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Published Date: 2008-11-07 16:00:35
Subject: PRO/AH/EDR> Salmonellosis Schwarzengrund, human, dog food - USA (02)
Archive Number: 20081107.3502

SALMONELLOSIS SCHWARZENGRUND, HUMAN, DOG FOOD - USA (02)
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Date: Fri 7 Nov 2008
Source: CDC. MMWR Morb Mortal Wkly Rep 2008; 57(44); 1200-2 [edited]
<http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5744a2.htm>

On 16 May 2008, CDC [US Centers for Disease Control and Prevention]
reported on a 2006-2007 multistate outbreak of infection with _Salmonella
enterica_ serotype Schwarzengrund that was associated with dry dog food
(1). At the time of that report, a total of 70 cases had been reported from
19 states, with the last case identified on 1 Oct 2007. Subsequently, an
additional case was identified on 29 Dec 2007.

Epidemiologic and environmental investigations have suggested the source of
the outbreak was dry pet food produced by one manufacturer, Mars Petcare
US. This report updates the previous CDC report, provides additional
epidemiologic findings, and describes additional actions taken by public
health agencies and the manufacturer.

In 2008, 8 more cases have been reported, bringing the total number of
cases in the outbreak to 79. On 12 Sep 2008, the company announced a
nationwide voluntary recall of all dry dog and cat food products produced
during a 5-month period at one Pennsylvania plant. [The list of recalled
products is available at <http://petcare.mars.com/othernewsreleases.html>.
- Mod.LL] Dry pet food has a 1 year shelf life. Contaminated products
identified in recalls might still be in the homes of purchasers and could
cause illness. Persons who have these products should not use them to feed
their pets but should discard them or return them to the store.

During 2006-2007, CDC, the Food and Drug Administration (FDA), and multiple
state health departments investigated reports to PulseNet (the national
molecular subtyping network for foodborne disease surveillance) of persons
infected with a strain of _S._ Schwarzengrund with an indistinguishable
pulsed-field gel electrophoresis (PFGE) pattern (XbaI pattern JM6X01.0015).
A case was defined as a laboratory-confirmed infection with the outbreak
strain of _S._ Schwarzengrund in a person residing in the USA who either
had symptoms beginning on or after 1 Jan 2006, or (if the symptom onset
date was unknown) had _S._ Schwarzengrund isolated from a specimen on or
after 1 Jan 2006.

Investigators initially identified 70 cases, mostly in children. As a
result of these findings, on 21 Aug 2007, Mars Petcare US (referred to as
manufacturer A in the 16 May 2008 report) announced voluntary recalls of
selected sized bags of 2 brands of dry dog food, both manufactured by the
company at its plant in Everson, Pennsylvania. The recall was based on
microbiologic testing by FDA, which found unopened bags of the 2 brands
contaminated with the outbreak strain. Other brands of dry dog and cat food
produced at the same facility were not included in that recall. The
Everson, Pennsylvania, facility ceased operations during July-November 2007
to enable cleaning, disinfection, and renovation, and resumed normal
operations in mid-November 2007.

Despite the 2007 recall, the outbreak strain of _S._ Schwarzengrund was
isolated from 8 more ill persons during January-October 2008 (Figure 1 [for
figures, see source URL - Mod.LL]), bringing the total number of cases to
79 in 21 states (Figure 2). The ill persons were residents of Pennsylvania
(3), Georgia (2), New York (2), and Texas (1). The last reported specimen
collection date was 18 Sep 2008. The only connection between the ill
persons was infection with the outbreak strain; they shared no household or
family contacts.

Among the 8 ill persons, 5 were female. Among the 7 whose age was
available, the median age was 8 months (range: 4 months-39 years); 6
persons were aged less than 2 years. Of 5 ill persons for whom clinical
information was available, all had visited a health-care professional, 2
had bloody diarrhea (no information on symptoms was available for the other
3), and 1 had been hospitalized. No deaths were reported. Of 6 households
with pet ownership known, all 6 had pets (that is,, dogs, cats, or both),
but no illness was reported in any pet. Pets in 3 households were being fed
a brand of dry pet food known to be produced at the Everson plant.
Investigators collected 7 dog stool specimens and 2 samples of dry dog food
from the homes of 2 Pennsylvania patients. None of the stool specimens or
dog food samples tested positive for _Salmonella_. Bag lot numbers and
"best by" dates could not be examined in these households because the dog
food had been poured into plastic containers and the bags discarded.
Consequently, investigators could not be certain that the dog food from the
2 households had been produced at the Everson plant, and, if so, whether
the dog food had been produced after the plant was reopened in November
2007 or earlier.

After additional outbreak-linked illnesses were identified in 2008, FDA
conducted another investigation. In August 2008, FDA found the outbreak
strain of _S._ Schwarzengrund in multiple brands of finished product at the
plant, prompting another recall of products by Mars Petcare US. On 12 Sep
2008, the company announced a nationwide voluntary recall of all dry dog
and cat food products produced at the Everson plant from 18 Feb 2008 to 29
Jul 2008, when production again was suspended at the plant. In addition,
Mars Petcare US has taken steps to ensure that recalled products are no
longer on store shelves. On 1 Oct 2008, the company announced that the
Everson plant would be closed permanently. The FDA investigation is continuing.

[Reported by: Deasy M, Moll M, Urdaneta V, et al]

Editorial note
--------------
This outbreak of human _Salmonella_ Schwarzengrund infections has continued
over a 3 year period, likely because of continued contamination in the
Everson, PA, pet food production facility. _S._ Schwarzengrund is a rare
serotype of _Salmonella_. Although the outbreak PFGE pattern is the most
common _S._ Schwarzengrund PFGE pattern in the PulseNet database, isolates
with that pattern made up only 20 (4 per cent) of the 498 _S._
Schwarzengrund isolates from humans submitted to PulseNet during 1999-2005,
suggesting that the illnesses described in this report resulted from a
common source.

Considering the wide distribution of these products and the relatively
small number of cases, the attack rate for this outbreak appears to be low.
However, only an estimated 3 per cent of all _Salmonella_ infections in the
USA are laboratory confirmed and reported to surveillance systems (2). A
low attack rate supports the hypothesis that infection might have resulted
from practices in a limited number of households that brought humans into
contact with the contaminated pet food and led to amplification of the
organisms (such as, cross-contamination in the kitchens or irregular
cleaning of pet food bowls that might promote bacteria growth). In
addition, the strain might primarily affect persons (such as young
children) who are more susceptible to lower infective doses.

This outbreak is the 1st documented outbreak to associate human
salmonellosis with contaminated dry dog food and to trace human illness to
a contaminated pet food plant. The original source of contamination and
mechanisms for continued contamination in the Everson plant over a 3 year
period are unknown. The absence of cases during January-March 2008 suggests
that cleaning and disinfection of the plant might have had some effect. FDA
is working with Mars Petcare US to better understand this problem.

Since 2006, at least 13 recall announcements involving 135 pet products
(such as, dry dog food and cat food, pet treats, raw diets, and pet
supplements) have been issued because of _Salmonella_ contamination. These
recalls have resulted from contamination with multiple serotypes of
_Salmonella_ and have been associated with multiple pet food manufacturing
plants in the USA. Pet products typically are recalled after product
testing indicates contamination with _Salmonella_. To date, no human
illness has been associated with these other pet food recalls.

Although the last reported case in this outbreak was tested on 18 Sep 2008,
additional cases might occur. The September 2008 recall involved
approximately 23 109 tons [more than 4.6 million pounds - Mod.LL] of dry
pet foods, representing 105 brands. However, dry pet food has a 1 year
shelf life, and contaminated product might still be in the homes of
purchasers and could produce illness.

State and local health departments that identify ill persons with the
outbreak strain should query ill persons or their caregivers to find out
about pet-related exposures, including brands of dry pet food used in the
home. When possible, pet stool specimens and samples of dry pet food should
be collected and submitted for laboratory testing. Hypothesis-generating
interviews for enteric infections should routinely include questions on
contact with pets and other animals, pet food, pet treats, and pet supplements.

Consumers and health departments should be aware that all dry pet food, pet
treats (3), and pet supplements (4) might be contaminated with pathogens
such as _Salmonella_, and consumers should use precautions with all brands
of dry pet food, treats, and supplements. In contrast, canned pet food is
unlikely to be contaminated with such pathogens because the manufacturing
process should eliminate bacterial contamination. To prevent _Salmonella_
infections, persons should wash their hands for at least 20 seconds with
warm water and soap immediately after handling dry pet foods, pet treats,
and pet supplements, and especially before preparing and eating food for
humans. Infants should be kept away from pet feeding areas. Children aged
less than 5 years should not be allowed to touch or eat dry pet food,
treats, or supplements.

In addition to transmission of _Salmonella_ from contact with dry pet food,
humans can acquire _Salmonella_ infection from contact with the feces of
animals that acquired _Salmonella_ infection from contaminated dry pet food
or other sources. Effective hand washing after handling pets and animal
feces will prevent such infections. Persons who suspect that contact with
dry pet food or pets has caused illness should consult their health-care
providers. Additional information on the transmission of _Salmonella_ from
pets to humans is available at
<http://www.cdc.gov/healthypets/diseases/salmonellosis.htm>.

References
----------
1. CDC. Multistate outbreak of human _Salmonella_ infections caused by
contaminated dry dog food - United States, 2006-2007. MMWR 2008; 57: 521-4.
Available at <http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5719a4.htm>
2. Voetsch AC, Van Gilder TJ, Angulo FJ, et al. FoodNet estimate of the
burden of illness caused by nontyphoidal _Salmonella_ infections in the
United States. Clin Infect Dis 2004; 38: S127-S34. Available at
<http://cdc.gov/enterics/publications/280-voetscha1.pdf>
3. CDC. Human salmonellosis associated with animal-derived pet
treats---United States and Canada, 2005. MMWR 2006; 55(25): 702-5.
Available at <http://www.cdc.gov/mmwR/preview/mmwrhtml/mm5525a3.htm>
4. Food and Drug Administration. The Hartz Mountain Corporation recalls
vitamin care for cats because of possible health risk. Rockville, MD: Food
and Drug Administration; 2007. Available at
<http://www.fda.gov/oc/po/firmrecalls/hartz10_07.html>

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[This is the CDC report of an intermittent outbreak of _S._ Schwarzengrund
occurring over 3 years and eventually resulting in the closure of the plant
producing the implicated pet food. - Mod.LL]

See Also