An animal model to assess the potential for viral disease transmission from lawns irrigated with wastewater

Abstract

A study was initiated to evaluate the feasibility of using pigs as an animal model to assess the risk of human viral infection from land application of treated wastewater. The model system consisted of three‐week‐old pigs and porcine enterovirus‐serotype 2 (PE2). Pigs were used because the porcine digestive tract and porcine enterovirus infections in pigs are similar to that of man.

An oral challenge inoculation experiment was carried out to examine antibody production in pigs as a result of PE2 virus infection. Piglets free of antibody were intragastrically inoculated with 0, 100 or 100,000 CCID50 (50% cell culture infective dose) of PE2 virus. Serum was monitored to detect antibody to PE2 virus at 3, 7, 10 and 13 days post inoculation. By 13 days post inoculation all pigs challenge inoculated with as little as 100 CCID50 of PE2 virus had seroconverted.

To evaluate the potential for using pigs to assess the risk of viral infection from contact with virus on lawns, piglets free of antibody to PE2 were placed on grass plots seeded with known concentrations of PE2 virus and serologically monitored for production of PE2 antibody. A total of 52 pigs were exposed for two hours to concentrations of 4 x 10² to 4 x 10⁵ CCID₅₀ virus seeded to 0.36 m² grass plots. Incidence rates of infection resulting from a single exposure to virus seeded to grass were calculated for each exposure concentration. The incidence rate of infection among pigs exposed for two hours to 4 x 10⁵ CCID₅₀ PE2 virus seeded on grass was 66.7. The incidence rate dropped off rapidly as the virus concentration seeded onto plots decreased.

Results confirmed that pigs provide a simple means for providing an indication of the risk of viral infection to humans who may come in contact with virus in wastewater applied to lawns. Information gained from studies using pigs for this purpose can be used to examine the dose‐response relationship and establish best practicable management procedures to limit potential health and environmental effects from use of treated wastewater for irrigation.

Key words:

• Wastewater reuse
• enterovirus
• animal model
• porcine
• PE2