By Michael Watts MVB, MSc, MRCVS
Michael Watts
Cases of respiratory disease in dogs are an everyday event in in veterinary practice. They are a dime a dozen. The greyhound game in particular is vulnerable to outbreaks of respiratory disease as the dogs involved are mostly young, with fewer opportunities to come into contact with disease causing organisms and develop resistance to them. Racing greyhounds also move around the country more than your average mutt and mix with other dogs from all airts and parts. They are also, it has to be said, often under a degree of stress, which cannot help.
Most commonly problems are confined to the upper respiratory tract. Being anoraky for a moment, that means the nose and nasal passages, paranasal sinuses, the pharynx, and the portion of the larynx above the vocal cords. In human patients who stand upright these are the upper part of the respiratory tract, and from force of habit the term has also been applied to four-legged patients even if it does not make a lot of sense. Most commonly these upper respiratory infections in dogs are caused by Canine Parainfluenza Virus (CPIV), by the bacterium Bordetella bronchiseptica, or by the two infectious agents acting in concert. Think of the all too familiar Kennel Cough, a disease characterised by a hacking cough which can last for two weeks or more and which can spread through a kennel faster than you yourself can draw breath. An outbreak of Kennel Cough in a trainer’s kennels puts a huge spanner in the works and mucks up plans for racing and training for weeks, but ultimately it runs a course and dies out in time. Otherwise healthy adult dogs almost invariably recover completely in time and in the long term are generally none the worse for their experience. .
Canine Haemorrhagic Pneumonia, or CHP, is different. It is a disease that has only emerged in fairly recent years and the veterinary profession has not got all the details sussed out yet but, not to beat about the bush, it is very bad news. CHP strikes suddenly with little or no warning. Affected dogs become very sick very quickly and many die, often within hours of first falling ill. It is a disease of the lower respiratory tract, which is to say the lungs and the airways from the vocal folds backwards. The disease is characterised by the sudden onset of profound lethargy, often accompanied by a temperature in excess of 39.5oC, and laboured breathing. Affected dogs cough, and may cough up blood or vomit blood. As I said earlier, some of the ins and outs of this condition have still to be hammered out but a bacterium with the unmemorable name of Streptococcus equi zooepidemicus can be isolated from a substantial percentage of affected dogs. It can also sometimes be isolated from clinically healthy dogs kept on the same premises as affected dogs. These may be dogs who have a greater degree of immunity to the bacterium and have been infected with it without becoming ill. Alternatively they may be dogs that have had CHP in another life, survived it and remain carriers of the bacterium. It seems probably that the disease is triggered by a combination of infection with this bacterium, a lack of immunity to the bacterium and external stress factors This is work in progress, and as soon as I hear of any big breakthroughs rest assured that you guys will be the first to know.
So where do the bacteria come from in the first place? Streptococcus equi zooepidemicus is a very common opportunist equine pathogen, which causes sporadic infections of the skin, respiratory, genital and urinary tracts and joints of horses of all ages. Opportunist is the key word here. This is an organism which moves in where animal have low resistance to disease for some reason or are under stress. We know this is the case in horses, and cases have been sporadically reported in people who have had close and continuous contact with horses. It is noteworthy that in these human patients the disease tends to be invasive and severe, requiring prolonged treatment and rehabilitation, not unlike the canine cases seen recently in this country. If the bacteria can “jump” from horses to humans then presumably they could potentially transfer their affections from horses to dogs. The details remain to be thrashed out, but the smart money would not rule out some sort of a link between horses and some cases on CHP in dogs. On the other hand outbreaks of Streptococcus equi zooepidemicus respiratory disease have been recorded in dogs in local authority pounds in inner city areas where a connection with horses is hard to identify.
A vaccine against a closely related species of bacterium is commercially available for use in horses, so perhaps in the fullness time there may be a prospect of a vaccine against Streptococcus equi zooepidemicus being developed for dogs. For the present though the best advice I can give is not to muck about and if you see signs of disease of this kind in any of your dogs seek professional help as a matter of urgency. Time is not on our side.
©UnderTheRadar 2019
