Acknowledgements• I would like to thank my school and my teachers, Mr. Dusza (science) and Ms.

Robbins (math), for their support and guidance.

• I would also like to thank my parents for their help and supervision of my work.

References1. Centers for Disease Control and Prevention. Parasites – Toxocariasis (also known as

Roundworm Infection). Available at: https://www.cdc.gov/parasites/toxocariasis/gen_info/faqs.html. Accessed: October 2, 2017.

Finding Toxocara Eggs in Park Soil from Montgomery County, Pennsylvania, USA Devyn K. Stek 1

1 St. Teresa of Calcutta Education Center, Schwenksville, PA, USA

BACKGROUND• Toxocara spp. is a parasite commonly known as roundworm 1

• Most common reservoirs are dogs (Toxocara canis) and cats(Toxocara cati) 2

• Toxocara eggs are spherical to oblong, with a rough/pitted edge, andbrownish in color (Figure 1)

• Toxocara has a predictable life cycle 5 (Figure 2)

Figure 1. Toxocara Eggs

IMPACT ON HUMANS

• Toxocara spp. infection in humans is called toxocariasis 1

• Children are more frequently infected (~30% in 6-11 year olds) thanadults (~14%) 6-8

• Most infections have no symptoms and clear by themselves 9

• Symptoms include weight loss, malaise, fever, fatigue, and failureto grow 9

• Worms can move anywhere in the body 10

STUDY OBJECTIVE• The primary objective: to examine and describe the contamination level

of each park and sample for Toxocara eggs

– Independent variable: different samples tested

Table 1. Park and Sample Site Descriptions

STUDY PROCEDURES

Figure 4. Distribution of Toxocara Eggs Figure 5. Average Number of Toxocara Eggs per Park (95% CIs)

Contact: Devyn K. Stek St. Teresa of Calcutta Education Center256 Swamp Pk., Schwenksville, PA 19473 610-850-2476denise.stek@yahoo.com

Table 3. Chi-Square Test for Similarity/Difference

• Toxocara eggs were found in every park tested

– Soil sifting and the floatation technique with a sugarsolution was used

– Highest amounts in areas that could contain fooddroppings (e.g. picnic area) or places that could serveas a convenient bathroom for dogs (e.g. tree grove)

RESULTS

Table 2. t-Distribution Test and 95% Confidence Interval (CI) Determination

IDWeek 2018; San Francisco, CA, USA; October 3-7, 2018.

Poster #438

– Other reservoirs: foxes, birds, pigs, rodents, goats, rabbits,monkeys, and humans

– 75-90 µm (T. canis) or 65-70 µm (T. cati) 3,4

Figure 2. Toxocara spp. Life Cycle

– Higher likelihood of hand-to-mouth transmission of contaminatedsoil by kids

– Visceral larva migrans (VLM) = worm moving under skin

– Ocular larva migrans (OLM) = worm moving in eye

= ~70 people in the US go blind from toxocariasis

– Dependent variable: use of the floatation method with a sugarsolution to visualize Toxocara eggs using a microscope 11

STUDY QUESTIONS

• Are Montgomery County parks infected with Toxocara eggs?

• Can the float technique using a sugar solution be used to visualizethe number of Toxocara eggs in soil samples?

• What information can be learned from the number of Toxocara eggsin each sample?

• What comparisons can be made about the average number ofToxocara eggs found in each park?

• Toxocara eggs will be found in Montgomery County park soilsamples

• The float technique with a sugar solution will allow the visualizationand counting of the number of Toxocara eggs in soil samples

• The number of Toxocara eggs in each sample will vary; certainareas may contain more eggs than others

• Some parks will have a greater average number of Toxocara eggsthan others

STUDY HYPOTHESES

STUDY MATERIALS

• Gardening trowel

• Zip-lock plastic bags

• Sieve

• Glass cups

• Floatation solution

• ~20 mL plastic tubes • Plastic pipettes

• Glass slides/cover slips

• Microscope

• Identify parks (Table 1)

• Collect ~2 cups of dirt into a plastic bag

• Dry and sift sample using a 1/32-inch opening mesh screen

• Add 2 tablespoons of sifted soil to glass

• Add 1/4 cup of sugar floatation solution and stir 11

• Let mixture sit for 1 hour

• Transfer supernatant to a 20 mL tube and cap

• Let tube sit overnight

• Pipette 3 drops of surface fluid onto a glass slide and cover

• Examine the slide under 400X total magnification

• Count and record the number of Toxocara eggs seen in a full grid search

Figure 3. Park Locations in Montgomery County, PA

• Parks and samples varied in levels of contamination (Figure 3)

– Smallest samples (0 & 2 eggs) from Sanatoga Park

– Largest samples from Pottstown Memorial Park [52 eggs - picnicpavilion] and Heather Place Park [56 eggs - tree grove]

• 35 of 36 samples tested positive for Toxocara eggs

• Manderach Park (11.7 eggs [95% CI: 9.6, 13.8]) had significantly largeraverage number of eggs compared to Sanatoga Park (2.5 eggs [95%CI: 1.0,4.0]), Gerald Richards Park (4.0 eggs [95% CI: 3.8, 6.2]), and AlthouseArboretum (4.7 eggs [95% CI: 3.3, 6.1]) (Table 2A;Figure 4)

– Sanatoga, Gerald Richards, and Heather Place had similar averagenumber of eggs (χ2=3.97 < 5.99) (Table 2B)

• Highest average number of eggs recorded from Pottstown Memorial Park(18.2 eggs [95% CI: 4.1, 32.1]) and Heather Place Park (18.5 eggs [95%CI:3.5, 23.5]) (Table 2A; Figure 4)

– Both parks had very similar average number of eggs (χ2=0.02 <3.84)(Table 2B)

STUDY LIMITATIONS

• There are many different types of roundworms whose eggs allhave similarities and differences

– Pinworms, Ascaris, hookworms, Strongyloides, Trichinella,whipworm, and Baylisascaris

• Due to their similar appearance and size, no differentiationbetween T. canis and T. cati was attempted during this study

• A lack of formal parasitology training could have resulted incounting the wrong egg as Toxocara

• I especially would like to acknowledge Steven Silberman, DVM of Affordable Spayand Neuter (Pottstown, PA) for providing a Toxocara-positive sample as areference for my microscope work.

• I would also like to recognize Dr. Misoo Ellison for her guidance on additionaland future statistical analyses of my work.

Post-Study Analyses (credit: Misoo Ellison, PhD)

2. Marty AM. Toxocariasis Chapter 27, pages 411- 421 in Meyers WM, Neafie RC,Marty AM, Wear DJ. (Eds) Pathology of Infectious Diseases Volume I: Helminthiases.Armed Forces Institute of Pathology, Washington DC. 2000.

3. Harris-Linton, M. Toxocara canis. Animal Diversity Web. 2001. Available at: http://animaldiversity.org/accounts/Toxocara_canis/. Accessed: October 2, 2017.

4. Peregrine AS. Roundworms in Small Animals. The Merck Manual. 2017. Available at:http://www.merckvetmanual.com/?cfile=htm%2Fbc%2F23505.htm. Accessed:October 2, 2017.

5. Centers for Disease Control and Prevention (DPDx). Toxocariasis. Available at:https://www.cdc.gov/dpdx/toxocariasis/index.html. Accessed: October 2, 2017.

6. Hermann N, Glickman LT, Schantz PM, Weston MG, Domanski LM. Seroprevalenceof zoonotic toxocariasis in the United States: 1971-1973. Am J Epidemiol.1985;122(5):890-6.

7. Jones JL, Kruszon-Moran D, Won K, Wilson M, Schantz PM. Toxoplasma gondii andToxocara spp. co-infection. Am J Trop Med Hyg. 2008;78(1):35-9.

8. Won KY, Kruszon-Moran D, Schantz PM, Jones JL. National seroprevalence and riskfactors for Zoonotic Toxocara spp. infection. Am J Trop Med Hyg. 2008;79: 552–557.

9. NHS Choices. Toxocariasis. Available at: https://www.nhs.uk/conditions/Toxocariasis/. Accessed: October 2, 2017.

10. Kayes SG.Human toxocariasis and the visceral larva migrans syndrome: correlativeimmunopathology. Chem Immunol. 1997;66:99-124.

11. Ruiz de Ybanez MR, Garijo M, Govena M, Alfonso FD. Improved methods forrecovering eggs of Toxocara canis from soil. J Helminthol. 2000;74(4):349-53.

• The number of eggs per sample varied greatly

• Some parks were significantly less infected than others

• Some, but not all, parks had similar average numberof Toxocara eggsTable 4. Kruskal-Wallis Test on the Number of

Toxocara Eggs Among Parks

Table 5. Pair-wise Comparison on the Average Rank between Parks using the Dunn Procedure

RESULTS SUMMARY

CONCLUSIONS