I was appalled in our previous exchanges that the County would consider
flea-born typhus to be a common disease.  I had hoped that that was just
an isolated instance or misunderstanding.  However, your responses here
demonstrate that you have no real understanding of public health
research methods and analysis.  Your policy regarding feral cats is not
science-based: it is fear-based reliance on old wives’ tales, flawed,
and biased research to justify your extreme prejudice against cats.  As
a public health servant, your public statements do a disservice to the
community you serve: they are irresponsible and just plain wrong.


But more unfortunate is the 
pseudo-science you use to evaluate public health risks and programs. 
You base your judgment of the success or failure of a public health 

intervention on nonexistent or questionable data and on a flawed 
simulation study. You use and cite statistical results inappropriately, 
fail to accurately measure the outcomes you are supposed to be 
monitoring, and you don’t even understand the research done by members 
of your own department.  

Read the complete exchange:

Gail Vangordon wrote:

 Hello Dr. Ackerman,

 This email is in response to questions you raised regarding an article
 in the Sunday LATimes (January 17, 2010) concerning TNR.  I was
 interviewed by Ms. Yoshino by telephone and initiated the interview with
 the statement that all my responses to her questions on free-roaming
 cats and the effects of TNR would be based on those colonies within Los
 Angeles County that we monitor, and that I would not be able to respond
 to general questions regarding the practice of TNR. The most significant
 statement I made during the interview related to our policies regarding
 free-roaming cats and was not included in the article.  In effect, the
 practice of TNR, whether it is effective in reducing the size of
 free-roaming cat colonies, is not a debate we willingly engage.  Our
 concerns lie only in the public health risks related to the accumulation
 of feces and flea infestations that occur in association with colonies
 of free-roaming cats.

 I’ll respond to each of the issues you raised:

 You wrote:  VanGordon is quoted as saying that TNR has been
 "'collectively ineffectual' and that all county-monitored colonies had
 significantly increased in number."  This is news to me.

 For approximately the last 6 years, my Program has routinely monitored
 4 colonies of free-roaming cats that reside on County properties and
 public areas: Rancho Los Amigos Rehabilitation Center (RLARC),
 Harbor-UCLA Medical Center, White Point Beach, and Cabrillo Beach.
 Visits to these sites are scheduled once or twice yearly or more
 frequently if complaints are received.  During visits adult and juvenile
 cats are counted, the presence of fecal material and/or fleas is noted,
 the number and condition of feeding stations are recorded, and
 interviews are conducted with maintenance staff and life guards, if
 present. We have noted the following over this period:

 o         The total number of cats observed increases from year to year
 o         The total number of feeding stations increases from year to
 o         Monitoring of RLARC and Harbor-UCLA has revealed 1 to 3 new
 litters of kittens at each site for the past two years

 o         In almost all cases, fecal removal is infrequent at best, and
 fleas are present from late spring to early fall in areas frequented by
 the cats.

 We attribute the observed increases in monitored colonies to
 ineffective trapping by care takers who are unable to trap all intact
 cats within the colony, or keep pace with newly introduced individuals.

 You wrote:  All of the published studies have shown that feral colonies
 managed by  TNR actually shrink over time unless there is an influx of new cats.
 In the past 2 years, the downturn in the economy has forced many families
 to abandon their cats (and dogs), and those abandoned cats have entered
 existing colonies.  In many cases these former pets are already spayed
 and neutered so that even if the number of animals increases slightly
 due to the influx of former pets, the colonies are not breeding. 

 We do not argue the fact that if all members of an original colony have
 been spayed or neutered, there will be no breeding by these individuals.
  Our concerns relate to the influx of intact individuals and the
 considerable size of the colonies we monitor.  As an example, the most
 recent surveillance conducted at each of the hospital campuses indicated
 a minimum of 100 adult and juvenile cats in residence, although
 maintenance personnel who were interviewed estimated a much higher
 number. Grounds staff were also able to direct my staff to areas of the
 campus where young cats from previous litters could be observed. 

 To successfully reduce colonies of this magnitude, a strict trapping
 regimen must be an integral part of the management process. As
 accurately referenced in the article, mathematical models of feral cat
 the population to decline, assuming there is no immigration. Although
 the cats on the 4 monitored sites receive regular care in the form of
 food and water, we have never observed attempts by care takers to
 systematically conduct a disciplined trapping protocol that would
 effectively offset the effects of intact individuals entering the colony
 or reproduction by intact females. 

 You wrote:  It is irresponsible for a public official to make such a
 sweeping  statement that contradicts the published scientific evidence. If you
 have evidence that TNR isn't working in LA County, you should share it
 with members of the scientific community who are trained to critically
 evaluate it.  I am committed to insuring that County policies - and the
 words and  actions of County staff - are consistent with scientific evidence.

 As prefaced above, although our observations and the statements I
 provided for the article reflect our experience related only to
 monitored colonies, the results of our surveillance accurately reflect
 those data published in numerous peer-reviewed journals. As a matter of
 note, we make it a point to verify the literature we maintain in our
 Program reference library and the data we rely upon are only published
 in peer-reviewed journals. 

 You wrote:  If the numbers have "significantly increased", what does
 that mean?  What is the comparison group?

 There is no comparison group; our intention is not to assess the
 effectiveness of TNR, only to evaluate the conditions associated with
 the presence of the cats.  As an example, during the monitoring period,
 the observed population at RLARC has increased from 70 to 100.
 Statements from care givers and grounds maintenance staff placed the
 population at 120.  Despite efforts by SCA to trap and remove cats in
 anticipation of the demolition of structures on the south campus, our
 counts and population estimates by campus staffs have remained
 relatively unchanged. During the monitoring period we have consistently
 observed excessive accumulations of fecal material and active flea
 infestations during the summer months in areas frequented by the cats.

 You wrote:  What would the numbers be if there were no TNR efforts?
 These are the kind of questions we should be asking when evaluating such
 an intervention.  If TNR isn't working here as it elsewhere than we
 should be trying to understand why it isn't working.

 During the interview I referred Ms. Yoshino to the web site where our
 policies have been posted.  I stated that Public Health can not, and
 will not, engage in the debate as to the effectiveness of TNR as a
 management practice.  Our policies relating to free-roaming cats refer
 specifically to the potential public health risks associated with fecal
 accumulations and the presence of fleas.  Whether TNR can reduce a
 colony over a period of 3 years or 10 years is not at issue. Our stance
 must be clearly stated: without the rigorous and systematic removal of
 all fecal accumulations associated with a colony and the effective
 elimination of fleas both on the cats and in the associated environment,
 any colony, regardless of its size, will continue to present a public
 health risk.

 Thank you for the opportunity to restate our perspective and clarify
 the issues you raised.  Unfortunately, when a 20-minute interview is
 reduced to a single paragraph with two sentences, a great deal of
 information is lost.

 Gail VanGordon, R.E.H.S., MS
 Los Angeles County Dept of Public Health
 Chief, Vector Management Program
 Public Health Entomologist
 5050 Commerce Drive
 Baldwin Park, CA 91706
 Office:  (626) 430-5450
 Fax:      (626) 813-3017

Gail Vangordon , Angelo Bellomo 
Re: TNR programs - LA County Public Health


Thank you, Ms. VanGordon. 

While this information does help me see the problem from your
perspective as a vector control manager, it raises additional questions.

Since you have repeatedly stated that your concern is not the numbers of
cats in the colonies but the amount of fecal material and fleas, I would
like to know how you measure those amounts.  As you know, to evaluate an
intervention requires data.  So I’d like to know what you are measuring
and how those measurements have changed or not since TNR programs were
adopted at the colonies you monitor.  Again, I ask you for the data upon
which you based your conclusion that TNR is “collectively ineffectual.” 
By that I am assuming you mean it is ineffectual in reducing feces and

You continue to exaggerate the public health risks associated with
exposure to the feces of feral cats.  Despite the frequency with which
infected patients have household pets, pets have rarely been implicated
as the source of these infections.  With regard to toxoplasmosis, where
causal analyses have been performed, the leading cause of infection is
eating undercooked meat.  Other cases had been exposed to infected feces
of their own pet cats.  Infection from oocysts in cat feces requires
close contact with infected animals.  The same is true of other
intestinal parasites: for cross-infections to occur close contact is

You assert that your goal is the “removal of all fecal accumulations
associated with a colony.”  This is a ridiculous goal that makes no
sense scientifically in light of the findings of species and genotypes
of Cryptosporidium and Giardia (see early review by Hunter and Thompson,
2005).  Molecular epidemiologic studies of Cryptosporidium and Giardia
transmission by Cacciòa et al. (2005), Thompson et al. (2008), Xiao and
Fayer (2008), Ballweber et al. (2009), and many others conclude that the
public health significance of infections in domestic animals is not as
great as previously thought.  There is considerable genetic diversity
among isolates of the same species of Giardia and Cryptosporidium,
suggesting that these species are in fact species complexes and that
some of these are host-specific.  Dogs and cats are commonly infected
with the C. canis and C. felis while human infections are most often
associated with C. parvum and C. homini.  Similarly, genotyping and
subtyping data suggest that zoonotic transmission is not as prevalent in
the epidemiology of giardiasis.  In fact these researchers, many who
work for the World Health Organization, indicate transmission may be
anthroponotic (humans are the reservoir) rather than zoonotic!

In addition, numerous recent surveillance studies have found the
prevalence of these intestinal parasites in cats is low.  An examination
of fecal samples from 384 cats in 4 northern California shelters found
the overall prevalence of Giardia spp. and Cryptosporidium spp. to be
9.8 and 4.7%, respectively.  In New York State, an examination of fecal
samples from 263 kittens also found the prevalence of these parasites to
be low: Giardia, 7.3% and Cryptosporidium, 3.8%.   Do you have data that
show the prevalence of these parasites among cats in LA County is
significantly higher to justify the requirement that all fecal material
be removed?

Feral cats contribute less than you imagine to environmental fecal
accumulations.  I refer you to a 2006 study by Dabritz et al., which
estimated that pet cats allowed to roam were responsible for 72% of
outdoor fecal mass from cats.  She didn't estimate the fecal mass
attributable to dogs, but dogs only defecate outside.  So the outdoor
fecal mass associated with a particular colony is the result of both
free-roaming and feral cats, as well as dogs and also wildlife.  In
fact, the CDC has attributed dog feces as the leading source of
infections from these intestinal parasites.  What are you doing to
protect the public from exposure to dog feces?  Or bird feces and the
feces of other wildlife, etc?

If people are at greater risk of infection from intestinal parasites in
the feces of feral colonies, you would expect to see a higher incidence
of giardiasis or cryptosporiadiosis infections in the colony
caregivers.  Yet none of the workers I interviewed has ever gotten sick
with these diseases.   From an epidemiologic standpoint, consider the
City of Berkeley which vigorously promotes TNR.  The incidence of these
diseases is the same in Berkeley as it is in Los Angeles: in 2008 there
were 9 cases of giardiasis per 100,000 residents and 10 cases per
100,000 in LA; similarly there was 1 case of cryptosporidiosis per
100,000 Berkeley residents and 1 case per 100,000 residents of Los
Angeles.  Thus the fecal mass associated with feral colonies makes no
difference in the rate of these parasitic infections.

With regard to your concerns about the public health risks associated
with fleas, I must again remind you of our discussions in October.  The
risk of flea-born typhus is extremely low, so low that Dr. Helene
Calvet, the Long Beach Health Officer, is quoted as saying, "This is a
rare disease.... The vast majority of the population is not going to
come in contact with this disease or come down with it."  (The full
article is posted on the FoxLA web site,
Furthermore, the causal analysis of cases of murine typhus in LA County
by Sorvillo et al. (1993) found that pet ownership was the greatest risk
factor (OR=6.9, CI=1.8-25.9, p=0.002) and that 90% of pet cats compared
with only 11.5% of neighborhood cats were seropositive for typhus.  As
you know, seropositivity indicates exposure of animals to fleas infected
with typhus.  The conclusion is that flea-born typhus is a rare disease
and if people get sick they most likely become infected from fleas on
their own cats (or dogs) rather than from cats in the neighborhood.  To
repeatedly call fleas from feral cats a public health risk is contrary
to the evidence from your own department.  The risk of infection is from
fleas on pet cats (and dogs).

You have also stated that, even though you are not concerned with
numbers, you are obtaining counts of the numbers of cats and litters at
each site.  And you are quoted as saying that those numbers have
“significantly increased.”  Statistical tests require either a parallel
comparison group or a before-and-after comparison in the same
population.  Do you mean the numbers have increased since before TNR was
initiated?  Are your statistical analyses comparing current numbers with
the historical numbers of cats before TNR?  What are the historical
numbers that you are using for your before and after comparisons?  How
many litters per year were there in the colonies before TNR?  Again, I
ask you for the data you are using to base your conclusion that the
numbers have significantly increased in the colonies you are
monitoring.   You suggest that up to 3 litters a year in a colony of 100
cats is proof that TNR isn’t working.  How many litters do you think
there would be if none of the cats were sterilized?  Just one intact
female cat can produce 3 litters or more a year and more than 600,000
offspring during her lifetime.  Without accurate counts of cats and
litters and a comparison group, either historical or parallel, it is
impossible for you to draw any conclusion about the effectiveness of TNR.

For your information and education, the following are appropriate and
accurate data from Harbor that I obtained by interviewing the primary
caregiver.  Caregivers are the only accurate source of this type of data
because they feed the cats at night, when the cats are out, and they get
to know each animal.  Before TNR began in earnest at Harbor there were
at least 100-150 cats, and may have been as high as 300.  The hospital
would trap and remove them every 6 months, and during each 6-month
interval the number of cats and kittens doubled or tripled.  Currently
there are 52 cats at Harbor.  The caregiver feeds them at night and
returns 1 hour later to remove the dishes.  Each year there are 4-6
newcomers who are removed, spayed or neutered, and adopted out.  Many of
the newcomers are intact, and many of these are pregnant females.  Last
year there were 2 litters.  In other recent years there have been 0
litters.  All kittens are removed for adoption and the mothers are
removed, spayed, and put up for adoption.   You mention counting the
number of feeding stations.  There are none at Harbor except for 1 hour
each night.  What does that number tell you about the size of the
colony, number of fleas, or the amount of fecal material?   At Harbor,
the agreement is that Harbor removes the fecal material and controls
fleas in its buildings and the caregiver adds "Program" to the cats’
food once a month to control fleas on the animals.  If and when special
situations arise, the caregiver and the hospital work together.  For you
to state on the record that TNR is “collectively ineffectual” is just
plain wrong and does a disservice to the ongoing and successful
partnership between Harbor and the team of caregivers.

I also interviewed the caregivers at Cabrillo, White Point, and Rancho
Los Amigos where similar successes can be demonstrated.  At Cabrillo
before TNR there were about 40 cats and now there are 20.  There hasn’t
been a litter in 3 years.  Last year there were 2 newcomers, abandoned
cats, who were trapped, neutered, and put up for adoption. 

At White Point there were substantially more than 100 cats when they started TNR
in 1995.  In 2001 the caregivers and other volunteers at their own
expense had the cats’ blood and feces tested and the results were
presented to staff of the Public Health department, who concluded that
the cats posed no health risk to the public. Currently there are 55
cats.  There was 1 litter last year, and all the kittens were removed,
spayed/neutered, and put up for adoption.  Each year they receive about
8 drop-offs, which are all spayed/neutered and if possible put up for
adoption.  The cats are fed daily, and the feces are removed daily.  To
control fleas, the cats are treated with Program twice a year or
regularly with Advantage.  Sick animals are trapped and treated or
euthanized if necessary. 

Historically at Rancho there were 150-200 cats. Many were cats who had escaped from the Downey shelter in 2008.  There are now 70 cats.  There was 1 litter this past year and the kittens were removed for adoption and the mother was trapped, spayed,
and removed.  Several newcomers were similarly trapped, spayed/neutered,
and put up for adoption.  To appropriately monitor these colonies, you
need to interview the caregivers.  They are truly field researchers who
document their work.  Stray Cat Alliance and the other caregivers, all
dedicated volunteers, are dismayed that you continue your obvious
vendetta against the cats with total disregard for the actual data.

Despite the fact that you are not interested in numbers of cats, you
cite estimates provided by simulation models of the number of
sterilizations required for TNR to be successful (in terms of numbers of
cats).  However, simulation studies of the type you mention can never
accurately predict the future of a specific colony.  We would need to
know: 1. what the colony growth rate would be if all animals were
intact; 2. the rate of immigration of intact animals entering the
colonies; and 3. the rate animals are adopted out of colonies.   The
paper you mention is severely flawed because it does not include
adoption rates in its simulations, and yet adoption out of colonies has
been shown to be an important component of successful TNR programs. 
Thus this model overestimates the proportion of animals that must be

I would like to point out the public health benefits of TNR programs. 
By reducing the proportion of intact animals it slows the colony growth
rate and thereby slows the accumulation of feces.  TNR also removes sick
cats from the environment and through vaccination it increases the
proportion of healthy animals so that any risk of disease transmission
to humans is also lowered.  To achieve the goal of smaller (and
healthier) colonies that do shrink overtime along with the fleas and
fecal mass, it seems that a coordinated effort is needed that requires
support for TNR programs and the caretakers.  In addition, the influx of
new cats must be slowed or stopped by encouraging responsible pet
ownership (to discourage animal dumping) and by mandatory spay and
neuter laws.  Most importantly from a public health perspective, pet
owners must be made aware of the need for flea control, proper
sanitation, and good hygiene.

None of us wants large populations of cats living in the streets. 
However, trap and remove has not been found to be effective.  As was
observed at Harbor and elsewhere, intact females will continue to breed
and other animals will move in as long as the environment supports a
certain population size.  As long as more pets are born than can be
adopted, there will always be abandoned animals and there will always be
humanitarians who feed them.  TNR is an important component of the

It is unfortunate that Ms. Yishima chose to include only a small part of
your discussion and not your disclaimer that you are only interested in
the fleas and feces of feral cats.  But more unfortunate is the
intervention on nonexistent or questionable data and on a flawed
simulation study.  You use and cite statistical results inappropriately,
fail to accurately measure the outcomes you are supposed to be
monitoring, and you don’t even understand the research done by members
of your own department.  You may very well have a whole library of
reference material, but if no one knows how to interpret the studies,
what good are they in informing your policies?

I was appalled in our previous exchanges that the County would consider
an isolated instance or misunderstanding.  However, your responses here
demonstrate that you have no real understanding of public health
research methods and analysis.  Your policy regarding feral cats is not
and biased research to justify your extreme prejudice against cats.  As
community you serve: they are irresponsible and just plain wrong.


Deborah Ackerman, M.S., Ph.D.
Adjunct Associate Professor of Epidemiology
UCLA School of Public Health



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