However, contamination by S. typhi
(typhoid fever) and S. paratyphi was found in 4.62% of
dry manure and post-biogas wastewater samples although
these were not normally found in the natural environment
and only forming colonies in human bodies as reported by
Percival et al. (2004) and Berends et al. (1996). While these
kinds of Salmonella are basically found when the environment
is contaminated by human stools via faecal-oral
transmission, the non-typhoidal Salmonella are mainly
found in the natural environment where they usually causes
problems in animals rather than in humans. Davies et
al. (1999) reported that Salmonella can be isolated from
wastewater which is rich in nutrients, but the number of
bacteria can be reduced by wastewater treatment. It can
survive in open-air soils for at least 6 months and for more
than 5 months in wallows (Callaway et al., 2005).