Soil Survival of Toxoplasma Oocysts in Kansas and Costa Rica *

Abstract

Toxoplasma oocysts in cat feces were marked with a tracer amount of strontium-85 (85-SR), and were superficially buried simulating the natural disposal of feces by cats. Oocyst infectivity in Costa Rica was followed qualitatively and persisted for 1 year in three shaded sites, two moist, and one relatively dry site. Oocyst infectivity was quantitated in the Kansas deposit over a period of 18 months, including two winters. After initial mixing in soil, the level of infectivity remained fairly stable. Infectivity was recovered, probably from the surface on one Musca, several isopods, and earthworms. These data on persistence of Toxoplasma oocysts in soil support the concept that Toxoplasma infectivity in nature may be increased logarithmically by cats.

Adaptive host manipulation by Toxoplasma gondii: fact or fiction?

“…In the short term, it has been suggested that cats are pivotal to the transmission of T. gondii as they shed millions of oocysts into the environment, providing a large, persistent reservoir of infection for intermediate hosts [19]. However, there are other opportunities for transmission to intermediate hosts, and production of oocysts in a cat may not necessarily result in the greatest dissemination of the parasite.…”

The Life Cycle of Toxoplasma gondii in the Natural Environment

“…Oocyst survival is maximal (> 200 days) for temperatures comprised between -6°C and +20 °C [79]. Above +20°C, dessication of oocysts may occur [41,80,81], but moisture should prevent it [82,83]. Under-6°C, the survival of oocysts is reduced and their capacity to sporulate is lost [79], although one may hypothesize that snow cover may protect them from cold.…”

Long-Term Survival of Toxoplasma gondii Sporulated Oocysts in Seawater

“…Frenkel et al (1975) demonstrated that sporulated T. gondii oocysts in soil could survive for 18 mo. Drinking unfiltered water is a risk factor for obtaining T. gondii infections (Bahia-Oliveira et al, 2003), and outbreaks of waterborne infections have been reported (see Dubey, 2004).…”