The Rabies battle continues, in my backyard and yours.

I have posted about the new strain of rabies virus associated with bats but also capable of causing outbreaks in other species such as foxes and skunks a couple of times. There have not been many cases reported in carnivores this year, probably due to the wildlife vaccine program which they did last year. This program involves oral vaccines distributed for foxes, coyotes and raccoons, and a trap and vaccinate program for skunks (unfortunately the oral bait vaccine is not effective in skunks for some reason). The dedicated personnel of the USDA wildlife services rabies management program get the lovely job of trapping and vaccinating skunks in Northern Arizona again this summer to prevent the spread of rabies virus from bats into terrestrial animals again.
Currently they are vaccinating skunks in my neighborhood. I found a trap about 100yards away from my house today, complete with a small skunk hiding in the brush near the trap waiting for darkness before traveling away from cover again.

This skunk was very calm and sleepy during the middle of the day, waiting for nightfall to resume it's normal foraging.

 The ear tags indicate that this skunk has been vaccinated against Rabies.

This program is an interesting example of how science based veterinary medicine can improve the lives of both humans and  animals. Eliminating terrestrial rabies would reduce the risk of exposure for both wild and domestic animals and humans as well. If you have a program like this going on in your area, be sure to express your appreciation of the sometimes unpleasant and nearly always under appreciated work that these people are doing on your behalf.

Rabies vaccine fears and relative risk.

People are often not very good at assessing relative risks. This can be expressed as a fear of flying, even though the relative risk of dying in a car accident on the way to the airport is probably much higher than the risk of a commercial airline crash. Two papers published in the September 15th issue of JAVMA (Rabies surveillance in the United States during 2008, Blanton, et. al. and Rabies in vaccinated dogs and cats in the United States, 1997-2001, Murray, et. al.) and a post and discussion on Dolittler concerning these papers illustrates how the relative risk of side effects of a vaccine versus the risk of the disease and related consequences. The comments related to the post are particularly revealing, and I believe show how veterinarians and their clients sometimes approach an issue from different angles and can end up talking past each other, especially when a client may be mistaking the relative risks involved.

So what are the risks of vaccination versus the risk of disease as illustrated by these two papers and the discussion on Dolittler?

Risks related to vaccination mostly involve adverse effects of vaccination. Adverse effects include allergic reactions, delayed reactions such as granulomas at the injection site and then the well-known and well-publicized vaccine associated sarcomas which occur mostly in cats, but can happen very rarely in dogs.
Most of these adverse effects are treatable and/or preventable (allergic reactions) and may happen a few times in 1,000 vaccinations. More serious life threatening reactions to vaccines are very rare, and many vets may see very few in their career. Vaccine associated sarcomas in cats may happen in one in 1000 cat to 1 in 10,000 cats over their lifetimes, depending on which study you would like to read. These sarcomas can be very difficult to remove depending on the location they form in, and can be caused by inflammation not related to vaccination. There are newer vaccines for cats that do not have the adjuvants suspected of causing sarcomas to form.
Some other serious diseases and problems such as generalized allergies, autoimmune diseases and "vaccinosis" (a general term for ill health blamed on vaccines that does not have any real meaning or definition) have never been clearly linked to vaccines and are probably not directly or specifically caused by vaccines.

What is the risk of any given pet being exposed to Rabies? This risk may be higher than most people think. The first Rabies surveillance paper shows that Rabies exists in wildlife in every state except Hawaii, and that various bat strains are the most widespread type. There are also regional variations-Raccoon rabies along the east coast, several skunk variants in the midwest, southwest and California, and fox variants in the southwest. A new strain of bat rabies has recently made the jump to skunks and foxes in Arizona. Canine rabies strains have been eradicated in the U.S. due to vaccination and animal control efforts, so all cases of rabies in domestic animals come from wildlife. Any animal that goes outside at all is at risk of being exposed to rabies. Since bat rabies is so widespread, it is possible for a pet to be exposed anywhere bats occur. Rabid bats have an annoying habit of turning up in strange places, including inside homes, so keeping cats indoors is no guarantee that they will never be exposed.

Another risk of having a pet that is not vaccinated against rabies or that is not current on rabies boosters is what could happen if the pet happens to bite someone or is exposed to a rabid animal.
Animal bites treated by doctors legally have to be reported to local health departments, so that appropriate follow up and rabies preventative treatment can be done in a timely manner. In the second JAVMA paper, reports from 20 states on dogs and cats tested for rabies between 1997 and 2001 are listed. There is no way to test a live animal for rabies infection, so all of these animals were euthanised because of a bite or died of neurologic disease that raised a suspicion of rabies. During that period these stated tested 78,669 dogs and 92,318 cats for rabies. 248 dogs (0.32%) and 685 cats (0.74%) tested positive. many of these animals may have been strays, but some of them were pets that were not vaccinated. 13 dogs and 22 cats had a history of rabies vaccination, but only 2 dogs and 3 cats were classified as currently vaccinated. As with any vaccine, failures can happen, but are very rare. This also indicates that one vaccine or an extended schedule of rabies booster does increase the risk for rabies infection.
If an unvaccinated pet bites someone, the local health department can have the pet euthanised and tested for rabies if they think they need to. This is a risk to the pet that is unrelated to the actual risk of rabies infection, as shown by this study-over 99% of dogs and cats tested for rabies were negative. Other states undoubtedly tested many animals as well, but did not agree to participate in this paper, so these numbers are probably even more dramatic across the entire country.

Some of the comments on Dollittler were common arguments many veterinarians hear. "My cats never go outside, they are always in the yard, etc." These papers show that rabies is common and widespread in wildlife, and that hundreds of unvaccinated and even a few vaccinated pets do get rabies, and tens of thousands of unvaccinated pets were killed for rabies testing over a five year period. This is the perspective veterinarians are coming from when they recommend rabies vaccines. The risk to pets and humans from rabies is real and the consequences of infection are severe. Some people who do not want to vaccinate their pets consider information like this fear-mongering, but failing to inform pet owners of these risks, along with a discussion of the rare but serious side effects of vaccines would constitute negligence on the veterinarians part.
Failing to keep a pet current on it's rabies vaccination can result in the death of the pet even if it does not get rabies. This is a result of the need to ensure that humans receive appropriate treatment in a timely manner when exposed to a potentially rabid animal and is a risk that most pet owners are not aware of. Just because a client thinks their pet will never bite anyone or will never get outside, does not mean that it will never happen. It does not mean that your vet thinks you are lying, but we understand the relative risks of vaccinating versus not vaccinating in a way that the pet owner may not.

Spread of bat-variant rabies virus in other species.

I started to hear rumors about rabies virus spreading through the air from clients today. Then I got an e-mail referencing this article from National Geographic today. Apparently the article is the source of the rumors. There are a couple of problems with the article that make it difficult for people unfamiliar with the science involved to interpret.
First, calling this a new rabies virus in the title makes people think that the current outbreak of Rabies in foxes and a few skunks in the Flagstaff area might be something new and different.
The Rabies outbreak in foxes is a bat variant rabies virus that has crossed into other species several times in the last decade in the Flagstaff area. The thing that is different about these outbreaks is that the virus seems to be better at spreading in a new species of animals than bat variants usually are.
Rabies virus has many different genetic variants that are adapted to different species. All of these variants are capable of infecting other species, and basically all mammals are susceptible to infection with rabies. Often, when an animal or human is infected with a variant of rabies from another species, the new host is considered a "dead end" because the disease is fairly rapidly fatal after the virus reaches the central nervous system and the new host may not spread the virus very efficiently. When a host is infected with a variant of rabies that is adapted to that host, it is more likely to spread to another animal. The primary mechanism of spread is by bites or scratches that are exposed to saliva from the infected animal. On rare occasions the virus can spread by oral or nasal inoculation as well. This still requires close contact with the saliva or tissues, especially nervous tissue or salivary glands of an infected animal. There are several different places around the country with different variants of rabies in their respective species.
The CDC publishes annual reports on rabies epidemiology which list the number of animals tested positive for rabies and the human cases along with the variants that caused the disease in humans. This shows that Rabies is a common disease in wild mammals, and it is not unusual for it to be spread from one species to another. It is less usual for the virus to mutate and then spread widely in the new species. Apparently the outbreaks of bat variant rabies in foxes, skunks and bobcats in Northern Arizona over the past decade is the first time that humans have observed the mutation of the virus and its spread in a new species. This has obviously happened many times in the past, hence all the different rabies variants in many different species. It is even possible that bats are the initial reservoir for all rabies viruses and occasional mutations in the virus result in new variants that are better adapted to other species of mammals.
This paper documents the original outbreak of the bat variant rabies in skunks in Flagstaff in 2001. The current outbreak in foxes is also a bat variant, and is probably the same or a similar variant as the previous outbreaks were.
The main problems I have with the National Geographic article are the author's assertion that skunks described in the paper by Leslie, et. al. were spreading the virus "passively" whatever that means. Some people in the Flagstaff area have already interpreted this to mean that rabies is being spread as an airborne virus. It is spreading in a new species, but there is no reason to suspect that the virus is not spreading through bites or very close contact just like Rabies has always spread. The other problem I have is the quote from Barbara Worgess, the head of the Coconino County Health Department that "It shouldn't be able to spread from skunk to skunk."
There is no reason that the virus cannot spread from animal to animal, it is just unusual and does create a concern for the Health Department. Unfortunately Ms Worgess seems to say things like this to the media which make it look like she really does not know what is going on.
Fortunately, this new variant of the Rabies virus can be prevented by the same Rabies vaccinations that have been available for years. The fact that bats are often carriers of Rabies is an excellent reason to keep your pets vaccinations (including cats!) up to date, and the spread of the virus in a new species is a good reason to be cautious in the woods and around any wild animal that is acting sick or agressive. People that have been exposed to Rabid foxes in the Flagstaff area have been effectively treated with standard protocols just like other exposures to other rabies variants. Any time someone has been bitten by a wild animal or exposed to a bat (bat bites can be very hard to identify due to their small size) they should seek medical attention immediately. Rabies antisera and vaccinations do not work once symptoms appear.
The Natonal Geographic article is another example of the media publishing an overly sensational, inaccurate story. No one should panic, but should take sensible precautions.