Clinical and biochemical findings in bovine cerebrocortical necrosis produced by oral administration of amprolium

Purposing to get some hints on cause and early diagnosis for cerebrocortical necrosis (CCN), CCN was produced in three healthy calves by the oral administration of amprolium. All three calves showed central nervous signs characterized by ataxic gait, clonic spasm, astasia and opisthotonus, from 24 to 49 days after the start of daily administration of 321-418 mg/kg amprolium. They showed bradycardia from about 20 days before the appearance of the nervous signs, which was supposed to be a finding of primary change and to be useful for early diagnosis of CCN. At necropsy of the two calves, large necrotic lesion was found in the cerebral cortex, and tissue thiamine levels decreased significantly, especially in cerebrum and cerebellum. In the other calf, injection with 25 mg thiamine tetrahydrofurfuryl disulfide (TTFD) was proved to be effective for the recovery of clinical signs. No significant changes in thiamine level were recorded in the whole blood, but those in erythrocytes decreased slightly at about a week before the appearance of the clinical signs. No significant alteration of thiamine excretion was observed in urine. Those findings suggest that CCN in calves is caused by thiamine deficiency and that the blood thiamine levels cannot be used for diagnosis of CCN.     

Ultrastructural study of experimental cerebrocortical necrosis in calves (author's transl)

Cerebrocortical necrosis (CCN) was experimentally induced in three calves with the thiamine antagonist Amprolium. The calves were followed clinically. At the time of development of typical clinical signs of CCN the calves were killed and necropsied and a complete histopathologic examination was performed. The light microscopic lesions of the cerebral cortex were those of middle laminar necrosis and deep laminar edema. The necrotic zone consisted of fine vesicles and differed only slightly from the edema zone. In the former some neurons were morphologically normal, others showed signs of injury, while in the latter all neurons were injured. The lesions are consistent with those found in natural cases of CCN. Biopsies from the cerebral cortex were taken at the time of early clinical signs. Ultrastructural studies of these biopsies showed no clear difference between the zones of necrosis and edema observed light microscopically. The ultrastructural changes were characterized by dilatations in the neuropil. The cytoplasm and foot plates of the astrocytes had a "watery" appearance and contained dilated mitochondria and large vesicles. The vesicles were continuous with the granular endoplasmic reticulum. It was concluded that the initial morphologic changes in CCN in calves were indicative of a cytotoxic edema of the astrocytes. This may be due to a cytotoxic edema with subsequent loss of cell volume control. The primary astrocytic changes could then lead to neuronal injury.     

Experimental Sarcocystis levinei infection in buffalo calves

Six buffalo calves were orally inoculated with 3 graded doses of sporocysts of Sarcocystis levinei (0.5, 1.0 and 2.0 million sporocysts; 2 calves for each dose) while two more calves were kept as uninoculated controls. One calf from each group was killed at 30 days post infection (DPI) and the other at 80 DPI. Inoculated calves showed a dose dependent response. The calves inoculated with 0.5 and 1.0 million sporocysts did not manifest any clinical signs of disease up to 80 DPI. One of the two calves inoculated with 2.0 million sporocysts showed clinical signs of weakness, emaciation and anaemia during the 5th week post infection. The other calf remained healthy until it was killed at 30 DPI. Pale liver tissue, gelatinization of fat and haemorrhages in the heart were observed in one calf inoculated with 2.0 million sporocysts; only microscopic lesions were seen in other calves. Schizonts and merozoites were not observed in any calf. Mature sarcocysts were observed in cardiac and skeletal muscle of calves killed at 80 DPI whereas no sarcocysts were seen in calves killed at 30 DPI.     

Mycoplasma bovis infection in gnotobiotic calves and combined infection with respiratory syncytial virus

Mycoplasma bovis was inoculated alone or in combination with respiratory syncytial virus into the respiratory tracts of 12 gnotobiotic calves. Clinical signs ranged from transient pyrexia to protracted fever accompanied by severe lower respiratory signs and in one case, arthritis. Pulmonary lesions included foci of coagulative necrosis surrounded by mononuclear cells and suppurative bronchiolitis with varying degrees of lympho-reticular hyperplasia. No enhancement of lesions occurred in the combined infections of M. bovis and respiratory syncytial virus. M. bovis was identified by immunoperoxidase labelling in lesions of necrosis, especially at interfaces between the lesion and mononuclear cells and in bronchiolar exudates. Organisms were also located in necrotic lesions of joint capsules, in tonsillar crypts, and in liver.     

Gross postmortem and histologic examination findings from abortion losses and calf mortalities in western Canadian beef herds

Production losses from abortions, stillbirths, and early calf mortality were described for the 2002 calf crop in 203 beef herds in western Canada. A total of 1689 calves were examined. A summary diagnosis was reported for 64% of aborted calves, 78% of stillborn calves, 88% of neonatal calves, and 94% of the calves > 3 d of age. Diagnoses for aborted calves included: thyroid gland lesions, pneumonia, developmental anomalies, placentitis, and myocardial necrosis or myopathy. For stillborn calves, diagnostic findings included: dystocia, thyroid gland lesions, myocardial necrosis or myopathy, developmental anomalies, and skeletal myopathy or necrosis. The most common diagnoses for neonatal calves (≤ 3 d) were: pneumonia, skeletal myopathy or necrosis, myocardial necrosis or myopathy, accident or trauma, and septicemia. For older calves (3 d to 3 mo), the most common diagnoses included: starvation, abomasal ulcer or perforation, enteritis or colitis, pneumonia, and intestinal volvulus, obstruction, or perforation.     

The clinical pathology of heartwater. II. Studies on cardiac and pulmonary function in 4 calves with experimentally-induced heartwater

Studies to evaluate cardiac and pulmonary function were undertaken in 4 calves suffering from experimentally-induced heartwater. There was a marked variation in the course of the disease. Three of the calves recovered spontaneously after developing clinical signs. These included a rectal temperature in excess of 40 degrees C, anorexia and listlessness but no neurological signs. The remaining calf died 2 days after developing a fever and neurological signs. In the 3 calves that recovered, a mild hypoxemia developed during the acute stage of the disease. Arterial CO2 tension remained within normal limits, but there was a tendency towards an alkalosis. Increases in pulmonary dead space and fluctuations in venous admixture were observed. The calf that died showed similar mild changes in blood gas parameters, despite the presence of a marked reduction in minute volume, and a lung oedema was demonstrated on post-mortem examination. No marked changes in systolic and diastolic blood pressures and in right cardiac intraventricular pressures were observed. Terminally, however, there were marked decreases in stroke volume and cardiac output. These changes were associated with a sharp increase in heart rate. No primary cardiac pathology was observed on clinical and post-mortem examinations.     

No foot-and-mouth disease virus transmission between individually housed calves

The foot-and-mouth disease outbreak in The Netherlands in 2001 most likely started on a mixed veal-calf/dairy-goat farm. The outbreak among the 74 calves on this farm appeared to be limited to four animals, and no clinical signs of FMD were reported. Also on a second veal-calf farm minor clinical signs and limited virus transmission were observed. Since FMD is known to be a very contagious disease, and can cause severe lesions, these observations were disputed. Therefore, we carried out two experiments to determine whether the Dutch FMD virus isolate from 2001 does spread among individually housed calves with limited contacts, either indirect (experiment 1) or direct (experiment 2). In experiment 1, four pairs of calves were housed in an individual box at 1m distance from each other. In experiment 2, two groups of three calves were housed in individual boxes, directly bordering each other. We infected one animal per pair in experiment 1, and the calf in the middle in experiment 2. We recorded clinical signs, virus shedding in saliva and the development of antibodies. In addition, we determined whether the virus was transmitted from the inoculated calves to the neighbour(s). All inoculated calves showed mild signs of FMD--fever, and some vesicles on hooves and/or in the mouth--but only one calf showed signs that were visible without physical examination. All inoculated calves shed virus in the saliva and developed neutralising antibodies. None of the contact animals seroconverted, indicating that virus transmission did not occur. These experiments showed that no virus transmission among individual housed calves can occur. This finding supports the hypothesis of the route of virus introduction to The Netherlands in 2001 and show that the observations on the two veal-calf farms were not impossible.     

Electroencephalographic recordings in dogs suffering from idiopathic and symptomatic epilepsy: diagnostic value of interictal short time EEG protocols supplemented by two activation techniques

The diagnostic value of interictal short time electroencephalographic (EEG) recordings in epileptic dogs under general anaesthesia with propofol and the muscle relaxant rocuronium bromide was investigated. Two activation techniques, namely photic stimulation and hyperventilation, were evaluated for their potential to enhance the diagnostic validity of these recordings. Sixty-one dogs suffering from idiopathic epilepsy and 28 dogs suffering from symptomatic epilepsy were included. Electroencephalograms were recorded using five subdermal EEG electrodes (F3, F4, Cz, O1 and O2). All 89 EEGs were analysed visually and 61 were also evaluated quantitatively with fast Fourier transformation. Interictal paroxysmal epileptiform activity was found in 25% of idiopathic and in 29% of symptomatic epileptic dogs. Quantitative analysis of the EEGs (qEEGs) detected significant differences of frequency analysis in single reading points without any continuous changes of frequency bands. A comparison between healthy and affected brain hemispheres in seven dogs with focal lesions of one hemisphere did not show any significant differences in qEEG analysis. qEEG was not more sensitive than visual evaluation. Despite the use of activation techniques, the results showed that short time EEG recordings in epileptic dogs can detect interictal epileptic activity in less than one third of all seizuring dogs and is not a useful screening method.     

An outbreak of mucosal disease in a dairy herd

An outbreak of mucosal disease (MD) was studied in a dairy herd, comprising 12 cows, 9 heifers and 18 calves. During a period of 1 month, six 5 to 8 month-old calves showed typical signs of MD. They all died or were killed in extremis after 2-8 days with progressively worsening clinical signs. Post mortem lesions were examined in one calf. Non-cytopathogenic MD virus was isolated from serum or tissues from 3 clinically affected calves and from 1 healthy heifer. All cows and heifers except for the viremic one possessed neutralizing antibodies against bovine pestivirus. According to the current MD-pathogenesis concept, the affected calves were probably infected transplacentally during the first half of foetal life with pestivirus from the persistently infected heifer in the herd.     

Spinal Epidural Abscess in Two Calves

Objective— To report clinical signs, diagnostic and surgical or necropsy findings, and outcome in 2 calves with spinal epidural abscess (SEA). Study Design— Clinical report. Animals— Calves (n=2). Methods— Calves had neurologic examination, analysis and antimicrobial culture of cerebrospinal fluid (CSF), vertebral column radiographs, myelography, and in 1 calf, magnetic resonance imaging (MRI). A definitive diagnosis of SEA was confirmed by necropsy in 1 calf and during surgery and histologic examination of vertebral canal tissue in 1 calf. Results— Clinical signs were difficulty in rising, ataxia, fever, apparent spinal pain, hypoesthesia, and paresis/plegia which appeared 15 days before admission. Calf 1 had pelvic limb weakness and difficulty standing and calf 2 had severe ataxia involving both thoracic and pelvic limbs. Extradural spinal cord compression was identified by myelography. SEA suspected in calf 1 with discospondylitis was confirmed at necropsy whereas calf 2 had MRI identification of the lesion and was successfully decompressed by laminectomy and SEA excision. Both calves had peripheral neutrophilia and calf 2 had neutrophilic pleocytosis in CSF. Bacteria were not isolated from CSF, from the surgical site or during necropsy. Calf 2 improved neurologically and had a good long‐term outcome. Conclusion— Good outcome in a calf with SEA was obtained after adequate surgical decompression and antibiotic administration. Clinical Relevance— SEA should be included in the list of possible causes of fever, apparent spinal pain, and signs of myelopathy in calves.     

Suspected sheep-associated malignant catarrhal fever in a zero-grazed dairy herd in Kenya

An outbreak of a disease characterised by very high mortality occurred in a group of nine calves (1B4 months old) in a zero-grazing unit 2-3 weeks after an introduction of an apparently healthy alien sheep into the calf pen. Five of the six calves which contracted the disease died. The main clinical signs observed were marked depression, persistently high body temperature (40,5-41,5 degrees C), copious mucopurulent nasal and ocular discharges, dyspnoea, bilateral keratoconjunctivitis with corneal opacity, enlargement of the superficial lymph nodes and marked erythema and/or superficial erosions of the buccal mucosae. At necropsy there were lesions in the upper respiratory and digestive tracts, lymph nodes, brain, eyes, liver, kidneys and the urinary bladder.The lesions were histopathologically characterized by fibrinoid vasculitis which was accompanied by lymphocytic infiltration in the parenchyma of the affected tissues. Based on the evidence of contact between the calves and the recently introduced foreign sheep, the characteristic clinical signs and histopathological findings, a diagnosis of sheep-associated malignant catarrhal fever was made.     

Blood bactericidal assay (Pasteurella haemolytica) comparison of morbidity in marketed feeder calves

An in vitro bactericidal assay that used bovine heparinized blood was investigated for its usefulness in detecting differences in the bactericidal immunity of calves against Pasteurella haemolytica serotype 1 (Ph1). Greater than 90% of killing occurred within 30 minutes. The substitution of fetal calf serum for autologous calf plasma caused loss of bactericidal activity of the blood. Decomplemented calf serum also was low in bactericidal activity. The blood bactericidal assay appears to be opsonin antibody-dependent and complement-dependent. The coefficient of variation (CV) that can be expected with this assay was established by use of a group of 8 calves; within-day CV maximum was 0.9, and between-day CV maximum was 2.1. The blood bactericidal assay was used to evaluate 30 calves under typical market stress from 4 farms in eastern Tennessee. All calves had decreased bactericidal activity, as they moved into a feedyard in Texas. The bactericidal activity was reduced among sick calves, based on the severity of clinical signs. Morbidity was highest during the first 14 days in the feedlot. During this period, healthy calves had a decreased bactericidal index (BI) of 4 points, and calves with clinical signs of bovine respiratory tract disease for 3 days had a decreased BI of 8 points. The average reduction in the BI of calves with clinical signs of bovine respiratory tract disease for 6 or more days was 14 points.     

Consequences of short term fluctuations of the environmental temperatures in calves--Part 2: Effects on the health status of animals within three weeks after exposure

The aim of the present study was to examine consequences of sudden changes in ambient temperature over a 4-hour period (see part 1 [ELMER & REINHOLD, 2002]) on respiratory health in clinically healthy calves. Therefore, the relationship between short-term changes in ambient temperature and the occurrence of clinical respiratory disease was checked over a period of 3 weeks after exposure in 10 calves exposed to 5 degrees C, in 9 calves exposed to 35 degrees C and in 8 control calves (kept at 18-20 degrees C). Within the period beginning 3 days before exposure and lasting until up to 21 days after exposure, each calf was examined clinically. Rectal temperature and respiratory rate were measured daily. All calves were euthanised on day 21 after exposure. Macroscopically visible pneumonic lesions were evaluated using a semiquantitative system. Tissue samples from tonsils, bronchi, trachea, lung and mediastinal lymph nodes were examined bacteriologically. In contrast to non-exposed control calves, severe respiratory illness was observed in individual calves of both exposed groups (5 degrees C, 35 degrees C). Significant increases in body temperature, respiratory rate and animal losses (2 calves died in the group exposed to 5 degrees C, one calf died in the group exposed to 35 degrees C) were the main clinical findings. At necropsy (3 weeks after exposure), no pneumonic lesions were observed in control calves--despite the fact that this group had the highest microbiological colonisation rates in tonsils and in large airways, i.e. trachea and bronchi, within all groups. However, variable pneumonic lung lesions were seen in remaining calves exposed to cold or warm air (5 degrees C, 35 degrees C). The microbiological examination confirmed that mainly Mycoplasma spp. were identified in the lung tissue of calves exposed to 5 degrees C while Pasteurella multocida and/or Mannheimia haemolytica were the only germs found in the lung tissue of calves exposed to 35 degrees C. The results of parts 1 and 2 of the present study related to health issues of calves should be taken into account for future legislation on animal welfare.     

The use of immunomodulators in the control of infectious bovine rhinotracheitis

Three experiments have been carried out to verify the effectiveness of an immunomodulator, Baypamun (Bayer AG) in limiting the spread of Bovine herpesvirus-1 (BHV-1), the causal agent of infectious bovine rhinotracheitis (IBR). In the first experiment, four calves infected with BHV-1 developed severe disease whereas four calves given Baypamun simultaneously with the virus had less severe disease. Four other calves in contact with the infected calves became severely ill but another four given Baypamun were only mildly affected. In the second experiment three calves infected with BHV-1, which reacted with typical disease, were allowed to remain in contact with six calves. All six calves were given Baypamun at various times following the exposure to BHV-1 infection and all showed a much reduced reaction with two treated for 4 days developing no clinical disease. Finally, in the third experiment one calf vaccinated one month before the start of the experiment did not develop any signs of disease when housed together with a calf experimentally infected with BHV-1. Of four other calves, vaccinated when the infected calf showed the first signs of disease, only the two given Baypamun in addition to the vaccine, were protected from clinical disease whereas the two given vaccine only developed classical signs of IBR. In the three experiments the virus shedding by the Baypamun-treated calves resulted to be significantly reduced.     

Pulmonary hypertension in a group of dairy calves

An episode of pulmonary arteritis and sclerosis in twenty 5- to 6-month-old dairy calves was investigated. Sixteen of the calves died acutely, without marked premonitory signs of disease. Four calves evaluated clinically had lethargy, pallor, weakness, tachycardia, tachypnea, and jugular venous distention. Cardiac catheterization performed in 3 of the calves revealed pulmonary hypertension; 1 of these calves survived. Necropsy findings in 19 calves included pale lungs and excess free fluid in the pleural and abdominal cavities. In addition, 13 of 19 calves had a dilated and thin-walled right ventricle; 4 of the calves had right-sided cardiac hypertrophy, and 2 had dilatation of the pulmonary artery. Microscopically, pulmonary arteritis and sclerosis of the small to medium-sized arteries were evident in all calves submitted for necropsy. A lung biopsy specimen from a surviving calf had similar lesions. Centrilobular hepatic necrosis was found in 17 of 19 calves. Investigation of the disease episode, including feed analysis for toxins and serologic and microbiological studies of clinically affected calves and clinically normal in-contact penmates, failed to reveal any associated risk factor. The pulmonary arterial changes in the calves were similar to lung lesions in rats fed monocrotaline.     

Experimental intraamnionic exposure of bovine fetuses with subgroup 2, type 7 Adenovirus.

Three third trimester fetuses were exposed to a subgroup 2, type 7 adenovirus (adeno 7) by intraamnionic infection. The virus caused preterm delivery of two clinically ill calves and one stillbirth. The two premature calves died 12 and 72 hours after birth. An elevated serum neutralizing antibody titer (1:256) to adenovirus 7 was found in one principal calf at birth. Adenovirus 7 was recovered from several tissues of the live calves and the spleen of the stillborn calf. Fetuses exposed by intraamniotnic injection with virus carrier only, were born healthy after normal gestational periods and no viruses were isolated from the tissues. Clinically ill calves were weak, severely depressed and unable to stand and nurse. Gross postmortem lesions were nonspecific and consisted of petechial and ecchymotic hemorrhages and edema of the gastrointestinal tract. Histopathological lesions included vasculitis, necrosis of the mucosa of the forestomach, mild gastroenteritis and acute, nonsuppurative focal necrosis of the liver, kidney and adrenal gland. Intranuclear inclusion bodies were seen in pericytes, macrophages, hepatocytes, epithelial cells of adrenal cortical sinusoids of the zona glomerulosa and zona fasciculata and renal tubular epithelium.     

EXPERIMENTAL ENCEPHALOMYOCARDITIS VIRUS INFECTION IN CALVES

Nine calves, were inoculated intravenously with the Innisfail strain of encephalomyocarditis (EMC) virus. Apart from a mild fever, no obvious clinical signs were noted. A low titre viraemia was demonstrated in all 5 calves from which blood was collected, and EMC virus was recovered from the myocardium of 3 of 6 calves at 2, 3 and 6 days after inoculation. Virus was not recovered from the central nervous system. No excretion of EMC virus in urine or faeces was detected in 3 calves. Histopathological lesions were present in brain tissue from only 1 calf, destroyed 14 days after inoculation, and in the heart muscle from another calf, destroyed 7 days after inoculation. Macroscopic lesions were not seen in these organs. Both neutralising and haemagglutination-inhibiting antibodies were produced within one week of infection, reached a peak in 3–4 weeks and persisted undiminished until 9 weeks after inoculation. By nitration on Sephadex G 200, it was shown that the early response was due to IgM type antibodies, and these were replaced by IgG antibody. One calf was inoculated intracerebrally with EMC virus. It developed a flaccid posterior paralysis and was destroyed 6 days later. Virus was recovered from the brain and spinal cord, but no significant histopathological lesions were detected in brain or spinal cord from this calf.     

Encephalitis and neuronal necrosis in a 3-month-old suckled beef calf

A 3-month-old suckled beef calf from the west coast of Scotland showed neurologic clinical signs for 1 week and was euthanized after failing to respond to treatment. Blood and tissue samples, including the brain, were submitted for diagnosis. Histologic examination of the brain showed neuronal chromatolysis and necrosis in the hind brain and loss of Purkinje cells in the cerebellum, accompanied by mild nonsuppurative encephalitis in the hind brain with a striking lack of inflammation in the cerebellar layers. Other microscopic lesions present were mild nonsuppurative meningitis with perivascular cuffs, diffuse hypergliosis, and occasional foci of neuronophagia. Polymerase chain reaction amplification of viral nucleic acids and specific immunohistochemical labeling allowed the identification of louping ill virus, and serology showed high titers of immunoglobulin M, indicating a recent infection.     

Encephalitis induced by bovine herpesvirus 5 and protection by prior vaccination or infection with bovine herpesvirus 1.

Calves were intranasally challenged with bovine herpesvirus 5 (BHV5) and followed for the development of viral infection, clinical encephalitis, histologic lesions in the brain, and viral sequences in the trigeminal ganglia. Calves that were previously vaccinated with bovine herepesvirus 1 (BHV1, n = 4) or previously infected with BHV1 (n = 5) or that had not been exposed to either virus (n = 4) were compared. No calf developed signs of encephalitis, although all calves developed an infection as indicated by nasal secretion of BHV5 and seroconversion to the virus. Histologic lesions of encephalitis consisting of multifocal gliosis and perivascular cuffs of lymphocytes were observed in calves not previously exposed to BHV1. BHV5 sequences were amplified from the trigeminal ganglia of calves previously vaccinated and from calves not previously exposed to BHV1; calves sequentially challenged with BHV1 and later BHV5 had exclusively BHV1 sequences in their trigeminal ganglia. Administration of dexamethasone 28 days after BHV5 challenge did not influence clinical disease or histologic lesions in either previously unexposed calves (n = 2) or previously immunized calves (n = 2), although it did cause recrudescence of BHV5, as detected by nasal virus secretion.     

Efficacy of a live Pasteurella multocida vaccine for the prevention of experimentally induced bovine pneumonic pasteurellosis

Seventeen Holstein-Friesian calves weighing an average of 139.8 +/- 13.5 (mean +/- standard deviation) kg were used in a study to determine the efficacy of a live vaccine containing of Pasteurella multocida A:3 and Pasteurella haemolytica A:1. Eleven calves received the vaccine by intramuscular injection in the right shoulder, whereas six calves received vaccine diluent and served as non-vaccinated controls. Fourteen days following vaccination (Day 15) all calves were inoculated deep intranasally with 3.6 X 10(7) TCID50 bovine herpes virus-1. On Day 16, calves were stressed by transports, and on Day 17 calves were challenged intratracheally with P. multocida A:3. On Day 22 calves were euthanized and necropsied, and tissues were collected for pathological and microbiological evaluations. Scores were assigned to each calf based on the severity of observed clinical signs. Macroscopic lung lesions were expressed as percentage of tissue involved relative to the total lung tissue of a calf. Plasma fibrinogen concentration, rectal temperature, serum antibody level, microscopic appearance of lung, and microbiologic results were also recorded for analyses. The control calves had significantly higher clinical-sign scores (P less than 0.05) and more severe gross lesions (P less than 0.05) than the vaccinated calves. Although the vaccinated calves had a slight increase of immunoglobulins M and G classes, the differences were not statistically significant (P greater than 0.05, P greater than 0.05). The results of the study indicate that the live Pasteurella vaccine is effective against experimental P. multocida infection in calves.