Second Annual Great Plains Emerging Infectious Diseases Conference

For those of you in the general vicinity, the University of Iowa Department of Epidemiology will be once again sponsoring the Great Plains Emerging Infectious Diseases Conference on April 19-20 in Iowa City. This year’s keynote speaker will be Dr. Peter Daszak, President of the EcoHealth Alliance:

Dr. Peter Daszak, president of EcoHealth Alliance, is a leader in the field of conservation medicine and a respected disease ecologist. EcoHealth Alliance is a global organization dedicated to innovative conservation science linking ecology and the health of humans and wildlife. EcoHealth Alliance’s mission is to provide scientists and educators with support for grassroots conservation efforts in 20 high-biodiversity countries in North America, Asia, Africa, and Latin America.

As Executive Vice President of Health at EcoHealth Alliance, Dr. Daszak directed a program of collaborative research, education, and conservation policy. The program examined the role of wildlife trade in disease introduction; the emergence of novel zoonotic viruses lethal to humans such as Nipah, Hendra, SARS, and Avian Influenza; the role of diseases in the global decline of amphibian populations; and the ecology and impact of West Nile virus in the U.S. Dr. Daszak holds adjunct positions at three U.S. and two U.K. universities and serves on the National Research Council’s committee on the future of veterinary research in the U.S.

Like last year, we will also be having breakout sessions in an “unconference” format–loosely moderated by discussion leaders. If you’re thinking of attending the conference and would like to suggest or lead a session, please leave a comment or drop me a line (tara dash smith at uiowa dot edu). Looking forward to seeing some readers here in April!

Coexisting with Coyotes

This is the twelfth of 16 student posts, guest-authored by Stanley Corbin.

Disease in wildlife is an important concern to the health and safety of humans and domestic animals. The expanding growth of our nation and resultant land use changes with urbanization has resulted in a shrinking habitat and fragmentation for all animals, including humans. The effects of ecological disruption are universally recognized and adversely effects wildlife through multiple mechanisms.

Hand it to the coyote (Canis latrans) for its ability to exist with humans. The resilience of this animal can be attributed to its natural instincts, remarkable intelligence and survivability. Opportunistic is another word that can be used to define them. Once an animal roaming the mid-west prairies, their territory has expanded throughout the North American continent and beyond. Coyotes demonstrate their wily nature by meeting the challenges of the American landscape.  

Progression of coyote range expansion throughout North America and Mexico. (7) Click to enlarge. 

Precise population estimates of coyotes in the United States are not available and unclear at best. However, to put it in perspective, the California Department of Fish and Game estimates a population range of  250,000  to 750,000 animals.(1)  The greater metropolitan area of Chicago estimates home to between 200-2000 coyotes. (3) The coyote population in New York during the summer is approximately 20,000-30,000. (2)  In March 2010, a lone coyote led a police chase through lower Manhattan, deep in New York City.

Coyotes can thrive in suburban settings and even some urban ones creating a concern for public health. A study by wildlife ecologists at Ohio State University yielded some surprising findings in this regard. Researchers studied coyote populations in Chicago over a seven-year period (2000–2007), proposing that coyotes have adapted well to living in densely populated urban environments while avoiding contact with humans. They found, among other things, that urban coyotes tend to live longer than their rural counterparts. (3)

As with most all wild animals, the coyote population represents a reservoir for diseases. Zoonotic (animal to human) diseases in particular are on the rise, comprising 75% of emerging infectious diseases. Viruses, bacteria, fungi, internal and external parasites, and other pestilence are only the headings for what’s out there.

Fortunately, the rabies virus is rather uncommon in coyotes as reported. The only exception was the 1974-1998 rabies epizootic (epidemic in animals) in south Texas. The world’s largest wildlife oral rabies vaccine (ORV) drop, 11.6 million doses covering over 189.6 square miles, was performed beginning in 1995 and led to the total elimination of the domestic dog-coyote (DDC) variant by 2006. (4) A study performed by the USDA, APHIS, Wildlife Services, National Wildlife Research Center concluded; “In Texas, the use of the ORV stopped the northward spread and led to the progressive elimination of the DDC variant of rabies in coyotes”. (5) This campaign was a win for our tax dollars as well. The economic evaluation study yielded “total estimated benefits of the program approximately ranged from $89 million to $346 million, with total program costs of $26,358,221 for the study period”. This represents benefit-cost ratios that ranged from 3.38 to 13.12. (5)

Coyote rabies surveillance reported by the Center for Disease Control (CDC) for 2010 declared 10 confirmed cases. None of these cases were DDC variant, which remains non-detected from the populations. The raccoon variant and skunk variant represented 8 (AL, GA, NC, NJ, NY, NYC) and 2 (CA, CO) cases respectively. (6)These coyote rabies cases were diagnosed from New York City (1) on the east coast to California (1) in the west, confirming the widespread distribution of this terrestrial carnivore. An interesting fact that comes from this data is that the coyote is not a player in the zoonotic rabies front. From a public health concern, a human has a significantly greater chance of contracting the disease from the backyard domestic cat.

Canine Distemper Virus is an enzootic disease (prevalent in an animal population) in the coyote. The neurological form is rightfully confused with a rabies infection as the two appear similar clinically. Humans are not susceptible to the disease, however it is highly contagious to dogs. Greater Yellowstone Park has a dynamic management study to assist with the surveillance of the disease enzootic in the parks coyote population.

The parasitic disease Sarcoptic mange is what gives the animal the “mangy” look. Caused by the mite Sarcoptes scabei, the disease in humans is called Scabies. Severely affected coyotes are unsightly and are perceived as threatening by their appearance. The compromised condition may explain the increased frequency of nesting and scavenging in suburban areas, especially in daylight hours. Coyotes with extensive mange infections are not considered aggressive as concluded by The Cook County, Illinois, Coyote Project.(7) Human infections from animal sources are short-lived and self-limiting due the highly host species-specific nature of the bug.

A recent hot epidemiological study conducted in Santa Clara County, California, identified coyotes as a wildlife reservoir for a disease caused by Bartonella vinsonii subsp. Berkhoffii .(8) The disease in humans is characterized by endocarditis, an inflammation of the interior lining of the heart. The study was prompted by the coyote bite of a child who developed symptoms compatible with Bartonella infection. Among 109 coyotes sampled, 31 animals (28%) were found to be bacteremic and 83 animals (76%) had Bartonella vinsonii seropositve antibodies. The disease is thought to be transmitted by insect vectors (ticks, biting flies, fleas), however further studies are necessary to elucidate additional modes of transmission to humans.(8) Bartonellosis in domestic cats is commonly called “cat scratch fever”, caused by a different species variant of Bartonella. The role coyotes play in this emerging infectious zoonose and public health concern are yet to be resolved.

Additional diseases exist in the coyote populations warranting public health attention. Anyone concerned with coyote interaction and communicable diseases will need to seek information relative to their geographical location. The ubiquitous nature of this animal and the corresponding diseases posing risks to humans and domestic animals respectively are regionally specific.

Coyotes are here to stay. Most every state (excluding Hawaii) has a control program in effect to manage the public health risks and deprivation to human welfare. The Humane Society of the US has issued techniques to resolve coyote conflict and how to discourage coyotes.  Project Coyote champions innovative solutions to live in peace with the coyote despite differences, especially in terms of human policy. (9) A collaborated and integrated management approach is required to maintain a balance of needs for this specie of animal and humans. Wildlife specialist Jeffery Green summarizes; “regardless of the means used to stop damage, the focus should be on damage prevention and control rather than elimination of coyotes”. (10)

Pet owners need to adapt to coyote presence and take precautionary measures in securing their animal’s health and safety. Routine core vaccinations and other preventative health care are effective in stopping the transmission of nearly all the important diseases from the coyote to a pet animal.

Coyote attacks on humans are rare; the coyote human avoidance factor is responsible for the low incidence. In the cases of human attacks, approximately 30% were reported as humans feeding coyotes. (8) Additionally, greater than 50% of the human attack cases were in California, (8) where coyotes have a longer history of habituation with humans.

A person who sees a coyote should feel lucky since they avoid humans and are mostly invisible.

The most important advice to prevent human exposure is: do NOT feed coyotes and ensure your environment is NOT coyote friendly. Any attempt to domesticate or habituate the coyote will surely be a kiss of death for its existence. Survival of coyotes is dependent on living side by side but not together with humans.

The “tricksters still run wild and provoke all sorts of all-too-human difficulties, pitting the spirit of the wild against the sturdy values of our American farmers and their need to protect livestock. Somehow we need both”. (11)

Our Canadian neighbors at The Royal Canadian Geographical Society  conclude; “the more we cut down habitat and build, the happier the scavenging and opportunistic coyote”. (12)

As they say in Texas, “when the human population fails, cockroaches and coyotes will survive”. (13)

References:

  1. L.A. County Department of Animal Care and Control website. Accessed June 15, 2012. Available at: http://animalcare.lacounty.gov/coyote.asp
  2. New York State Department of Environmental Conservation website. Accesses June 15, 2012. Available at: http://www.dec.ny.gov/animals/9359.html
  3. World Science website: Thriving under our noses, stealthily: coyotes.  Accessed June 13, 2012. Available at:  http://www.world-science.net/othernews/060105_coyotefrm.htm
  4. Texas Department of State Health Service website. Accessed June 12, 2012. Available at: http://www.dshs.state.tx.us/idcu/disease/rabies/orvp/statistics/
  5. Stephanie A. Shwiff, PhD; Katy N. Kirkpatrick, BS; Ray T. Sterner, PhD. Economic evaluation of an oral rabies vaccination program for the control of a domestic dog-coyote rabies epizootic: 1995-2006. JAVMA, Vol.233, No.11, Dec.1, 2008. Available at http://www.avma.org/avmacollections/rabies/javma_233_11_1736.pdf
  6. Jesse D. Blanton, MPH; Dustyn Palmer, BA; Jessie Dyer, MSPH; Charles E. Rupprecht, VMD,PhD. Rabies surveillance in the United States during 2010. Vet Med Today: Public Veterinary Medicine. JAVMA, Vol. 239, No. 6, September 15, 2011. Available at: http://avmajournals.avma.org/doi/pdf/10.2460/javma.239.6.773
  7. The Cook County, Illinois, Coyote Project website. Accessed June 13, 2012. Available at: http://urbancoyoteresearch.com/Coyote_Project.htm
  8. Chang CC, Kasten RW, Chomel BB, Simpson DC, Hew CM, Kordick DL, Heller R, Piedmont Y, Breitschwerdt EB. Coyotes (Canis latrans) as the reservoir for a human pathogenic Bartonella sp.: molecular epidemiology of Bartonella vinsonii subsp. Berkhoffii infection in coyotes from central coastal California. J Clin Microbiol. 2000 Nov; 38 (11): 4193-200. Available at: http://www.ncbi.nlm.nih.gov/pubmed/11060089
  9. Project Coyote website. Accessed June 15. 2012. Available at: http://www.projectcoyote.org/programs.html
  10. Jefferey S. Green, Urban Coyotes: Some Summary Thoughts. Proceedings of the 12th Wildlife Damage Management Conference (D.L. Nolte, W.M. Arjo, D.H. Stalman, Eds. 2007
  11. Shake-Spear’s Bible.com website; Coyote: An Instant Classic. Post by Roger Strirtmatter, October 25, 2011. Accessed June 13, 2012. Available at: http://shake-speares-bible.com/2011/10/25/coyote-an-instant-classic/
  12. The Royal Canadian Geographical Society website. Accessed June 13, 2012. Available at: http://www.canadiangeographic.ca/wildlife-nature/?path=english/species/coyote/2
  13. Personal correspondence; James Wright; Tyler Texas. Retired Texas Department of State Health Service official.

Holy influenza, batman!

Typically when we think of flying things and influenza viruses, the first images that come to mind are wild waterfowl. Waterbirds are reservoirs for an enormous diversity of influenza viruses, and are the ultimate origin of all known flu viruses. In birds, the virus replicates in the intestinal tract, and can be spread to other animals (including humans) via fecal material.

However, a new paper expands a chapter on another family of flying animals within the influenza story: bats.

I’ve written previously about the enormous diversity of microbes that bats possess. This shouldn’t be surprising–after all, bats are incredibly diverse themselves, encompassing about a fifth of all known mammalian species. Though rabies is probably the most famous bat-associated virus, other viruses that have been isolated from bats include Nipah and Hendra viruses, SARS coronavirus, Chikungunya virus, Japanese and St. Louis encephalitis viruses, Hantaan virus (a relative of the Sin Nombre hantavirus), and filoviruses, among many others. And of course, a bat->pig->human cross-species infection ended up being a plot line in the recent movie, Contagion (modeled after Nipah virus). However, bats still remain chronically under-studied, despite the fact that they can carry so many potential human pathogens.

This new research expands our knowledge of bat viruses a bit. The authors examined 316 bats from eight locations in Guatemala in 2009-10. Rectal swabs were obtained and screened for influenza virus using molecular methods (looking for influenza virus RNA). Three of the samples tested positive, and all were from little yellow-shouldered bats (Sturnira lilium). This could indicate some clustering and transmission of the virus within bat colonies–and indeed, two of the bats were from the same area in the same year (2009). However, the third bat was captured in 2010 at a location 50 km away from the other two, suggesting that the virus may be more widespread than in just one colony.

When we discuss the epidemiology of influenza viruses, we talk about two genes: the HA gene, which encodes the hemagglutinin protein and allows the virus to bind to host cells; and the NA gene, which encodes the neuraminidase protein and allows the virus to leave an infected cell and spread to others. This is where the “H1N1” or “H5N1” nomenclature come from. The novel bat virus was a completely new H type–type 17 (provisional, they note, pending further analyses). The NA gene was also highly divergent, but they are awaiting further analyses to more definitively classify this gene. (Currently there are 9 recognized types of NA genes).

Though they weren’t able to culture out the flu viruses, the authors did do some molecular work suggesting that these novel bat viruses could combine with human viruses and form a functional recombinant virus. What implications could this have for human health? Well, hard to say. We still know very little about all the implications of any distinct type of avian influenza virus, or swine influenza virus, much less something completely foreign like bat flu. It’s interesting that, like birds, influenza virus in bats was found in the intestine (though lung samples were also positive). Can it cause an intestinal infection as well as an upper respiratory infection (the latter being more common in other mammal species)? Does it cause any signs of disease in infected bats at all? If they can get this bat virus to grow, all sorts of interesting lines of research are just waiting.

The article also mentions that seroepidemiological studies are currently being carried out to better understand the epidemiology of bat flu. Looking at PubMed, there is one reference to some similar studies carried out in the early 1980s, but I can’t access anything beyond the title. There also is a report of H3N2 influenza in bats in Kazakhstan, but that article is in Russian and also not readily available. Either way, everything old is new again, and it looks like interest in bat influenza has resurfaced after a 30-year lull. Who knows what else we’ll find lurking out there as interest continues to increase in the wildlife microbiome.

Reference

Suxiang Tong, Yan Li, Pierre Rivailler, Christina Conrardy, Danilo A. Alvarez Castillo, Li-Mei Chen, Sergio Recuenco, James A. Ellison, Charles T. Davis, Ian A. York, Amy S. Turmelle, David Moran, Shannon Rogers, Mang Shi, Ying Tao, Michael R. Weil, Kevin Tang, Lori A. Rowe, Scott Sammons, Xiyan Xu, Michael Frace, Kim A. Lindblade, Nancy J. Cox, Larry J. Anderson, Charles E. Rupprecht, & Ruben O. Donis (2012). A distinct lineage of influenza A virus from bats PNAS Link.