Herd Immunity, Whooping and Kennel coughs

Herd immunity is the protective firewall you enjoy when enough of your social circle is vaccinated. Even if you’re susceptible to a disease, you can’t catch it, because there isn’t anyone to give it to you. Let’s get our heads around the concept, and look at Whooping Cough in man and Kennel Cough in the dog..

cherax destructor (yabbie) eggs .

Historically, when plagues were common and vaccinations new, blanket coverage demanded mandatory vaccination of all citizens. Back then, the social contract was strong and there was less talk of the personal right to decline vaccination. Nowadays, it’s a matter of informed consent and media-driven, public opinion can easily tip the scales, leading to falling vaccination rates, decreased herd immunity and the return of epidemics.

Contagious diseases love urbanised and social populations. Whether you’re a layer hen, caged with 100,000 others, or one of 10,000 in Shanghai apartment block, the more contact with your neighbours, the greater the risk of an epidemic.  Add international air travel and highly contagious, airborne diseases like H5N1 become an inevitability rather than possibility.

Like bushfires, dependent on sufficient combustible material, epidemics can only be sustained when the percentage of unvaccinated individuals rises above a threshold level. The incidence of most diseases will drop to low, smouldering levels, and outbreaks prevented, if vaccination rates of 85+% are maintained.  The higher the population density and the more contagious a disease, especially if airborne, the higher the percentage required.  The graphic below is the most eloquent I could find.

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Diagram from the National Institute of Allergy and Infectious Diseases.

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Infectious coughs

There are many historic examples of once-controlled disease reemerging as a result of decreasing herd immunity.   Most recently, in Australia, the small number of kids whose parents decided against Whooping cough immunisation were doing just fine until their numbers grew beyond 8% of the school population. Now we see an old disease reappear and kill once again. More on vaccination falling victim to it’s own success, here.

An interesting animal comparison is Kennel Cough. Caused by Parainfluenza virus and Bordetella Bronchioseptica, a bacterial cousin of the Whooping cough pathogen, this upper respiratory tract infection is easily spread by aerosolised droplets, sneezed or coughed by infected dogs. Incubation period is 3-7 days; duration of coughing, 3 days to 3 weeks.

As a disease that usually resolves without treatment, with an extremely low mortality rate, Kennel cough is one inoculation that can be hard for a vet to sell. Doctors experience the same dilemma with flu vaccination in man.  Frustratingly, the ease of spread amongst social populations (beach, park, street, kennel), coupled with the low vaccination rates in some areas, makes Kennel Cough a very common disease.  If a dog suffers only mild symptoms, their owner’s decision against vaccination seems vindicated; those with a severe bout may regret skipping the annual kennel cough jab.

In contrast to Whooping cough, localised epidemics of Kennel Cough still frequently occur when vaccination rates are 100%, in boarding kennel populations. Immunisation against Kennel Cough is not 100% effective, prompting many owners to question it’s value, although it’s uncertain how bad things would be if kennels were to relax their rules.

Pet owners who return from holidays, to be reunited with a coughing dog are sometimes dismayed their inoculations didn’t work, or believe the kennel to be negligent. In this situation I try to reassure: dogs that catch Kennel Cough, despite their immunisation, usually suffer a milder form of the disease, with less coughing, for a shorter period. Those seeking recompense from kennels don’t have a strong case. Short of individualised biohoods for each dog, there isn’t much a kennel proprietor can do to prevent an outbreak.

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RECOMMENDATION

  • Your decision-making surrounding vaccination shouldn’t be isolated from the reality of our increasingly crowded cohabitation of the planet, and our responsibilities to the collective this raises. It’s important we keep herd immunity levels, especially for life-threatening diseases, above threshold levels, to avoid resurrecting plagues of the past. Parvo, Distemper, Calicvirus and Herpes are all waiting in the wings. For more on disease incidence see Google-mapping infectious disease.
  • If times are tough, and you can’t afford to vaccinate your dog, it’s probably OK to temporarily bludge off the immunity of your neighbours. If, however, you foolishly proselytise, convincing the entire community inoculations are unnecessary, it’s possible your actions may kill half the neighbourhood dog population with a single outbreak of Parvo.
  • Annual kennel cough vaccination is of greater priority in dogs who

1. Board at kennels
2. Socialise often, even if only briefly, in well ventilated environments like the beach
3. Live in a holiday destination, with a constant flow of dogs passing through town
4. Suffer preexisting cardiorespiratory disease (heart disease, bronchitis, collapsing trachea)
5. All those short-faced dogs that can barely breathe when healthy.

1, 2 & 3 increase risk of contracting disease, 4 & 5 increase disease impact.

  • Request an intranasal vaccine if you’re looking to maximise immunity, and minimise potential side effects of kennel cough immunisation (dribbled into the nostrils).

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7 Responses to “Herd Immunity, Whooping and Kennel coughs”

  1. Nicole Bryant says:

    What a fantastic explanation for everyone to read and be able to understand. With the recent bout of kennel cough to sweep mainly through Suffolk Park for quite a few months (beach going pooches), it only makes sense to cover our loved furry friends against these diseases.

  2. matt says:

    I agree. I’m usually a little sceptical of KC vaccination, but I saw so many severe cases this year, most caught on the beach. I started to think of our suburb, with all the peak season holiday rentals, as one huge open plan boarding kennel.

  3. gabagooligonk says:

    In my experience Dr Matt, the intranasal Kennel cough vaccine seems to be much more effective, it causes far fewer adverse vaccination events than the subcutaneous vaccines and seems to confer greater immunity. Similarly as it stimulates local production of antibodies on the surfaces of the respiratory tract it prevents the infection from establishing at all. A fabulous vaccine by most accounts. Much better than the conventional vaccine it seems.
    What a wonderful resource this website is Dr Matthew,
    Yours sincerely,
    The Reluctant Registrar

  4. matt says:

    You’re right, Richard. The adjuvants required to make subcutaneous Bordetella vaccines effective are responsible for many of the local adverse reactions we see. The intranasal vaccine only had 6 adverse events reported in 2008, with over a hundred for the injectables. Without a tally of the total number of each type given, it’s hard to compare these figures, however. You’re right about mucosal immunity too.

  5. Alan says:

    How should you look after a dog that’s got Whooping/Kennel Cough. Is it OK for him (in our case) to go in the water? What about sleeping outside after spending the evening in front of the fire? He’s not in a draught but the nights are cool. He’s had it for 1 1/2 weeks.

  6. becky says:

    I was told that giving the kennel cough shot to your puppy dog was not a very good idea as you could make him more sick, especially if your puppy was not in a kennel or with other infectious dog.

    What do you think? I decided not to give him the shot but I’m still nervous about my decision.

    rebecca

  7. admin says:

    the intranasal vaccine, dribbled into nostril, rarely causes dogs to become unwell. The injectable one can cause local reactions at injection site.

    Yes, if your dog is antisocial, the risk of catching KC is reduced and, like flu vaccination in us humans, sometimes the risk of preventative side effect is greater than risk of the disease.

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