Turkey enteric coronavirus (TCV) from intestinal contents of diarrheal poults was isolated and serially propagated in HRT-18 cells, an established cell line derived from a human rectal adenocarcinoma. In these cells, TCV induced cytopathic changes, including polykaryocytosis, which depended on trypsin in the medium and incubation at 41 C. Viral antigens could be demonstrated in the cytoplasm by immunofluorescence, and extracellular virus was detected by an ELISA and negative electron microscopy. The cell-free virus had characteristics of TCV: shape, surface projections, buoyant density of 1.18 to 1.20 g/ml in sucrose, and hemagglutination of rat RBC. The one-step growth curve was complete by postinoculation hours 14 to 16, and maximal titers reached 9 to 9.5 log10 TCID50/ml during 5 passages, after which the titer remained stable. Electron microscopic examination of infected cell monolayers revealed budding of typical coronavirus particles through intracytoplasmic membranes and accumulation of complete virus in cytoplasmic vesicles. Late in the infection, aggregated progeny vial particles were detected near the outer surface of infected cells. One-day-old turkey poults inoculated orally with tissue culture-adapted TCV isolates developed mild to severe diarrhea.

A field study was performed to determine the effectiveness of benzathine cloxacillin for the treatment of infectious bovine keratoconjunctivits in cattle from 2 farms located in northern California. The study was performed between June and September of 1987. Affected calves ranging from 2 to 9 months of age were selected from the main herd when signs of corneal ulceration were observed. The study was conducted in 2 phases. For phase I, the affected calves of herd 1 (n = 21; Holsteins) and herd 2 (n = 43 Angus crossbred), were randomly assigned to 1 of 3 groups, and were either treated with 250 (n = 23) or 375 mg (n = 21) of benzathine cloxacillin, or mineral oil (n = 20) on days 1 and 4. For phase II, affected calves (n = 16; Angus crossbred, 3 to 9 months of age) from herd 2 were treated with benzathine cloxacillin (250 mg). Eight of these calves were retreated on day 4. After treatment, all calves were examined every 72 hours for 16 days. For examinations, a clinical score was assigned to each eye, and the surface areas of photographed corneal ulcers were measured. The ocular secretions were collected and examined culturally for Moraxella bovis. On days 7, 10, and 13, the calves treated with benzathine cloxacillin had significantly (P less than 0.05) lower lesion scores, compared with the controls. The percentage of day-1 area measurements on posttreatment days 4, 7, and 10 were significantly larger in the controls than in the treated calves. The mean healing times of corneal lesions in the 2 antibiotic treatment groups were significantly (P less than 0.05) shorter than in the controls. In the treated calves, the healing times of corneal ulcers less than or equal to 0.05 cm in diameter on day 1 were significantly (P less than 0.05) shorter than the healing times of larger lesions. The healing times of the corneal ulcers in the Angus crossbred calves were significantly (P less than 0.05) longer than the healing times of the Holsteins. The controls had the greatest number of nonhealed corneal ulcers on day 16. The number of calves that remained infected with M bovis on days 4, 7, 10, and 13 was significantly less in both groups of treated calves than in the controls. The scores, surface area measurements, healing times, and the M bovis isolation frequency in the calves of the 250-mg and 375-mg and 1- and 2-dose treatment groups were not significantly different. The minimal inhibitory concentrations (MIC) of penicillin, cloxacillin, and ampicillin in the day-16 isolates from benzathine cloxacillin-treated herd-2 calves were greater than in isolates from corresponding calves on observation day 1; however, twofold increases of the respective MIC of pretreatment and day-16 specimens were not observed. The highest MIC of ampicillin, cloxacillin, gentamicin, oxytetracycline, and penicillin were 0.5, 8.0, 0.5, 2, and 1 migrogram/ml, respectively, for isolates collected during the final study week.

Thirty-two isolates of Campylobacter fetus subsp venerealis were obtained from 1 bull and 4 heifers with experimentally induced infection. When whole-cell antigens of isolates were cross titrated with antisera to the infecting strain, isolates from 3 heifers had limited antigenic variation, whereas whole-cell antigens of isolates from 2 cattle (the bull and a heifer) differed serologically from those of the infecting strain. Changes were detected specifically in 6 heat-labile antigens. Of the 6 heat-labile factors evaluated, all were initially present on the infecting parent strain, but not on early isolates obtained from 4 of the 5 cattle. Restriction enzyme analysis revealed minor variation in the DNA fingerprints of isolates obtained from individual cattle, thus implying stability of the Campylobacter genome once persistent infection is established. Isolates with identical restriction enzyme patterns expressed different heat-labile antigens. Correlation could not be found between the DNA electrophoretic pattern and the expression of heat-labile antigens.

To determine their capacity to host Brucella abortus, face flies were examined 1 to 120 hours after feeding on broth containing bacteria and bovine erythrocytes. Brucella abortus was cultured in large numbers from whole flies for 12 hours after feeding, but not after 72 hours. Histologic analysis showed that brucellae were rapidly taken into the midgut, sequestered from erythrocytes, transiently stored, and shed in the feces; there was no evidence of bacterial replication within epithelial cells. Immunoperoxidase and immunogold techniques revealed that most brucellae in the gut were confined to the lumen by the peritrophic membrane, that brucellae were degraded in secondary lysosomes of midgut epithelial cells, and that intact brucellae passed into connective tissues surrounding the midgut. Bacterial excretion without midgut replication is consistent with transient, but not long-term, insect transmission in nature.

Pathogens causing significant respiratory disease in growing pigs include Porcine reproductive and respiratory syndrome virus, Porcine circovirus 2, swine influenza virus, porcine respiratory coronavirus, Mycoplasma hyopneumoniae, and Bordetella bronchiseptica. The objective of this research was to characterize the respiratory excretion of these pathogens by acutely infected pigs. Pigs were inoculated under experimental conditions with 1 pathogen. Samples were collected from the upper respiratory tract and exhaled air. All pathogens were detected in swabs of the upper respiratory tract, but only M. hyopneumoniae and B. bronchiseptica were detected in expired air from individually sampled, acutely infected pigs. These findings suggest either that the acutely infected pigs did not aerosolize the viruses or that the quantity of virus excreted was below the detection threshold of current sampling or assay systems, or both, at the individual-pig level.

A longitudinal survey of 820 cats in 73 households was conducted over a period of 6 years to establish the fate of pet cats that were seropositive after natural exposure to feline coronavirus (FCoV). In particular, their risk of developing feline infectious peritonitis (FIP) was determined. The seropositive cats were assigned to 1 of 3 groups: cats from households in which FIP had recently been diagnosed; cats from households in which FIP had not been diagnosed, but from which kittens had been relocated and subsequently died of FIP; and cats from households in which FIP had not been diagnosed. Cats in the first group were not at greater risk of developing FIP than were cats in the other 2 groups. Consequently, any household in which seropositive cats live must be considered a potential source of FCoV that can cause FIP. There was no evidence that the enhanced disease, which has been described after experimentally induced infection of seropositive cats, exists in nature. Thus, analysis of the survival of the seropositive cats over periods of up to 36 months indicated that their risk of developing FIP decreased with time, suggesting the development of immunity rather than increased susceptibility to disease. In addition, of 56 cats deemed to have been naturally reinfected because their anti-FCoV antibody titers decreased and subsequently increased, only 3 developed FIP.

Changes in serum alpha-1-acid glycoprotein (alpha-1 AG) concentration in cattle with hepatic abscesses were observed, and function of alpha-1 AG was evaluated, particularly its influence on cellular immune response. Test cattle (n = 4) were inoculated with Fusobacterium necrophorum, control cattle (n = 2) were inoculated with inactivated bacteria, and naturally affected cattle (n = 11) were found in a slaughterhouse. Determination of alpha-1 AG was made by use of a single radial immunodiffusion method. The action on lymphocyte blastogenesis was determined by [3H]thymidine incorporation. Cultured lymphocytes from healthy cattle were treated with variable concentrations of alpha-1 AG purified from serum obtained from cattle with hepatic abscesses and suppression of blastogenesis stimulated by each of 3 mitogens was measured. In cattle with experimentally induced abscesses, serum alpha-1 AG concentration increased for 7 to 10 days after F necrophorum inoculation, its change being parallel to that of sialic acid. High concentration of alpha-1 AG was found in naturally affected cattle and was highly correlated to sialic acid concentration. Suppression of lymphocyte blastogenesis in cattle with experimentally induced hepatic abscesses was highly correlated to serum alpha-1 AG concentration.

Nutritional and physiologic effects of clinically apparent and subclinical Ostertagia ostertagi infections were studied in 3 groups of 5 calves each. Group-1 calves were inoculated with 100,000 Ostertagia ostertagi third-stage larvae (L3)/calf/wk for 14 weeks. Group-2 calves were inoculated with 10,000 L3/calf/wk for 14 weeks, and group-3 calves were not inoculated. Calves in group 1 had decreased dry matter intake and feed utilization from 4 weeks after initial inoculation. Group-2 calves had no changes in dry matter intake, but had decreased feed utilization at 12 and 14 weeks. Calves with clinically apparent infections (group 1) lost a mean weight of 11.8 kg, whereas calves with subclinical infections (group 2) lost a mean of 46.6 kg, and control calves lost a mean of 60.7 kg. Calves with O. ostertagi infections (groups 1 and 2) also had decreased carcass quality at slaughtering, which was reflected in decreased dressing weights and increased water-holding capacity of the rib-eye muscle. Calves in groups 1 and 2 also had lower carcass yield and rib-eye muscle weight, and group-1 calves had decreased protein content. Results of hematologic, pathologic, parasitologic, and clinical examinations mirrored nutritional changes.

Four balance trials were conducted in 3 groups of 5 calves each at 0, 4, 8, and 14 weeks after initial inoculation with Ostertagia ostertagi. Group-1 calves were inoculated with 100,000 third-stage larvae (L3) of O. ostertagi/wk for 14 weeks. Group-2 calves were inoculated with 10,000 L3/wk for 14 weeks, and group-3 calves were not inoculated. Effects of infection on apparent digestibilities of dry matter and nitrogen, and balances of nitrogen and water were evaluated. Neither clinically apparent (group 1) nor subclinical (group 2) O. ostertagi infections had observable effects on the apparent digestibility of dry matter. Subclinical infection also had no significant effects on nitrogen digestibility or nitrogen and water balance. Clinically apparent infection, however, decreased the apparent digestibilities of nitrogen significantly (P < 0.05) at 4, 8, and 14 weeks after inoculation, and decreased nitrogen balance at 4 and 8 weeks after inoculation. Group-1 calves also had lower water intake, fecal-water excretion, and apparent water balance, but higher urinary water output at 4, 8, and 14 weeks after inoculation.

Effects of Ostertagia ostertagi infection on secretion of insulin, pancreatic glucagon, cortisol, gastrin, and pepsinogen were studied in calves inoculated with 100,000 (group 1) or 10,000 (group 2) O. ostertagi infective larvae weekly for 14 weeks. Plasma insulin concentrations in both inoculated groups were lower than those in a noninfected (group 3) control group. The differences between group 1 and group 3 were significant (P < 0.05) at 2 and 12 weeks after initial inoculation. Plasma pancreatic glucagon and cortisol concentrations of groups 1 and 2 did not differ significantly from those of the control group, although plasma pancreatic glucagon concentration was consistently lower in group-1 calves from 4 weeks to the end of the study. Plasma pepsinogen and serum gastrin concentrations also increased significantly (P < 0.05) in both groups that received inoculations. We concluded that decreased plasma insulin concentrations are contributory to changes in postabsorptive protein metabolism, and that serum gastrin concentrations are more representative of the pathologic changes in the abomasum than are plasma pepsinogen concentrations.