Bovine Infectious Keratoconjunctivitis: Serological Aspects of Moraxella bovis Infection

A modification of a gel diffusion precipitin test (GDPT) was used to detect antibodies for Moraxella bovis (M. bovis) in the sera of cattle affected with bovine infectious keratoconjunctivitis (BIK). The test was also used for the detection of sequential antibody development in cattle vaccinated with cultures of M. bovis. Also, strains of M. bovis isolated from cattle herds affected with BIK were characterized serologically as a part of an identification scheme using the test.

A comparison of the antigenic properties of various strains of M. bovis and M. bovis-like organisms was conducted using the test. The results indicated that there might be antigenic relationships between M. bovisand M. bovis-like organisms such as Moraxella liquefaciens, Moraxella nonliquefaciens, an unidentified hemolytic diplococcus, Mima polymorpha, Mima polymorpha var. oxidans and Herellea vaginicola

The authors suggest that the GDPT can be used for serological studies of BIK, and the identification and antigenic analysis of M. bovis. They indicate, however, that a more definitive study is needed to evaluate the reliability of the test for quantitative work.

     

Ocular penetration of oral doxycycline in the horse

OBJECTIVE: To investigate intraocular penetration of orally administered doxycycline in the normal equine eye and to compare intraocular and serum doxycycline concentrations. Procedures Six mares were administered doxycycline at 10 mg/kg every 12 h by nasogastric tube for 5 days. Blood, aqueous, and vitreous samples were collected on days 1 and 5. All samples were assayed for doxycycline concentrations. Aqueous and vitreous samples were also assayed for protein quantitation. RESULTS: Doxycycline was rapidly absorbed after the first dose (T(max) value of 1.42 +/- 1.28 h); and elimination of doxycycline occurred slowly (median t(1/2) = 10.88 h). Doxycycline could not be detected in the aqueous on days 1 and 5, nor could it be detected in the vitreous on day 1. On day 5, the mean vitreous doxycycline concentration was 0.17 +/- 0.04 microg/mL at 2 h after drug administration. CONCLUSIONS: Repeated oral administration of doxycycline in the horse resulted in steady state serum concentrations of < 1 microg/mL; however, it did not result in appreciable concentrations of drug in the aqueous and vitreous in normal eyes.     

SONOGRAPHIC AND RADIOGRAPHIC CHANGES ASSOCIATED WITH SPLENIC TORSION IN THE DOG

The clinical, radiographic, and sonographic signs in three dogs with splenic torsion are presented. AH dogs exhibited weight loss, anorexia, and lethargy. Splenomegaly was consistent radiographic finding in two dogs and large ill-defined midabdominal mass was seen in one dog. The spleen was easily imaged sonographically in all dogs. Splenic sonography in two dogs showed diffuse, hypoechoic pattern consistent with splenic congestion. Hilar splenic vessels were enlarged on the sonograms of two dogs.     

Pathogenesis of corneal lesions caused by Moraxella bovis in gnotobiotic calves

Moraxella bovis was instilled into the conjunctival sac of gnotobiotic calves and corneas were sampled serially after infection. Lesions developed in seven of eight infected calves, but were absent in a noninfected control calf. Histologically, M. bovis was first seen in foci of swollen epithelium and within basal epithelial cells adjacent to ulcers. Corneal ulcers were severe in later stages of infection; fibrin deposits, neutrophils, and bacteria were present in the stromas. Examination of early lesions by scanning electron microscopy showed M. bovis in pits on the surfaces of dark epithelial cells, enmeshed in degenerate epithelial cells and within erosions and an ulcer; in later samples, bacteria were rare. Ultrastructurally, M. bovis was seen in surface pits in superficial epithelial cell processes and within swollen epithelial cells. In stroma, M. bovis was frequently seen among collagen fibrils, within neutrophil phagosomes, and associated with cellular debris. This study demonstrates that a virulent strain of M. bovis can invade bovine corneal epithelial cells and can cause keratitis in the absence of injurious ultraviolet irradiation or other known predisposing environmental factors.     

TESTICULAR ULTRASOUND IN THE NORMAL DOG

The testicles of ten dogs presented for routine castration were imaged with real time ultrasound. A scanning technique using multiple imaging planes (sagittal, transverse, and dorsal planes) was developed to image the testicles and epididymi. The testes were characterized by a coarse medium echo pattern. The mediastinum testis was consistently seen as a 0.2 cm wide linear hyperechoic structure in the central long axis of the testis. The ability to identify and the appearance of the epididymis was variable. The tail was consistently seen as an anechoic to hypoechoic structure. Ultrasound images were compared for anatomical structure with frozen gross sections. Ultrasonic and gross measurements were made and analyzed. Individual gross and ultrasonic measurements compared favorably. Linear regression coefficients between body surface area versus testicular length and diameter were 0.73 and 0.58 respectively. A Wilcoxin signed rank test for similarity p = 0.33 value was found when comparing the right to the left testicle.     

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.     

Comparison of vaccination and treatment in controlling naturally occurring infectious bovine keratoconjunctivitis.

A vaccination study for infectious bovine keratoconjunctivitis was conducted on 108 newborn Hereford calves in the US Department of Agriculture Meat Animal Research Center cattle herd at Clay Center, Nebraska. Groups were allocated so that age of calf, sex of calf, and age of dam were equally distributed between the 54 vaccinated (group I) and the 54 nonvaccinated (group 2) control calves. The dams of both groups of calves were monitored as group 3 controls. An autogenous Moraxella bovis bacterin (formalin-killed, whole cells) was given IM at birth and at approximate intervals of 2 weeks for a total of 3 doses. Bacterial isolation rates for the cattle in groups 1, 2, and 3 during the summer were 92.6%, 92.6%, and 54.1%, respectively, and disease rates were 100%, 96.3%, and 70.6%. The rates were significantly (P less than 0.05) different between calves and cows. Vaccination of calves at birth permitted serum antibodies to develop before the calves were extensively exposed to infection; however, immunity to the disease did not develop. In a treatment study of other animals in the same herd, but in another pasture, the same criteria were used for allocation of 107 cow-calf pairs. Eye spray was applied to treated principals (group 4, 52 calves; and group 6, 53 cows) each week after examination and sample collection. Controls consisted of 54 calves (group 5) and 54 cows (group 7) that were examined and cultured bacteriologically in the same manner. The bacterial isolation and disease rates were less (P less than 0.05) in the treated calves (group 4) than in the nontreated controls (group 5). The differences in bacterial isolation rates between groups 6 and 7 were not significant, but group 6 had less (P less than 0.05) grade III lesions than did group 7. Weekly treatment appeared to be more effective in reducing the incidence of disease than did vaccination.