Transmission of classical swine fever virus within herds during the 1997-1998 epidemic in The Netherlands

In this paper, we describe the transmission of Classical Swine Fever virus (CSF virus) within herds during the 1997–1998 epidemic in the Netherlands. In seven herds where the infection started among individually housed breeding stock, all breeding pigs had been tested for antibodies to CSF virus shortly before depopulation. Based upon these data, the transmission of CSF virus between pigs was described as exponential growth in time with a parameter r, that was estimated at 0.108 (95% confidence interval (95% CI) 0.060–0.156). The accompanying per-generation transmission (expressed as the basic reproduction ratio, R₀) was estimated at 2.9. Based upon this characterisation, a calculation method was derived with which serological findings at depopulation can be used to calculate the period in which the virus was with a certain probability introduced into that breeding stock. This model was used to estimate the period when the virus had been introduced into 34 herds where the infection started in the breeding section. Of these herds, only a single contact with a herd previously infected had been traced. However, in contrast with the seven previously mentioned herds, only a sample of the breeding pigs had been tested before depopulation (as was the common procedure during the epidemic). The observed number of days between the single contact with an infected herd and the day of sampling of these 34 herds fitted well in the model. Thus, we concluded that the model and transmission parameter was in agreement with the transmission between breeding pigs in these herds.

Because of the limited sample size and because it was usually unknown in which specific pen the infection started, we were unable to estimate transmission parameters for weaned piglets and finishing pigs from the data collected during the epidemic. However, from the results of controlled experiments in which R₀ was estimated as 81 between weaned piglets and 14 between heavy finishing pigs (Laevens et al., 1998a. Vet. Quart. 20, 41–45; Laevens et al., 1999. Ph.D. Thesis), we constructed a simple model to describe the transmission of CSF virus in compartments (rooms) housing finishing pigs and weaned piglets. From the number of pens per compartment, the number of pigs per pen, the numbers of pigs tested for antibodies to CSF virus and the distribution of the seropositive pigs in the compartment, this model gives again a period in which the virus most probably entered the herd. Using the findings in 41 herds where the infection started in the section of the finishers or weaned piglets of the age of 8 weeks or older, and of which only a single contact with a herd previously infected was known, there was no reason to reject the model. Thus, we concluded that the transmission between weaned piglets and finishing pigs during the epidemic was not significantly different from the transmission observed in the experiments.     

Quantification of the transmission of classical swine fever virus between herds during the 1997-1998 epidemic in The Netherlands

In this study, we describe a method to quantify the transmission of Classical Swine Fever Virus (CSFV) between herds from data collected during the 1997–1998 epidemic in the Netherlands. From the contacts between infected herds and the serological findings shortly before depopulation, we estimated the week of virus introduction and the length of the period over which the herd emitted virus for each CSFV-infected herd. From these data, we estimated the infection-rate parameter β (the average number of herds infected by one infectious herd during one week) and the herd reproduction ratio, R_h (the average total number of secondary outbreaks caused by one infectious herd, i.e. in its entire infectious period), using a SIR-model for different sets of CSF control measures. When R_h > 1, an epidemic continues to grow. On the other hand, when R_h < 1 an epidemic will fade out.

During the phase before the first outbreak was diagnosed and no specific measures had been implemented, β was estimated at 1.09 and R_h at 6.8. In the subsequent phase infected herds were depopulated, movement restrictions were implemented, infected herds were traced forward and backward and the herds in the protection and surveillance zones were clinically inspected by the veterinary authorities (regional screening). This set of measures significantly reduced β to 0.38. However, R_h was 1.3 and thus still >1. Consequently, the number of outbreaks continued to grow. After a number of additional measures were implemented, the value of R_h was reduced to 0.5 and the epidemic came to an end. These measures included pre-emptive slaughter of herds that had been in contact with infected herds or were located near an infected herd, increased hygienic procedures, replacement of transports of pigs for welfare reasons by killing of young piglets and a breeding ban, and regional screening for CSF-infected herds by local veterinary practitioners.     

Effect of day and night temperatures during long photoperiods on the vegetative growth and flowering of Chrysanthemum morifolium Ramat

The influence of day and night temperatures in the range of 10–17°C on the vegetative growth under long days of 17 year-round cultivars of chrysanthemum was studied. The after-effect of the temperature regime on the time of flowering at 17°C under short days was also recorded.A decrease of the day or night temperature reduced growth, but the effect of the day temperature was much stronger than that of the night temperature. The temperature during the vegetative period had hardly any effect on the time of flowering at 17°C.The consequences for production and breeding are discussed.     

Use of clomipramine,alprazolam, and behavior modification for treatment of storm phobia in dogs

OBJECTIVE: To evaluate use of clomipramine, alprazolam, and behavior modification for treatment of storm phobia in dogs. DESIGN: Prospective open clinical trial. ANIMALS: 40 dogs with storm phobia. PROCEDURE: Dogs received clomipramine at a dosage of 2 mg/kg (0.9 mg/lb), PO, every 12 hours for 3 months; then 1 mg/kg (0.45 mg/lb), PO, every 12 hours for 2 weeks; then 0.5 mg/kg (0.23 mg/lb), PO, every 12 hours for 2 weeks. Alprazolam was given at a dosage of 0.02 mg/kg (0.009 mg/lb), PO, as needed 1 hour before anticipated storms and every 4 hours as needed. Desensitization and counter-conditioning were conducted at home by the caregiver with an audio simulation of storm sounds that had induced a fear response during evaluation. RESULTS: 30 of the 32 dogs that completed the study had a degree of improvement, as measured by caregivers' global assessment. Two caregivers considered the storm phobia to be resolved. Panting, pacing, trembling, remaining near the caregiver, hiding, excessive salivation, destructiveness, excessive vocalization, self-trauma, and inappropriate elimination all decreased significantly during treatment. Improvement was greater during true storms (rain, thunder, and lightning) than during rain only. Response to audio simulation did not change during treatment. Four months after the study, improvement was maintained. CONCLUSIONS AND CLINICAL RELEVANCE: The combination of clomipramine, alprazolam, and behavior modification can be effective in decreasing or eliminating storm phobia. Improvement could not be evaluated by use of audio simulation of a storm.     

A review of porcine reproductive and respiratory syndrome virus in Dutch breeding herds: population dynamics and clinical relevance

Understanding the spread of porcine reproductive and respiratory syndrome virus (PRRSV) in pig populations is essential to the development of effective PRRS prevention and control strategies. Moreover, knowledge of the field dynamics of PRRSV in pigs will provide insights into the clinical relevance of PRRS, and will enable the targeting of interventions. This review of PRRSV includes discussion on the occurrence of outbreaks, the persistence of infection and the fade-out of infection in Dutch breeding herds. The dynamic character of PRRSV infections in endemically infected herds and the relevance of the disease under Dutch field conditions are also highlighted. Furthermore, several strategies aimed at controlling the spread of PRRSV are discussed.     

Experimental vascular graft for liver transplantation

Hepatic artery thrombosis is a major cause of graft failure in liver transplantation. Use of donor interponates are common, but results are controversial because of necrosis or thrombosis after rejection. Reperfusion injury, hypoxia and free radical production determinate the survival. The aim of the study was to create an 'ideal' arterial interponate. Autologous, tubular graft lined with mesothelial cells, prepared from the posterior rectus fascia sheath, was used for iliac artery replacement in eight mongrel dogs for six months under immunosuppression. Patency rate was followed by Doppler ultrasound. Eight grafts remained patent and another two are patent after one year. The patency rate was good (median Doppler flow: 370 cm/sec) and there was no necrosis, thrombosis or aneurysmatic formation. The grafts showed viable morphology with neoangiogenesis, appearance of elastin, smooth muscle and endothelial cells. Electron microscopy showed intact mitochondrial structures without signs of hypoxia. Tissue oxygenation was good in all cases with normal (< 30 ng/ml) myeloperoxidase production. In conclusion, this autologous graft presents good long-term patency rate. Viability, arterialisation and low thrombogenicity are prognostic factors indicating usability of the graft in the clinical practice without the risk of rejection. Further investigations such as cell cultures and standardisation are necessary.     

Effects of restricted feeding on physiological stress parameters in growing broiler breeders

1. In previous studies, a lack of agreement in measurements of plasma corticosterone concentrations and heterophil:lymphocyte (H/L) ratio as physiological indices of stress, caused by hunger and frustration in restricted-fed broiler breeders, was observed. It could be suggested that the differences between previous studies were caused by differences in duration of restriction and time of the day of the measurements. Therefore, in the present study the plasma corticosterone concentration and the H/L ratio were again determined in restricted- and ad libitum-fed growing broiler breeders, taking possible causes of disagreement between previous studies into account. In addition, we measured the daily rhythm in body temperature and heart rate, and the corticosterone responses to an acute stressor as physiological indices of stress. 2. Female broiler breeders (64 per treatment, housed in groups of 4 birds) were used in the experiment. Behaviour, baseline plasma corticosterone concentrations and H/L ratio were determined at 21 d of age (immediately after the start of food restriction), and at 42 and 63 d of age. Body temperature, heart rate and activity were measured by radiotelemetry for 36 h at 49 and 70 d of age. In addition, the plasma corticosterone response to acute stress (5 min manual restraint) was measured at 77 or 78 d of age. 3. Restricted broiler breeders had higher plasma corticosterone concentrations at 42 and 63 d of age, but no differences in H/L. ratio were found between restricted birds and unrestricted control birds. Restricted broiler breeders had a higher corticosterone response to 5 min manual restraint than unrestricted birds. Restricted birds displayed a clear day-night rhythm in body temperature, heart rate and activity whereas such a rhythm was blunted in ad libitum-fed birds. 4. It is discussed that some physiological differences (plasma corticosterone concentrations, body temperature and heart rate) between ad libitum-fed and restricted broiler breeders may have been caused by differences in metabolic rate as well as by differences in the level of stress. It is concluded that a combination of behavioural measurements and a wide range of physiological parameters should be used for the assessment of stress in growing broiler breeders.     

Recent increase of Marek's disease in Korea related to the virulence increase of the virus

The incidence of Marek's disease (MD), an important neoplastic disease of chickens, suddenly increased in 1997 in Korea. Most MD cases of this country were detected in chickens over 20 wk of age. Five MD viruses were isolated from field flocks in which severe MD losses had occurred, and one of the viruses was studied to compare its pathotype with the prototype JM strain. The isolate KOMD-IC induced severe depression not only in body weight but also in relative bursal weight, and the depression by KOMD-IC was more severe than that induced by JM strain. In addition, the incidence of MD tumor caused by KOMD-IC was higher than that caused by the JM strain. The protective capacity of several MD vaccines was studied against challenge with KOMD-IC. The protective levels of several MD vaccines such as herpesvirus of turkeys (HVT), HVT plus SB1, and Rispens were usually lower against challenge with KOMD-IC than those challenged with JM strain, even if the chickens vaccinated with serotype 1 were not completely protected against challenge with KOMD-IC. The above results indicate that the virulence of KOMD-IC isolated recently was increased, and the increase of MD outbreak in Korea may be related to the virulence increase of the virus. Various MD vaccine programs were applied to reduce MD loss to a broiler breeder farm where severe MD loss had occurred. Serotype 1 vaccine could dramatically decrease the mortality due to MD, and the best results were obtained from the flocks vaccinated with bivalent vaccine of Rispens and HVT.     

Dermal pharmacokinetics of the insecticide furathiocarb in rats

The pharmacokinetics of furathiocarb were studied in vivo in male Sprague-Dawley rats following dermal treatment. HPLC and post-column derivatization were used for the analysis of furathiocarb and its metabolites (carbofuran, 3-hydroxycarbofuran and 3-ketocarbofuran). Carbofuran and 3-hydroxycarbofuran were detected in plasma and urine rather than furathiocarb. 3-Ketocarbofuran, another potential metabolite, was not observed in any sample. The concentration of carbofuran was higher than that of 3-hydroxycarbofuran in plasma, but the reverse was the case in urine. The corresponding area under the plasma concentration-time curve, Tmax, and Cmax values of carbofuran and 3-hydroxycarbofuran for 1500 mg kg-1 doses were 2.4-8.0 mg equiv hml-1, 12 h and 0.1-0.4 mg equiv ml-1, respectively. T1/2 was calculated only for 3-hydroxycarbofuran (28 h). Two metabolites were excreted in a dose-dependent manner without saturation.     

Disseminated transmissible venereal tumor in a dog.

Transmissible venereal tumor (TVT) is a well-documented transplantable tumor in dogs, with no breed or sex predilection and a low metastatic rate. In this report, a 2-year-old intact female Mastiff that had numerous, rapidly growing masses throughout the subcutis mainly at the dorsal body plane, the caudal half of the ventral abdomen, and around the vulva was euthanized due to poor prognosis. Neoplastic nodules similar to those seen in the subcutis were also noted in the lung, anterior mediastinum, liver, spleen, kidney, and superficial and deep lymph nodes in both abdominal and thoracic cavities. The neoplastic nodules from the subcutis as well as metastatic foci revealed similar cytologic and histologic features, which were consistent with canine TVT. By immunohistochemical staining, the neoplastic cells were positive for lysozyme and vimentin but were negative for cytokeratin, desmin, CD3, and CD79a. The diagnosis of the TVT was further supported by the identification and analysis of long interspersed nuclear elements (LINE) from paraffin-embedded tumor tissue. This case is a rare example of TVT with multiorgan metastasis. In this case, the polymerase chain reaction technique was useful in differential diagnosis of canine round cell tumors because this technique can be applied in retrospective as well as future study.