Use of enzyme-linked immunoassays for antibody to types C and D botulinum toxins for investigations of botulism in cattle

The development of specific enzyme-linked immunosorbent assays (ELISA) for antibody to types C and D Clostridium botulinum toxins for investigation of botulism in cattle is described. Partially purified type C and D toxins were used as antigens to develop these ELISAs. Specificity of the ELISAs was evaluated on sera from 333 adult beef and dairy cattle from areas with no history or evidence of botulism in animals or water birds. The test was also evaluated on sera from 41 herds that included herds vaccinated against botulism, confirmed botulism cases and herds from areas where the disease is considered endemic. The ELISAs detected the presence of antibody to botulinum toxins in samples from vaccinated cattle and both convalescent and clinically normal animals from unvaccinated herds with outbreaks of botulism. Antibody was also found in unvaccinated animals from herds in which there had been no diagnosed botulism cases in areas where botulism was considered endemic. Sera from some unvaccinated cattle with high ELISA reactivity was shown to be protective for mice in botulinum toxin neutralisation tests. The use of these tests in investigations of botulism in cattle is discussed.     

Leptospira interrogans serovar hardjo is not a major cause of bovine abortion in Victoria

The aim of this study was to determine whether evidence could be obtained of foetal infection with Leptospira interrogans serovar hardjo in aborted foetuses collected from dairy farms. Material from 197 abortions occurring over a wide area of Victoria was collected over 3 years. None of 195 foetal kidney cultures or 7 cultures from membranes was positive for leptospiral organisms. Immunogold silver staining for leptospires was performed on sections of kidneys, lungs or heart from 156 foetuses, with negative results. Evidence of transient leptospiral infection in 11 of 123 foetuses was obtained by foetal heart blood serology. Two isolates of L. interrogans serovar hardjo were obtained from the urine of milking cows. These strains were examined by restriction endonuclease analysis and both were shown to be of the genotype Hardjobovis, as have been all Australian isolates studied so far. It appears that foetal infection with serovar hardjo is not associated with any substantial proportion of bovine abortions in Victoria, in contrast to the situation in Northern Ireland. The apparent absence from Victoria of the pathogenic genotype Hardjoprajitno is a possible explanation.     

Adrenocortical suppression by topically applied corticosteroids in healthy dogs

Three corticosteroid products (triamcinolone acetonide, fluocinonide, betamethasone valerate) and a control product composed of water, petrolatum, mineral oil, cetyl alcohol, steryl alcohol, sodium lauryl sulfate, cholesterol, and methylparaben each were applied topically to healthy dogs (5 dogs/product) once daily for 5 consecutive days. Plasma concentrations of immunoreactive adrenocorticotropic hormone (iACTH) and cortisol were determined before 1 microgram of ACTH/kg of body weight was given intravenously (pre-ACTH values) and cortisol was again measured 60 minutes after ACTH was given (post-ACTH values). Cortisol and iACTH concentrations were determined in each dog before, during, and after administration of the corticosteroid products. All 3 corticosteroids caused prompt and sustained pituitary-adrenocortical suppression. Compared with control applications, the application of corticosteroids resulted in significant reduction of plasma cortisol and iACTH concentrations by day 2 of treatment, and the lower concentrations continued to day 5. One week after the last application of the corticosteroids, plasma iACTH concentrations in the corticosteroid-treated dogs had returned to the range of values for the control dogs; however, pre- and post-ACTH cortisol concentrations remained suppressed in all corticosteroid-treated dogs. Two weeks after the last treatment, the pre-ACTH plasma cortisol concentrations of corticosteroid-treated dogs returned to those of the control dogs, but the post-ACTH plasma cortisol concentrations remained suppressed. By 3 weeks after the last treatment, post-ACTH plasma cortisol concentrations of dogs treated with triamcinolone acetonide had returned to the range of values for the control dogs, but remained suppressed in the other 2 groups of dogs. All indices of pituitary-adrenocortical activity were within the control range by 4 weeks after the last treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Endocrine responses of healthy parrots to ACTH and thyroid stimulating hormone

Effects of exogenous ACTH on plasma corticosterone and cortisol concentrations and the effects of thyroid stimulating hormone (TSH) on plasma triiodothyronine (T3) and thyroxine (T4) were determined in the following 3 species of parrots: red-lored Amazon (group 1), blue-fronted Amazon (group 2), and African gray (group 3). Each bird was given ACTH (0.125 mg/bird) IM, except for 3 to 4 birds in each group, which were given saline solution (controls). Blood samples were collected before and 90 minutes after ACTH stimulation. In group 1 (n = 12), mean plasma corticosterone concentrations increased significantly (P less than 0.001) from 1.06 microgram/dl (before ACTH) to 4.89 micrograms/dl (after ACTH); mean corticosterone concentrations increased in the control birds from 1.06 microgram/dl to 1.84 microgram/dl; and mean cortisol concentrations increased only slightly from 0.228 microgram/dl to 0.266 microgram/dl. In group 2 (n = 12), mean corticosterone concentrations increased significantly (P less than 0.001) from 2.09 micrograms/dl to 10.58 micrograms/dl; control mean corticosterone concentrations decreased slightly from 2.09 micrograms/dl to 1.77 microgram/dl; and mean cortisol concentrations increased from less than or equal to 0.16 microgram/dl to 0.266 microgram/dl. In group 3 (n = 12), mean plasma corticosterone concentrations increased significantly (P less than or equal to 0.001) from 2.33 micrograms/dl to 4.67 micrograms/dl; mean control plasma corticosterone concentrations decreased from 2.33 micrograms/dl to 1.68 microgram/dl; and plasma corticol concentrations were not detectable. Each bird was given TSH, IM (1 U/bird). Blood samples were collected before and 6 hours after TSH administration. Saline solution was not administered as controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

The survival of platypuses in captivity

Data are presented on the duration of survival of 228 platypuses at six Australian zoos between 1934 and 1988. Only 22.4% of all platypuses survived more than 1 year in captivity. Of 15 living platypuses, 3 had been held in captivity for less than 1 year, 5 for between 1 and 5 years, 6 for between 5 and 10 years and 1 for 21 years. Of 213 platypuses that died in captivity, 81.7% had died within 1 year; most within the first month. The duration of survival was unrelated to the age of animals at acquisition or to sex. The survival rate of animals donated to zoos, including "refugees", was similar to that of purpose-caught animals. Clearly, only a small proportion of platypuses adapted to captive husbandry. The cause of death of most platypuses was not established. However, infectious disease did not appear to be significant. Approximately 28% of deaths were related to inadequate husbandry. Recommendations are made to improve the survival of platypuses in captivity. Research has commenced in zoos to facilitate this goal.     

Comparative effects of abamectin and two formulations of ivermectin on the survival of larvae of a dung-breeding fly

Objectives To compare the survival of larvae of a dung-breeding fly in the faeces of cattle treated either with an injectable formulation of abamectin, or with oral or injectable formulations of ivermectin.
Design Replicated bioassays were conducted on larvae of the bush fly, Musca vetustissima, using faeces collected before and at intervals after drug treatment.
Animals Two cows and their calves were allocated to each of three drug treatments and dosed according to individual weights.
Procedures Differences in the proportions of larvae pupariating were used as measures of the toxicity of drug residues.
Results Development of fly larvae was inhibited in all faeces collected 1 to 4 days after treatment. In cattle treated with oral ivermectin, there was reduced larval survival in faeces collected 8 and 16 days after treatment, but by day 32, survival was equivalent to that recorded in the faeces of untreated cattle. With injectable ivermectin, there was no survival at day 8, limited survival at day 16 and, at day 32, survival was not significantly affected. With injectable abamectin, survival was completely suppressed until day 32, at which time the number of pupariating larvae did not differ significantly from that recorded in faeces from untreated animals.
Conclusion The oral formulation of ivermectin is eliminated more rapidly than the injectable formulation and, as a consequence, is likely to be less harmful to dung-feeding insects. Abamectin and ivermectin appear to equally toxic larvae of M vetustissima.     

Corticosterone- and aldosterone-secreting adrenocortical tumor in a dog

A dog was evaluated for clinical signs suggestive of hypercortisolemia. Serum biochemical testing revealed hypernatremia and hypokalemia. Serum cortisol concentration after injection of ACTH was less than the lower reference limit. An adrenal gland tumor was visualized via ultrasonography and computed tomography. Histologic examination confirmed that the mass was an adrenocortical carcinoma. Excess adrenal secretion of corticosterone was hypothesized to be the cause of the signs of glucocorticoid excess. Serum corticosterone secretion was high before and after ACTH injection, compared with clinically normal dogs and dogs with hypercortisolemia and classic hyperadrenocorticism. Hyperaldosteronemia was detected as well. Treatment with mitotane was instituted and successful for a period of 4-months until the dog was euthanatized for neurologic problems that were most likely unrelated to endocrine disease.     

Vesicles Cytoplasmic Injection: An Efficient Technique to Produce Porcine Transgene‐Expressing Embryos

The use of vesicles co‐incubated with plasmids showed to improve the efficiency of cytoplasmic injection of transgenes in cattle. Here, this technique was tested as a simplified alternative for transgenes delivery in porcine zygotes. To this aim, cytoplasmic injection of the plasmid alone was compared to the injection with plasmids co‐incubated with vesicles both in diploid parthenogenic and IVF zygotes. The plasmid pcx‐egfp was injected circular (CP) at 3, 30 and 300 ng/μl and linear (LP) at 30 ng/μl. The experimental groups using parthenogenetic zygotes were as follows: CP naked at 3 ng/μl (N = 105), 30 ng/μl (N = 95) and 300 ng/μl (N = 65); Sham (N = 105); control not injected (N = 223); LP naked at 30 ng/μl (N = 78); LP vesicles (N = 115) and Sham vesicles (N = 59). For IVF zygotes: LP naked (N = 44) LP vesicles (N = 94), Sham (N = 59) and control (N = 79). Cleavage, blastocyst and GFP+ rates were analysed by Fisher's test (p < 0.05). The parthenogenic CP naked group showed lower cleavage respect to control (p < 0.05). The highest concentration of plasmids to allow development to blastocyst stage was 30 ng/μl. There were no differences in DNA fragmentation between groups. The parthenogenic LP naked group resulted in high GFP rates (46%) and also allowed the production of GFP blastocysts (33%). The cytoplasmic injection with LP vesicles into parthenogenic zygotes allowed 100% GFP blastocysts. Injected IVF showed higher cleavage rates than control (p < 0.05). In IVF zygotes, only the use of vesicles produced GFP blastocysts. The use of vesicles co‐incubated with plasmids improves the transgene expression efficiency for cytoplasmic injection in porcine zygotes and constitutes a simple technique for easy delivery of plasmids.     

Effect of Trilostane and Mitotane on Aldosterone Secretory Reserve in Dogs with Pituitary‐Dependent Hyperadrenocorticism

Background

Maximal aldosterone secretion in healthy dogs occurs 30 minutes postadrenocorticotropin (ACTH; 5 μg/kg IV) stimulation. The effect of trilostane and mitotane on aldosterone at that time is unknown.

Objectives

To assess the effect of trilostane and mitotane in dogs with pituitary‐dependent hyperadrenocorticism on aldosterone secretory reserve. To determine if aldosterone concentration correlates with electrolyte concentrations.

Animals

Serum collected from 79 client‐owned dogs and 33 stored samples.

Methods

Client‐owned dogs had ACTH stimulation tests with cortisol concentrations measured at 0 and 60 minutes and aldosterone concentrations measured at 0, 30, and 60 minutes. Stored samples had aldosterone concentrations measured at 0 and 60 minutes. Ten historical clinically healthy controls were included. All had basal sodium and potassium concentrations measured.

Results

The aldosterone concentrations in the mitotane‐ and trilostane‐treated dogs at 30 and 60 minutes post‐ACTH were significantly lower than in clinically healthy dogs; no significant difference was detected in aldosterone concentration between 30 and 60 minutes in treated dogs. However, a significantly higher percentage of dogs had decreased aldosterone secretory reserve detected at 30 minutes than at 60 minutes. At 30 minutes, decreased secretory reserve was detected in 49% and 78% of trilostane‐ and mitotane‐treated dogs, respectively. No correlation was detected between aldosterone and serum electrolyte concentrations.

Conclusions and Clinical Importance

Decreased aldosterone secretory reserve is common in trilostane‐ and mitotane‐treated dogs; it cannot be predicted by measurement of serum electrolyte concentrations. Aldosterone concentration at 30 minutes post‐ACTH stimulation identifies more dogs with decreased aldosterone secretory reserve than conventional testing at 60 minutes.