Concurrent daily infection of calves with Fasciola hepatica and Ostertagia ostertagi.

Three groups of calves were infected daily with either 1500 Ostertagia ostertagi larvae, 20 Fasciola hepatica metacercariae, or 1500 O ostertagi plus 20 F hepatica metacercariae. Weekly measurements were taken of calf weight, faecal egg output, plasma concentrations of albumin, plasma activities of sorbitol dehydrogenase, gamma glutamyl transpeptidase and pepsinogen and standard haematological indices. Calves were killed either 10 or 21 weeks after daily infections began. F hepatica infection had little influence on the size and structure of the O ostertagi worm population or vice versa. Mean worm burdens found at 20 weeks in those animals infected with both F hepatica and O ostertagi were 293 flukes and 20,641 nematodes. While this level of infection is similar to that seen in the disease complex in the field, there was no evidence of clinical disease or any difference in weight gain between the groups in this experiment. Factors other than additive worm burdens are obviously important for the expression of disease under field conditions.     

Infection with Ostertagia ostertagi in goats and calves

In order to determine the usefulness of the goat as a model host for Ostertagia ostertagi, a series of experiments was conducted in which young goats and calves were experimentally infected with L3 of calf-source and goat-source isolates. The goat-source isolate was derived from a continuous passage of the bovine parasite in goats. Patent infections resulted in 73 out of 86 inoculated goats (85%). The largest number of patent infections was observed when inoculation consisted of a single dose of goat-source larvae. Percent establishment of infection was generally low in goats inoculated with either larval source. Time taken to achieve patency in goats was frequently within the range normal for cattle infections, but was often extended (21-67 days). With the exception of the generally higher level of establishment of goat- or calf-source isolates in calves and the low frequency of the vulval flap in adult female worms established in goats, little difference was observed in percent establishment or worm population characteristics of the two isolates in goats as based on source of larval inoculum, inoculation course, and age of host at inoculation. Prolonged passage of infection in goats did not result in stabilized isolate more adapted to the goat or less adapted to calves. Fecal egg counts were generally minimal or negative in goats during the first 30 days of infection, but were often increased and not substantially lower than counts in calf infections after 60 or 90 days. Low level egg counts in goats were observed to persist for up to 17 months. During the spring of 2 years, goat kids grazed on a cattle pasture acquired O. ostertagi infections which included adult worms, but a larger number of early L4. The latter were presumed to be inhibited in development just as such inhibition occurs in cattle during spring.     

Gastrin and pepsinogen changes during an Ostertagia ostertagi challenge infection in calves

Daily changes in serum gastrin and pepsinogen concentration have been studied during two types of infection with Ostertagia ostertagi in calves. In a first experiment two calves were trickle infected (10 times 10,000 L3 Ostertagia) and two animals received a single infection of 100,000 L3 Ostertagia. Gastrin and pepsinogen changes are discussed in relation to adult wormburdens. The second experiment involved 8 calves and was designed to investigate pepsinogen and gastrin changes following a challenge infection in previously sensitized calves. The high dosed group was infected with 5,000 L3 O. ostertagi during 30 days, the low dosed group received 500 L3 O. ostertagi and group 3 served as uninfected control. At day 41 post infection all animals were treated with oxfendazole and on day 61 challenged with 100,000 L3 O. ostertagi. Only in the high dosed group a distinct pepsinogen and gastrin reaction was noticed. Both parameters dropped to almost preinfection levels after treatment. Two days post challenge a moderate rise (+/- 1,000 mU tyr) of the pepsinogen concentration was observed in the previously infected animals and gastrin showed a temporary slight increase in several animals 8 to 10 days post challenge. The effect of treatment and challenge infection is discussed in relation to gastrin and pepsinogen changes and immunity.     

Response to transplanted adult Ostertagia ostertagi in calves

Plasma pepsinogen levels became elevated in groups of recipient calves immediately after transplant with adult Ostertagia ostertagi. These rises occurred in both previously parasite-naive calves and in calves which had experienced prior infection terminated with an anthelmintic either seven or 21 days before transplant. From the results it appears that adult O ostertagi play a significant role in the elevated plasma pepsinogen levels associated with bovine ostertagiasis.     

Pathogenesis of simulated natural infections with Ostertagia ostertagi in calves

The possibility of a mucosal hypersensitivity reaction and its relationship to the pathogenesis of simulated natural infections with Ostertagia ostertagi were studied in calves. Four groups of 4 calves each were used. One group was used as noninfected control; a 2nd group was given increasing doses of infective larvae; a 3rd group was given increasing doses of larvae and these were removed by succeeding treatment with an anthelmintic; and a 4th group was given an initial dose of larvae which was then eliminated with an anthelmintic. All calves given larvae became sensitized, as shown by an intradermal skin test. The continuously infected calves had significantly (P less than 0.05) higher fecal egg counts, eosinophil counts, plasma pepsinogen values, and worm burdens and significantly (P less than 0.05) lower lymphocyte counts than did the other groups of calves. These animals also had the most extensive mucosal pathologic changes. The group given intermittent larval challenge exposures followed by an anthelmintic showed decreased lymphocyte values, but these were not significant. Plasma pepsinogen values of this group increased between every challenge exposure and treatment, a 3-day period. This indicated that a mucosal hypersensitivity reaction had occurred in these calves at these times, because they were shown to have been sensitized, and challenge-exposure infections were not present for sufficient time to have produced direct pathologic effects. It therefore seems that a part of the pathologic changes in O ostertagi infections may be the result of the continuous challenge exposure experienced by the animals through a constant intake of larvae from pasture and the intestinal reaction to this challenge exposure.     

Effects of Ostertagia ostertagi infection on secretion of metabolic hormones in calves.

Effects of Ostertagia ostertagi infection on secretion of insulin, pancreatic glucagon, cortisol, gastrin, and pepsinogen were studied in calves inoculated with 100,000 (group 1) or 10,000 (group 2) O ostertagi infective larvae weekly for 14 weeks. Plasma insulin concentrations in both inoculated groups were lower than those in a non-infected (group 3) control group. The differences between group 1 and group 3 were significant (P < 0.05) at 2 and 12 weeks after initial inoculation. Plasma pancreatic glucagon and cortisol concentrations of groups 1 and 2 did not differ significantly from those of the control group, although plasma pancreatic glucagon concentration was consistently lower in group-1 calves from 4 weeks to end of the study. Plasma pepsinogen and serum gastrin concentrations also increased significantly (P < 0.05) in both groups that received inoculations. We concluded that decreased plasma insulin concentrations are contributory to changes in postabsorptive protein metabolism, and that serum gastrin concentrations are more representative of the pathologic changes in the abomasum than are plasma pepsinogen concentrations.     

Lymphocyte blastogenic responses of calves experimentally infected with Ostertagia ostertagi

Twelve 9-week-old calves were divided into four groups; two groups were maintained helminth-free as controls and the other groups were given Ostertagia ostertagi infective-stage larvae (L3) orally. One group received 100,000 L3 as a single inoculum and the other group received L3 in increasing dosages at weekly intervals for 8 consecutive weeks. The blastogenic responses to concanavalin A (Con A), phytohemagglutinin (PHA), and a soluble larval antigen from O. ostertagi (SLA) of peripheral blood lymphocytes were evaluated using tritiated thymidine incorporation into DNA as a measure of blastogenesis. The responses to Con A of all infected calves were significantly depressed while the responses to PHA were not. SLA, at concentrations of 4 micrograms ml-1 and above, caused blastogenic activity in lymphocytes from uninfected calves. Using SLA at 1 microgram ml-1 in lymphocyte cultures supplemented with autologous serum, an antigen-induced blastogenic response was detected in calves receiving serial inoculations of L3.     

Grazing pressure and acquisition of Ostertagia ostertagi in calves

The effect of stocking rate on the acquisition of Ostertagia ostertagi infection and performance of yearling calves grazing a marshland area in the southwest of Jutland (Denmark) was examined. During the early part of the grazing season, when grass growth was high and pasture infectivity low, there was little stocking rate effect on performance. However, during the late part of the grazing season (characterized by poorer grass growth and high pasture infectivity) gains were significantly lower at high, compared with moderate stocking. At both stocking rates, the beneficial effect of moving animals to aftermath in mid-summer was significant, but was most pronounced at the high stocking rate. Interactions between stocking rate and acquisition of parasitism are discussed in the light of grazing behaviour and climatic factors.     

Dermal responses to Ostertagia ostertagi in Ostertagia ostertagi- and Cooperia punctata-inoculated calves

Calves harboring patent Ostertagia ostertagi or Cooperia punctata were given intradermal injections of O ostertagi 3rd-stage larval antigen. The initial injections were followed 30 days later by a 2nd series of injections. Skin thickness was measured at injection sites for 72 hours after injection. Selected injection sites including saline solution control sites were biopsied at 30 minutes, at 3, 24, 48, and 72 hours, and at 30 days after injection. After the 1st series of injections, there was a clear distinction in dermal reactions between O ostertagi-inoculated calves and C punctata-inoculated calves; after 24 hours, reactions were not seen in the C punctata-inoculated calves. Marked dermal reactions occurred in the O ostertagi-inoculated calves. The reactions at 30 minutes and 3 hours were characterized by slight-to-extensive infiltration of neutrophils and dermal edema. The 24-hour cellular reaction was principally due to neutrophil and eosinophil infiltration with edema and necrosis. Reactions at 48 to 72 hours were due to eosinophils and perivascular accumulations of macrophages and lymphocytes. Necrosis, neutrophils, and edema were present in foci where fragments of nematodes were located. On reinjection, a clear distinction in dermal reactions between calves was not seen based on the type of nematode infection. Thirty days after dermal inoculation, large nodules developed at the site of the initial antigen injection. The nodules were characterized by marked intradermal proliferation of lymphocytes in a follicular pattern with occasional macrophages and rare multinucleated giant cells.     

Acute phase response in calves following infection with Pasteurella haemolytica, Ostertagia ostertagi and endotoxin administration

The concentrations of bovine acute phase proteins were monitored in plasma following experimental infection with Pasteurella haemolytica and Ostertagia ostertagi and after endotoxin administration. Raised levels of haptoglobin, alpha 1 proteinase inhibitor and seromucoid were detected after pasteurella infection and endotoxin administration. Ceruloplasmin levels increased after endotoxin administration but not during pasteurella infection. Raised levels of the four acute phase proteins were found in eight of 19 calves infected with ostertagia but showed a variable pattern and did not correlate with plasma pepsinogen increases. Bovine alpha 1 antichymotrypsin and alpha 2 macroglobulin were identified as acute phase reactants.     

Ostertagia ostertagi challenge of calves vaccinated with Haemonchus placei intestinal homogenate

The protective capacity of vaccination with Haemonchus placei whole gut homogenate against challenge with the non-blood-feeding nematode Ostertagia ostertagi was evaluated in calves. Ten helminth-free calves were randomly assigned to two groups. Group 1 received 100microg H. placei intestinal homogenate in the adjuvant 5% dextran sulfate/PBS, while Group 2 received the adjuvant alone. Injections were administered subcutaneously on Days 0 and 28. All calves were challenged with approximately 26,100 O. ostertagi larvae on Day 42. Serum antibody response and counts of nematode eggs per gram of feces (EPG) were determined throughout the study. Calves were necropsied at 5.5 weeks post-challenge for recovery of nematodes. Although significant increases were detected in both serum IgG(1) and IgG(2) of Group 1 calves (p<0.05), there was no significant difference in the total number of O. ostertagi recovered from the two groups (p>0.05). Lengths of adult nematodes were not significantly different between groups nor were the numbers of eggs present in adult females recovered from each group significantly different (p>0.05). There were also no significant differences between groups regarding fecal egg counts (p>0.05). Results suggest either: (1) the antigens targeted by the induced antibodies were not present in O. ostertagi; (2) the antigens targeted by the induced antibodies were present, but not essential to O. ostertagi survival; or (3) the antigen was present and essential, but amount of antibody ingested was insufficient to cause damage to the nematode.     

Age resistance in calves to Ostertagia ostertagi and Cooperia oncophora

Calves were infected repeatedly during a period of 6 weeks with Ostertagia ostertagi and Cooperia oncophora, at an age of 3, 6 or 9 months. The inoculations were performed during three periods, February-March, May-June and August-September, to account for possible seasonal effects or effects of larval batches. Observations were done on faecal egg output, antibody titres and weight gains. Calves were slaughtered for post mortem examinations 9 weeks after the start of infections. The influence of age on worm populations and egg output was significant for C. oncophora but not for O. ostertagi. The effect of season or larval batch on worm populations was significant for O. ostertagi but not for C. oncophora. The correlations between worm numbers and several other parameters found for Cooperia were strongly indicative of a process of worm expulsion taking place at the stage of infection (9 weeks after the start of infections) when post mortem examinations were done. Such correlations were absent for Ostertagia. It is concluded that within the range of ages examined here (the range to which first season grazing calves belong), there is no influence of age on Ostertagia populations but a clear effect of age on Cooperia. This difference strongly influences the total faecal egg output of grazing calves and its interpretation.     

Pathophysiological and parasitological studies on Ostertagia ostertagi infections in calves

Friesian calves given a low level infection of the abomasal parasite Ostertagia ostertagi over a six week period displayed a mild diarrhoea with high faecal egg counts and elevated plasma pepsinogen values. At necropsy on day 23 abomasal lesions characteristic of ostertagiasis were widespread. At 42 and 84 days oedema and congestion were also prominent. Total worm burdens on days 23 and 42 were similar but a marked decrease had occurred by day 84. Feed digestibility and nitrogen economy were not markedly affected but radioisotopic measurements demonstrated an increase in albumin disappearance and catabolic rates, and plasma faecal clearance during the course of the infection. Prior administration of a morantel sustained release bolus to a group of similarly infected calves reduced the total worm burdens to less than 50 per cent of those recorded in the infected calves on days 23 and 42 and this fell to 3 per cent on day 84. Abomasal damage and the adverse pathophysiological changes associated with infection were prevented in this group.     

Negative interactions between Ostertagia ostertagi and Cooperia oncophora in calves

The interactions between Ostertagia ostertagi and Cooperia oncophora were studied in calves by concurrent and sequential infections. A reciprocal negative interaction between the 2 species was found in sequential, but not in concurrent infections. This result was supported by the finding of serological cross-reactions. It is suggested that the negative interaction is immunologically mediated. The depression of weight gain found after infection was similar for O. ostertagi- and C. oncophora-infected calves.     

Pathophysiologic effects of Ostertagia ostertagi in calves and their prevention by strategic anthelmintic treatments.

Pathophysiologic effects of Ostertagia ostertagi infection and their prevention by strategic anthelmintic treatments were studied in 3 groups each of 6 steer calves. Group-1 calves were noninfected controls. Group-2 calves were inoculated with 100,000 third-stage larvae on the 1st and 28th days of the experiment and grazed on pasture initially free of contamination. Group-3 calves were on a similar regimen as those in group 2, but were also treated with ivermectin 9 days after each larval inoculation. Group-2 calves had increased plasma pepsinogen and gastrin values and decreased weight gains, and total serum protein and albumin concentrations from the 2nd week of infection onward. They were anemic at 10 to 12 weeks and had lower carcass and meat quality at slaughter. Strategic anthelmintic treatments were effective in preventing these effects and calves in groups 1 and 3 had similar performances. On the basis of our findings, high pepsinogen values were related to worm burdens, whereas high gastrin concentrations were related to gastric lesions.     

Adverse immune reactions and the pathogenesis of Ostertagia ostertagi infections in calves

The possible development of type-1 hypersensitivity reactions in the abomasal mucosa caused by soluble L3 products of Ostertagia ostertagi was studied in 4-month-old calves sensitized by repeated exposure to L3 over a 50-day period followed by anthelmintic treatment. Four groups each of 4 calves were used. Group 1 served as nonsensitized controls and group 2 as sensitized controls, group 3 was challenge exposed at 2-week intervals beginning at week 10 with a soluble L3 product (OAG), and group 4 was challenge exposed at 2-week intervals with an oral dose of L3, followed by anthelmintic treatment 3 days later. All calves infected with L3 became sensitized, as indicated by a positive reaction to an intradermal skin test. However, a passive cutaneous anaphylaxis was only partly effective in indicating the presence of homocytotropic antibody in the infected calves. Sensitized calves had significantly (P less than 0.05) higher eosinophil counts and plasma pepsinogen values for the entire 14 weeks than uninfected controls. Globule leukocyte and mast cell counts from the abomasal mucosa were also significantly (P less than 0.05) higher. Studies for possible immunomodulation revealed that lymphocyte counts decreased between every 2-week challenge-exposure period for groups-3 and -4 calves. A transient depression of blood lymphocyte (BL) responses to phytohemagglutinin (PHA), a T-cell mitogen, was observed over the first 8 weeks in the infected calves. Increases in BL responses to OAG were also observed. Differences were not observed in BL responses to pokeweed mitogen, a T- and B-cell mitogen. Blood lymphocyte responses to PHA in group-3 calves were low following the initial challenge exposure with OAG.(ABSTRACT TRUNCATED AT 250 WORDS)     

Further studies on the response to transplanted adult Ostertagia ostertagi in calves

Calves infected by surgical transplantation of adult Ostertagia ostertagi had raised levels of plasma pepsinogen and those in which the largest number of worms established also had elevated plasma gastrin concentrations. Despite the elevated plasma pepsinogen values, the abomasal pH of the animals did not change significantly, and there was no significant difference in the percentage establishment of adult parasites in calves previously infected with O ostertagi third stage larvae and those which had been maintained parasite-naive before transplant.