More on dogs and Hendra virus

Neil Fearon and his family have lost three horses to Hendra virus, and are concerned about one other. They are now dealing with the implications of their dog, a Kelpie named Dusty, having tested positive for Hendra virus antibodies in its blood. As I mentioned in yesterday's post, the presence of antibodies in the blood of this dog, detected during voluntary testing as part of the outbreak response, only indicates that the dog was exposed to the virus. Viral shedding was not identified, suggesting that the exposure was a prior event and that an active infection was not present. Despite this, government authorities are requiring that the Hendra antibody-positive dog be euthanized.

Poor communication and mixed messages are often the cause of problems during outbreak management, and this seems to be the case here. Based on the news reports, there are some pretty concerning issues.

Testing of the dog was voluntary and the owner was not notified that euthanasia would be required if the dog tested positive.

  • This is rather unethical. People need to understand the implications of outbreak control measures. It's not fair to have such an aggressive response to a voluntary test without proper notification.

Mixed messages are being given about the risk the dog poses to the family.

  • Authorities want to euthanize the dog, indicating they must believe there is some risk. However, the owner is very concerned about his 11-year-old son who has slept with the dog in his bed for the last few weeks. Yet, ABC news indicates authorities reassured Mr. Fearon that the risks are minimal. If the risks are minimal from that type of prolonged, close contact during the period when the dog may have been actively infected, it's hard to justify euthanasia after the fact on the basis of the dog posing a risk to people or animals (especially when the virus is endemic in the bat population in the area).
  • Why euthanasia is being required seems to be unclear. While fear of Hendra virus shedding makes the most sense, Queensland's chief vet has stated that the dog will be euthanized as a precaution because "As a result of that infection, it may make it aggressive." It seems rather strange to euthanize a dog because of concern that an infection (which may not be active) might cause aggression, with no evidence that disease will occur or that it can cause aggression in dogs. Quarantine and observation would make more sense. There are a lot more dogs that are prone to aggression wandering around Australia.

This type of action drives things underground.

  • When overly-aggressive actions are used, and people either don't agree with them or don't understand them, faith in the system decreases. What's the likelihood that people are going to allow their pets to be tested now? I assume it's a lot lower now that they've seen what will happen. So, the ability to determine exposure of other species and the potential risks from other species will be impacted.

Hendra virus is not something with which to play around. It's a very serious disease and one must err on the side of caution. How far you err on the side of caution is the question, and it's a hard thing to determine. It's easy to be very strict when setting rules, and fear of liability or fear of making a subjective decision often override logical thought and discussion.

As a somewhat informed outsider, I have a hard time supporting mandatory euthanasia for a dog that has evidence of previous infection but no evidence of active viral shedding. Yes, no test for virus shedding is 100%, but a pretty high level of assurance can be obtained and the dog can be quarantined for further testing. There's no indication from laboratory studies that I know of that dogs (or other non-bat species) can become longterm carriers of the virus. The owners should be involved in the decision making process and be given enough information to understand the implications of keeping the dog, the risks that might be present, and what they can do to reduce the risks. Government authorities need to clearly state their concerns and the evidence supporting them. With that, it's easier to make a logical plan that protects the public but is also appropriate for the animal and its owners. If the risk is deemed to be real and/or the owners are not willing to accept some degree of risk, then euthanasia is reasonable.

"Kill the dog" is an easy knee-jerk response. I simply don't see the evidence supporting it. Is it possible that authorities have a true reason to be concerned? Sure, but if so, that indicates another communication problem. If there is really evidence that this dog is a concern, this needs to be clearly communicated so people understand what's happening and why such drastic actions are being taken.

(click image for source)

This Worms & Germs blog entry was originally posted on equIDblog on 27-Jul-11.

Hendra virus in a dog

Adding a new twist to the already very concerning situation in Australia, Hendra virus infection has now also been identified in a dog. It's been a bad year for Hendra virus in Australia, with larger numbers of cases of this highly fatal disease in horses in a geographic range that seems to be expanding. Spread by flying foxes (fruit bats), Hendra virus predominantly infects horses, but can be transmitted to people working with infectedhorses.

The Australian Animal Health Laboratory in Geelong has now announced diagnosis of Hendra virus infection in a dog. The dog is from a quarantined farm in Queensland where the virus has been identified in a horse. The dog was healthy and was tested as part of a standard policy to test dogs and cats on infected farms. It's great to see this approach being used, since it helps identify other potential sources proactively - something that is often overlooked in outbreak investigations that focus only on the main species that are already known to be involved.

In this case, the dog had antibodies against the virus in its blood. That means that it was exposed to the virus and mounted an immune response. It doesn't indicate whether it was exposed recently or in the past. Two tests for the virus itself were negative, suggesting that the dog's immune system eliminated the virus (or that the virus isn't really capable of surviving for long in a dog). This is a good news/bad news scenario.

Bad news:

  • Dogs can be infected. It increases the range of known susceptible species.
  • If dogs can be infected and shed live virus, then they could be a source of infection for other individuals, including people.
  • The dog wasn't sick. This might sound like strange "bad news," but healthy carriers of infectious diseases are harder to spot and control than ones that are sick.

Good news:

  • The dog wasn't shedding the virus. That's critical since if dogs can be infected but not infectious (i.e. if they can carry the virus but not transmit it), then they are of limited concern.
  • They have been testing farm dogs and cats as a routine measure, and this was the first positive. Infection of pets therefore must be relatively uncommon even on farms where the virus is active.
  • The dog wasn't sick. While it's only one case and doesn't guarantee dogs won't be affected clinically, this might suggest that dogs just occasionally get exposed with no disease. Since it's highly fatal in other species, that's a good thing.

What should be done based on this?

  • Probably not much more than should have been done before this finding, but it's a good reminder about the potential involvement of other species.
  • Dogs and cats should be kept away from fruit bat roosting sites.
  • Dogs and cats should be kept away from infected horses.
  • If a farm is quarantined because of Hendra virus, dogs and cats should be tested and quarantined. Quarantining the animal while testing is underway helps reduce the risk of an infectious dog or cat (should that occur) transmiting the virus to people on the farm, or wandering away and exposing other people or animals.
  • Animals of any type in areas where Hendra virus is active that get sick with signs that could possibly be consistent with Hendra virus infection should be tested.

This should also be taken as yet another reminder that infectious diseases are unpredictable. Considering the potential involvement of different species in a proactive manner as was done here is critical.

Image: Bay Horse and White Dog by George Stubbs (1724-1806)

This Worms & Germs blog entry was originally posted on equIDblog on 26-Jul-11.

Human rabies in New Jersey

A 73-year-old New Jersey woman has died of rabies after being bitten by an infected dog. The woman was visiting Haiti in April when she was bitten, and she developed signs of neurological disease in late June. Family members and healthcare workers are being assessed to determine whether they may have been exposed to rabies during care of the woman. If so, post-exposure treatment would be started.

Rabies is a devastating but almost 100% preventable disease. While rare in most developed countries, canine rabies is a huge problem internationally and kills tens of thousands of people every year. The main reason it kills so many people is because of inadequate access to proper post-exposure treatment or failure to seek medical care. Timely access to post-exposure care can virtually guarantee that a person won't get rabies.

Why this woman didn't get post-exposure prophylaxis (I'm making the assumption that she didn't) isn't reported, and it could be because of patient or healthcare factors such as:

  • Assuming a minor bite isn't a big deal.
  • Not thinking about the potential for rabies.
  • No access to adequate heatlhcare.
  • The physician not thinking about rabies.
  • Inadequate or no supply of rabies vaccine (for post-exposure treatment).

All of these problems can occur.  Education of the public and medical personnel, as well as ensuring adequate access to rabies vaccine, are critical to prevention.

More information about rabies can be found in the Worms & Germs Resources page.

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Bat cull for Hendra virus prevention?

As Australia faces a particularly bad year for Hendra virus, with possible expansion of the range of this serious disease, there have been calls for a mass cull of flying foxes (fruit bats).  These bats are the reservoir of the virus but also a protected species. The virus lives in the bats and is spread mainly through their urine. Horses that are exposed to bat urine or feces (e.g. grazing under a tree where bats are roosting) can become infected and then serve as a source of human infection. Being a highly fatal disease for which there is no available vaccine, looking at ways to reduce exposure to the virus is critical.  When you have a wildlife-associated disease, questions about trying to eliminate the wildlife source often arise.  Any discussion of culling wildlife leads to intense debate, and this situation is no different. Some people support culling bats in areas around people and horses, while others are opposed on various grounds, including a lack of evidence that it will be effective.

Can fruit bat numbers really be decreased? A lot of bats would have to be killed to have a significant impact on the population. Bats can reproduce quickly and migrate readily, therefore a single cull may have only a limited and short-term effect. A good understanding of the dynamics of the bat population is required to determine how many would need to be killed in a given area to have any significant impact. As Biosecurity Queensland's chief veterinarian RIck Symons stated "Culling is against government policy. I believe in terms of biosecurity it's counterproductive, because it does stress flying foxes and they're more likely to excrete (the virus). It could be filled by another bat colony the next day and if you're moving them on, you're moving it on to somebody else and it's somebody else's problem, so that is not the solution."

Will a cull actually achieve anything? Even if effective at reducing bat numbers (probably just in the short term), culls don't necessarily have an impact on disease rates. All bats would not be eliminated, and it's unclear whether there is a critical mass of bats that is required to transmit infection or whether a small number of bats distributed across the same region would be as likely to result in infections. Small or temporary decreases in bat numbers may have no effect.

What unintended consequences might occur if a cull is effective at reducing bat numbers? Removing an animal from any ecosystem has an effect, and it's important to be confident that that effect isn't accompanied by problems of its own. I don't know enough about fruit bat ecology to say much here, but if this species is greatly reduced, are there other species that will come and occupy that ecological niche, and might they be associated with problems of their own? Careful scientific study can help to figure this out in theory, but you can never be certain.

Are other control measures, such as removing roosting sites from pastures and other bat avoidance measures, being adequately used? Culls should only be considered when other measures have failed, but it can be difficult to ensure or enforce compliance with these other measures. Certainly, people in endemic areas should remove trees in which bats roost from pastures. However, not all Hendra cases are associated with identifiable roosting sites.  For example, one affected Queensland farm does not have any fruit bats residing on the property, but it lies along a common flight path for the bats.

It's easy to talk about avoiding a cull when you're not in the heart of the Hendra epidemic, and I understand the reasoning behind the calls for a cull. Hendra is a devastating disease that's a threat to both horse and human health, and it's unpredictable - and that's scarey for a lot of folks. People that have been exposed face an incredibly stressful period while they wait and see if they've been infected with a virus that kills in ~50% of cases. A vaccine is probably still a couple of years away, leaving a period of continued risk and stress. With such a serious disease, considering culling is reasonable. However, it can't be a knee-jerk reaction to public outcry. It needs to be based on sound science to ensure that if it's used, it will be effective. The impact on this protected species also can't be ignored.

This Worms & Germs blog entry was originally posted on equIDblog on 19-Jul-11.

Rabies quarantine lawsuit

A Chapel Hill, North Carolina woman is suing Orange County in response to quarantine of her dog because of possible rabies exposure. This lawsuit highlights some of the inconsistencies in application of current rules, along with some misunderstandings.

In February, her dog Russell was barking at something under her deck, and that something ended up being a raccoon with rabies. There's no evidence of a fight or contact, but it can't be ruled out. Because of this, the dog was considered potentially exposed. Russell was overdue for his rabies booster, so a strict six-month quarantine was required, and the county required that this be done at an approved facility, not in the home. (The alternative option was euthanasia.)

  • The lawsuit is based on the inconsistent application of the rules by various counties. The owner is seeking permission to quarantine the dog at home. This is allowed in many regions, provided there is confidence that the owner is responsible enough to properly quarantine the animal.
  • It's a reasonable argument that's based on subjective and variable application of rabies guidelines. Certainly, formal quarantine in a facility offers more containment. The question is when household quarantine is appropriate, in terms of the animal's risk of exposure and the ability of the household to properly quarantine the animal.

Some other highlights:

Russell was overdue for his rabies vaccine by 46 days.

  • Dogs don't immediately go from protected to unprotected. Certainly, we want animals to be up-to-date on their vaccines, but some thought needs to go into dealing with potentially exposed overdue animals. The NASPHV Rabies Compendium states "Animals overdue for a booster vaccination need to be evaluated on a case-by-case basis (e.g. severity of exposure, time elapsed since last vaccination, number of prior vaccinations, current health status, local rabies epidemiology)."
  • Knowing the age of the dog and the number of previous vaccines would help, but the news article reports vaccinations (plural), suggesting that he's been vaccinated more than once in the past. In a dog with a relatively low index of exposure that was only overdue by 46 days, it would seem reasonable to consider it protected and treat it as vaccinated (although it's hard to say this definitively based on a news report that doesn't give the whole story). It's a critical point because considering the dog up-to-date would only result in a 45 day observation period as opposed to a strict six-month quarantine. 

The owner's veterinarian stated that research shows that an animal that is vaccinated regularly is protected for many years, if not a lifetime.

  • Yes and no. Vaccination is quite effective and in most animals probably confers long-lasting protection. However, I'm not aware of research that really shows this. This isn't a disease where we have good research data about duration of effect of vaccination. I suspect that most dogs that have been regularly vaccinated are well protected. Most does not equal all, and with a disease like rabies, you have to be quite sure.

A rabies antibody titre was measured. This is a blood test indicating the level of anti-rabies antibodies. The veterinarian indicated that the titre showed Russell is currently protected from contracting rabies.

  • Unfortunately, no. TItres tell you antibody levels, but we don't have good data about what is actually protective. Higher is better, but we can't say a certain number is absolutely protective. Back to the NASPHV guidelines: "Titers do not directly correlate with protection because other immunologic factors also play a role in preventing rabies, and our abilities to measure and interpret those other factors are not well developed. Therefore, evidence of circulating rabies virus antibodies should not be used as a substitute for current vaccination in managing rabies exposures or determining the need for booster vaccinations in animals". That statement was echoed by North Carolina's state public health veterinarian, Dr. Carl WIlliams.

This is a tough situation. In many circumstances, home quarantine is a reasonable option. It's easier on everyone involved, by not separating the dog from the household. It's also less expensive. However, it inherently comes with some degree of risk to the household and the community. It's only a reasonable option when it's certain that people will take "strict quarantine" seriously, and truly quarantine the animal. That's hard to assess, and regulatory bodies are presumably afraid of assuming liability should they allow someone to quarantine an animal at home and something bad happens (e.g. it develops rabies and exposes people in the household, the owners take it outside where it encounters other animals or people, it escapes...). Determining whether someone can and will properly quarantine an animal isn't easy, and those issues presumably lead some people to err on the side of caution, and require formal quarantine at an approved facility.

The easiest way to avoid all this: Ensure your pets are properly vaccinated.

Puppy seizure on Vancouver Island

The British Columbia SPCA has seized 71 dogs, including 43 puppies, from a Vancouver Island woman and is planning on recommending cruelty charges. The dogs were seized from Green Acres Kennels because of various health problems that were believed to be the result of bad breeding and inadequate care. Numerous congenital abnormalities were identified, strongly suggesting poor breeding practices. Other problems like infections and severe dental disease were found, including one dog that will need most or all of its teeth removed.

As reported by The Province, SPCA Manager of Cruelty Investigations Marcie Moriarty explained "A good breeder would never breed those dogs. It's not fair to the dogs and it's the public who suffers when they have to spend thousands of dollars on vet bills."

Owner Nancy Kitching responded with the ever informative "That's a bunch of crock. The dogs are not in distress."

There are a number of problems associated with buying animals from poor breeders. Beyond the ethics of supporting these kinds of practices, poorly bred and raised puppies tend to be at increased risk of various health and behavioural problems. They also may be at higher risk for carrying a range of infectious agents, particularly bacteria and parasites.

Here are some red flags when it comes to identifying problem breeders/puppy mills:

  • Lots of dogs available at any time. Most good breeders rarely have puppies available on demand.
  • No scrutiny of potential buyers. Good breeders want to make sure their puppies go to good homes. If the only thing you need to show to get a puppy is your wallet, that's a bad sign.
  • You don't see all the dogs that are advertized and/or the parents. If there's a barn in the backyard, lots of puppies for sale and no dogs in sight, the dogs may be all caged out of the way. Ask to see the parents and the rest of the litter.
  • They won't tell you the name of their veterinarian. A good breeder has a good relationship with a veterinarian. A bad breeder may do a lot of their own "vet" work (often with internet-sourced drugs and vaccines), shuttle between multiple veterinarians and have a poor reputation amongst the veterinary practices in the area.

Buying a puppy should be a 10-year-or-more commitment, so it's worth doing right. If someone wants a dog from a breeder, it's better to put the time, effort and potentially more money into doing it right, because a bad choice can result in lots of extra cost, frustration and heartache.

As for Ms. Kitching, she's not getting the dogs back because she can't afford the costs associated with covering the legal, boarding and veterinary costs. However, she has plans on offering laser treatment for dogs with skin problems (which sounds like practicing veterinary medicine without a license) and may still 'dabble' in breeding. Beware.

Staph food poisoning...possible pet reservoir

When it comes to public health concerns about staphylococcal bacteria from pets, most of the attention gets paid to methicillin-resistant strains like MRSA. That's not surprising considering how important MRSA is in human medicine. However, staph that aren't methicillin-resistant can also be a problem, since they can cause the same types of infections that resistant types can (they are just easier to treat). Another issue that often gets overlooked is staphylococcal food poisoning.

Staphylococcal food poisoning is one of the most common foodborne illnesses and results from growth of certain strains of staphylococci in poorly handled or stored foods. If staph get into food and the food is kept at improper temperatures, the bacteria can grow. If the strain of staph that's in the food is one that can produce enterotoxins, these toxins can accumulate in the food at high enough levels to cause food poisoning when eaten. In most cases, people are probably the origin of enterotoxin-producing staph that contaminate food, but pets are another possible source.

A recent study in Vector-borne and Zoonotic Diseases (Abdel-moein et al 2011) looked at enterotoxigenic staph in 70 dogs and 47 cats. Swabs were collected from the mouth, nose and wounds. Nasal swabs were also collected from 26 people. The researchers isolated enterotoxigenic Staphylococcus aureus (strains of S. aureus that possessed genes for enterotoxin production) from 10% of dogs and 2.1% of cats, as well as 7.7% of people. Most of the positive samples from pets were oral samples.

This study shows that dogs and cats can be potential sources of strains of S. aureus that cause food poisoning. Since the staph are often in the animals' mouths (and therefore presumably shed in saliva), animals can potentially contaminate food with these enterotoxigenic staph fairly easily, but it's unknown how often this occurs.

Prevention measures are pretty basic but should be considered, including:

Exotic pet problems

I've written numerous times about risks (mainly infectious disease risks) associated with some types of exotic pets. I'm not against all exotic pets, but I am against keeping improper pets and doing so in improper situations. The latter largely involves keeping species at high risk for certain pathogens like Salmonella in households with high-risk people (e.g children under five years of age and people with compromised immune systems). The former involves keeping pets that are just not appropriate as pets because of they are large, hard to care for or venomous, or where keeping them in captivity is otherwise risky to either the owner or the pet.

Some good examples of these issues were reported this week:

  • English snake "expert" Luke Yeomans died after being bitten by one of his pet king cobras. He kept 24 snakes in a compound behind his home and was planning on opening the space up to the public. He had stated that the trust he had built up with the snakes by feeding and caring for them ensured they would not turn on him. Famous last words.
  • A South Dakota man was bitten by his (or a visiting relative's... there's some controversy) pet copperhead snake. Along with what was characterized as an "exceedingly painful bite" he could face criminal charges for owning a dangerous animal. Fortunately, copperhead bites are rarely fatal, but they are far from pleasant. One expert described it as "go ahead and light your hand on fire and put the fire out with a hammer for several weeks."
  • A Florida man (note a gender bias here?) was bitten by his African Puff Adder. Neighbours heard his screams of "Help, my fingers are turning black!" as the ambulance arrived. Fortunately, a local serpentarium met them at the hospital to provide anti-venom to counteract the venom from this somewhat small but bite-prone snake that accounts for more than 50% of snake bite deaths in Africa.
  • A Putnam Lake, New York woman was found dead in her bedroom, with the prime suspect being a pet Black Mamba, one of 75 snakes she and her boyfriend kept. Black Mambas are described as one of the fastest and most venomous snakes in the world, a great combination for a predatory snake, not a good combination for a pet.

Some people may argue that these incidents are Darwin-in-action. However, while people have some degree of right to be stupid, they don't have the right to put other people at risk. There are too many instances of dangerous exotic pets escaping, with potential risk of exposure of members of the general public. At the moment, Ipswich, UK police are on the search for a 7.5 foot boa constrictor that's on the loose. They've warned that children and pets should be kept indoors, particularly since the owner describes the snake as "unfriendly" at the best of times and, having last been fed 3 weeks ago, "is due a feed." The risks to the public are limited, but people have been killed by pet constrictors in the past, so erring on the side of caution and awareness is justified.

Yes, exotic pets can be interesting and unique. People are sometimes attracted to something new and different, but often it's the 'look at me!' aspect of having something completely different. However, novelty should not be a justification for keeping pets. Our ability to safety and humanely take care of them, and manage potential risks to the public have to be part of the equation.

Image: A Black Mamba (Dendroaspis polylepis) (source: http://en.wikipedia.org)

Record settlement for pet store-associated infection

An Irish woman has won a record, multi-million Euro settlement after developing severe disease while working at a pet store. Patricia Ingle was a healthy 19-year-old when she was working in a Limerick, Ireland pet store. Then she developed psittacosis, an infection caused by the bacterium Chlamydophila psittaci, which she most likely contracted from a cockatiel at the store. It doesn't sound like the source of infection was confirmed, but the bird-associated nature of the bacterium (and presumably no other high-risk source of infection for the person) and the timing of disease with respect to contact with the cockatiel, are strongly suggestive. 

Exposure to C. psittaci is an ever-present risk when working with psittacines, especially when they come from various sources and are mixed and stressed, as often occurs in pet stores. Human infections are rare, and they are usually treatable if diagnosed and managed properly. Usually, flu-like disease develops in people, however Ms. Ingle developed severe and permanent neurological disease (malpractice in management of her infection was also alleged).

This is yet another example of the need for proper education and training. Not all infections are preventable, and not all infections indicate liability. If this store had a proper training program in place, adequately informed staff of potential risks and had sound protocols in place to reduce the risk of exposure, it would have been possible to argue that this was an unavoidable infection in someone that knew the risks. In the absence of proper training, education and protocols, however, there's no way to successfully argue that any infection was not preventable, and the liability should shift to the employer. Hopefully this is a wake-up call for pet stores (as well as other facilities like veterinary clinics) that while you can never eliminate infectious disease exposure, you have a moral and legal requirement to take practical measures to protect staff, visitors and other people.

Urinary tract infection treatments guidelines: Dogs and cats

Urinary tract disease is a common reason for use (and misuse) of antibiotics. In veterinary medicine, one thing that we lack is clear clinical guidelines (particularly regarding antimicrobial use) to help manage specific types of diseases. In human medicine, there are some excellent guidelines of this kind (e.g. the Infectious Disease Society of America guidelines) available for a range of diseases, and these can greatly assist with proper management of cases.

Because of the lack of veterinary guidelines, the International Society for Companion Animal Infectious Diseases has started a guideline development program. Using a committee of international experts in the fields of infectious diseases, internal medicine, microbiology and pharmacology, from both human and veterinary medicine, and extensive discussion, debate and revision, specific treatment guidelines are being developed for different types of infectious diseases. The first set, Antimicrobial Use Guidelines for Treatment of Urinary Tract Disease in Dogs and Cats, has now passed peer-review and the guidelines have been published in Veterinary Medicine International, an open-access journal available to all veterinarians.

To download the guidelines, you can also click here.