Reduction of risk of human and food animal infection with Toxoplasma gondii is hampered by the lack of epidemiological data documenting the predominant routes of infection (oocyst versus tissue cyst consumption) in horizontally transmitted toxoplasmosis. Existing serological assays can determine previous exposure to the parasite, but not the route of infection. We have used difference gel electrophoresis in combination with tandem mass spectroscopy and Western blot to identify a sporozoite-specific protein (Toxoplasma gondii embryogenesis-related protein, TgERP) which elicited antibody and differentiated oocyst- versus tissue cyst-induced infection in pigs and mice. The recombinant protein was selected from a cDNA library constructed from T. gondii sporozoites, and this protein was used in Western blots and probed with sera from T. gondii infected humans. Serum antibody to TgERP was detected in humans within 6–8 mo of initial oocyst-acquired infection. Of 163 individuals in the acute stage of infection (anti-Toxoplasma IgM detected in sera, or <30 in the IgG avidity test), 103 (63.2%) had detectable antibodies that reacted with TgERP. Of 176 individuals with unknown infection route and in the chronic stage of infection (no anti-Toxoplasma IgM detected in sera, or >30 in the IgG avidity test), antibody to TgERP was detected in 31 (17.6%). None of the 132 uninfected individuals tested had detectable antibody to TgERP. These data suggest that TgERP may be useful in detecting exposure to sporozoites in early Toxoplasma infection and implicates oocysts as the agent of infection.

-The objective of this experiment was to describe the stability of airborne infectious porcine reproductive and respiratory syndrome virus (PRRSV) as a function of temperature and relative humidity. A cloud of infectious PRRSV was aerosolized using 24-jet Collison nebulizer into a dynamic aerosol toroid (DAT) maintained at a specific temperature and relative humidity. The PRRSV cloud within the DAT was sampled repeatedly over time using SKC BioSampler impingers and the total viral RNA (RT-PCR) and concentration of infectious PRRSV (TCID 50 ) in the air samples was determined. As measured by quantitative RT-PCR, PRRSV RNA was stable under the conditions evaluated in this study. Thus, a comparison of viral RNA and Rhodamine B dye, a physical tracer, found no significant difference in the slopes of the lines. Titers of infectious virus were plotted by time and the half-life (T 1/2) of infectious PRRSV was calculated using linear regression analysis. An analysis of the results showed that aerosolized PRRSV was more stable at lower temperatures and/or lower relative humidity, but temperature had a greater effect on the T 1/2 of PRRSV than relative humidity. Based on these results, an equation was derived to predict the T 1/2 of infectious airborne PRRSV for any combination of environmental temperature and relative humidity.aerosol / virus stability / PRRSV / relative humidity / temperature

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Leptospirosis is a zoonosis of global distribution that affects tropical and temperate areas. Under suitable conditions, Leptospira can survive in water and soil and contribute to human and animal infections. The objective of this study was to describe the presence of pathogenic Leptospira in peri-domestic water samples from rural households in southern Chile. Water samples, including puddles, containers, animal troughs, rivers, canals, and drinking water were collected from 236 households and tested for Leptospira using a PCR assay targeting the lipL32 gene. Evidence of Leptospira presence was detected in all sample types; overall, 13.5% (77/570) samples tested positive. A total of 10/22 (45.5%) open containers, 12/83 (14.5%) animal drinking sources, 9/47 (19.1%) human drinking sources, and 36/306 (19.3%) puddles tested positive. Lower income (OR = 4.35, p = 0.003), increased temperature (OR = 1.23, p < 0.001), and presence of dogs (OR = 15.9, p = 0.022) were positively associated with positive puddles. Increased number of rodent signs was associated with positive puddles in the household (OR = 3.22); however, only in the lower income households. There was no association between PCR positive rodents and puddles at the household level. Results revealed the ubiquity of Leptospira in the household environment and highlight the need to develop formal approaches for systematic monitoring.