[Ansteorra] Cats could make you crazy
Hugh & Belinda Niewoehner
BurgBorrendohl at valornet.com
Fri Jul 29 09:23:41 PDT 2011
You site your studies, I'll site mine :-) . Life is dangerous. There
is much more information on the site (including tons of references):
http://www.fabcats.org/cat_group/policy_statements/toxo.html
Other animals, including humans, are intermediate hosts of /T gondii/.
These hosts can become infected but do not produce oocysts. Oocysts
passed in a cat's faeces are not immediately infectious to other animals
and must first go through a process called sporulation which takes
between one and five days, depending on the environmental conditions.
Once sporulated, oocysts are infectious to cats, people and other
intermediate hosts and can survive in the soil or water for prolonged
periods (up to 18 months) even in extreme weather conditions.
Intermediate hosts become infected through ingestion of sporulated
oocysts, and this infection results in formation of tissue cysts
(bradyzoites) in various tissues of the body. Tissue cysts remain in the
host for life and are infectious to cats, people and other intermediate
hosts if eaten. Dogs (and perhaps other animals) can also transport
sporulated (infective) oocysts and spread these to other places if they
eat the oocysts and then pass them in their faeces where they remain
infective.
What are the sources of infection for people?
In most cases, people become infected via one of two routes:
* Ingestion of oocysts from the environment eg, through contact with
soil containing sporulated oocysts. This can also occur indirectly
through eating contaminated fruit or vegetables.
* Ingestion of meat containing tissue cysts. Fresh meat is most
risky since freezing meat for several days will kill most tissue
cysts.
Other routes of infection are less commonly implicated but include:
* Ingestion of sporulated oocysts through contact with contaminated
water
* Ingestion of raw (unpasteurised) goats milk can transmit the organism
* Inhalation of sporulated oocysts on dust particles (extremely rare)
Does contact with a cat increase the risk of infection?
Recent research indicates that contact with cats does not increase the
risk of /T gondii/ infection of people. These studies have shown that:
* It is rare to identify cats shedding oocysts in their faeces.
Thus, a recent survey found that while 24 percent of 206 cats had
antibodies to /T gondii/ indicating prior infection with this
agent, oocysts were not found in the faeces of any of these cats
(Hill et al 2000).
* Veterinary surgeons working with cats are no more likely to be
infected with /T gondii/ than the general population including
people not in contact with cats (Behymer et al 1973, Sengbusch &
Sengbusch 1976, DiGiacomo et al 1990).
* Contact with cats has no influence on the probability of people
having antibodies to /T gondii/ (antibodies develop following
infection) whereas consuming raw meat significantly increases the
risk of acquiring this infection (Flegr et al 1998).
* Stroking a cat will not spread infection from cats to people
* Even when cats are shedding oocysts in their faeces, oocysts
cannot be found on their coat (Dubey 1995).
* Studies performed in dogs have shown that oocysts do not sporulate
on their fur (Lindsay et al 1997) and it is likely that the same
is true in cats.
* Cat ownership does not increase the risk of toxoplasmosis in
people suffering from AIDS (Wallace et al 1993). Although people
with AIDS are generally at an increased risk of clinical disease
relating to /T gondii/ infection, this results from reactivation
of previous infection rather than acquiring new infection from
their cat or other sources.
* The risk of infection from cats is very low except in young
children playing in soil contaminated with sporulated oocysts.
Most people are infected through ingestion of undercooked meat --
especially goat, mutton and pork (Wallace et al 1993).
* It is generally believed that infection cannot be transmitted by a
bite or scratch from an infected cat.
* Studies suggest that previously infected cats needing treatment
with immunosuppressive drugs at standard doses, do not start
shedding oocysts in their faeces (Lappin et al 1992).
* Studies also indicate that cats previously infected with /T
gondii/ do not re-shed oocysts in their faeces if they become
immunosuppressed due to infection with feline immunodeficiency
virus (FIV) or feline leukaemia virus (FeLV) (Lappin 2001).
* Furthermore, cats with FIV or FeLV that are subsequently infected
with /T gondii/ do not appear to shed oocysts for any longer or in
any greater numbers than other cats (Lappin et al 1996, Dubey &
Lappin 1998).
* Newer strains of /T gondii/ have been identified that are highly
infectious with infection being efficiently passed between
intermediate hosts (species other than cats). Consequently, some
scientists think that cats are becoming less important in the
spread of this infection.
How can the risk of transmission of toxoplasma from a cat to its owner
be reduced?
Toxoplasmosis is particularly severe in certain 'high risk' groups of
individuals (see 'What is toxoplasmosis' section). Although the risk of
transmission of infection from a cat to its owner is very low, this can
be reduced further and/or its consequences minimised by adopting the
following recommendations:
1. People in 'high risk' groups should not have contact with the
cat's litter tray. Where possible, only non-pregnant and
immunocompetent people (ie, not those people with diseases or drug
therapy suppressing their immune system) should handle cat litter
trays (following all of the guidelines below).
2. Empty litter trays daily so that oocysts do not have sufficient
time to sporulate (become infective) while in the litter tray.
3. Wear gloves when handling cat litter and wash hands thoroughly
after cleaning the litter tray.
4. Use litter tray liners if possible and periodically clean the
litter tray with detergent and scalding water (which kills
oocysts) eg, fill the litter tray with boiling water and leave for
five to 10 minutes before emptying.
5. Dispose of cat litter safely. For example, seal it in a plastic
bag before putting it with other household waste.
6. Cover children's sandpits when not in use to prevent cats using
them as litter trays.
7. Feed only properly cooked food or commercial cat food to your cat
to avoid infection.
8. Washing hands after contact with a cat (especially before eating)
is a sensible hygiene precaution.
9. If very concerned, ask your vet to check your cat's toxoplasma
titre (antibody test for exposure to /T gondii/):
1. Cats with a positive titre have been infected in the past
and will not be a source of infection in the future as they
have completed their period of oocyst shedding.
2. Cats with a negative titre have not been infected with /T
gondii/ in the past and are likely to shed oocysts in their
faeces for a short time if they become infected in the future.
10. The risk of acquiring infection can be minimised by:
1. Avoiding feeding raw meat to the cat to reduce the risk of
/T gondii/ infection (see point 7 above).
2. Keeping the cat indoors to prevent hunting and access to
intermediate hosts such as moles and mice.
How can the risk of transmission of toxoplasma from other sources be
reduced?
These measures are essential in all 'high risk' groups of people (see
above) and are also sensible routine hygiene precautions:
1. Gloves should be worn when gardening and hands thoroughly washed
after contact with soil which may contain sporulated (infectious)
oocysts.
2. Gloves should be worn when handling food to prevent exposure to
oocysts and tissue cysts. Hands should always be washed thoroughly
afterwards.
3. Fruit and vegetables should be thoroughly washed before eating to
remove any oocysts present on their surface.
4. All food preparation surfaces and utensils should be cleaned with
detergent in warm water before and after use to inactivate any
tissue cysts.
5. Meat should be cooked to a minimum of 58°C for 10 minutes or 61°C
for four minutes to kill the tissue cysts (Dubey et al 1990).
Microwaving is not a safe way to kill tissue cysts as the heating
is uneven. /T gondii /oocysts can remain infectious when stored in
a refrigerator (4°C) for up to 54 months (Dubey 1998).
6. Freezing meat at --12°C to -20°C for three days kills tissue cysts
as does curing or smoking (Dubey 1988, Lunden and Uggla 1992).
7. Gamma irradiated food is free from any risk of infection.
8. If drinking a non-mains water supply, boil or filter before
drinking to remove oocysts.
Why is toxoplasmosis in the news so much at the moment?
Over the past 10 years, much research has centred on the possible
behavioural effects of /T gondii/ on infected people and animals. Some
of these studies have involved psychomotor tests on people, whereas
others have looked at experimental infection of rodents in the
laboratory. The human studies have yielded some interesting results but
these should be interpreted with caution because of the often small
numbers of people studied and their different backgrounds. All of the
studies have compared people who have been exposed to Toxoplasma with
those that have not and have used this as a basis for explaining any
differences between the two groups of people. However, other factors may
well have been responsible for some of the changes. For example, one
study involving 857 Czech military conscripts (Flegr et al 2003)
reported decreased IQ and verbal intelligence in /T gondii/-exposed
individuals whereas a second study found that /T gondii/-exposed
pregnant women were more intelligent (Flegr & Havlicek 1999). These
conflicting results raise the question as to whether Toxoplasma exposure
was responsible for any of the documented behavioural changes.
/T gondii /infection has also been implicated as a cause of slower
reaction times (Havlicek et al 2001) making individuals more at risk of
road traffic accidents (Flegr et al 2002). Both of these studies
involved relatively small numbers of people and results should be
interpreted cautiously. The authors reported that:
* /T gondii/-infected people had slower, more prolonged reaction
times and were more likely to have an accident than uninfected people.
* The risk of having a car accident was highest in those people with
the highest /T gondii/ antibody titre.
Behavioural changes have been documented in mice infected with /T
gondii/ (Hrda et al 2000, Webster 2001) although changes reported in
animals cannot necessarily be extrapolated to humans.
* Infected mice are less active and this is most noticeable when
infection is at its peak (peak of development of tissue cysts
inthe brains of the mice). These behavioural changes may make
affected mice more vulnerable to predation by cats thus passing
the infection on.
* The behavioural changes identified were transient -- disappearing
by week 12 post-infection.
Infected mice have increased levels of dopamine in their brain and
toxoplasmosis has been suggested as a possible cause of schizophrenia in
man (Flegr et al 2003) although evidence that this is the case is
currently lacking.
Conclusions
The risks of acquiring toxoplasmosis from a cat are extremely small and
most people are infected through other routes (such as eating
undercooked meat). Simple everyday hygiene measures can be taken to
reduce the risks of infection (from cats and other sources) making it
safe to own and enjoy owning a cat.
On 7/29/2011 10:40 AM, Angus MacKnochard wrote:
> All of this talk of Animal Hording reminded me of this article.
>
>
> Recent epidemiologic studies indicate that infectious agents may contribute to some cases of schizophrenia. In animals, infections with Toxoplasma gondii can alter behavior and neurotransmitter function. In humans, acute infection with the cat virus "T. gondii" can produce psychotic symptoms similar to those displayed by persons with schizophrenia. Two other studies found that exposure to cats in childhood was a risk factor for the development of schizophrenia.
> Since 1953, a total of 19 studies of T. gondii antibodies in persons with schizophrenia and other severe psychiatric disorders and in controls have been reported; 18 reported a higher percentage of antibodies in the affected persons; in 11 studies the difference was statistically significant.
>
> http://schizophrenia.com/prevention/cats.html
>
>
> Angus MacKnochard Bagadur
> ANDA GDH
> KSCA
> CSS LXVIII,
>
>
> snerta er vald
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