Posts tagged rabies

New World (right) and Old World Vultures (left)

The New World and Old World vultures are a prime example of convergent evolution - despite being only distantly related, they ended up with many of the same traits, behaviors, and appearances, and occupy largely the same niches in their ecosystems.

These large birds all subsist largely on carrion (dead things) or carrion products (bones), soar long distances to locate food, flock when resting [Egyptian vulture aside], and have unfeathered or sparsely feathered heads and necks.  They all provide critical “cleaning crew" and disease-reducing services in relation to humanity and other animals.

And all vultures, despite their ability to consume rabies and anthrax-ridden corpses without harm, are vulnerable to human destruction - even inadvertently.

With that out of the way, there are some fascinating differences between the two vulture orders!

Old World Vultures:

  • Locate food by sight or hearing other scavengers locate a kill
  • Excellent eyesight
  • Build stick nests for eggs
  • Frequently vocalize (and have a syrinx)
  • Poor sense of smell
  • Located in Europe, Africa, and Asia

New World Vultures

  • Locate food by smell
  • Will soar in circles above fresh kills or near-dead animals (who often give off a distinct scent) until other predators and scavengers leave
  • Lay eggs directly on rocky outcroppings or in crooks of trees - no nests
  • Practice urohidrosis to keep cool - they urinate onto their bare legs for the evaporative cooling it provides - very uncommon in birds
  • No syrinx, only vocalizations are hisses and clicks
  • Located in North and South America

Note that there are no vultures or condors in Australia or Oceania - the scavenger niche in those regions is filled by other birds, reptiles, and mammals.

Images:
Louis Agassiz Fuertes’ Album of Abyssinian Birds and Mammals. Field Museum of Chicago, 1930.

The Birds of America. John James Audubon, 1840.

How Vultures Save People

zosci:

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photo credit

Many people only see turkey vultures as nasty pests; lowly, ugly scavengers undeserving of our respect. But these bald-headed badasses may have saved thousands of people over the years because of their amazing guts.

Turkey vultures have such strong stomach acid that they can digest bacteria and viruses that would kill other animals, such as E. Coli, anthrax, and botulism. You may have heard me spout this fact before, but I want to further express how critical this ability is. A single crystal the size of a grain of sand of the botulism toxin, for instance, is potent enough to kill 9,600 people. When vultures consume carcasses with this toxin in it, they are not only immune to its effects but they remove it from the ecosystem. This means that when that turkey vulture dies and another scavenger eats it, the scavenger will not be subject to the toxin and will therefore not die!

Abilities like this put vultures in an undeniably important position when it comes to maintaining the health of an ecosystem (and of people!). If you still do not believe we need vultures, look to India as an example. The Indian and Indian white-rumped vulture populations have declines by 97% in the last decade because of a poisonous anti-inflammatory drug used on Indian cattle.

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photo credit

Without these vultures to consume the carcasses of dead animals, the population of stray dogs has skyrocketed. More stray dogs means more rabies, and therefore more rabies victims. Because of the decline of Indian vultures, which rabies has no effect on, India has become the number one country for rabies related deaths. 20,000 people per year die from rabies in India- that is more than 1/3 of the worldwide death toll!

If the connotation associated with turkey vultures does not change soon, and if use of lead shot is not banned (lead poisoning in the number one cause of turkey vulture deaths), a similar process may occur with something like botulism here in America.

yes, a thousand times yes.

not historical, but so important. do not discard vultures. they are critical to our environment. our vaccination rates are nowhere near high enough to consider us to have “herd immunity” to rabies anywhere in the United States and most of north america, especially where coyotes or feral dogs and raccoons intermingle.

killing off coyotes has proven to lead to huge surges in CWD and other deer and elk diseases, some transmissible the cows and horses that share their ranges. total culls of racoons are almost impossible, and inadvisable (thanks to their passive control of norway rats and their parasites in metro areas, and their ability to easily take over woodland areas, respectively). 

again: vultures cannot carry anthrax or hog cholera, despite rumors and urban legend. in fact, they are immune to both diseases.

turkey vultures may be ugly, and they may be considered “pests”, but they clean up our roadways far more efficiently than crows, and do not pose any threat to our livestock.

compoundfractur:

"Rabies in a Human Patient"

"Mad dog"
This 1826 cartoon depicts a “mad dog” in the London streets, attacking people. You can note the “Hydrophobia!” warning posted in the upper left-hand side of the caricature.
Rabies was definitely a thing people wanted to avoid, and was especially terrifying because they didn’t understand anything useful about the virus. All they knew was if you got bit by a mad dog, you had less than a year before you went dumb or manic and then ended up dead, yourself…at least if your bite wound didn’t get infected and kill you before then!

"Mad dog"

This 1826 cartoon depicts a “mad dog” in the London streets, attacking people. You can note the “Hydrophobia!” warning posted in the upper left-hand side of the caricature.

Rabies was definitely a thing people wanted to avoid, and was especially terrifying because they didn’t understand anything useful about the virus. All they knew was if you got bit by a mad dog, you had less than a year before you went dumb or manic and then ended up dead, yourself…at least if your bite wound didn’t get infected and kill you before then!

Tongue and larynx of rabid dog
People once thought that rabies was caused by a worm in the sublingual salivary glands, because of how tight and swollen they become when rabies is infecting the system. We know now that that’s not true. Rabies is caused by a virus that infects the nervous system. Once it enters the body, it seeks out the peripheral nervous system, and moves along peripheral nerve cells until it reaches the CNS. The virus continues up the central nervous system until it reaches the brain, where it multiplies, causes the extreme symptoms, and kills the victim.
Up at the top of this illustration, you can see the inflamed section of the upper throat. This goes along with the involuntary throat spasms that rabies entails, which prevent the ingestion of any liquids. The spasms are often incredibly painful, and the avoidance of liquids (though not a true fear of them) is why rabies used to be called hydrophobia.
Rabies and Hydrophobia: Their History, Nature, Causes, Symptoms, and Prevention. George Fleming, 1872.

Tongue and larynx of rabid dog

People once thought that rabies was caused by a worm in the sublingual salivary glands, because of how tight and swollen they become when rabies is infecting the system. We know now that that’s not true. Rabies is caused by a virus that infects the nervous system. Once it enters the body, it seeks out the peripheral nervous system, and moves along peripheral nerve cells until it reaches the CNS. The virus continues up the central nervous system until it reaches the brain, where it multiplies, causes the extreme symptoms, and kills the victim.

Up at the top of this illustration, you can see the inflamed section of the upper throat. This goes along with the involuntary throat spasms that rabies entails, which prevent the ingestion of any liquids. The spasms are often incredibly painful, and the avoidance of liquids (though not a true fear of them) is why rabies used to be called hydrophobia.

Rabies and Hydrophobia: Their History, Nature, Causes, Symptoms, and Prevention. George Fleming, 1872.

"Mad dog in a coffee-house"
Late 18th century illustration by Thomas Rowlandson (1756-1827)

"Mad dog in a coffee-house"

Late 18th century illustration by Thomas Rowlandson (1756-1827)

The girl who survived rabies

Well I found that much faster than I thought I would. Here ya go: http://youtu.be/gWiYyYwZy_w

They have found a way to “cure” rabies by putting a person in a coma so deep they are on the brink of death.

Ah, yes, Jeanna Giese and the Milwaukee Protocol. The church parking lot where she got bitten by the bat is actually down the street from where my cousin lives, and they went to the same school for a couple of years, though they never knew each other.

The Milwaukee Protocol has a LOT to do with the strength of the patient’s immune system, and the strength of the strain of rabies that they were infected with. If the patient has a weak immune system or are infected with the stronger of the rabies strains, it does not appear to have the same benefits.

ShortFormBlog: Girl beats the odds, becomes a rare rabies survivor

More historical rabies coming soon (along with parotid tumors and other ear afflictions).

Once known as hydrophobia due to the characteristic “fear” (really just reflexive gagging caused by the virus) of water, rabies always has been deadly once symptoms appear. It looks like it still will be for a good while longer, given that our current protocol (vaccinate animals, give vaccine to those who work with rabid animals and those exposed by injury, give immune globulin to those actively exposed to virus) results in only 3-4 human deaths per decade on average, and all of them appear to be from unnoticed bat bites from a rare genus of bat (rabies is rare in bats in the US, and it’s even rarer that bats bite people in the US). 

More recent history: 

Jeanna Giese of Milwaukee, WI, contracted rabies from a bat she caught in her church to put back outside, in 2004. Thinking it was only a tiny scratch, probably from the feet, she did nothing but put a small bandaid over the wound. Three weeks later, she began feeling tired, vomiting, and her left arm - where the bat had bitten - began tingling. The last symptom was a result of the rabies virus moving through the neurons - and only the neurons - to her Central Nervous System, and eventually to her brain. 

Where almost all patients at this point will die within a week (as the antivirus vaccine will only speed up death), Jeanna Giesse was admitted to Children’s Hospital in Milwaukee, WI, and Dr. Rodney Willoughby decided to put her into a medically induced coma in order to “shut down the brain and wait for the cavalry to come”. He was banking on the fact that her body would eventually build up enough antibodies to fight off the virus itself when the virus was both unable to advance through her CNS to propagate, and had antivirals preventing any advance it may make on its own (without brain stimulation to allow it to jump between neurons). It was a treatment never tried before, but it worked - Jeanna survived and just graduated from college this last May.

This became known as the Milwaukee protocol, and has since had one of the two antiviral medications (ribavarin) removed from the regimen, as it was believed to have actually hindered the cellular processes of some aspects of the immune system. Combined with the fact that the bite was on her hand (very far away from her brain, given that rabies has to travel only through the neurons) so that her body had already built up a lot of antibodies, keeping her artificially alive while the body produced the remainder it needed to fight off the disease was actually feasable.

Though rabies causes encephalitis (swelling of the brain), it doesn’t actually damage the brain structures per se…death comes from inability to control muscles, so that the patient chokes on their saliva, can’t breathe, or has a fatal heart arrhythmia. When these factors are able to be controlled for - and it’s much harder than it seems - and the patient is not comatose for an excessively long period, survival can occur, thanks to the body’s amazing ability to kill off invaders even when incapacitated. Of the original Milwaukee protocol, 3/25 patients survived, and of the modified one (without the ribavarin), 3/11 have now survived. The debate whether the protocol is the determining factor in survival, instead of the fact that the rabies strains in survivors have been noted to be weak ones, continues.