Editing Toxocariasis (section)

===Reservoir===
[[Image:2009-08-16 Puppy at Duke East 1.jpg|thumb|270px|Puppies are the major source of environmental contamination with roundworm eggs]]
Dogs and foxes are the reservoir for ''Toxocara canis'', but puppies and cubs pose the greatest risk of spreading the infection to humans.<ref name="Huh, Sun, Sooung"/><ref name="CDC3"/> Infection in most adult dogs is characterized by encysted second stage larvae.  However, these larvae can become reactivated in pregnant females and cross the placental barrier to infect the pups.  Vertical transmission can also occur through breastmilk.<ref name="Markell_2006"/><ref name="CDC1"/><ref name="CDC4">{{cite web | publisher = Centers for Disease Control and Prevention. | work = DPDx: Parasites and Health. | title = Toxocariasis | date = 19 January 2009 | url = http://www.dpd.cdc.gov/dpdx/HTML/Toxocariasis.htm |access-date=2006-03-07 |url-status=live |archive-url=https://web.archive.org/web/20060513184653/http://www.dpd.cdc.gov/dpdx/HTML/Toxocariasis.htm |archive-date=2006-05-13 }}</ref> Infectious mothers, and puppies under five weeks old, pass eggs in their feces.<ref name="CDC1"/><ref name="CDC4"/> Approximately 50% of puppies and 20% of adult dogs are infected with ''T. canis''.<ref name="Markell_2006"/>

Cats are the reservoir for ''Toxocara cati''.<ref name="Huh, Sun, Sooung"/><ref name="CDC3"/> As with ''T. canis'', encysted second stage larvae in pregnant or lactating cats become reactivated.  However, vertical transmission can only occur through breastfeeding.<ref name="CDC1"/>

Flies can act as mechanical vectors for ''Toxocara'', but most infections occur without a vector.<ref name="Holland_2006"/> Most incidents with Toxocariasis result from prokaryotic expression vectors and their transmission through direct physical contact with feces that results in the contraction of the illness.<ref>{{cite journal | vauthors = Mohamad S, Azmi NC, Noordin R | title = Development and evaluation of a sensitive and specific assay for diagnosis of human toxocariasis by use of three recombinant antigens (TES-26, TES-30USM, and TES-120) | journal = Journal of Clinical Microbiology | volume = 47 | issue = 6 | pages = 1712–7 | date = June 2009 | pmid = 19369434 | pmc = 2691092 | doi = 10.1128/JCM.00001-09 }}</ref>