A preliminary assessment of the palate and tongue for detecting organophosphorus and carbamate pesticide exposure in the degraded carcasses of vultures and other animals

Abstract

In many regions of the world, organophosphorus (OP) and carbamate (CM) pesticides are used to poison wildlife thought to be competing with human activities (e.g. hunting). Vultures may be secondarily poisoned or directly targeted, e.g. for muti or traditional medicine. Some OPs and CMs are so acutely toxic that animals will die with poisoned material still in their mouths -un-swallowed, before traces may have spread to other parts of the body. Even when death is more prolonged, the tissues in which residues have accumulated may deteriorate before the carcass is discovered, minimizing the chances of recovering viable samples for toxicological analyses that would conclusively identify poisoning as the cause of death. With all these factors in mind, we investigated the feasibility of detecting OP and CM pesticides in the oral cavity, with emphasis on the tongue and palate. A total of 60 degraded carcasses (n = 28 avian and 32 mammalian) recovered from various scenes of wildlife crime in Andalucía, southern Spain, where poisoning was suspected, Vulture News 68 July 2015 33 were submitted to the Center for Analysis and Diagnosis of Wildlife in Málaga for necropsy and toxicological analyses. Of these, 20 and 24 avian and mammalian tongues, respectively, could be recovered for analysis. Separately, the palate from one degraded Cinereous Vulture Aegypius monachus carcass was also opportunistically retrieved and analyzed following an incident of vulture mass-mortality in which nine Griffon Vultures Gyps fulvus also perished. Residues or presence of OPs and CMs were detected in one avian tongue (analyzed with food from the mouth) and four mammalian tongues. Our findings suggest avian tongues alone are not optimal, but canid tongues and those of larger mammals may lend themselves well to analysis. Detection of the OP chlorfenvinphos (3.39 mg/kg) in the Cinereous Vulture palate (the only part of the carcass in which residues were detected) indicates this is a promising sample. To our knowledge, this represents the first time that OP and CM pesticides have been detected in tongue and palate samples. We recommend further exploration of oral cavity samples, especially within the context of the risk that residues therein may pose to human health.

Talons and beaks are viable but underutilized samples for detecting organophosphorus and carbamate pesticide poisoning in raptors

“…When the carcasses of multiple species have been recovered, residues detected in either the beak or the talons of one carcass could compel a re-examination of others that had previously tested negative, especially if the latter was of a species accorded a higher protection status. Following a mass vulture poisoning in southern Spain in 2012, the detection of chlorfenvinphos residues in two Griffon Vultures prompted another examination of the carcass of a highly decomposed Cinereous Vulture that was also recovered from the scene (Richards et al 2015). The bird's palate was removed for analysis, and subsequent detection of chlorfenvinphos in this sample further strengthened the legal justification for pursuing the caseand ultimately served as a cornerstone of the secured conviction.…”

“…We note that TLC capacity is often a fixture even in the most minimally equipped laboratory, and therefore, in the absence of further confirmatory/quantitative analysis, a qualitative analysis could at least be conducted to establish presence/absence of a pesticide. (Richards et al 2014, Richards et al 2015. In Europe where a legal framework is being forged, and in Africa, where efforts are underway to strengthen legislation, regulatory mechanisms and investigatory/analytical capacity, failure to utilize these samples in the absence of other viable carcass components may result in pesticide residues -and deliberate poisoning incidents -being overlooked.…”

“…aldicarb) and OP (e.g. chlorfenvinphos) compounds in the palates and tongues of deliberately and/or unintentionally poisoned vultures, canids and domestic animals (Richards et al 2015). Vyas et al (2003) detected residues of the OP compound diazinon in (artificially exposed) gosling feet left outside for seven days.…”

“…Thus, the poor condition of the majority of the carcasses recovered during these investigation and submitted to CAD precludes analysis of AChE levels (Fajardo & Zorrilla 2016). Even when fresh carcasses are available, we caution that these compounds can be present in baits at such acutely toxic levels that birds die with the food still in their mouths, either unswallowed or regurgitated, before residues may reach other parts of the body (Richards et al 2014, Richards et al 2015, Fajardo & Zorrilla 2016.…”

“…Otieno et al (2010) detected residues of carbofuran and its primary metabolites in the talons and beaks of a desiccated African White-backed Vulture Gyps africanus carcass retrieved from an agricultural field in Kenya. In light of these findings, the opportunistic analysis of talons and heads/beaks was also initiated at CAD (Zoun & Spierenburg 1989, Richards et al 2015. Table 1 and 2 summarize the OP and CM compounds (and/or their main breakdown products) that have been detected in the talons and beaks, respectively, of various avian species submitted to the CAD as part of routine wildlife forensics investigations in southern Spain between 2012 and 2016.…”