Evaluation of Ziehl-Neelsen stained faecal smear and ELISA as tools for surveillance of clinical paratuberculosis in cattle in the Netherlands

Testing cattle suspected of clinical paratuberculosis is an important element of surveillance of paratuberculosis. The aim of this study was to evaluate the diagnostic-test characteristics of microscopic examination of Ziehl-Neelsen stained faecal smears for acid-fast Mycobacteria (ZN-test) and serum-ELISA in cattle suspected of clinical paratuberculosis in the Netherlands. Results of all samples submitted for ZN-test and serum-ELISA between April 2003 and April 2006 to our laboratory were retrieved. Results from cattle for which both tests were performed were analysed using two Bayesian latent-class models for evaluation of diagnostic tests in two populations without a gold standard, assuming (a) conditional independence of tests, or (b) conditional dependence of tests in both infected and non-infected cattle. Sampled cattle were divided into two populations in different ways using four known risk factors for clinical paratuberculosis: region, soil type, clinical signs, and age. For 892 cattle suspected of clinical paratuberculosis, both ZN-test and serum-ELISA results were retrieved: 250 ZN-positive and ELISA-positive, 12 ZN-positive and ELISA-negative, 260 ZN-negative and ELISA-positive, and 370 ZN-negative and ELISA-negative cattle. With priors based on the available literature, the posterior estimates of sensitivity, specificity, and positive and negative predictive values of the ELISA were always higher than those of the ZN-test. Furthermore, lower limits of the 95% credibility intervals of the posterior positive predictive values of the ELISA were >or=99.7%, and of the negative predictive values of the ELISA >or=56.4%. We conclude that the ELISA is preferred to the ZN-test to confirm the presumptive diagnosis of clinical paratuberculosis in the Netherlands. Little diagnostic information can be gained by performing the ZN-test in addition to the ELISA.

[Four milk cows dead by electrocution]

Two dairy cows were found dead in their cubicles and a third was found lying dazed in a stall but the animal stood up 5 minutes later. Two days later; two other cows were found dead in the same row of cubicles. Death was due to electrocution caused by an electric wire in a steel pipe connected to front of the cubicles. Post-mortem findings supported this diagnosis.

Nitrogen dioxide (silo gas) poisoning in dairy cattle

Toxic silo gases are a potential danger to livestock housed in close proximity to roughage silos. These gases, such as nitrogen dioxide (NO2), may be produced during the early stages of (maize and grass) silage making. In humans, inhalation of these gases causes a condition known as 'Silo Filler's Disease' (SFD), which is a recognized occupational hazard for workers in upright forage silos in many countries. NO2 accumulates on top of silage, is inhaled by workers, and reacts with water on the airway surfaces to form nitrous acid, which damages the lung and causes pulmonary oedema, bronchiolitis, and death in severe cases. On a dairy farm, a cloud of reddish-brown NO2 gas (which is heavier than air) was noticed to escape from underneath the plastic sheet of a horizontal maize bunker and to enter a cubicle house for dairy cows 1 day after ensiling. Eleven cows became dyspnoeic, 3 of which subsequently died. A combination of weather conditions, an insufficient sand load on the maize bunker, the utilization of a lactobacillus starter culture, and the close proximity of the silo to the cubicle house may have caused the incident.

Assessing the repeatability and reproducibility of the Leg Score: a Dutch Claw Health Scoring System for dairy cattle

The optimal moment for trimming the claws of all dairy cows in a herd was investigated by assessing the external rotation of the hind claws of individual cows relative to the spinal column. This leg score consisted of three independent descriptors: 1 (good/normal), 2 (moderately deviant), and 3 (severely deviant). This study assessed the repeatability and the reproducibility of the leg score system, and the consistency of the advice given subsequently about trimming of the hind claws of all cows in the herd. Repeatability was assessed for 52 cows that were scored twice on the same day by 11 observers; the kappa value ranged from 0.17 to 0.66 (mean: 0.36). The probability of the same result for both assessments ranged from 0.49 to 0.80 (mean: 0.61). Claw trimming was advised if at least 20% of the cows had a leg score of 3. On the basis of the scores, 3 observers consistently advised trimming of the hind claws of all the cows in the herd, and 6 observers consistently advised against the need for trimming in the short term; 2 observers had an inconsistent advice. The reproducibility of the scoring system was assessed in two dairy herds (62 and 50 cows). Eight observers evaluated the leg score of the cows of both herds on the same day. The mean kappa value of the leg score for all pairs of different observers (A-B, A-C etcetera) was 0.24 [-0.08-0.49]. In conclusion, the leg score is not a reliable method for determining the optimal moment for claw trimming in dairy cattle. The reasons for the inconsistent observations require further investigation.

[Lungworm disease in dairy cattle: symptoms, diagnosis, and pathogenesis on the basis of four case reports]

Clinical lungworm disease appears to occur frequently in Dutch dairy herds. Because the clinical diagnosis is difficult to make in adult cattle, the clinical diagnosis, laboratory diagnosis, differential diagnosis, therapy, and prevention are discussed in this article. In addition, four cases of lungworm disease in adult cattle are presented. The main clinical complaints were coughing, decreased milk production, and weight loss. Several lactating cows died in one herd. The disease history of four herds revealed that introduction of susceptible cows or heifers to herds with cows with subclinical patent lungworm infections had resulted in a pasture infection, leading to clinical problems in both the newly introduced and 'resident' cows of the herd. Further history analysis of the fourth herd revealed that re-introduction of lungworm infection by newly purchased cows in a lungworm free herd resulted in clinical lungworm problems in adult and young animals. The fourth case led to the conclusion that lungworm infection must have been re-introduced by cows purchased from another farm.

Herd-level diagnosis for Salmonella enterica subsp. enterica serovar Dublin infection in bovine dairy herds

Herd-level sensitivities of bacteriological and serological methods were compared in 79 bovine dairy herds, recently infected with Salmonella enterica subsp. enterica serovar Dublin. All farms experienced clinical signs of salmonellosis for the first time and had no history of vaccination against salmonellosis. At the start of the study, infection with serovar Dublin was confirmed with at least one positive bacteriologic culture for serovar Dublin from a clinical case (gold standard for herd infection). Bacteriological culture was done on samples of dung-pits, drinking water, bulk-milk filters, and faeces of animals with current or earlier clinical signs of salmonellosis. Blood samples of all animals and bulk-milk samples were tested using an ELISA.Herd-level sensitivity (HSe) of culture of dung-pits, drinking water, bulk-milk filters, and faeces of animals with current or earlier signs of salmonellosis was 45, 5, 7, and 38%, respectively. HSe for serology of all animals was 100%. If blood samples of all calves 4-6 months old were examined, at least one calf was seropositive on 91% of the infected farms. If serology was performed on samples of animals with current or earlier signs of salmonellosis, at least one animal was seropositive on 80% of the infected farms. HSe for bulk-milk samples was 54%. However, if clinical signs of salmonellosis were observed only in lactating animals, sensitivity of bulk-milk serology was 79%. Interesting combinations of methods were the combination of serology of bulk milk with either serology of animals with current or earlier signs of salmonellosis (HSe=91%), or serology of all calves of 4-6 months old (HSe=99%).

Control of VTEC in Dutch livestock and meat production

The Dutch government and the meat industry, recognising VTEC as having important public health, meat quality and economic implications, have taken a number of initiatives within the last 5 years to control VTEC in livestock and meat. These initiatives, brought together last year in a 'Masterplan VTEC', include short-, middle- and long-term priorities. Short-term priorities include advice on interventions in the cases of an outbreak of VTEC associated with a cattle herd, the implementation of handbooks for Good Manufacturing Practice (GMP) in slaughterhouses and deboning plants, and the execution of an action programme on zero-tolerance to faecal contamination of carcasses. Mid-term activities include surveillance of the occurrence of VTEC and other enteropathogens in livestock and meat, and the investigations of VTEC population dynamics in dairy farms, transportation and farm hygiene. In the longer term, this programme aims to produce a system of Integrated Quality Assurance, consolidating effective measures to control VTEC in Dutch livestock and meat, and integrating emerging means for control and prevention.

[Integrated disease control in dairy herds. A case study from the veterinarians' viewpoint]

Integrated control of bovine virus diarrhoea virus, bovine herpesvirus-1, Leptospira interrogans serovar hardjo subtype hardjobovis, Mycobacterium avium subsp. paratuberculosis, and Salmonella dublin in dairy herds may provide economic benefits superior to those obtained by sequential disease control, because, among other things, it allows optimization of voluntary culling. However, in practice there are no adequate instruments to establish priorities in voluntary culling. Therefore, in this study the priorities in decision-making for voluntary culling of infected cattle, as indicated by more than 300 cattle veterinarians, were analysed. Based on our results and supplementary considerations, the priorities for voluntary culling in the Netherlands can be ranked as: 1st. cull S. dublin carriers, 2nd. cull persistently infected BVDV carriers, 3rd. cull paratuberculosis faecal culture positive cattle and their last offspring, 4th. cull, in paratuberculosis infected herds, paratuberculosis ELISA positive cattle and their last offspring and cull, in low prevalence herds, BHV1 gE-positive cattle, and 5th. cull leptospirosis seropositive cattle. Since this ranking was based on one case study only, other priorities may prevail in other herds.

[Vitamin B12 supplementation and milk production on farms with 'chronic wasting' cattle]

From early 1999 onwards, cattle health problems accompanied by chronic wasting of unknown aetiology were reported on a number of dairy farms. An association between these health problems and the compulsory use of gE-negative marker vaccines against bovine herpesvirus 1 was presumed by farmers. On one dairy farm an increased milk production of 50% was reported within a few days after parenteral vitamin B12 treatment. Therefore, the current study was designed to determine the effect of parenteral vitamin B12 treatment on the milk production of dairy herds with wasting cattle. A randomized blind trial was performed in five problem herds and two control herds. On each farm five lactating cows were injected intramuscularly with 20 mg vitamin B12 and paired with five untreated lactating cows. The milk production of treated and untreated animals was measured for 19 days following treatment and compared to pre-treatment production. No effect of vitamin B12 treatment on milk production was established on either problem farms or control farms. Neither was a difference detected in the response to vitamin B12 treatment between problem herds and control herds. In a second experiment, parenteral vitamin B12 treatment was applied in three problem herds by local veterinary practitioners. The results of this experiment were in line with the results of the first experiment.

[Possibilities for further research of chronic wasting in dairy cows]

In this study, we reviewed the research that has been conducted in relationship with the problem of 'chronic wasting' in dairy cows in the Netherlands as was experienced during 1998 and 1999. Emphasis was drawn towards three aspects of this 'chronic wasting'; the definition, the magnitude, and the possible cause or causes. It appeared that a clear, objective definition of 'chronic wasting' in cows, and of farms with a problem of 'chronic wasting' cows is still lacking. Furthermore, the incidence (of the problem) was restricted to approximately 150 dairy farms at most. Currently, no farms with 'chronic wasting' cows are known. Combined with the uncertainty in the definition, this will hamper future research. Many of the studies were related to the hypothesis that the vaccination with the BHV1 marker vaccine had caused 'chronic wasting' in the cows. None of the results, however, substantiated this hypothesis. Other possible causes have hardly been investigated and further research would be needed to evaluate the role of nutrition, infectious agents, and genetics. However, due to the waning of the phenomenon, the availability of data and controls will be limiting.

[Prevalence of chronic wasting in Dutch dairy herds with a history of chronic health problems]

The prevalence of chronic wasting in cattle in March and April 2000 was studied on 218 dairy farms with a history of health problems accompanied by wasting, following reports in the media suggesting that chronic wasting was a substantial problem on Dutch dairy farms. A telephone call revealed that the health problems had resolved on 41 farms; 16 of these farms had culled all cattle. Two farmers refused co-operation. On the remaining 175 farms the animals were inspected and was completed a questionnaire. A high percentage of culling for of health reasons (on average 18.1% of young stock and adult cattle) and an increased mortality rate (4.8%) were reported on the farms visited. In only two of the 175 inspected herds, more than 20 percent of cattle were found showing signs of wasting. These two herds were identified as 'chronic wasting herds'. The prevalence of such herds was low in this study. Consequently, it is likely that there were very few 'chronic wasting herds' among the whole Dutch dairy population in March/April 2000.

Dutch paratuberculosis programme history, principles and development

Organised disease control started in the Netherlands in the 18th century with governmental attempts to eradicate cattle plague. At the beginning of the 20th century, the dairy industry and cattle breeding organisations initiated a programme to control infectious diseases by means of a complex system of rewards and penalties. This was also the reason for establishing the Animal Health Service in Friesland in 1919. The history of programmes to control paratuberculosis in sheep, goats, and cattle in various countries is described. The vaccination of young animals seems to be an effective measure in the prevention of clinical paratuberculosis, although changes in management and hygiene practices are also important. A control programme for infectious cattle diseases has a number of phases (a lifecycle) and different components. Two components are essential for success, namely: open and regular communication with farmers, veterinary practitioners, and other people involved and a good registration and identification system for cattle, herds, and veterinary practitioners. The Dutch paratuberculosis programme has 10 herd status levels: 5-10 for non-suspect herds and 1-4 for infected herds or herds of unknown status. The higher the status, the greater the chance that a herd is free of paratuberculosis. An outline is given of the Dutch paratuberculosis programme including its objectives, basic principles for eradication, communication plan, legal action, logistic considerations, and complementary research programme.

[Identification of an introduced bovine herpesvirus type 1 strain in a closed dairy herd by experimental virus reactivation followed by DNA restriction enzyme analysis]

In a closed dairy herd in the province of Utrecht in 1995, nine replacement heifers were erroneously intramuscularly vaccinated with Tracherine, a live virus IBR vaccine. More than 18 months later, serology of the herd revealed that a large part of the herd had developed an antibody response towards BHV1 (62 of 87 animals). To investigate whether Tracherine had recirculated on the farm, four BHV1 antibody positive animals, of which two had been vaccinated with Tracherine, were treated with corticosteroids to reactivate latent BHV1. Two virus isolates were obtained and subsequently analysed by resctriction enzyme analysis. Both isolates were identified as BHV1.1 subtypes. One of the isolates was clearly distinct from Tracherine and was most likely a BHV1 field virus. A BHV1 field virus was most likely introduced into the farm even though the herd was closed, the animals had not been in contact with other cattle, and preventive hygienic measures had been implemented. There was no indication that Tracherine had recirculated.

An epidemiological and economic simulation model to evaluate the spread and control of infectious bovine rhinotracheitis in The Netherlands

Bovine herpesvirus type I (BHV1), causing infectious bovine rhinotracheitis (IBR), was introduced in the Netherlands in 1971. In 1993, about 42% of the dairy cows had antibodies against BHV1. In the future, stricter requirements are anticipated regarding the health status of exported breeding cows and material. To support policymakers in their decisions on IBR eradication, a simulation model was developed in which the epidemiological and economic consequences of various control strategies were evaluated. This paper describes the model and provides an overview of some important outcomes. In the model, dairy herds were classified into different disease states based on (1) the reproduction ratio of the disease (R, defined as the number of secondary cases caused by one infectious animal) (2) the within-herd prevalence, within each value of R and (3) the expected number of infectious animals in an infectious herd within each prevalence range. The dynamic transition probability of a herd going from one state to another per week depends on direct contacts between animals, and other contacts such as transmission through fomites, indirect transmission through other species, airborne transmission and minor disease-specific routes such as venereal or iatrogenic transmission. Five control strategies, including both a voluntary vaccination program and a compulsory vaccination program for all dairy herds were evaluated. A voluntary vaccination program with 50% participation is not expected to lead to eradication of IBR. It appears that compulsory vaccination would be necessary to reach an IBR-free status.

An inactivated gE-negative marker vaccine and an experimental gD-subunit vaccine reduce the incidence of bovine herpesvirus 1 infections in the field

An inactivated glycoprotein E-negative vaccine and an experimental glycoprotein D-subunit vaccine against bovine herpesvirus 1 (V1) were examined for their effectiveness in a randomized, double-bline, placebo-controlled field trial comprising 130 dairy farms. The use of these marker vaccines enabled us to monitor the incidence of infections in vaccinated populations. The aims of this trial were to evaluate whether these vaccines: (1) reduce the proportion of outbreaks in dairy herds; and (2) reduced virus transmission within dairy herds and to what extent. Vaccination with either of the two vaccines significantly reduced the proportion of herds wherein an outbreak occurred as well as the virus transmission within herds, as compared to placebo-treated herds. The estimated number of secondary cases caused by one infectious animal, expressed as the reproduction ratio R, was for both vaccines significantly > 1. This indicates that when BHV1 is introduced into vaccinated herds, major outbreaks may still occur.

The value of bulk milk ELISA Ostertagia antibody titres as indicators of milk production response to anthelmintic treatment in the dry period

An experiment was done to study whether estimation of the herd infection level, by assessing Ostertagia antibodies in bulk milk samples can serve to predict the effect of anthelmintic treatment on milk production. Bulk milk samples were collected from 134 farms at monthly intervals on three occasions prior to the start of the study. The ELISA titres to Ostertagia found in October at the end of the grazing season served as a basis to select 16 and 18 farms as having high and low levels of parasitism respectively. Heifers and cows within each herd were ranked by expected calving date, paired and randomly allocated to be treated with ivermectin or a placebo. Records of milk production and composition were collected for all the trial animals. The response to treatment expressed as the 305 day corrected milk yield of anthelmintic treated animals minus that of placebo treated animals was not statistically significant and amounted to 78 kg for multiparous cows and 124 kg for heifers. For cows as well as heifers the response to treatment was larger in the high antibody level herds than in low antibody level herds, but these differences also lacked statistical significance.

Study on the causes of outbreaks of lungworm disease on commercial dairy farms in The Netherlands

The causes of outbreaks of lungworm disease were determined from the herd histories of 25 affected herds of young cattle. The results indicate that light pasture contamination by carriers and subsequent auto-infections are the most prominent cause of lungworm disease, followed by heavy pasture contamination by carriers. Overwintered pasture infections seem to play a minor role. Adult dairy cows seem to be the predominant carrier animal when light pasture infections are concerned. Heavy pasture infections are almost always caused by calves and yearlings.

Automated feeding of milk replacer and health control of group-housed veal calves

The behaviour, growth rate, feed intake, health and slaughter quality of group-housed veal calves fed automatically with milk replacer were compared with those of veal calves kept in individual crates and bucket-fed the same milk replacer. The growth rate and feed intakes of the group-housed calves were lower than those of the calves in individual crates. Their feed conversion rates were similar and there were no significant differences in carcase conformation. The meat of the group-housed calves was paler in colour. The feeding behaviour of the group-housed calves was studied to see whether sick animals could be identified at an early stage but behaviour alone provided an inadequate detection system. Intensive health controls in one of the trials showed that infectious respiratory and digestive diseases may be a greater problem in group-housed veal calves than in veal calves kept in crates.

[An outbreak of bovine tuberculosis on a dairy farm]

An outbreak of bovine tuberculosis on a dairy farm is described. Following intradermal tuberculination 84 animals out of 111 animals older than 6 weeks had a positive reaction. Of the 34 adult sheep one gave a positive reaction. All animals on the farm were taken over for destruction by the Animal Health Centre. The source of the infection could not be established although there was a strong suspicion that the importation of three older dairy cows had introduced the infection on the farm. A further investigation was done on 45 farms. Two of these farms were infected by buying animals from the dairy farm in question. During the investigations the possible transmission of the infections to people who were in close contact to the infected animals was also investigated. From 35 examined persons 5 had a positive Mantoux-reaction. The outbreak coincided with a political discussion concerning the abolishment of the periodical tuberculination on dairy farms. Since 1 January 1993 the surveillance of bovine tuberculosis in the Netherlands is done by import control and findings in slaughter-houses combined with a good identification system. It is stressed that the examinations of the lymph glands in the slaughter-houses require the necessary attention.

Antibodies against nematodes in serum, milk and bulk milk samples as possible estimators of infection in dairy cows

Antibodies against Ostertagia spp., Cooperia spp. and Dictyocaulus viviparus were assessed in serum and individual milk samples of cows and in bulk milk samples from the refrigerating tank. Titres in milk samples were related to serum titers, but also influenced by milk yield, lactation stage and age of the cow. Correlation coefficients between serum and individual milk samples were highly significant, and varied from 0.42 to 0.56. Correlations between herd means of serum titres and herd means of individual milk titres varied from 0.41 to 0.61, and those between herd means of serum titres and means of bulk milk samples from 0.43 to 0.67. Finally, the correlations between herd means of individual milk samples and means of bulk milk samples varied from 0.52 to 0.82. This variation was dependent upon worm species and whether or not correction for milk yield was applied. The discrimination of herds was evaluated by the between/within herd ratio of variances. F-values for all types of samples were highly significant, and at least as high for milk samples as for serum samples. If, as has been shown for serum samples, a positive relationship exists between the milk yield response to anthelmintic treatment and the mean herd titre of milk samples or bulk milk samples, assessment of these titres could offer a rational basis for treatment of dairy cows.

Risk of infection with bovine herpes virus 1 (BHV1): a review

Bovine Herpes Virus 1 (BHV1) consists of three subtypes, which probably differ in their epizootiological characteristics. BHV1 subtypes 1 and 2a are mainly associated with the respiratory form of the disease (IBR), subtype 2b with IPV/IBP, and subtype 3 with encephalitis. BHV1 subtype 1 is excreted in high titres in nasal secretions and spreads more effectively than the other subtypes. Cattle are the only significant source of viral spread. Although other species may become infected, they probably do not contribute to the spread of BHV1. Airborne transmission or spread of the virus by humans is believed to be of minor importance.

Radiographic and radionuclide lung perfusion imaging in healthy calves and calves naturally infected with bovine respiratory syncytial virus

Nine calves between three and 18 weeks old with serologically confirmed natural bovine respiratory syncytial virus infection were examined clinically, radiographically and by radionuclide lung perfusion imaging. The results were compared with those from seven healthy calves. The diseased calves were euthanased and examined pathologically, virologically and bacteriologically. The clinical signs indicated that the disease was in an acute stage. Radiography of the diseased animals revealed cysts, corresponding morphologically with bullous emphysema, and infiltrations roughly corresponding in distribution with atelectatic and, or, pneumonic areas. Radionuclide lung perfusion imaging revealed no perfusion shifts between the left and right lungs and a normal perfusion pattern in five of the nine diseased calves. The abnormalities in the perfusion patterns of three calves were probably caused by anatomical disorders such as cysts and pleural adhesions, but no cause of the abnormality could be found in one calf. These findings suggest that in calves infected with bovine respiratory syncytial virus, the normal perfusion pattern is maintained until anatomical disorders occur. The pathological examination and radiography revealed that the cranioventral lung fields were particularly poorly ventilated. This finding and the normal perfusion pattern indicate that these parts of the lungs are probably the sites where shuntings and perfusion-ventilation mismatchings occur.

Effect of naturally occurring nematode infections on growth performance of first-season grazing calves

Liveweight of calves on 89 dairy farms was measured at the end of the grazing season and related per herd to the level of exposure to nematode infection during the grazing season. There were significant between-herd variations in antibody titres against Ostertagia spp., Cooperia spp. and Dictyocaulus viviparus as well as in pepsinogen values. All but six herds (93.1%) had gastrointestinal nematode infections, as measured by faecal egg counts in September. Faecal samples of 17 herds (19.3%) contained lungworm larvae in September. Liveweight of calves per herd deviated from -68.1 kg to +84.1 kg from the age-adjusted population mean after their first grazing season. Growth performance up to the time of liveweight measurements was significantly correlated negatively with several serological and parasitological parameters. Data could be fitted by means of both linear and segmented curvilinear regression. Antibody titre against Cooperia spp. and gastrointestinal nematode egg output measured in September accounted for 3.1% (P less than 0.10) and 6.7% (P less than 0.05), respectively, of the variation in growth performance among herds. Certain infection parameters, when combined, accounted for 9.2% of this variation; these were antibody titre against Cooperia spp. and larval counts for both gastrointestinal nematodes and lungworm. Adding certain management factors to these infection parameters resulted in a model explaining 27.6% of the observed variation in growth performance among herds. These factors were supplementary feeding, lungworm vaccination, anthelmintic treatment at housing, date of housing and herd age.

Clinical signs following experimental lungworm infection and natural bovine respiratory syncytial virus infection in calves

Similar clinical signs have been reported in calves infected either by Dictyocaulus viviparus or bovine respiratory syncytial virus. Three experiments were carried out to establish the clinical picture and the course of the disease in animals with these infections. The clinical signs of calves infected with lungworm included coughing, nasal discharge, tachypnoea, abdominal breathing and pyrexia, and auscultation of their lungs revealed increased bronchial sounds. Similar signs were also observed after infection with bovine respiratory syncytial virus, but the signs were more acute and resolved more rapidly than in animals infected with lungworm larvae. Calves infected with lungworm had more serious clinical signs after infection with bovine respiratory syncytial virus than calves, which were not infected with lungworm.

Mismatching of ventilation and perfusion in calves with natural bovine respiratory syncytial virus infection

The cause of arterial hypoxia during natural infection with bovine respiratory syncytial virus was studied in seven calves (three to nine months of age) originating from five herds with respiratory tract disease and serological evidence of infection with the virus. Blood gas values were measured during ambient air breathing and during 100 per cent oxygen breathing. The percentages of contribution to the arterial hypoxia from alveolar hypoventilation, mismatching of ventilation and perfusion, and right-to-left shunting were calculated from the measured parameters. Calculated percentages of total venous admixture varied from 14 per cent of cardiac output in relatively mild cases to 48 per cent in the worst affected animal. This venous admixture had been caused mainly by right-to-left shunting of blood, while mismatching of ventilation and perfusion became important in the more severely affected animals. Alveolar hypoventilation was only important in the worst affected animal.

Effects of two glucocorticoids on milk yield and biochemical measurements in healthy and ketotic cows

The effects of two glucocorticoid compounds (Dexamedium; Intervet. Voreen; Boehringer Ingelheim) were tested in 20 healthy and 28 ketotic dairy cows. Both compounds induced an increased blood glucose concentration and a temporary decrease in the milk yield of healthy dairy cows. Dexamedium reduced the milk yield only of cows producing 25 or more kg milk daily. Of 28 ketotic cows 22 were treated with one of the two glucocorticoid compounds, while the remaining six were treated orally with propylene glycol. After treatment all but one of the cows improved clinically within one week. Biochemical analysis of blood samples revealed that after treatment with any of the three therapeutic compounds some animals responded inadequately to therapy or relapsed after initial recovery.

Clenbuterol hydrochloride in calves with a natural bovine respiratory syncytial virus infection

The effect of clenbuterol hydrochloride on the course of disease in calves with a natural bovine respiratory syncytial virus infection was examined. Six calves (three to nine months of age) originating from four herds with respiratory tract disease and serological evidence of a bovine respiratory syncytial virus infection were used in this study. The calves were injected intravenously with clenbuterol hydrochloride. The effect of clenbuterol on the course of disease was measured using the PO2 in blood taken from an indwelling canula inserted in the caudal auricular artery and by clinical signs. Clenbuterol did not improve clinical signs. After clenbuterol administration arterial PO2 values decreased significantly in five out of six patients. Six to eight hours after medication the mean arterial PO2 values were higher than initial values. The moderate positive effect of clenbuterol after six to eight hours may be caused by enhancing ciliary activity and by the secretolytic activity of clenbuterol.

Flunixin meglumine in calves with natural bovine respiratory syncytial virus infection

Twenty-three calves (three to eight months of age) with serological evidence of bovine respiratory syncytial virus infection were used in this study. The calves originated from four herds with respiratory tract disease. In a double blind trial the calves were injected intravenously with either flunixin meglumine (2 mg/kg body weight) or with a placebo. The effect on the course of disease was measured using the PO2 in capillary blood samples from the ears of the calves and by the effect on body temperature and respiratory rate. Mean body temperature fell significantly in the flunixin meglumine treated group. Statistically significant differences were not found between the treated and control group during the seven-day examination period.

[On information. An essay]

We witnessed the stormy development of electronics during the last few years. The effects of this so-called micro-electronic revolution have gradually become noticeable in anyone's everyday life. This will penetrate into all our lives at an accelerated rate during the present century. The computer may be used as an automatic tool or as an independently operating instrument. In the former case (processing of texts and diagrams is an instance to bear in mind), man should see to it that he uses the tool as a creative individual himself. In the latter case, the strong features of the computer should be made use of. These are: Being able to wait patiently and attentively, which may stand in good stead in monitoring and alarming functions. Being able to react rapidly and accurately, a good quality in controlling a variety of well-defined processes in which the human ability to react fails. The ability to cope with and treat large amounts of data, in which the weak side of the computer should be taken into account, namely the assessment and recognition of situations. A good feature of these developments consists in the fact that man can dispose of a capable electronic slave. The unsatisfactory aspect is that a stupid electronic dictator may be imposed on man.

Onion poisoning of young cattle

Eighty-five cattle (calves and yearlings) were allowed 1000 kg of onions (Allium cepa) a day. Signs of poisoning were observed after five days; 22 animals were affected, one fatally. New illnesses continued to occur for five days after the withdrawal of onions from the diet. Clinical signs included inappetance, tachycardia, staggering and collapse, with jaundiced conjunctivae and haemoglobinuria. Haemolytic anaemia with Heinz bodies in the red cells and leucocytosis were demonstrated.

Respiratory syncytial virus pneumonia in Friesian calves: physiological findings

Clinical, serological and physiological values were measured during and after naturally occurring respiratory syncytial virus pneumonia in four Friesian calves weighing between 120 and 160 kg. Clinical and serological findings were in agreement with the description of spontaneous calf pneumonia, associated with respiratory syncytial virus infection. Pulmonary function values, recorded one, eight, 15 and 57 days after the clinical onset of the disease, provided good evidence that the clinical syndrome associated with respiratory syncytial virus infection in Friesian cattle is at first an acute obstructive disease which is progressively replaced by a moderate subclinical restrictive disease.

Spontaneous bovine respiratory syncytial virus infections in calves: arterial blood gas, pH and bicarbonate values

Arterial blood gas values of 12 calves in the acute stage of a bovine respiratory syncytial virus infection were compared with corresponding values of 11 healthy calves. The patients appeared to be severely hypoxic. Mean (+/- sd) arterial oxygen tension (PaO2) values of patients and healthy calves were 7.7 +/- 1.9 and 14.2 +/- 1.5 kPa, respectively. Hypercapnia was present in only three of the diseased calves. These findings are in close agreement with findings in young children with respiratory syncytial virus infections. It is argued that the pathophysiological mechanism involved probably is a ventilation-perfusion abnormality.

Correlation of a disease scoring system with arterial PO2 values in respiratory syncytial virus infection in calves

The mean arterial PO2 value measured in blood obtained by puncture of the brachial artery of 20 calves with acute clinical signs of a bovine respiratory syncytial virus (BRSV) infection was 8.4 +/- 1.9 kPa. The values differed significantly from arterial PO2 values of eleven healthy calves (mean 14.2 +/- 1.5 kPa). A disease scoring system is presented based on the type of respiration and the findings on auscultation. A high correlation (r = -0.87) was found between disease scores and arterial PO2 values. This indicates that the described disease scoring system can be a useful tool in the evaluation of the severity and course of BRSV infections in calves, and could be used for evaluating the efficacy of BRSV vaccines in the field. The course of disease was studied in 127 calves with clinical signs of serologically proven BRSV infection. Animals with mild respiratory signs during the acute phase of disease remained free of severe respiratory problems until the end of a 35-day examination period. Mean disease scores indicated that animals with severe signs in the acute phase often developed persistent respiratory problems.

Effects of trenbolone acetate and propylene glycol on pregnancy toxaemia in ewes

Eleven ewes with pregnancy toxaemia were monitored clinically and biochemically after daily treatment with trenbolone acetate (30 mg) and propylene glycol (twice daily 100 ml), for at least one week. The clinical signs of pregnancy toxaemia at first examination were less severe than those described in ewes in other countries. After the first treatment, the appetite improved in nine ewes, blood glucose levels increased in 10 ewes and blood ketone body concentrations decreased in nine animals. A statistically significant decrease in mean ketone body levels was found between the day of first examination and the second day thereafter. Four animals recovered before lambing (group 1). One animal lambed one day after the first treatment and recovered. In the remaining ewes clinical and biochemical improvement did not last long. Three of these animals did not recover until after lambing (group 2) and three animals died (group 3). In three animals of group 2 and two animals of group 3 an increase of serum activities of lactate dehydrogenase, sorbitol dehydrogenase, gamma glutamyl transferase and alkaline phosphatase was found. In two necropsied animals of group 3 a severe fatty degeneration of the liver was found. Treatment of pregnancy toxaemia with trenbolone acetate and propylene glycol appeared to have some positive effect in mild cases. In more advanced cases the time of parturition is the crucial factor leading to recovery.

Prevention of bovine respiratory syncytial virus infection and clinical disease by vaccination

A double blind field trial was carried out with a live attenuated bovine respiratory syncytial virus vaccine. The trial involved 530 calves, two to 10 months old, on 27 dairy farms, where respiratory problems due to bovine respiratory syncytial virus infections had been observed during the preceding year. In 17 herds either all calves were vaccinated (nine groups) or all calves received a placebo (eight groups). In 10 herds half the number of calves were vaccinated and the other half kept as non-vaccinated controls. Calves were vaccinated intramuscularly twice with an interval of four to five weeks. These groups were under regular clinical observation and animals were tested periodically for antibodies to bovine respiratory syncytial virus and parainfluenza type 3 virus. Serological examination indicated that no bovine respiratory syncytial virus infection had occurred prior to the first vaccination in August. Vaccination did not cause adverse reactions. Low concentrations of neutralising and complement fixing antibodies were induced by vaccination and a sharp increase of antibody titres was observed after natural infection of vaccinated animals. Infections with bovine respiratory syncytial virus occurred in six out of eight non-vaccinated groups, in nine out of 10 partly vaccinated groups and in only two out of nine completely vaccinated groups. Virus infection in completely vaccinated groups was significantly reduced compared with partly vaccinated and non-vaccinated groups. The incidence of bovine respiratory syncytial virus lower respiratory disease was significantly reduced in completely vaccinated groups compared to non-vaccinated groups. Generally only mild signs of upper respiratory disease were present in completely vaccinated groups after bovine respiratory syncytial virus infection.(ABSTRACT TRUNCATED AT 250 WORDS)

BRS virus, PI3 virus and BHV1 infections of young stock on self-contained dairy farms: epidemiological and clinical findings

The role of bovine respiratory syncytial virus, parainfluenza type 3 virus and bovine herpesvirus 1 as disease agents in 28 groups of young cattle on 19 dairy farms which raised their own replacements was investigated. Bovine respiratory syncytial virus infections occurred in 27, parainfluenza type 3 virus infections in all and bovine herpesvirus 1 infections in three of the 28 groups. Some infections were accompanied by clinical signs while others were entirely subclinical. Clinical respiratory disease was observed on 25 occasions in 20 of the groups. Respiratory disease was associated with a bovine respiratory syncytial virus infection on 15 occasions with parainfluenza type 3 virus infection in four cases and with bovine herpesvirus 1 infection in two cases. In four cases there was no association between the respiratory disease and any of the four virus infections. Bovine respiratory syncytial virus infections caused more serious respiratory problems than parainfluenza type 3 virus infections.

Bovine respiratory syncytial virus infections in young dairy cattle: clinical and haematological findings

Clinical signs and haematological findings during the acute and convalescent phases of an infection with bovine respiratory syncytial virus (RSV) were studied under field conditions. The study was carried out in 139 cattle less than 16 months of age in 16 herds with serologically proven bovine RSV infections. Blood was collected for serological and haematological examination. Repeated clinical examinations were carried out until 35 days after appearance of disease. Signs of general disease such as reduced appetite and a body temperature of 40 degrees C or higher lasted less than three days in most cases. Signs of upper respiratory disease, such as coughing, nasal discharge and conjunctivitis were predominant and persisted in 10 to 30 per cent of the animals till the end of the observation period. Signs of lower respiratory disease such as abdominal breathing, bronchial and bronchovesicular sounds on auscultation and a high respiration rate were valuable in diagnosing the disease. These symptoms were present in about 50 per cent of the animals in the early stages of the disease. They lasted for about six days and disappeared in most animals after about 10 days. On haematological examination statistically significant blood changes were observed. A rise in zinc and iron between day 0 and day 10 and a reduction in copper content between day 10 and day 21 were found.

Epidemiology of BHV 1 virus infections in dairy herds

The epidemiology of bovine herpesvirus 1 (BHV 1) infections was studied in 20 dairy herds. Periodic serological surveillance of these herds during three consecutive years (1980-82) was combined with clinical studies. In 19 herds seropositive cows were found indicating previous exposure to BHV 1. One herd had its first experience with BHV 1 during the study. No indication of virus circulation for at least three years was found in eight herds. In five herds an interval of 2 years without an indication of virus circulation was followed by infections in yearlings, first- and second-calf cows during the third year. One or two cycles of virus circulation in calves and/or yearlings during the 3 year survey were detected in six herds. Most BHV 1 infections passed unnoticed. Signs of respiratory disease in association with BHV 1 infection were observed in three herds: young animals were most seriously affected. Clinical manifestations of BHV 1 infections were less pronounced than a few years ago when infections in cows caused frank signs and diagnosis was frequently possible on the basis of a typical clinical picture. BHV 1 was the cause of abortions in the herd that experienced its first infections during this survey. A survey of the age-specific BHV 1 neutralizing antibody pattern may be helpful for tracing animals and herds at risk of an outbreak of infectious bovine rhinotracheitis.

Serology for diagnosis and epizootiological studies of bovine respiratory syncytial virus infections

The complement fixation test (CFT) and the virus neutralisation test (VNT), performed as a plaque reduction test, were employed to measure antibodies to bovine respiratory syncytial virus. The CFT with bovine sera was performed with supplementation of the complement factors in fresh guinea pig serum by an adequate amount of Clq-factor of the bovine species. Kinetics of maternally derived antibodies and the antibody response after spontaneous and experimental infections and after intramuscular vaccination were studied by both tests. Patterns of development of complement fixing and virus neutralising antibodies were generally similar and titres equalled each other in the test systems that are described. However a VNT detected antibodies a few days earlier after an infection than a CFT and peak-levels reached after a naturally acquired infection decreased faster in a CFT than in a VNT: a mean decrease of 3.1 and 1.4 log2 units was found in 13 weeks respectively. Mean half-life of passive antibodies was 25 days in a VNT. An infection with bovine respiratory syncytial virus could be diagnosed by serology, using a CFT on acute and convalescent serum samples of a number of animals in a group. Serology is preferable to virus isolation for routine diagnosis of bovine respiratory syncytial virus infections. Paired sera, collected at 14-day intervals and examined by CFT, are recommended for the diagnosis of the cause of respiratory disease. A VNT is preferable if low antibody levels are to be detected because non-specific reactions occur in a CFT at low serum dilutions.