As we all know, horses are always picking-up respiratory bugs, both viruses and bacteria. They get a snotty nose, cough for a bit and then get better. We often give antibiotics, sometimes bronchodilators such as clenbuterol ( ventipulmin or dilaterol) and possibly a mucolytic for the extra snotty ones, such as dembrexine (sputolosin ) . If the infection is not clearing up as quickly as we would like then the next step is to do a videoendoscopy allowing us to thoroughly visualise the horse’s airway and to collect samples of mucus which are then examined to determine the cell types present. The sample is also cultured in the lab to see what bacteria we are dealing with and what antibiotics they are sensitive to. The cellular content gives us a good idea on the type of problem we are dealing with and helps to differentiate between an infection and an allergic lung response such as RAO or COPD. All routine stuff, and usually results in a rapid return to a healthy horse.
The case I am going to describe is not particularly sick but has proved very refractory to treatment. He is a national hunt horse that has been retired for four years and has not previously had any respiratory problems.
He developed a cough and a snotty nose so he was prescribed with a five day course of oral potentiated sulphonamide antibiotics ( Trimediazine ) and given plenty of turnout to assist with lung drainage. After two weeks there was no improvement. His lungs sounded pretty normal to listen to and he didn’t have a temperature. His blood picture was unremarkable with a normal white cell count and differential. We then endoscoped the horse; the upper airway was normal, no inflammatory response in the throat and both guttural pouches clean. In the lower airway, the trachea, there was a small pool of mucus which didn’t look particularly exciting but we sampled it anyway. To our surprise the cytology of the sample showed an extreme density of white cells both acute inflammatory neutrophils and an the much larger macrophages , essentially it was pure pus! The sample was submitted for culture but unhelpfully, no bacteria grew. This is quite common with such a high density of white blood cells because they literally kill everything locally but clearly were not capable of totally resolving the problem. So without the help of a positive culture to direct us towards the appropriate antibiotic we chose doxycycline ( Karadox ) which is a broad spectrum drug with good tissue penetration and is typically good at killing pathogenic respiratory bacteria. As there is often an allergic component of the inflammatory response in the equine lung, we opted to give the horse some corticosteroid ( beclamethasone ) by inhaler to try and reduce the degree of inflammation. We also incorporated dembrexine in the treatment plan to loosen up the residual mucus in the lung to help it’s clearance. The horse was given this cocktail of drugs for 10 days and then returned to the Clinic for a repeat endoscopy. As this was billed as a “challenging case” you will not be surprised to learn that the horse had not improved, in fact there was more mucus visible and it was just as pus-like as before in terms of dense cellular content. This case was clearly not going to plan and not responding to treatment so we decided to phone a friend or friends in the form of Prof. Celia Marr from Rossdales and Dr Tim Brazil from Equine Medicine on the move , both world renowned experts in Equine Medicine. They were both very interested in the case and both cited similar cases which had turned out to have long standing walled-off abscesses in the chest. They suggested that we should obtain images of the lungs either via an ultrasound scan or by radiography in order to rule out an abscess. Since we have recently installed a new state of the art HD radiography system at Peasebrook, we were keen to see what quality images we could obtain. As you will see from the picture below the clarity of the lung is exceptional and thankfully it does not show the presence of an abscess.
So in the light of the radiography findings, both Tim and Celia felt that we must be dealing with an extreme allergic response from the horse, despite the absence of the typical lung sounds normally present in these cases. The recommended treatment is a stronger administration of corticosteroids via the oral route for 14 days plus a strict dust free environment and plenty of turnout. This treatment is ongoing and we will report on the horse’s progress in due course. Fingers crossed that his immune system starts to cooperate with us! This case highlights that it is always best practice to scope and collect samples from horses with respiratory disease if it is not resolving quickly.