The 1997/1998 epizootic of swine fever in the Netherlands: control strategies under a non-vaccination regimen.

The 1997/1998 epizootic of classical swine fever (CSF) in an area with high pig density in the Netherlands is described. The epizootic, which numbered 429 outbreaks, was controlled and finally eradicated after 14 months without resorting to vaccination. A further almost 1300 herds (1.1 million pigs) at close proximity of confirmed outbreaks were preventively culled because of the risk of having been infected. The pros and cons of this so-called "pre-emptive slaughter" are discussed. The long-lasting movement restrictions caused severe overcrowding especially in breeding farms. For reasons of animal welfare 6.5 million weaners and adult pigs had to be killed and destroyed, whereas another 2.6 million 3-17 days old piglets were euthanised to save long-term destruction capacity. The presumed routes of infection and factors influencing the epizootic are explained, as well as the various methods to bring the epizootic to a halt. The strategy for detecting outbreaks in an early stage, and the type of samples to be collected for laboratory diagnosis are emphasised from the general point of application. The direct costs of the epizootic, losses of exports not included, are estimated at US$ 2 billion.

Method for determination of pentobarbital in dry dog food by gas chromatography/mass spectrometry.

A procedure has been developed and validated for measuring the concentration of pentobarbital residues in dry, extruded animal feed in the range of 3-200 ng/g (ppb) with an estimated limit of quantitation of 2 ppb. The method was developed for surveillance purposes: to measure the concentration of euthanizing agent which might be present in feeds incorporating rendered products which themselves might include some fraction of euthanized animals. A previously published qualitative procedure was modified by adding isotopically labelled pentobarbital as an internal standard. Dry feed was ground and extracted with methanol. The extract was loaded on a mixed-mode (C-18, anion exchange) solid-phase extraction cartridge designed for barbiturate residues. Pentobarbital was eluted and derivatized for gas chromatography/mass spectrometry in positive ion chemical ionization mode. Quantitation was based on the ratio of dimethyl-pentobarbital MH+ (m/z 255) vs dimethyl-pentobarbital-d(5) (m/z 260) in standards and extracts. Accuracy ranged from 112% at 3 ppb to 96% at 200 ppb, with relative standard deviations ranging from 4% at 3 ppb to 2% at 200 ppb.

Immunoconversion against Sarcocystis neurona in normal and dexamethasone-treated horses challenged with S. neurona sporocysts.

Equine protozoal myeloencephalitis is a common neurologic disease of horses in the Americas usually caused by Sarcocystis neurona. To date, the disease has not been induced in horses using characterized sporocysts from Didelphis virginiana, the definitive host. S. neurona sporocysts from 15 naturally infected opossums were fed to horses seronegative for antibodies against S. neurona. Eight horses were given 5x10(5) sporocysts daily for 7 days. Horses were examined for abnormal clinical signs, and blood and cerebrospinal fluid were harvested at intervals for 90 days after the first day of challenge and analyzed both qualitatively (western blot) and quantitatively (anti-17kDa) for anti-S. neurona IgG. Four of the challenged horses were given dexamethasone (0.1mg/kg orally once daily) for the duration of the experiment. All challenged horses immunoconverted against S. neurona in blood within 32 days of challenge and in CSF within 61 days. There was a trend (P = 0.057) for horses given dexamethasone to immunoconvert earlier than horses that were not immunosuppressed. Anti-17kDa was detected in the CSF of all challenged horses by day 61. This response was statistically greater at day 32 in horses given dexamethasone. Control horses remained seronegative throughout the period in which all challenged horses converted. One control horse immunoconverted in blood at day 75 and in CSF at day 89. Signs of neurologic disease were mild to equivocal in challenged horses. Horses given dexamethasone had more severe signs of limb weakness than did horses not given dexamethasone; however, we could not determine whether these signs were due to spinal cord disease or to effects of systemic illness. At necropsy, mild-moderate multifocal gliosis and neurophagia were found histologically in the spinal cords of 7/8 challenged horses. No organisms were seen either in routinely processed sections or by immunohistochemistry. Although neurologic disease comparable to naturally occurring equine protozoal myeloencephalitis (EPM) was not produced, we had clear evidence of an immune response to challenge both systemically and in the CNS. Broad immunosuppression with dexamethasone did not increase the severity of histologic changes in the CNS of challenged horses. Future work must focus on defining the factors that govern progression of inapparent S. neurona infection to EPM.

The effects of different methods of accounting for observations from euthanized animals in survival analysis.

The issue of euthanasia is unique to veterinary clinical studies evaluating survival time. The decision to euthanize an animal is based on several factors including the health of the animal but also age and cost of treatment. The literature shows inconsistent methods used to account for observations from euthanized animals. Also, over 50% and up to 100% of animals in many studies have been euthanized. Our study illustrates the effects of different methods of accounting for observations from euthanized animals in survival analysis. Three data sets with different proportions of outcomes (alive, lost-to-follow-up, dead due to disease of interest, dead due to other disease, euthanized due to disease of interest, euthanized due to other disease) were used. Each data set was stratified according to treatment or a group characteristic (e.g. tumor type). Our methods for accounting for observations from euthanized animals were established from methods used in the literature and included right-censoring. Kaplan-Meier product-limit survival-function estimation was performed on each data set. Different methods resulted in inconsistent conclusions of significant differences between strata. At times, the ranking of the estimates of median survival time for strata was reversed. Right-censoring and use of Kaplan-Meier methods is inappropriate to evaluate observations from euthanized animals because censoring of such observations is informative. The current methods used by clinical investigators are inadequate to measure survival time reliably.

Culling of dairy cows. Part I. Effects of diseases on culling in Finnish Ayrshire cows.

The effects of 15 diseases on time until culling were studied in 39,727 Finnish Ayrshire cows that calved during 1993 and were followed until the next calving or culling. The diseases studied were: dystocia, milk fever, retained placenta, displacement of the abomasum, metritis, non-parturient paresis, ketosis, rumen disorders, acute mastitis, hypomagnesemia, lameness, traumatic reticuloperitonitis, anestrus, ovarian cysts, and teat injuries. Survival analysis, using the Cox proportional hazards model, was performed and diseases were modeled as time-dependent covariates. Different stages of lactation when culling can occur were also considered. Parity, calving season and herd were included as covariates in every model. Parity had a significant effect on culling, the risk of culling being four times higher for a cow in her sixth or higher parity than for a first parity cow. The effects of diseases varied according to when the diseases occurred and when culling occurred. Mastitis, teat injuries and lameness had a significant effect on culling throughout the whole lactation. Anestrus and ovarian cysts had a protective effect against culling at the time when they were diagnosed. In general, diseases affected culling decisions mostly at the time of their occurrence. The effect seemed to decrease with time from the diagnosis of the disease. However, milk fever, dystocia and metritis also had a significant effect on culling at the end of the lactation.

Operation-management factors associated with early-postnatal mortality of US foals.

Of 7320 equine foals reported born alive during 1997 on 1043 operations that had equids on 1 January 1997, and that participated in the United States National Animal Health Monitoring System (NAHMS) Equine 1998 Study, 120 foals were reported to have died (by either euthanasia or natural causes) within the first 2 days of a live birth. The weighted estimate was 1.7% mortality (standard error=0.5) within the first 2 days of live birth for all foals born on operations in the 28 states included in the study.A multivariable logistic-regression model revealed that foals born in the southern region were more likely to have been reported to have died within the first 2 days of live birth than in the western region. In addition, the following operation-level factors were associated with increased odds of a foal dying within the first 2 days of live birth: not routinely testing newborn foals for adequate absorption of colostral immunoglobulins during the first 2 days of life; adding new resident equids to the operation during 1997; having non-resident equids stay on the operation for 1-30 days during 1997; never requiring an official health certificate (for operations that had non-resident equids stay on the operation for 1-30 days); using something other than straw or hay as the predominant bedding type; and feeding equids a vitamin-mineral supplement/premix with forage and/or grain.

Atypical parasitic migration and necrotizing sacral myelitis due to Serratospiculoides amaculata in a prairie falcon (Falco mexicanus).

An adult, wild-caught, female prairie falcon (Falco mexicanus) was presented with the chief complaint of anorexia. Radiographic findings included increased densities within the air sacs, and coelomic endoscopy revealed numerous slender worms within the air sacs and on the serosal surfaces of the ovary, oviduct, liver, proventriculus, and ventriculus. The bird seemed to improve for a short period of time with antiparasitic therapy (ivermectin and fenbendazole) and supportive care. Twenty-one days after initial presentation, the bird became recumbent with increasing pelvic limb neurologic deficits and was euthanized. On histopathologic examination, mature nematodes and larvated eggs identified as Serratospiculoides amaculata were found within the subdural space of the distal thoracolumbar and synsacral spinal cord and within the coelomic cavity. This case suggests that S. amaculata can cause clinically significant lesions in its falconiform host with potentially fatal results.

Hepatocyte vacuolation and autolytic changes in the liver of pilot whales, Globicephala melas, stranded on Cape Cod, MA, USA.

Most cetacea available for internal sampling in recent times have died through mass or single stranding events. It is important to know how the time elapsed between death and sampling affect quality of tissues. This study evaluated histological quality in the liver of long-finned pilot whales that either died or were euthanased after mass stranding events. Histological detection of significant autolysis was found in animals when 2 or more hours elapsed between death and sampling. In addition, hepatocytes often had marked idiopathic cytoplasmic vacuolation that did not stain with hematoxylin and eosin. The extent of this vacuolation did not show any correlation with time between death and sampling, but did appear more often in animals of greater total length. These observations suggest that when animals die or are euthanased at a single or mass stranding, every effort should be made to obtain samples as soon as possible, although meaningful histological observations can still be made in the presence of significant autolysis. These data also suggest that a multi-disciplinary study should be conducted to determine whether increasing autolysis is associated with changes in the organic chemical residues, molecular biology, histopathology and microbiology of those tissues.

Use of injectable potassium chloride for euthanasia of American lobsters (Homarus americanus).

Potassium chloride (KCl: 330 mg/ml) was assessed as an euthanasia agent in American lobsters (Homarus americanus). Two groups of 10 lobsters (408.2 to 849.9 g) were maintained at 11.9 to 12.1 degrees C ('warm') and 1.5 to 2.5 degrees C ('cold') to evaluate the possible effect of ambient temperature on response to KCl. Death was defined as time of cardiac arrest, as viewed and measured by use of ultrasound. The KCl solution was injected (100 mg of KCl/100 g of body weight) at the base of the second walking leg to flood the hemolymph sinus containing the ventral nerve cord with potassium. Disruption of this 'central nervous system' was immediate, followed by cardiac arrest within 60 to 90 seconds. Group median ( +/- SD) baseline heart rate was 42 +/- 14 'warm' and 36 +/- 5 'cold' beats per minute. Time until cardiac arrest ranged from 35 to 90 (57 +/- 18) seconds in the 'warm' group and from 40 to 132 (53 +/- 34) seconds in the 'cold' group. There was no significant difference between group medians for either parameter. Histologic lesions were limited to mild to moderate acute degeneration, characterized by cell swelling, loss of contraction bands, and occasional mild cytoplasmic vacuolation of skeletal muscle at the injection site. Injectable KCl solution was an effective, reliable method for euthanasia of H. americanus.

Modification of immunologic and hematologic variables by method of CO2 euthanasia.

BACKGROUND AND PURPOSE: The major goal was to determine whether variations in the method of CO2 euthanasia would induce significant immunologic differences. METHODS: Young adult C57BL/6 mice (n = 40) were euthanized, using four regimens: 70% CO2/30% O2; 70% CO2/30% O2-->100% CO2; 100% CO2-naïve chamber; and 100% CO2 pre-charged chamber. Time to recumbency and euthanasia and body, liver, lung, spleen, and thymus masses were determined. Blood and spleen were further evaluated for leukocyte, lymphocyte, and thrombocyte counts, erythrocyte characteristics, distribution of lymphocyte subpopulations, spontaneous and mitogen-induced blastogenesis, complement activity, and cytokine production. RESULTS: Time to euthanasia was five- to eightfold longer in mice exposed to 70% CO2/30% O2 than that for any other group. There were slight increases in mean erythrocyte volume (MCV) and mean erythrocyte hemoglobin (MCH) for all groups, compared with those for the 100% CO2 pre-charged group. Circulating cytotoxic T (CD8+) lymphocyte percentages and numbers, and spontaneous blastogenesis of leukocytes in blood and spleen, also were affected by euthanasia method. CONCLUSIONS: The method of CO2 euthanasia can result in significant differences in immunologic/hematologic variables. Thus, consistency in euthanasia procedures may be important in accurate interpretation of research data.

Ethanol euthanasia and its effect on the binding of antibody generated against an immunogenic peptide construct.

Mice were immunised with an immunogenic peptide construct CKNNNSTNSGI coupled to diphtheria toxoid as a carrier. This peptide sequence contains the epitope STNS which is the target of inhibitory monoclonal antibodies directed against the second merozoite surface antigen of Plasmodium falciparum. Antisera raised against the peptide construct were taken using an injection of 70 per cent ethanol or sodium pentobarbitone as methods of euthanasia and these methods compared by determining their effects on the binding specificity of the antibody to the antigen using the immunological criteria of immunofluorescence, immunoblotting criteria of immunofluorescence, immunoblotting and ELISA assays. There was no significant decrease in antibody binding with either sodium pentobarbitone, or ethanol with a final concentration of less than 30 per cent in mouse antisera. Antisera with an added ethanol concentration of 40 to 60 per cent relaxed antibody conformation and this raises the possibility of using the differential effects of ethanol as a tool in mapping antigenic fine structure of a range of antibodies directed against defined epitopes. The cross-reactive response of non-specific antibodies in polyclonal antisera was lowered at the suggested dosage for ethanol euthanasia. Ethanol has immense potential as an alternative method of euthanasia when barbiturate drugs, such as sodium pentobarbitone, are unavailable in specific experimental protocols. This may especially aid research workers in developing countries involved in vaccine development, antibody production and subsequent serological analysis.

The importance of immediate destruction in epidemics of foot and mouth disease.

Foot and mouth disease is still prevalent in many parts of the world, as emphasised by the recent devastating epidemic in pig farms in Taiwan. A discrete time mechanistic model has been used to describe the spread of infection in both this epidemic and the 1967 to 1968 epidemic in the UK. The force of infection and basic reproduction number are estimated and the sensitivity of these results to the distributions of both the latent and infectious periods of the disease is examined. Epidemic simulations were performed to evaluate the disease control policy whereby all herds are slaughtered on the same day as disease confirmation. These simulations showed that implementing this policy could have resulted in a dramatic reduction (of over 60 per cent) in the number of pig farms affected in the Taiwan epidemic. It is thus imperative that the necessary resources are available to implement this policy, should an outbreak occur.

Cardiovascular effects of thoracic compression in horses subjected to euthanasia.

Six horses scheduled for euthanasia were instrumented for the measurement of blood flow by thermodilution, pulmonary arterial, right atrial and arterial blood pressures and collection of arterial blood for pH and blood gas analysis. The horses were anaesthetised with intravenous (iv) thiamylal sodium (10 mg/kg) and placed in right lateral recumbency. After euthanasia with an overdose of pentobarbitone sodium (100 mg/kg, iv) and loss of the electrocardiogram and arterial pulse pressure, thoracic compression at rates of 40, 60 and 80 compressions/min was instituted. Thoracic compression was accomplished by an investigator who delivered a blow to the chest wall with his knee while dropping from a standing or crouching position. Compression rates of 40, 60 and 80/min produced blood flows of 5.65 +/- 0.5, 6.33 +/- 1.11 and 8.28 +/- 2.16 litres/min, respectively. Compression rates of 80/min produced significantly (P < 0.05) greater blood flows and mean arterial blood pressures than did slower rates. The blood flows produced by 80 thoracic compressions/min were approximately 50% of those reported for deeply anaesthetised horses and while not sufficient to sustain life might be used to prolong life in order to facilitate distribution of resuscitative drugs to vital tissues.

Surgical treatment of 45 horses affected by squamous cell carcinoma of the penis and prepuce.

The medical records of 45 horses treated for suspected squamous cell carcinoma of the penis and/or prepuce were reviewed. The age of 40 horses was known, and these had a mean age of 17.4 years. The duration of neoplasia was known for only 3 of the 45 horses. The results of histological evaluation of lesions, available for 35 horses, confirmed that the diseased tissue was squamous cell carcinoma. The location of gross neoplastic lesions was recorded for 43 horses; the glans penis was involved in 24 horses, the body of the penis or the inner lamina of the preputial fold in 27 horses, and the external fold of the prepuce in 10 horses. Surgical treatments of these horses included phallectomy (penile amputation) in 35 horses, segmental posthectomy in 4 horses, phallectomy plus segmental posthectomy in 2 horses, and en bloc resection of the penis, prepuce and superficial inguinal lymph nodes with penile retroversion in 4 cases. Short-term complications in the immediate postoperative period included preputial oedema and haemorrhage at the end of urination. One horse developed acute urinary retention because of severe urethral oedema. Long-term (>1 year) follow-up information was obtained for 31 horses. Neoplasia of the penis and/or prepuce recurred in 6 of these 31 horses (19%), and in 5 of these the recurrence necessitated euthanasia of the horse.

Confidential enquiry of perioperative equine fatalities (CEPEF-1): preliminary results.

The Confidential Enquiry into Perioperative Equine Fatalities (CEPEF-1) is an observational multi-institutional prospective study of recovery outcome at 7 days post operatively, as called for by Steffey (1991). Data from 6,255 general anaesthetics (February 91-March 93) were submitted confidentially by 62 clinics. The outcomes of 333 cases which were subjected to euthanasia and which were not classified 'alive' or 'died' at 7 days, were excluded from the analysis. The remaining 5922 cases were analysed to identify risk ratios (RR) between survivors and nonsurvivors for a variety of factors. These preliminary results indicate an overall death rate, for equine patients dying or being subjected to euthanasia within 7 days of a general anaesthetic because of perioperative complications, of 102/6255 (1.6%). This mortality rate decreased to 46/5220 (0.9%) when all colic surgery and delivery of foals under general anaesthesia were excluded. There was an increased risk for mares in the last trimester of pregnancy (RR = 6.4). Patients undergoing emergency abdominal procedures (colic patients and pregnant mares undergoing controlled or caesarean section delivery of foals) under general anaesthesia were at increased risk (RR = 12.9) compared to ear, nose and throat surgery. Within orthopaedic surgery, patients requiring internal fixation were at increased risk (RR = 3.2) compared to those undergoing miscellaneous orthopaedic surgery. There was no difference in risk between breeds. Patients not placed in dorsal recumbency were at reduced risk (RR = 0.3-0.5) compared to those which were in dorsal recumbency.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaemia, diarrhoea and opportunistic infections in Fell ponies.

This report summarises clinical and pathological observations on Fell pony foals with a range of signs that included ill thrift, anaemia, respiratory infection, glossal hyperkeratosis and diarrhoea. Some of the foals had normochromic, normocytic anaemia and some had low levels of plasma proteins, including immunoglobulin G. Antibiotic and supportive treatment was ineffective and all affected foals died or were killed on humane grounds. Postmortem examination of 12 foals and tissues from 2 other foals revealed a range of lesions that included glossal hyperkeratosis, typhlocolitis, intestinal cryptosporidiosis, granulomatous enteritis, proliferative and necrotising bronchiolitis consistent with adenovirus infection; lesions similar to those in the respiratory tract were present in the salivary gland and pancreas of individual foals. Lymphoid tissue was judged to be smaller than expected. These observations suggest the possibility of opportunistic infections secondary to some form of undefined immunocompromised state.

Peripheral neuroblastoma and primitive neuroectodermal tumor in Japanese black cattle.

Peripheral neuroblastoma was found in a 1-year-old, male, Japanese black cattle (Case 1) and primitive neuroectodermal tumor was noted in 7-year-old, female, Japanese black cattle (Case 2). In Case 1, neoplastic tissue was replaced the right cranial vault and nasopharynx. A large, soft mass approximately 18 cm in diameter was also observed in the right mandibulopharyngeal area. In Case 2, a neoplastic mass of about 15 cm in diameter was found in the mandibulopharyngeal area. Histopathologically, massive necrosis showing a pseudopalisade arrangement was frequently observed in Case 1. On the contrary, Homer & Wright rosette formations of tumor cells were prominent in Case 2. Immunohistochemically, the proliferating cells in Case 1 were positive for vimentin, S-100, and neurofilament (NF) and those in Case 2 showed intense immunoreactivity for NF and neuron specific enolase, but were negative for vimentin and S-100. The different degrees of differentiation of the neoplastic cells originating from the neuroectoderm, might be reflected in their different morphological and immunohistochemical features.

Canine mesenchymal chondrosarcoma of the ribs.

The tumor of the thoracic cavity, which arose from the ribs, was diagnosed as mesenchymal chondrosarcoma. No distant metastasis was observed. Histologically, the tumor was characterized by the nests of well-defined cartilaginous tissue within a proliferation of primitive mesenchymal cells. Additionally, the deformed blood vessels compressed by the proliferating mesenchymal cells exhibited clear stag-horn appearance. Immunohistochemically, most neoplastic cells that formed multifocal cartilaginous islands were positive for S-100 protein, while the surrounding mesenchymal cells were negative. This is the first report of canine mesenchymal chondrosarcoma of the ribs.