Greetings, SANETers,
I've been following the raw milk discussion with interest, and did a
little searching on AGRICOLA through the University of Minnesota library
system. I found nothing in a search on the keywords "raw milk" and
"tuberculosis". There were 37 articles from a search on "raw milk" and
"disease*"; for what it's worth, here is a sample of what I found. Caveat:
This is strictly from the abstracts; I have not read the articles.
From the British Medical Journal, vol. 312 (7023) p. 91-94; Desenclos et
al.; Large outbreak of Salmonella enterica serotype paratyphi B infection
caused by a goats' milk cheese, France, 1993: a case finding and
epidemiological study.
The source of the infection was traced to a single processing plant that
made raw goats' milk cheese, and further traced to goats' milk from a
single farm. "This outbreak emphasises the potential health hazards of
widely distributed unpasteurised milk products in France and the need for
their close bacterial monitoring."
From Critical Reviews in Food Science and Nutrition, vol. 34 (1) p.1-30;
Champagne et al.; Psychrotrophs in dairy products: their effects and their
control.
Pathogenic psychrotrophs covered in this article are Listeria
monocytogenes, Yersinia enterocolytica, and Bacillus cereus. "Methods that
can be used to eliminate or control the development of psychrotrophic
bacteria include low or high temperatures, chemicals, gases, the
lactoperoxidase system, lactic acid bacteria, microfiltration,
bactofugation, lactoferrin-related proteins, sanitation, flavors, and
naturally occurring spore germinants."
(My question on the above: if lactic acid bacteria control the pathogens,
can we infer that milk from a healthy cow with a healthy lactobacillus
population would not be a problem? This possibility was brought up in a
previous post, I think by Hugh Lovel)
From British Food Journal: vol. 95 (3) p. 25-31; Lacey, R.W.; Food
poisoning: the rise continues.
"Food-borne infections due to campylobacter, shigella, salmonella and E.
coli 0157 have shown a real increase three to four fold. Argues that
between the mid-1980s and 1992 the reasons are multifactorial and include
unsafe farming methods, possibly a deterioration in water quality, problems
associated with moist food processing and changes in social habitats."
From Journal of Food Protection: vol. 56 (4) p. 306-312; Kirov et al.;
Milk as a potential source of Aeromonas gastrointestinal infection.
"The incidence and properties of Aeromonas species found in milk were
examined to evaluate the potential of milk, as a vehicle for the
transmission of Aeromonas gastroenteritis. Aeromonads are common in raw
milk (60%, 43 of 72 samples, positive). Pasteurization is effective at
removing this contamination. Nevertheless, around 4% (seven of 183)
pasteurized milk samples contained potentially significant strains,
apparently introduced by subsequent handling of the milk. Some of these
strains were indistinguishable from diarrhea-associated strains and were
able to produce exotoxins at 37 degrees C and adhere to epithelial cells."
From Journal of Clinical Microbiology: vol. 29 (5) p.985-989; Wells et
al.; Isolation of Escherichia coli serotype 0157:H7 and other shiga-like
toxin-producing E. coli from dairy cattle.
"We examined 1,266 fecal specimens from healthy cattle during the
investigations of two sporadic cases of hemolytic uremic syndrome
associated with raw milk consumption and an outbread of gastroenteritis and
hemolytic uremic syndrome caused by E.coli 0157:H7. . . .E coli 0157:H7 was
isolated from 16 heifers or calves and 1 adult cow on 22 farms . . . and 1
raw milk sample. . . .This investigation demonstrates that dairy cattle are
a reservoir of E. coli 0157:H7 and other SLTEC."
(My question: Re: the Cornell study on grainfed vs. grassfed--if a dairy
cow is grassfed, is her milk free of E. coli 0157:H7?)
From Food Microbiology: vol. 9 (1) p. 29-36; Krovacek et al.; Prevalence
and characterization of Aeromonas spp. isolated from foods in Uppsala, Sweden.
The researchers found pathogenic Aeromonas spp. in 10 of 24 food samples.
The food types harboring Aeromonas were fish, poultry, beef, and pork. No
Aeromonas were found in vegetables or raw milk samples.
From Food Microbiology: vol. 8 (3) p. 171-182; Zottola and Smith;
Pathogens in cheese.
"The United States has an excellent record of safety; six outbreaks over a
period of 40 years in which more than 100 billion pounds of cheese were
produced. The use of raw milk in the production of cheese, faulty
pasteurization or equipment, post-processing or cross contamination were
contributing factors for reported outbreaks. Effective sanitization
procedures on the farm as well as in the processing plant, the adherence to
good manufacturing practices in all phases of cheesemaking and
distribution, skilled management, education of personnel and good personal
hygiene will assure the cheese industry of a safe and marketable product."
From Journal of Food Protection: vol. 60 (11) p. 1341-1346; Steele et al.;
Survey of Ontario bulk tank raw milk for food-borne pathogens.
Raw (unpasteurized) milk can be a source of food-borne pathogens. Raw milk
consumption results in sporadic disease outbreaks. Pasteurization is
designed to destroy all bacterial pathogens common to raw milk, excluding
spore-forming bacteria and possibly Mycobacterium paratuberculosis, but
some people continue to drink raw milk, believing it to be safe. Current
methods for assessing the bacteriological quality of raw milk, such as
aerobic plate counts, are not usually designed to detect specific
pathogens. The objective of this study was to estimate the proportion of
pick-ups (loads of raw milk from a single farm bulk tank) from Ontario farm
bulk tanks that contained Listeria monocytogenes, Salmonella spp.,
Campylobacter spp., and/or verotoxigenic Escherichia coli (VTEC). Samples
from 1,720 pick-ups of raw milk were tested for the presence of these
pathogens, and 47 L. monocytogenes, three Salmonella spp., eight
Campylobacter spp., and 15 VTEC isolates were detected, representing 2.73,
0.17, 0.47, and 0.87% of milk samples, respectively. Estimates of the
proportion of theoretical tanker truck loads of pooled raw milk
contaminated with pathogens ranged from a low of 0.51% of tankers
containing raw milk from 3 bulk tanks being contaminated with Salmonella
spp. to a high of 34.41% of tankers containing raw milk from 10 bulk tanks
being contaminated with at least one of the pathogens.
(My comment: They aren't sure if pasteurization kills M.
paratuberculosis??? BTW, a previous post mentioned Johne's disease. M.
paratuberculosis is the causative agent for that disease.)
There's lots more, but this post is getting long--here's one last item I
found very interesting:
From Journal of the American Medical Association: vol 257 (1) p. 43-46;
Blaser et al.; The influence of immunity on raw milk--associated
Campylobacter infection.
"A reported outbreak of Campylobacter jejuni infection in 19 of 31 college
students attending a retreat on a farm was found to be due to the first
time consumption of raw milk. Infection did not occur in students who
regularly had consumed raw milk; these students were found to have elevated
levels of antibodies to C. jejuni. A dose relationship was observed for the
degree of illness and the amount of raw milk consumed."
Jane Grimsbo Jewett
Assistant Scientist
Department of Agronomy and Plant Genetics
University of Minnesota
218-845-2832
jewet006@gold.tc.umn.edu
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