Assessing Potential Environmental Contamination by Baylisascaris procyonis Eggs from Infected Raccoons in Southern Texas.

Baylisascaris procyonis is a large ascarid of raccoons (Procyon lotor) and is a zoonotic threat. We documented the potential rate a raccoon population can contaminate their environment with B. procyonis eggs. We estimated the population size of raccoons using a 9 × 7 trapping grid of Havahart traps, identified locations of raccoon scats through systematic searches, and enumerated the distance B. procyonis eggs passively travel from site of origin upon scat decay. During an 8-week capture period, the raccoon population was estimated to be 19.6 ± 1.3 raccoons within the 63-ha study area (1 raccoon/3.2 ha). There were 781 defecation sites, of which 744 (95.3%) were isolated sites and 37 (4.7%) were latrine sites. Fifty-three (6.8%) defecation sites occurred in areas associated with human structures (commensal zone). Of the noncommensal sites, 9 (1.2%) and 719 (98.8%) sites were identified as latrine sites and isolated scats, respectively. More latrine sites were located within the commensal zone (p < 0.0001, [Formula: see text]) than proportionately available space. Twenty-five raccoon scats containing B. procyonis eggs were allowed to decay on level bare soil by way of simulated rain events, 13 were allowed to desiccate naturally in the environment, and 12 were allowed to desiccate and, subsequently, experience a simulated 1 cm rain event; eggs were found 49 ± 6, 28 ± 8, and 68 ± 8 cm from the initial scat location, respectively. We calculated that a single B. procyonis-infected raccoon could contaminate 0.03 ± 0.01 ha/year with B. procyonis eggs. Our findings indicate that B. procyonis represents a substantial risk to humans in areas where infected raccoons and humans co-occur.

Environmental Temperatures in Southern Texas, USA: Implications for Survival of Baylisascaris procyonis Eggs.

Baylisascaris procyonis is an intestinal nematode of raccoons ( Procyon lotor ). Within intermediate hosts, larvae can cause visceral, ocular, and neural migrans. Humans, especially children, have become infected after ingestion of larvated eggs at raccoon latrines. Eggs of B. procyonis have a thermal death point of 62 C. During 2012, we assessed the likelihood of thermal lethality on B. procyonis eggs in southern Texas. We recorded temperature every 30 min with data loggers placed on the ground in full sun and in the shade, buried 5 cm underground and the ground surface exposed to full sun or in shade, in attics with and without exhaust fans, in woodpiles, in sheds, in tree crevices, and in cars parked in the sun. Such locations represented common raccoon latrine sites or locations where B. procyonis eggs could be found. In addition, data loggers placed about 135 cm above the ground in full sun and in shade were used as controls to acquire ambient temperature. The hottest month was August (maximum 44 C), with 15 d that exceeded 38 C. However, only the car reached the lethal temperature limit, and only for 1 h. Southern Texas has one of the warmest climates in the contiguous US; however, it is unlikely that the southern Texas climate is hot enough to kill B. procyonis eggs.

Permeability and Viability of Baylisascaris procyonis Eggs in Southern Texas Soils.

Baylisascaris procyonis is a nematode whose definitive host is the raccoon ( Procyon lotor ). Adult parasites are not particularly pathogenic to raccoons; however, larvae in intermediate hosts can cause visceral, ocular, and neural larva migrans. Humans serve as dead-end hosts, and pathological responses are similar to those found in infected intermediate hosts. Infected raccoons expose intermediate hosts through their feces, which can contain millions of B. procyonis eggs. Our objective was to determine how the quantity and viability of B. procyonis eggs in soil changed over time within different soil texture, moisture, and sun exposure. To examine egg survival and movement through soil we placed 100 B. procyonis eggs on 100 squares in 48 boxes representing a full factorial treatment of soil texture, moisture, and sun level. We monitored egg percolation and survival for 2 yr, removing (at 0, 1, 3, 6, 12, 18, and 24 mo) 5 squares from each box and counting the number of viable eggs at each depth in the soil column. Dry soils were mainly impermeable; even after 2 yr, >60% of B. procyonis eggs remained on the surface of all soil textures. Wet soils were more permeable than dry soils, but even in wet sandy soils where the greatest egg movement occurred, it required 1 yr before 60% of eggs transitioned from the soil surface to the next soil depth. For all soil textures, moistures, sun exposures, and depths, >92% of B. procyonis eggs remained viable after 2 yr in the southern Texas environment. Therefore, high exposure risk exists for potential hosts because B. procyonis eggs remain viable on or near the soil surface for at least 2 yr.