Explaining variability in first grazing season heifer growth combining individually measured parasitological and clinical indicators with exposure to gastrointestinal nematode infection based on grazing management practice.

The objective of our study was to explain the variability of average daily weight gain (ADWG) due to gastrointestinal nematode (GIN) infection for 291 non treated first grazing season (FGS) heifers, from 12 independent groups in the western part of France, by combining parasitological and clinical indicators at individual level and grazing management indicators at group level. Parasitological indicators were faecal egg count (FEC), anti Ostertagia ostertagi antibody level (Ostertagia ODR), and pepsinogen level. Clinical indicators were diarrhea score (DISCO) and breech soiling score (BSS). At group level, grazing management practice (GMP), based on three variables (supplementation, month of turnout, grazing season duration), was clustered into three categories reflecting low, medium or high exposure (EXP) to GIN. Depending on the groups, turnout was from mid-March to early July and housing was from mid-October to late November, with a FGS duration ranging from 4 to 8.4 months. At turnout, the mean age of heifers was 8 months (range: 6-16 months) and they weighed between 175 and 268kg. In each GMP category, FEC significantly decreased between the mid-season and the housing, while Ostertagia ODR and pepsinogen level increased gradually throughout the grazing season. In contrast, clinical indicators did not show any seasonal variation. In a multivariate linear model, 22% of the ADWG variability was significantly explained by two individual indicators (Ostertagia ODR: 12.6%, DISCO: 4.8%) and by the group indicator (GMP category: 4.8%). ADWG losses due to GIN exposure (Ostertagia ODR) were estimated up to 39kg per heifer for the overall grazing season. For groups within the low EXP category the difference between animals with low (<697g/day) or high (>697g/day) ADWG was explained by the clinical indicator DISCO. In contrast, for groups within the medium and high EXP categories this difference was explained by a parasitological indicator (Ostertagia ODR). This study highlighted the value of combining both grazing management (group level) and parasitological (individual level) indicators to assess the impact of GIN on ADWG of FGS heifers. As a result, this combination might allow a better discrimination of animals or groups that may be in need of treatment in a targeting selective treatment approach.

Anti-parasitic activity of pelleted sainfoin (Onobrychis viciifolia) against Ostertagia ostertagi and Cooperia oncophora in calves.

BACKGROUND: Increasing anthelmintic-resistance in nematodes of ruminants emphasises the need for sustainable parasite control. Condensed tannin-containing legume forages such as sainfoin (Onobrychis viciifolia) have shown promising anthelmintic properties in small ruminants but this has never been explored in cattle. Therefore, our aim was to examine the efficacy of sainfoin against cattle nematodes in vivo. METHODS: Fifteen Jersey male calves (2-4 month-old) were allocated into two groups and fed isoproteic and isoenergetic diets mainly composed of sainfoin pellets (Group SF; n = 9, three pens) or concentrate and grass-clover hay (Group CO; n = 6, two pens). After 16 days of adaptation, all animals were experimentally infected with 10,000 and 66,000 third-stage larvae of Ostertagia ostertagi and Cooperia oncophora, respectively. Egg excretion, blood parameters and bodyweights were recorded throughout the study. Worms were harvested by sieving for quantification and scanning electron microscopy (SEM) 42 days post-infection (dpi) when the calves were necropsied. RESULTS: The number of O. ostertagi adults in the abomasum was reduced by 50 % in Group SF compared with Group CO (P < 0.05). This was further reflected in higher albumin (P < 0.1) and lower pepsinogen levels (P < 0.05) in Group SF at 21 dpi, and structural damage of the worm cuticle could be visualised by SEM. Yet, the nematode egg excretion in Group SF was not significantly different from that of the controls (P > 0.05). Likewise, no statistical difference in total worm burdens of C. oncophora was found between the groups. Weight gains were lower for Group SF (P < 0.05), which may reflect lower digestibility and phosphorus levels in the SF diet, despite similar feed intake at pen-level. CONCLUSIONS: Overall, the effect of sainfoin on abomasal nematodes corroborates results from studies with small ruminants and encourages further investigations of the use of this crop for control of cattle nematodes.

Exposure to pasture borne nematodes affects individual milk yield in Swedish dairy herds.

The association between exposure to gastrointestinal nematode (GIN) parasitism, indicated by elevated individual optical density ratio (ODR) to Ostertagia ostertagi, and individual milk production was analysed in dairy cows. The multivariable analysis also accounted for other sources of variation than exposure to GIN parasitism. Intra- and inter-herd variation in parasite exposure was also evaluated. Organic and conventional herds located in south-east Sweden (13 herds per system) were visited during the housing period 2009-2010. Levels of all major pasture-borne helminths in Sweden (O. ostertagi, Fasciola hepatica and Dictyocaulus viviparus) were determined in bulk tank milk, cow milk and serum (only for O. ostertagi). Their specific antibodies were detected using three different ELISAs (Svanova Biotech) and the optical density of the sample was expressed as ODR. Positive cases of Dictyocaulus and Fasciola were seldom found. Variation in ODR in serum samples for Ostertagia was higher within herds than between herds. Correlations between ODR for Ostertagia in serum and milk parameters were significant and negative. In the multivariable analysis, two models were performed separating data from primiparous and multiparous cows. Results from mixed models showed that daily milk yield was significantly influenced by Ostertagia ODR for multiparous cows. No interactions were found between Ostertagia ODR values and herd type.

Protective immunization of calves against Ostertagia ostertagi using fourth stage larval extracts.

ConA lectin was used to isolate glycoproteins from detergent extracts of fourth stage Ostertagia ostertagi larvae. This preparation contained proteins additional to those observed in a similar fraction prepared from adult O. ostertagi. Two vaccine trials were conducted with this preparation, and sub-fractions thereof, in groups of 6-8 worm-free calves. All groups were challenged with 50,000 O. ostertagi larvae 1 week after the final immunization, and protection was assessed by comparing the egg and worm counts of the immunized groups with their respective controls. Immunization with the ConA-binding antigen or its sub-fractions induced high titre serum antibody responses. In the first trial, the cumulative egg count of the group immunized with unfractionated antigen was 60% lower than the corresponding control value, and worm counts were 47% lower. In the second trial, the cumulative egg counts of the vaccinated groups ranged from 70% to 85% lower than the corresponding controls, with worm counts up to 64% lower. It was concluded that detergent-soluble, ConA-binding extracts prepared from O. ostertagi fourth stage larvae contained protective immunogens that were as effective as the best antigens published for O. ostertagi to date.

Measurement of antibodies to gastrointestinal nematodes and liver fluke in meat juice of beef cattle and associations with carcass parameters.

In an effort to develop non-invasive methods for the diagnosis of Ostertagia ostertagi and Fasciola hepatica infection in beef cattle, this study was undertaken to evaluate antibody-detection ELISAs in meat juice samples and to investigate the associations between test results and carcass parameters. Preliminary tests were carried out to determine optimal working dilutions of meat juice samples. The Pearson correlation coefficients between ELISA results (expressed as ODR) of serum and meat juice samples from 90 to 100 cows were R=0.82 and 0.75 for O. ostertagi and F. hepatica, respectively. Next, an abattoir survey in Belgian Blue suckler cows was performed, analysing meat juice samples from 726 animals in spring and 724 animals in autumn 2008, originating from a total of 480 herds. There was a large variation in the observed O. ostertagi and F. hepatica ODRs and inter-seasonal differences were observed for F. hepatica (spring>autumn), but not for O. ostertagi. The relationships between individual parasite-specific ELISA results and carcass parameters (warm carcass weight, conformation score, fat coverage) were investigated by linear or logistic mixed models with herd as a random effect, while the relationship between herd average ELISA results and herd averaged carcass weight was investigated by linear regression with mean cow age and season as covariates. An increase in individual O. ostertagi ODR over the interquartile range was associated with an increased likelihood by 1.3 of a low conformation score (score E vs. S), but no significant associations were found with other carcass parameters. However, herd mean ELISA results were negatively associated with a decrease in the herd average carcass weight (P=0.001 and P=0.09 for O. ostertagi and F. hepatica, respectively). An increase in the herd mean O. ostertagi or F. hepatica ODR over the interquartile range was associated with a decrease in herd mean carcass weight of 9.1 and 3.4 kg, respectively. The implications of these results and the value of monitoring parasitic infections by analysis of meat juice samples from the abattoir are discussed.

Associations between blood gastrin, ghrelin, leptin, pepsinogen and Ostertagia ostertagi antibody concentrations and voluntary feed intake in calves exposed to a trickle infection with O. ostertagi.

Twenty-five, castrated male Holstein-cross calves, between 4 and 5 months of age, weighing 156.5+/-12.2 kg and reared under conditions designed to minimise the risk of parasitic infection, were allocated to one of the five treatment groups on the basis of initial bodyweight. The groups were (1) ad libitum (ad lib) fed controls (ALC); (2) ad lib fed infected (INF) and treated with topical eprinomectin on Day 56; (3) controls pair-fed with the INF group (PFC); (4) ad lib fed controls treated with eprinomectin on Days 0 and 56 (E-ALC) and (5) ad lib fed, infected and treated with eprinomectin on Days 0 and 56 (E-INF). Infection comprised a trickle infection with the equivalent of 10,000 larvae of Ostertagia ostertagi per day from Day 0 to Day 56 and the study concluded on Day 77. Parameters measured throughout the study included: liveweight, feed intake, faecal egg counts; plasma pepsinogen, gastrin, ghrelin and leptin; plasma antibodies to adult O. ostertagi. No significant differences in feed intake or liveweight gain were observed between any of the different groups, a finding thought to result from the high quality of feed offered. Significant differences between the INF and control groups however were observed in faecal egg counts, plasma pepsinogen, gastrin and O. ostertagi antibodies, which were all elevated, and leptin, which was reduced. Values of these parameters for the E-INF group were intermediate between the INF and ALC groups. Plasma ghrelin showed no association with either feed intake or parasitism. Further studies are needed to fully elucidate the roles of various biochemical and neuroendocrine mediators for inappetence in ruminants with parasitic gastroenteritis.

A longitudinal survey of anti-Ostertagia ostertagi antibody levels in individual and bulk tank milk in two dairy herds in Normandy.

The Ostertagia-specific antibody levels in milk were monitored in 2 dairy herds to investigate seasonal variations and the relationship between individual and bulk tank milk antibody levels. Bulk tank and individual milk samples from all lactating animals were collected over a 1-year period at weekly and monthly intervals, respectively. The Ostertagia-specific antibody levels were measured with an indirect ELISA and the test results were expressed as optical density ratios (ODR). A clear seasonal pattern that followed the expected intake of infectious larvae was observed in the individual and bulk tank milk antibody levels of both herds. Within each herd, there was a large variation in the individual ODRs. This variation remained large when the distribution of individual ODRs was plotted according to high and low bulk tank milk ODR categories. The results suggest that the effect of seasonal variations on cut-off levels that predict production responses after anthelmintic control, needs to be assessed.

Abomasal contents of parasitised sheep contain an inhibitor of gastrin secretion in vitro.

Serum gastrin concentrations are typically elevated in parasitised sheep; however, in some animals serum gastrin concentrations may fall abruptly despite a very high abomasal pH. Although proliferating abomasal bacteria in culture generate a potent inhibitor of in vitro gastrin secretion, this inhibitor has not been detected in abomasal contents of unparasitised sheep. In sheep parasitised by O. circumcincta, all abomasal fluid samples of pH 5 and above were inhibitory to gastrin release in vitro. Inhibitory activity and abomasal pH were correlated in two separate experiments; the model best fitting the data being sigmoidal in each case, with zero activity at pH 3.6 and 4.6, respectively. There was no clear evidence that the presence of a gastrin inhibitor in the abomasal contents reduced the serum gastrin concentration in parasitised sheep. Serum gastrin was correlated with abomasal pH (log(10) serum gastrin concentrations conformed to log-linear sigmoidal models).

Rapid improvement of immunity to Teladorsagia circumcincta is achieved through a reduction in the demand for protein in lactating ewes.

Protein supplementation can improve the resistance to parasites of periparturient ewes, as indicated by reduced nematode egg excretion and worm burdens. However, the rate at which this improvement can occur is largely unknown. We investigated the rate of improvement by assessing temporal changes in faecal egg counts after we experimentally reduced nutrient demand. Three groups of nine pregnant ewes each were trickle infected with Teladorsagia circumcincta from day(-70) to day(16) (parturition is day0). Two groups of twin-rearing ewes were fed at 0.8 (L22) or 1.2 (H22) times their assumed metabolizable protein requirements, and a third group was fed the same daily food allowances as L22 ewes, but one of their lambs was removed on day10 (L21). Ewes were slaughtered on day21 to assess worm burdens, in vitro larval establishment on abomasal explants, and mucosal inflammatory cells. Faecal egg counts of L22 ewes were higher than H22 ewes throughout lactation. After the removal of one lamb, faecal egg counts of L21 ewes decreased within 5 days to levels similar to H22 ewes. Relative to L22 ewes, L21 and H22 ewes had lower worm burdens, parasite per capita fecundity and in vitro establishment rates of both T. circumcincta and Haemonchus contortus. Mucosal mast cell and eosinophil counts were similar for all ewes, but H22 ewes had higher globule leukocyte counts than L22 and L21 ewes. The data suggest that a reduction in protein demand can rapidly improve periparturient immunity to T. circumcincta. This may be associated with increased parasite expulsion, reduced fecundity and non-parasite specific reduction of in vitro larval establishment.

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.

Osteopenia and reduced serum alkaline phosphatase activity in grazing lambs naturally infected with gastrointestinal nematodes.

The effect of gastrointestinal nematode infections on bone development was investigated in growing sheep on pasture. Forty-five weaned lambs from six groups in a two-factorial design incorporating stocking rate (SR; low, medium and high) and presence or absence of infection on pasture were sampled in the late grazing season. Worm counts were performed at slaughter, and the left metacarpal bones were excised for bone assessment. Faecal egg counts and worm burdens, primarily of Ostertagia circumcincta and Trichostrongylus vitrinus, were considerably higher in the high SR infected group ("I-High") than in comparable animals at low or medium SRs, whereas uninfected groups showed negligible egg excretion. Clinical biochemistry revealed significantly reduced serum concentrations of albumin, calcium and alkaline phosphatase in infected lambs. Nematode infections were associated with significant reductions in bone mineral density (30% at high SR), measured by dual energy X-ray absorptiometry, and in bone size (9%). Histomorphometry indicated thinning of the trabecular structure and reduced bone formation in the infected groups, particularly the I-High group. Bone mineral density, bone tissue volume and structural changes were strongly associated with log-transformed worm counts. The study showed that lambs suffering from moderate to heavy degrees of naturally acquired gastrointestinal nematode infection developed marked osteopenia after weaning, i.eduring the later part of the grazing season.

Development of a protective immunity against Ostertagia leptospicularis in trickle-infected sheep and parallel changes of serum gastrin, pepsinogen and antibody levels.

Nine lambs, approximately 9 months of age were allocated to three groups (A, B, C), with three animals in each. Sheep in Groups A and B were trickle-infected with doses of 1000 third-stage larvae (L3) of Ostertagia leptospicularis (five times per week) over periods of 7.5 and 10.5 weeks, respectively, and were subsequently treated with fenbendazole (7.5 mg/kg). Approximately 3 weeks after anthelmintic treatment, all sheep were challenged with a single dose of 100,000 L3, whereas sheep of Group C received the same dose as a primary infection. Sheep of Groups A and B were almost completely refractory against the challenge infection, as indicated by negative faecal egg counts and adult worm burdens. A relatively high infection level was present in the sheep of Group C. The results indicate that a comparatively short immunization period of 7.5 weeks is sufficient to protect lambs against subsequent larval challenge. During immunization, the pepsinogen-, gastrin- and IgA-responses were similar in the individual sheep. In contrast to parasite-specific IgG1 and IgG2 levels, IgA decreased rapidly after cessation of trickle infection and parallel anthelmintic treatment, and may therefore indicate current exposure to parasite antigen. After challenge, the majority of the immunized sheep exhibited immediate and short-term responses of pepsinogen, gastrin and IgA in the serum. The time course and the level of each of these responses were very similar in the individual sheep, suggesting that the release of pepsinogen, gastrin and IgA into the circulation was influenced by related mechanisms.

Infection of sheep with adult and larval Ostertagia circumcincta: gastrin.

Gastric endocrine cell populations and serum and tissue gastrin have been examined in sheep which were infected either intraruminally by tube with 150,000 Ostertagia circumcincta larvae followed by a trickle infection of 10,000 larvae thrice weekly for 8 weeks or by the transfer of 15,000 adult worms directly into the abomasum and killed 8 days later. Depletion of both antral gastrin and somatostatin was evident in both groups: tissue gastrin concentrations were reduced by 85% in the trickle infection and both G cells (gastrin-containing) and D cells (somatostatin-containing) were pale and fewer after adult worm transfer. The concurrent depletion of antral gastrin and somatostatin supports the contention that the hypergastrinaemia in parasitised sheep is largely secondary to the increase in abomasal pH. Although there was no change in the proportions of G34 and G17 in the tissues, there was an increase in the longer form of gastrin in the circulation of the larval-infected sheep, suggesting that there may be differential secretion of G17 and G34 which may be exaggerated as the rate of secretion increases. Although the fundic mucosa was thicker following trickle infection, there was no evidence of enterochromaffin-like cell hyperplasia in either infected group. It is suggested that hyper-gastrinaemia may be beneficial to the host, as it may allow the abomasum to regain the ability to acidify its contents during continued exposure to the parasites.

Infection of sheep with adult and larval Ostertagia circumcincta: effects on abomasal pH and serum gastrin and pepsinogen.

Infection of sheep with adult or larval O. circumcincta increased serum pepsinogen and gastrin and abomasal pH. The upper limits of the normal range, calculated from over 1000 samples collected from parasite-naive sheep, were set at 2 standard deviations above the mean; these were for serum pepsinogen, 454 mU tyrosine l-1; serum gastrin, 64 pM and abomasal pH, 3.26. Five infection regimes were used: sheep previously exposed to field parasitism were infected with 30,000 larvae intraruminally (Group A), while parasite-naive sheep were administered either 50,000 larvae intraruminally (Group B), 150,000 larvae intraruminally followed by a trickle infection of 10,000 larvae thrice weekly from days 21 to 45 (Group C), 150,000 exsheathed larvae via an abomasal cannula (Group D) or 15,000 adult worms via an abomasal cannula (Group E). Whereas the presence of adult worms rapidly increased serum pepsinogen (after 8 h) and abomasal pH and serum gastrin (after about 19 h), the early infective larval stages, regardless of the infection regime, had minimal effects until the abrupt rise in all parameters 5-6 days after infection. Abomasal pH returned to near normal levels when the infections became patent and was not re-elevated by a subsequent trickle infection, whereas serum gastrin and pepsinogen remained high. The initial hypergastrinaemia was coincident with the increased abomasal pH, but was preceded by the increase in serum pepsinogen. In several sheep, serum pepsinogen increased very little during the parasitism, although there were typical effects on abomasal pH and serum gastrin. Serum gastrin was depressed when the abomasal pH exceeded about 5.5. It is suggested that an inhibitor of gastrin release is generated by proliferating abomasal microbes under these conditions and that this is a limitation to the use of elevated serum gastrin in the diagnosis of parasitism in individual sheep.

Different patterns of faecal egg output following infection of Scottish blackface lambs with Ostertagia circumcincta.

Faecal nematode egg counts were monitored in 184 Scottish Blackface lambs during natural exposure to a mixed, predominantly Ostertagia circumcincta infection and 12 lambs were selected which showed consistently zero (low count group; nine lambs) or consistently positive faecal egg counts (high count group; three lambs). These lambs were then treated with anthelmintic and challenged with 50,000 infective larvae of O. circumcincta and monitored thrice-weekly for 38 weeks; they were then re-challenged with another 50,000 infective larvae of O. circumcincta and monitored for a further 8 weeks. All sheep gave positive egg counts following deliberate infection. However, there was considerable variation among sheep in the size and timing of the peak in egg production. In particular, the pattern of mean values for faecal egg counts was different in the two groups. Egg counts were lower in the later periods of the extended infection in both groups of sheep. During the first half of the extended infection, egg counts were lower in sheep from the low count group, but during the second half of the infection the pattern was reversed and egg counts were lower in sheep from the high count group. There was a weak positive correlation between egg counts following anthelmintic treatment and 28 days exposure to natural infection and egg counts 28 days after a deliberate infection. Egg counts in the later stages of the deliberate infection were strongly but negatively correlated with egg counts following natural infection. The results of these studies show that differences in egg count following natural infection can be reproduced in experimental infections and that there is substantial variation in the pattern of egg production over time in different sheep. They also suggest that naturally resistant lambs are better able to delay worm development than naturally susceptible lambs.

Gastrin and gastrin-related responses to infection with Ostertagia ostertagi in the calf.

The effects of a single challenge with 60,000 infective Ostertagia ostertagi larvae on blood and gastrointestinal mucosal gastrin concentrations, gastrin-producing G-cell numbers in the pyloric mucosa and growth of different parts of the gut were investigated in 16, two-and-a-half-month-old calves. Infected calves exhibited a rise in abomasal pH which was accompanied by a 145 per cent increase in wet weight of the fundic mucosa (P < 0.05) and a significant rise in blood total gastrin concentrations (P < 0.01). Circulating little gastrin (G-17) was unaffected. Pyloric mucosal total gastrin concentrations remained unaltered in the infected calves until day 28 when levels fell to 36.9 per cent of control group values (P < 0.01). Pyloric mucosal G-cell numbers declined during the experiment in the infected group. It is suggested that release of previously stored tissue gastrin and not a change in G-cell numbers contributes to the hypergastrinaemia associated with ostertagia infection in the calf.

[The serological diagnosis of gastrointestinal nematode infections in cattle]. / De serologische diagnose van gastro-intestinale nematodeninfecties bij runderen.

Ostertagia ostertagi and Cooperia oncophora are widely distributed and are the most important parasites affecting young bovine livestock. Therefore, there is a substantial need for sensitive and specific parameters in support of their diagnosis, especially for sub-clinical disease correlated to production loss. In this review, the value and the application as a diagnostic tool of pepsinogen, gastrin and antibody response are discussed. An increase in pepsinogen or gastrin reflects mucosal damage caused by an Ostertagia infection. Some controversy exists about the level of pepsinogen and gastrin, which may be considered indicative for the diagnosis of clinical and sub-clinical ostertagiasis. Pepsinogen levels between 3,000 tot 4,000 mU tyrosine are regarded indicative for subclinical disease, values in excess of 5,000 mU tyrosine are considered significant for diagnosing clinical disease. For gastrin, it is suggested that based on group means, values of 400 pg/ml are indicative for subclinical parasitic disease in calves with reduced daily weight gain, while threshold levels of > or = 1000 pg/ml gastrin are representative for clinical ostertagiasis. Antibody responses to Ostertagia and Cooperia can be assessed using the enzyme immunoassay (EIA). Until now, mainly crude worm extracts have been used as antigen source in the EIA. They are not species-specific as discussed experiments provide evidence of a close relationship between the onset of parasitic disease and the evolution of the group mean parameters. However, data demonstrate serious variations between animals, which impede a reliable individual diagnosis. For longitudinal epidemiological studies especially pepsinogen and gastrin have proven their value, exhibiting fast fluctuations induced by infection or as a result of treatment. Conversely antibody levels were found to be more stable and therefore are useful in large cross-sectional studies, enabling a rough assessment of the degree of infection.

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.

An association of faecal egg counts and prolactin concentrations in sera of periparturient Angora goats.

Faecal egg counts and serum prolactin concentrations in 13 pregnant and five non-pregnant Angora goats were monitored over a period of 20 weeks. The mean weekly egg counts of pregnant goats were significantly higher (P less than 0.01) than those of non-pregnant goats. In pregnant goats the mean egg counts in the 6 week post-partum period were significantly higher (P less than 0.01) than those of 6 weeks prepartum. The mean prolactin concentration of pregnant goats during the 6 week post-partum period was significantly higher (P less than 0.01) than that of 6 weeks pre-partum. During the 6 to 3 weeks before parturition, the prolactin values generally remained low (below 100 ng ml-1). The rise in prolactin concentration started between 3 weeks and 1 week before parturition. Only in pregnant goats was there a positive linear regression between prolactin levels and faecal egg counts.

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.