GBGB advice on Canine Haemorrhagic Pneumonia (CHP)
GBGB wishes to respond to the recent articles regarding Canine Haemorrhagic Pneumonia (CHP) in racing Greyhounds, supporting many statements whilst refuting others.
General picture of CHP
CHP is an uncommon but easily recognisable disease. The infection is characterized by a sudden onset lethargy, fever (above 39.5 ˚C / 103.1 ˚F), and rapid breathing or panting. Coughing is not a consistent sign because CHP is a pneumonia, not a bronchopneumonia. In other words it is an infection of the lungs themselves, not of the airways and lungs.
CHP is not related to or linked with kennel cough. Kennel cough will affect many Greyhounds, whereas CHP only affects one or two Greyhounds. The GBGB has investigated many cases of CHP where there is no kennel cough, and similarly kennels with kennel cough are no more at risk of developing CHP than a perfectly healthy dog. Indeed one of the distressing aspects of CHP is that it can and does affect fit Greyhounds and as such represents a shock to trainers when they see their prized Greyhound get CHP. It is true to say that CHP is more likely in the damp and cold months, but it occurs all year round unlike kennel cough which is strongly seasonal.
What causes CHP?
In about half of cases laboratory analyses isolate either Streptococcus equi zooepidemicus (Strep zoo for short) or E. coli. We have a good understanding of how Strep zoo causes CHP, but less so with E. coli because it is present everywhere. To cause CHP these bacteria must gain access to the lungs, since many Greyhounds carry these bacteria on their tonsils with no ill effects. It is most important to understand that Strep zoo needs a trigger event and that it must have access to the lungs. Trigger events can be things like long distance travel or racing, and access to the lungs is gained by being drawn down into the airways during exercise.
How does CHP progress?
CHP starts very suddenly, often with no warnings. Lethargy / off-colour / off-food are the first signs, followed within a few hours by fever and panting. Coughing is not a reliable feature of CHP, so often the only signs are lethargy, fever and panting. Affected Greyhounds die within a 6-10 hours – few cases survive more than 10-12 hours.
Can CHP be treated?
The GBGB has developed a protocol based on best practice for the treatment of CHP cases. The over‑riding requirement is for the immediate use of intravenous fluids and intravenous antibiotics for a few days, followed by three weeks of antibiotics in the food. Delays in starting the therapy (even waiting for things like X-rays and blood samples) worsen the outlook, as does use of single injections or just using a course of tablets. Unfortunately only about half of CHP cases respond to therapy, but where dogs do respond they improve rapidly and make a full recovery. They are able to race again with no further problems. Veterinary surgeons who suspect CHP cases can ask the GBGB for the protocol, or download it from the GBGB website.
How is Strep zoo spread?
Strep zoo is transmitted by dogs sniffing or licking each other, but spread by water bowls and other inanimate objects (biologists call these objects fomites) is certainly possible. Since coughing is not a regular feature of the disease, spread by the air is possibly less likely. Previous work by the GBGB in liaison with the Animal Health Trust at Newmarket has shown that between 10% and 30% of Greyhounds carry Strep zoo on their tonsils. Since the number of cases is nowhere near 10% of the Greyhound population it is thought that the dogs pass the bacteria between themselves in low doses which acts as a natural vaccination.
The GBGB has investigated over 60 cases of CHP since 2008, and very few had links with horses and none had a positive link with horses with respiratory disease. There are much stronger and far more consistent links with recent exercise or transport with many cases occurring with 36 hours of such events. Although it is feasible to pass Strep zoo between species, the strain of Strep zoo which infects UK Greyhounds is different and unique. Readers may have come across reports of Strep zoo in horses and in shelter kennels in the USA where the pattern of disease is very different from what happens within UK Greyhounds.
How many cases of CHP are seen?
Technically speaking, CHP as a disease does not spread very well in Greyhounds. Even kennel mates do not get CHP, again highlighting the difference from other respiratory diseases like kennel cough. So we are indeed fortunate that although Strep zoo spreads well, the disease it causes is very rare and restricted to one, rarely two, Greyhounds.
For any one residential kennel, only one case of CHP occurs. Rarely two cases are seen: the second case always occurs within 48 hrs of the first case. USA-style outbreaks of CHP have not been seen in the UK. The reasons for this are the facts that it is a different strain and that many Greyhounds are thought to be immune to Strep zoo. Another important fact is that CHP is only seen after periods of stress, e.g. long distance transport or racing. Thus it is only non-immune or stressed Greyhounds which develop the full disease. CHP does not occur in resting or retired Greyhounds for the simple reason that they are not stressed, so even if they have Strep zoo on their tonsils the body’s immune system can control the bacteria and thus develop immunity.
Recurrent cases on the same kennels are very rare – in other words if a kennel has had a CHP case it does not mean that kennels will be more likely to get another CHP case in the future.
On a UK-wide basis looking at 20,000+ Greyhounds, the GBGB sees 0-4 cases per month, so overall the case rate is very low making CHP a rare but significant disease.
How are the kennels controlled?
The usual principles of isolation, hygiene and staff awareness apply. The kennels will be assessed and a determination made as to whether a whole-kennel closure is needed, or whether only certain kennel blocks need to be closed. Closure is normally for 7-8 days. Specific veterinary advice is given to the trainers and cases are submitted for post-mortem examination wherever possible.
Dr Simon Gower BVSc MRCVS, GBGB Veterinary Director and Chair of the GBGB Veterinary Sub Committee;
Dr Richard Payne MA VetMB DProf AdvCertVPhys CertClinEd SFHEA MRCVS, Vice Chair of GBGB Veterinary Sub Committee.
GBGB encourages the reporting of any cases via the Helpline on 0207 822 0929.
For licensed trainers, GBGB will pay for the laboratory work.
Specific veterinary advice sheets are available here.