J.C. Williams

Effect of gastrointestinal nematode and liver fluke infections on weight gain and reproductive performance of beef heifers

Spring born, crossbred beef heifers (n=372) were utilized over four years to measure reductions in body weights, reproductive performance and calf weights caused by gastrointestinal nematodes (primarily Ostertagia ostertagi) and the bovine liver fluke (Fasciola hepatica) and to differentiate losses attributable to each type of parasitism. Each year, weaned heifers were allotted to one of the four treatment regimens: Group 1, untreated controls; Group 2, treated for nematodes; Group 3, treated for liver fluke; and Group 4, treated for both nematodes and liver fluke. Nematodes were controlled with subcutaneous injections of either ivermectin (Ivomec, Merial) or doramectin (Dectomax, Pfizer), both at the recommended dose of 200 ug/kg bodyweight. Clorsulon (Curatrem, Merial) drench was given at the recommended rate of 7 mg/kg bodyweight to control flukes. Treatments and fecal collections were initiated at allotment each year and were repeated at 28-84-day intervals until palpation for pregnancy diagnosis. Open heifers were removed from the study at this time. Treatment dates were based on expected length of treatment efficacy, the stage of growth of the heifers and the seasonal risk of infection by the parasites. Pregnant females were pooled and received their assigned treatments prior to their calving and breeding seasons and remained together until their calves were weaned. Heifers treated for nematode infections were heavier and had higher condition scores (P<0.01) than untreated control heifers at initiation of breeding, and maintained that difference through pregnancy diagnosis. Liver fluke infection did not affect heifer gains or condition scores prior to palpation (P<0.01). At palpation, heifers treated for both forms of parasitism had the highest condition scores and weight gains (P<0.01), and also higher pregnancy rates than control heifers and heifers treated for nematodes only (P<0.01). Pregnancy rates for heifers treated for flukes only were not significantly different from those treated for both nematodes and flukes. Heifers treated for nematodes weaned heavier calves than those not treated for nematodes (P<0.05).

A comparison of persistent anthelmintic efficacy of topical formulations of doramectin, ivermectin, eprinomectin and moxidectin against naturally acquired nematode infections of beef calves☆

Persistent anthelmintic efficacy of topical formulations (all at a dosage of 500 microg/kg) of doramectin (DOR), ivermectin (IVM), eprinomectin (EPR) and moxidectin (MOX), in comparison with untreated control cattle (CONT), was observed in stocker beef calves during a 112-day winter-spring grazing trial. Five groups of 15 calves per group were grazed on 15 separate 2 ha pastures following random assignment of animals to specific pastures and then to treatment groups. All of the 5 treatments were represented in each of the 15 pastures. All cattle were weighed on study Days 1, 0, 28, 56, 84, 111 and 112. Fecal samples for nematode egg counts were collected on Days 7, 0, at 7 day intervals through Day 56 and at 14 day intervals to Day 1 12. Pooled group fecal cultures for determining generic composition of nematode infections were prepared at 14 day intervals throughout the study. As based on fecal egg counts, anthelmintic activity of EPR and MOX was greater (p < 0.05) than values for IVM or CONT through Day 28. Activity of DOR was greater (p < 0.05) than that of IVM on Days 7 and 14 only. Although significance levels varied little among treated groups from Day 42 to the end of the study, egg counts and percent reduction values of EPR and MOX remained consistently lower numerically than egg counts and higher than reduction values respectively, of DOR and IVM through Day 70. From Day 70 on, IVM counts were numerically, but not significantly higher than values of CONT. Based on larval culture, Cooperia predominated from Day 0 through 28 and again from Days 70 to 98; Ostertagia was second in prevalence with highest percentages, which exceeded those of Cooperia, between Days 42 and 70. Bodyweights of all treated groups, with exception of IVM, were always significantly greater (p < 0.05) than weights of CONT. Weights of IVM were numerically greater, but not significantly greater than CONT only on Days 84 and 112. From Day 56 on, there were no significant differences between weights of DOR, EPR and MOX, however, numerical values for MOX were consistently higher than values for the other two. Final average total bodyweight gains were: 153.7 kg for MOX, 148.5 kg for EPR, 146.9 kg for DOR, 139.7 kg for IVM and 127.7 kg for CONT.

A comparison of the efficacy of two treatments of doramectin injectable, ivermectin injectable and ivermectin pour-on against naturally acquired gastrointestinal nematode infections of cattle during a winter-spring grazing season☆

Four groups of 18 crossbred beef steer calves (three replicates of six per group) were used to compare persistent efficacy of doramectin injectable, ivermectin injectable and ivermectin pour-on against naturally acquired infections of gastrointestinal nematodes during winter-spring grazing in Louisiana. The experiment was initiated on January 11. Treatments administered on Day 0 and again on April 5 (Day 84, 12-week interval) were: Group 1, untreated controls (CONT); Group 2, doramectin (DOR) at 200 micrograms/kg, s.c. injection; Group 3, ivermectin (IVM-INJ) at 200 micrograms/kg, s.c. injection; Group 4, ivermectin pour-on (IVM-PO) at 500 micrograms/kg, back midline. The cattle were weighed and fecal samples (for egg counts and for culture-larval identification) were collected at regular intervals throughout the 161 day experiment. In the interval between Day 0 and 84, arithmetic mean egg counts of the CONT group averaged about 890 eggs per gram, but then decreased markedly between Days 119 and 126, and remained at a lower plane for the remainder of the experiment. From Day 28 to 56, egg counts of the DOR group were consistently lower (P < 0.05) than those of controls and both IVM-treated groups. Egg counts of the DOR group were always lowest after the second treatment, but differed (P < 0.05) only from IVM-PO counts between Days 119 and 140 (35 and 56 days after the second treatment). Ostertagia was the predominant genus, followed by Cooperia in all four groups. Oesophagostomum, Trichostrongylus, Haemonchus, and Bunostomum were other genera identified. Bodyweights of the DOR group remained significantly greater (P < 0.05) than those of all other groups from Day 112 through the end of the experiment. Total gains for the CONT, DOR, IVM-INJ, and IVM-PO groups were 96, 159, 147, and 150 kg, respectively; treated groups were significantly (P < 0.05) greater than CONT, but differences among treated groups was not significant (P > 0.05).

Plasma pepsinogen, inhibited larval development, and abomasal lesions in experimental infections of calves with Ostertagia ostertagi

Abstract Single doses of Ostertagia ostertagi , followed in 42 days by multiple increasing doses in calves, were monitored by fecal egg counts and plasma pepsinogen. The level of plasma pepsinogen increase was related to the increase in graded levels of inoculation and to the fecal egg counts. Plasma pepsinogen in uninfected controls remained below 1 IU/L. Plasma pepsinogen in all calves reached levels greater than 5 IU/L at 48 days of the extended inoculation period, although fecal egg counts remained low in the previously inoculated calves. The previously infected calves had a higher proportion of early fourth-stage larvae, while larger adult worm burdens were found in the previously uninfected calves. Early fourth-stage larvae were observed in extra-glandular sites, notably between the glandular epithelium and basement membrane or within the lamina propria. An immunological response of the host was suggested by the lymphoid cell infiltration in the mucosa. This host immune response may account for the greater larval inhibition exhibited by the previously infected calves.

Comparative efficacy of ivermectin pour-on, albendazole, oxfendazole and fenbendazole against Ostertagia ostertagi inhibited larvae, other gastrointestinal nematodes and lungworm of cattle

An experiment was conducted to evaluate the current efficacy of albendazole (ABZ), oxfendazole (OXF) and fenbendazole (FBZ) compared with ivermectin pour-on (IVM-PO) against inhibited early fourth-stage larvae (IEL4) of Ostertagia ostertagi, other gastrointestinal nematodes and lungworm of cattle during spring in Louisiana. Twenty-five crossbred beef heifer calves of 235 kg average weight and 10-12 months of age were acquired in late winter and grazed for 9 weeks on pasture contaminated with O. ostertagi and other nematodes until May 15. The cattle were weighed and randomly allotted into 5 groups of 5 calves on May 16 (day 0) and treatments were as follows: group 1, nontreated controls (CONT); group 2, IVM-PO on mid-backline at 500 micrograms/kg; group 3, ABZ suspension (oral) at 10 mg/kg; group 4, OXF suspension (oral) at 4.5 mg/kg; group 5, FBZ suspension (oral) at 5 mg/kg. After treatment and confinement in separate pens for each group, approximately equal numbers of cattle from each group were necropsied daily between days 29-31. Mean numbers of O. ostertagi developmental stages present in CONT were: adult, 5234; developing (DL4), 3130; IEL4, 44,077. The mean percentage of IEL4 was 84.1. Cooperia spp. were the second most prevalent in CONT (20,307) and smaller numbers of abomasal and intestinal species and Dictyocaulus viviparus were present in nearly all CONT. Percent reductions for the four compounds against O. ostertagi adult, DL4 and IEL4, respectively, were IVM-PO: 99.7, 98.3, 98.1; ABZ: 74.1, 76.5, 75.3; OXF: 78.5, 42.1, 32.0; FBZ: 63.6, 17.7, 39.7. Efficacy of IVM-PO was greater (P < 0.05) against all O. ostertagi stages than the benzimidazole (BZ) drugs, except for ABZ (DL4). There were no significant differences in group means (except for C. punctata adult males, P < 0.05 lower for IVM-PO) or wide variation in reduction percentages for other abomasal and intestinal species and D. viviparus between IVM-PO and BZ drugs. The low efficacy of all three BZ drugs for O. ostertagi, but especially for OXF and FBZ, under conditions of this experiment, were suggestive of drug tolerance to dosages employed or resistance. However, problems of drug availability/concentration in the abomasum, and the factor of IEL4 and DL4 replacing adult worms after treatment cannot be excluded. Efficacy of the BZ drugs against all other species were essentially similar to that of IVM-PO.

Epidemiology of Ostertagia ostertagi in weaner-yearling cattle☆

Epidemiologic events in the life cycle of Ostertagia ostertagi are best known in the weaner-yearling phase of cattle development throughout the concentrated cattle-rising areas of the world. Animal and pasture management demands placed on this age class are greater than for suckling calves and adult stock in either beef or dairy breeds. This fact alone would likely account for a higher prevalence of clinical and subclinical disease in weaner-yearlings. Additionally, the developing immune response provides relatively early protection against intestinal genera such as Cooperia and Oesophagostomum, but is delayed against Ostertagia ostertagi and Trichostrongylus axei. Both Type I and Type II disease may occur within the weaner-yearling stage. Factors affecting population changes of Ostertagia ostertagi have been described as extrinsic, i.e. weather-climate and grazing management, and intrinsic or host factors, i.e. age, sex, immune status, heredity and reproductive state. Immune status, particularly in weaner-yearlings, may be of primary importance, as affected by host and extrinsic factors. With slow development of protective immunity against Ostertagia ostertagi in calves, the possible role of immunity in both induction of inhibition and larval maturation, the potential immunopathologic involvement in pathogenesis of Type II disease, hypersensitivity to larval intake in resistant adult cows, and the reported delay of a protective response following anthelmintic prophylaxis in younger cattle, the immune response may have profound influence on epidemiologic variation through age classes. Although continual epidemiological observations from birth to early adulthood in the same cattle have not been undertaken, some notable studies in the UK, the Netherlands, and Denmark have closely examined epidemiological events through first and second grazing seasons.

Preliminary report: Immunodiagnosis of pre-type II ostertagiasis

Ostertagia ostertagi soluble antigens were prepared by gel electrophoresis and electrophoretic transfer onto nitrocellulose for enzyme-linked immunosorbent assays with serum probes. Serologic responses to L3-derived antigen of approximately 32 kDa may be unique and diagnostic for cattle harboring inhibited larvae, or pre-Type II ostertagiasis. Specificity was evaluated by comparing sera from pre-Type II cattle to sera from Type I, uninfected, Fascioloides magna infected, Fasciola hepatica infected or Cooperia oncophora infected cattle.

Dose confirmation of moxidectin 0.5% pour-on against adults and fourth-stage larvae of various Cooperia spp. and Trichostrongylus colubriformis in Louisiana.

Thirty-five castrate or intact Holstein male calves, ranging in weight from 122 to 210kg, were used in the study. On study Days -15 and -14, all study calves were treated with fenbendazole 10% paste at 10mg/kg to remove existing nematode infections. All cattle had zero egg counts on Day -1. Experimental infections of a mixed species inoculum were administered to all calves on Day 0. The inoculum consisted of Cooperia spp. (primarily C. punctata, but also C. pectinata, C. spatulata, C. oncophora and C. surnabada-total 40,961); Ostertagia ostertagi-1550; Trichostrongylus colubriformis-4996; and Oesophagostomum radiatum-38. Necropsy results from two of three monitor calves slaughtered on Day 6 after infection indicated that Day 6 was an appropriate time to evaluate efficacy of moxidectin against fourth larval stages (L(4)). The remaining 32 calves were randomly allotted to four groups of eight based on body weights. Eight calves (Group 1) were treated with moxidectin 0.5% pour-on at 0.5mg/kg on Day 6 to evaluate efficacy against nematode larval stages; eight control calves (Group 2) were matched with these principals. Eight calves (Group 3) were also treated with moxidectin pour-on at the same dosage on Day 23 in order to determine efficacy against adult nematodes; eight control calves (Group 4) were matched with these principals. In both cases, principals and controls of the Days 6 and 23 treatments were necropsied at 14-15 days after treatment. C. punctata was the only species found in a sufficient number of controls to evaluate moxidectin efficacy against the L(4). Moxidectin pour-on was not effective (P<0.05) against C. punctata L(4) by arithmetic means, but was highly effective based on geometric means. Regardless of whether arithmetic or geometric means were used for percent efficacy calculations, moxidectin pour-on was demonstrated to be highly effective (>99%) against the adult stages of C. oncophora, C. punctata, C. spatulata, C. surnabada, Cooperia spp. adult females and T. colubriformis adults.

Efficacy of levamisole against Ostertagia ostertagi in Louisiana cattle during maturation of inhibited larvae (September) and during minimal inhibition (December/January)☆

Levamisole (LEV) was tested in four experiments to compare efficacy values against Ostertagia ostertagi when larval maturation was occurring (September), following inhibition and also when populations were expected to be largely adult (winter). A primary objective was to determine the importance of developing fourth-stage larvae (DL4) and inhibited, early fourth-stage larvae (EL4) in replacing adult worms lost through treatment and the effect of this on reduced efficacy against adult worms. Young crossbred beef calves ranging in weight from 150 to 230 kg were used in the first (September 1981), second (September 1983) and third experiments (January 1987). Jersey calves of 110 kg average weight were used in the fourth experiment (December 1988). Calves were randomized to groups according to weight and group sizes ranged from three to five calves. All parasite infections were naturally acquired, but a mixture of nematode third-stage larvae (L3) (22,500 per calf), including 20% Ostertagia ostertagi, was inoculated into Jersey calves of Experiment 4 following a 2 week exposure to natural infection. All LEV treatments were by subcutaneous injection at dosages of 6 and 8 mg kg-1. Treatment with ivermectin was used only in Experiment 3 as an efficacy reference. All calves were killed at 8-10 days after treatment. The efficacy of LEV against all developmental stages of Ostertagia ostertagi was consistently low in all experiments and a dose-dependent response was not evident. Large numbers of all Ostertagia ostertagi developmental stages were present in non-treated calves in both September experiments. Percent reduction of adults, DL4 and EL4 at the 6 mg kg-1 and 8 mg kg-1 dosages, respectively, were adults, 51.7 and 23.6 (1981), 8.7 and 51.3 (1983); DL4 40.3 and 13.2 (1981), 37.9 and 33.1 (1983); EL4, 19.6 and 0 (1981), 59.6 and 42.9 (1983). Smaller numbers of Ostertagia ostertagi were present in winter experiments and adult worms greatly outnumbered larval stages. Percent reductions of adults, DL4 and EL4, respectively, were (1987) LEV 6 mg kg-1, 40.2, 0 and 0; ivermectin 200 micrograms kg-1, 98.7, 97.7 and 100.0; (1988) LEV 6 mg kg-1, 62.4, 100.0 and 100.0; LEV 8 mg kg-1, 49.1 65.0 and 74.1. Too few larval stages were present in the latter experiment for valid efficacy values.(ABSTRACT TRUNCATED AT 400 WORDS)

Sequential histopathologic changes of type I, pre-type II and type II ostertagiasis in cattle

Yearling cattle in Louisiana were examined at monthly intervals for abomasal nematode burdens and histological lesions over a year. Tracer calves were grazed for 3 to 4 weeks and removed from pasture for 2 to 3 weeks, then slaughtered; a few animals were killed in extremis shortly after removal from pasture. Histological changes were correlated with worm burdens and characterized according to the type of Ostertagia ostertagi infection present. In cattle with acute Type I ostertagiasis, changes varied from eosinophil infiltration to glandular dilation and slight mucous cell hyperplasia with submucosal edema. During the summer months the cattle had worm burdens that were primarily early 4th stage larvae (EL4), with changes characterized by minimal glandular dilation and mucous cell metaplasia and moderate lymphoid cell proliferation and with intramucosal migration of EL4. In the autumn, the maturation of EL4 produced the Type II syndrome with severe glandular changes, prominent mucosal hyperplasia and marked lymphoid cell accumulation. With increased duration of the pre-Type II interval, there was greater development of the subepithelial lymphoid tissue and increased frequency of epithelial globule leukocytes. The lymphoproliferation which occurred during the prolonged pre-Type II interval appeared to be related to the increased severity and mortality seen with the Type II ostertagiasis syndrome.