Better Resolution in Microscopy

By Jonathon Marioneaux

For centuries, light microscopes have helped biologists understand the inner workings of the cell by using the unique properties light and how it bends when traversing through different mediums.  The first light microscope led to the discovery of cells and ushered in a new era of biology: microbiology. Since that time, new technological advances have helped push the boundaries of cell anatomy to ever smaller structures and better resolution of those structures.  Several types of microscopes include the scanning electron microscope, transmission electron microscope, florescent microscope, bright field microscope, laser capture micro-dissection microscope, multifocal plane microscope, and x-ray microscope; each one with its unique capabilities.

Traditional optical or light microscopes take advantage of a light source to illuminate a specimen from behind allowing the viewer to see the object. However, the greatest limitation is the resolution of a microscope itself.  The resolution is the ability to differentiate between two objects in a viewing plane and is directly dependent on the wavelength used for viewing.  For example, a light microscope can only view objects to a resolution of 1250 times (theoretical limit 0.250 micrometers) whereas the scanning electron microscope has a limit of 1 nanometer.  As mentioned, this difference is based on the type of wavelength used for viewing, and in the optical microscope this is directly dependent on the type of light used; ultraviolet light achieves a better resolution than infrared.  Another problem with light microscopes is the material must be transparent to the wavelength, the best medium is dependent on the sample, however, oil or water are the most common.

Fei Chen and colleagues have shown that light microscopes can now achieve a higher resolution then previously thought due to a new technique called Expansion Microscopy.  This technique takes advantage of polyelectrolyte gels hydrolyzing in the presence of water homogenized throughout a specimen.  In their work, the researchers showed that a fixed permeabilized brain tissue can be infused with polyelectrolyte gel triggered by an ammonium persulfate accelerator, tetramethylethylenediamine accelerator and digested with tissue-polymer composite protease and can swell 4.5 times without distortion. As the polyelectrolyte gel is mostly water optical microscopes can resolve cellular structures.  The researchers showed that structures such as microtubules, dendrites, and mossy fiber boutons in the dentate were observable in high resolution.

To further increase the resolution of the new technique, the researchers attached fluorescently labeled proteins to the gel matrix and infused the cell before hydrolyzing it.  As the radical hydrolyzing occurred the florescent tags were bound in the matrix and allowed specific regions of the cell to be analyzed in more detail and higher resolution then without the tags.  The tags were created using a specific oligonucleotide sequence on a protein corresponding to an antibody which was then bound to either green florescent protein or yellow florescent protein.  The florescent antibodies also allow for macrostructures to be seen in more refined structural detail then previously possible.

This new technique is still in its infancy and will take advantage of further advancements in both the physical expansion of polyelectrolyte gel and diffraction-limited microscopes.  However, this new technology will allow light microscopes to see smaller cellular structures in finer detail then previously possible in fixed cell microscopy.  Microscope technology continues to advance far beyond the simple refraction lens used to discover the cell.

Image Credit: Erwin94

Chen, F., Tillberg, P., & Boyden, E. (2015). Expansion Microscopy. Science, 347(6221), 543-548.

There is a Pattern Here: The Case to Integrate Environmental Security into Homeland Security Strategy

By Jonathon Marioneaux

Recent reports of extreme weather related events, massive industrial catastrophes with hazardous materials, and critical resource shortages have begun to highlight the need to incorporate climate change as part of the national security strategy and its effects on emergency preparedness.  In their article, Dr. Ramsay and Dr. O’Sullivan argue that changing climate and human influences are becoming more important to homeland security and must be increasingly factored into national and international security assessments. The authors argue that the term ‘Environmental Security’ should be placed among homeland security factors because of its immense reach and potential impact upon the nation and its infrastructure.  However, the role of environmental security is not simply localized to a region or country; the global impact of climate change, resource scarcity, and certain industrial disasters have global impacts that will disproportionately affect less developed nations who are not able to cope as quickly or efficiently.  Finally, these impacts must be incorporated into strategic planning more effectively in order to cope with future global security challenges.

The authors begin by laying out the factors that might impact regional security such as rising sea levels, increased storm intensity, increased droughts and floods, and increased spread of disease and explain why they are a security threat.  For example, the authors state that global sea level rise has increased from 0.02 inches per year from 1950 to 2009, however it has increased 0.08 inches per year along the Atlantic Coast.  This is a security concern as large numbers of people and pieces of critical infrastructure are located in close proximity to coastlines with little to no protection.  To provide further evidence, hurricane Sandy smashed into the Northeast and the above discussed increased sea level helped make it the most expensive natural disaster in modern history. A second example is drought that has plagued the Southeast and Western parts of the nation pushing water resources to record lows.  The result has been increased State and Municipal tensions over increasingly scarce water supplies in regions with rapidly growing populations. The resulting experiences have shown the need to increase local, regional, and federal preparedness to weather related disasters, which will continue to worsen in the future.

The authors also explain why industrial accidents and resource shortages should be factored into the national security equation.  Certain industrial accidents—such as the BP New Horizon spill in the Gulf of Mexico—have the power to influence the economy and, by extension, the physical security of regions or nations by rendering an area inhabitable or economically unsustainable. Increased resource scarcity has already been identified as a factor for political instability and will continue to be so in the future.  The authors referenced food scarcity that triggered some Arab Spring revolutions in certain Middle Eastern countries and pushed existing politicians from power and installed new regimes. Finally, increasing environmental concerns have the potential to lead to increasing levels of regional instability and failed states that will only be exacerbated by continuing climate change.

Some steps are already being taken to address these issues such as the Quadrennial Defense Review and intelligence assessments; however more still needs to be done to fully implement environmental security into the national security apparatus. Recent events have shown that increasing environmental security is imperative to increasing both national and international security because global climate changes are not limited by borders and neither are the outcomes.

Image Credit: Wikimedia Commons

Ramsay, J., & O’Sullivan, T. (2013). There’s a Pattern Here: The Case to Integrate Environmental Security into Homeland Security Strategy. Homeland Security Affairs, 9(6).

Just in Time for Thanksgiving: Fowl Cholera

By Jonathon Marioneaux

Let’s finish the series on birds this week with one of the most ubiquitous diseases that affect our distinguished guests on Thanksgiving: fowl cholera.  First, we will look at what cholera is including a general overview of its structure and transmission.  We will then explore the clinical symptoms and if there are any treatments to protect birds.  We will then conclude with a farewell to our series on turkeys and introduce our next topic: plant diseases.

Pasteurella multocia was first characterized in the 1880’s by Louis Pasture as the causative agent of fowl cholera.  It was soon recognized that P. multocia had three distinct subspecies multocida, spetica, and gallicida with gallicida being the most common.  All birds are susceptible to cholera to varying degrees with waterfowl and turkeys being more susceptible than chickens or other land birds.  P. multocia is a gram negative coccobacillus that stains with Wright stain on its variable carbohydrate surface.  It resists phagocytosis by macrophages and neutrophils with a lipopolysaccraccharide capsule covering a highly hydrated polysaccharides cell wall (Chung et al. 2001). No single virulence toxin has been shown to cause virulence, however several proteins are suspected: capsule endotoxin, outer membrane proteins, iron binding systems, heat shock proteins, neuraminidase, antibody cleaving enzymes, and P. multocida exotoxin (Chung et al. 2001).  The bacterium is highly motile in water and can transfer hosts without direct contact when in close proximity.

The disease is spread primarily by feces or nasal fluids, however it can also be spread by contaminated water, food, bedding, humans (shoes and clothes), and other animals, primarily pigs.  P. multocia causes explosive greenish diarrhea and nasal and oral discharges that can directly infect new hosts (Overview, 2014).  Infected birds can also pass the bacterium by touching feed with open lesions, distended wattles and combs, and contaminated feathers.  Introducing new or wild birds that have not been properly quarantined can introduce the infection to otherwise healthy flocks.  Reservoirs such as pigs and dogs are known to harbor the pathogen as asymptomatic carriers and can spread it to flocks if allowed to mingle with the birds.  Transmission is also a problem with humans when moving between flocks because contaminated feces can stick to boots or other clothing and then be picked up by birds through open cuts or mucus membranes.  Finally, transmission is very common with asymptomatic carriers in large flocks such as factory farms and is less of a problem in free range birds because the bacterium is susceptible to heat and drying out (PM-Onveax,).

Cholera is known for its high morbidity and sudden mortality in large numbers of birds.  Symptoms of infection anorexia, ruffled feathers, oral and nasal discharge, and depression, so careful observation of animals should be carried out routinely.  Other signs might include fibrous contents in distended waddles and excessive red blood cells in livers in post mortem autopsies.  Treatments with penicillin and proactive bacteria can be effective against P. multocia, however caution should be used because antibiotic resistance has been shown to occur rapidly (Fowl cholera, 2014).  A new cholera vaccine is being developed using a highly pathogenic attenuated isolate while an established vaccine uses a mild variant administered under the wing (Hertman et al. 1979).

In conclusion, turkeys are susceptible to bacterial infections primarily by fecal-oral transfer and open lesions.  The most common treatment is oral penicillin or live attenuated vaccination injected under the wing.  With Thanksgiving tomorrow, remember to take extra care of our feathered friends—they can get sick just like us, but with the proper treatment we can take care of them.

This concludes our session on diseases that affect birds; birds are all around us and their diseases deserve to be studied more in-depth because they can teach us a lot about diseases that affect mammals.

Our next series will cover fungal plant diseases in preparation for the winter festivities.


Image Credit: Plainville Farms

Chung, J. (2001, January 1). Role of Capsule in the Pathogenesis of Fowl Cholera Caused by Pasteurella multocida Serogroup A. Retrieved November 22, 2014.

FOWL CHOLERA – Diseases of Poultry. (n.d.). Retrieved November 22, 2014, from

Hertman, I., Markenson, J., Michael, A., & Geier, E. (1979). Attenuated Live Fowl Cholera Vaccine I. Development of Vaccine Strain M3G of Pasteurella multocida. Avian Diseases, 24(4), 863-863. Retrieved November 22, 2014.

PM-ONEVAX-C®. (n.d.). Retrieved November 22, 2014, from

Overview of Fowl Cholera. (n.d.). Retrieved November 22, 2014, from

Turkey Brooder Pneumonia

By Jonathon Marioneaux

This week we continue our series on bird diseases by diving into a fungal bird disease: Aspergillus fumigatus. We will begin by characterizing the physical and genetic qualities of Aspergillus fumigatus and move into a more detailed analysis of how it is spread. Finally we will wrap up by discussing what precautions you can take to keep our favorite holiday bird safe and healthy for the days to come.

Aspergillus fumigatus is a type of fungus that is commonly found in decaying matter and produces spores from the conidiophores during asexual reproduction that are 2-3 microns in size. Its optimal growth range is 37-50 degrees Celsius which is critical for the carbon and nitrogen cycle for breaking down plant and animal matter. It has a filamentous structure under the microscope and its fruiting bodies appear grey during spore release. A study in Nature found 29.4 million base pairs and 5,000 noncoding regions in its genome (Galagan et al., 2010).

A. fumigatus is an opportunistic pathogen that typically attacks immunocompromised individuals, such as those suffering from previous infections, or the very young. The most typical route of infection is pulmonary where the spores germinate in the warm moist areas of the lungs. The fungi evade immune systems attack through macrophages and lactoferrin (iron scavenger molecule) by overwhelming macrophages and lactoferrin production (Ben-Ami et. al., 2005). After successful germination, the fungi penetrate the pulmonary cell walls and in severe cases spread in the blood system for nutrient acquisition. The nutrients include iron, nitrogen, polypeptides, and byproducts, including gliotoxin, that suppress neutrophil activation through superoxide and apoptosis (Ben-Ami et. al., 2005).

In birds, A. fumigatus is spread principally through contaminated feed products or in unsanitary bedding conditions, however, it has been documented that spores can come through improperly cleaned air vents. Air sampling techniques have found seasonal variation among the types of Aspergillus with variations being significantly higher in the winter than the summer (Ben-Ami et. al., 2005). This may be a result of more spore production in drier conditions—there is an inverse relationship between humidity and spore production. Additionally, poults can be exposed to asymptomatic adult carriers and contract it through mechanical interaction. It typically attacks poults 5 days to 8 weeks of age, however, it has been found in birds with underlying genetic or other disease related conditions. Because the fungus mainly attacks the lungs, symptoms can include heavy or rapid breathing and yellow or grey nodular lesions in the respiratory tract, especially lungs and air sacs.

Currently there are no vaccinations or cost effective cure for A. fumigatus infections, therefore once an infection has been identified the bird must be isolated and culled. Vaccine trials have shown no immunity and in some cases a second exposure has proven fatal. The best protection against A. fumigatus infection is delivered through the preparation of clean bedding, food, and air and the prompt culling of infected animals (Ben-Ami et. al., 2005). In addition, increasing the humidity levels and a light spraying of germicide when the poluts are of sufficient size will also keep the risk of contracting the spores lower (Larson et al., 2007).

In summary, there is a lot of work that goes into creating healthy turkeys but with some simple steps and proactive work flocks will not be overrun by pathogenic A. fumigatus. The fungus is very necessary in the carbon and nitrogen cycle and only causes opportunistic disease in immunocompromised birds. So, enjoy your holiday turkey and next week we will continue our series and investigate more illnesses that plague our avian friends.


Image Credit: Champoeg Farm

Ben-Ami, R., Lewis, R. E. and Kontoyiannis, D. P. (2010), Enemy of the (immunosuppressed) state: an update on the pathogenesis of Aspergillus fumigatus infection. British Journal of Haematology, 150: 406–417. doi: 10.1111/j.1365-2141.2010.08283.x

Galagan, J. (2005, October 5). Sequencing of Aspergillus nidulans and comparative analysis with A. fumigatus and A. oryzae. Retrieved November 16, 2014, from

Larson, C., Beranger, J., Bender, M., & Schrider, D. (2007). Common Diseases and Ailments of Turkeys and Their Management. In How to Raise Heritage Turkeys on Pasture (pp. 35-52). American Livestock Breeds Conservancy.

Characterization of Turkey Pox

By Jonathon Marioneaux

This week we start a new series of articles about the diseases of birds. We will start with viruses and then progress to bacterial and fungal later in the month.   In celebration of the next major holiday, we will cover turkeys and the threats to both our feathered friends and to their handlers.  To begin our series will look at fowl pox, more specifically turkey pox.  We begin with a short characterization of the virus, how it works in hosts, and the general routes of transmission.  Then we progress to a short case study of turkey pox in Europe where it is becoming an endemic problem among breeders.  Finally, we wrap up with a discussion of how our feathered friends help us in the wild (and on the plate.)

Pox viruses belong to two major families—Chordopoxvirinae, which infects vertebrates including mammals and birds, and Entomopoxvirinae, which infects invertebrates including beetles, butterflies, and flies.   Both of these families share similar characteristics including large genomes, early RNA’s made in the virion core, and an internal envelope formed de novo, not during budding.  Mature particles of Chordopoxvirinae attach to the target cell membrane glycosaminoglycans during the first uncoating stage and release enzymes ready to begin DNA replication (Acheson, 2011).

Pox viruses are unlike many other viruses because they replicate solely in the cytoplasm and therefore they must carry all of the genes coding for DNA replication proteins with them.  These early genes code for proteins that break down the viral core and expose intermediate genes that code for DNA replication.  As theses intermediate genes are activated by compound promoters they produce intermediate mRNA which code for intermediate proteins.  These intermediate RNA’s are unique because they have 5’ terminal poly(A)heads added, facilitated by a TAAA sequence, which allows for a slippage mechanism adding the AAA head (Acheson, 2011).  These proteins are created in viral factories and set the stage for late gene activation.  The late genes code for structural proteins used in the encapsulation process.  The process includes the packaging of completed DNA (incomplete viruses) and enzymes (mature viruses); the final step is dependent on the infection route of the virus.

If the host cell ruptures before the virus escapes then it is left with an extra protein layer and is called an extracellular virus, which can infect cells easier.  If the virus is able to escape the cell then it sheds its protein shell during the budding process and is left with only its envelope. One difference between these viruses is their stability in the external host environment.  These enveloped viruses are extremely stable in the environment and are found in the scabs and mucus of infected individuals (Acheson, 2011).  Poxviruses have several means to evade host immune systems including TNF-binding proteins and soluble IFN-γ proteins which diminish inflammatory cytokine activity.  Finally, the general routes of transmission include contact with abraded epithelium of mucosal membranes or skin and physical inoculation of epithelial tissues either by pecking or blood feeding arthropods (Kindt et al, 2007).

In 2010 a turkey farm in Austria experienced an outbreak of fowl pox in the cutaneous form (Hess et al, 2011).  The farm had 11,680 birds spread over six flocks in stages ranging from polts to mature birds.  The effect on the birds included “nodular red-brown wart-like growth” and encrusted lesions on the head and neck region.  Samples were taken a plated on Columbia agar, McConkey agar, Schaedler agar, and Sabouraud-gentamicinchloramphenicol agar and included at 37 ͦC in aerobic conditions. Other tissue samples were used to isolate the virus using pathogen-free-Gallus gallus domesticus embryos.  PCR DNA replication was performed by using tissue samples and fowl pox base pairs were isolated by gel electrophoresis.  These isolates were reconstituted and sequenced with the original fragments and compared to the GenBank database using BlastN algorithm.

The results included antibiotic Staphylococcus aureus which is common on most skin surfaces but can become problematic when entered into the blood stream.  The tissue isolates showed hyperplasia and hypertrophy as well as distended eosinophilic inclusion suggestive of excessive dissolved lipids.  The GenBank search yielded 100% matches to avipox-AY530304 and turkeypox-DQ873808.  Interestingly no lesions were reported on internal organs, however, no septicemia test was done so a blood infection could not be excluded.

In contrast to other outbreaks the morbidity rate was very low due to a lack of perceived aggressiveness among the birds.  It was noted that a large number of flies were observed in heavy litter suggesting an initial route of exposure and a persistent route of infection to other individuals (Hess et al, 2011.)  Both flies and mosquitoes are known transmitters of fowlpox (Larson et al, 2007).

In conclusion, there are many types of fowl pox ranging from pigeons and turkeys to ducks and chickens however it is generally assumed that the pox viruses that effect each are unique to that species.  These pox viruses have commonalities among birds and generally affect the non-feathered regions of the neck, feet, and head.   In many cases the disease is spread by pecking/scratching or by blood feeding arthropods and covers most of the southeastern part of the USA. In general, wild turkeys are less affected by the virus than domesticated turkeys, however that could be in part due to a lack of recorded data and the predation of sick individuals (Davidson and Doster).

No need to worry, though, as all farm raised stocks are vetted by the USDA and are disease free so the risk of contracting fowl pox by eating a farm raised turkey is very slim. So this Thanksgiving eat lots of turkey and remember the complex interactions that happened to get it to your plate.


Image Credit


Acheson, N. (2011). Poxviruses. In Fundamentals of Molecular Virology (2nd ed., pp. 312-323). Hoboken: John Wiley & Sons.

Davidson, W., & Doster, G. (n.d.). Avian Pox – A disease that can affect any bird. NWTF Wildlife Bulletin, 24:1-24:4.

Hess, C., Maegdefrau-Pollan, B., Bilic, I., Liebhart, D., Richter, S., Mitsch, P., & Hess, M. (2011). Outbreak of Cutaneous Form of Poxvirus on a Commercial Turkey Farm Caused by the Species Fowlpox. Avian Diseases, 714-718.

Kindt, T., Goldsby, R., & Osborne, B. (2007). Immune Effector Mechanisms. In Kuby Immunology (6th ed., p. 314). New York: W. H. Freeman and Company.

Larson, C., Beranger, J., Bender, M., & Schrider, D. (2007). Common Diseases and Ailments of Turkeys and Their Management. In How to Riase Hertigae Turkeys on Pasture (pp. 35-52). American Livestoock Breeds Conservancy.


Aerosolized Fungal Infection from Bats

By Jonathon Marioneaux

As promised, we will be continue our coverage of bats and their diseases this week.  Over the last several postings we have covered different diseases bats can carry and their place in folklore.  In many horror stories and movies the main antagonist resides in a cave which makes you wonder, what else is in that cave? One of the main diseases that can be contracted in caves is histoplasmosis, which as it turns out is a relatively common disease.  Researchers from Heliopolis Hospital in Brazil documented a case of oral manifestation in a patient in 2013 that provided clinical details to the history and progression of the disease.

Histoplasmosis is a fungal infection caused by Histoplasma capsulatum and has two variants—capsulatum and duboisii. The fungus is found in caves worldwide, however most clinical cases occur on the American continent.  H. capsulatum requires moderate temperatures and constant humidity to grow and does best in bird or bat guano.  The fungus is found in its hyphae form primarily in caves and reverts to its yeast form in human lungs due to the higher temperature.  The fungus is primarily transferred to humans in its aerosolized form during cave diving, giving it the nickname “Caver’s disease” and “Spelunker’s disease.” However, it can also be transferred any time soil aerosolizes, for example, during digging.

The disease has a relatively low mortality rate in immunocompetent people and may go undetected as mild flu symptoms. Yet in people with compromised immune systems, such as AIDS patients, it can reach mortality rates as high as 80% and can be a tool for AIDS diagnosis.  In some cases the disease can become chronic in the presence of underlying disease and become severe to life threatening.  Diagnosis of H. capsulatum can be difficult due to its mimicking of other diseases, such as tuberculosis, and limitations of diagnostic exams.  The gold standard for diagnosis is culturing of the fungi on dextrose slats which will show white or brown filamentous colonies.

The Brazil patient was initially admitted on complaints of oral lesions and shortness of breath to the Heliopolis hospital.  The initial diagnosis was tuberculosis, however radiography diffuse infiltrate of both lungs and negative acid-fast staining discounted this.  Subsequent tests showed CD4/CD8 lymphocyte count was normal, discounting HIV, and culture tests indicated fungi presence.  A biopsy of lung tissue showed Langhas-type multinucleated giant cells with variable amounts of lymphocytes consistent with histoplasmosis. The patient was treated with Itraconazol for six months and showed marked improvement.

The above example explains why the conversation between patient-doctor and doctor-doctor is very important.  Without knowledge of the patient’s history and the referral by the dentist it is possible that a positive diagnosis could never have been made. This is especially true with organisms which are hard to grow or mimic symptoms of other disease.  In addition, knowing the immunocompetent state of a patient can give clues to what type of pathogen might be present.

So, when going spelunking or anywhere near animal feces wear a mask or other protective covering to prevent infection from various diseases including H. cacsulatum. Bats are our friends and serve a much needed role in pollenating plants and keeping insects under control during the warm parts of the year.  Let’s not forget their contributions when discussing their role in disease transmission and the Hollywood spin put on them for Halloween. It is always advisable to take caution when handling bats of any species or geographic location to prevent the spread of numerous viral, bacterial, and fungal agents that they carry.

With Halloween upon us, this concludes our series on bats and their diseases. Next week, we will pick up coverage of birds (if you have a specific bird you would like me to cover send me an email) to get into the Thanksgiving spirit.

As always remember to wave at the next bat and thank them for their invaluable service to our ecosystem!

New Bat Flu Found

By Jonathon Marioneaux

Halloween is right around the corner, so we continue our coverage of one of the most notable creatures of the season: bats. Previously we covered vampire bats and their role in spreading rabies to humans and livestock in South America.  Considering how bats appear to be vectors for both Ebola and rabies this made left me wondering what other viruses bats carry.

Many animals carry some sort of virus that belong to the Orthomyxoviridae family which is broken into three classes A, B, and C.  Classes B and C primarily infect humans while class A infects a range of hosts including birds, mammals, and reptiles. However, no Orthomyxoviridae virus has been found in bats, or so we thought.  In October researchers from Maryland and Kanas discovered a new flu virus that can be transmitted between bats and in doing so discovered a new lineage of the Orthomyxoviridae family and a potential new pandemic flu.

Influenza is a negative sense RNA virus consisting of 7-8 segments allowing it to recombine during infection and create new combinations of RNA segments.  Multiple types of influenza can infect a host cell simultaneously allowing strains of flu from different hosts to recombine in novel ways.  This ability to be infected with different types of influenza viruses is why there are new outbreaks of the flu every year and why the virus has the potential to become a global pandemic if the correct reassortment happens.

Bats carry many diseases such as Coronaviruses, Filoviruses, and Henipaviruses, but as stated earlier, no Orthomyxoviridae have been previously found.  While trying to sequence genomes the researchers found influenza-like RNA sequences in tissue cultures.  However, when these sequences were introduced into cell cultures they did not replicate efficiently.  The researchers then synthetically altered the surface protein structure and re-infected cell and animal models.  The virus reproduced efficiently in the cell and mice models with high mortality among the mice; thus showing that the virus can reproduce in traditional flu hosts. The researchers indicated that the bat virus does not have the same surface proteins that influenza A and B contain.  This lack of ability to infect the same cells shows high cell specificity that results in a limitation of the cell types that influenza A and bat influenza can infect.  Finally, the genetic differences that are seen in the bat influenza virus indicate that they are a distant relative of the current influenza types, thus potentially making them a new branch of the Orthomyxoviridae family tree.

The difficulty in growing the bat viruses in traditional cells without modification indicates that the virus does not have the necessary surface proteins to enter cells.  However, after synthetic modification the bat virus was very lethal in host cells and animal models.  This indicates that the bat virus is only distantly related to the influenza A and B types that circulate currently.  Therefore, the risk of reassortment between flu viruses is small and there is a smaller risk of a global pandemic.

In conclusion,  bats harbor many viruses and make great Halloween decorations but they pose little risk for a global pandemic of zombie apocalyptic proportions and are great for the environment.  So, make sure you thank the next bat that you see and we will continue our coverage of our winged friends next week.

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