Journal of APPLIED BIOMEDICINE
ISSN 1214-0287 (on-line)
ISSN 1214-021X (printed)
Volume 9 (2011), No 3, p 157-161
DOI 10.2478/v10136-009-0035-3
Incidental poisoning of animals by carbamates in the Czech Republic
Ladislav Novotny, Jan Misik, Alena Honzlova, Petr Ondracek, Kamil Kuca, Oldrich Vavra, Vaclav Rachac, Petr Chloupek
Address: Ladislav Novotny, Center of Advanced Studies, Faculty of Military Health Sciences, University of Defence, Trebesska 1575, 500 01 Hradec Kralove, Czech Republic
novotnyl@pmfhk.cz
Received 16th September 2010.
Revised 20th October 2010.
Published online 23rd November 2010.
Full text article (pdf)
Abstract in xml format
Summary
Key words
Introduction
Material and methods
Results
Discussion
Acknowledgement
References
SUMMARY
Illegal poisoning of wildlife and domestic animals is a worldwide issue. The carbamates primarily used as pesticides are often misused for such a purpose. In this study, 181 birds, mammals and baits were analysed over the period 2004-2009 for possible intoxication by carbamates. Intoxication by carbamate carbofuran was diagnosed in 89 cases, and in another 19 cases (nine Wild Boars and 10 Bisons) intoxication with another carbamate-methomyl - was proven. Incidental ingestion of the marten bait was the main cause of intoxication. Although the distribution of carbofuran was prohibited in 2007, no decline in the number of intoxicated animals in the following two years was detected. New cases of intoxication by carbofuran are anticipated in the future until all remaining stock is expended.
KEY WORDS
pesticide poisoning; organophosphorous inhibitors; forensic medicine; acetylcholinesterase
INTRODUCTION
Pesticide poisoning of non target organisms is a
worldwide issue and many cases are described
(Roberston et al. 1992, Hornfeldt and Murphy 1997,
Xavier et al. 2002, Berny and Gaillet 2008).
Carbamate compounds are a very important group of
cholinesterase inhibitors and intoxications caused by
these compounds represent the majority of pesticide
poisoning among animals. According to present
knowledge, carbofurane (2,3-dihydro-2,2-dimethyl-7-
benzofuranylmethylcarbamate) is the most frequently
encountered carbamate as a cause of intoxication. Its
LD50 is ranging from 3-19 mg.kg-1 of body weight in
many animal species (Wang et al. 2007).
Toxicologically, carbamates belong to the group
of acylating (carbamylating) acetylcholinesterase
(AChE) inhibitors which inhibit AChE by
carbamoylation of the serine hydroxyl group in the
enzyme active site. Moreover, this inhibition leads to
the accumulation of acetylcholine in the gap junction
causing hyperstimulation of cholinergic receptors.
"Overdose" with acetylcholine is followed by
overstimulation of the receptors and finally it ends
with a cholinergic crisis followed by muscarine,
nicotine and central nervous signs, i.e. miosis,
hypersecretion of exocrine glands, bradycardia, tonic
and clonic convulsions (O'Malley 1997).
Although carbamate pesticides are less toxic than
organophosphorus pesticides, many cases of animal
poisonings caused by these agents are reported with
increasing frequency (Balcom 1983, Elliot et al. 1996,
Mineau et al. 1999, Wobeser et al. 2004).
In this study, we summarize the results from the
analysis of 89 cases of positively tested birds
(White-tailed Eagle, Golden Eagle, Common
Buzzard, Rough-legged Buzzard, Hooded Crow,
Common Raven, Common Magpie, Grey Partridge)
and mammals (dog, Red Fox, Otter, Wild Boar,
European Polecat, Marten) during the period 2004-09
poisoned by carbofuran and 19 cases of animals
(Wild Boar, Bison) intoxicated with other carbamate
methomyl (methyl N {[(methylamino)carbonyl]
oxy}ethanimidothioate).
MATERIAL AND METHODS
In this retrospective study, 181 cases of suspected
intoxications from January 2004 to December 2009
were analysed. In these 181 cases, 59.0% were tissue
samples (mostly liver), 31.0% were gastric content
and 9.8% were baits (mostly eggs, meat and meat
products). Baits had been laid in forests and parks, or
thrown into private gardens.
White-tailed Eagle, Golden Eagle, Common
Buzzard, Rough-legged Buzzard, Hooded Crow,
Common Raven, Common Magpie, Grey Partridge,
dog, Red Fox, Otter, Wild Boar, European Polecat,
Marten, Bison were among the intoxicated animals.
Necropsy and histopathology were performed on
entire animals (six dogs and three otters) delivered
with a no longer post mortem interval than 24 hours.
The analysis was conducted with the available
chromatographic techniques at the State Veterinary
Institute in Jihlava Czech Republic, using tissue
samples (liver), solid (bait, undefined material) or
liquid samples (gastric content). Samples were
extracted by petroleumether and after evaporation on
the rotary vacuum evaporator and dissolution in
isooctane were analysed by the gas chromatography
method with a nitrogen-phosphorous detector (Lee
and Westcott 1983).
RESULTS
The numbers of examined samples and positive cases
in each year of the study are given in Fig. 1. The
presence of carbofuran could be verified in a total of
89 samples. This means that there were approximately
half (49.2%) of the samples positive out of 181 in
6 years. In 2004 only three samples were examined.
Two of these three samples originally from birds of
prey were positive for carbofuran - a White-tailed
Eagle (Haliaeetus albicilla) and a Rough-legged
Buzzard (Buteo lagopus). In 2005, the percentage of
positive samples was 45.5% (10/25), as in 2007 and
2008 [2007 44.0% (11/25), 2008 46.2% (18/39)]). In
2006, the percentage of positive samples was
somewhat higher [67.9% (36/53)], whereas some
decline was obvious in 2009 [30.8% (12/39)]). Birds
of prey were the most common victims of carbofuran
(Fig. 2) - 22 Buzzards (Buteo sp.) and 8 endangered
Eagles (Haliaeetus sp., Aquila sp.) were illegally
poisoned during the studied time frame. Also dogs
(n=12), Otters (n=10, Lutra lutra) and Corvids [n=10;
Common Raven (Corvus corax)], Common Magpie
(Pica pica)] and Hooded Crow (Corvus cornix)] were
frequently involved. Other species, such as small
carnivores [Marten (Martes sp.), European Polecat
(Mustela putorius)], Stoat (Mustela erminea)] or birds
[Grey Partridge (Perdix perdix)] rarely show signs of
intoxication by carbamates.
In 2007 and 2008, 19 samples were positively
tested for another carbamate - methomyl (methyl
N-{[(methylamino)carbonyl]oxy}ethanimidothioate).
Nine samples were taken from Wild Boars (Sus
scrofa), another ten samples were collected from
Bison (Bison sp.) from a private farm in south
Bohemia. Up to November 2008 a total of a 37 Bison
died supposedly poisoned by methomyl (not all
animals were investigated).
Necropsy revealed dried saliva around the oral
cavity, congestion of the organs, and haemorrhagic
necrosis of the small gut. Histopathology showed
congestion of the kidney, liver and lung, granular
dystrophy of liver and haemorrhagic necrosis of the
small intestine.
Fig. 1. No. of samples analysed in the State Veterinary Institute Jihlava tested for carbofuran (black columns) and number
of positive cases (gray columns).
Fig. 2. Distribution of carbofuran intoxicated samples. Birds of prey were the victims of carbofuran in most cases.
DISCUSSION
Carbamate intoxication is the most common form of
pesticide poisoning of animals in Europe and the US
(Berny 2007, Wang et al. 2007). The most common
route of exposure to pesticides is an ingestion of
poisoned insects, carcasses, or grains intentionally
treated with pesticides for bait (Reece and Handson 1982). Organophosphorous and carbamate pesticides
present also a potential threat for humans mainly
because of their wide use in agriculture. Thousands of
intoxication cases in humans are recorded every year
especially in developing countries (Jayaratnam 1990).
According to many studies, birds of prey are
common victims of carbofuran poisoning (Balcom
1983, Elliot et al. 1996, Wobeser et al. 2004) and this
was confirmed in our study. This could be caused by
secondary poisoning when the raptor consumes a
primary victim with unassimilated remains of
pesticide in its alimentary tract (Dietrich et al. 1995,
Hill 1995, Mineau et al. 1999, Berny 2007), but it is
also possible that some of the baits are directed at
birds of prey.
Compared to the high number of intoxicated birds
we found only sporadic cases of small carnivore
intoxication (except otters), although martens or foxes
are thought to be the main target object of poisoners.
This could be caused by the hidden behaviour of
carnivores, so the real number of intoxications is
expected to be much higher.
Also domesticated animals such as pets, mainly
dogs, and livestock are at risk of being poisoned
(Wang et al. 2007). The consumption of bait could be
accidental during walks outdoors but there are also
some cases of intentional poisoning (Novotny et al.
2003).
Although the use of carbofuran was prohibited by
law in the Czech Republic on 13th December 2008 and
its sale was stopped on 13th December 2007, new
cases of intoxication by carbofuran are still expected
in the future until all stocks are expended.
In organophosphorous and carbamate pesticide
investigation, analysis of the brain and blood
cholinesterase (ChE) activity is widely used as a
diagnostic technique (Worek et al. 1999 Zdarova
Karasova et al. 2009), but gas chromatography was
used in this study. However, diagnostic interpretation
of ChE data always requires knowledge of the normal
value for each species (Blakley and Skelley 1988),
and it may be confounded as well by changes in ChE
levels caused by post mortem decomposition
(Wobeser et al. 2004) and post mortem reactivation of
carbamylated ChE (Hill 1989).
ACKNOWLEDGEMENT
The work was supported by the grant projects
MSM0021620820 and OVUOFVZ200905.
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