An evaluation of an oral formulation of moxidectin against selected anthelmintic-resistant and -susceptible strains of nematodes in lambs

The efficacy of an oral formulation of the newly developed parasiticide, moxidectin, was tested against benzimidazole-resistant Haemonchus contortus, Trichostrongylus colubriformis, and Nematodirus spathiger, levamisole-resistant Ostertagia circumcincta, and susceptible Cooperia curticei infections in weaned lambs. Thirty-two lambs were experimentally infected with mixed doses of the above strains of nematodes. They were allocated into four treatment groups by stratified randomisation using liveweights and faecal egg counts 28 days later. One group received moxidectin at 0.2 mg/kg liveweight, one group oxfendazole at 4.5 mg/kg liveweight, one group levamisole at 7.5 mg/kg liveweight and the last group remained untreated as the control. Worm burdens in the lambs at slaughter 10 days after oral treatment confirmed the resistance status of the nematode strains used, and showed that moxidectin had a greater than 99.9% efficacy (p<0.01) against all of them. No adverse effects due to treatment with moxidectin were observed in any of the animals.     

Consequences of anthelmintic resistance on liveweight gain of lambs on commercial sheep farms

AIM: To assess the consequences of anthelmintic resistance on commercial sheep farms on liveweight (LW) gains and susceptibility to diarrhoea of growing lambs. METHODS: Five farms with a history of resistance to benzimidazole drenches were selected. On each farm, 150 ewe lambs were randomly allocated to 1 of 3 treatment groups (n=50). Group 1 was treated 5 times at 28-day intervals with oxfendazole (to which nematode resistance had been demonstrated); Group 2 was treated 5 times at 28-day intervals with levamisole or levamisole + oxfendazole (to which nematode resistance had not been demonstrated) and; Group 3 was treated with a combination of slow-release albendazole capsules and oral moxidectin (intended to totally suppress nematode infection). Differentiated faecal egg counts (FECs), FEC reduction tests (FECRT), LW gain and degree of faecal soiling around the breech (dag scores) were determined and compared between groups. RESULTS: Pre-treatment FECs in Group 1 were similar to or slightly lower than those of Group 2. Efficacy of oxfendazole in Group 1 varied between farms and over time within farms, the reduction in FECs after treatment varying from 0% to 95%. The genera identified as resistant on each farm also varied over time. Lambs from Group 3 had lower FECs, lower dag scores and higher growth rates than lambs from Group 2, which in turn had higher LW gains than lambs from Group 1. The overall LW gains during the 5 months of the study were 7.03+/-0.27 kg for Group 1, 8.33+/-0.27 kg for Group 2, and 9.91+/-0.31 kg for Group 3 (mean+/-SEM; means differed significantly from each other, p<0.01). CONCLUSIONS: The decrease in growth rates associated with the continued use of an incompletely effective anthelmintic were surprisingly small in situations where all lambs grazed together.     

Longitudinal investigation of protozoan parasites in meat lamb farms in southern Western Australia

In this study, 96 faecal samples were collected from pregnant Merino ewes, at two broad-acre, commercial sheep farms in southern Western Australia, on two separate occasions (16 and 2 weeks prior to lambing). Following lambing, 111 (Farm A) and 124 (Farm B) female crossbred lambs (2-6 weeks old), were individually identified using ear tags (a numbered tag and a radio-frequency tag). A total of 1155 faecal samples were collected only from these individually identified lambs on five separate sampling occasions. All samples were screened using PCR to detect Cryptosporidium (18S rRNA and actin loci) and Giardia duodenalis (glutamate dehydrogenase and triosephosphate isomerise loci). The overall prevalences (lambs positive for a parasite on at least one of the five samplings) at Farm A and B were 81.3% and 71.4%, respectively for Cryptosporidium and similarly 67.3% and 60.5% for Giardia, respectively. Cryptosporidium and Giardia prevalences at individual samplings ranged between 18.5 and 42.6% in lambs and were <10% in the ewes. Cryptosporidium xiaoi was the most prevalent species detected at all five samplings and was also isolated from lamb dam water on Farm B. Cryptosporidium ubiquitum was most commonly detected in younger lambs and Cryptosporidium parvum was detected in lambs at all five samplings, typically in older lambs and as part of a mixed species infection with C. xiaoi. A novel, possibly new genotype (sheep genotype I), was identified in six Cryptosporidium isolates from Farm B. Giardia duodenalis assemblage E was the most common genotype detected at all five samplings, with greater proportions of assemblage A and mixed assemblage A and E infections identified in older lambs. This longitudinal study identified high overall prevalences of Cryptosporidium and Giardia in lambs grazed extensively on pastures, while reinforcing that sampling a random selection of animals from a flock/herd on one occasion (point prevalence), underestimates the overall prevalence of these parasites in the flock/herd across an extended time period. Based on these findings, grazing lambs were identified as a low risk source of zoonotic Cryptosporidium and Giardia species/genotypes, with these protozoa detected at all five samplings in some lambs, indicating that these individuals were either unable to clear the naturally acquired protozoan infections or were repeatedly re-infected from their environment or other flock members.     

Sheep performance under intensive continuous grazing of native grasslands of <Emphasis Type="Italic">Paspalum notatum</Emphasis> and <Emphasis Type="Italic">Axonopus compressus</Emphasis> in the subtropical region of the Highlands of Central Mexico

Liveweight gain was evaluated in tropical Dorper X Pelibuey lambs under intensive continuous grazing of native grasslands dominated by Paspalum notatum (PN) or Axonopus compressus (AC) in the subtropics of Central Mexico. Two trials were undertaken. Trial 1 lasted 12 weeks with 10 lambs (initial weight 18 +/- 2.57 kg, 3 months old) per treatment in 2002, and Trial 2 for 13 weeks with 8 lambs (initial weight 24.0 +/- 2.0 kg, 4 months old) per treatment. Lambs were weighed once per week, and liveweight change was estimated by linear regression over day of the experiment, using individual regression coefficients as unbiased estimates of daily liveweight change; analysed in a random block design. Lambs on Trial 1 gained 0.061 kg/lamb/day on PN and 0.047 kg/lamb/day on AC (P > 0.05) at an overall mean stocking rate of 25 lambs/ha. In Trial 2, liveweight gain was significantly larger in PN (0.060 kg/lamb/day) than on AC (0.043 kg/lamb/day) (P < 0.05), at a mean stocking rate of 21.5 lambs/ha. It is concluded that intensive continuous grazing of native grasslands in the subtropics of the highlands of Central Mexico enables moderate liveweight gains for weaned lambs during the rainy season; with better results in grasslands dominated by Paspalum notatum.     

Impacts of naturally acquired protozoa and strongylid nematode infections on growth and faecal attributes in lambs

On two separate sampling occasions, faecal samples were collected from lambs (2-5 months of age) grazing pasture on two separate sheep farms in southern Western Australia. Live weight, body condition score (BCS), faecal consistency score (FCS) and faecal dry matter percentage (DM%) were measured. Faecal samples were screened by PCR for Cryptosporidium (18S rRNA, actin and 60 kDa glycoprotein [gp60] loci), Giardia duodenalis (glutamate dehydrogenase [gdh] and β-giardin) and patent strongylid nematode infections (ITS-2 nuclear ribosomal DNA for Haemonchus contortus, Teladorsagia circumcincta, Trichostrongylus spp. Chabertia ovina and Oesophagostomum spp.). Faecal worm egg counts (WECs) were performed using a modified McMaster WEC technique. The WECs were adjusted for FCS and transformed using log(10)(adjusted WEC+25) prior to statistical analyses. Cryptosporidium, Giardia and Trichostrongylus spp. detected by PCR were associated with an increased risk of non-pelleted faeces (FCS ≥ 3.0) for both flocks. Cryptosporidium-positive lambs were 2.8-11.6 times more likely to have non-pelleted faeces and Giardia-positive lambs were 2.4-14.0 times more likely to have non-pelleted faeces compared to lambs negative for each respective parasite. Lambs positive for both Cryptosporidium and Giardia were 2.9-11.8 times more likely to have non-pelleted faeces than lambs positive for only one or neither of these parasites. Mixed internal parasite infections were found to have greater impacts on FCS and BCS than single infections. A higher number of internal parasites detected per lamb was associated with lower BCS and more loose faeces. The relationship between parasite detection and live weight or growth rate were inconsistent for both flocks. Adjusted WEC was correlated with FCS and faecal DM% for one flock only, although little or no correlation was found with live weight and growth rate for both flocks. Cryptosporidium ubiquitum and Cryptosporidium parvum were the most prevalent Cryptosporidium species isolated in the two flocks. Giardia assemblage E was the most commonly isolated genotype assemblage from both flocks, while assemblage A was isolated almost as frequently as assemblage E in the one flock. One flock was a potential source of zoonotic Cryptosporidium and the other flock was a potential source of zoonotic Giardia.     

Prevalence of Cryptosporidium in sheep and goats bred on five farms in west-central region of Poland

Faecal specimens were taken from 205 sheep and goats housed in five different localities in the west-central part of Poland. All faecal specimens were examined for Cryptosporidium by using microscopy screening of smears stained by modified Ziehl-Neelsen technique and commercial enzyme immunoassay. PCR technique using genus specific primers was additionally applied in the surveys of 10 faecal specimens collected from lambs. C. parvum infection was identified in 16 of 159 sheep (10.1%). Lambs were more often infected than adult sheep, and the intensity of infection was higher in lambs than in sheep, as a rule. Both lambs and sheep examined in the study were asymptomatically infected with Cryptosporidium. Both microscopy and enzyme immunoassay methods gave one false negative result. The examination of 10 faecal samples revealed 100% agreement among the results obtained by microscopic, immunologic and molecular methods. None of the goats raised on three farms were infected with Cryptosporidium.     

Cryptosporidium and Giardia associated with reduced lamb carcase productivity

On two extensive sheep farms in southern Western Australia, 111 (Farm A) and 124 (Farm B) female crossbred lambs (2-6 weeks old) were randomly selected and individually identified using ear tags (a numbered tag and radio-frequency tag) at marking. On five separate occasions, faecal samples were collected and live weight, body condition score (BCS), faecal consistency score (FCS), breech fleece faecal soiling score and faecal dry matter percentage (DM%) were recorded. Lamb hot carcase weight (HCW) and dressing percentage were measured at slaughter. Faecal samples were screened by PCR for Cryptosporidium (18S rRNA, actin and 60 kDa glycoprotein [gp60] loci), Giardia duodenalis (glutamate dehydrogenase [gdh] and triosephosphate isomerise [tpi]) and Campylobacter jejuni (16S rRNA). Observation of Eimeria oocysts and faecal worm egg counts (WECs) were performed using a modified McMaster technique. The WECs were adjusted for FCS for analyses. Faecal samples were screened for patent strongylid infections using PCR (specifically ITS-2 nuclear ribosomal DNA for Teladorsagia circumcincta, Trichostrongylus spp. and Haemonchus contortus). Lambs positive for Cryptosporidium at least once had lighter HCWs by 1.25 kg (6.6%) (P=0.029) and 1.46 kg (9.7%) (P<0.001) compared to lambs never positive for Cryptosporidium for Farms A and B respectively. Similarly, dressing percentages were 1.7% (P=0.022) and 1.9% (P<0.001) lower in Cryptosporidium-positive lambs on Farms A and B respectively. Lambs positive for Giardia at least once had 0.69 kg (P<0.001) lighter HCWs and 1.7% (P<0.001) lower dressing percentages compared to lambs never positive for Giardia on Farm B only. Cryptosporidium-positive lambs at the second sampling were 4.72 (P=0.010) and 3.84 (P=0.002) times more likely to have non-pelleted faeces compared to Cryptosporidium-negative lambs for Farms A and B respectively. Breech fleece faecal soiling scores of Cryptosporidium-positive lambs were 3.36 (P=0.026) and 2.96 (P=0.047) times more likely to be moderate to severe (scores 3-5), compared to negative lambs at the second sampling for Farms A and B respectively. Live weight, growth rate and BCS were inconsistently associated with protozoa detection across different samplings and farms. Adjusted WEC was correlated positively with FCS and negatively with faecal DM%, differing between sampling occasions and farms. Campylobacter jejuni prevalence was very low (<1%). Adjusted WEC were not correlated with carcase attributes, growth rates or live weights. This study is the first to quantify productivity consequences of naturally acquired protozoa infections in lambs managed under extensive farming conditions.     

Production and immunological responses associated with controlled-release-capsule vs 5-drench preventive anthelmintic programmes for parasite control in lambs

AIMS: To determine whether: a) using a controlled-release anthelmintic capsule (CRC) instead of a programme of 5 oral drenches administered at 3-4 week intervals, would delay the development of anti-parasite immunity in lambs; b) the use of ivermectin instead of albendazole, administered either as a CRC or as a programme of 5 oral drenches, would delay the development of anti-parasite immunity in lambs; c) lambs treated with CRCs would have higher liveweight gains than lambs drenched orally 5 times at 3-4 week intervals, and; d) delayed onset of anti-parasite immunity is associated with reduced liveweight gains in the period following anthelmintic treatment. METHODS: Three field trials were conducted, 1 on a research farm and 2 on commercial sheep farms, in which groups of 30 lambs were treated with either a CRC containing albendazole, a CRC containing ivermectin, 5 oral drenches with albendazole, or 5 oral drenches with ivermectin, administered at 3-4 week intervals. Liveweights and faecal nematode egg counts (FECs) were recorded in all trials. Immunoglobulin-G (IgG) antibody levels to Ostertagia circumcincta and Trichostrongylus colubriformis adult and larval antigens were measured in Trials 1 and 3, and fleece weights and resistance of animals to nematode challenge infection were measured in Trial 1. RESULTS: CRC-treated lambs had higher levels of antibodies to O. circumcincta infective-stage larvae (L3) than orally drenched lambs in Trial 3, but no other immunological differences due to mechanism of delivery were detected. Antibody levels were lower in lambs treated with ivermectin than albendazole, as a CRC or oral drench in Trial 1, but this was not associated with any measurable effects on FEC or productivity. No significant differences (p>0.05) were detected between drench types (albendazole vs ivermectin) or delivery mechanisms (CRC vs oral drenching) in any of the production parameters measured, in any of the trials. Albendazole-CRCs failed to control FECs in all 3 trials. CONCLUSIONS: Although some differences between treatments in antibody levels were detected these were not associated with measurable differences in level of parasitism or productivity of lambs. CRC use did not appear to offer substantial gains in productivity over a structured programme of 5 oral drenches administered at 3-4 week intervals.     

Differential effects of the endocrine-disrupting compounds bisphenol-A and octylphenol on gonadotropin secretion, in prepubertal ewe lambs

This study examined the effects of long-term exposure to the endocrine-disrupting compounds (EDCs) Bisphenol-A (BPA) and Octylphenol (OP) on gonadotrophin secretion in pre-pubertal female sheep. Four-week-old, female lambs were randomly allocated to four groups (n=6), and twice each week treated with i.m. injections of either corn oil (vehicle controls), diethylstilbestrol (DES; 0.175mg/kg), BPA (3.5mg/kg) or OP (3.5mg/kg). After 5 weeks of treatment, animals were ovariectomized (ovx) and ovary weights recorded. Two weeks later, blood samples were collected from lambs every 15min for 6h, for LH pulse analysis. Animals were then euthanased and adrenal and kidney weight recorded. An age-related increase in tonic LH secretion was noted in Control, BPA- and OP-treated lambs, but was absent in DES-treated lambs. Following ovx, LH secretion increased in all except DES-treated lambs; FSH concentrations increased in all groups. BPA and DES significantly suppressed LH pulse frequency (C: 6.7+/-0.3pulses/6h, DES: 1.5+/-0.8pulses/6h, BPA: 2.3+/-0.8pulses/6h) and amplitude (C: 7.1+/-1.0ng/ml, DES: 1.9+/-0.6ng/ml, BPA: 1.6+/-0.4ng/ml). OP had no effect on LH secretion (Frequency: 5.8+/-0.5pulses/6h, amplitude: 8.0+/-2.0ng/ml). Ovary weight was similar among all groups. Results show that chronic in vivo exposure of prepubertal female lambs to BPA, at levels lower than those reported previously, can have significant effects on LH secretion that are comparable to those seen following exposure to the known xenoestrogen, DES. Exposure to an equal dose of the EDC OP, over the equivalent period of time was without effect on gonadotropin secretion in the prepubertal ewe lamb. These results indicate that exposure of prepubertal female lambs to the EDC BPA can induce significant effects on gonadotropin secretion, the potential long-term effects of exposure and the effects of these changes on reproductive performance and efficacy, therefore, merit further study.     

Efficacy of a single dose of oral antibiotic given within two hours of birth in preventing watery mouth disease and illthrift in colostrum-deficient lambs.

An antibiotic with a product licence limited to the treatment and control of infectious bacterial enteritis associated with Escherichia coli in piglets was tested for its ability to control watery mouth disease in neonatal lambs. Three groups of lambs were kept in conditions commonly encountered in intensive lambing systems, where high levels of environmental bacterial contamination may be expected. They were allocated at birth to: a control group (group 1) consisting of 18 colostrum-deprived lambs; group 2, consisting of 17 lambs given one feed of colostrum when they were two hours old; and group 3, consisting of 18 colostrum-deprived lambs given spectinomycin orally when they were two hours old. Nine group 1 lambs became diseased and were killed for humane reasons. Blood biochemical changes included hyperglycaemia followed by hypoglycaemia, lactacidaemia, hypoproteinaemia and metabolic acidosis, and postmortem examination of the diseased lambs showed signs consistent with endotoxaemia and a clinical diagnosis of watery mouth disease. Coliforms were isolated from the blood of all group 1 lambs and from half the lambs in groups 2 and 3, but endotoxaemia and watery mouth disease occurred only in group 1 lambs. The results for groups 2 and 3 showed that neither colostrum nor antibiotic at the rates and frequency used prevented bacteraemia, although consecutive samples were positive only on three occasions. Group 3 lambs consistently grew more rapidly than the surviving group 1 lambs and as rapidly as group 2 lambs. There was no evidence that male lambs were more prone to watery mouth disease than female lambs. The results indicated that the antibiotic spectinomycin did not induce endotoxaemia during low-grade bacteraemia and that a single oral dose given within two hours of birth protected colostrum-deprived lambs delivered into a contaminated indoor environment against watery mouth disease.     

Effect of parasitism on the pharmacokinetic disposition of ivermectin in lambs

The aim of this study was to investigate the effect of parasitism on plasma availability and pharmacokinetic behaviour of ivermectin (IVM) in lambs. Fourteen greyface Suffolk lambs (26.8 +/- 2.2 kg body weight) were selected for this study. Seven pairs of lambs were allocated into two groups in order to obtain an approximately even distribution. Group I (non-parasitized) was pre-treated by three repeated administrations of 5 mg/kg of fenbendazole (Panacur), in order to maintain a parasite-free condition. The lambs in group II (parasitized) did not receive any anthelmintic treatment and the natural infection was sustained by an oral inoculation of infective stages of nematode parasites. After the 85-day pre-treatment period both groups of animals were treated with IVM (200 microg/kg, Ivomec) by subcutaneous injection in the shoulder area. Both groups of animals were maintained under similar conditions of feeding and management. Blood samples were collected by jugular puncture at different times between 0.5 h and 25 days post-treatment. After plasma extraction and derivatization, samples were analysed by high-performance liquid chromatography with fluorescence detection. A computerized kinetic analysis was performed and data were compared using the unpaired Student's t-test. The parent molecule was detected in plasma between 30 min and either 12 (parasitized) or 20 (no parasitized) days post-IVM treatment. The area under the curve values of the parasitized group (75.2 +/- 15.5 ng x d/ml) were significantly lower that those observed in the parasite-free group (134.3 +/- 15.7 ng x d/ml). The mean residence time (MRT) of the parasitized group (2.93 +/- 0.16 days) was significantly lower than the MRT of healthy group (3.93 +/- 0.29 days). The results of this study have shown that a change in body condition followed by a parasitic infection is associated with significant changes in plasma disposition of IVM when it is administered subcutaneously to parasitized lambs. Therefore, variations in the condition induced by parasitism should be considered when these anthelmintics are used for treating parasitized animals.     

Faecal excretion profile of moxidectin and ivermectin after oral administration in horses

A study was undertaken to evaluate and compare faecal excretion of moxidectin and ivermectin in horses after oral administration of commercially available preparations. Ten clinically healthy adult horses, weighing 390-446 kg body weight (b.w.), were allocated to two experimental groups. Group I was treated with an oral gel formulation of moxidectin at the manufacturer's recommended therapeutic dose of 0.4 mg/kg b.w. Group II was treated with an oral paste formulation of ivermectin at the recommended dose of 0.2 mg/kg b.w. Faecal samples were collected at different times between 1 and 75 days post-treatment. After faecal drug extraction and derivatization, samples were analysed by High Performance Liquid Chromatography using fluorescence detection and computerized kinetic analysis.For both drugs the maximum concentration level was reached at 2.5 days post administration. The ivermectin treatment groups' faecal concentrations remained above the detectable level for 40 days (0.6 +/- 0.3 ng/g), whereas the moxidectin treatment group remained above the detectable level for 75 days (4.3 +/- 2.8 ng/g). Ivermectin presented a faster elimination rate than moxidectin, reaching 90% of the total drug excreted in faeces at four days post-treatment, whereas moxidectin reached similar levels at eight days post-treatment. No significant differences were observed for the values of maximum faecal concentration (C(max)) and time of C(max)(T(max)) between both groups of horses, demonstrating similar patterns of drug transference from plasma to the gastrointestinal tract. The values of the area under the faecal concentration time curve were slightly higher in the moxidectin treatment group (7104 +/- 2277 ng.day/g) but were not significantly different from those obtained in the ivermectin treatment group (5642 +/- 1122 ng.day/g). The results demonstrate that although a 100% higher dose level of moxidectin was used, attaining higher plasma concentration levels and more prolonged excretion and gut secretion than ivermectin, the concentration in faeces only represented 44.3+/- 18.0% of the total parental drug administered compared to 74.3 +/- 20.2% for ivermectin. This suggests a higher level of metabolization for moxidectin in the horse.     

Efficacy of a killed vaccine for the control of paratuberculosis in Australian sheep flocks

A field trial was undertaken from 1999 until 2004 to determine the efficacy of a killed M. a. paratuberculosis vaccine, Gudair, for the control of ovine Johne's disease (OJD) in merino sheep run under Australian pastoral conditions. On each of three farms experiencing significant OJD losses (5-15% per annum), 200 merino lambs (age 1-4 months) were vaccinated, and 200 lambs were left unvaccinated. Animal assessments and sample collections were conducted twice yearly until 4 or 5 years of age. The impact of vaccination on mortality rate, faecal shedding of M. a. paratuberculosis (by pooled and individual faecal culture), liveweight, wool productivity, vaccine injection site lesions and cellular (BOVIGAM) and humoral (PARACHEK) immunity was examined. Vaccination stimulated cell-mediated and humoral immune responses, reduced mortalities due to OJD by 90% and delayed faecal shedding for the first year post-vaccination. Thereafter, the prevalence of shedders among vaccinates was reduced by 90%. The numbers of M. a. paratuberculosis excreted by the vaccinated groups were also reduced by at least 90% at most sampling times. However, high levels of excretion by vaccinates occurred on some occasions, and although only 7 of 600 vaccinates died from OJD, all 7 had multibacillary lesions. Thus there remains a risk that some vaccinated sheep will transfer the disease. Small reductions in liveweight were found in vaccinated lambs in the first year, but there was little effect on wool production. Vaccine injection site lesions were detected in almost 50% of sheep after 2 months, and these persisted for at least 4 years in 20-25% of vaccinates. Data from this trial enabled the registration of Gudair in Australia in 2002 and underpins the pivotal role of vaccination in the current management of OJD.     

Biological control of field infections of nematode parasites of young sheep with Duddingtonia flagrans and effects of spore intake on efficacy

A field study was undertaken to determine the effects of feeding Duddingtonia flagrans to young Merino sheep on pasture. A total of 60 mixed sex lambs 4-5 months old were divided into six even groups on the basis of liveweight. On Monday to Friday, each week for 6 months, three groups were offered barley grains on which D. flagrans had been cultured while the other three groups remained untreated. Every 4 weeks liveweights were recorded and faecal samples collected for nematode egg count estimation. Feeding D. flagrans reduced faecal egg counts and tended to improve liveweight gains, but considerable differences were observed between groups within treatment. These differences are thought to result from variations between the groups in consumption of the treated barley with the "best" consumers showing the greater effects of treatment.     

Effect of hypertonic vs isotonic saline solution on responses to sublethal Escherichia coli endotoxemia in horses

Cardiovascular responses to sublethal endotoxin infusion (Escherichia coli, 50 micrograms/ml in lactated Ringer solution at 100 ml/h until pulmonary arterial pressure increased by 10 mm of Hg) were measured 2 times in 5 standing horses. In a 2-period crossover experimental design, horses were either administered hypertonic (2,400 mosm/kg of body weight, IV) or isotonic (300 mosm/kg, IV) NaCl solution after endotoxin challenges. Each solution was administered at a dose of 5 ml/kg (infusion rate, 80 ml/min). Complete data sets (mean arterial, central venous, and pulmonary arterial pressures, pulmonary arterial blood temperature, cardiac output, total peripheral vascular resistance, heart rate, plasma osmolality, plasma concentration of Na, K, Cl, and total protein, blood lactate concentration, and PCV) were collected at 0 (baseline, before endotoxin infusion), 0.25, 1, 1.5, 2, 2.5, 3, 3.5, 4, and 4.5 hours after initiation of the endotoxin infusion. Blood constituents alone were measured at 0.5 hour and cardiovascular variables alone were evaluated at 0.75 hour. By 0.25 hour, endotoxin infusion was completed, a data set was collected, and saline infusion was initiated. By 0.75 hour, saline solutions had been completely administered. Mean (+/- SEM) cardiac output decreased (99.76 +/- 3.66 to 72.7 +/- 2.35 ml/min/kg) and total peripheral resistance (1.0 +/- 0.047 to 1.37 +/- 0.049 mm of Hg/ml/min/kg) and pulmonary arterial pressure (33.4 +/- 0.86 to 58.3 +/- 1.18 mm of Hg) increased for both trials by 0.25 hour after initiation of the endotoxin infusion and prior to fluid administration. For the remainder of the protocol, cardiac output was increased and total peripheral resistance was decreased during the hypertonic, compared with the isotonic, saline trial.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of immunization against somatostatin in the pregnant ewe on growth and endocrine status of the neonatal lamb

Absorption of somatostatin (SRIF) specific antibodies from colostrum of ewes actively immunized against SRIF may improve growth rate of the neonatal lamb by neutralizing the inhibitory effects of SRIF on pituitary and thyroid function. Growth and endocrine parameters in the offspring of SRIF immunized (SI) and control (C) crossbred ewes were examined. Lamb weight was recorded at birth and twice each week to 24 days of age. Blood samples were collected prior to first suckle and twice each week. At 21 to 24 days of age, in separate experiments, lambs were infused with glucose (0.29 g/kg), arginine (0.25 g/kg) or thyrotropin-releasing hormone (TRH; 0.33 microgram/kg). A strong correlation (R = 0.88; P less than .01) was observed between anti-SRIF titre in the ewe at parturition and in the lamb at 3 days of age. No effect on lamb birth weight (SI 4.28 +/- 0.27 kg; C 4.35 +/- 0.23 kg) was observed. At 24 days of age cumulative gain in SI lambs (5.4 +/- 0.32 kg) was greater (P less than .05) than in C lambs (4.5 +/- 0.32 kg). The growth hormone secretory responses to glucose or arginine were not affected by treatment. Plasma IGF-I, plasma thyroxine (T4) and the plasma thyrotropin and T4 responses to TRH were not different between treatments. Plasma triiodothyronine (T3) was higher (P less than .05) in SI (2.46 +/- .10 ng/ml) than in C (2.01 +/- .05 ng/ml) lambs, however, the plasma T3 response to TRH was lower in SI lambs. Plasma glucose (mg/dl) was higher (P less than .05) in SI (118.4 +/- 1.7) than in C (106.0 +/- 4.0) lambs. Plasma insulin was not affected by treatment. Increased plasma T3 and glucose concentrations during SRIF immunoneutralization in the neonate lamb may be important factors contributing to the growth response observed.     

Effects of allopurinol on endotoxin-induced increase in serum xanthine oxidase in the horse

Using a modified bovine milk enzyme kinetic assay, xanthine oxidase activity of serum collected from 34 adult, healthy horses of both sexes was determined. Enzyme activity varied from 0 to 126 mU litre-1 with a mean of 44.95 +/- 21.05 mU litre-1. The optimal pH and temperature for maximal activity were 7.8 and 28 degrees C, respectively. Freezing the serum for four days at -70 degrees C did not destroy the enzyme activity. Various doses (25, 50 and 75 micrograms kg-1, intraperitoneally) of endotoxin (lipopolysaccharide D1 Escherichia coli O26:B6) previously known to have caused moderate to severe systemic clinical signs of endotoxaemia in horses produced a significant dose related increase in serum xanthine oxidase activity. Pretreatment (12 hours) with allopurinol (5 and 50 mg kg-1, intravenously [corrected]) significantly reduced the rise in xanthine oxidase activity in endotoxin (50 micrograms kg-1, intraperitoneally) treated horses. The results of this study suggest that xanthine oxidase catalysed production of superoxide radicals may play a role in the pathogenesis of endotoxaemia and that allopurinol, an alternate substrate, should be further evaluated for its therapeutic potential in endotoxin related systemic diseases in horses.     

Enzymeimmunoassay of oestrone sulphate concentrations in faeces for non-invasive pregnancy determination in mares

AIM: To determine the suitability of measuring faecal oestrone sulphate (OS) by enzymeimmunoassay as a means of determining pregnancy status in mares bred under New Zealand conditions. METHODS: An antibody-coated microtitre plate-based enzymeimmunoassay was used to determine the concentration of OS in faecal and plasma samples obtained from pregnant and non-pregnant mares. RESULTS: In non-pregnant mares, the mean faecal OS concentration was 34 ng/g, and the value three standard deviations above this was 80 ng/g. None of 427 faecal samples collected from 116 non-pregnant mares over a l-year period had an OS concentration >80 ng/g. Only five samples from three mares had an OS concentration >65 ng/g, the value two standard deviations above the mean non-pregnant value. Analysis of faecal OS concentrations in 532 faecal samples collected from 39 pregnant mares showed that as pregnancy progressed, an increasing proportion of faecal samples had OS concentrations >80 ng/g. None of the mares 150 days or more pregnant had faecal OS concentrations <50 ng/g, and 204/220 samples obtained from these mares had faecal OS concentrations >80 ng/g. Following foaling or foetal death, elevated faecal OS concentrations returned quickly to non-pregnant levels. The mean +/- s.e.m. plasma level of OS in five mares bled daily throughout one oestrous cycle was 1.7 +/- 0.2 ng/ml. Sixty-eight blood samples from pregnant mares bled up to five times between 92 days after mating and foaling all had plasma OS concentrations >30 ng/ml, with 64/68 being >50 ng/ml. CONCLUSIONS: This study shows that measuring faecal OS concentrations by enzymeimmunoassay offers a convenient, accurate, non-invasive means of determining pregnancy status in mares from 150 days after mating onwards. Mares with faecal OS concentrations <50 ng/g can be considered not pregnant, while mares with faecal OS concentrations >80 ng/g can be considered pregnant. Those few mares returning a faecal OS concentration between 50 and 80 ng/g should be retested to obtain a conclusive result. Measuring plasma OS concentrations allows pregnancy status to be determined earlier (from 100 days after mating). Moreover, the discrimination between non-pregnant and pregnant levels is greater for OS in plasma than in faeces. CLINICAL RELEVANCE: Measurement of OS concentrations in faeces provides an alternative and non-invasive means of determining pregnancy status in mares from 150 days after mating.     

Ibuprofen prevents Pasteurella hemolytica endotoxin-induced changes in plasma prostanoids and serotonin, and fever in sheep

Intravenous infusion of Pasteurella hemolytica endotoxin caused marked increases in the plasma levels of thromboxane B2 (TxB2), prostaglandins (PG) and serotonin in sheep. The control values for TxB2, 6-keto-PGF1 alpha, PGF2 alpha, and serotonin before endotoxin infusion averaged 283 +/- 53 (standard error of mean), 281 +/- 14 and 199 +/- 27 pg/ml and 57 +/- 3 ng/ml, respectively. At 50 min during endotoxin infusion, these values were increased to their maximum of 376, 339, 325 and 202% of control, respectively. Body temperature increased from the control value of 39.5 +/- 0.1 degrees C to a maximum of 41.5 +/- 0.1 degrees C at 200-300 min of infusion. In the second part of this study, we have examined the effects of ibuprofen on endotoxin-induced increases in plasma PG, TxB2, and serotonin levels and body temperature. The control values for TxB2, 6-keto-PGF1 alpha, PGF2 alpha, and temperature prior to ibuprofen and endotoxin infusion averaged 238 +/- 35, 335 +/- 44 and 248 +/- 28 pg/ml, 65 +/- 3 ng/ml and 40.1 +/- 0.2 degrees C, respectively. A loading dose (15 mg/kg) of ibuprofen was followed by infusion of endotoxin (12 micrograms/kg) and ibuprofen (43.3 mg/kg) over 500 min. Plasma levels of 6-keto-PGF1 alpha and serotonin increased only to 131 and 149% of control at 50 min of infusion, and levels of PGF2 alpha and TxB2 decreased to 50 and 80% of control at 100 and 150 min of infusion, respectively. Temperature remained unchanged. Ibuprofen effectively suppressed endotoxin-induced increases in the plasma levels of TxB2, 6-keto-PGF1 alpha, PGF2 alpha, and serotonin and body temperature. It was concluded from the present study that nonsteroidal anti-inflammatory drugs as an adjunct to antibiotic therapy might have a rational basis in treatment of endotoxin toxicity.     

Prevalence and molecular characterisation of Cryptosporidium and Giardia in lambs and goat kids in Belgium

The prevalence of Cryptosporidium and Giardia was studied on 10 intensively reared sheep and goat farms in the province of East Flanders, Belgium. Random faecal samples were collected and examined using the Merifluor((R)) immunofluorescence assay. Cryptosporidium positive samples were withheld for molecular identification using primers targeting the 18S rDNA, 70 kDa heat shock protein and 60 kDa glycoprotein gene. For the molecular identification of Giardia the beta-giardin gene and a recently developed assemblage specific PCR based on the triose phosphate isomerase gene were used. The prevalence of Cryptosporidium in lambs was 13.1% (18/137), on 4 out of 10 farms. In goat kids the Cryptosporidium prevalence was 9.5% (14/148), on 6 out of 10 farms. The molecular characterisation of Cryptosporidium positive isolates indicated that in lambs (n=10) the cervine genotype was predominant, whereas in the goat kids (n=11) only C. parvum was identified, with subgenotypes IIaA15G2R1 and IIdA22G1. The Giardia prevalence was 25.5% (35/137) in lambs with all 10 farms being positive, and 35.8% (53/148) in goat kids with 8 out of the 10 farms being positive. Both in the goat kids and in the lambs the host specific assemblage E was most commonly identified. However, the zoonotic assemblage A was identified in 6 out of 28 goat kids and in 2 out of 8 lambs, based on the beta-giardin sequence alignment. Using the assemblage specific PCR, mixed assemblage A and E infections were additionally identified in 2 lambs and in 5 goat kids. The results of the present study indicate that both Cryptosporidium and Giardia are common parasites on intensively reared sheep and goat farms in the province of East Flanders, Belgium, and that they are a potential source for zoonotic infections.