Transmission of Rabies by Bats in South America

By Jonathon Marioneaux

Halloween is still weeks away but it is never too early to get into the spirit of ghosts, goblins, and vampires.

Two common Halloween characters are the vampire and the bat so it is fitting to review vampire bats and their real impact on modern society.  In addition, another favorite of Hollywood is the zombie, depicted as a flesh eating undead corpse infected by a rapidly progressing virus.  The closest virus that causes these symptoms is the rabies virus which makes its host bite other animals in order to spread the virus by contaminated saliva. In my research of these two organisms (vampire bats and rabies), I discovered an interesting mini-literature review published in 2003 on the spread of rabies by vampire bats in South America.

Vampire bats are the principle spreader of rabies in South America. The virus infecting humans and livestock causes millions of dollars’ worth of damage to local economies. These bats are known as haematophagous bats belonging to the order Chiroptera with the most well-known species being the hairy-legged vampire bat (Diphyella ecaudata) and the rarer Desmodus rotundus. These bats feed on animals ranging from snakes to amphibians and cattle to humans and drink between 15 and 25 milliliters of blood per meal.  During their blood meal the bats spread the rabies virus through their saliva resulting in paralytic rabies.  Rabies has an incubation period of 21-150 days and causes muscular tremors, excessive salivation, spasms, and erratic activity.  If left untreated rabies is almost 100% fatal with only three known causes of survival without prophylactic treatment at the time of publication. Rabies can be prevented by the rabies vaccine however it is only given irregularly in South American livestock thus leaving many animals susceptible to paralytic rabies.

In South America, rabies has been blamed for expanding bat populations. Different population control methods have included lethal gas and/or dynamiting bat caves and coumarin paste. These methods led to the death of enormous quantities of bats but only a slight reduction in the numbers of rabies cases.  The rabies virus is spread by saliva and asymptomatic bats do not excrete infectious virions therefore the majority of the bats killed probably did not have rabies.  The spread of rabies in humans is mainly in areas that were previously covered by rain forests that were cleared to make build ranches and urban areas.  The main site of transmission is usually in the toes of individuals living in hazardous housing.

Therefore, urban sprawl and deforestation have led to the spread of rabies from bat populations to humans and livestock.  The current methods of controlling rabies, such as dynamiting caves and gassing known populations, may have the unintended effect of killing beneficial bats such as insectivorous (those that feed on insects) and nectarivorous (those that feed on nectar).  A more effective way of reducing the damage to livestock is more consistent animal vaccination practice which is effectively makes the animals vampire bat repellent.  In addition, educational campaigns should be introduced to reduce the “Dracula” image that many bats have.  It is widely known that bats are beneficial to the ecosystem and must be protected. Indiscriminate killing of bats might make a good Hollywood thriller but it is not good for the environmen

No Rabies Treatment After All: Failure of the Milwaukee Protocol

By Chris Healey

Doctors are abandoning the only treatment for rabies.

The Milwaukee protocol, a procedure reported to prevent death after the onset of rabies symptoms, has been performed over 26 times since its inception in 2004 but has only saved one life. Overwhelming failure has lead health officials to label the protocol a red herring.

Rabies is caused by the rabies virus, an RNA-based virus in the genus Lyssavirus. Transmission typically occurs when virus-laden saliva from a rabid animal enters a wound or mucous membrane. Infection typically occurs from a rabid animal bite. The virus travels along peripheral nerves until it reaches the brain and salivary glands. A characteristic rabies symptom is aversive behavior toward water or water consumption called hydrophobia. Individuals demonstrating hydrophobia will generally avoid water and resist drinking it. Other symptoms include anxiety, nerve pain, itching, impaired sensation of touch, convulsions, paralysis, and coma. Cases among unvaccinated individuals almost always result in death.

The Milwaukee protocol was conceived in 2004 by a team of medical professionals, led by Dr. Rodney Willoughby, after a 15-year-old girl was admitted to a Milwaukee hospital after a rabies diagnosis.

After consulting with researchers at the Centers for Disease Control and Prevention in Atlanta, the team formulated and implemented a novel procedure. The patient was placed in a drug-induced coma and given an antiviral cocktail composed of ketamine, ribavirin, and amantadine. Considering the theory that rabies pathology stems from central nervous system neurotransmitter dysfunction, doctors hypothesized suppressed brain activity would minimize damage while the patient’s immune system developed an adequate response.

The patient was discharged from the hospital 76 days after admission. She demonstrated speech impediment and difficulty walking during a clinic visit 131 days after discharge. It is unclear how long those conditions persisted. In subsequent years, the patient attended college. She remains the only Milwaukee protocol success.

There has been confusion regarding the efficacy of the Milwaukee protocol. A 2009 report published by Dr. Willoughby in the journal Future Virology described the efficacy and promise of the procedure. In that article, Dr. Willoughby cited two new instances of rabies patient survival following Milwaukee protocol implementation. Those two cases brought the total number of rabies patients saved by Milwaukee protocol procedure to three. However, those survivor reports were rebuked by a 2013 article published in the journal Antiviral Research. That article explicitly states Dr. Willoughby’s claims in Future Virology are misleading because the two patients mentioned actually succumbed to rabies.

Overwhelming Milwaukee protocol failure has been attributed to anomaly in the initial patient. For example, she was bitten by a bat, but that bat was not recovered. Without the bat, it is impossible to test the causative rabies agent to rule out a less virulent variant. A mild version could be fought off more easily and could help explain her survival. Additionally, researchers cannot rule out the possibility the patient possessed extraordinary physiology that somehow impaired the rabies progression.

Health officials claim Milwaukee protocol repetition impedes efforts to find new treatments. Instead of exploring new techniques, doctors fall back on the Milwaukee protocol because it was once successful. Crushing failure has prompted the health community to place a taboo on the protocol, encouraging experimentation that may lead to different treatment options.


Image Credit: CDC

The Pandora Report 11.1.13

Highlights include polio in Syria (really not a highlight), bats and SARS (surprise, bats carry everything!), rabies in a French kitten, MERS in Oman, and cholera in Mexico. Happy Friday!

Polio outbreak in Syria threatens whole region, WHO says
For the first time since 1999, a polio outbreak has occurred in Northern Syria. This is not a spontaneous re-emergence of the otherwise eradicated disease. This is the same strain found in the recent Iraqi outbreak, as well as that found in sewage in Egypt, Israel, the West Bank, and Gaza, a strain which originates in Pakistan. Pakistan is one of just three countries globally in which polio remains endemic. Pakistan is also a country in which the Taliban has banned administration of the vaccine, and routinely kills the poor, often women, workers who administer the vaccine anyway. As a result of this tremendous bit of stupidity, polio is re-emerging in Syria, a country in the middle of a civil war, and therefore a ripe breeding ground for the crippling virus’ spread.

Reuters – “‘This virus has come over land which means the virus is not just in that corner of Syria but in a broad area,’ Bruce Aylward, WHO assistant director-general for polio, emergencies and country collaboration, told Reuters in an interview.’We know a polio virus from Pakistan was found in the sewage of Cairo in December. The same virus was found in Israel in April, also in the West Bank and Gaza. It… is putting the whole Middle East at risk quite frankly,’ he said by telephone from Oman.”

Bat virus clues to origins of SARS
Researchers at the Commonwealth Scientific and Industrial Research Organisation have discovered two viruses closely related to SARS in the Chinese horseshoe bats. The viruses both bind to the same receptor in humans as SARS does, the ACE2 receptor, which is primarily expressed in endothelial cells of the kidney and heart. The use of the same receptor in both species suggests that coronaviruses may be able to jump directly from bats to humans without a vector species. Our first thought here is MERS?

BBC – “According to Gary Crameri, virologist at CSIRO and an author on the paper, this research ‘is the key to resolving the continued speculation around bats as the origin of the Sars outbreaks’. This Sars-like coronavirus is around 95% genetically similar to the Sars virus in humans, the research shows. And they say it could be used to develop new vaccines and drugs to combat the pathogen.

WHO: Middle East respiratory syndrome Coronavirus (MERS-CoV) – update

The WHO has confirmed another four cases of the Middle Eastern Respiratory Virus, including the first case in Oman. The three other cases, including one fatality, were all located in Saudi Arabia. While none of the three had recent contact with animals, one of the Saudi cases had been in recent contact with an infected patient. All three however were immunocompromised. The Omani case had no recent contact with animals or travel to Saudi Arabia.

WHO – “The patient in Oman is a 68-year-old man from Al Dahkliya region who became ill on 26 October 2013 and was hospitalized on 28 October 2013…Globally, from September 2012 to date, WHO has been informed of a total of 149 laboratory-confirmed cases of infection with MERS-CoV, including 63 deaths. Based on the current situation and available information, WHO encourages all Member States to continue their surveillance for severe acute respiratory infections (SARI) and to carefully review any unusual patterns.”

France issues rabies warning after kitten’s death
It is no secret that rabies is scary. We’ve all joked at one point or the other about what a zombie apocalypse would look like, which is all fun and games until someone mentions rabies.  While our vaccine is very good, in order for it to be effective, you have to know you’ve caught rabies. The virus itself usually has an incubation period of a few weeks, although cases have occurred in which the virus lay dormant for years.  At that point it’s of course too late. So we definitely understand Paris health authorities preemptively vaccinating five people, setting up a public hotline, and imploring anyone who may have handled or come near the kitten to contact authorities to be vaccinated.

BBC – “France was first declared a rabies-free zone for non-flying terrestrial mammals 12 years ago following the elimination of fox rabies. The 2008 canine rabies outbreak led to that status being suspended for two years. The BBC’s Christian Fraser in Paris said that the urgent appeal seeking anyone who came into contact with the infected animal is likely to be fuelled by fears of a repeat of the 2008 outbreak. The rabies virus is present in the saliva of an infected animal and is usually transmitted to humans by a bite.”

Haitian Cholera in Mexico
The cholera strain introduced to Haiti three years ago has spread to Mexico, which has seen 171 cases of the disease since September 9th of this year. The Haitian epidemic has infected as many as 600,000 people and caused nearly 8,500 deaths in Haiti, before spreading to the Dominican Republic and causing a further 31,000 cases there.

IBT – “Mexico has reported 171 cases of the disease, which has been identified as the same strain that arrived in Haiti, Dominican Republic and Cuba and one that is different from the strain that circulated in Mexico during a 1991-2001 epidemic. The Pan American Health Organization (PAHO) is warning that the illness could spread worldwide. Mexican health authorities reported the 171 cases in Mexico City and in the states of Mexico, Hidalgo, Veracruz and San Luis Potosí between Sept. 9 and Oct. 18. According to the Mexican Ministry of Health, there has been only one fatality, while 39 other cases have required hospitalization. The recent devastation caused by hurricanes Ingrid and Manuel contributed to the spread of the disease, which had not been reported in Mexico since the previous epidemic.”

(image: CDC Global Health/Flickr)