- Author: Emily C. Dooley, UC Davis
E. coli and Salmonella are rare in wild birds, Campylobacter more common
Concerns over foodborne risk from birds may not be as severe as once thought by produce farmers, according to research from the University of California, Davis, that found low instances of E. coli and Salmonella prevalence.
While the research found that the risk is often low, it varies depending on species. Birds like starlings that flock in large numbers and forage on the ground near cattle are more likely to spread pathogenic bacteria to crops like lettuce, spinach and broccoli, according to a study of food safety risk and bird pathogens from the University of California Davis. In contrast, insect-eating species were less likely to carry pathogens.
The findings, published in the journal Ecological Applications, suggest that current practice of removing bird habitats around produce growers' farms over concerns the animals could bring foodborne pathogens into their fields may not solve the problem.
“Farmers are increasingly concerned that birds may be spreading foodborne diseases to their crops,” said Daniel Karp, the senior author on the study and an assistant professor in the UC Davis Department of Wildlife, Fish and Conservation Biology. “Yet not all bird species are equally risky.”
Only one foodborne disease outbreak in produce has been conclusively traced to birds: a Campylobacter outbreak in peas from Alaska. While the bacteria can cause diarrhea and other foodborne illness in humans, it's less of a concern to growers than E. coli and Salmonella, which have been responsible for multiple outbreaks across the nation.
In this study, researchers compiled more than 11,000 bacteria tests of wild bird feces and found that Campylobacter was detected in 8 percent of samples. But pathogenic E. Coli and Salmonella were only found in very rare cases (less than 0.5%).
In addition to the bacteria tests, researchers conducted roughly 1,500 bird surveys across 350 fresh produce fields in Western states and collected more than 1,200 fecal samples from fields. They then modeled the prevalence of pathogens in feces, interactions with crops, and the likelihood of different bird species to defecate on crops to determine risk.
Insect-eating birds pose lower risk
Based on the data, insect-eating birds, such as swallows, present a lower risk, while birds that flock near livestock, such as blackbirds and starlings, are more likely to transmit pathogens.
The data can help the agricultural industry determine risk and take action, such as separating produce crops from cattle lands. They also don't need to treat all birds the same.
“Maybe farmers don't need to be quite as concerned about all types of birds,” Karp said. “Our data suggest that some of the pest-eating birds that can really benefit crop production may not be so risky from a food-safety perspective.”
Removing habitat can backfire
This study and the authors' prior work indicate that removing habitat around farms may actually benefit the species that pose more risk and harm the beneficial, pest-eating ones that are less risky to food safety. This is because many prolific insect-eaters may visit crop fields to eat pests but need nearby natural habitats to survive. In contrast, many of the bird species that most commonly carry foodborne pathogens readily thrive on both cattle farms and produce farms without natural habitat nearby.
Other findings
Insect-eating birds that forage in the tree canopy pose minimal threat because they are less likely to carry foodborne pathogens and come into direct contact with produce. They can also be valuable parts of the ecosystem, particularly if they eat pests that can harm crops. Installing bird boxes could attract the pest-eaters, as well as help with conservation efforts.
“We basically didn't know which birds were problematic,” said lead author Olivia Smith, a postdoctoral researcher at Michigan State University who was at University of Georgia when the paper was written. “I think this is a good step forward for the field.”
Additional co-authoring institutions include James Cook University, UC Berkeley, UC Riverside, University of Kentucky, University of Texas, Virginia Polytechnic Institute and State University, Washington State University, BioEpAr, The Nature Conservancy and Van Andel Institute.
The research was funded by the United States Department of Agriculture and the National Science Foundation.
/h3>/h3>/h3>/h2>- Author: Norma De la Vega
A pesar de que el brote, a principios de este mes, de E-Coli 0145 en las lechugas romanas picadas no afectó a los consumidores de California ni a los minoristas locales, si está impactando a toda la industria. De nuevo, la salubridad de las verduras de hoja verde a la venta, ya cortadas y lavadas, ha vuelto a ocupar los titulares, infundiendo temores entre consumidores y productores.
Los Centros para el Control de Enfermedades han confirmado 23 casos de enfermedad y 7 probables casos más en Nueva York, Michigan, Ohio y Tennessee debido a lechuga contaminada. La investigación que se realiza para determinar el origen apunta al Oeste en Yuma, Arizona, donde la lechuga pudo haber sido cultivada. Pero la fuente de contaminación no ha sido identificada.
La designación del contaminante 0145 ha generado confusión y alarma, ya que durante los últimos 30 años, la mayoría de los brotes de E.coli en Estados Unidos fueron del serotipo 0157:H7. Sin embargo, según Trevor Suslow, especialista de Extensión Cooperativa en UC Davis, la cepa del E. coli 0145 no surgió de la noche a la mañana; esta cepa es reconocida y asociada con alimentos de otros países y, más frecuentemente, con productos animales, no agrícolas.
Suslow y sus colegas estaban muy al tanto de la cepa E. Coli 0145 antes del brote de este mes, incluso la incluyeron en su reciente investigación dirigida al desarrollo de un nuevo método para detectar una amplia variedad de las formas más peligrosas de bacteria E.coli en frutas y verduras y en los entornos donde se cultivan y procesan.
La nueva prueba no ha sido designada para identificar una cepa en particular de E.coli, sino para determinar si una cepa patógena/toxigénica de E.coli - como la 0145- está presente. Si el resultado de la prueba es positivo, se tendrá que efectuar una segunda prueba para especificar el tipo concreto de E.coli.Las cepas patógenas/toxigénicas de E. coli son causa de tremenda preocupación para la industria de frutas y verduras frescas. El E.coli “genérico” se encuentra en los intestinos de la mayoría de los mamíferos; usualmente es inofensivo y puede incluso ser benéfico. Sin embargo, cuando las cepas patógenas/toxigénicas de E. coli es ingerido por los humanos puede causar diarrea con sangrado, particularmente entre gente muy joven o de edad avanzada, y puede conducir a insuficiencia renal e incluso la muerte.
Suslow dijo que la nueva prueba, conocida como “total pathogenic E.coli” (E.coli patogéno completo), o TPEC por sus siglas en inglés, fue probada en una variedad de muestras: agua para irrigación, el suelo donde se colocan alimentos para engorda, abono, composta, suelo y productos frutas y verduras.
“Con todos esos materiales, tuvimos muy buenos resultados, pero especialmente con el agua y las frutas y verduras“, dijo Suslow.
La investigación se presentará en el Centro para la Producción Salubre de Frutas y Verduras en UC Davis (Center for Produce Safety), como parte del Simposio sobre Investigaciones Relacionadas con Frutas y Verduras que se llevará a cabo el 23 de junio y que está abierto al público. El costo de inscripción - $150. - incluye todas las sesiones del simposio, desayuno, almuerzo y una recepción por la noche en los jardines del Instituto Robert Mondavi para la Ciencia de Alimentos y Vino.
Para más información o para registrarse en el simposio, vaya al sitio del Center for Produce Safety, http://ccps.ucdavis.edu.
Preparado por Jeannette E. Warnert
Adaptado al español por Norma De la Vega
- Author: Jeannette E. Warnert
Wildlife is not a primary source of E. coli 0157:H7, according to a press release distributed last week by the California Department of Fish and Game. The release reported preliminary results of ongoing research aimed at understanding the risk of fresh produce contamination by wildlife on the Central Coast. The research was prompted by the deadly and well-publicized 2006 E. coli contamination incident in spinach.
From 2007 through 2008, the research team collected 866 wildlife samples, including 311 black-tailed deer, 184 wild pig, 73 birds, 61 rabbits, 58 tule elk, 52 ground squirrels, 51 coyotes, 24 mice, 19 raccoons, 17 opossums and 16 striped skunks. (No animals were harmed in conducting this research; the samples are scat.) Of the 866 animals sampled, 862 tested negative. The four positive samples included: one wild pig, one coyote and two tule elk.
The study's leader, USDA-Agricultural Research Service microbiologist Robert Mandrell, said scientists are less than halfway through the study. (Mandrell was identified in the news release as team leader of the Produce Microbiology and Safety Research Unit, UC Davis. University of California scientists are working with Fish and Game and ARS on the research.)
"The small number of positive animals suggests the risk for produce contamination by wildlife is probably low, and following good agricultural practices should minimize the public health risk," Mandrell was quoted in the release.
The story also appeared on YubaNet.com.