Geographic Expansion of Baylisascaris procyonis Roundworms, Florida, USA

Photo credit Wisconsin Department of Natural Resources

Baylisascaris procyonis roundworms are common parasites of raccoons (Procyon lotor) in several regions of North America, Europe, and Asia. These parasites are increasingly recognized as a cause of larva migrans in humans (disease caused by the larvae of various nematode parasites), an infection that often results in severe neurologic sequelae or death. In addition, larva migrans has been documented in ≈90 species of wild and domestic birds and mammals. In the United States, B. procyonis roundworms are most prevalent in the midwestern, northeastern, and Pacific western states. Numerous surveillance studies have been conducted in the southeastern United States, and B. procyonis roundworms are most common in the mountainous regions of Virginia, Kentucky, and West Virginia. Geographic expansion of B. procyonis roundworms has been recently documented in Georgia. In 2002, 22% of raccoons sampled in DeKalb County, Georgia, a highly urbanized area near Atlanta, were positive for the parasite, and recently, 10% of raccoons sampled in Clarke County, Georgia, were positive. Whether this expansion is due to natural spread of the parasite among raccoons or to translocations of infected raccoons into naive areas is unclear. We document expansion of B. procyonis roundworms into northwestern and southeastern Florida. 

Photo credit National Wildlife Federation

 In 2006 and 2007, nine ascarids (>3 inches) (an ascarid is a nematode worm) were collected from the feces of an unrecorded number of raccoons admitted to a rehabilitation center in northern Florida. In September 2008, December 2009, and June 2010, 1 ascarid each was found in the feces of a 4- and a 6-month-old raccoon from Leon County, Florida, and 1 6-month-old raccoon from Wakulla County, Florida, after routine treatment with pyrantel pamoate (20 mg/kg). In July 2010, a juvenile (6-month-old) raccoon from Broward County, Florida, which had been admitted to a rehabilitation center, passed several ascarids (2 collected for testing) in its feces after ivermectin treatment (0.2 mg/mL) for mange. The 14 ascarids were preserved in 70% ethanol, and adult males were identified as Baylisascaris spp. on the basis of their morphologic characteristics (perianal rough patches). The ascarids were subsequently confirmed as B. procyonis.

Several previous studies did not detect B. procyonis roundworms in raccoons or latrine sites in central Florida (51 from Glades, Highlands, Hillsborough, and Orange counties), southern Florida (90 from around Miami and 64 fecal samples on Key Largo), and numerous counties throughout Florida (177). Historically, B. procyonis roundworms have been absent throughout most of the Southeast, but the parasite was recently detected in north-central Georgia. How the species became established in Florida remains unclear. Establishment could have resulted from natural dispersal of infected raccoons from B. procyonis–endemic areas; however, recent examination of several raccoon populations in southern Georgia failed to detect such infections. Alternatively, the parasites could have been introduced from the movement of infected raccoons, exotic pets (e.g., kinkajou [Potos flavus]), or natural wildlife intermediate hosts.

Additionally, because domestic dogs can serve as definitive hosts, an infected dog from a B. procyonis–endemic area may have passed eggs into the environment. Veterinarians in Florida should be aware of this possible zoonosis and carefully examine ascarid eggs detected in fecal specimens because B. procyonis–infected dogs often have mixed infections with Toxocara canis, Toxascaris leonina, or both, which have morphologically similar eggs. Physicians, veterinarians, and wildlife biologists in Florida should be aware of this serious pathogen and the likelihood its range will increase, as highlighted by the recent detection of B. procyonis roundworms in a kinkajou from southern Florida (Kazacos et al., unpub. data).

Typical raccoon latrines found in urban/suburban environments. (A) Latrine on a chimney ledge, illustrating the climbing abilities of raccoons and their tenacity in maintaining latrines. (B) Large latrine in the crotch of an oak tree approximately 3.5 m (15 feet) above ground. The sides of the tree were visibly stained with fecal residue that rain had washed down the trunk, contaminating a child’s play area below with Baylisascaris procyonis eggs. (C) Large latrine, in use for years on a house roof, unknown to the home owner. (D) Latrine site on the ground near downed timber and rocks in a suburban yard. Note the variety of fecal materials (including seeds, crustacean shells, and human refuse), reflecting the diversity of the raccoon diet. The homogeneous-appearing fresh scat in the center is composed of digested pet food. (E) Latrine on a stump in a suburban park with plants sprouting from seeds in the scat. Granivorous birds and mammals are attracted to such locations, as are curious children. (F) Raccoon scat hidden in leaf litter in a suburban back yard, indicating how occult contamination may be. Photo courtesy of the CDC.

This study also highlights the importance of wildlife rehabilitation centers as resources for the study of wildlife/zoonotic diseases. Animals admitted to rehabilitation centers are often ill or injured, which may increase pathogen shedding or transmission. Additionally, young raccoons are likely to be infected with B. procyonis roundworms, and kits as young as 3 months of age can be patent. Numerous fatal B. procyonis larva migrans infections have occurred among animals in rehabilitation centers and zoological parks. These infections were likely acquired when animals were housed in enclosures previously occupied by infected raccoons or when bedding or food became contaminated with B. procyonis–infected raccoon feces. In B. procyonis–endemic areas, cages used to house raccoons should be thoroughly decontaminated by flaming, or cages should be dedicated for use by raccoons. Because B. procyonis roundworms are zoonotic, persons in contact with raccoons should be alert to potential transmission routes and apply appropriate biosecurity procedures.

Yabsley MJ, Blizzard EL, Beck MF, Harsch S. Geographic expansion of Baylisascaris procyonis roundworms, Florida, USA [letter]. Emerg Infect Dis. 2010 Nov; [Epub ahead of print]


One response to “Geographic Expansion of Baylisascaris procyonis Roundworms, Florida, USA

  1. Pingback: Baylisascaris | Natural Health Techniques

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