZ) and fenbendazole (FBZ) were administered alone and in combinations of CLOS + ABZ and CLOS + FBZ, to five groups of sheep, with an additional untreated control group on each farm (n = 28 per flock). Anthelmintic resistance was determined using Fecal Egg Count Reduction Tests (FECRT) as recommended in the guidelines of the World Association for the Advancement of Veterinary Parasitology. Fecal samples were collected 14 and 21 days after treatment. The anthelmintic resistance status was determined based on the reduction in the fecal egg count arithmetic mean and 95 % confidence limits. According to the FECRT, resistance developed to CLOS, ABZ, FBZ and CLOS + FBZ because the mean percentage of EPG reduction was ≤ 95 % with a lower confidence limit of ≤ 90 %. By contrast, nematode susceptibility was confirmed for the CLOS + ABZ combination, as it reduced the percentage of GIN fecal egg output by 96.46 ± 3.04 % (day 14) and 96.88 ± 3.04 % (day 21). Based on the morphometric identification of larvae, Haemonchus spp., Cooperia spp. and Teladorsagia spp. were the most abundant genera on all farms before the administration of these five treatments. In conclusion, the use of the anthelmintic combination of closantel plus albendazole may reduce the development of anthelmintic resistance in gastrointestinal nematodes. Figure 1. Marginal means ± SD of the percentage reduction in egg count on days 14 and 21 after treatment of sheep on three farms (n = 28 per flock) with fenbendazole (FBZ), closantel (CLOS), albendazole (ABZ), closantel + fenbendazole (CLOS + FBZ) and closantel + albendazole (CLOS + ABZ).

Faecal egg counts and immune markers in a line of Scottish Cashmere goats selected for resistance to gastrointestinal nematode parasite infection

This study aimed to investigate the effect of selection for low faecal egg count (FEC) in Scottish Cashmere goats in comparison to a control line of unselected goats grazing the same pasture. Goats from generations F2 through to F9 were monitored for FEC, bodyweight, peripheral eosinophilia and IgG, IgA and IgE response against Teladorsagia circumcincta from the end of their first grazing season, through winter housing (during which a single artificial challenge dose of 10,000 drug susceptible T. circumcincta was given) and the following full grazing season. The study demonstrated that selected line animals excreted a significantly lower number of parasite eggs (P<0.01) in the majority of generations examined. Liveweight productivity was unaffected by selection. Although selected line animals had greater numbers of circulating eosinophils in many of the generations (four generations of males and six generations of females, P<0.05), there was no direct link between eosinophilia and reduced FEC. Immunoglobulin levels showed no consistent difference between selected and control lines. IgG, IgA and IgE levels were not different between lines over the whole dataset(P>0.05), although the selected line had significantly elevated or reduced levels (P<0.05) for all three within individual generations. There were significant associations between increased IgG and reduced FEC under artificial infection conditions (P=0.02). Increased IgA was also significantly associated with elevated FEC during the second grazing season (P<0.001). The study demonstrates that selection produced a line of goats with consistently reduced FEC compared with control animals, but did not identify a clear relationship between any of the immune markers measured and faecal egg output.

A model for the development and growth of the parasitic stages of Parascaris spp. in the horse

Literature documenting the growth and development of Parascaris spp. infections was used to develop a model describing worm dynamics in the young horse. The model incorporates four main variables; the rate at which larvae migrate through host tissues to return to the small intestine, the proportion of migrating larvae which succeed in returning to the small intestine, the rate of growth in size of maturing and adult worms and the survival rate of maturing and adult worms. In addition, the number of eggs laid each day by adult female worms is calculated as a function of worm size (length) and is used to calculate faecal egg output of the foal. Published data describing the rate of migration through host tissues, and the growth of worms following their return to the small intestine, was used to derive relationships describing these processes. However, only limited data exists relating the survival of migrating larvae and mature worms in the intestine to host age and experience of infection. Therefore, relationships and coefficients describing these variables were modified so that output aligned with published experimental results. As a consequence, the model has not yet been evaluated against an independent data set, and so remains as the best ‘current hypothesis’ for the dynamics of this parasite. Hopefully, future experiments designed to test specific assumptions and outputs of the model will lead to a better understanding of the biology of this important parasite. For example, the most influential variable in determining model output is the survival rate of worms in the small intestine. In the model, worm survival declines in response to both the increasing age of the horse and the increasing cumulative length of worms in the intestine (used as a proxy for crowding). Given the importance of this variable to model behaviour and the paucity of experimental data on this topic this would seem a priority for future study. Initial experiments using the model suggest that a single anthelmintic treatment, administered soon after patency of initial infection, may effectively control environmental contamination with Parascaris spp. eggs while allowing a small ‘refugia’ of susceptibility to delay the emergence of anthelmintic resistance. Further evaluations of the practicality of this approach may be worthwhile.

Assessment of flukicide efficacy against Fasciola hepatica in sheep in Sweden in the absence of a standardised test

Anthelmintic resistance (AR) to Fasciola hepatica is emerging worldwide. Recently, AR to the adulticide compound albendazole (ABZ) was shown in Argentina and Spain. In Sweden, ABZ treatment failure against F. hepatica was first reported in sheep in 2012. The present study tested the efficacy of ABZ and triclabendazole (TCBZ) in sheep naturally infected with F. hepatica using a combination of three different diagnostic methods: faecal egg counts (FEC), coproantigen ELISA (cELISA) and Fasciola egg hatch test (FEHT). Two deworming trials, in November 2014 and January 2015, were performed on two sheep farms (farms A and B) in south-western Sweden. Except ABZ in November, treatment with ABZ or TCBZ achieved sufficient efficacy (97–100%) against adult F. hepatica on farm A. In contrast, ABZ treatment failed in the sheep flock on farm B, despite low initial faecal egg output. On farm B, ABZ efficacy based on FEC was 67% (95% CI: 35–84) and four of eight ewes tested were coproantigen-positive 21 days post-treatment. Ovicidal activity of ABZ against Fasciola eggs in isolates from both farms and one additional bovine isolate were tested by FEHT to exclude the presence of juvenile flukes and other factors such as dosing failure and poor quality of drug product. Irrespective of drug trial, data from FEHT showed significantly lower ovicidal activity of ABZ for the ovine farm B isolate than for the isolate from farm A. This confirms that the low efficacy of ABZ in sheep flock B was associated with ABZ resistance. Overall, the usefulness of three complementary methods for detection of ABZ resistance in the field was demonstrated.