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Flea control - least toxic
options
Indoor use of chemicals is the main
source of non-occupational human exposure to pesticides.
As an ongoing series in Pesticides News, this report aims
to help reduce hazards from the home environment.
 Every summer the Pesticides
Trust [now PAN UK] information line becomes overheated with
calls from concerned pet owners unsure of which
flea control products to use safely on their pets
and in their homes. Parasitic cat and dog fleas (Ctenocephalides
felis/canis) which feed on warm blooded
animals can cause pets to lose hair, scratch and
bite at sensitive areas and cause owners skin
irritation and allergic reactions. The veterinary
medicines industry has put a vast array of
insecticidal products on the market, some of
which still contain organophosphates (OPs), this
article offers an alternative strategy.
Biology
A female flea can lay around 25 eggs a day, which hatch
into larvae in 2-12 days. In optimal conditions larvae
develop into pupae in 8 -24 days but can take up to 200
days. Pupal development takes up to a year in
unfavourable conditions but normally lasts 1-2 weeks.
Ideal conditions are hot, rainy summers. Dryness is fatal
to larvae because they cannot close their spiracles
(breathing holes) to retain moisture(1). Fleas develop
throughout the year and at different rates, so in the
summer season infestations are likely to take hold.
Chemical control
Pesticides used to control fleas include collars, sprays,
spot-ons, shampoos and powders. The main active
ingredients are listed in table 1.
| Table 1. Concerns about flea
treatments used in UK (10, 11) |
|
amitraz (amidine) |
suspected endocrine disruptor |
| carbaryl (CA) |
suspected
endocrine disruptor; human carcinogen; cholinesterase, inhibitor; toxic to bees |
| coumaphos (OP) |
cholinesterase inhibitor; toxic to
fish |
| cythioate (OP) |
cholinesterase inhibitor |
| diazinon (OP) |
suspected endocrine disruptor;
cholinesterase inhibitor; mild eye and skin irritant; toxic to birds; highly toxic to
bees |
| dichlorvos (OP) |
suspected endocrine disruptor;
cholinesterase inhibitor; mild eye and skin irritant;
moderately toxic to birds; toxic to bees and fish |
| fenitrothion (OP) |
suspected endocrine disruptor;
cholinesterase inhibitor; toxic to bees |
| fenthion (OP) |
cholinesterase inhibitor; toxic to
bees |
| fipronil (phenyl pyrazole) |
mild eye irritant |
| flumethrin (SP) |
|
| imidacloprid |
toxic to bees; moderately toxic to
birds |
| iodofenphos (OP) |
cholinesterase inhibitor |
| lufenuron (benzoylurea) |
|
| permethrin (SP) |
suspected endocrine disruptor;
mild skin and eye irritant; skin sensitizer;
toxic to aquatic invertebrates and bees; highly toxic to
fish |
| phenothrin (SP) |
suspected endocrine disruptor;
toxic to fish and bees |
| phosmet (OP) |
cholinesterase inhibitor; mild skin
and eye irritant; embryotoxic; teratogenic; harmful to
birds and animals; toxic to fish and bees |
| piperonyl butoxide (synergist) |
|
| propoxur (CA) |
cholinesterase inhibitor; very toxic
orally; mild eye irritant; foetotoxic; highly toxic to
bees; phytotoxic to some species |
| pyrethrin/pyrethrum (botanical) |
mild skin and eye
irritant; highly toxic to fish; toxic to bees |
| s-methoprene |
formulations can be skin sensitizers |
CA = carbamates; OP = organophosphates; SP =
synthetic pyrethroid.
Inerts used
include: disodium edetate, polyoxy-ethylene lanoline,
sulphamlamide and sodium polyborate on which there is
little information available in the public domain. |
Concern about the harmful effects of
pesticides in flea products were heightened with press
reports of veterans complaining of Gulf War Syndrome
after being exposed to a combination of chemicals,
including OPs during the Gulf War. OPs and carbamates are
nerve poisons which kill by inhibiting the nerve enzyme
cholinesterase thereby disrupting the nervous system. In
February 1997, Droplix, an anti flea treatment which
contains the OP diazinon, was linked with dozens of pet
deaths in Britain (see PN35 pp6-7). Table 2 is a summary
of incidents reported to the Appraisal Panel for Human
Suspected Adverse Reactions to Veterinary Medicines in
the UK(2).
| Table 2. Incidents of suspected
adverse reactions to veterinary products |
|
amitraz in three separate incidents (1992-95)
small children aged 2 & 3 reported to have lost
consciousness after accidentally swallowing a small
amount of shampoo product, in one case with bradycardia
followed by hypothermia and laboured breathing. 6 other
incidents include symptoms of nausea, abdominal pain,
severe eye irritation, flatulent dyspepsia, and headache
and vomiting |
| diazinon three cat owners (1994-1996) reported a
variety of symptoms from diarrhoea, headache, internal
trembling, nervousness, facial burning, nausea and loss
of appetite, stinging eyes and breathlessness |
| dichlorvos & fenitrothion (1991-1995) 11
separate incidents reported, symptoms included: nausea,
diarrhoea aching limbs, dizziness, rashes, flu-like
symptoms, chest pain, respiratory problems, abdominal
pain and vomiting, depression, anxiety and lethargy |
| fenthion symptoms from 9 reported cases (1994-96)
include nausea, sore throat and coughing, breathlessness,
sore eyes, aches and pains, burning and itching, swollen
lips and eyes, and in 2 cases development of lobar
pneumonia days later |
| permethrin after treating dog one owner had an
asthmatic attack (1992), another had an itching and
nettle rash on body and arms (1994) |
| phosmet 8 incidents (1994-1996) symptoms included
burning sensation in mouth, headaches, blurred vision,
dizziness, nausea, difficulty in breathing and burning
sensation in chest |
| propoxur 2 incidents reported (1995), one with
rash on hands and arms, the other with nausea, chest
tightness, shortness of breath and blurred vision |
pyrethrins + piperonyl butoxide pet owner reported
coughing up blood for 3 days after using small animal
spray product (1994). Also used paint stripper the
previous day. 2 cases of itchy rashes (1994)
skin rashes were also reported in incidents concerning pyrethrum
powder (1993), tetrachlorvinphos (1991), piperonyl |
|
butoxide + pyrethrum extract (1991) |
The US Journal of Pesticides Reform 1997(3) cited research papers relating to pesticide
exposure and childhood illness: In Denvor, Colorado,
research has found that home pesticides may be associated
with some childhood cancers(4), one study in Los Angeles found a significant
increased risk of leukaemia in children whose parents
used pesticides in the home and garden(5),
and in Missouri childhood brain
cancer was associated with use of pesticides to control
household pests; flea collars on pets were identified as
a risk factor(6).
The National Office of Animal Health
(NOAH) and the British Pest Control Association (BPCA)
both take the view that a product is safe, if used
according to the label's instructions.
However in 1993 the BPCA asked:
"What insecticide formulation is approved for
amateur use, applied directly to the body, touched by
unprotected hands, provides a source of long-term
insecticide contamination of skin surface including those
of children? Think twice before recommending their
use."(7)
Safer chemical products that contain
insect growth regulators (IGRs) act by preventing
development during one of the four stages of the flea
life cycle. In 1996 Your Cat readers voted Program
the 'Best Flea Treatment' for cats. It is available for
both cats and dogs and the active ingredient, lufenuron
acts by preventing the hatching of any eggs once the flea
has bitten its host. However the US Food and Drugs
Administration observed the following adverse effects in
cats and dogs: vomiting, depression, lethargy, diarrhoea,
loss of appetite and itchy, scratchy skin(8).
Natural flea control
Knowing the size of a flea
population by combing or using flea traps is very useful
in controlling and minimising large flea infestations.
Flea combs are designed to catch the adult flea but also
catch the dried blood and flea faeces that feed larvae.
Any fleas caught should be placed in a bowl of soapy
water. Combing will also tell you if the controls you
have in place are working effectively or need to be
increased in any way. Cleaning the pet's bedding area
regularly and the pet itself can drown fleas. Vacuuming
areas used by pets, including skirting and soft
furnishings on a regular basis is effective at picking up
adult and egg stage fleas.
| Herbal flea collar |
|
| Buy a soft flea collar
(untreated) |
|
| Mix |
|
| 1/2 teaspoon alcohol |
(Essential oils) |
| 1 drop cedar wood oil |
|
| 1 drop lavender |
Mix with the contents of four |
| 1 drop citronella |
garlic capsules |
| 1 drop thyme oil |
|
Soak flea collar
until it has absorbed sufficient mixture
(i.e. is soaked through), then dry |
| The effect
lasts approximately one month |
|
In severe infestations extremities of
temperature are needed such as steam-cleaning, which
kills off larvae as well, although some eggs may still
hatch. Vacuum cleaner bags should be burned or sealed in
an airtight bag and put in the freezer prior to disposal.
Your Cat magazine recently
reviewed the range of natural products available on the
market in response to consumer demand for alternatives to
pesticidal products(9). These include:
- electric flea traps which work by
emitting gentle heat which attracts fleas and
traps them on sticky paper;
- a wide range of cat collars
containing natural ingredients such as
penny-royal, citronella, eucalyptus, cedarwood,
orange and sesame that work for up to 3-4 months;
- other natural sprays, shampoos,
drops, and homeopathic remedies, including diet
and supplements to help boost the immune system.
Comment
The Pesticides Trust is concerned that conditions of use
of domestic veterinary products together with exposure to
garden and household pesticides may be leading to higher
exposure levels than previously expected.
This is particularly worrying for
children whose organs are still at a sensitive stage of
development and are more susceptible to the effects of
pesticide exposure. Their relative exposure to pesticides
is higher than that of adults as they eat, drink and
breathe more per pound of body weight. They can also come
into contact with pesticides via toys, carpets, lawns and
parks - traditional playing areas of children.
-
References
1. Common-Sense Pest Control:
Least-toxic solutions for your home, garden, pets and
community, Olkowski, W., Daar, S. and Olkowski, H.,
Taunton Press, 1991, 255-264.
2. Veterinary Products Committee
Appraisal Panel 1996.
3. Journal of Pesticide Reform,
1997, 17(3):15-22.
4. Home Pesticide Use and
Childhood Cancer: A Case Control Study, Leiss, J.D. and
D.A. Savitz, American Journal of Public Health, 1995,
85(2): 249-252.
5. Childhood Leukaemia and
Parents Occupational and home exposures, Lowengart, R.A.
et. al., Journal of the National Cancer Institute, 1987,
79(1):39-46.
6. Family pesticide use in the
home, garden, orchard, and yard, Davis, R.R., Brownson,
R.C. and Garcia, R., Archives of Environmental
Contamination and Toxicology, 1992, 22:260-266.
7. Your Cat Magazine, January
1997, 76-77.
8. Journal of Pesticide Reform,
1997, 17(3):15-22.
9. Your Cat Magazine, June 1997,
74-77.
10. Henston Small Animal Vade
Mecum. Electronic Version, Business Data Systems Ltd,
1997.
11. Pesticides Trust [now PAN UK] Active
Ingredient Database, 1998.
[This briefing is an extended article that first
appeared in Pesticides News No.40, June 1998, p21]
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