Infectious bovine keratoconjunctivitis: evidence for genetic modulation of resistance in purebred Hereford cattle.

A vaccination study was conducted in a herd of purebred Hereford cattle representing 4 selection (genetic) lines. For each of 2 years, half of the cattle were vaccinated with a pilus-enriched Moraxella bovis bacterin. Cows were vaccinated before parturition, and calves were vaccinated at 2 to 3 months of age. None of the cattle was vaccinated for 1 year preceding and 1 year after the 2 years in which cattle were vaccinated. There was a significantly (P less than 0.05) lower percentage of infectious bovine keratoconjunctivitis (IBK) in calves during years cattle were vaccinated than during years cattle were not vaccinated. During years cattle were vaccinated, there were lower percentages of IBK in vaccinated calves when compared with the percentages of IBK in nonvaccinated calves. When calves were compared on the basis of selection lines, regardless of the vaccination group, there were consistent differences in the percentages that developed IBK. Although calves with pigmented and nonpigmented eyes (representing all 4 genetic lines) developed IBK, the genetic line of calves with the most pigmented eyes had the lowest (P less than 0.05) percentage of IBK. Also, across all genetic lines, there was less IBK in pigmented eyes than in nonpigmented eyes. Seemingly, vaccination of dams, before parturition, and young calves reduced the occurrence of severe IBK in a herd situation under natural exposure conditions. The resistance or susceptibility in cattle under good management may be influenced by genetic factors.

Infectious bovine keratoconjunctivitis: comparison of infection, signs of disease and weight gain in vaccinated versus nonvaccinated purebred Hereford heifer calves.

To determine whether the carrier state of Moraxella bovis could be prevented under natural conditions of exposure by vaccination, purebred Hereford calves were vaccinated twice; once in June 1982, and again in September 1982. Eyes of calves were examined for signs of infectious bovine keratoconjunctivitis (IBK) and cultured for M. bovis in June 1982, September 1982, January 1983 and June 1983. When calves were compared on the basis of selection lines (four genetic groups), there were significant (P less than 0.05) differences in the percentages of infection, disease and weight gain between selection line calves, regardless of their vaccination status. Results suggest that vaccination, in conjunction with clinical infectious, bovine keratoconjunctivitis, reduces the carrier state of M. bovis in the herd but the immunity lasted less than 9 months. The disproportionate representation of the most genetically resistant calves among nonvaccinated calves probably accounted for the equivocal results between vaccinated and nonvaccinated calves.

Infectious bovine keratoconjunctivitis: contact transmission.

The transmission of Moraxella bovis was studied in calves in the absence of the face fly (Musca autumnalis) or environmental conditions that might insult the eye. Thirty calves were placed in 10 groups of 1 experimentally infected calf and 2 contact calves each. Over 40 days, only 1 eye in 1 contact calf developed clinical infectious bovine keratoconjunctivitis. The organism was recovered in only 8 of 20 contact calves, whereas infection and disease occurred in all experimentally infected calves. Transmission of M bovis occurring in the absence of some other intervening factor was probably of minimal importance. Seemingly, herd preventive treatment would be most effective when flies and environmental factors are at a minimum.

Infectious bovine keratoconjunctivitis: subconjunctival administration of a Moraxella bovis pilus preparation enhances immunogenicity.

To compare the immune response elicited by 3 routes of vaccination, 36 calves were randomly allotted to 4 groups of 9 calves each. Group I was vaccinated subconjunctivally only. Group II was vaccinated concomitantly, both subconjunctivally and in the dewlap. Group III was vaccinated in the dewlap only. Group IV was not vaccinated and served as a virulence control for the Moraxella bovis culture. Calves in groups I, II, and III were given 2 inoculations with 14 days between inoculations. Twenty-one days after the last inoculation, the ventral conjunctival sac of all calves was instilled with cells of a virulent M bovis strain. After challenge exposure, all vaccinated calves (groups I, II, and III) had evidence of enhanced resistance, compared with the nonvaccinated calves. The highest to lowest gradients of immune responsiveness were: Group I greater than or equal to group II greater than group III greater than group IV. When immune criteria, such as the percentage of diseased eyes, the mean duration of infection, the severity of corneal lesions, and the serologic response were compared, groups I and II were significantly (P less than 0.05) more resistant to challenge exposure than were groups III and IV. Group III was significantly (P less than 0.05) different from group IV in severity of lesions and in serologic response. Also, the mean duration of infection was shorter, and the percentage of diseased eyes was less in group III than in group IV (P greater than 0.10). Group I was more resistant than was group II (P less than 0.10).(ABSTRACT TRUNCATED AT 250 WORDS)

Infectious bovine keratoconjunctivitis: enhancement of Moraxella bovis pili immunogenicity with diphtheria-tetanus toxoids and pertussis vaccine.

A study was conducted to determine whether diphtheria-tetanus-toxoids and pertussis vaccine (DPT) would enhance the immunogenicity of homologous Moraxella bovis pili fractions. Thirty-six calves were divided into 4 groups (I, II, III, and IV) of 9 calves each. Calves in group I were not vaccinated and served as controls. Calves in group II were vaccinated with pili fractions only. Calves in group III were vaccinated with DPT only. Calves in group IV were vaccinated with DPT and pili. Vaccination consisted of 2 inoculations, 21 days apart. Fourteen days after the last vaccinal inoculation was done, the eyes of all calves were exposed to a hemolytic homologous strain of M bovis. The percentage of eyes with disease was significantly less in calves given DPT and pili (P less than 0.001) and calves given pili only (P less than 0.05) than in calves given DPT only or nonvaccinated calves. The lesions were less severe in calves vaccinated with pili only than in calves not vaccinated with pili. Serologic results also showed a positive relationship between the development of serum antibodies against pili and immunity. The results indicate that DPT enhanced the immune response and if used as an adjuvant, might be useful in the development of a vaccine against infectious bovine keratoconjunctivitis.

Effects of aflatoxin ingestion on the development of Moraxella bovis infectious bovine keratoconjunctivitis.

A study was conducted to determine whether measured doses of aflatoxin given under different schedules would influence the pathogenesis of Moraxella bovis induced infectious bovine keratoconjunctivitis (IBK). Calves were allotted to 4 groups (groups I-IV) of 9, 9, 9, and 8 calves, respectively. Group I calves were given aflatoxin for 11 consecutive days starting 5 days before their eyes were exposed to M. bovis. Group II calves were given aflatoxin for 5 consecutive days starting 7 days after their eyes were exposed to M. bovis. Group III calves were given aflatoxin for 5 consecutive days starting 21 days after their eyes were exposed to M. bovis. Group IV calves were not given aflatoxin; but their eyes were exposed to M. bovis on the same day as were the eyes of calves in groups I-III; these calves served as controls. Aflatoxin had little if any influence on the pathogenesis of IBK under the conditions of this study. The results did not rule out an exacerbating effect of M bovis infection on aflatoxicosis in calves. Calves with the highest concentration of aflatoxin in their blood had the more severe signs of aflatoxicosis. Possible reasons for the equivocal results are discussed.

Infectious bovine keratoconjunctivitis: evidence for general immunity.

A study was conducted to determine whether acquired immunity to Moraxella bovis during episodes of infectious bovine keratoconjunctivitis (IBK) was local or general. Twelve calves (principals) were exposed to M bovis in the left eye by conjunctival sac instillation on day 1 and in both eyes on day 21. Six calves exposed in both eyes at day 1 and six others exposed at day 21 served as controls. The mean duration of infection in the right eyes of principal calves was significantly less (P less than 0.001) than that in the left eyes of principal calves, as well as those of the control calves. There were no significant differences (P less than 0.2) in the durations of infection between the 2 groups of the control calves or the duration of infection in the left eyes of principal calves. Five of 6 calves (7 of 12 eyes) in the day 1 controls and 4 of 6 calves (7 of 12 eyes) in the day 21 controls developed IBK. Ten of 12 of the principals developed IBK in the left eye when exposed on day 1, but only 1 of 12 principals developed IBK in the right eye when exposed on day 21. It was concluded that the resistance to infection after initial infection is probably due to a generalized immune response, rather than to a localized response.

Experimental infectious bovine keratoconjunctivitis: efficacy of a vaccine prepared from nonhemolytic strains of Moraxella bovis.

Calves vaccinated with a bacterin prepared from 4 nonhemolytic strains of Moraxella bovis were challenge exposed with a virulent hemolytic strain of M bovis. Ten calves were given 2 vaccinal inoculations 21 days apart. Twenty-one days after the last vaccinal inoculation, the eyes of the 10 vaccinated and the eyes of the 12 non-vaccinated calves were exposed to a hemolytic heterologous strain of M bovis. The percentage of eyes with infectious bovine keratoconjunctivitis was lower, the lesions were less severe, and the duration of infection was shorter in vaccinated calves than in nonvaccinated calves. Seemingly, the resistance induced by nonhemolytic strains of M bovis was at least comparable with the induced by hemolytic virulent strains of that organism. The nature of the immune response in vaccinated calves is discussed.

Infectious bovine keratoconjunctivitis in cattle vaccinated and medicated against Moraxella bovis before parturition.

A vaccination and prophylactic treatment study for infectious bovine keratoconjunctivitis (IBK) was conducted on selection line purebred Hereford and recombination mixed-breed cattle. In February, prepartum cows were allotted to 4 groups: group 1--mixed-breed cows vaccinated with a formalin-killed trivalent Moraxella bovis bacterin; group 2--Hereford cows vaccinated and treated with tylosin; group 3--Hereford cows treated with tylosin; and group 4--mixed-breed cows neither vaccinated nor treated (controls). Groups 2 and 3 were pastured together greater than 3 km for other cattle; cattle added to groups 2 and 3 were treated before being added. Groups 1 and 4 cattle were pastured together; cattle added to groups 1 and 4 were not treated. Cows, and subsequently their calves, were observed cursorily for clinical signs of IBK during the spring and early summer. The eyes of calves were examined in September and October 1979, and their eye secretions were examined for M bovis. The first clinical signs of IBK were seen in the herds in late July, and the largest percentages of acute disease were seen in mid-August. There were no significant differences (P = 0.18) in the percentages of calves that developed IBK, regardless of whether (or not) their dams were vaccinated. A larger percentage of the calves from tylosin-treated cows developed IBK than did calves from nontreated cows. The smallest percentage of disease was seen in calves of cows that were vaccinated only, but the differences were not significant (P greater than 0.10). The percentages of isolations of M bovis were similar (P = 0.23) among the 4 groups of calves. When compared on the basis of breed, the percentage of Hereford calves (62%) that developed IBK was greater than that of the mixed-breed calves (47%). When compared on the basis of color pattern, the percentages with IBK were significantly different (P less than 0.001). The percentages of IBK in calves were: red white-face (70%), black white-face (52%), black black-face with some white on body (40%), black (34%), and others (all color patterns not conforming to the 4 other groups; 21%). When compared on the basis of sire, the percentages of IBK in Hereford calves were significantly different (P less than 0.05). The percentages of affected calves ranged from 80% to 31%; the percentages of affected eyes ranged from 67% to 22%. When compared on the basis of sire, the percentages of IBK in mixed-breed calves were significantly different from each other (P less than 0.001). The percentages of affected calves ranged from 63% to 27% and the percentages of affected eyes ranged from 49% to 16%.

Influence of outdoor winter environment on the course of infectious bovine keratoconjunctivitis.

The effect of environmental conditions on the onset, severity, and duration of Moraxella bovis infection and subsequent clinical disease was studied. Twelve calves were used; 6 were maintained under usual isolated experimental conditions (inside), and 6 were kept under normal feedlot conditions (outside) during the winter (-20 to +15 C). The cattle housed inside had a higher infection rate, a milder disease, and longer duration of infection than did the cattle kept out side. Seemingly, the stress of the cold weather caused a more severe disease of shorter duration.

Isolation of Moraxella bovis ribosomes and their subsequent use in a vaccine against infectious bovine keratoconjunctivitis.

A study was conducted to determine whether a Moraxella bovis ribosomal vaccine would protect calves from infectious bovine keratoconjunctivitis (IBK). Each of 16 calves were given 2 inoculations 21 days apart. Twenty-one days after the 2nd inoculation, 8 of the calves were challenge exposed with a homologous strain culture and 8 calves were challenge exposed to a heterologous strain culture of M bovis. Sedimentation velocity analysis of the ribosomes used in this study indicated that they were mostly 30S and 50S subunits. Chemical assays indicated that the ribosomes were composed of 64% to 65% RNA and 35% to 36% protein. The cesium chloride buoyant density of the ribosomes was 1.62 g/ml. Ribosomes used as antigen gave 1 line of precipitation in a gel-diffusion precipitin test with hyperimmune serum against the whole-cell antigen of the homologous strain of M bovis. The eyes of all the experimentally exposed calves became infected and all calves developed clinical signs of either unilateral or bilateral IBK. None of the sera of the vaccinated calves had detectable precipitins against the ribosomal antigen at the time they were challenge exposed, but most of the sera had precipitins against whole-cell and pilus antigens. The results indicate that M bovis ribosomes, although similar to other bacterial ribosomes, did not protect cattle against IBK.

Wavelength of ultraviolet radiation that enhances onset of clinical infectious bovine keratoconjunctivitis.

Cellulose acetate filtered ultraviolet (UV) radiation and unfiltered UV radiation were used on calves that were subsequently challenge exposed with Moraxella bovis. The onset, course, and severity of infectious bovine keratoconjunctivitis (IBK) were studied. Ten calves irradiated with unfiltered UV had the disease 1 to 2 days after M bovis challenge exposure; all 10 calves had moderate to severe IBK. Ten calves irradiated with filtered UV and 10 calves not irradiated manifested IBK in a similar manner. The date of onset and severity of the disease varied. Evidence is presented to support the contention that the wavelengths (around 270 nm) which are eliminated by cellulose acetate enhance the course of IBK. The effects on IBK of environmentally increased solar UV radiation is also discussed.

Infectious bovine keratoconjunctivitis: effects of vaccination on Moraxella bovis carrier state in cattle.

A study was conducted to determine whether vaccination of cattle while they were undergoing an acute episode of infectious bovine keratoconjunctivitis (IBK), would cause vaccinated cattle to abort Moraxella bovis infection sooner than nonvaccinated cattle. Fourteen calves were allotted into two groups of seven calves each, and the eyes of each calf were exposed to a virulent culture of M bovis. Twenty days after calves were infected and showing signs of IBK, seven calves were vaccinated with M bovis pilus vaccine made from the exposure strain. Ocular and nasal discharges were collected and examined for M bovis for 64 days. Most calves developed signs of IBK after exposure and all but one calf (nonvaccinated) developed ocular infection with M bovis. The mean number of days (33 and 33.3, respectively) of ocular infection was not significantly (P = 0.05) different in the vaccinated calves than in the nonvaccinated calves. The eyes of the calf that did not become infected with M bovis were infected with nearly a pure culture of Escherichia coli. This calf failed to develop ocular infection, but had M bovis in its nasal discharge throughout the study (64 days). Moraxella bovis was isolated from the nasal discharge of other calves only when there were concurrent ocular infections.

Biological effect of ultraviolet radiation on cattle: bovine ocular squamous cell carcinoma.

The relationship between bovine ocular squamous cell carcinoma and ultraviolet radiation was studied. Experimental procedures were devised to irradiate cattle with predetermined quantities of ultraviolet beta. Irradiation induced a preneoplastic ocular growth in one of four irradiated cattle. An epizootiologic study indicates that since 1950 the occurrence of bovine ocular squamous cel carcinoma reported at slaughter has increased. This increase was real and not due to an increase in numbers of cattle.

Ozone depletion: implications for the veterinarian.

Man has inadvertently modified the stratosphere. There is a good possibility that the ozone layer is being depleted by the use of jet aircraft (SST), chlorofluoromethane propellants, and nitrogen fertilizers. Under unpolluted conditions, the production of ozone equals its destruction. By man's intervention, however, the destruction may exceed the production. The potential outcome is increased intensity of solar ultraviolet (280-400 nm) radiation and penetration to the earth's surface of previously absorbed wavelengths below about 280 nm. The increased ultraviolet radiation would increase the likelihood of skin cancer in man and ocular squamous cell carcinoma in cattle. The climate also might be modified, possibly in an undesirable way.

Distribution of paratuberculosis in Wisconsin, by soil regions.

A study was undertaken to determine the relationship between concentration of paratuberculosis-infected herds and soil types in Wisconsin. Locations of farms on which paratuberculosis had occurred between 1971 and 1975 were obtained from the Wisconsin Department of Agriculture. The disease occurred mainly in the rolling and undulating areas. Fifty percent of the infection herds were in the southwestern "driftless area" and the southeast uplands; 43% occurred in the western part of the northern silty and loamy uplands; the other 7% were scattered in the east and east-central part of the state. The disease did not necessarily occur in the areas of high cattle concentration. It was concluded that the disease persisted in regions with acid soils but not in regions with alkaline, calcereous soils.

Susceptibility of the Mongolian gerbil (Meriones unguiculatus) to Mycobacterium paratuberculosis.

Mongolian gerbils (Meriones unguiculatus) were exposed to Mycobacterium paratuberculosis by intraperitoneal and oral routes. Fourteen weeks after exposure, the gerbils were necropsied and tissues were cultured and examined microscopically. Results of the study showed that gerbils can be infected with M paratuberculosis but are not suitable for studies of paratuberculosis.

Intravenous johnin and tuberculin tests in cattle vaccinated with Mycobacterium paratuberculosis cells and subsequently inoculated with Mycobacterium bovis.

Calves at 30 days of age were vaccinated with a killed whole-cell Mycobacterium paratuberculosis vaccine. Four months later, these calves were inoculated with Mycobacterium bovis. The intravenous tuberculin and johnin tests were applied both before and after inoculation. The results of the hematologic investigation had extremes at both high and low values and were too unsuitable for statistical analysis. The intravenous tuberculin test is considered unsuitable for diagnosis of bovine tuberculosis in cattle vaccinated against paratuberculosis.