Toxocara canis is a zoonotic helminth parasite of dogs and is the causative agent of ocular and visceral larva migrans (VLM) in humans. Clinical signs of infection are often absent or nonspecific, so diagnosis is made by serologic assays, such as the indirect enzyme-linked immunosorbent assay. This highly specific assay identifies the presence of antibodies to excretory-secretory larval antigens (ESLAs). Obtaining ESLAs requires collection of feces from infected animals, careful dissection of parasite uteri, and arduous purification of parasite larvae. This paper reports marked improvements in the standard larval collection protocol, the De Savigni method. Major changes to the procedure include harvesting both the anterior and posterior portions of uteri and using a metal mesh sieve instead of centrifugation to purify samples. Following these modifications, egg contamination in the samples was reduced, and larval yield increased 5-fold. In addition, the time needed to complete the protocol decreased significantly, from 13 to 4 hours.
COMMENTARY: The modified larval purification protocol described in this report has far-reaching benefits for researchers who need Toxocara antigen. In addition to diagnostic assays, ESLAs are used for studies on the immunomodulatory effects of Toxocara larvae. This new protocol may also be useful to researchers studying the biology of roundworm larvae or the epidemiology of VLM. Benefits to scientists include greatly reduced procedure time and limited need to maintain infected animals, saving precious space and resources in animal research facilities.
An improved method to obtain antigen-excreting Toxocara canis larvae. Alcântara-Neves NM, dos Santos AB, Mendonça LR, et al. PARASITOL 118:349-351, 2008.