Immunogenicity of a soluble antigen againstPasteurella haemolytica-associated pneumonia in calves

Three experiments were performed to evaluate the immunogenic potency of a soluble fraction ofPasteurella haemolytica against pneumonic pasteurellosis in calves. A soluble antigen was extracted by a 2.5% saline solution fromP.haemolytica. Weaned Holstein bull calves, seronegative for infectious bovine rhinotracheitis virus (IBRV) and the pasteurella antigen, were vaccinated either by repeated subcutaneous (SC) vaccination, or by exposure 3 times to the aerosol ofP.haemolytica antigen. Challenge exposure to aerosol ofP.haemolytica was preceded by infection with IBRV, or in experiments 2 and 3, the virus exposures were combined with a stress treatment. The lung lesions were examined at necropsy 3 to 8 days post infection. In the first experiment, all the vaccinated calves produced specific antibody response to the pasteurella antigen, and none of the calves including controls showed significant lesions in the lung. In the second experiment 2 aerogenically vaccinated calves had no lesions. One of the two SC-vaccinated calves had mild consolidated lesions. Two control calves, one of which died 3 days following the challenge, developed severe fibrinous pneumonia with consolidation of 50% or more of the lung surfaces.P.haemolytica was isolated only from the 2 control animals. In the third experiment, 2 of the 3 control calves developed moderate to severe consolidation, butP.haemolytica was isolated only from one of them. Two of the three aerosol-vaccinated calves also developed significant lesions and one of them yielded the bacteria from the lung. Three SC-vaccinated calves had slight lesions and the organism was not isolated from their lungs. The results did not consistently indicate an immunogenic potential of the soluble antigen againstP.haemolytica-related pneumonia. The effect of stress on the pathogenesis of bovine viral penumonia and correlation between pneumonic lesions and antibacterial resistancein situ are discussed.     

The pathogenesis of enteric colibacillosis in neonatal unsuckled calves.

The development of pathological lesions in the small intestine of neonatal calves is described. Seven newborn calves were challenged orally with a known enteropathogenic strain of E coli 0101k?(A) and killed at varying times after inoculation. Adhesion of bacteria to the mucosa of the small intestine was observed in all calves. A few organisms were seen in the distal small intestine at three hours after inoculation and thereafter adhesion progressed anteriorly along the intestine in calves killed from six to 36 hours. In these calves pathological changes occurred between six and 12 hours after inoculation. Villi were stunted and thickened and the epithelial surface was irregular. A further calf, anaesthetised from five-and-a-half to 10 hours after inoculation and repeatedly sampled from the distal small intestine, developed similar lesions abruptly at nine hours after inoculation. Villus and crypt lengths in the challenged calves were compared with those in three normal uninoculated control calves.     

Plasma pepsinogen,inhibited larval development,and abomasal lesions in experimental infections of calves with Ostertagia ostertagi

Single doses of Ostertagia ostertagi, followed in 42 days by multiple increasing doses in calves, were monitored by fecal egg counts and plasma pepsinogen. The level of plasma pepsinogen increase was related to the increase in graded levels of inoculation and to the fecal egg counts. Plasma pepsinogen in uninfected controls remained below 1 IU/L. Plasma pepsinogen in all calves reached levels greater than 5 IU/L at 48 days of the extended inoculation period, although fecal egg counts remained low in the previously inoculated calves. The previously infected calves had a higher proportion of early fourth-stage larvae, while larger adult worm burdens were found in the previously uninfected calves. Early fourth-stage larvae were observed in extra-glandular sites, notably between the glandular epithelium and basement membrane or within the lamina propria. An immunological response of the host was suggested by the lymphoid cell infiltration in the mucosa. This host immune response may account for the greater larval inhibition exhibited by the previously infected calves.     

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.     

The efficacy of dexamethasone and flunixin meglumine in treating endotoxin-induced changes in calves

Eicosanoids have been implicated in the pathophysiology of endotoxic shock. Drugs which alter eicosanoid production such as corticosteroids and non-steroidal anti-inflammatory drugs (NSAID) are beneficial in treating endotoxic shock. Experiments were conducted to investigate the efficacy of dexamethasone, a corticosteroid, and/or flunixin meglumine, a NSAID, in treating endotoxin-induced changes in calves.Fourteen male calves were assigned to one of four treatment groups: group 1, endotoxin-untreated; group 2, endotoxin-flunixin meglumine treated; group 3, endotoxin-dexamethasone-treated; group 4, endotoxin-flunixin meglumine and dexamethasone-treated. Each calf was given three intravenous and intraperitoneal injections of E. coli endotoxin. Hemodynamic, blood gas, blood chemical and eicosanoid level determinations were obtained.Thirty minutes after endotoxin injection, pulmonary artery pressure (PAP) increased and cardiac output (CO) decreased compared with baseline, corresponding to increased thromboxaneB₂ levels in groups 1 and 3. These groups exhibited a decreased mean arterial pressure (MAP) at three and five hours corresponding to increased 6-keto-prostaglandinF_lalpha. The MAP, PAP and CO of group 4 remained near baseline for the entire six hours, except for a late drop in MAP. Lactic acid levels were significantly increased and arterial bicarbonate levels were reduced by six hours in all groups except for group 4. These results indicate that the combination treatment of flunixin meglumine and dexamethasone prevents many of the metabolic derangements observed during endotoxic shock in calves.     

Experimental trichophytosis in calves caused by cultures of Trichophyton verrucosum and Trichophyton equinum

Tests were performed on 130 one-month-old calves. In 16 animals, treatment with a suspension of Trichophyton verrucosum culture at the dosage of 5 mil. conidia for an area of 10 x 10 of the clipped skin caused clinical trichophytic changes. The length of the incubation time was shorter in the calves scarified before inoculation of the infecting culture (10 to 13 days), as compared with the group of calves without scarification of the skin (11 to 19 days). Only 3 in 6 calves, infected by the same dose into non clipped skin, did contract trichophytosis, manifesting themselves as separate mycotic deposits, which appeared 26 to 35 days after inoculation. Trichophytic changes lasted longest in the group with scarification of the infected area. The ID50 in T. verrucosum and T. equinum cultures was about 1500 conidia per one calf in the case of the method of infecting into clipped scarified skin (area 100 sq cm). A 10 times lower dose (150 conidia per one calf) of the T. verrucosum suspension did not induce visible mycotic changes, but the T. equinum inoculation produced infection in one of 10 calves.     

Effect of decoquinate on the control of coccidiosis in young ruminating calves

Twenty-five 6-week-old Holstein male calves were each inoculated with 500,000 sporulated oocysts of Eimeria bovis. Two nontreated (control) and 3 treated calves (1.5 mg of decoquinate/kg of body weight in feed) were necropsied 7 days after inoculation. Similar groups of calves were necropsied at 12, 18, 22, and 28 days after inoculation. Treated calves were started on medicated feed 2 days before inoculation or at 7, 12, or 15 days after inoculation or were on continuous medication from the day of inoculation. Control calves were not given medication. Early schizonts were in the small intestines of control calves at 7 days after inoculation, but none was in the treated calves that were started on medicated feed 2 days before inoculation. Schizonts were present in the small intestine of both treated and control calves at 12 days after inoculation. At 18 days after inoculation, control calves had schizonts in the small intestine and gamonts and oocysts in the cecum and large intestines, but treated calves only had schizonts in the small intestine. At 22 days, control calves had schizonts in the small intestine and gamonts and oocysts in the large intestine; treated calves had schizonts in the small intestine. At 28 days, controls still had schizonts in the small intestine and gamonts and oocysts in the cecum and large intestine; the treated calves that had been on continuous medication did not have schizonts, gamonts, or oocysts in the tissues. Decoquinate apparently kills sporozoites or arrests development and release of merozoites from the schizonts when fed at 1.5 mg/kg of body weight in the feed.     

Skin testing, fecal culture, and lymphocyte immunostimulation in cattle inoculated with Mycobacterium paratuberculosis.

Fourteen calves at 21 days of age were experimentally inoculated with 100 mg (wet weight) of Mycobacterium paratuberculosis. Three calves were inoculated orally, 4 intravenously, and 7 subcutaneously. Lymphocyte immunostimulation, fecal culture, and intradermal tuberculin skin testing were done between 112 to 150 days following exposure. Lymphocyte immunostimulation test results, conducted at 112 days after inoculation, showed all animals positive to Mycobacterium avium purified protein derivative. Fecal culture results, taken at 120 days after inoculation, showed that 2 of 3 animals inoculated intravenously were positive, whereas only 2 of 7 inoculated subcutaneously were positive (8 of 14 total were positive). Intradermal skin testing results at 150 days with M avium purified protein derivative showed 13 of the 14 calves were positive. Calves were examined at necropsy 153 days after inoculation, and M paratuberculosis was isolated from tissues of each of the 14 calves.     

Leukocyte changes and interferon production in calves injected with hydrocortisone and infected with infectious bovine rhinotracheitis virus.

Correlations between leukocyte counts and serum interferon titers were determined in calves given hydrocortisone (HC) and infectious bovine rhinotracheitis (IBR) virus. Calves were injected with either 1 mg or 3 mg of HC/kg of body weight every 8 hours for a total of 9 injections each. Control calves were given placebo injections. Viral inoculation was given IV 10 hours after the 1st dose of HC or placebo was given. By the time of viral inoculation, all calves injected with HC had developed neutrophilia, and the calves injected with 3 mg of HC also developed leukocytosis, lymphopenia, and eosinopenia; total leukocyte counts in calves injected with 1 mg of HC were increased, but not as much as in other HC-treated calves. Leukocyte counts in calves given placebo remained essentially unchanged before viral inoculation. At 1 day after IBR virus was inoculated, the number of circulating lymphocytes in HC-treated calves and control calves was decreased by more than 50%, on the average, of the counts taken before the HC injections or inoculation of virus. A significant negative correlation existed between the numbers of circulating lymphocytes and serum interferon titers at 1, 2, and 3 days after inoculation with IBR virus. The interferon response of calves undergoing lymphocyte suppression due to HC was not impaired, but was enhanced.     

Isolation of Mycoplasma mycoides subspecies mycoides from Polyarthritis and Mastitis of Goats in Canada

The clinical signs, pathomorphological changes, and microbiological findings in Canadian goats infected with Mycoplasma mycoides subspecies mycoides are discussed. The disease affected mainly young goats and was characterized by septicemia and polyarthritis. Mastitis followed by septicemia was seen in two mature goats. The diagnosis was made by culture and identification of the mycoplasma. Infected goats without clinical signs were identified by cultural and serological (complement fixation) techniques. Healthy carriers are presumably able to transmit the infection and may have brought the disease to Canada.     

Comparative Study of Agar Mediums for Propagation of Ruminant Mycoplasma

A brain heart infusion agar supplemented with 16.7% rabbit serum (BHIR) was found the most suitable for the culturing of ruminant mycoplasma. Gourlay medium and Perreau medium (4, 5) were not suitable for growth of Mycoplasma mycoides var. mycoides or M. agalactiae, but were satisfactory for M. mycoides var. capri.

Four strains of M. mycoides var. mycoides, three strains of M. agalactiae and three strains of M. mycoides var. capri were grown in our laboratory.

     

Bovine homocytotropic antibody in the sera of cattle resistant to infestation withRhipicephalus appendiculatus

The homologous skin sensitizing activity of serum from tick-naive cattle (Bos taurus) and from cattle resistant to the tickRhipicephalus appendiculatus was tested by attempting to induce passive cutaneous anaphylaxis (PCA) in ticknaive calves. The serum from tick-resistant cattle induced PCA, whereas that from tick-naive cattle failed to do so. The PCA was more marked at 72 hours than at 24 hours after administration of the serum. Treatment of the serum by heat at 56°C for 2 hours or by adding 0.1 M 2-mercaptoethanol to it reduced its ability to sensitize.Serum from tick-resistant cattle did not sensitize the skin of heterologous species, namely rabbits, guinea-pigs and rats.     

Immunization of Crossbred Cattle (Bos indicus×Bos taurus) with Fractionated Midgut Antigens against Hyalomma anatolicum anatolicum

Crossbred calves (Bos indicus×Bos taurus) were immunized with a fractionated midgut supernate antigen (GS-F Ag from Hyalomma anatolicum anatolicum). The first inoculation on day 0 was given intramuscularly after emulsification with Freund's complete adjuvant; the second was given subcutaneously on day 14 in incomplete Freund's adjuvant; and the third on day 35 was given subcutaneously without adjuvant. Each injection comprised 1 mg of antigen protein. Ten days after the last inoculation, the immunized calves were challenged simultaneously with 1000 larvae and 20 pairs (20 males and 20 females) of adult H. a. anatolicum on one ear and a similar number of Hyalomma dromedarii ticks on the other ear. There was a significant decrease in the percentage larval engorgement and larval rejection of up to 34% on the immunized calves. A significant increase in the engorgement and preoviposition periods and a significant decrease in the engorged weight, egg mass weight and reproductive index were observed for adult female ticks when fed on the immunized calves. The GS-F Ag also induced a considerable degree of cross-protection in calves against H. dromedarii larval ticks.     

Hematological changes in calves exposed to a mixture of lipopolysaccharide and crude leukotoxin of Pasteurella haemolytica.

The purpose of this investigation was to determine if culture supernatants of Pasteurella haemolytica containing crude leukotoxin and lipopolysaccharide (CLCL) causes disseminated intravascular coagulopathy (DIC) when injected into calves. The effect of intraduodenal (ID) exposure followed by a subsequent subcutaneous (SC) inoculation of either heat-treated or untreated CLCL was evaluated. The relative contribution of the crude leukotoxin and lipopolysaccharide (LPS) to the virulence of P. haemolytica was evaluated. One group of calves received an ID inoculation of CLCL followed two weeks later by a SC inoculation of CLCL; one group received an ID inoculation of tissue culture medium followed two weeks later by a SC inoculation of CLCL; and a third group received an ID inoculation of CLCL followed two weeks later by a SC inoculation of heat-treated CLCL. Hematological parameters used to evaluate DIC included white cell count, platelet count, neutrophil number, fibrinogen, fibrin degradation products, one stage prothrombin time (OSPT), activated partial thromboplastin time, body temperature and clinical signs. Each parameter was measured in calves at 0, 2, 4, 6, 12 and 24 h following the SC inoculation of CLCL. Each group had significant changes over time in all parameters except body temperature. Calves that received a SC inoculation of heat-treated CLCL had smaller changes in all parameters except OSPT compared to the other groups. Results suggest that the LPS and leukotoxin of P. haemolytica exert additive effects on the coagulation cascade and number of peripheral leukocytes, and that the ID inoculation of CLCL does not affect the response of calves to a SC inoculation of toxin.     

Experimental induction of abdominal tympany, abomasitis, and abomasal ulceration by intraruminal inoculation of Clostridium perfringens type A in neonatal calves

The etiologic role of Clostridum perfringens type A in the acute abdominal syndrome characterized by abomasal and rumen tympany, abomasitis, and abomasal ulceration was investigated in neonatal calves. Eight calves, 4 to 12 days old, were inoculated intraruminally with toxigenic C perfringens type A. Before and after C perfringens inoculation, blood samples were collected from all calves for blood gas and serum biochemical analysis and for determination of serum copper concentration; ruminal fluid was obtained for isolation of C perfringens. Calves were monitored daily for clinical signs of the syndrome and, depending on the severity of clinical signs, they were either euthanatized or redosed within 4 to 7 days. After necropsy, specimens obtained from the abomasum and rumen for macroscopic and microscopic examination and for anaerobic bacteriologic culture were processed in routine manner. Intraruminal inoculation of C perfringens type A into healthy calves induced anorexia, depression, bloat, diarrhea, and in some calves, death. Serum copper concentration was within normal range. Necropsy revealed variable degrees of abomasitis, petechial and ecchymotic hemorrhages, and ulcers (ranging from pinpoint to nearly perforate) in the abomasum. Seven of those calves also had multiple trichobezoars in the rumen. These necropsy findings were not seen in calves (controls) given distilled H2O only. In affected calves, acute abdominal syndrome was unrelated to copper deficiency, and C perfringens type A given intraruminally was able to induce clinical signs similar to those of the naturally acquired disease.     

Detection of bacteriuria and bacteremia in newborn calves by a catalase-based urine test

Background: Bacteremia occurs frequently in newborn calves. The predictive value of clinical signs is low, suggesting the use of calf‐side diagnostic tests. Objectives: To investigate testing of urine catalase activity (Uriscreen test) for bacteriuria and bacteremia detection. Animals: Five colostrum‐free calves and 3 colostrum‐fed control calves. Methods: Controlled experimental trial. Colostrum‐free calves were inoculated PO with Escherichia coli O78+. A clinical score was established to define the onset of the illness. Blood and urine (cystocentesis) samplings and cultures, and Uriscreen tests, were performed 4–6 times from inoculation to death. Three control calves received the same management as 3 inoculated calves, but with colostrum and without inoculation. Results: Bacteremia was demonstrated in all of the inoculated colostrum‐free calves and in none of the control calves. The E. coli O78+ strain, E. coli, and Klebsiella spp. were recovered from 4/5, 5/5, and 2/5 inoculated colostrum‐free calves, respectively. Urine cultures were negative for the 2 groups at the start of the experiment; 5/5 colostrum‐deprived inoculated calves were positive for E. coli thereafter whereas 3/3 controls remained negative. Concordance of Uriscreen tests with bacteremia and bacteriuria was 0.86 and 0.88, respectively. Kappa value of agreement between Uriscreen and bacteremia and bacteriuria was 0.73 and 0.76, respectively. Sensitivity of Uriscreen for bacteremia and bacteriuria was 80.0 and 86.6%, respectively, and specificity was 92.8 and 88.8%, respectively. Conclusions and Clinical Relevance: The results suggest that Uriscreen can be used for detection of bacteremia in neonatal calves in connection with a constant bacteriuria.     

Assessing the effectiveness of intubation as a challenge model in contagious bovine pleuropneumonia vaccine experiments

A study was carried out to assess the effectiveness of a bronchoscope in administering a pathogenic field strain of Mycoplasma mycoides subsp. mycoides (MmmSC) in cattle challenge experiments. Out of 16 animals inoculated using the bronchoscope, 10 (62.2%) showed clinical disease as evidenced by fever and 15 (93.8%) displayed typical lesions of CBPP from which MmmSC was isolated. Serum samples collected weekly were tested by Complement Fixation Test (CFT) and competitive enzyme-linked immunosorbent assay (c-ELISA). Antibodies to MmmSC were detected in 10 out of the 16 animals by the CFT and 11 out of the 16 animals by c-ELISA. The onset of clinical disease was as early as 2 days post-inoculation, and most of the animals developed clinical disease 2 to 3 weeks post-infection. These results clearly demonstrate that nasotracheal inoculation of pathogenic strain of MmmSC with the aid of a bronchoscope can lead to early onset of clinical disease; similar to previous studies but with higher numbers of animals showing clinical disease. This is in contrast with previous studies where early clinical disease was observed in as little as 15% of inoculated animals. This nasotracheal inoculation method using a bronchoscope can, therefore, be adopted for use in experimental challenge infections of cattle. This method is found to be a better replacement to the contact transmission method whose drawback includes extra cost of donor animals and unpredictable rate and timing of transmission from intubated to challenge animals.     

Use of computed tomography to evaluate pathologic changes in the lungs of calves with experimentally induced respiratory tract disease

OBJECTIVE: To optimize methods for the use of computed tomography (CT) to assess pathologic changes in the lungs of calves and to determine the effect of treatment on lung consolidation. ANIMALS: 10 male Holstein calves. PROCEDURES: Calves were anesthetized to facilitate CT imaging of the thorax. After initial images were obtained, pneumonia was induced in the calves by inoculation through a bronchoscope. Two calves were used in a preliminary study to refine the inoculation dose and optimize CT images. Four calves were administered florfenicol and 4 calves were untreated control animals. Serial images were obtained 24, 48, and 72 hours after inoculation. After final images were obtained, calves were euthanized, and lung consolidation was estimated by use of lung surface area scoring and water displacement. These estimates were compared with estimated lung consolidation obtained by use of CT. RESULTS: Calves had rapid disease progression. Percentage of lung consolidation was not significantly different between treatment groups for any of the estimation methods. Results of an ANOVA of the 3 assessment methods indicated significant differences among methods. Estimates of the percentage of lung consolidation obtained by use of surface area scoring and CT correlated well, whereas water displacement estimates correlated poorly with other methods of consolidation estimation. CONCLUSIONS AND CLINICAL RELEVANCE: Because of the correlation with other methods for estimation of lung consolidation, CT has the potential to be used to monitor disease progression in calves with experimentally induced respiratory tract disease.     

Platelet aggregation responses and virus isolation from platelets in calves experimentally infected with type I or type II bovine viral diarrhea virus.

Altered platelet function has been reported in calves experimentally infected with type II bovine viral diarrhea virus (BVDV). The purpose of the present study was to further evaluate the ability of BVDV isolates to alter platelet function and to examine for the presence of a virus-platelet interaction during BVDV infection. Colostrum-deprived Holstein calves were obtained immediately after birth, housed in isolation, and assigned to 1 of 4 groups (1 control and 3 treatment groups). Control calves (n = 4) were sham inoculated, while calves in the infected groups (n = 4 for each group) were inoculated by intranasal instillation with 10(7) TCID50 of either BVDV 890 (type II), BVDV 7937 (type II), or BVDV TGAN (type I). Whole blood was collected prior to inoculation (day 0) and on days 4, 6, 8, 10, and 12 after inoculation for platelet function testing by optical aggregometry by using adenosine diphosphate and platelet activating factor. The maximum percentage aggregation and the slope of the aggregation curve decreased over time in BVDV-infected calves; however, statistically significant differences (Freidman repeated measures ANOVA on ranks, P < 0.05) were only observed in calves infected with the type II BVDV isolates. Bovine viral diarrhea virus was not isolated from control calves, but was isolated from all calves infected with both type II BVDV isolates from days 4 through 12 after inoculation. In calves infected with type I BVDV, virus was isolated from 1 of 4 calves on days 4 and 12 after inoculation and from all calves on days 6 and 8 after inoculation. Altered platelet function was observed in calves infected with both type II BVDV isolates, but was not observed in calves infected with type I BVDV. Altered platelet function may be important as a difference in virulence between type I and type II BVDV infection.     

Duration of protection of calves against rhinovirus challenge exposure by infectious bovine rhinotracheitis virus-induced interferon in nasal secretions

Six calves inoculated intranasally with a vaccinal strain of infectious bovine rhinotracheitis (IBR) virus and 6 control calves were given a placebo. All calves were subsequently challenge exposed (by aerosol) with rhinovirus--3 of the calves from each group at 2 days after they were inoculated with IBR virus or with placebo and the remaining calves at 6 days. Nasal excretion of viruses, interferon (IFN) concentrations in nasal secretions (NS), and neutralizing antibody in sera and NS were determined. All calves given the vaccinal IBR virus subsequently had IFN in their NS. Interferon was detected as early as 1 day, reached maximal titers at 2 to 4 days, and persisted in individual calves for 5 to 10 days after inoculation. Rhinovirus shedding was not detected from IBR virus-inoculated calves whose NS contained both rhinovirus antibody and IFN at the time of challenge exposure; such calves were protected at either 2 or 6 days after IBR virus inoculation. The outcome of rhinovirus challenge exposure of calves whose NS contained IFN, but not rhinovirus antibody, varied with the day of challenge exposure. Rhinovirus excretion was detected from 2 of these calves challenge exposed 2 days after IBR virus inoculation, but was not detected from a calf challenge exposed 6 days after inoculation. However, while IFN was present in NS from the former 2 calves, rhinovirus shedding was markedly reduced as compared with that from control calves without IFN or NS antibody at the time of challenge exposure. Consistent relationship was not observed between the rhinovirus neutralizing antibody titer of calves' sera and NS. The antibody titer of NS more closely correlated with protective immunity to rhinovirus infection than did the serum antibody titer.