Worms and Germs Blog : Animal Health & Diseases : University of Guelph : Ontario Veterinary College : Zoonotic Diseases : Guelph, Hamilton, Ontario

This comic, based on actual (and unfortunately common) events, was developed by Los Angeles County Veterinary Public Health. It's a good example of novel ways of communication regarding zoonotic diseases. More information from Los Angeles County Veterinary Public Health (and apparently future editions of Rabies Tales) can be found on their website.

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Last fall, I wrote about rabies exposure in a Montana school. The full story has just been published in CDC's Morbidity and Mortality Weekly Reports. The brief version of the story is:

• Parent finds a dead bat carried in by the family cat and, for reasons known only to him/her, puts it in a jar.
• The next day, the parent takes the bat to a school, takes it out of the jar, and presents it to 8 classrooms full of children. Many students, teachers and staff touch the bat.
• The school nurse finds out later that day (I assume this finding is accompanied by a large spike in the nurse's blood pressure), and advises the parent to submit the bat for rabies testing.
• The bat tests positive and an investigation is started.
• 107 students and staff are interviewed and all are identified as requiring rabies post-exposure treatment. One student reported that their finger may have been pricked while sticking it in the bat's mouth, which would be a high risk exposure.
• 74 people ended up being treated. There's no word as to why some declined.

This was clearly a completely avoidable situation that resulted in potential widespread exposure to rabies, a large investigation, stress for people and their families, as well as the expense and pain of multiple injections for many individuals - all because one well-meaning but poorly-informed parent brought a dead wild animal to school, and because none of the teachers or staff that witnessed this thought to act.

The school's insurance policy covered the $75 000 in vaccine costs (plus an additional $29 000 for vaccine that was ordered but not used by people who declined vaccination).

• People need to be more informed about diseases such as rabies. This type of information is available on the Worms & Germs Resources page.
• Schools need to develop and enforce policies regarding visitors and pets. Approximately 1/3 of large scale rabies exposures occur in schools.
• Common sense needs to be a little more common.

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Some areas of the world are fortunate enough to be rabies-free. However, there's a closely related virus that is of concern in many of these areas: European bat lyssavirus (EBLV). This virus is present in bats in various countries and can occasionally be transmitted to other animals. A recent report in the journal Emerging Infectious Diseases describes EBLV infection in two cats in France. Both cats died, although the actual cause of death of one of them was uncertain (the animal was also infected with feline immunodeficiency virus (FIV)).

Infection with EBLV in domestic animals is very rare. The risk to dogs and cats is probably very low, but obviously not zero. Avoiding contact with bats is always a good idea. Even in rabies-free areas, measures should be undertaken to keep bats out of houses, and people or animals should never touch sick or injured bats.

The risk to humans from infected domestic animals is unclear. It is thought that dogs and cats pose little risk for further transmission. While susceptible to infection, they are unlikely to transmit EBLV, probably because they produce very low levels of virus. Although there are no clear data about using standard rabies prophylaxis for the prevention of EBLV, it is believed that it would be effective if the virus was transmitted from an infected animal to a person. One cat in this report bit a veterinarian, who received a rabies vaccine booster since he/she had previously been vaccinated against rabies. Fifteen people who were exposed to the second cat underwent the recommended rabies post-exposure series of shots as a precaution.

Even in rabies-free areas, bites from bats or other wild animals should be taken seriously. They should immediately be cleaned thoroughly with lots of soap and water, and medical attention should be sought.

A big problem with EBLV is that it can be very difficult to diagnose. In this Emerging Infectious Disease report, several different tests were used and results were inconsistent.  Multiple tests are probably needed to make a diagnosis. It's possible, therefore, that without this kind of comprehensive testing cases could be missed.

Overall, EBLV is a minor concern for public health, but is yet another reason to just use common sense - avoid contact with bats and treat bite wounds carefully, even in rabies-free areas.

More information about rabies can be found on the Worms & Germs Resources page, and in our rabies archives.

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A recent report in the Journal of the American Veterinary Medical Association by Jesse Blanton and colleagues provided a detailed report of rabies infection in the US in 2007. Here are some of the more interesting points:

• Rabies was diagnosed in 7 258 animals and 1 person. That's a 4.6% increase in animals from 2006, but 2 fewer human cases.
• 93% of cases were wildlife: 37% raccoons, 27% bats, 20% skunks, 7% foxes.
• 0.8% of cases were in cattle and 0.6% were in horses.
• 4% of cases were cats, with the largest numbers of feline cases in Virginia, Florida, Pennsylvania, North Carolina, Maryland, New Jersey, New York, Georgia, Texas and Kansas.  Cat cases peaked in June and July.
• 1.3% of cases were dogs, with the largest number of canine cases in Texas, Georgia and North Dakota. Dog cases did not appear to have a seasonal pattern.
• Small numbers of a variety of other species were diagnosed, including pigs, wolves, opossums, bobcats, coyotes, otters, bears, deer, mongooses (in Puerto Rico), groundhogs and beavers.
• The largest number of rabies cases occurred in Texas (969).
• The infections that occurred were due to several rabies virus variants in circulation in North America, including raccoon rabies virus, skunk rabies virus, arctic fox rabies virus, bat rabies virus and Texas gray fox rabies virus.  In each region of the continent, one or more of these rabies virus variants may be more common.
• No infections with canine rabies virus were identified. Dogs and coyotes were infected by other variants of the rabies virus, but not with the dog variant.  It is believed that dog-to-dog transmission of canine rabies virus no longer occurs in the US.
• The one human rabies case in 2007 occurred in Minnesota, and was probably due to exposure to a rabid bat.

More information on rabies can be found on the  Worms & Germs Resources page, and in the rabies archives.

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A small outbreak of the potentially deadly Hendra virus was identified in a group of horses near Brisbane, Australia. This virus has caused periodic cases of illness and death in horses, and can be transmitted to people working closely with infected horses. In the latest outbreak, 3 horses have died, making this the worst outbreak since 1994 when 14 horses and 2 people died.  Now, a human case has been identified. This person works at a veterinary clinic that treated infected horses. This individual was admitted to hospital overnight but was discharged, so is presumably not very ill.

While Hendra virus (genus Henipavirus) is only found in Australia, it is a good reminder for everyone about the strange nature of some infectious diseases. The natural reservoir of the virus is the fruit bat. It is believed that horses become exposed when infected fruit bats give birth and contaminate horse pastures with uterine fluids. Horses develop respiratory disease ranging from mild to fatal. Human cases have been reported in people working closely with infected horses. A horse trainer and veterinarian's assistant died in the 1994 outbreak. Close contact is required for transmission to people.

Picture: Locations of previous Henipavirus outbreaks (red stars – Hendra virus; blue stars – Nipah virus) and distribution of Henipavirus flying fox reservoirs (red shading – Hendra virus; blue shading – Nipah virus)

It's very difficult to take specific measures to protect horses, people or other animals from sporadic, rare diseases such as Hendravirus infection. However, common sense infection control measures can reduce the risks associated with any animal contact.

• Wash your hands after contact with any animal.
• Avoid contact with sick animals - consider sick animals to be potentially infectious until proven otherwise.
• Remember that  new animal diseases are regularly being identified, and that they might be able to infect people.
• People that work in veterinary clinics must be diligent and use good infection control practices because they are at higher risk of exposure to various diseases.

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