Blood gastrin and pepsinogen responses to subclinical infection with Ostertagia ostertagi in adult dairy cattle

Blood gastrin and pepsinogen responses to a single infection with 100,000 Ostertagia ostertagi infective larvae in lactating dairy cows were investigated. None of the infected cows showed signs of clinical ostertagiasis, nor was there any difference in live weight gain, milk yield or faecal egg count between groups. Pepsinogen levels of the infected group were significantly elevated between days 3 and 24 after infection (peak 1041 mU tyrosine; day 14). In contrast, there was no significant difference in blood gastrin levels between infected and control animals suggesting that few adult worms had become established in the former group. These data are compared with the increases in both gastrin and pepsinogen levels recorded in susceptible calves exposed to the same level, pattern and strain of ostertagia infection in a previous experiment. It is suggested that gastrin assay may be of value in adult cattle for indicating when elevated pepsinogen levels are merely associated with a rise in larval intake and not with the establishment of large adult worm burdens.     

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.     

Interactions between lungworms and gastrointestinal worms in calves

Interactions between gastrointestinal worms (Ostertagia ostertagi, Cooperia oncophora) and lungworms (Dictyocaulus viviparus) in calves were studied by assessing the effect of primary infections with either group of worms on the development of homologous or heterologous challenge infections. Primary infections with lungworms resulted in some degree of resistance to challenge with gastrointestinal worms, but this resistance was lower than that found after homologous infection. Primary infections with gastrointestinal worms did not confer any resistance to challenge with lungworms. On the contrary, an indication was found of some enhancing effect of previous gastrointestinal worm infection on the establishment of lungworms. The highest degree of resistance against lungworm challenge was found where calves have been primarily infected with lungworms. Lungworm infections produced some elevation of serum pepsinogen levels. Gastrointestinal worms evoked a rise in circulating eosinophils, although this rise was smaller and occurred later than in lungworm-infected calves. Under the conditions of the experiment, the effect of 6000 infective lungworm larvae on weight gain was larger than the effect of 100,000 L3 of Ostertagia ostertagi and 100,000 L3 of Cooperia oncophora.     

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.     

Efficacy of the morantel sustained release trilaminate bolus against gastrointestinal nematodes and its influence on immunity in calves.

An experiment was conducted in calves to investigate the efficacy of a morantel sustained release trilaminate bolus (MSRT) to control gastrointestinal parasitism and to assess the development of immunity during the use of MSRT. Two groups (M and U) of four calves each were infected three times a week with a mixed Ostertagia ostertagi and Cooperia oncophora infection for 12 weeks. Calves of Group M received an MSRT at the start of the experiment. Twenty weeks after the start of the experiment, all animals, including a previously uninfected control group (C), received a challenge with 100,000 Ostertagia and 100,000 Cooperia. After a further 4 weeks all calves were necropsied for worm counts. During the trial calves were weighed and faecal egg counts, larval differentiation and pepsinogen concentrations were determined. The results demonstrated the high level of efficacy of the MSRT in reducing the faecal egg output and preventing parasitic gastroenteritis under conditions of a continuous high rate of infection. Efficacy of treatment was higher for Cooperia than for Ostertagia. Post-mortem worm counts suggested a partially impaired immunity build-up in Group M, at least for Cooperia.     

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.     

Diagnostic value of gastrin for clinical bovine ostertagiosis.

Gastrin values were evaluated in 130 parasite naive calves, in 61 first season grazing calves during six field trials and in 8 experimentally infected adult immune cows. The gastrin values were linked to pepsinogen levels and daily weight gain. Also the influence of an anthelmintic treatment on pepsinogen and gastrin values was assessed during a clinical outbreak of ostertagiosis in a group of first season grazing calves. Mean gastrin levels in parasite naive calves were 106 pg/ml. Results show that a group mean of 400 pg/ml gastrin in first season grazing calves indicates a reduced daily weight gain but with no obvious clinical signs. During clinical outbreaks mean gastrin levels frequently reached 1,000 pg/ml with a severe weight loss and a mean pepsinogen level of 5,000 mU tyr. The serum gastrin concentration was strongly reduced 4 days post treatment. No gastrin response was noted following an Ostertagia challenge in adult immune cows. The value of gastrin as a diagnostic aid for ostertagiosis is discussed in relation to pepsinogen, the adult worm burden, larval inhibition and the technique involved in assessing gastrin.     

Studies of the immunomodulatory effects of low-level infection with Ostertagia ostertagi in calves

Possible immunomodulation by low-level infection with Ostertagia ostertagi was studied in 4-month-old calves. Six groups of 4 calves each were subjected to the following regimens: group 1--nonparasitized controls; group 2--nonparasitized, but challenge exposed at day 64 with Brucella abortus strain 19 vaccine (BA) and at day 78 with IV administration of a soluble third-stage larval (L3) antigen preparation of O ostertagi (OAG); group 3--nonparasitized, but challenge exposed at day 78 with 75 x 10(3) L3 of O ostertagi; group 4--continuously parasitized by weekly dosing with 30 x 10(3) L3 of O ostertagi; group 5--continuously parasitized by weekly dosing with 30 x 10(3) L3 of O ostertagi, then challenge exposed on day 64 with BA and on day 78 with IV inoculation of OAG; and group 6--continuously parasitized by weekly dosing with 30 x 10(3) L3 of O ostertagi, then challenge exposed on day 78 with 75 x 10(3) L3 of O ostertagi. Over the initial 10 weeks of the study, nonparasitized calves, (groups 1, 2, and 3) had higher body weight, blood lymphocyte (BL) response to phytohemagglutinin (PHA), and significantly (P less than 0.05) higher feed consumption and lymphocyte numbers, whereas parasitized calves (groups 4, 5, and 6) had higher BL responses to pokeweed mitogen (PWM) and significantly (P less than 0.05) higher neutrophil and eosinophil numbers, plasma pepsinogen (PP) values, and BL response to OAG.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

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.     

Effects of Ostertagia ostertagi and omeprazole treatment on feed intake and gastrin-related responses in the calf

Infection with the bovine abomasal nematode, Ostertagia ostertagi, results in a loss of acid-secreting parietal cells and an increase in gastric pH. The effects of an experimental infection with Ostertagia and/or daily treatment with omeprazole (OMP) at 2mgkg(-1) bodyweight for four consecutive days (experiment days 24-27, inclusive) on voluntary feed intake, blood and tissue gastrin concentrations, abomasal G-cell numbers, gastric pH, and blood cholecystokinin (CCK) and pepsinogen concentrations were investigated in the calf. Ostertagia-infected calves demonstrated a significant drop in feed intake between days 24 and 27 post-infection (38%; P<0.001) and in G-cell numbers (42%; P<0.05) and significant increases in abomasal pH (P<0.001), fundic mucosal weight (99%; P<0.01), and blood gastrin (P<0.05) and pepsinogen (P<0.0001). OMP treatment of worm-free animals resulted in a significant drop in intake between days 24 and 27 (30%; P<0.001) and in G-cell numbers (17%; P<0.05) and significant increases in abomasal pH (P<0.01) and blood gastrin (P<0.001). OMP treatment of Ostertagia-infected animals with an existing hypergastrinaemia had no effect on feed intake, abomasal pH, blood gastrin or pepsinogen or abomasal G-cell numbers. Blood CCK concentrations were also unaffected by either Ostertagia infection or OMP treatment. These data suggest that: (a) the depression in feed intake associated with OMP in worm-free calves was not due to a side effect of drug treatment; (b) inappetance in Ostertagia-infected animals is closely associated with the parasite-induced hypergastrinaemia; and (c) the elevation in abomasal pH was a major factor responsible for the elevated blood gastrin concentrations seen in parasitised and OMP-treated animals.     

High concentration of serum gastrin immunoreactivity and abomasal mucosal hyperplasia in calves infected with Ostertagia ostertagi and/or Trichostrongylus axei

Parasite-free, 4-month-old-calves were inoculated with Ostertagia ostertagi and/or Trichostrongylus axei, followed 6 weeks later by inoculation with increasing doses of O ostertagi for 8 weeks in the 2 groups (n = 4) of calves that had been given O ostertagi. Gastrin immunoreactivity concentration in serum was measured before and after infection and was correlated with changes in mucosal thickness. Gastrin immunoreactivity concentration in preinoculation control sera ranged from 95.2 to 287.1 pg/ml, and increased values were measured in all parasitized calves after 15 weeks. Significantly (P less than 0.05) increased serum gastrin immunoreactivity concentration compared with the preinfection value, was found in calves infected with O ostertagi or T axei, and highly significant (P less than 0.01) values were observed in calves infected with both parasites. Abomasal mucosal hyperplasia was observed in all parasitized calves; increased mucosal thickness and mucosal cross-sectional area were most prominent in calves infected with O ostertagi and T axei.     

Larval migration inhibition activity in abomasal mucus and serum from calves infected with Ostertagia ostertagi

The present study investigated whether abomasal mucus from calves naturally infected with gastrointestinal nematodes possessed larval migration inhibition (LMI) activity in vitro, and whether LMI activity was greater in mucus from previously immunised animals, compared to primary infected and uninfected calves. LMI activity was also assessed in serum from calves during both natural and artificial Ostertagia ostertagi infections, in an attempt to monitor the development of acquired immunity. Both abomasal mucus and serum exhibited larval paralysing activity. Although the LMI capacity of the abomasal mucus was very variable, the highest paralysing activity was consistently observed in mucus from previously immunised calves. LMI activity in serum increased significantly during both artificial and natural Ostertagia infections. After a challenge infection, sera from immunised animals showed a significantly higher LMI capacity, compared to previously uninfected calves. Moreover, serum LMI activity was significantly negatively correlated with Ostertagia worm counts after the challenge infection. The present results suggest that LMI activity in serum and/or abomasal mucus reflects a protective immune response against O. ostertagi in the abomasal mucosa.     

Forms of bovine pepsinogen in plasma from cattle with three different 'syndromes' of Ostertagia ostertagi infection

Calves infected orally with third stage larvae of Ostertagia ostertagi or infected with adult O ostertagi by direct transplantation into the abomasum had raised plasma pepsinogen activity, as did four-year-old dairy cattle challenged with O ostertagi third stage larvae on five occasions. Using fast protein liquid chromatography two forms of pepsinogen; pepsinogen 1 (PG1) and pepsinogen 2 (PG2) were identified in each of the parasitic infection regimes.     

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.     

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.     

Evaluation of the persistent efficacy of doramectin and ivermectin injectable against Ostertagia ostertagi and Cooperia oncophora in cattle

The persistent efficacy of doramectin and ivermectin injectable against moderate and high infection levels of Ostertagia ostertagi and Cooperia oncophora were evaluated in cattle. Calves were allocated to six groups of six animals. On Day 0 animals of Groups I1/I2 and D1/D2 were treated with 0.2mg/kg ivermectin and doramectin injectable, respectively. Animals of the C1, I1 and D1 groups received a daily (moderate) infection of 1000 L3 of O. ostertagi and 1000 L3 of C. oncophora, and animals of the C2, I2 and D2 groups received a daily (high) infection of 10,000 L3 of each species. The animals were infected for 21 days with both species, the infections with C. oncophora and O. ostertagi started from Days 8 and 15 post treatment, respectively. Animals were necropsied on Day 40. The calculation of the persistent activity of ivermectin and doramectin was based on the efficacy against the different developmental and adult stages of both parasites. The present study confirmed that infection levels may influence the duration of persistent efficacy of an anthelmintic. Doramectin had at the moderate infection level a persistent efficacy of at least 35 days against O. ostertagi and at least 28 days against C. oncophora; at the high infection dose persistent efficacy was somewhat shorter i.e. up to 33 days and approximately 28 days, respectively. The duration of persistent efficacy of ivermectin against O. ostertagi at the moderate infection level was between 14 and 25 days, at the high dose level up to 25 days. Persistent efficacy of ivermectin against C. oncophora could, at both infection doses, not be measured, with the present experimental design.     

Dermal cellular responses of helminth-free and Ostertagia ostertagi-infected calves to intradermal injections of soluble extracts from O. ostertagi L3 larvae

Twelve calves were raised helminth-free until 9 weeks of age when six were orally inoculated with 100,000 Ostertagia ostertagi infective stage larvae (L3). Three uninfected and three experimentally infected calves received intradermal injections of sterile saline and soluble larval extract (SLE) from O. ostertagi L3 with a protein concentration ranging from 1 to 200 micrograms ml-1. Biopsies were performed 48 h post-injection. A kinetic study was performed on the remaining six calves, three infected and three uninfected, using a 100 micrograms ml-1 concentration of SLE and taking biopsies 1, 4, 8, 12, 24, and 72 h post-injection at both the saline and SLE-injected sites. All calves had an immediate wheal and increase in skin thickness at the SLE-injected sites. The numbers of eosinophils infiltrating SLE-injected sites as compared to saline-injected sites were significant in both uninfected and infected calves, but the infected calves had significant numbers to a wider range of SLE concentrations and had significantly higher numbers than uninfected calves in the kinetic study. Infected calves also had significant numbers of basophils in the dose response study at concentrations of 5 and 100 micrograms ml-1 SLE. Neutrophil infiltration was similar in both groups and was significant at SLE-injected sites early in the kinetic study. Detectable mast cells were decreased in SLE-injected sites of infected animals and perivascular accumulation of mononuclear and some polymorphonuclear cells was observed in the deep dermis of infected animals.     

Nutritional and pathophysiologic effects of clinically apparent and subclinical infections of Ostertagia ostertagi in calves.

Nutritional and physiologic effects of clinically apparent and subclinical Ostertagia ostertagi infections were studied in 3 groups of 5 calves each. Group-1 calves were inoculated with 100,000 Ostertagia ostertagi third-stage larvae (L3)/calf/wk for 14 weeks. Group-2 calves were inoculated with 10,000 L3/calf/wk for 14 weeks, and group-3 calves were no inoculated. Calves in group 1 had decreased dry matter intake and feed utilization from 4 weeks after initial inoculation. Group-2 calves had no changes in dry matter intake, but had decreased feed utilization at 12 and 14 weeks. Calves with clinically apparent infections (group 1) lost a mean weight of 11.8 kg, whereas calves with suclinical infections (group 2) lost a mean of 46.6 kg, and control calves lost a mean of 60.7 kg. Calves with O ostertagi infections (group 1 and 2) also had decreased carcass quality at slaughtering, which was reflected in decreased dressing weights and increased water-holding capacity of the rib-eye muscle. Calves in groups 1 and 2 also had lower carcass yield and rib-eye muscle weight, and group-1 calves had decreased protein content. Results of hematologic, pathologic, parasitologic, and clinical examinations mirrored nutritional changes.