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Veterinary research communications2007; 32(1); 75-92; doi: 10.1007/s11259-007-9004-z

Effects of oral tetrachlorvinphos fly control (Equitrol) administration in horses: physiological and behavioural findings.

Abstract: Highly reactive horses may pose risks to humans involved in equestrian activities. Among the factors that may affect horses' reactivity to external stimuli are pesticides used for fly control in equine facilities. The organophosphorus (OP) insecticide tetrachlorvinphos (TCVP) is used as a feed-through larvicide to prevent completion of the fly larval life cycle in horse manure. TCVP exerts its effect by inhibiting the enzyme cholinesterase (ChE) leading to the accumulation of the neurotransmitter acetylcholine (AChE) in synapses of the central and peripheral nervous systems. The aim of the present study was to investigate alterations of whole-blood ChE levels associated with feeding a commercially available product (Equitrol, Farnam Companies, Inc.) to horses for fly control. A second aim was to report neurological, physiological and behavioural findings in addition to profiles of selected immune markers (IFN-gamma, IL-12p40 and COX-2) and serum thyroid hormones during and after a 30-day treatment period of TCVP feeding. The results indicated significant decreases in whole-blood ChE activity and concomitant behavioural alterations, manifested as increased reactivity and decreased controllability in treated horses. No changes were detected in physiological or neurological parameters, immune markers or thyroid hormones in treated (n=6) or control (n=4) horses during the course of the study.
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Publication Date: 2007-05-24 PubMed ID: 17522960DOI: 10.1007/s11259-007-9004-zGoogle Scholar: Lookup
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  • Controlled Clinical Trial
  • Journal Article
  • Research Support
  • Non-U.S. Gov't

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research study investigates the physiological and behavioural impact on horses as a result of oral administration of a common fly control pesticide. Specifically, the study looks at how a product called tetrachlorvinphos (TCVP) can cause behavioural changes in horses, including increased reactivity and lesser controllability.

Study Objective and Methodology

The study aimed to understand the alterations in horses’ whole-blood Cholinesterase (ChE) levels when fed with a commercially available product (Equitrol) for fly control. The researchers also intended to analyze any changes in selected immune markers, serum thyroid hormones, and neurological and physiological parameters throughout a 30-day treatment period of TCVP feeding.

  • To achieve the goal, the researchers treated a group of horses (n=6) with Equitrol and compared their behavior and physiological responses with a control group (n=4).
  • The equine reactivity was carefully monitored and measured, and the whole-blood levels of ChE were regularly analyzed.

Key Findings

On analyzing the data gathered during the experiment, the study found a direct correlation between TCVP ingestion and behavioural changes in horses.

  • There was a significant decrease in the whole-blood ChE activity in horses treated with TCVP. Low ChE activity is associated with an accumulation of the neurotransmitter acetylcholine (AChE), which might result in heightened sensitivity or reactivity of horses towards their environment.
  • This decrease in ChE activity led to behavioural alterations, specifically presenting as increased reactivity and decreased controllability in the test group.
  • On the other hand, no changes were found in the physiological or neurological parameters of treated horses.
  • Similarly, when the immune markers were evaluated, no variations were found in serum thyroid hormones or selected immune markers including IFN-gamma, IL-12p40 and COX-2.

Implication of Findings

Though the experiment does not point to any physiological or neurological changes, it’s apparent that TCVP has a significant impact on the behavior of horses, which can be a challenging discovery for those engaging with horses in various activities. The heightened reactivity can result in unpredictability, making these horses a potential risk. The findings of this study suggest a need for the review and careful consideration of TCVP usage as a means of fly control in horses.

Cite This Article

APA
Berger J, Valdez S, Puschner B, Leutenegger CM, Gardner IA, Madigan JE. (2007). Effects of oral tetrachlorvinphos fly control (Equitrol) administration in horses: physiological and behavioural findings. Vet Res Commun, 32(1), 75-92. https://doi.org/10.1007/s11259-007-9004-z

Publication

Veterinary research communications
ISSN: 0165-7380
NlmUniqueID: 8100520
Country: Switzerland
Language: English
Volume: 32
Issue: 1
Pages: 75-92

Researcher Affiliations

Berger, J
  • Behaviour Service, Veterinary Medical Teaching Hospital, University of California, Davis, California 95616, USA. jberger@ucdavis.edu
Valdez, S
    Puschner, B
      Leutenegger, C M
        Gardner, I A
          Madigan, J E

            MeSH Terms

            • Animals
            • Behavior, Animal / drug effects
            • Cholinesterase Inhibitors / administration & dosage
            • Cholinesterase Inhibitors / pharmacology
            • Cholinesterases / blood
            • Diptera
            • Drug Administration Schedule
            • Horses
            • Insect Control / methods
            • Insecticides / administration & dosage
            • Insecticides / chemistry
            • Insecticides / pharmacology
            • Tetrachlorvinphos / administration & dosage
            • Tetrachlorvinphos / chemistry
            • Tetrachlorvinphos / pharmacology

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