could give a dependable evaluation and interpretation of exposure of wild birds to anticholinesterase insecticides (Fairbrother & Bennett, 1988; Hooper, 1988; Cairns et al., 1991; Fossi et al., 1992; Vodela & Dalvi, 1995; McInnes et al., 1996; Clegg & van Gemert, 1999; Parson et al., 2000; Iko et al., 2003; Fildes et al., 2009). The variations in the plasma and whole brain cho- linesterase activities across the three bird species of the present study (Table 1) could be attributed to normal physiological differences found in the birds (Hill & Murray, 1987; Fairbrother & Bennett, 1988; Hooper, 1988; Fossi et al., 1996; Wilson et al., 1998; Wilson, 1999; Alias & Mohammad, 2005). Such differences could form the basis of differential toxicity of organophosphates and carbamates in wild birds (Fairbrother & Bennet, 1988; Hooper, 1988; Wilson et al., 1998; Wilson, 1999). This notion supports the variations in the extent of in vitro inhibition of plasma and brain cholinesterase activities by organophosphate and carbamate insecticides (Table 2). The technique of in vitro cholinesterase inhibition by organophosphate and carbamate insecticides can be used to assess the potential toxicity of anticholinesterase chemicals (Iyaniwura, 1990; Khan et al., 1990; Karanth & Pope, 2003; Mohammad et al., 2006, 2007a,b). Organophosphate and carbamate insecticides in the avian species as well as in mammals primarily inhibit nervous system cholinesterases with subsequent develop- ment of nicotinic, muscarinic and central nervous tox- icities (Anonymous, 1986a,b; Clegg & van Gemert, 1999; Wilson, 1999; 2005). However, many factors might affect the degree of cholinesterase inhibition in birds. These include the type of the insecticides, exposure dose, route and duration of exposure, species involved, toxicokinet- ics of the insecticide, seasonal variation, etc. (Osweiler et al., 1985; Anonymous, 1986a,b; Hill & Murray, 1987; Osweiler, 1996; Wilson, 1999; Blakely & Yole, 2002; Roy et al., 2005; Wilson, 2005). The in vitro inhibition of plasma and whole brain cholinesterase activities by the organophosphate insecticides dichlorvos, malathion, monocrotophos and by the carbamate insecticide car- baryl in the three bird species are in agreement with the reported anticholinesterase effects of these insecticides in various animal species (Anonymous, 1986a,b; Karanth & Pope, 2003; Long et al., 2003; Wilson, 2005; Al-Badrany & Mohammad, 2007; Mohammad et al., 2007a,b). In vitro cholinesterase inhibition is also a useful technique for detecting the potential anticholinesterase activity of chemicals (Iyaniwura, 1990; Khan et al., 1990; Karanth & Pope, 2003; Mohammad et al., 2006, 2007a,b). In conclusion, the present study reports the values of plasma and whole brain cholinesterase activities in three indigenous wild birds (quail, collard dove and rock dove) in Mosul, Iraq, as determined by an electrometric method. The present findings are indicative of the sensi- tivity of the described method in detecting cholinesterase inhibition caused by organophosphates or carbamates. As these enzymes are potential targets for anticholinesterase insecticides, their activities could be routinely measured using the described electrometric method to assess Interdisciplinary Toxicology. 2011; Vol. 4(3): 144–148 Also available online on PubMed Central 147 exposure of wild birds to agricultural insecticides pollut- ing the environment. Acknowledgements This study was supported by a grant from the Ministry of Higher Education and Scientific Research, Iraq, No. 524, 2009. REFERENCES Abass KS and Mohammad FK. (2004). Validation of an electrometric method for cholinesterase measurement in the plasma and tissues of the chicken. Proceedings of the 11th Scientific Congress, Faculty of Veterinary Medicine, As- siut University, Assiut, Egypt 1: 241–259. Al-Badrany YMA and Mohammad, FK. (2007). Effects of acute and repeated oral exposure to the organophosphate insecticide chlorpyrifos on open- field activity in chicks. Toxicol Lett 174: 110–116. Alias AS and Mohammad FK. (2005). Electrometric measurement of plasma and tissue cholinesterase activities of four wild birds in Iraq. J Biol Res 4: 197–202. Anonymous (1986a) Organophosphorus Insecticides: A General Introduction, Environmental Health Criteria, No. 63. World Health Organization, Geneva, Switzerland. Anonymous (1986b) Carbamate Pesticides: A General Introduction Environmental Health Criteria, No. 64. World Health Organization, Geneva, Switzerland. Blakely BR and Yole MJ. (2002). Species differences in normal brain cholines- terase activities of animals and birds. Vet Hum Toxicol 44: 129–132. Burn JD and Leighton FA. (1996). Further studies of brain cholinesterase: Cholinergic receptor ratios in the diagnosis of acute lethal poisoning of birds by anticholinesterase pesticides. J Wildlife Dis 32: 216–224. Cairns MA, Maguire CC and Williams BA. (1991). Brain cholinesterase activ- ity of bobwhite acutely exposed to chlorpyrifos. Environ Toxicol Chem 10: 657–664. Claudie R, Grolleau G, Chamoulaud S and Riviere J. (2005). Plasma B-esterase activities in European raptors. J Wildlife Dis 41: 184–208. Clegg DJ and van Gemert M. (1999). Determination of the reference dose for chlorpyrifos: proceedings of an expert panel. J Toxicol Environ Health, Part B 2: 211–255. Cocker J, Mason HJ, Garfitt SJ and Jones K. (2002). Biological monitoring of exposure to organophosphate pesticides. Toxicol Lett 134: 97–103. Coggon D. (2002). Work with pesticides and organophosphate sheep dips. Occupational Medicine (London) 52: 467–470. Coles EH. (1986). Veterinary clinical pathology. Saunders Co., Philadelphia, PA, USA: 12–27. Fairbrother A and Bennett JK. (1988). The usefulness of cholinesterase mea- surements. J Wildlife Dis 24: 587–590. Fildes KJ, Szabo JK, Astheimer L, Hooper M and Buttemer WA. (2009). Plasma cholinesterase characteristics in native Australian birds: signif icance for monitoring avian species for pesticide exposure: 41–47. [cited 2011 May 27). Available from: http: //ro.uow.edu.au/scipapers/376. Fossi MC, Lari L and Casini S. (1996). Interspecies variation of ‘B’ esterases in birds: the influence of size and feeding habits. Arch Environ Contam Toxicol 31: 525–532. Fossi MC, Leonzio C, Massi A, Lari L and Casini S. (1992). Serum esterase in- hibition in birds: a nondestructive biomarker to assess organophosphorus and carbamate contamination. Arch Environ Contam Toxicol 23: 99–104. Hill EF and Murray HC. (1987). Seasonal variation in diagnostic enzymes and biochemical constituents of captive northern bobwhites and passerines. Comp Biochem Physiol 87B: 933–940. Hooper MJ. (1988). Avian cholinesterases: Their characterization and use in evaluating organophosphate insecticide exposure. Dissert Abst Int 6: 2068. Iko WM, Archuleta AS and Knop FL. (2003). Plasma cholinesterase levels of mountain plovers (CHARADRIUS MONTANUS) wintering in central Califor- nia, USA. Environ Toxicol Chem 22: 119–125. Copyright © 2011 Slovak Toxicology Society SETOX