Rabies: The Killer Virus Ask students to make inferences about these pictures. Copyright 2010. PEER.tamu.edu

Rabies is caused by a virus. What is Rabies? Rabies is caused by a virus. Rabies is an RNA Virus. It has RNA as its genetic material … no DNA How can it multiply? … use their own enzymes to duplicate their RNA Other RNA viruses: SARS Influenza Hepatitis C A virus cannot reproduce on its own. It “high jacks” a cell of a host and makes that cell produce more viruses!

Shaped somewhat like a bullet. The Rabies Virus Shaped somewhat like a bullet.

Rabies Rabies is a special virus because it is lethal to pets and people. All states require pets to be vaccinated for rabies. Pictures from: http://thedogshamanblog.wordpress.com/category/dog-shaman/traveling-with-your-dog/

Who gets Rabies? All mammals are susceptible to rabies. This not only includes dogs and cats but livestock and humans as well. Rabies is know as a zoonotic disease since it can be transmitted from animals to humans and from humans to animals. In U.S. 93% of all rabies occurs in wild animals Source of recent information:Rabies surveillance in the United States during 2007. JAVMA 233: 884-887 Ask students to make inferences from this chart of reported cases.

Review 1 Why is rabies a significant concern? What is a zoonotic disease? What kinds of animals get rabies? How does the rabies virus reproduce? It is 100% fatal. An animal disease that can be spread to humans. All mammals, including humans By “hijacking” another cell and getting it to reproduce for it. If your students have studied RNA, they can be told that they reproduce by RNA, either their own or that of the host cells, depending on the sub-type of RNA virus it is.

How is Rabies spread? Rabies is transmitted through the saliva of an infected animal. This usually occurs by a bite wound. The virus then travels up the nerves toward the brain and spinal cord. It even leaves one nerve cell and moves to the next. How do you suppose it does that? 1. Do your students know about “exocytosis?” Actually, we don’t know exactly how rabies moves, but most likely it migrates to the membrane, is “spit out” exocytosis style, and then attaches to the membrane of the next neuron and moves into it. A big question: how does the virus “know” which direction to move in? … that is up the axon, into the cell body, go to the surface, get expelled, and then attach to the next neuron?

Do I look like I have rabies? Symptoms of Rabies In early stages rabies is very difficult to detect. After an animal is bitten it usually takes two to twelve weeks before it shows any symptoms, however it may take as long as two years. This period of time is known as the incubation period. This dog is a Chinese Crested Dog. Although it does have unusual looks, it does not have rabies. This is how this breed “normally” looks. Do I look like I have rabies?

Initial Symptoms of Rabies The first symptoms are flu-like in humans. Human patients complain of feeling tired with pain and stiffness. Dogs may chew at the bite site, have fever, show a loss of appetite, or show subtle changes in behavior. The tone of their bark might change. Dog information from:http://www.animalhealthchannel.com/rabies/symptoms.shtml

Neurological Symptoms Soon afterwards, symptoms begin to include neurological dysfunction. This may include slight paralysis, anxiety, sleeplessness, paranoia, and delirium.

Advanced Symptoms in Dogs Craving to eat anything, including inedible objects Constant growling and barking Dilated pupils Disorientation Erratic behavior Episodes of aggression Facial expression showing anxiety and hyperalertness Irritability No fear of natural enemies (e.g., wild animals may not be afraid of people) Restlessness Roaming Seizures Trembling and muscle incoordination Image from: http://www.south-norfolk.gov.uk/environment/698.asp

Advanced Symptoms The patient will begin to produce large quantities of saliva and tears. The ability to swallow and bark are also lost because of paralysis of the jaw, throat, and chewing muscles.. It is because of these characteristic symptoms that animals often “foam at the mouth.”

Symptoms Because patients are unable to swallow water they exhibit hydrophobia or fear of water. This is seen in approximately 50-80% of patients.

Symptoms The virus spreads from the brain to the salivary glands where viral particles are able to be shed in the saliva, thus allowing the animal to spread the virus to others. Picture from: http://www.northcentralanimalhospital.com/site/view/183737_RabiesInfo.pml

Aggression Rabid animals may also exhibit aggressive behavior. This makes them more likely to bite other animals allowing infection to spread. Wild animals with rabies may lose their fear of humans and be active during the day and in the open when they are usually not.

Symptoms Once the onset of symptoms has begun the animal usually dies within ten days. Rabies is almost always fatal. There are only six reported cases in all of human history of humans surviving rabies after the onset of symptoms*. *Reference: Centers for Disease Control and Prevention http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5350a1.htm *See reference on slide notes

Review 2 What is happening during the incubation period of rabies? Summarize the symptoms of rabies. Why do bites spread rabies? The virus is migrating up neurons to infect enough neurons to cause symptoms. It begins like flu. Then causes all sorts of behavioral changes, ranging from aggression to depression.. Virus migrates to salivary glands and gets spread with the saliva.

Prevention Despite the fact that rabies is nearly always fatal once an animal is infected, it can be easily prevented. Vaccination is the most effective and commonly utilized method of prevention. Vaccinations are commonly given to pets and livestock. This method of prevention has greatly reduced the incidence of disease in many countries.

Human Prevention The first human was successfully vaccinated for rabies in 1885 after being bitten by a rabid dog. While human vaccination has been available for many years, vaccination is normally only given to people who are exposed to a rabid animal or those who are at an increased risk of being exposed, such as veterinarians and animal care workers. If a human gets exposed in a way where the disease can spread rapidly, as with a splash of blood or saliva into the eyes or nose, a passive injection of antibodies is usually recommended, followed by vaccination with an active vaccine.

Public Health Rabies is found in nearly all nations. Nations highlighted in red were at a high risk for rabies. The majority (99%) of rabies in humans is seen in Asia and Africa. The United States is in yellow, for low risk. However, the United States is very close to countries with high risks like Mexico and countries in South America. Is the United States at high risk for Rabies?

Rabies was such a big problem in France in the 1800s that it caused Pasteur to make a vaccine for rabies one of his highest priorities. Pasteur biographies

Rabies in The U.S. The majority of rabies cases in the U.S. are caused by bats. Skunks and raccoons are also a major reservoir for the disease. Bat bites cause the largest number fatalities since the bites are often small and people may not even realize that they have been bitten.

Rabies In Wild Animals Different colors for the same wild animal reservoir indicate a different variant of the rabies virus. Every year, the vast majority of rabies cases are in wild animals. Vaccination of pets must be working to keep their infection low even at a time when cases in wild animals increase. Source: JAVMA. 2008. 233: 884-897 How do you interpret the graph?

States with the Most Cases Wild Animal Sources Raccoons Bats Skunks Foxes Texas 17 482 362 32 Virginia 359 30 185 90 New York 279 104 75 25 North Carolina 245 34 98 58 Source: JAVMA. 2008. 233: 884-897

We’re cute, but we could be dangerous! Staying Safe We’re cute, but we could be dangerous! Never handle wild animals, especially skunks, raccoons and bats. Never try to nurse sick animals back to health, call your local wildlife rescue service instead. Make sure wild animals can’t get into your garbage cans. Never purposely feed wild animals. Never handle wild animals that are acting unafraid of humans. Never handle wild animals that approach you.

Testing for Rabies Because rabies is such a deadly disease, testing is very important. If a wild animal bites a person, the person should immediately go to a physician the animal should usually be tested immediately by a veterinarian. If an person is bitten by a pet, the pet is put in quarantine for a period of ten days to see if it develops symptoms. If an animal is shedding the virus in its saliva it will almost always start showing symptoms within ten days.

Pets are kept away from all human contact during this time, and watched carefully by a veterinarian.

Testing for Rabies Since rabies affects the brain the best way to test for it is by examining brain tissue. This is done with a method call direct fluorescent antibody testing. This test can only be done post mortem (after the animal is dead.) Fluorescent antibodies have been tagged with a chemical compound that fluoresces under certain wavelengths of light. Special microscopes have the ability to deliver the appropriate wavelength of light to cause fluorescence. Sections of the brain are submitted for a direct fluorescent antibody test, which illuminates the parts of the brain that are infected.

Vaccinate us so we will be SAFE! Staying Safe Always vaccinate pets for rabies! Puppies and kittens should be vaccinated at sixteen weeks of age and then at one year of age. Every animal should get a vaccine every three years for the rest of their life. In Texas, pet rabies vaccination is required by state law! Vaccinate us so we will be SAFE! Pets can get bitten by rabid dogs, skunks, squirrels, bats, and other animals that are carrying the disease. For more information on Rabies Quarantine and Testing See: http://info.sos.state.tx.us/pls/pub/readtac$ext.TacPage?sl=R&app=9&p_dir=&p_rloc=&p_tloc=&p_ploc=&pg=1&p_tac=&ti=25&pt=1&ch=169&rl=27

Review 3 What are some ways to prevent the spread of rabies? Vaccinate pets. Avoid wild animals that are acting strange or unafraid of people. Don’t keep wild animal pets. Don’t feed wild animals. Consult your physician immediately if you get bitten by an animal.

Rabies Research Most research is focused on public health (vaccines in food for wild animals, better vaccines, vaccination programs for pets, etc.) We Need: More fundamental research on how a virus is able to multiply. Research on stopping the migration of rabies throughout the nervous system. If we knew how to stop viruses from multiplying, we would have a cure for all viral diseases (including the common cold!). Chicken pox is an interesting model. If you get chicken pox as a child, the immune system forces it into “hiding.” The virus is tapped for decades, but in some people, it breaks out again in old age in the form of shingles. Nobody knows how the immune system traps viruses for decades, but if we did, it might lead to useful therapies that could apply to all viruses.

World Rabies Day is a worldwide campaign against rabies World Rabies Day is a worldwide campaign against rabies. One person in the world dies from rabies every 10 MINUTES, equaling 55,000 each year! The disease is 100% fatal, but 100% preventable. Human deaths are happening most frequently in underprivileged countries, but the presence of rabies and it's risks are still remarkably high even in the U.S. For more information go to: http://www.worldrabiesday.org/