[Pathogenesis of mixed experimental infection caused by diarrheal viruses--bovine mucosal disease and bovine infectious rhinotracheitis in calves].

The pathogenesis of mixed experimental infection caused by intranasal inoculation of seronegative calves aged 4-6 months with bovine viral diarrhea-mucosal disease (BVDMD) (cytopathogenic) and infectious bovine rhinotracheitis (BRT) viruses, was studied. Consecutive injections of viruses resulted in acute respiratory disease that was severer and accompanied by necrotic rhinotracheitis and acute catarrhal bronchopneumonia than individual injections. BVDMD virus was reisolated from the samples taken from the respiratory tract, intestine, and lymphoid system. The longer excretion of BRT virus with nasal swabs and its high concentration in the respiratory organs suggests its more potent pathogenic properties during reproduction of BVDMD virus.

A non-specific defence inducer in preventing clinical signs of infectious bovine rhinotracheitis in calves.

One calf was infected with bovine herpesvirus-1 (BHV-1) and mixed with five other calves, of which one had been vaccinated with a BHV-1 modified live vaccine one month earlier. The other four calves were vaccinated at the time the experimentally infected calf developed the first signs of the disease (fever, depression, nasal discharge), i.e. on post infection day (PID) 2. In addition to the vaccine, two of the four PID 2 vaccinated calves also received a non-specific defence (NSD) inducer (Baypamun, Bayer AG) at the same time as the vaccine. The calf that was vaccinated 1 month before the start of the experiment, as expected, did not show any signs of the disease. Of the remaining four, the two vaccine-only calves experienced a classical form of infectious bovine rhinotracheitis. However, the two calves that had also received the NSD inducer remained generally healthy during the entire observation period of 30 days. It was speculated that the use of a NSD inducer once an outbreak of a respiratory disease has started on a farm could be of significant help in an emergency in reducing the clinical manifestations in those animals that may subsequently be infected.

Effects in calves of mixed infections with bovine viral diarrhea virus and several other bovine viruses.

The objective of this study was to verify whether a mixed infection in calves with bovine viral diarrhea virus (BVDV) and other bovine viruses, such as bovid herpesvirus-4 (BHV-4), parainfluenza-3 (PI-3) and infectious bovine rhinotracheitis (IBR) virus, would influence the pathogenesis of the BVDV infection sufficiently to result in the typical form of mucosal disease being produced. Accordingly, two experiments were undertaken. In one experiment calves were first infected with BVDV and subsequently with BHV-4 and IBR virus, respectively. The second experiment consisted in a simultaneous infection of calves with BVDV and PI-3 virus or BVDV and IBR virus. From the first experiment it seems that BVDV infection can be reactivated in calves by BHV-4 and IBR virus. Evidence of this is that BVDV, at least the cytopathic (CP) strain, was recovered from calves following superinfection. Moreover, following such superinfection the calves showed signs which could most likely be ascribed to the pathogenetic activity of BVDV. Superinfection, especially by IBR virus, created a more severe clinical response in calves that were initially infected with CP BVDV, than in those previously given the non-cytopathic (NCP) biotype of the virus. Simultaneous infection with PI-3 virus did not seem to modify to any significant extent the pathogenesis of the experimentally induced BVDV infection whereas a severe clinical response was observed in calves when simultaneous infection was made with BVDV and IBR virus.

Preincubation of bovine blood neutrophils with bovine herpesvirus-1 does not impair neutrophil interaction with Pasteurella haemolytica A1 in vitro.

In this study we examined the direct effects of bovine herpesvirus-1 on the interaction of bovine blood neutrophils with Pasteurella haemolytica A1. Preincubation of neutrophils for approximately 2 h in vitro with BHV-1 at a multiplicity of infection of 5:1 had no effect on neutrophil random migration and directed migration to zymosan-activated bovine serum. Neutrophils also were unimpaired in their ability to ingest and kill P. haemolytica A1. Preincubation of neutrophils with BHV-1 did not elicit an oxidative burst, as measured by luminol-enhanced chemiluminescence, nor did it alter neutrophil chemiluminescence in response to opsonized P. haemolytica A1. Prolonged preincubation with BHV-1 for 18-24 h similarly did not affect neutrophil chemiluminescence in response to opsonized P. haemolytica A1. The susceptibility of neutrophils to the lethal effects of crude P. haemolytica cytotoxin also was unaltered by preincubation with BHV-1. We observed no evidence of BHV-1 replication in bovine neutrophils as determined by indirect immunofluorescence and electron microscopy. Previous reports have indicated that active BHV-1 infection alters certain neutrophil functions and results in hypersusceptibility to pulmonary pasteurellosis. Our results suggest that these effects are unlikely to be mediated directly by BHV-1, but instead may reflect the action of endogenous mediators that are released during active BHV-1 infection.

Evidence for defective neutrophil function in lungs of calves exposed to infectious bovine rhinotracheitis virus.

Calves were exposed to an aerosol of infectious bovine rhinotracheitis (IBR) virus followed five days later by an aerosol of Pasteurella haemolytica. The animals were subjected to bronchoalveolar lavage before IBR and four days after, and again at 0, 4, 24, and 48 hours following Pasteurella haemolytica challenge. The results of these experiments suggest that neutrophil infiltration into the lung, in response to the presence of the bacteria was delayed thereby allowing the bacteria to become established in the lung. Neutrophils in infected animals displayed little random migration in vitro and did not respond to a chemotactic stimulus. It was also found that alveolar macrophages from virus-infected animals were not able to produce neutrophil chemotactic factors. These data suggest that the decrease in neutrophil chemotaxis and the lack of chemotactic factor production by the alveolar macrophage following infection with infectious bovine rhinotracheitis virus may predispose infected cattle to a secondary bacterial infection.

Viral agents and associated lesions detected in a 10-year study of bovine abortions and stillbirths.

In a 10-year survey started in 1980, specimens from 8,995 bovine abortions and stillbirths were submitted to the South Dakota Animal Disease Research and Diagnostic Laboratory. Of these, 8,962 were suitable for some type of examination. Viruses were associated with 948 (10.58%). Bovine herpesvirus-1 (IBR) was detected in 485 (5.41%), and bovine viral diarrhea virus (BVDV) was detected in 407 (4.54%). In 1 year of the survey, BVDV was detected in 8/32 fetuses that had lesions of passive congestion. Bovine herpesvirus-4 was isolated from 47 specimens (0.52%), parvovirus and enterovirus were each isolated from 2, and adenovirus, parainfluenza virus, and pseudorabies virus were each isolated from 1. Malignant lymphoid neoplasia was present in 2 fetuses, and their abortion was assumed to have been caused by the bovine leukosis virus.

Etiologic agents detected in a 10-year study of bovine abortions and stillbirths.

During a 10-year period, specimens from 8,995 bovine abortions were submitted to the South Dakota Animal Disease Research and Diagnostic Laboratory; 8,962 of these specimens were suitable for examination. A supportable diagnosis was made in 2,942 (32.82%) of the abortions examined. An infectious cause was determined for 2,723 (30.38%) and a noninfectious cause for 219 (2.44%). Bacteria caused 1,299 (14.49%), viruses caused 948 (10.57%), and fungi caused 476 (5.31%). The infectious bovine rhinotracheitis virus was associated with 485 (5.41%) and the bovine viral diarrhea virus with 407 (4.54%). The most common noninfectious causes of abortion or stillbirth were anomalous development, 112 (1.25%); dystocia, 56 (0.62%); and twinning, 37 (0.41%). The cause of 6,020 (67.17%) abortions was not determined. Lesions, many suggesting the presence of infection, were present in 1,554 (17.34%) fetuses or placentas in which no infectious agent could be demonstrated.

Histological changes in lungs of calves exposed to an aerosol of Pasteurella haemolytica.

An experiment was designed to study the interaction of Pasteurella haemolytica with an attenuated bovine herpesvirus 1 in calves. Low titre of the virus culture used for aerosol exposure failed to produce measurable interaction. However, the experiment provided the first opportunity to study the light-microscopic changes in lungs of calves (n = 3) to a low-dose exposure (5-min aerosol) of P. haemolytica A1 from a fresh 5-h log-phase culture. The histopathological study was confined to tissue exposed to only P. haemolytica. A limited macroscopic pneumonia was produced in ventral parts of cranial lobes. Four days after exposure, a typical reaction featured four zones. Zone 1a at the centre with acute inflammatory processes and necrosis of phagocytic cells was surrounded by a broad band of compacted, largely necrotic macrophages and polymorphonuclear leucocytes (PMNL) in alveoli of zone 1b. Necrosis was confined to zone 1. Zone 2a frequently occupied the remainder of the lobule with irregular distribution of congestion, oedema with a fibrinous component, and infiltration by numerous PMNL, macrophages and other mononuclear inflammatory cells. The narrow zone 2b was located between zones 1b and 2a and had oedema with a fibrinous component, numerous fibrocytes, few inflammatory cells and empty capillaries. It is suggested that zone 2 served to isolate zone 1 by surrounding it with nonfunctional tissue. The pathogenicity of P. haemolytica is discussed for uncompromised lungs and lungs compromised by virulent BHV1 infection.

Protective effect of inactivated bovine herpesvirus-1 in calves experimentally infected with bovine herpesvirus-1 and Pasteurella haemolytica.

The protective effect of an inactivated whole-virion bovine herpesvirus-1 (BHV-1) immunising inoculum, without adjuvant, against viral-bacterial respiratory disease was studied in three experimental treatment groups of five calves each. One group was boosted 14 days after the first vaccination and at this time the second group received their initial inoculation. Seven days later, calves were challenged with BHV-1 in aerosol and four days after this challenge all calves were exposed to Pasteurella haemolytica A1 in aerosol. Among the three groups, differences in rectal temperature responses four days after viral challenge (P less than 0.01) did not relate to protection. However the main response variable, viral-bacterial pneumonia, was reduced in boosted calves (P less than 0.05).

Effect of copper deficiency on tissue, blood characteristics, and immune function of calves challenged with infectious bovine rhinotracheitis virus and Pasteurella hemolytica.

Fourteen Holstein steers, averaging 30 d of age, were fed a semipurified diet (1.5 mg of Cu/kg) supplemented with 0 (-Cu) or 10 mg of Cu/kg of diet (+Cu) for 5 mo. Calves were then challenged by consecutive exposure to aerosol preparations of infectious bovine rhinotracheitis virus (IBRV) and Pasteurella hemolytica on d 0 and 7, respectively, of the 30-d study. Serum ceruloplasmin and plasma copper were higher in +Cu calves throughout the challenge period and increased in +Cu calves after microbial challenge. Heart weights were higher in -Cu calves, although weights of liver, spleen, and thymus were not different between treatments. Copper concentrations in all tissues as well as thymus zinc were higher in +Cu calves. Serum immunoglobulin M tended to be higher in +Cu calves and increased in both treatments after IBRV challenge. Serum IBRV antibody titers were higher in -Cu calves with detectable seroconversion by d 10 postinfection. In contrast, antigen-specific antibodies to P. hemolytica tended to be higher in +Cu calves on d 21. Copper status did not affect blastogenic response, but phytohemagglutinin (PHA)-stimulated blastogenesis was higher in both treatments after IBRV challenge. Repletion of lymphocyte cultures with copper chloride increased proliferative responses to PHA in both +Cu and -Cu calves, and greater responses at all levels of copper (1 to 16 micrograms/mL) were noted in -Cu calves. These results indicate that copper deficiency affects various physiological characteristics that may be important in immunological defense to pathogenic challenge.

Serum copper, zinc, calcium and phosphorus concentrations of calves stressed by bovine respiratory disease and infectious bovine rhinotracheitis.

The relationship between serum minerals and stress and(or) disease has not been fully evaluated in beef cattle. Two trials were conducted to determine the changes in serum Cu and Zn during market-transit stress and(or) disease. Two additional trials were conducted to determine the changes in serum Cu and Zn after inoculation with infectious bovine rhinotracheitis virus (IBRV), with one of the trials determining the changes in serum Ca and P. Trials 1 (n = 80) and 2 (n = 100) utilized calves that were handled through a normal market-transit system and transported 1,967 km to the feedlot. Trials 3 (n = 37) and 4 (n = 8) used calves that were sero-negative to IBRV and then challenged with 2.7 x 10(5) plaque-forming units of the virus. Serum samples were collected at specified intervals and serum minerals were measured for each trial. Serum Zn for morbid or IBRV-challenged calves was decreased by 34, 57, 29 and 15% (P less than .05) for the four trials, respectively, at peak morbidity. Serum Cu of morbid or IBRV-challenged calves increased 5, 15, 40 and 33% for the four trials, respectively, at peak morbidity. Feed intakes were lower during morbidity for market-transit trials and after IBRV inoculation. Lower feed intake could partially explain the decrease in serum Zn; however, when feed intake was held constant, serum Zn concentration still decreased. Serum Zn decreased and serum Cu increased during market-transit morbidity or after IBRV.

Pathology of bovine abortion and newborn calf death caused by dual infection with Chlamydia psittaci and infectious bovine rhinotracheitis virus.

Nine aborted fetuses and one newborn calf, diagnosed as Chlamydia psittaci (C. psittaci) infection, were pathologically examined. The characteristic lesions in the liver were focal necrosis in 9 aborted fetuses and granulomatous necrotic foci in the newborn calf. Moderate numbers of intranuclear inclusion bodies were found in necrotic foci of the liver, spleen, thymus, lymph nodes, adrenal gland, kidney, lung and forestomach. Immunohistologically, a small number of C. psittaci antigens was demonstrated in necrotic foci of the liver and correlated with distribution of elementary bodies. Moderate numbers of infectious bovine rhinotracheitis (IBR) virus antigens were also detected in degenerating and necrotizing parenchymal cells in various organs and correlated with distribution of intranuclear inclusion bodies. Thus, these aborted bovine fetuses and newborn calf were interpreted as being dually infected with C. psittaci and IBR virus during pregnancy.

Infertility in heifers inoculated with modified-live bovine herpesvirus-1 vaccinal strains against infectious bovine rhinotracheitis on postbreeding day 14.

Heifers were inoculated IV with 1 of 4 modified-live bovine herpesvirus-1 vaccinal strains against infectious bovine rhinotracheitis (2 heifers/strain) on postbreeding day (PBD) 14. The effect of infection on fertility was monitored by plasma progesterone assay at 1- to 3-day intervals from the time of virus exposure until PBD 60. Infertility was detected in 4 of 8 inoculated heifers. In 2 heifers, progesterone concentrations decreased to values indicative of estrus within 10 days after inoculation (PBD 24). The 2 other heifers had evidence of embryonic death on PBD 40 and 42. Two control heifers inoculated with culture medium from noninfected cells maintained their pregnancies.

Colonization of the tonsils of calves with Pasteurella haemolytica.

Tonsils of 10 calves were inoculated with Pasteurella haemolytica (PH) and the degree of colonization was followed by collecting sequential tonsil. wash specimens. Tonsils were colonized for at least 3 weeks after instillation of PH into the tonsillar sinus. Calves with colonized tonsils responded with serum and nasal secretion antibody responses to PH and to leukotoxin. Pasteurella haemolytica was detected in nasal mucus specimens of 2 calves during the week after inoculation of the tonsils, but all other specimens were culture-negative. Infectious bovine rhinotracheitis virus-induced respiratory tract disease 25 days later did not elicit a population increase of PH in the tonsils, and did not elicit shedding of PH in nasal mucus.

Early embryonic death in heifers after inoculation with bovine herpesvirus-1 and reactivation of latent virus in reproductive tissues.

Thirteen crossbred heifers seronegative for bovine herpesvirus-1 (BHV-1) were bred naturally to a seronegative bull. Eight heifers were inoculated with BHV-1, IV, on postbreeding day (PBD) 7 or 14. Viremia was detected in heifers 1 through 7, and virus also was isolated from nasal and vaginal secretions of heifers 2, 3, 4, 6, and 7. The pregnancy status of all heifers was monitored from PBD 14 to PBD 35 by determining plasma progesterone concentrations at 1- to 3-day intervals. Decreased progesterone values indicated that pregnancy was not maintained in BHV-1-inoculated heifers 2, 3, 4, 6, 7, and 8. The postbreeding interestrual period of these 6 heifers was normal or only slightly longer than would be expected in the absence of conception. All 5 noninoculated heifers were pregnant on PBD 35. Three to 4 months after acute infection, all BHV-1 inoculated heifers were treated with dexamethasone for 5 days and were euthanatized. Nasal and vaginal swab specimens were tested daily during dexamethasone treatment for excreted BHV-1, and reproductive tissues and adrenal glands were collected at necropsy for virologic tests and histopathologic examination. Virus reactivation was demonstrated in heifers 2 through 8. The BHV-1 isolations were made from adrenal glands of heifers 2, 3, 5, 6, 7, and 8, vaginal swab specimens of heifers 2, 3, 4, 6, and 7, and nasal swab specimens of heifers 2, 3, and 6. Only heifer 3 had virus in reproductive tissues; these isolations were made from ovary, infundibulum, and uterine tube, but not from endometrium.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of bovine viral diarrhea virus infection on the distribution of infectious bovine rhinotracheitis virus in calves.

Four calves (control animals) were inoculated (by aerosol) with Cooper's strain of infectious bovine rhinotracheitis (IBR) virus given with an ultrasonic nebulizer. Seven other calves (principals) were inoculated (by aerosol) with a noncytopathic strain of bovine viral diarrhea (BVD) virus and 7 days later, with IBR virus. The calves were killed 3 to 8 days after the latter virus was inoculated. Various tissues were collected from the calves during necropsy and assayed for IBR virus. In the control calves, the IBR virus was recovered only from the cranial part of the respiratory tract and, in much lower concentrations, from the caudal part of the respiratory tract. In contrast, the same virus was widely disseminated in most tissues, usually in high concentrations, of the calves first inoculated with BVD virus (principals). These observations indicate that initial BVD virus infection may impair the ability of calves to clear IBR virus from the lungs and to contain the latter virus at the local infection site. The pathogenesis of various forms of IBR virus-induced diseases in calves is discussed.

Experimentally induced pneumonic pasteurellosis: dose-response relationships and protection against natural reinfection in calves.

Calves were inoculated intranasally with 2 X 10(6.2) tissue culture infective doses of infectious bovine rhinotracheitis virus, followed in 7 days by intratracheal inoculations with 1 of 4 challenge doses of pathogenic Pasteurella haemolytica. Severity and duration of the ensuing clinical signs of respiratory tract disease were correlated with the challenge dose of bacteria. Calves given 1 X 10(6) colony-forming units (CFU) of bacteria did not develop reliable clinical evidence of disease, whereas those given 1 X 10(8) CFU or 1 X 10(10) CFU of bacteria developed clinical signs of pneumonic pasteurellosis within 12 to 24 hours of bacterial challenge. Severity of clinical signs was equal at the 10(8) and 10(10) doses of bacteria, but duration of clinical signs was greater in calves given the 10(10) dose. Calves given 1 X 10(12) CFU of bacteria developed relatively severe respiratory tract disease in excess of what was necessary for positive clinical detection. Positive correlations were found between the bacterial challenge dose and the height and duration of increased rectal temperature, amount and duration of increases in ocular and nasal discharges, and the subjective evaluation of depressed attitude and appetite. Correlations were not found between challenge dose and respiratory rate or character, or between challenge dose and complete blood cell count. Convalescent calves were resistant to naturally occurring pneumonic pasteurellosis, which caused severe disease in nontreated calves. Adverse effects of P haemolytica were not observed after the first 4 to 15 days after bacterial administration; however, the bacteria were isolated from nasal secretions of convalescent calves 89 to 116 days after bacterial inoculation.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased elastase activity in nasal mucus associated with nasal colonization by Pasteurella haemolytica in infectious bovine rhinotracheitis virus-infected calves.

Four healthy calves were inoculated with Pasteurella haemolytica serotype 1 by instillation of a broth culture into the middle nasal meatus of the left nostril. Four weeks later, calves were exposed to infectious bovine rhinotracheitis virus by aerosol into both nostrils. All calves became ill, from approximately day 3 through day 10 after virus exposure, and shed increased amounts of nasal mucus. Two calves were induced to shed P haemolytica by the virus infection, and 2 calves required reinoculation with P haemolytica for nasal passages to become actively colonized. Elastase activity in nasal mucus increased about 15-fold within 3 days and peaked about 60-fold over baseline by 7 days after virus exposure. Activity of N-acetyl-beta-D-glucosaminidase, a measure of cell damage and serum leakage, increased slightly by day 3 and reached plateau on day 5, almost threefold over baseline activity. Protein and carbohydrate content increased at a rate similar to that of N-acetyl-beta-D-glucosaminidase activity with about 12-fold and sixfold increases, respectively. None of the variables returned to baseline by 19 days after virus exposure. Increased elastase activity preceded colonization by P haemolytica and decreasing elastase activity preceded decreasing P haemolytica concentration in the nasal secretions. A causal relation between elastase activity and P haemolytica colonization could be mediated by cleavage of epithelial cell surface fibronectin and exposure of receptors.

Infection of the middle nasal meatus of calves with Pasteurella haemolytica serotype 1.

Eight healthy nonstressed calves were inoculated with Pasteurella haemolytica serotype 1, by instilling a broth culture into the middle nasal meatus of the left nostril. The inoculated left nostrils shed P haemolytica from the ventral nasal meatus at a steady rate for a mean of 7 days, whereas the uninoculated right nostrils of the same calves shed P haemolytica sporadically and in lower concentrations. The duration, frequency, and concentration of P haemolytica shed from the inoculated nostrils was significantly (P less than 0.05) greater than from the nostrils of other healthy calves that had been exposed by instilling the culture into the ventral nasal meatus of both nostrils in a previous study. The concentration of antibodies (IgG, IgA, and IgM) to P haemolytica increased significantly (P less than 0.05) in serum and nasal secretions after exposure. Four weeks after initial P haemolytica exposure, calves were exposed to infectious bovine rhinotracheitis virus and became clinically ill. Four calves were induced to shed P haemolytica from both nostrils by the virus infection; thus, they were harboring the bacterium and were susceptible to active recolonization. Four calves were not induced to shed P haemolytica. The apparent reason was not that they were resistant to active colonization, but that they were no longer harboring the bacterium, because they became active shedders after they were reinfected with P haemolytica.

Clinical and epidemiological features of 15 incidents of severe infectious bovine rhinotracheitis.

Fifteen incidents of infectious bovine rhinotracheitis (IBR) were studied in herds distributed widely throughout northern Britain. Fattening beef animals (10 outbreaks), dairy cattle (four outbreaks) and suckler beef cows (one outbreak) were affected and all bar one incident occurred in housed cattle during the winter. The first signs of illness noticed were a reduced appetite, dullness, coughing and oculonasal discharge. In 13 of the incidents they were observed in cattle purchased from a market within the previous four weeks. In every outbreak, affected animals developed a serous nasal discharge which became purulent in severe cases. In the early stages the nasal mucosa was congested but later yellow-brown diphtheritic plaques developed. In such animals halitosis was always detected. Soft coughing was frequently heard but pneumonia was rarely confirmed ante mortem. Conjunctivitis and ocular discharge were a major finding in 13 incidents and, in severely affected cases, conjunctival oedema was seen. The drooling of saliva was noticed in 14 incidents but congestion of the oral mucous membranes was the only abnormality found on examination of the oral cavity. Diarrhoea was a consistent feature in one outbreak. As a result of contracting this disease beef cattle failed to put on weight for a period of one to eight weeks and the milk yield of lactating dairy cattle decreased markedly. The morbidity rate was high, being more than 90 per cent in 10 incidents. The mortality rate varied considerably but 7 to 8 per cent of the animals died, or were culled, in three outbreaks. The clinical signs were most severe on intensive units with a high turnover of cattle.