Agriculture Reference
In-Depth Information
out by microorganisms (Rynk 1992). Due to the outdoor nature, diversity of waste
materials, contamination levels, and waste handling practices, the outcome of com-
posting varies signifi cantly between farms, and even between compost heaps on the
same farm.
Furthermore, there is growing interest in organic foods because consumers believe
they are healthier than conventionally grown foods. According to a United States
Department of Agriculture (USDA) report, consumption of organic products has
increased by more than 20% annually since 1990, with organic vegetables and fruits
leading the way (Dimitri and Greene 2002). It is expected that the rapid growth of
organic foods, especially fresh produce and fruits, will continue in the future. However,
organic foods may be less safe than conventionally grown produce because organic
farmers largely use animal manure or compost as a fertilizer for their crops (Mukherjee
and others 2004). Because of the increased economic importance of organic produce
and less treatments on these products to inactivate any pathogen that may be present,
it is important for organic growers to use scientifi cally valid methods for treating and
using manure safely.
This chapter focuses on the role of animal manure and compost in produce safety.
Fresh Produce Outbreaks Due to Fecal Contamination of Produce
in the Field
The number of cases of foodborne diseases annually that are associated with the
consumption of raw vegetables and fruits has doubled in the United States during the
past 2 decades prior to 1999 (NACMCF 1999). Recent data revealed that about 13%
of outbreaks with an identifi ed food source from 1990 to 2005 were linked to fresh
produce (DeWaal and Bhuiya 2007). Many varieties of bacteria, viruses, and parasites
have been epidemiologically linked to fresh produce-related outbreaks. These micro-
organisms include various serotypes of
Salmonella
spp.,
E. coli
O157:H7, enterotoxi-
genic
E. coli
,
Vibrio cholera
,
L. monocytogenes
,
Shigella
spp.,
Campylobacter
spp.,
Bacillus cereus
,
Clostridium botulinium
,
Cryptosporidium
spp.,
Cyclospora
spp.,
Hepatitis A, and Norwalk/Norwalklike viruses (FDA 2001; Johnston and others 2006;
NACMCF 1999). The most common produce items associated with outbreaks include
leafy greens-based salads (such as lettuce), potatoes, tomatoes, and sprouts (Buck and
others 2003; Sivapalasingam and others 2004; DeWaal and Bhuiya 2007).
Table 8.1 lists some foodborne disease outbreaks with possible fecal contamination
of fresh produce with human pathogens. For example, an outbreak of
L. monocyto-
genes
in 1981 in Nova Scotia was traced back to the coleslaw that had been made
from cabbage grown in a fi eld fertilized with manure from
Listeria
- infected sheep
(Schlech and others 1983). Most recently, a large
E. coli
O157 outbreak associated
with bagged baby spinach was linked to potential sources such as wild pig feces
present in and around spinach fi elds, nearby irrigation wells and surface waterways
exposed to feces from cattle, and wildlife on one organic ranch in California (CalFERT
2007). However, the exact source of spinach contamination could not be confi rmed
due to the complexity associated with spinach production and processing; this was
also true for many other outbreaks listed in the table.
