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In This Article

  • Summary
  • Abstract
  • Introduction
  • Protocol
  • Representative Results
  • Discussion
  • Acknowledgements
  • Materials
  • References
  • Reprints and Permissions

Summary

Here, we present a protocol to evaluate nociception in mice infected with Trypanosoma evansi, using the electronic von Frey apparatus as a tool, measuring mechanical thresholds of the hind paw and viscera.

Abstract

Infectious disease pathogenesis is still a complex field to study. The course of several clinical signs, such as allodynia and pain, may be observed in domestic animals. However, the knowledge of their pathways and correct treatment need controlled experiments, many of them using laboratory animals. Measuring changes in mechanical thresholds of the hind paw and viscera is a useful technique to observe changes in pain perception in rodents. Withdrawal response can be measured first in baseline tests, which creates better control of experimental groups. Subsequent tests can be performed after inducing infection and adding drugs to the protocol. The use of an electronic von Frey apparatus associated with the use of a facial scale to observe pain-like changes allows a simple, precise, and consistent assessment to evaluate allodynia and pain in mice. Thus, experiments using the present methodology for Trypanosoma evansi infection represent a useful method to evaluate allodynia and pain in laboratory-infected animals, which can be applied to the conventional treatment for livestock animals.

Introduction

Trypanosoma evansi is the etiological agent of the disease called "surra" or "mal-das-cadeiras" in South America1,2. It commonly affects equines and cattle, but also wild fauna, being transmitted by hematophagous bats, tabanids, and stomoxes fly bites1,3. Surra is a major disease in domestic animals, which can be fatal in the absence of the correct treatment, exhibiting nonspecific clinical signs such as anemia, loss of appetite and weight, muscle weakness, and abortion, which may vary according to the host and geographic regio....

Protocol

All experiments were performed using 10-week-old adult female Swiss mice (35-55 g). Animals were housed in polysulfone cages (3-5 animals per cage) in a room with controlled temperature (21 ± 1 °C), 12 h light/12 h dark cycle, and standard lab chow and water ad libitum. Ten animals were assigned to each group in every test to demonstrate the consistent effects of drug treatments. The experimental design was submitted and approved by the Ethics Committee of Santa Catarina State University (CEUA) (protoc.......

Representative Results

Decrease in the mechanical threshold due to T. evansi infection as evaluated by electronic von Frey apparatus on both right hind paw and visceral tissues
The experiment was conducted over 5 days, according to previous data related to the available T. evansi sample2. Infected mice started to show a significant difference in mechanical threshold on the right hind paw at day 3 post infection and remained significantly lower than the control group during the ne.......

Discussion

A critical step in experiments involving infected animals is the control of parasitemia levels. Different strains of T. evansi may behave in divergent ways in mice, leading from acute to chronic infections2,4,5,6. Furthermore, changes in the infection dose may decrease or extend the survival time of mice. Therefore, obtaining a survival curve prior to the experiments is recommended to .......

Acknowledgements

The authors give special thanks to the Santa Catarina State University for financial support, to the Pharmacology Laboratory for the animals and space, and to the Hemoparasites and Vectors Biochemistry Laboratory for the cryopreserved blood sample infected with T. evansi used in these experiments.

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Materials

NameCompanyCatalog NumberComments
26 G 1/2" needle coupled to insulin syringeTKL80288090100Used to infund solutions on laboratory animals
Accessories for von Frey analgesimeterINSIGHTEFF 303Containment box with support for digital analgesimeter assessment
D-(+)-GlucoseSIGMA-ALDRICHG7021A monosaccharide which is the main source of energy in the form of ATP for living organisms
Digital analgesimeterINSIGHTvon Frey Wi-FiThe von Frey Wi-Fi is a portable device used to assess tissue sensitivity to mechanical stimuli
Gilson type 10 µL polypropylene tipCRALPLAST18261Polypropylene to be used on eletronic von Frey apparatus, recommended for hind paw allodynia assessment
Laboratory water bathBEING INSTRUMENTBW-22PUsed to heat liquid and semi-solid substances contained in appropriate recipients to specific temperature
Phosphate buffered salineSIGMA-ALDRICH806552A balanced salt solution buffer used for a variety of cell culture applications
Swiss mice (Mus musculus) from both genderUFSCSwiss WebsterLaboratory animals used for controlled experiments
Trypanosoma evansi cryiopreserved sampleUDESC-Sample used to infect all mice, ceded by the Hemoparasites and Vectors Biochemistry Laboratory
Universal type 10 µL polypropylene tipCRALPLAST18171Polypropylene to be used on eletronic von Frey apparatus, recommended for visceral allodynia assessment

References

  1. Desquesnes, M., et al. Trypanosoma evansi and surra: a review and perspectives on origin, history, distribution, taxonomy, morphology, hosts, and pathogenic effects. BioMed Research International. 2013, 194176 (2013).
  2. Cipriani, D. S., et al.

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Trypanosoma EvansiNociceptionAllodyniaPain AssessmentLaboratory AnimalsElectronic Von FreyFacial ScaleExperimental ChallengesAnimal WelfareAnalgesicsInfection ModelPain PerceptionWithdrawal ResponseMechanical ThresholdsInfectious Disease Pathogenesis

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