Plasma and tear concentrations of antibiotics administered parenterally to cattle.

Chloramphenicol, erythromycin, gentamicin, oxytetracycline, penethamate and procaine benzyl penicillin were administered parenterally to cattle and the concentrations of these antibiotics in plasma and tears were assayed microbiologically. Concentrations in plasma and tears were significantly correlated for all antibiotics tested but the concentration of antibiotic in tears and the tear flow rate were not correlated. Lipophilic drugs diffused into the tears in higher concentrations than did drugs which were not lipophilic. Concentrations of lipophilic but not hydrophilic antibiotics in tears could be predicted from the Henderson-Hasselbach equation. In cattle, it is possible through parenteral administration of chloramphenicol, erythromycin, gentamicin or oxytetracycline to achieve antibiotic concentrations in the tears which are bacteriostatic to Moraxella bovis, a primary aetiological agent of infectious bovine keratoconjunctivitis.

Ocular inserts for application of drugs to bovine eyes--in vitro studies on gentamicin release from collagen inserts.

Soluble collagen and insoluble collagen films were impregnated with gentamicin and investigated in vitro as vehicles for the delivery drugs. Succinylated collagen released significantly higher levels of antibiotic than the insoluble films, and maintained mean inhibitory concentrations (MIC) for Moraxella bovis for 24 h.

A national survey of the occurrence of infectious bovine keratoconjunctivitis.

A national mail survey of 4880 beef and dairy producers was undertaken to record details of infectious bovine keratoconjunctivitis. One thousand four hundred and fifty eight (29.8%) questionnaires were returned. The survey confirmed the widespread nature of the disease with higher prevalence in the summer months, in calves and dairy cattle, and in Bos taurus breeds. The constant prevalence contrasts with the disease in New Zealand where it is increasing.

A national survey of the clinical features, treatment and importance of infectious bovine keratoconjunctivitis.

A postal survey of cattle producers throughout Australia was conducted to obtain information concerning the occurrence, signs and treatment of infectious bovine keratocojunctivitis, animals breeds, animal numbers and types, environmental conditions under which the animals were kept and management routines and systems of the animals (Slatter et al 1982). The most common clinical signs reported were ocular discharge (43.9%), corneal opacity (9.9%), or both (46.1%). The majority of respondents (54.8%) indicated duration of infections of at least 3 weeks. The condition was predominantly unilateral (74.7%) but 22.3% of respondents reported an equal occurrence of the condition unilaterally and bilaterally. The most frequently used drugs were homidium bromide (26.7%), oxytetracycline hydrochloride (22.8%), chloramphenicol derivatives (13.7%) and penicillin derivatives (13.5%). However, described treatment regimes indicated that therapeutic levels of antibiotics would not be maintained in the eyes of treated animals. Producers considered that 75% of affected animals showed reduced rates of weight gain, and 64% indicated they were more difficult to handle. An approximate figure of +22,000,000 was determined for loss of national production due to the disease, based on producers' estimates. In addition, a further cost of +1,566,500 was estimated for the labour involved in current treatment regimes. Beef and dairy producers spent different amounts on medications and treated for different durations. The economic significance of the disease justifies further studies on production losses due to the disease and cost effective methods of treatment.

Prevalence of leptospiral titres in normal horses.

Serum samples were collected from 479 clinically normal horses from 11 different locations in Queensland. Using a microscopic agglutination test, 157 serums (33%) reacted to one or more serovars of Leptospira interrogans at a minimum serum dilution of 1/30. The prevalences of reactors among all horses to the serovars tested were pomona 30.5% icterohaemorrhagiae 23.9%, tarassovi 18.8%, hardjo 12.2%, canicola 8.6%, grippotyphosa 3.6%, and australis 2%. There was a significantly higher prevalence of reactors in tropical areas than in sub-tropical areas, but no difference in prevalence between coastal and non-coastal areas.

Stypandra imbricata ("blindgrass") toxicosis in goats and sheep - clinical and pathologic findings in 4 field cases.

Two goats and 2 sheep from field outbreaks of Stypandra imbricata toxicosis had severe lesions in the retina, optic nerves and white matter of the central nervous system. Clinical, ophthalmoscopic, fluorescein angiographic, electroretinographic and histologic atrophy, necrosis and degeneration of axons in the optic nerves and optic tracts and status spongiosus of cerebral white matter.

Regeneration of retinal limiting membranes after chorioretinal biopsy in dogs.

After chorioretinal biopsy in dogs, obtained without vitreous loss, accessory glial cells and fibroblasts filled the defect between cortical vitreous and bare sclera. The proliferating glial cells laid down a new basement membrane which was complete both on the internal and external aspects of the defect. After biopsy complicated by vitreous loss, however, cellular proliferation failed to re-establish complete internal and external limiting membranes, and new formed fibroblastic tissue extended into the vitreous. To our knowledge, this is the first report to describe effective regeneration of the internal limiting membrane of the retina in any species. These findings suggest that when vitreous loss can be avoided, healed chorioretinal biopsies are unlikely to lead to delayed pathological complications.

Stilboestrol toxicity in a dog.

A case of stilboestrol toxicity is described in a dog which was treated for prostatic hyperplasia with stilboestrol dipropionate (10 mg) daily for 5 days. An initial anaemia and thrombocytopaenia of 19,500/microliters was recorded on day 11, and a severe leukocytosis of 125,300/microliters on day 15 was followed by a precipitous drop to 8,400/microliters on day 21. The dog received antibiotic treatment for concurrent peritonitis and prostatitis/cystitis between days 7 and 15. The dog died on day 41 with marrow aplasia.

Chorioretinal biopsy in dogs.

A simplified practical technique for biopsy of retina and choroid has been developed in dogs. A 270 degree circular scleral flap of 3 mm diameter is raised. The risks of chorioretinal bleeding and vitreous loss are greatly reduced by intravenous mannitol and controlled hyperventilation, with hyperoxygenation and transient, systemic hypotension under general anesthesia. Rreasonable ultrastructural detail was preserved in chorioretinal specimens of 1 mm diameter. Repeat biopsies in the same eye are feasible without significant complications.

Myelin oedema, optic neuropathy and retinopathy in experimental Stypandra imbricata toxicosis.

Rats experimentally poisoned with the toxic plant Stypandra imbricata developed acute oedema of central and peripheral myelin and extensive axonal degeneration in the optic nerves. The oedema developed with vacuolation and splitting of myelin lamellae at the intraperiod line. Following recovery from acute intoxication, myelin oedema resolved after 6 to 12 weeks, but severe retinal degeneration and optic nerve atrophy remained. Morphological abnormalities in glial cells and axons were only found in the optic nerves. It was concluded that there is probably also a direct toxic effect on the axons of the optic nerve and the photoreceptor cells of the retina. The chemical nature of the toxin remains to be defined but the marked similarity of its toxic effects to those of hexachlorophene are noted.