title: Flotation of Toxocara canis Eggs in Commercial Bleach and Effects of Bleach Treatment Times on Larval Development in These Eggs.
abstract: Toxocara canis is a common intestinal nematode of young dogs. Puppies contaminate the environment with large numbers of eggs that can embryonate and become infective in less than a month. Embryonated eggs are infectious for humans and other paratenic hosts. Most T. canis infections in humans are asymptomatic; however, migration of T. canis larvae in the eye and in the central nervous system can result in vision loss, blindness, and even death. The eggs of T. canis are highly resistant to harsh environmental conditions and routinely used chemical disinfectants. The objective of this study was to evaluate the effects of full-strength commercial bleach (5.25% sodium hypochlorite solution) treatment on development of T. canis eggs and to report our serendipitous finding that T. canis eggs in dog feces can float in passive fecal flotation tests using bleach. We also demonstrated that T. canis eggs could be identified using the McMaster's fecal eggs counting test using 100% bleach. Toxocara canis eggs collected from the feces of naturally infected 4-8 wk old puppies were treated with full-strength bleach (5.25% sodium hypochlorite solution) for 15 min, 30 min, 60 min, and 120 min; washed free of bleach smell by centrifugation; and resuspended in 0.1 N sulfuric acid solution to undergo larval development at room temperature for 18 days after exposure to bleach. Motile larvae were observed in T. canis eggs in all groups treated for 15-120 min and eggs continuously exposed to bleach for 18 days. Our results indicate that bleach may not be an appropriate disinfectant for dog kennels, cages, or laboratory utensils and work surfaces. Toxocara canis eggs are resistant to bleach treatment and continue to pose a risk for canine and human infections. Further study is needed to find the most appropriate methods for disinfection and removal of eggs to reduce the risk of transmission of this parasite.
authors.affiliation: Department of Natural Sciences and Mathematics, College of Science, Technology, Engineering and Mathematics, Johnson C. Smith University, Charlotte, North Carolina 28216.
authors.forename: Alexa Rosypal
authors.initials: AR
authors.lastname: von Dohlen
authors.affiliation: Department of Natural Sciences and Mathematics, College of Science, Technology, Engineering and Mathematics, Johnson C. Smith University, Charlotte, North Carolina 28216.
authors.forename: Alice E
authors.initials: AE
authors.lastname: Houk-Miles
authors.affiliation: Department of Natural Sciences and Mathematics, College of Science, Technology, Engineering and Mathematics, Johnson C. Smith University, Charlotte, North Carolina 28216.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Zajac
authors.affiliation: Department of Natural Sciences and Mathematics, College of Science, Technology, Engineering and Mathematics, Johnson C. Smith University, Charlotte, North Carolina 28216.
authors.forename: David S
authors.initials: DS
authors.lastname: Lindsay
mesh_terms: D000818:Animals; D004202:Disinfectants / Q000737:chemistry / Q000494:pharmacology*; D004285:Dogs; D005243:Feces / Q000469:parasitology; D006801:Humans; D007814:Larva / Q000187:drug effects / Q000254:growth & development; D010063:Ovum / Q000187:drug effects / Q000254:growth & development; D016877:Oxidants / Q000737:chemistry / Q000494:pharmacology*; D010270:Parasite Egg Count; D012973:Sodium Hypochlorite / Q000737:chemistry / Q000494:pharmacology*; D013046:Specific Gravity; D013997:Time Factors; D017166:Toxocara canis / Q000187:drug effects / Q000254:growth & development*
chemical_list: D004202:Disinfectants; D016877:Oxidants; D012973:Sodium Hypochlorite