Electrometric measurement of plasma and tissue cholinesterase activities of four wild birds in Iraq

Measurement of serum or plasma and brain cholinesterase (ChE) activities in wild birds is used to diagnose and monitor their exposure to organophosphate and carbamate insecticides (Marden et al., 1994; Burn & Leighton, 1996; Iko et al., 2002; Osten et al., 2005). Reduced enzyme activity is an indicator of exposure and adverse effects of anti ChE insecticides even in the absence of overt signs of toxicosis or lethality (Wilson & Henderson, 1992; Wilson, 1998, 1999). These insecticides inhibit acetylcholinesterase activity in the nervous tissue causing accumulation of acetylcholine at the nerve endings with subsequent appearance of signs of toxicosis characterized by muscarinic, nicotinic and central nervous system effects (Osweiler, 1996; Wilson, 1998). The extent of ChE inhibition and the appearance of signs of toxicosis depend on many factors such as the type of the ChE inhibiting compound, amounts exposed to, duration, frequency and route of exposure and species variation (Osweiler, 1996; Wilson, 1998, 1999; Wilson et al., 1998). Various colorimetric and electrometric methods are available for measurement of blood and tissue ChE activities (Fairbrother et al., 1991; Wilson, 1999). Electrometric methods are widely used in veterinary practice because of their simplicity, accuracy and they do not require sophisticated equipment and laboratory supplies (Mohammad & St. Omer, 1982; Osweiler et al., 1985; Imerman, 1993). Recently, a modified electrometric ChE method has been validated and used in several animal species (Mohammad et al., 1997, 2002; Al-Jobory & Mohammad, 2004; Ahmed & Mohammad, 2005) as well as in the chicken (Faris et al., 1999; Abass & MoJournal of Biological Research 4: 197 – 202, 2005