[Human and animal health]. / Santé humaine et santé animale.

The concept of "one health" applies perfectly to human health and animal health because many diseases are zoonoses. There are many historical examples of effective collaboration between veterinary medicine and human medicine in the development of the first vaccines used in the world (smallpox, rabies, tetanus, diphtheria, tuberculosis, etc.). But when a new disease appears in animals, the risk of possible transmission to humans is difficult to estimate. In the latter case, the loss of consumer confidence in the face of scientific uncertainties can cause a health crisis (examples of bovine spongiform encephalopathy and H5N1 avian plague). But the most serious crisis that we have known since early 2020 is Covid-19 pandemic, which confirms that the modification of the ecosystems of certain wild species such as the horseshoe bats can have significant consequences for the public health. Animals infected with Covid-19 have been contaminated by humans but we cannot currently exclude an animal reservoir risk for SARS-CoV-2 which has circulated around the world.

Tumor necrosis factor-alpha concentration in the aqueous humor of healthy and diseased dogs: a preliminary pilot study.

OBJECTIVES: To determine reference values of tumor necrosis factor-alpha (TNF-α) concentrations in the aqueous humor of control dogs. To show whether these values are significantly different from those obtained in dogs affected with intraocular pathology: acute anterior uveitis (AAU) or chronic primary angle closure glaucoma (PACG). METHODS: Forty-four dogs were included in the study and were divided into two groups: a control group and a group with intraocular disease. Twenty-seven dogs (9 males and 18 females) were examined and found to be normal after a complete ophthalmological examination (control group), 7 (6 females and 1 male) presented with PACG, and 10 (7 females and 3 males) presented with AAU secondary to corneal perforation. One aqueous humor sample (volume ≥ 0.2 mL) was collected from one eye of all dogs. The aqueous TNF-α concentration was determined with an Elisa kit. RESULTS: TNF-α levels were detectable in all dogs. TNF-α levels were significantly higher in the group with intraocular disease compared to the normal control group (P=0.001). In the group with intraocular disease, TNF-α levels were significantly higher in the aqueous humor of the AAU group compared with the PACG group (P=0.001). CONCLUSIONS: In the dog, it is possible to measure the concentration of TNF-α in the aqueous humor. The level of TNF-α was significantly higher in the case of AAU. TNF-α is an interesting biomarker for longitudinal follow-up studies of comparative ophthalmology.

Effect of topical application of tetracaine on intraocular pressure in dogs: preliminary results.

PURPOSE: To evaluate the effect of topical application of tetracaine on intraocular pressure (IOP) measurement by Tonopen in dogs. SUBJECTS AND METHODS: Six healthy male Epagneul Bretons (group 1) and six healthy male black Labrador Retrievers (group 2) were examined. IOP was measured in the right eye (OD) prior to (IOP1) and 1 minute following instillation of one drop of topical tetracaine (IOP 2), and the left eye (OS) (control) prior to (IOP 3) and 1 minute following instillation of one drop of isotonic saline solution (IOP 4). Measurements were performed on two occasions: at 8:00 AM and 3:00 PM. RESULTS: For both groups, IOP measurements were higher in the morning than in the afternoon. For group 1, IOP1 mean (SD), IOP2 mean (SD), IOP3 mean (SD) and IOP4 mean (SD) were 14.6 (2.2) mmHg, 11.3 (3.2) mmHg, 14.4 (2.2) mmHg and 13.5 (3.9) mmHg respectively, while in group 2, IOP1 mean (SD), IOP2 mean (SD), IOP3 mean (SD) and IOP4 mean (SD) were 14.2 (3.8) mmHg, 9.5 (3.7) mmHg, 13.5 (2.8) mmHg and 13.0 (3.8) mmHg respectively. For both groups at each time point, IOP 2 values were significantly lower (P<0.007) than IOP 1 values, whereas IOP 3 and 4 values were not significantly different (P>0.27). CONCLUSION: This study demonstrates that topical application of tetracaine significantly lowers IOP measured by Tonopen due to a possible interaction with melanin. The potential effect of topical anesthetics should be taken in consideration when performing applanation tonometry for clinical, pharmacological and toxicological studies.

Effects of hypercapnia on the electroretinogram in sevoflurane and isoflurane anaesthetized dogs.

To evaluate the effects of induced hypercapnia on the electroretinogram (ERG) in beagle dogs anaesthetized with isoflurane and sevoflurane. Binocular, full-field flash photopic and scotopic ERGs were obtained from six healthy neutered female beagle dogs. In order to determine Vmax and the photopic negative response (PhNR), photopic ERG luminance-response curves were generated with 17 different light stimuli. Photopic flicker ERGs were obtained at 30-Hz temporal frequency. Scotopic ERGs were recorded after 35 min of dark adaptation. For all animals, this procedure was performed once in four different sessions: isoflurane + end-tidal [CO(2)] at 35 mmHg +/- 3 mmHg (ISON), isoflurane + end-tidal [CO(2)] at 65 mmHg +/- 3 mmHg (ISOH), sevoflurane + end-tidal [CO(2)] at 35 mmHg +/- 3 mmHg (SEVON), isoflurane + end-tidal [CO(2)] at 65 mmHg +/- 3 mmHg (SEVOH). In photopic conditions, b-wave amplitudes were significantly smaller in hypercapnic groups (ISON = 170.6 +/- 12.1 microV; ISOH = 132.6 +/- 24.9 microV; SEVON = 170.9 +/- 14.4 microV; SEVOH = 130.2 +/- 22.8 microV). Similarly, in scotopic conditions, b-wave amplitudes were significantly decreased when CO(2) was increased (ISON = 89.4 +/- 14.7 microV; ISOH = 58.2 +/- 17.6 microV; SEVON = 93.4 +/- 24.1 microV; SEVOH = 56.2 +/- 22.2 microV). Flicker peak times were significantly increased in hypercapnic groups (ISON = 25.9 +/- 0.4 ms; ISOH = 27.7 +/- 1.2 ms; SEVON = 25.9 +/- 1.5 ms; SEVOH = 27.2 +/- 0.7 ms). Our results clearly indicate that induced hypercapnia significantly alters the genesis of the electroretinogram at level of ON-pathway and suggest that OFF-pathway is unaffected and that ERGs obtained from isoflurane or sevoflurane anaesthetized dogs are almost identical. Control of hypercapnia must be taken into consideration when ERGs are performed under inhaled anaesthesia in dogs.

ERG findings in three hypothyroid adult dogs with and without levothyroxine treatment.

PURPOSE: To evaluate the effects of levothyroxine (LTh) on the electroretinogram (ERG) of adult dogs. MATERIAL AND METHODS: Binocular, full field photopic and scotopic ERGs were recorded from an anesthetized Maltese Bichon cross (MB), a Yorkshire Terrier (YT) and a Shetland Sheepdog (SS) affected with hypothyroidism and treated with a daily dose of LTh at 20 microg/kg. The photopic ERGs were evoked to 12 different intensities ranging from 0.81 to -2.19 log cd.s/m(2) and presented under photopic conditions in order to assess (from the derived luminance-response curves) Vmax and b : a amplitude ratio parameters. Photopic flicker ERGs were obtained at 30 Hz. The scotopic ERGs (intensity: -3.09 log cd.s/m(2)) were recorded while the retina was dark-adapting and after 32 min of dark adaptation. This procedure was performed on two separate sessions: following a 3-day interruption of LTh treatment (S1) and following 30 days without interruption of LTh treatment (S2). RESULTS: The mean photopic a-wave peak times were 9.8 ms at S1 and 5.0 ms at S2, respectively. The mean photopic b-wave peak times were 23.3 ms at S1 and 11.5 ms at S2, respectively, and the mean scotopic b-wave peak times (after 32 min of dark adaptation) were 45.2 ms at S1 and 26.0 ms at S2, respectively. No other significant ERG changes were observed. CONCLUSION: Our results indicate that a dose of 20 microg/kg of LTh given to adult dogs was accompanied by a marked peak time shortening of both photopic and scotopic ERGs, without affecting other ERG parameters.

[A new model of induced ocular hyperpressure using the minipig]. / Un nouveau modèle d'hyperpression oculaire induite chez le miniporc.

PURPOSE: To characterize a new animal model of moderate chronic hyperpressure obtained by obstruction of the iridocorneal angle (ICA) in the minipig. METHODS: Intraocular hyperpressure was induced in one eye (left) using an injection of methylcellulose (4%) in the anterior chamber of six healthy adult minipigs. Intraocular pressure (IOP) was measured before injection and at D+60 and D+180. The clinical condition thus created was regularly assessed with the following procedures: fundus photography, electroretinography (ERG) to evaluate retinal function, scanning laser ophthalmoscopy (SLO) angiography to measure the arteriovenous filling times (AVFT). Optical microscopy was also performed to evaluate iridocorneal angle and inner retinal layers. RESULTS: In all instances the injection produced a significant increase in the IOP accompanied by a mydriasis, as well as a significant increase in the AVFT and reduction (abolition in some cases) in the i-wave of the ERG. Fundus examination also revealed a blurred aspect and reduction in the calibre of the retinal blood vessels. Similarly, all experimental eyes showed, at optical microscopy, obstruction of the ICA as well a significant loss of of retinal ganglion cells. CONCLUSION: Our results suggest that the above pathophysiological processes, triggered by the induced hyperpressure, share many similarities with human chronic open-angle glaucoma. Consequently, our model, which is very easy to create, could be used to test new therapeutic agents such as neuroprotective drugs.

Ocular fundus images with confocal scanning laser ophthalmoscopy in the dog, monkey and minipig.

Confocal scanning laser ophthalmoscopy (CSLO) is a new technique that enables ocular fundus image recording and retinal dynamic angiography to be performed. The ocular fundus image is acquired sequentially, point by point, and is reconstructed on a video monitor at the rate of 25 images per second. The feasibility of performing both ocular fundus image recordings and retinal angiography image recordings were tested on two dogs, two monkeys and two minipigs using a 40 degrees field I + Tech CSLO. Fundus area of each dog, monkey and minipig were examined without any additional optical devices. The ocular fundus and angiography images were recorded, stabilized and analyzed under the same conditions. For each species, all images were easily recorded without any additional optical device in a lighted room and the morphology of the retinal images generated was similar to those obtained with a camera or angiography of higher resolution. Capillary phase or venous times are presented. Image recording at 25 frames/second enabled more retinal dynamics to be demonstrated than with use of regular angiography. This technique is noninvasive and easy to perform if the eye is fixed and eyelids maintained open. It also allows exploration of retinal microvascularization and could be utilized for clinical, pharmacologic and toxicologic investigations as well.

Recording the photopic electroretinogram from conscious adult Yucatan micropigs.

The micropig is viewed by many as one of the best animal models of human system physiology. The purpose of this study was to develop a simple, rapid and reliable method to record clinical electroretinograms from conscious adult Yucatan micropigs. Photopic ERGs were recorded from 18 conscious animals following a 3-h period of preadaptation to a moderate photopic environment. Rectal temperature and blood pressure were monitored throughout the experiment. In order to test the reproducibility of our procedure, the same protocol was repeated (n=6 micropigs) on three different recording sessions each separated by a 48-h period. Our results indicate that the recording of reproducible ERGs, in the conscious Yucatan micropig, is feasible provided that an adequate experimental approach is used. We believe that our method will enable investigators to perform retinal physiology experiments using an approach which is compatible with that used in a human clinical setup thus facilitating the transposition of experimental data from animal to human.

Use of biometry and keratometry for determining optimal power for intraocular lens implants in dogs.

Axial length and corneal curvature were determined by use of A-scan ultrasonography and keratometry on both eyes of dogs of various breeds, sizes, and ages. Mean axial length was 20.43 +/- 1.48 mm; axial length was not related to age or sex, but was significantly greater (P = 0.047) in dogs of larger breeds. Mean corneal curvature was 39.94 +/- 2.61 diopters. Dogs of large breeds had significantly (P less than 0.001) flatter corneas. Mild, roughly symmetric astigmatism was detected in a majority of dogs. Use of mean values in a theoretic artificial intraocular lens power equation suggests that aphakic dogs require an implant of approximately 40 diopters to achieve emmetropia.