Wednesday, June 8, 2011

Now that's one huge pile of 'yote crap!.... with comments on wildlife diseases

Above: the massive pile of steaming canine crap found on May 6, 2011. Compare to the pictures below.  Note: the key in most of these pictures is roughly three inches long.

Could be from a big domestic dog....I supose you may say. 

True, I respond, but it has hair in it.

Ok....perhaps a farm dog was eating roadkill, you counter.

Possible, I consider, but it also has some sort of fruit husk or seed in it, and coyotes eat alot of that type of stuff.

Hmm, you ponder.  Well, domestic dogs might eat that too.  My dog will eat carrots sometimes.

A-huh.  Well, when we broke the scat up with a stick it was full of tape-worm proglottids, I mention.

Ew!, you cringe.  I hope that wasn't a domestic dog!

Me too!  Otherwise there's an owner somewhere that will be very unhappy when they find their dog scooting its butt across the carpet, only (on closer inspection) to find a tapeworm sticking out of its rear-end. I'm just being needlessly graphic.  The perks of having two mentors with backgrounds in Parasitology, I guess.


The scat above was placed near a trail intersection at one of my sites.  Last year at approximately the same time (April 21, 2010), I saw another rather large pile of scat at about the same location (isn't it great to have a library of poop pics on one's computer?).  It also had alot of hair in it...and some seeds or grain of some kind.

Above: the large canine scat found on April 21, 2010.

Compare the scat examples above to one I found in March of this year (below).  This picture depicts Coyote scat that is a size I am more used to seeing.

Notes on Coyote parasites:

The importance of understanding wildlife parasites and disease cannot be overstated.  Studying wildlife diseases and parasites is not particularly glamorous, especially compared to stuff like radio telemetry or camera trapping.  For example, macro-parasite research may involve sifting through excrement under a microscope or analyzing sections of intestines and other organs post-mortem.  Yet, parasites and diseases are an important source of mortality for wildlife.  They can potentially regulate stable populations, or be a major conservation concern for rare species.  There is also the possibility that wild animals may transmit diseases to pets and livestock.  Finally, wildlife diseases can result in zoonosis.  Zoonoses are infectious diseases that jump from non-human animals (wild or domestic) to humans, and back.  Thus, the study of parasites and diseases is incredibly relevant to wildlife management, conservation and human health.   

Wild Canids potentially suffer from, and carry, many infectious agents (ticks, lice, fleas, tapeworms, roundworms, viruses, etc.).  Woodroffe, et al. (2004) give a very nice overview of the general topic of infectious diseases that plague wild canids.  They review information that suggests wild canids may be particularly vulnerable to disease outbreaks, which they suggest has to do with aspects of their ecology. 
  • A high trophic status (feeding postition in the food chain): because canids are often higher on the food chain, they are exposed to diseases carried by prey.  Tapeworms and flukes, for example, are often contracted by a predator when it consumes the muscle of an infected prey animal.
  • Intolerance of other carnivores that may be competitors:  territorial conflict or competitive interactions among wild canids or other carnivores may increase the likelihood of contact with infected animals.
  • Living in social groups: this provides another avenue for contact with potentially infected individuals that a solitary animal does not face.  Canids in social groups will often lick and groom eachother.
  • Communication via feces and urine that may be infected: investigating or scent rolling in the scat of a sick individual may be a potential route for infection.
  • The fact that domestic dogs are also canids: as the authors point out, most domestic dog populations are regulated by humans, not disease.  Where there are large populations of people, there are usually large populations of dogs.  These domestic dogs can act as a source (or resevoir) for infectious diseases that may plague wild canids (remember also that in some regions of the world, "domestic" dogs are not vaccinated, and often allowed to roam freely). 
There has been a fair amount of published literature on the topic of diseases that impact canids, particularly as it pertains to Coyotes.  To my knowledge, the first thorough review of Coyote parasites and disease is Gier et al. (1978).  This is a chapter is Marc Bekoff's Coyotes: biology, behavior and management...a very good introduction to the basics of Coyote ecology.  Not a book for the lay-person, but an an excellent scientific reference for this species.  Since then a number of other papers on the subject have been published.

Examples of External Parasites that Affect Coyotes

Mange.-  According to Gies et al. (1978) there is potential for both sarcoptic mange and demodectic mange in Coyotes.  Sarcoptic mange is the result of a mite (Sarcoptes scabei) that burrows into the skin and lead to an acute itch.  Infected coyotes bite, scratche and rub at this itch (perhaps to the point of hair removal), and secondary bacterial growth can result.  Demodectic mange is the result of a different species of mite (Demodex canis) that feeds on the hair follicles, rather than burrowing into the skin.  This can also result in "hairless" coyotes.  Both of these parasites have apparently given rise to many current "chupacabara" reports.

Ticks.- Coyotes can become infested with any number of tick species.  These usually attach on the face or ears, where the hair is short.  According to Gies et al. (1978) only a few species of tick appear to actually "thrive on coyote blood".   Although coyotes have been found to carry the antibodies for Rocky Mountain Spotted Fever, a disease transmitted by ticks in the genus Dermacentor (such as the Long-Star Tick), they apparently do not exhibit clinical symptoms of the disease.

Due to urban/suburban sprawl and agricultural expansion, the potential for contact between humans, domestic animals and wildlife is on the rise.  This trend is likely to increase.  As humans alter landscapes, it is possible that we enhance habitat for species that may carry disease.  For example, habitat fragmentation has created an extensive network of "edges" across the landscape (areas where two habitat types meet, in this case where natural and altered habitats meet).  Edge habitats are conducive to some species, like White-tailed Deer (Odocoileus virginianus) and various rodents, which can carry the ticks that spread lyme disease. 

Information on Lyme Disease, which is spread by the black-legged or deer tick (Ixodex scapularis), and coyotes is sparse.  Several studies have found a link between deer densities and prevalence of the black-legged or deer tick (Rand et al. 2003).  The tick actually carries the bacterium that causes Lyme Disease internally, but the deer gives the tick a place to live, feed and reproduce (the deer is, therefore, considered a vector).  With higher deer densities comes more hosts for ticks, which can increase the prevalence of Lyme Disease.  For example, Rand et al. (2003) found that relatively few ticks were found on white-tailed deer when deer densities were less than 7/km-squared. 

The same group of researchers published another very interesting study in 2004 that focused on Monhegan Island (off the coast of Maine; Rand et al. 2004).  White-tailed Deer had been introduced to this island in 1955 and had experienced a large population increase over the following three decades.  In the 1980s, deer densities were estimated to be at 37/km-squared!  At that time, ~13% of the year round human residents of the island had contracted Lyme disease.  Estimates of tick desnities in the early 1990s were 6-17 adults ticks/ hectare, with 24-41% of these ticks carrying the Lyme disease bacterium.

From 1996-1999 all deer were removed from the island.  For a very brief period immediately after the removal of deer (fall 1999), tick densities and prevelance of ticks infected with the bacterium rose substantially (28 ticks/hectare and 75% infection rate with Lyme Disease).  But wait for it!  By the summer of 2003, these numbers had dropped dramatically, with tick densities estimated at a mere 0.67 ticks/ hectare and 29.4% infection rate.  Concurrently, Rand et al. also monitored tick densities and infection rates on a nearby reference island still populated by deer and found that tick densities had continued to gradually increase during this same time.

Lyme Disease sucks.  Trust me.  Anything that can reduce the potential for contracting it when in the outdoors is A-OKAY in my book.

Examples of Internal Parasites:

Tapeworms-. Tapeworms are a particularly common parasite in the intenstines of coyotes, with some 65-90% of coyotes examined being infected in some cases (Gies et al. 1978).  The most commonly reported tapeworm species in coyotes is Taenia pisiformes.  The larval form of these tapeworms encysts in the muscles of prey animals....such as rabbits, which are a primary prey species for coyotes.  When a coyote eats an infected rabbit, they ingest the cysts in the rabbit muscle.  The cysts then develop into adult tapeworms in the intenstines of the Coyote.  This adult tapeworm grows (sometimes it reaches 4 -10 inches in length), and as it grows it produces more and more segments called proglottids.  These proglottids each carry hundreds or thousands of tapeworm eggs.    When an infected coyote excretes, mature proglottids break off of the tapeworm's main body. These proglottids are then evacuated from the intestines with the excrement.  These proglottids eventually open and eggs get on the grass/vegetation near where the coyote left the scat.  Geis et al. (1978) reported finding up to 110 of these adult worms in an individual coyote....each producing many proglottids (segments)....and each proglottid producing thousands of eggs.  That's alot of tapworm eggs being broadcasted into the environment.  Rabbits that eat the vegetation pick up the eggs...which eventually lead to larval tapeworm cysts in the muscles of the rabbit and the parasite lifecycle starts a-new.

The canine tapeworm that likely poses the most serious threat of mortality to humans is Echinococcus granulosus.  The eggs can be accidentally ingested by humans from close contact with infected dogs.  The larval form of this parasite in people can result in a large concentration of larval tapeworms that collect in a structure called a hydatid cyst.  The cyst can be the size of a golf ball or even grapefruit, and typically forms on the liver, kidneys or brain.  Should this cyst rupture, release of this large volume of foreign proteins into the body at once may result in mortality from anaphylaxis.  Removal of the cyst can only be done through surgery.  The incidence of coyotes infected with this particular tapeworm is (apparently) not high.

Tapeworms, and other internal parasites like flukes, adversely affect coyotes in a variety of ways.  The tapeworm nourishes itself from tissues and other digested materials in the coyote's intestines....this obviously draws away nourishment/nutrients that would otherwise go directly to the coyote.  If tapeworm loads become too heavy, they can actually cause a blockage in the intestines.  They may also cause internal irritation or result in secondary infections in the instestines.

Roundworms.- Any number of roundworms, such as hookworms, are found in the gastrointestinal system of coyotes.  The hookworm Ancylostoma caninum attaches to the intenstinal lining and feeds on blood/tissue.  These worms may migrate around in the intenstines and each time it finds a new feeding location, it potentially leaves an open wound from the spot it was previously feeding at.  A study of coyotes in the Gulf Coast of Texas found that every individual analyzed may carry up to 250 hookworms each (Mitchell and Beasom, 1974).  This obviously can lead to internal bleeding, and secondary bacterial infections.

Filarlial worms, the most infamous of which being Dirofilaria immitis (the canine heart worm) infect coyotes.  The infection rate of canine heart worm in wild coyotes varies considerably (from 1-36% infection rate depending on location; Geis et al. 1978).  A study in Illinois found a state-wide prevalence of 16% infection in wild coyotes (Nelson et al. 2003).  This same study found that the heart worm infections (i.e. the number of worms present per individual coyote) were rarely heavy.  Furthermore, although low body weight and kindey fat (both indicators of overall health) were not correlated with heart worm infections among coyotes, infected females did have a lower reproductive success than uninfected females.

Viral Infections-.  The most well-known wildlife viral disease is probably rabies.  Until the late 1980s, rabies was recorded only sporadically in coyotes.  At that time, however, a substantial outbreak of rabies in coyotes ocurred, that also spread to domestic dogs, in Texas (Clark et al. 1994). Coyotes are not often considered one of the main host species for rabies....this is usually reserved Raccoons, Skunks, Foxes and also Bats, which accounted for 91% of all rabies cases during 2000.  Domestic species accounted for 7% of the rabies cases in that year, and the remaining 2% of cases were the result of 13 other mammal species (one of which was the Coyote; Krebs, et al. 2003).  Over a 40 year period (1960-2000) a total of only 2,851 cases of rabies were reported from animals OTHER THAN Raccoons, Skunks and Foxes (Krebs et al. 2003).  This represented only 1.3% of the >215,000 cases of animal rabies.  Of these, 22% of the cases included coyotes.  So...a pretty low incidence.

Distemper is another disease that affects coyotes.  A survey of 228 coyotes sampled in Texas revealed that 56% tested seropositive for distemper (Guo et al. 1986).  Unlike rabies, canine distemper does not affect humans....but it can be a threat to domestic dogs.  During a four-year study in Colorado, 57% of 72 sampled coyotes tested positive for distemper (Gese et al. 1991).

Probably the most complete treatise on wild animal diseases to-date is Williams and Barker (2001).  Check it out for further information.

Oh...and to be safe...never actually touch any wildlife scat that you encounter in the wild (like I need to tell you this).  :)

Literature Cited

Clark, K.A., S.U. Neill, J.S. Smith, P.J. Wilson, V.W. Whadford, G.W. McKirahan. 1994. Epizootic canine rabies transmitted by coyotes in south Texas. Journal of the American Veterinary Medicine Association 204:536-540.

Gese, E.M., R.D. Schultz, O.J. Rongstad, and D.E. Andersen. 1991. Prevalence of antibodies against canine parvovirus and canine distemper virus in wild coyotes in southeastern Colorado. Journal of Wildlife Disease 27:320-323.

Gier, H.T., S.M. Kruckenberg, and R.J. Marler. 1978. Parasites and diseases of Coyotes.  In Coyotes: biology, behavior and management. M. Bekoff (ed.). The Blackburn Press.  Caldwell, NJ.

Guo, W., J.F. Evermann, W.J. Foreyt. F.F. Knowlton, L.A. Windberg. 1986. Canine distemper virus in coyotes: a serologic survey. Journal of American Verterinary Medical Association 189:1099-1100.

Krebs, J.W., S.M. Williams, J.S. Smith, C.E. Rupprecht, and J.E. Childs. 2003. Rabies among infrequently reported mammalian carnivores in the United States, 1960-2000. Journal of Wildlife Diseases 39:253-261.

Mitchell, R.L. and S.L. Beasom. 1974. Hookworms in south Texas coyotes and bobcats. Journal of Wildlife Management. 38:455-458

Nelson, T.A., D.G. Gregory, J.R. Laursen. 2003. Canine heartworms in coyotes in Illinois.  Journal of Wildlife Diseases 39:593-599.

Rand, P.W., C. Lubelczyk, G.R. Lavigne, S. Elias, M.S. Holman, E.H. Lacombe, and R.P. Smith Jr. 2003. Deer density and the abundance of Ixodes scapularis (Acari: Ixodidae). Journal of Medical Entomology 40:179-184.

Rand, P.W., C. Lubelczyk, M.S. Holman, E.H. Lacombe, and R.P. Smith Jr. 2004. Abundance of Ixodes scapularis (Acari: Ixodidae) after the complete removal of deer from an isolated offshore island, endemic for Lyme Disease. Journal of Medical Entomology 41:779-784.

Williams, E.S. and I.K. Barker. 2001. Infectious Diseases of Wild Mammals (third edition). Iowa State University Press.  Ames, IA.

Woodroffe, R. S. Cleveland, O. Courtenay, M. K. Laurenson, and M. Artois. 2004. Infectious disease: infectious disease in the management and conservation of wild canids.  In Biology and Conservation of Wild Canids, D.W. Macdonald and C. Sillero-Zubiri (eds.).  Oxford University Press.


  1. I sit down with my morning coffee and find..this!
    Very interesting read, though.
    Also, very much appreciating modern veterinary medicine and that today is heartworm pill day for the dogs!

  2. With reference to your last sentence: In Africa safari and trail guides are regularly seen handling the scat/dung of large herbivores. In particular, that of elephant and rhino is often closely examined since the warmth of it gives a very good indication of when it was 'deposited'. This knowledge is not just of academic interest but useful in helping those on foot to ensure that they live to see another day. Personally I have a preference for coming across ice-cold dung rather that that which is still steaming!

    At the risk of spoiling Samantha's day further there is a local 'sport' known as 'bokdrol spoeg' - which translated means buck (bok) dropping (drol) spitting (spoeg). If you don't believe me just Google 'bokdrol spoeg'. The aim is to see how far one can spit one of the little rounded dung pellets left by buck such as kudu. I'm pretty sure that the rules differ among communities but a common denominator is probably the prior consumption of a fair bit of alcohol. The alcohol consumption following the competition is, of course, to get the taste out of you mouth.

  3. Sorry to ruin your coffee, Samantha! My mentor as an undergraduate would eat lunch at the same counter he dissected animal intestines looking for tapeworms under a microscope (he was "old school", as they say). So, I got hardened to disgusting things pretty quickly :) But, working with him (and teaching a parasitology lab as a graduate students) made me alittle paranoid about zoonotic infections.

    Jeremy....very interesting about the bokdrol spoeg! I'm gonna look that up as soon as I'm done typing this.....

    Also good point about the warmth of the scat, and I can understand it's application in a life or death situation, for sure. Perhaps the dung of those large mega-herbivores doesn't carry many diseases....I guess I really don't know.

    The closest we get to a bigger herbivore 'round here is the white-tailed deer. Out west they get Elk, Bison and the like...but not here. It's probably true that deer scat here in the US can pose little threat if ingested (at least compared to the wealth of stuff you can pick up from carnivore scat)....things like brucellosis are a possibility, I suppose, although I think this is rare....and of course there's good old E. coli, Giardia, Tularemia, etc.