Effects of in vitro culture methods on morphological development and infectivity of Strongyloides venezuelensis filariform larvae

The effects of in vitro culture methods on morphological development and infectivity of Strongyloides venezuelensis filariform larvae ($L_3$) to rats were investigated. A significantly higher body length was observed in $L_3$ from filter paper culture ($597.3{\;}{\pm}{\;}32.2{\;}{\mu\textrm{m}}$) than those in fecal (($509.9{\;}{\pm}{\;}35.0{\;}{\mu\textrm{m}}$) and nutrient broth culture (503.3{\;}{\pm}{\;}31.0{\;}{\mu\textrm{m}}) (P<0.05). Larval infectivity was assessed by exposing rats to 1,000 $L_3$ from each culture and worms were recovered from the lungs and small intestines. Recovery rate of these worms did not show any significant difference. A significantly greater body length of adults was recorded in those corresponding to the $L_3$ harvested from filter paper (2,777.5{\;}{\pm}{\;}204.4{\;}{\mu\textrm{m}}$) and nutrient broth culture (($2.732.5{\;}{\pm}{\;}169.8{\;}{\mu\textrm{m}}$) than those corresponding to the $L_3$ obtained from fecal culture (($2.600.5{\;}{\pm}{\;}172.4{\;}{\mu\textrm{m}}$) (P<0.05). Although worm fecundity and EPG counts differed among culture methods but worm burdens and course of infection did not. These findings suggest that the methods of cultures have a significant effect on the morphological development of the larvae to the $L_3$ stage, but do not influence the infectivity to rats.