The Presence of the Raccoon Roundworm Parasite (Baylisascaris procyonis) in Raccoon Fecal Samples as a Factor in the Decline of the Allegheny Woodrat (Neotoma magister): a Continued Assessment
The Presence of the Raccoon Roundworm Parasite (Baylisascaris procyonis) in Raccoon Fecal Samples as a Factor in the Decline of the Allegheny Woodrat (Neotoma magister): a Continued Assessment
ABSTRACT
The presence of the common raccoon (Procyon lotor) roundworm parasite, Baylisascaris procyonis, in local raccoon populations has previously been determined to be a cause of death in the Allegheny woodrat (Neotoma magister) and may be a major factor in the decline of the woodrat in Pennsylvania and other states in its historic northern range. In this study, continued efforts have been conducted in assessing the parasite as a cause in the decline of the woodrat. We have proceeded to test the hypothesis that healthy, stable woodrat populations will be found uncontaminated with B. procyonis, and sites at which woodrats are declining or recently extirpated will be found contaminated with the parasite. A standard centrifugal fecal flotation procedure for detection of the parasitic eggs, which was improved by Mullen (1994), was utilized in testing 14 raccoon fecal samples from 4 sites of local raccoon populations in south-central Pennsylvania, where woodrats are also presently found ("active") or at one time found ("extirpated"). The one stable site examined was Stoney Mountain (Dauphin County). The three extirpated sites include: Longs Gap (Cumberland County), Fort Richie (Franklin County), and New Baltimore (Somerset County). The presence of B. procyonis, however, was not found in any of the 14 samples tested. Previous studies conducted by Mullen (1994) also resulted in no detection of B. procyonis in both stable and extirpated sites. It should be noted that there has been a lack of information in Pennsylvania concerning the prevalence of B. procyonis in raccoon fecal samples as a factor in the decline of the Allegheny woodrat. Mullen’s (1994) results combined with the large number of samples tested in this study, especially for the Fort Richie site (8 samples), with no detection of the parasite, strongly suggests that B. procyonis may not be a factor in the decline of the Allegheny woodrat, in Pennsylvania at least.
INTRODUCTION
The second largest member of the native North American rats and mice (family Cricetidae) is the Allegheny woodrat (Neotoma magister) ("Allegheny Woodrat: Neotoma magister," 1991). Neotoma magister was believed to be a subspecies of the eastern woodrat Neotoma floridana, but has recently been identified by Hayes and Harrison (1992) as a unique species using analysis of woodrat mitochondrial DNA restriction sites. The small, furry body of the Allegheny woodrat is brownish-grey in color, while its feet and underside are white (Fig. 1). It has four digits per front foot, and five digits per hind foot. The woodrat weighs approximately nine ounces ("Allegheny Woodrat: Neotoma magister," 1991) and measures between approximately 38 cm to 46 cm in length (Merritt, 1987; Mullen, 1994). The distinctly bicolored (black above and white below) tail constitutes 15 to 20 cm of the total body length (Merritt, 1987; Mullen, 1994).
The Allegheny woodrat is not a prolific breeder and averages one to three young in each of two to three litters per year ("Allegheny Woodrat: Neotoma magister," 1991). These woodrats have an average life span of three years in the wild. They are primarily herbivores and tend to cache debris and food such as berries, fruits, nuts, and green vegetation. N. magister is also a very sanitary animal, usually defecating in the same exact area called a latrine, forming a pile high of dung (Mullen, 1994).
N. magister is primarily nocturnal. It is territorial and typically lives in limestone caves or broken rock habitats including boulder piles, cliff faces, or talus slopes (Poole, 1940; Doutt et al., 1967). Such habitats can be found throughout the limestone regions of the Commonwealth of Pennsylvania, and specifically at water gaps where boulder piles and cliff faces are rather abundant (Genoways and Brenner, 1985). Historically, the Allegheny woodrat generally ranged in the Appalachian Mountain System: from northern Alabama, west into Kentucky, Indiana, and Tennessee (Poole, 1940) through southern Ohio, West Virginia, western Virginia, Pennsylvania and into southern New York, northern New Jersey and western Connecticut (Genoways and Brenner, 1985). Since the early 1960’s, however, the woodrat’s range has been declining (Mullen, 1994). Today, N. magister has disappeared from most of Eastern Pennsylvania, and has been completely extirpated from the entire state of New York (from half-dozen known colonies in 1979 to none in 1987) and Connecticut (Bean, 1992; Hall, 1990) (Fig. 2). The Allegheny woodrat is now endangered in Pennsylvania, Ohio, New Jersey, Maryland, and Indiana (Hall, 1990; Genoways and Brenner, 1985; Mullen, 1994).
In recent years, the decline of N. magister has been the concern of much research. The assessment of the raccoon (Procyon lotor) roundworm parasite, Baylisascaris procyonis, as a major factor in the decline of the Allegheny woodrat, is currently under extensive study. An investigation conducted by Edwin M. McGowan, Endangered Species Unit, New York State Department of Environmental Conservation, clearly implicated B. procyonis in woodrat deaths in New York (1993b). In his study, McGowan, radio-collared woodrats and released them at a historic woodrat site in New York and then tracked them to determine their cause of death (1993b). In ten of the eleven known woodrat deaths, B. procyonis was the cause due to brain infestation. Thus, woodrats could be at an increased risk for B. procyonis infection because they habitually collect food and debris, which may include infected raccoon feces.
The ascarid, B. procyonis (Fig. 3), is a common large roundworm parasite typically found in the small intestine of raccoons-- its normal host. The parasite was first described as Ascaris procyonis by Stefanski and Zarnowski (1951), but then later re-classified by Sprent (1968). Adult male B. procyonis worms are about 12 cm long and females are 23 cm long (Kazacos and Boyce, 1990). As the primary hosts, raccoons apparently tolerate B. procyonis in their small intestine, and extensive migration of the parasite beyond the intestinal lumen does not seem to take place (Kazacos and Boyce, 1990).
Figure 3. Egg of Baylisascaris procyonis, showing developing embryo. Source: Michigan State University College of Veterinary Medicine http://cvm.msu.edu/courses/mic569/docs/parasite/baylis.html
B. procyonis has been shown to cause visceral and ocular larva migrans in a variety of other hosts, including humans (Sloss, Kemp, and Zajac, 1994; Kazacos and Boyce 1990). Larva migrans refers to the persistence and prolonged elongation of parasite larvae (the larvae live and move around, but they never mature to adults) in the tissues and organs of humans and animals, similar to those in the natural intermediate hosts (rodents, birds, and rabbits) of the parasite (Kazacos and Boyce 1990). Intermediate hosts become infected by accidentally ingesting infective B. procyonis eggs from environmental areas contaminated by raccoon feces (Kazacos and Boyce 1990). About 5 to 7% of ingested larvae enter the brain of intermediate hosts and usually cause CNS disease.
The life cycle of B.
procyonis (Fig. 4) shows how woodrats may become infected. Adult
female worms in the small intestine of raccoons produce eggs which
are shed in the feces (Kazacos and Boyce, 1990). Eggs reach their
infectivity in about three to four weeks under moderate temperatures.
Older raccoons become infested by ingesting larvae in the tissues of
intermediate hosts. Young raccoons become infested by ingesting eggs
with infective larvae. Juvenile raccoons are more susceptible to
infection via eggs because adult raccoons tend to have an age
resistance factor (Kazacos and Boyce, 1990). Again, B.
procyonis does not have much of an effect on its normal host, the
raccoon. Woodrats, however, can become infected by B.
procyonis if they cache infested raccoon feces along with their
food and then accidentally ingest the B. procyonis eggs in the
contaminated feces.
Figure 4. Life cycle of raccoon roundworm (from JAVMA 195, 1990).
The prevalence of B. procyonis, particularly in raccoons, decreases from northern to southern states, and, as noted by several authors, infection in raccoons is most common in the northern temperate regions of the midwestern and northeastern United States (Table 1) (Fig. 5) (Kazacos and Boyce, 1990; Bafundo and Kennedy, 1980; Dubey, 1986; Ermer and Fodge, 1986; Harkema and Miller, 1964; Jacobson, et al, 1982; Jones and McGinnes, 1983; Kidder, et al, 1989; Mumford and Whitaker, 1982; Schaffer, et al, 1981; Snyder and Fitzgerald, 1985). As indicated by Schaffer, et al. (1981), hunters have been importing a large number of raccoons from high density populations, primarily from the coastal plain, and releasing them into the Appalachian Mountains. Raccoons from along the coastal plain carry more parasites, and, when translocated, can spread them inland (Schaffer, et al, 1981). However, there is a lack of information in Pennsylvania concerning the prevalence of B. procyonis in raccoon populations, and further investigation is needed in order to determine if the parasite is a cause in the decline of the Allegheny woodrat.
|
State |
Geographic area |
Author |
Date |
Sample |
N |
Percent infected |
|
GA |
coastal/inland |
Harkema & Miller |
1964 |
direct |
22 |
0 |
|
GA |
coastal/inland |
Schaffer, et al |
1981 |
direct |
20 |
0 |
|
IL |
rural central IL |
Snyder & Fitzgerald |
1985 |
direct |
310 |
82 |
|
IN |
urban/rural centr IN |
Jacobson, Kazacos, et al |
1982 |
scat |
218 |
29 |
|
IN |
throughout state |
Mumford & Whitaker |
1982 |
direct |
25 |
0 |
|
NC |
coastal/inland |
Harkema & Miller |
1964 |
direct |
209 |
0 |
|
NC |
coastal/inland |
Schaffer, et al |
1981 |
direct |
23 |
0 |
|
NY |
GtLakes plain |
Ermer & Fodge |
1986 |
direct |
429 |
68 |
|
NY |
Ithaca urb/suburb |
Kidder, et al |
1989 |
scat |
243 |
20 |
|
OH |
urban Columbus |
Dubey |
1982 |
direct |
28 |
25 |
|
SC |
coastal/inland |
Harkema & Miller |
1964 |
direct |
64 |
0 |
|
TN |
plains/valley/mtn |
Bafundo et al |
1980 |
direct |
253 |
7.5 |
|
VA |
coastal/inland |
Harkema & Miller |
1964 |
direct |
6 |
0 |
|
VA |
mountain |
Jones |
1976 |
direct |
34 |
56 |
|
VA |
piedmont/plain |
Jones |
1976 |
direct |
38 |
0 |
|
VA |
coastal/inland |
Schaffer, et al |
1981 |
direct |
30 |
0 |
|
WV |
(w of Pittsburgh) |
Schaffer, et al |
1981 |
direct |
10 |
20 |
B. procyonis, in its egg and embryo states, is extremely resistant to environmental conditions and common disinfectants. The parasite is dangerous because of its resistance and ability to survive and infect such a wide range of hosts. Thus, examination of infected soil and raccoon feces from local raccoon populations, where woodrats are also presently found or at one time found, is an easy and effective way to assess B. procyonis as a factor in the decline of the Allegheny woodrat. A simple centrifugal-flotation procedure developed by McGowan (1993a) is used for assessing B. procyonis contamination in feces. It was also utilized and improved by Mullen (1994) in his feasibility study of raccoon fecal samples to determine the presence of B. procyonis in Allegheny woodrat habitats. We have continued Mullen’s work (1994) and methods by using his improved centrifugal-flotation technique in examining raccoon fecal samples collected from additional local woodrat populations that had not yet been assessed. We also proceeded to test the hypothesis that healthy, active woodrat populations will be found to be uncontaminated with B. procyonis and sites at which woodrats are declining or recently extirpated will be contaminated with the parasite.
METHODS
Raccoon fecal samples were
collected from 14 sites in the south-central Pennsylvania region and
then analyzed for the presence of B.
procyonis. The collection took place in the Cumberland, Franklin,
Dauphin, and Somerset counties. The samples were collected in plastic
zip-lock bags and then kept frozen. Some samples contained the latex
gloves used to pick up the possibly infected samples. (See Stein
(1993) for complete information on search and collection procedure of
samples.) Cal Butchkoski and Jim Kennedy have investigated many
Pennsylvania Woodrat Metapopulations (Fig. 6). The fourteen sites in
our study that were sampled and tested include: 2 different samples
from Longs Gap (Cumberland County, PA), 8 different samples from Fort
Richie (Franklin County, PA), 3 different samples from Stoney
Mountain (Dauphin County, PA), and 1 from New Baltimore (Somerset
County, PA) (Fig. 6).
PROTOCOL OVERVIEW
The samples collected were tested using the centrifugal-flotation procedure developed and described by McGowan (1993a), but we followed Mullen’s (1994) improved techniques. The method is cost-effective, easy and efficient in separating parasitic eggs from soil and feces and prepares them for microscopic analysis. The procedure is based upon the specific gravity between eggs of B. procyonis, the flotation media, and fecal debris (Mullen, 1994). The fecal debris is suspended in Sheather’s sucrose solution. When this mixture is centrifuged for 5 minutes at 2,000 RPMs, the parasite eggs will float to the top of the centrifuge tube and collect onto the plastic coverglass situated on top of the tube (McGowan 1993: Mullen 1994). The plastic coverglass can be placed onto a glass slide, sealed with clear nail polish, and then examined microscopically.
In the slide examinations, two to three sub-samples of each fecal sample were used. Mullen (1994) used three sub-samples for each fecal sample examination. In Mullen’s analysis, the three sub-samples were always consistent. This provided confidence that two sub-samples were enough for an appropriate analysis. Also, due to the amount of sample, or otherwise, shortage of materials (i.e. Sheather’s Solution) in this study, two sub-samples were analyzed instead of three. Along with microscopic analysis, a video set-up was used in order to study the samples on a monitor. This often helped to lessen the tediousness of extensive slide examination and helped to speed up analysis. Mullen (1994) recorded his data on notebook data sheets, but he recorded later data onto computerized data spreadsheets for convenience. Data in this investigation, however, was always recorded manually onto notebook data sheets, and sketches were included as well. Using Kodak Gold 100 speed film, photographs of "other" common eggs, pseudoparasites (i.e. fungal spores), or other interesting organisms were also taken for reference. The number of each (photo) negative was recorded on the notebook data sheets that corresponded to the particular specimen that was being photographed. The backside of the photographs were labeled with: negative number and film roll number, sample number, magnification, location of the site, date analyzed and photographed, and photo number corresponding to the notebook data sheets.
RESULTS
The raccoon fecal samples were collected and then analyzed from the fourteen sites (Table 2). In this study, the woodrat status of each site was examined by researchers for fresh or old woodrat sign at the time the raccoon scat collection was made. On the basis of their personal communications, woodrat populations are here considered "extirpated" at the Fort Richie, Longs Gap, and New Baltimore sites and "active" at Stoney Mountain. In our study, 8 fecal samples were collected from Fort Richie, 2 fecal samples were collected from Longs Gap, 3 fecal samples were from Stoney Mountain, and 1 fecal sample was collected from New Baltimore, PA. There were a total of 37 slides prepared and then examined: 3 for most samples and 2 each for Fort Richie sample #2 and Fort Richie samples #11-14. Slide preparation took about 10-15 minutes. Each slide took approximately 30-45 minutes to analyze by microscope and/or video monitor. Two control slides positive for B. procyonis were prepared and used as standards for comparison and identification of the parasite if found in the fecal samples. Laboratory analysis resulted in no detection of the B. procyonis parasite in any of the samples. Other items, however, which most of the time were not specifically identified, were found (Figs. 7-18 [not included in Web site]).
TABLE 2. List of sites tested for eggs of the raccoon roundworm parasite Baylisascaris procyonis by examination of raccoon (Procyon lotor) fecal samples collected from known Allegheny woodrat (Neotoma magister) habitats.
SAMPLE WOODRAT STATUS DATE ANALYZED RESULT Fort Richie: extirpated #1a,b 18-Oct-94 No B. procyonis eggs found #1c 25-Oct-94 No B. procyonis eggs found #2a,b,c 25-Oct-94 No B. procyonis eggs found; other, small parasite eggs in
2c? #3a,b,c 27-Oct-94 No B. procyonis eggs found; much fecal debris #4a,b,c 2-Nov-94 No B. procyonis eggs found; fungal spores; pollen
grains? #11a,b: Site "R", 2100M E. of W. Vent 21-Nov-94 No B. procyonis eggs found; fungal spores; pollen
grains? #12a,b: Site "R" No B. procyonis eggs found; pollen grains? other clear, parasite eggs? #13a,b: shaft, 350M E. of W. Vent 21-Nov-94 No B. procyonis eggs found #14a,b 21-Nov-94 No B. procyonis eggs found Longs Gap: extirpated 3-Nov-94 #5a,b,c No B. procyonis eggs found; seed in 5a? other parasite
eggs? #6a,b,c No B. procyonis eggs found Stoney Mt. active 7-Nov-94 #7a,b,c, No B. procyonis eggs found; honey-comb like
structures (spider eyes?); possible insect fragments #8a,b,c No B. procyonis eggs found; clustered eggs/cells? fungal spores #10a,b,c: Ellendale Forge No B. procyonis eggs found; other small parasite
eggs? fungal spores New Baltimore extirpated 13-Nov-94 No B. procyonis eggs found; brown egg/cells? fungal
spores
DISCUSSION
McGowan’s (1993a) procedure, which Mullen (1994) improved upon, was quick and easy to use. There were no major difficulties encountered. Using nail polish to seal the plastic coverglasses was useful, but sometimes it would not last if an insufficient amount was applied. Air bubbles would then develop and evaporation sometimes occurred, and this posed a problem when trying to relocate a certain organism if re-analysis were to be performed. Microscopic analysis, at times, tended to become quite tedious and painstaking. In order to remedy this, a video-set up onto the microscope proved to be helpful. Analysis of the samples on a monitor screen allowed for a wider viewing area and quicker scanning. Clarity was sometimes sacrificed, but in such instances, one could return to the microscope.
Photographs were taken of interesting "other" eggs, pseudoparasites, and other unidentifiable items. Possible pollen grains and fungal spores (Figs. 9 and 15, respectively [not included in Web site]) were often found in the samples. Many interesting items were found, but identification was not a simple task. As in Mullen’s study (1994), many parasitic eggs were similar in size, shape, and color, and final identification was difficult. B. procyonis, though, is very distinct in its morphology. Unfortunately, no eggs of its kind were found in our samples.
Safety was an important factor and serious concern during preparation of samples using the centrifugal-flotation technique. Airborne infection of B. procyonis eggs or other parasitic eggs was a danger. Thus, a respirator, latex gloves, and a lab coat were worn throughout experimentation in order to prevent possible infection. The lab area and materials used were washed with 70% ethanol before and after each experiment. All contaminated materials that were used in each experiment were discarded in a trash bag labeled as biohazardous.
In this follow-up study, we expected a high frequency of B. procyonis in the fecal samples at "extirpated" sites, and little or no raccoon roundworms at stable, "active" woodrat populations (Mullen, 1994). We expected that for the one active site, Stoney Mountain, no presence of B. procyonis would be found. And, this was the case-- the woodrat population is presently stable. In the three extirpated sites examined-- Longs Gap, Fort Richie, and New Baltimore-- we predicted that the collected fecal samples would be contaminated with the parasite, however, this was not the case. The largest collection of different samples (eight) from the same site was done at Fort Richie in Franklin County, PA. A larger number of sites from a wider range of locations were examined for this study than had been available previously, and yet no parasitic roundworm eggs were detected at any of the extirpated sites. It seems unlikely that infected fecal samples escaped collection because a large enough sample at each site was usually taken. There has been a lack of information in Pennsylvania concerning the prevalence of B. procyonis in raccoon fecal samples as a factor in the decline of the Allegheny woodrat. The results of this study, combined with Mullen’s (1994) results, strongly suggest that B. procyonis is not a major factor in the decline of the Allegheny woodrat, especially in the south-central regions of Pennsylvania. The parasite could simply vary geographically, and its detection must undergo more research. Thus, continued analysis of more fecal samples is needed in order to determine the true cause of decline in the Allegheny woodrat.
Other theories that may explain the decline of the woodrat include: reduced winter food supply (due to the initial assault of the gypsy moths on Pennsylvania oak trees-- reduced supply of acorns) and severe winters (during the late 1970’s-- pushing the woodrat’s range further south) (Bean, 1992). There may also be other factors that are complicating the detection process of B. procyonis in the decline of woodrats. For example, raccoons have a wide range of homes (Merritt, 1987), and they may not be encountering woodrat habitats very often (Mullen, 1994). Mullen (1994) has also pointed out that raccoons frequently shed the parasite in the winter, but are reinfected in the spring (Kazacos, personal communication). Because B. procyonis also infects a variety of other hosts, further research is needed to fully understand reasons for woodrat extinction due to this parasite. Further investigation could then be applied to other target hosts and, thus, possible negative impacts upon in these species could be prevented.
I would like to thank Sean Mullen for his advice and instructional help, especially in the centrifugal fecal flotation procedure and photographing techniques.
The scat collection for this study was done by Jim Hart, who supplied the Fort Richie samples, Jim Kennedy and Cal Butchkoski for the sample from the New Baltimore site, and Professor J. Wright for the Longs Gap samples and the Stoney Mountain sample.
I would also like to express my thanks to Professor Janet Wright for her constant advice and help in continuing this project.
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