Why Parasites?

Brief intro from Dr. Rollins coming soon.

Eight years ago we sat in a motel room in Sweetwater with a team of 10 scientists from Texas A&M, Texas A&M – Kingsville, Texas Tech University, and the University of North Texas.  We had been given a charge from Rick Snipes, President of the Rolling Plains Quail Research Foundation.  Our charge was to design and conduct a comprehensive scientific investigation into disease (in the broadest context) as a possible explanation for the decline of bobwhites in the Rolling Plains.  Over the next 24 hours, we pondered pathogens and parasites, and the procedures and collaborations that would be necessary to pull it off.

Read more about this project

RPQRF’s Position Statement on Eyeworms & Cecal Worms

What We Know: Eyeworms

  • Rolling Plains ecoregion is the hot spot for infection, typically 50-70% of birds infected (up to 100% in some areas); 8X more prevalent in bobwhite from Rolling Plains vs South Texas Plains;
  • Epizootic event in 2013 demonstrated the potential for rapid spread of infection;
  • 107 worms found in a single bird (Note: our more recent surveillance counted 185 eyeworms in a bird from RPQRR);
  • Feed on tissues and glands within the eyes and nasal sinuses;
  • Cause scarring of the cornea as well as damage to other eye tissues; thus providing a mechanism for reduced vision and/or fitness and may explain reports of quail flying into stationary objects
  • Several potential intermediate hosts have been identified, including cockroaches, field crickets, and several species of grasshoppers;
  • 96% related at the DNA level to the Loa loa, a central African human eyeworm known to cause blindness;
  • New molecular techniques are available to allow for on-site, non-lethal sampling of quail to detect eyeworm infection.

What We Know: Cecal Worms

  • Very common throughout the Rolling Plains with 80-90% of birds infected (up to 100% in some areas);
  • Over 1,700 worms have been found in a single bird;
  • Has been associated with gross pathology, distension of the ceca, and lack of digesta; thus providing a mechanism for reduced fitness, including weight loss;
  • 90% related at the DNA level to the Ascarid, or roundworm, of dogs and cats which if left untreated can cause weight loss, malnutrition, and eventual death;
  • 13 different species of grasshoppers have been identified as potential intermediate hosts;
  • New molecular techniques are available to allow for on-site, non-lethal sampling of quail to detect cecal worm infections.

What We Think

  • Eyeworms reduce vision and likely predispose quail to predators, flying into objects (e.g., barns, fences, trees), and have difficulty finding food;
  • Cecal worms deplete nutrients and may lead to malnutrition, energy loss, reduced breeding potential, and impair ability to evade predators;
  • Parasitic infection suppresses the immune system which may leave quail susceptible to secondary infections;
  • Because parasites are long-lived, over time an infection may increase until it is eventually fatal, ultimately reducing populations;
  • Even low infections may tip the scales against quail in an already challenging environment, e.g. predation by Cooper’s Hawk;
  • Implementation of a medicated feed (“Quail Guard”) twice annually (Spring and late Summer) will reduce parasitic infection in wild quail populations;
  • Based on the “weight of the evidence” as well as field and laboratory data, we believe that quail are impaired by parasitic infection and their reproduction and survival are reduced.

What We Don’t Know (at this point)

  • How many parasites can a quail harbor before they are impaired? Is it a linear relationship or is it dependent on the bird-like people and alcohol consumption?
  • What level of infection represents an “action threshold” which would justify treatment?
  • How does availability of infected intermediate hosts vary from one year to the next?
  • Is there an effect on the immune system of quail? Do high infections leave them more susceptible to other diseases?
  • Can the “boom and bust” cycles of quail be reduced by addressing parasite-related concerns?
  • What are the consequences of infections of multiple parasite species?

Where We’re Headed

  • Dr. Kendall’s Wildlife Toxicology Laboratory has developed a medicated feed which we hope earns FDA approval soon and becomes available in 2019;
  • WTL is deploying a Mobile Research Laboratory to monitor parasitic infection in quail throughout the Rolling Plains;
  • WTL is conducting laboratory studies to evaluate how parasites affect vision;
  • WTL plans to evaluate bobwhite immune response to parasitic infection;
  • WTL will continue to add to the “weight of the evidence” supporting the hypothesis that parasites are affecting wild quail;
  • RPQRR plans to evaluate the efficacy of the medicated feed on survival and breeding success upon approval and availability of the medicated feed;
  • RPQRR received about 1,000 quail heads from across West Texas this past Jan-Feb to ascertain the current status/distribution of eyeworms and evaluate field vs. lab techniques for assessing eyeworm infection. RPQRR will produce “heat maps” to identify where prevalence is highest on an annual basis.

Related Webisodes

Publications of the Wildlife Toxicology Laboratory Texas Tech University

  1. Dunham, N.R., Soliz, L.A., Fedynich, A.M., Rollins, D., Kendall, R.J. 2014. Evidence of an Oxyspirura petrowi epizootic in Northern bobwhites (Colinus virginianus). Journal of Wildlife Diseases. 50:552-558.
  2. Dunham, N.R. and Kendall, R.J. 2014. Evidence of Oxyspirura petrowi in migratory songbirds found in the Rolling Plains of West Texas. Journal of Wildlife Diseases. 50:711-712.
  3. Dunham, N.R., Peper, S.T., Baxter, C.E., Huddleston, J.E., Kendall, R.J. 2014. The parasitic eyeworm Oxyspirura petrowi as a possible cause of decline in the threatened Lesser Prairie-Chickens (Tympanuchus pallidicinctus) found in Kansas. Plos One. 9:9.
  4. Kistler, W.M., Parlos, J.A., Peper, S.T., Dunham, N.R., Kendall, R.J. 2016. A quantitative PCR protocol for detection of Oxyspirura petrowi in Northern bobwhites (Colinus virginianus). PLoS One. 11(11):e0166309.
  5. Dunham, N.R., Reed, S., Rollins, D., Kendall, R.J. 2016. Oxyspirura petrowi infection leads to pathological consequences in Northern bobwhite (Colinus virginianus). International Journal for Parasitology: Parasites and Wildlife. 5:273-276.
  6. Dunham, N.R., Peper, S.T., Downing, C., Brake, E., Rollins, D., Kendall, R.J. 2016. Infection levels of the eyeworm Oxyspirura petrowi and caecal worm Aulonocephalus pennula in the Northern bobwhite and scaled quail from the Rolling Plains of Texas. Journal of Helminthology. 91(5):569-577.
  7. Dunham, N.R. and Kendall, R.J. 2016. Eyeworm infections of Oxyspirura petrowi, Skrjabin, 1929 (Spirurida: Thelaziidae), in species of quail from Texas, New Mexico and Arizona, USA. Journal of Helminthology. 91(4):491-496.
  8. Kistler, W.M., Hock, S., Hernout, B., Brake, E., Williams, N., Downing, C., Dunham, N.R., Kumar, N., Turaga, U., Kendall, R.J. 2016. Plains lubber grasshopper (Brachystola magna) as a potential intermediate host for Oxyspirura petrowi in Northern bobwhites (Colinus virginianus). Parasitology Open. 2(e7):1-8.
  9. Dunham, N.R., Bruno, A., Almas, S., Rollins, D., Fedynich, A.M., Presley, S.M., Kendall, R.J. 2016. Eyeworms (Oxyspirura petrowi) in Northern bobwhites (Colinus virginianus) from the Rolling Plains Ecoregion of Texas and Oklahoma, 2011-2013. Journal of Wildlife Diseases. 52(3):562-567.
  10. Henry, C., Brym, M.Z., Kendall, R.J. 2017. Oxyspirura petrowi and Aulonocephalus pennula infection in wild Northern bobwhite quail in the Rolling Plains ecoregion, Texas: Evidence of a possible die-off. Archives of Parasitology. 1:109.
  11. Henry, C., Brym, M.Z., Blanchard, K.R., Kendall, R.J. 2017. Helminth infection and Northern bobwhite (Colinus virginianus). Archives of Parasitology. 1(2):e102.
  12. Kalyanasundaram, A., Blanchard, K.B., Kendall, R.J. 2017. Molecular identification and characterization of partial COX1 gene from caecal worm (Aulonocephalus pennula) in Northern bobwhite (Colinus virginianus) from the Rolling Plains ecoregion of Texas. International Journal for Parasitology: Parasites and Wildlife. 6:195-201.
  13. Dunham, N.R., Henry, C., Brym, M., Rollins, D., Helman, R.G., Kendall, R.J. 2017. Caecal worm, Aulonocephalus pennula, infection in the Northern bobwhite quail, Colinus virginianus. International Journal for Parasitology: Parasites and Wildlife. 6:35-38.
  14. Brym, M.Z., Henry, C., Kendall, R.J. 2018. Potential parasite induced host mortality in Northern bobwhite (Colinus virginianus) from the Rolling Plains ecoregion of West Texas. Archives of Parasitology. 2:1.
  15. Kalyanasundaram, A., Blanchard, K., Henry, C., Brym, M.Z., Kendall, R.J. 2018. Development of a multiplex quantitative PCR assay for eyeworm (Oxyspirura petrowi) and caecal worm (Aulonocephalus pennula) detection in Northern bobwhite quail (Colinus virginianus) of the Rolling Plains ecoregion, Texas. Veterinary Parasitology. 253:65-70.
  16. Henry, C., Brym, M.Z., Kalyanasundaram, A., Kendall, R.J. 2018. Molecular identification of potential intermediate hosts of Aulonocephalus pennula from the Order Orthoptera. Journal of Helminthology. 13:1-6.
  17. Blanchard, K., Henry, C., Brym, M.Z., Kalyanasundaram, A., Kendall, R.J. 2018. Regional surveillance of parasitic infections in wild Northern bobwhite quail (Colinus virginianus) utilizing a mobile laboratory platform. Parasitology Open. 4:e14.
  18. Brym, M.Z., Henry, C., Kendall, R.J. 2018. Elevated parasite burdens as a potential mechanism affecting Northern bobwhite (Colinus virginianus) population dynamics in the Rolling Plains of West Texas. Parasitology Research. 117:1683-1688.
  19. Kalyanasundaram, A., Henry, C., Brym, M.Z., Kendall, R.J. 2018. Molecular identification of Physaloptera sp. from wild northern bobwhite (Colinus virginianus) in the Rolling Plains ecoregion of Texas. Parasitology Research. Published online July 7.

By Other Authors Supported by RPQRF:

Bedford, K. 2015. Parasitological survey of scaled quail from west Texas. Thesis. Texas A&M University, Kingsville.

Bruno, A., A. M. Fedynich, A. Smith-Herron, and D. Rollins. 2015. Pathological response of northern bobwhites to Oxyspirura petrowi infections. Journal of Parasitology 101:364–368.

Bruno, A., A.M. Fedynich, D. Rollins, and D.B. Wester. 2018. Helminth community and host dynamics in northern bobwhites from the Rolling Plains Ecoregion, U.S.A. Journal of Helminthology 1–7. https://doi.org/10.1017/S0022149X18000494

Ferro, P.J., O. Khan , C. Vuong , S. M. Reddy , L. LaCoste , D. Rollins , and B. Lupiani. 2012. Avian Influenza Virus Investigation in Wild Bobwhite Quail from Texas. Avian Diseases, 56:858-860.

Kubečka, B.W., A. Bruno, and D. Rollins. 2017. Geographic Survey of Oxyspirura petrowi Among Wild Northern Bobwhites in the United States,” National Quail Symposium Proceedings: Vol. 8, Article 84. Available at: http://trace.tennessee.edu/nqsp/vol8/iss1/84

Kubecka, B.W., N. J. Traub, V. V. Tkach, T.R. Shirley, D. Rollins, and A. M. Fedynich. 2018. Mesocestoides sp. in Wild Northern Bobwhite (Colinus virginianus) and Scaled Quail (Callipepla squamata). Journal of Wildlife Diseases, 54(3): In press.

Su, H., J. McKelvey, D. Rollins, M. Zhang,, D.J. Brightsmith, et al. 2014. Cultivable Bacterial Microbiota of Northern Bobwhite (Colinus virginianus): A New Reservoir of Antimicrobial Resistance? PLoS ONE 9(6): e99826. doi:10.1371/journal.pone.0099826

Villarreal, S.M., Fedynich, A., L. A. Brennan, and D. Rollins. (2012) “Parasitic Eyeworm (Oxyspirura petrowi) in Northern Bobwhites from the Rolling Plains of Texas, 2007–2011,” National Quail Symposium Proceedings: Vol. 7, Article 95.

Villarreal, S.M., A. Bruno, A.M. Fedynich, L.A. Brennan, and D. Rollins. 2016. Helminth Infections Across a Northern Bobwhite (Colinus virginianus) Annual Cycle in Fisher County, Texas. Western North American Naturalist 76(3):275-280.

Parasite FAQ

How do quail become infected with eyeworms?

Quail must consume an infected “intermediate host” (e.g., grasshopper, cricket, cockroach).  Once inside the quail’s crop, eyeworm larvae from the intermediate host escape, make their way into the esophagus, and move up to the lacrimal ducts, then migrate up into the eye.  This process can occur in less than 30 minutes.

Are these eyeworms only in quail?

No, they have been found in pheasants, lesser prairie chickens, mockingbirds, and several other species. Interestingly, we surveyed for their presence in wild turkeys on a site that had “high” infection rates of eyeworms. While the turkeys were eating arthropods (presumably infected with eyeworm larvae), only 1 of 104 turkeys had an eyeworm. Explain that discrepancy?

Read Host Specificity of Oxyspirura petrowi in Wild Turkey

Is the eyeworm native to North America?

Parasites aren’t typically classified as native or exotic. Skrjabin (1929) first characterized O. petrowi in Northeastern Europe, and early reports in the U.S. date back to the 1940s.

I've only heard of this in Texas—is it limited to there or does it occur elsewhere?

While the Rolling Plains ecoregion of Texas appears to have the highest infection rates, we have also found them in bobwhites from AL, OK, and VA.  They likely occur in KS and NE but we have not examined birds from those states.

Do eyeworms cause blindness in an infected quail?

They can irritate (i.e., cause inflammation) to the optic nerve and associated glands situated behind the eyes.  They can also produce scarring of the cornea.  Such pathology likely affects the quail’s vision.  Odds are it would be preyed upon before it became “blind.”

What percentage of bobwhites have eyeworms?

Since we began studying them in 2009, we typically find that 50-60 percent of the bobwhites harbor eyeworms.  Some sites have upwards of 80 percent infection.  Infections in the Rolling Plains are about 8X greater than bobwhites from south Texas.  Adult quail typically have greater infections than juvenile birds.

Are the birds okay for human consumption if they have eyeworms?

Yes, no concerns for human consumption . . . most of us don’t eat the heads anyway!

How do I know if my quail have eyeworms?

For initial inspection in the field, see Joe Crafton’s technique above (https://youtu.be/VSfwWONuU0Y ).  Also watch the video “How to Search for Eyeworms in Quail”.  Be aware however that both of these techniques underestimate the number of eyeworms, as many (probably most) reside behind the eyeball itself.  A complete dissection of the head is needed to get an accurate count.

So do you think eyeworms are worse now than in times past or is it just that we are aware that they exist now and know how to check for them?

We’ve known about eyeworms since early 1960s in bobwhites; they were noted in pheasants in the Midwest earlier than that. Information about them in quail essentially lay “dormant” for the past 50 years, because most parasite studies don’t look at/in/around the eyes–looking typically in the GI tract. Our “Operation Idiopathic Decline” study (initiated in 2011; see video at https://www.youtube.com/watch?v=xUfqw8dGk5E ) resulted in newfound interest in eyeworms.

Is there any credibility to the rumor that wild hogs assist in the spread of eyeworms?

I am not aware of any connection/rumor of feral hogs being involved in transmission of eyeworms–I don’t see any connection between the 2.

What’s the answer?

We are working with the Wildlife Toxicology Lab at Texas Tech to develop a medicated feed that will kill the eyeworms and cecal worms. Hope to have it commercially available in early 2019.

More Resources