J of IMAB. 2018 Jul-Sep;24(3) https://www.journal-imab-bg.org 2177

Original article

CONTAMINATION WITH TOXOCARA SPP. EGGSOF ENVIRONMENTAL SAMPLES OF PUBLICPLACES OF VARNA CITY, BULGARIA

Tatyana Cvetkova1, Kalina Stoyanova1*, Tsonko Paunov2

1) Department of Infectious Diseases, Parasitology and Dermatovenereology,Faculty of Medicine, Medical University - Varna, Bulgaria2) Department of Hygiene and Epidemiology, Faculty of Public Health, MedicalUniversity - Varna, Bulgaria.

Journal of IMAB - Annual Proceeding (Scientific Papers). 2018 Jul-Sep;24(3)Journal of IMABISSN: 1312-773Xhttps://www.journal-imab-bg.org

ABSTRACT:Toxocariasis in humans is an unknown and under-

diagnosed disease with increased risk of distribution de-termined by the large canine and cat populations. Contami-nation of the environment with pets feces containing hel-minth eggs is the key route of transmission toxocariasis,threatening especially the youngest children.

The purpose of this study is preliminary research ofthe degree of pollution of the environment with Toxocaraspp. eggs by examining soil and sand samples from differ-ent public places of Varna, Bulgaria.

Material and methods: In 2018, 40 soil and sandsamples were collected from various locations of Varna city:public park areas, areas for dog-walking, playgrounds, sand-boxes and yards with domestic animals. The samples wereprocessed using modified Romanenko’s method.

Results: Soil analysis showed Toxocara spp. eggs inone sample from a public park area in the central region ofVarna. In another soil sample of a private yard with domes-tic dog typical ova of the Taeniidae family was observed(possibly of E. granulosus). In two other samples, eggsfrom other canine parasites were discovered.

Conclusion: The first research of the environmentalcontamination with helminthic eggs in Northeastern Bul-garia showed Toxocara spp. eggs in one of the central andmost populated area of Varna city. Furthermore, at least 10%of the tested materials were contaminated with canineexcrements that testify for the lack of proper control of do-mestic and stray animals, which represents a real and im-minent danger from zoonotic infection for the public healthin the region.

Keywords: Toxocara, Toxocariasis, Visceral LarvaMigrans, Environmental Exposure, Public Health

INTRODUCTION:Toxocara canis and Toxocara cati are roundworms

from genus Toxocara - one of the most common parasitesof dogs and cats, respectively [1, 2]. Toxocariasis in hu-mans is a result of the migration of the Toxocara larvae indifferent tissues and internal organs of the organism. Theclinical forms include asymptomatic or subclinical course

with mild and unspecific symptoms known as coverttoxocariasis and the clinically significant involvement ofthe lungs, liver and local or systemic allergic reactions –visceral toxocariasis or visceral larva migrans. The involve-ment of the retina and other ocular structures (oculartoxocariasis) may lead to blindness and the migration ofthe larvae through the brain, and spinal cord (neuro-toxocariasis) causes severe neurological complications -meningitis, encephalitis, cerebral vasculitis and epilepsy[1, 3-6].

In Bulgaria, the increased risk for the humans of thiszoonotic infection is determined by the large numbers ofdogs and cats, especially the stray ones [4, 7]. In more than20 years the “stray dogs population” is a widespread andoverwhelming problem of our country that remains unre-solved and continues to exist, unabated with all of its con-sequences [7]. Furthermore, no official data exist regard-ing the population of the domestic or feral cats.

Toxocariasis in humans is caused by occasional in-gestion of Toxocara ova from the environment [4, 6, 8]. Inthe European cities, public places, including parks, play-grounds and sandboxes are the major areas of exposure tothe helminthic eggs, because those areas serve as commonplaces for pets walking and usual habitat of stray dogs andcats [9, 10]. Children playing in these areas are at higherrisk of exposure due to their improper personal hygiene[11]. Recent studies show widespread contamination of ur-ban public places with eggs of Toxocara spp. in differentparts of the world [8, 9, 12, 13]. In Europe the prevalenceof such positive finding varies from 13.0% to 87.0%, inUS – from 4.4 to 20.6%, in Asia – from 6.6% to 63.3% andin Latin America from 17,4 to 60,3% [10, 13–16]. Uncon-trolled and untreated definitive hosts lead to a widespreadcontamination of the environment that, in warm and hu-mid climates, facilitates the survival of Toxocara spp. eggs.[3, 5, 17, 18]

The purpouse of the current study is to perform apreliminary investigation of the environmental contamina-tion with Toxocara spp. eggs of soil and sand samples ofseveral public places of Varna city, Bulgaria.

https://doi.org/10.5272/jimab.2018243.2177

2178 https://www.journal-imab-bg.org J of IMAB. 2018 Jul-Sep;24(3)

MATERIALS AND METHODS:In February-March 2018, 40 environmental samples

(n = 34 soil and n = 6 sand) were taken from various loca-tions of Varna city with an increased risk of infestation withhelminthic eggs (Figure 1). The sampling sites were as-signed and categorized in the following groups: public parkgreen areas (n=11), specified public areas for dogs (n=4),public playgrounds (n=7), separately sandboxes of play-grounds, kindergartens and schools (n=6), as well as pri-vate house yards with dogs, cats and other domestic ani-mals (n=12).

The soil and sand samples were gathered in an ini-tial volume of 200g from the different spots of superficialground layer (1-3 cm) of the assigned places. The sampleswere placed in polyethylene bags with individual labelscontaining information about the place, date and environ-mental conditions. The samples were stored in room tem-perature and analyzed within a week after collection. Thesamples were investigated using modified Romanenko’scentrifugation and flotation technique [4]. After thoroughmixing 25 g of the initial soil/sand samples were measuredand processed by adding an equal quantity of 3% NaOH.After continuous homogenization for 20-30’ min the sam-ples were sieved, centrifuged and then washed several timesdepending on the debris. The final stage of flotation wasperformed with a concentrated solution of NaNO3 in 20 mlplastic vials for 20-30 min, and the superficial layer wasexamined with light microscopy.

RESULTS AND DISCUSSION:Soil analysis showed helminth ova or larvae in 45%

(n=18) of the tested sampling sites, and 55% of the materi-als remained negative (Figure 1). In one (2.5%) of the posi-tive samples from a public park area in the central regionof Varna (Fig.1, sampling site #3) Toxocara spp. eggs werediscovered. Their specific morphology includes sphericalshape, thick dark shell and serrated surface. In a soil sam-ple (2.5%) of a private yard with domestic dog (Fig.1, sam-pling site #9) typical Cestode eggs were observed – small,oval with radially striated thick shell and central onco-sphera. Although the ova of all Taeniidae family are withthe same morphology, we suspect that this is probablyEchinococcus granulosus egg – another canine parasitewith great clinical significance in Bulgaria. A soil sample(2.5%) of an enclosed public area for dog walking (Fig.1,sampling site #15) showed eggs with the characteristiclemon shape of Trichocephalus spp. Since human trichu-riasis in Varna city was not diagnosed as endemic in thelast 10 years [19], we assume that these are eggs of someof the canine wipworms - probably Trichuris vulpis. In oneof the sand samples (2,5%) from a playground of a centralcity, area elongated eggs with thin shell, and severalblastomeres were discovered. Due to their morphologicalidentity, we couldn’t differentiate if this is Ancylostoma orStrongyloides spp. egg but either genus may represent atreat for human health. In 11 soil (27.5%) and two sand(5.0%) samples, a wide variety of nematode larvae were ob-served. They have not been defined by species because theyhave a limited clinical significance for humans and are notrelevant to this study.

Fig. 1. Varna city map with sampling sites and positive findings.★★★★★ - sampling sites with canine parasites, ● - sampling sites with Nematoda larvae.

J of IMAB. 2018 Jul-Sep;24(3) https://www.journal-imab-bg.org 2179

This is the first study researching the environmentalcontamination with helminthic eggs in Northeastern Bul-garia, and the as a pilot enquiry was focused on severalhigh-risk places of Varna city. Even in these small num-bers of samples in our preliminary research, we were ableto detect Toxocara spp. eggs in a public park area of oneof the most populated central part of the city. Furthermore,in the other 3 sampling sites ova of canine parasites werediscovered which shows that at least 10% of the tested ma-terials are contaminated with canine excrements. These re-sults testify for the lack of proper control of domestic andstray animals in the city area and represent a real and im-minent danger from zoonotic infection for the public healthof the human population of the region.

Additional sampling of soil and other environmen-tal materials from small villages and countryside areas ofthe Varna District would be necessary to determine the realthreat of toxocariasis and other helminths because most ofthe studies in the European countries display the evenhigher presence of Toxocara spp. eggs in the rural areas [6,8, 13, 16, 18]. At the same time, the specific regional bio-climatic factors of the Black Sea coast – warm winter andhumid summer, are favorable for the maturation, survivaland longevity of Toxocara eggs in the soil [9, 11]. In asimilar enquiry from Stara Zagora region (South Bul-garia), significantly higher levels of contamination are re-ported - Toxocara eggs in 56,76% of the studied soil andsand samples, probably associated with difference in sam-pling sites, advantageous climate or socio-economic con-ditions [20]. Additional and consecutive research in North-eastern Bulgaria would be essential to reveal the actuallevels of contamination with Toxocara eggs of the envi-ronment and would expose the major determinants respon-

sible for the detected discrepancies in the different partsof our country.

CONCLUSIONS:The ova of all soil transmitted Nematoda (including

Toxocara spp.) and other helminths (incl. E. granulosus)are resistant to the exterior conditions and remain infec-tive in the soil for years. There are no methods for reduc-ing the contamination from the environment, so the onlypractical approach requires prevention of the initial pollu-tion [2, 8]. This can include measures for and even manda-tory removing of the excrements of the companion animalsby the owners; regular anthelmintic treatment of domesticcats and dogs, especially puppies; active improvement ofthe health education of pet owners by the veterinarians;preventing access of cats and dogs to public areas (chil-dren’s playgrounds, schools etc.). Several measures in Varnacity in this direction are already applied by the authoritieslike the establishment of specified enclosed areas for dog-walking, fencing of playgrounds and reduction of sand-boxes. In addition, one of the major control measures ofthe municipalities should include limiting the populationof the stray dogs and feral cats.

Such multidisciplinary and integrated approachwould require collaboration between physicians, veterina-rians, pet owners, health and public authorities to limit thedistribution of toxocariasis, echinococcosis and other zoo-notic helminthiases that present a significant and in the caseof toxocariasis unknown and underdiagnosed threat for thepublic health.

Conflict of Interest:No conflict of interest to declare.

1. Moreira GM, Telmo Pde L,Mendonca M, Moreira AN, McBrideAJ, Scaini CJ, et al. Human toxoca-riasis: current advances in diagnostics,treatment, and interventions. TrendsParasitol. 2014 Sep;30(9):456-64.[PubMed] [CrossRef]

2. Deplazes P, van Knapen F,Schweiger A, Overgaauw PA. Role ofpet dogs and cats in the transmissionof helminthic zoonoses in Europe,with a focus on echinococcosis andtoxocarosis. Vet Parasitol. 2011 Nov;182(1):41–53. [PubMed] [CrossRef]

3. Hotez PJ, Wilkins PP. Toxo-cariasis: America’s Most Common Ne-glected Infection of Poverty and aHelminthiasis of Global Importance?PLoS Negl Trop Dis. 2009 Mar;3(3):e400. [PubMed] [CrossRef]

4. Rajnova I. [Toxocarosis - epide-

miology, clinical forms, diagnosis,treatment.] Sofia: Pensoft; 2008. 78 p.[in Bulgarian]

5. Lee AC, Schantz PM, KazacosKR, Montgomery SP, Bowman DD.Epidemiologic and zoonotic aspects ofascarid infections in dogs and cats.Trends Parasitol. 2010 Apr;26(4):155-61. [PubMed] [CrossRef]

6. Macpherson CN. The epidemiol-ogy and public health importance oftoxocariasis: a zoonosis of global im-portance. Int J Parasitol. 2013 Aug;43(12-13):999-1008. [PubMed][CrossRef]

7. Uzunova K, Nikolova N. [Etiolo-gical aspects of the stray dog’s popu-lation in Bulgaria.] Vet Assem BG.2017; 1-2:41-4. [in Bulgarian]

8. Traversa D, Frangipane diRegalbono A, Di Cesare A, La Torre F,

Drake J, Pietrobelli M. Environmentalcontamination by canine geohel-minths. Parasit Vectors. 2014 Feb13;7:67. [PubMed] [CrossRef]

9. Avcioglu H, Burgu A. Seasonalprevalence of Toxocara ova in soilsamples from public parks in Ankara,Turkey. Vector Borne Zoonotic Dis.2008 Jun;8(3):345-50. [PubMed][CrossRef]

10. B³aszkowska J, GóralskaK, Wójcik A, Kurnatowski P, Szwabe K.Presence of Toxocara spp. eggs in chil-dren’s recreation areas with varyingdegrees of access for animals. AnnAgric Environ Med. 2015;22(1):23-7.[PubMed] [CrossRef]

11. Azam D, Ukpai OM, Said A,Abd-Allah GA, Morgan ER. Tempera-ture and the development and survivalof infective Toxocara canis larvae.

REFERENCES:

2180 https://www.journal-imab-bg.org J of IMAB. 2018 Jul-Sep;24(3)

Address for correspondence:Dr Kalina Stoyanova,Department of Infectious Diseases, Parasitology and Dermatovenereology, Fac-ulty of Medicine, Medical University – Varna.55, Prof. Marin Drinov Str., Varna 9000, BulgariaTelephone: +359 888 325 982E-mail: drkalinasto@gmail.com

Parasitol Res. 2012 Feb;110(2):649-56. [PubMed] [CrossRef]

12. Jarosz W, Mizgajska-Wiktor H,Kirwan P, Konarski J, Rychlicki W,Wawrzyniak G. Developmental age,physical fitness and Toxocara seropre-valence amongst lower-secondary stu-dents living in rural areas contamina-ted with Toxocara eggs. Parasitology.2010 Jan;137(1):53-63. [PubMed][CrossRef]

13. Mizgajska-Wiktor H, Jarosz W,Fogt-Wyrwas R, Drzewiecka A. Distri-bution and dynamics of soil contami-nation with Toxocara canis and Toxo-cara cati eggs in Poland and preven-tion measures proposed after 20 yearsof study. Vet Parasitol. 2017 Jan;234:1-9. [PubMed] [CrossRef]

14. Rubinsky-Elefant G, Hirata CE,Yamamoto JH, Ferreira MU. Humantoxocariasis: diagnosis, worldwideseroprevalences and clinical expres-

sion of the systemic and ocular forms.Ann Trop Med Parasitol. 2010 Jan;104(1):3-23. [PubMed] [CrossRef]

15. Farmer A, Beltran T, Choi YS.Prevalence of Toxocara species infec-tion in the U.S.: Results from the Na-tional Health and Nutrition Examina-tion Survey, 2011-2014. PLoS NeglTrop Dis. 2017 Jul;11(7):e0005818.[PubMed] [CrossRef]

16. Studziñska MB, Demkowska-Kutrzepa M, Borecka A, MeisnerM, Tomczuk K, Roczeñ-Karczmarz M, etal. Variations in the Rate of Infesta-tions of Dogs with Zoonotic Nema-todes and the Contamination of Soilin Different Environments. Int JEnviron Res Public Health. 2017 Jan;14(9).pii:E1003. [PubMed] [CrossRef]

17. Congdon P, Lloyd P. Toxocarainfection in the United States: the rel-evance of poverty, geography and de-

mography as risk factors, and implica-tions for estimating county preva-lence. Int J Public Health. 2011 Feb;56(1):15-24. [PubMed] [CrossRef]

18. Overgaauw PA, van Knapen F.Veterinary and public health aspects ofToxocara spp. Vet Parasitol. 2013 Apr;193(4):398-403. [PubMed] [CrossRef]

19. Stoyanova K. [Epidemiologicalstudies and analysis of risk factors inthe distribution of intestinal parasi-toses with person to person transmis-sion in Varna District] [Dissertation].Sofia: NCIPD. 2017; 197p. [in Bulgar-ian]

20. Georgieva D, Kirkova Z,Ivanov A, Chakarova B, Chakarova P,Jovcheva V, et al. [Induced morbidityin children. Parasitological study ofthe children’s playgrounds of StaraZagora.] Pediatria. 2005; 45(1):23-25[in Bulgarian]

Please cite this article as: Cvetkova T, Stoyanova K, Paunov T. Contamination with Toxocara spp. eggs of environmen-tal samples of public places of Varna city, Bulgaria. J of IMAB. 2018 Jul-Sep;24(3):2177-2180.DOI: https://doi.org/10.5272/jimab.2018243.2177

Received: 21/05/2018; Published online: 14/09/2018